National Ocean Service

National Ocean Service (NOS) Technical

Memos

The National Oceanic and Atmospheric Administration Year 

An ecological characterization of the Salt

River Bay National Historical Park and

Ecological Preserve

Matthew S. Kendall L.T. Takata O. Jensen

NOS, matt.kendall@noaa.gov

Z, Hills-Starr Mark E. Monaco

NOS, mark.monaco@noaa.gov

This paper is posted at Repository@NOAA.

http://repository.wrclib.noaa.gov/nos tech memos/1
An Ecological Characterization of the 

Salt River Bay National Historical Park and 

Ecological Preserve, U.S. Virgin Islands

NOAA Technical Memorandum NOS NCCOS 14
Citation For This Report

Kendall, M.S., L.T. Takata, O. Jensen, Z. Hillis-Starr, and M.E. Monaco. 2005. An 

Ecological Characterization of Salt River Bay National Historical Park and 

Ecological Preserve, U.S. Virgin Islands. NOAA Technical Memorandum NOS 

NCCOS 14, 116 pp.

Cover Photograph

NOAA aerial photograph of Salt River Bay taken in 2000.

Mention of trade names or commercial products does not constitute endorsement or 

recommendation for their use by the United States government.
An Ecological Characterization of the Salt 

River Bay National Historical Park and 

Ecological Preserve, U.S. Virgin Islands

M.S. Kendall1, L.T. Takata1, O. Jensen1, Z. Hillis-Starr2, and M.E. Monaco1

1

NOAA, National Ocean Service

National Centers for Coastal Ocean Science

Center for Coastal Monitoring and Assessment

1305 East West Highway, N/SCI-1

Silver Spring, MD 20910

Matt.Kendall@noaa.gov

2

National Park Service, Buck Island Reef National Monument

2100 Church Street #100

Christiansted, St. Croix, VI 00820-4611

Zandy_Hillis-Starr@nps.gov

Contributors: 

Government of the Virgin Islands Department of Planning and Natural Resources (VIDPNR) 

VIDPNR Coastal Zone Management Division

VIDPNR Division of Fish and Wildlife 

VIDPNR Division of Environmental Protection

NOAA, Office of Oceanic and Atmospheric Research

NOAA, National Environmental Satellite, Data and Information Service

St. Croix Environmental Association, Virgin Islands ReLeaf

NOAA Technical Memorandum NOS NCCOS 14

April 2005

United States Department of Commerce

Carlos M. Gutierrez

Secretary

National Oceanic and 

Atmospheric Administration

Conrad C. Lautenbacher, Jr.

Administrator

National Ocean Service

Richard W. Spinrad

Assistant Administrator
4
5

 Salt River Bay National Historical Park 

and Ecological Preserve (hereafter, SARI or the 

park) was created in 1992 to preserve, protect, 

and interpret nationally significant natural, 

historical, and cultural resources (United States 

Congress 1992). The diverse ecosystem within 

it includes a large mangrove forest, a submarine 

canyon, coral reefs, seagrass beds, coastal 

forests, and many other natural and developed 

landscape elements. These ecosystem 

components are, in turn, utilized by a great 

diversity of flora and fauna. A comprehensive 

spatial inventory of these ecosystems is required 

for successful management. To meet this 

need, the National Oceanic and Atmospheric 

Administration (NOAA) Biogeography Program, 

in consultation with the National Park Service 

(NPS) and the Government of the Virgin 

Islands Department of Planning and Natural 

Resources (VIDPNR), conducted an ecological 

characterization. The characterization consists 

of three complementary components: a text 

report, digital habitat maps, and a collection of 

historical aerial photographs. This ecological 

characterization provides managers with a suite 

of tools that, when coupled with the excellent 

pre-existing body of work on SARI resources, 

enables improved research and monitoring 

activities within the park (see Appendix F for a 

list of data products). 

A collection 184 color, black and white, 

black and white infrared, and color infrared 

aerial photographs of the Salt River area 

from the 1970’s to 2000 were obtained from 

several federal agencies for this assessment. 

Photographs from selected years were digitally 

oriented in geographic space (orthorectified) 

and then used to create several habitat maps of 

the park. The most current photographs, from 

year 2000, were used to create a map of fifty 

terrestrial and marine habitat types visible in the 

imagery. This map covers the entire land (145 

hectares) and mangrove area (19 hectares) 

within the park, all of the benthic habitat within 

Triton, Sugar, and Salt River Bays, and much 

of the offshore benthic habitats (250 hectares). 

This map, created with a minimum feature size 

of 10 by 10 meters, is the first detailed spatial 

characterization of the SARI ecosystem. The 

time series of photographs were used to create 

maps of changes to seagrass and mangrove 

distributions that have occurred over the last 

three decades. This group of maps and images 

were used to frame the discussion of each major 

habitat type, faunal group, or environmental 

category in the text report for this ecological 

characterization.

 The text portion of the report is divided 

into sections based on physical characteristics 

(e.g. geology, water quality, currents), habitat 

types (e.g. land cover, coral reefs, mangroves), 

and major faunal groups (e.g. fish, birds). 

Each section includes an overview, methods, 

results, and a discussion of linkages with 

other components of the SARI ecosystem and 

surrounding environment. 

 Physical characteristics of the SARI 

area described in this report include currents, 

climate, water quality, geology, and bathymetry. 

Water currents within the park are primarily wind 

and tidal driven. These play an important role 

in the transport of sediments along the shelf 

and canyon axis and consequently are a major 

control on reef characteristics of the canyon 

walls. The climate of the park is controlled 

primarily by the seasonal changes associated 

with the trade winds which are interrupted by 

weak cold fronts in winter and hurricanes in the 

summer and fall. Water quality within the bays 

is usually within acceptable values for Class B 

waters although dissolved oxygen, turbidity, and 

bacterial load of some sites farthest from the bay 

mouth are periodically in violation of allowable 

pollutant levels. The geology of the region has 

been well characterized including the underlying 

terrestrial and marine formations as well as 

the sediment accretion, erosion, and transport 

patterns of the bays and shelf. Bathymetry 

within the park has changed considerably over 

the last fifty years due to dredging activities and 

will likely continue to change at an accelerated 

rate relative to natural conditions due to 

development and erosion in the watershed. 

 Reef and hard bottom habitats in the 

canyon were once among the best studied 

and characterized coral structures in the world 

at the time the NOAA National Undersea 

Research Program (NURP) saturation diving 

Executive Summary
Executive Summary

facility was in operation at the site. Since the 

closing of this facility this is no longer the case. 

Reefs within SARI but outside of the canyon 

have received virtually no attention. Based 

on the year 2000 maps, total two-dimensional 

coral reef and hard bottom area within SARI 

covered 116.3 hectares, with over 41 species of 

coral documented in the canyon from existing 

literature.

Seagrass and algae communities within 

the canyon were also once studied intensively 

using the NOAA/NURP diving facility but have 

since gone largely unmonitored. Our maps 

indicate that seagrass distributions within 

the bays declined by ~13% overall from the 

1970’s to 1992 with the greatest apparent 

change occurring in the northwestern portion 

of Salt River Bay. By 2000, seagrass area had 

changed little from its 1992 extent.

The mangrove forests of the park were 

once among the most impressive in the region 

although they have undergone perhaps the 

most dramatic changes of any SARI ecosystem 

component in the last 30 years. Hurricane Hugo 

in 1989 killed over half of the 1988 mangrove 

stand, approximately 12 hectares of forest, and 

reduced the density of much of the remaining 

canopy. Despite this catastrophic loss, forests 

are recovering both naturally and with human 

assistance. 

Notable evidence of past and recent 

human alteration, including dredging and 

construction, are noted in the grey literature, and 

are also visible in aerial photographs. Despite 

this and the expansive residentially zoned 

development areas within the park, forests 

dominate current (2000) terrestrial land cover, 

accounting for 106 hectares. 

Fish communities within SARI are quite 

diverse considering the park’s relatively small 

area. The presence of mangrove, seagrass, 

reef, bay, shelf edge, and access to offshore 

habitat within park boundaries all contribute to 

the high diversity of fish. Recent studies have 

noted 57 species in mangrove habitats, and 

nearly 200 on the walls of the canyon.

The bird fauna utilizing SARI are similarly 

diverse. The SARI area contains an array 

of potential avifauna habitat, including sandy 

beaches, mangrove stands, and mud flats. The 

most recent bird census data were collected by 

the Virgin Islands Division of Fish and Wildlife, 

but were not available during the preparation of 

this report.

The aerial imagery, habitat maps, and 

text report that make up this assessment are 

complimentary, together providing research, 

monitoring, and management tools for the park. 

The images can be used to map additional 

ground features, document historical changes, 

and serve as a baseline against which future 

imagery may be compared. Habitat and 

land cover maps will assist with the design of 

monitoring schemes, selection of research sites, 

and identification of potential habitat for species 

of interest. The discussion and analyses 

contained in the text highlight established 

knowledge, explore spatial aspects of prior 

research, and identify information gaps and 

threats that may guide future monitoring and 

research. Together, these components provide 

a variety of information that will facilitate the 

current and future stewardship of the diverse 

resources contained within SARI. 

6

Executive Summary
Section Chapter

 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

 2 Aerial Photographs and Mapping Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

 3 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

 4 Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

 5 Bathymetry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

 6 Currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

 7 Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

 8 Reefs and Hardbottom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

 9 Seagrass and Algae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52

 10 Mangroves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60

 11 Fish. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68

 12 Birds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72

 13 Land Cover, Soils, and Land Use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76

 14 Data Gaps and Threats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84

 15 Additional Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86

 Appendices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88

 Appendix A: Hydrolab/Aquarius Bibliography . . . . . . . . . . . . . . . . . . . . . . .89

 Appendix B: Coral Species List for Salt River Canyon . . . . . . . . . . . . . . . . .96

 Appendix C: Plant Species List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98

 Appendix D: Fish Species List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102

 Appendix E: Ground Truth Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108

 Appendix F: Data Products List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114

 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115

An Ecological Characterization of the 

Salt River Bay National Historical Park 

and Ecological Preserve, 

U.S. Virgin Islands

Table of Contents
8

Section 1 Introduction

Figure 1.1. Features, sampling sites, and place names in and around SARI. Capital letters denote water quality 

sampling atations.

64°46'0"W

64°46'0"W

64°45'30"W

64°45'30"W

64°45'0"W

64°45'0"W

17°45'30"N

17°45'30"N

17°46'0"N

17°46'0"N

17°46'30"N

17°46'30"N

17°47'0"N

17°47'0"N

17°47'30"N

17°47'30"N

0 500 Meters

Locator Map

East

Cove Dredged

Basin

Abandoned

Triton Marina Cut

Bay

Estate

Judith's Fancy

!(

Former

NOAA/FDU

Dock

Estate

Montpelier

Estate

Morningstar

Sugar

Bay

Salt River Bay Salt River

Marina

!(

Columbus

Landing

Estate

Salt River

Salt River Gut

and

swamp

East Wall

West Wall

Salt River Canyon

Emergent Barrier Reefs

Channel

White Horse

Reef

!(

Former Site of NOAA

Undersea Habitats

SARI Boundary

A

B

C

D

E

F

G

H

I

J

!(

NOAA/CREWS Station

central

peninsula
9

Section 1 Introduction

This report, associated maps, and 

aerial photographs provide an ecological 

characterization of the Salt River Bay National 

Historical Park and Ecological Preserve 

(hereafter, “SARI” or “the park”). It is the result 

of a partnership between the National Park 

Service (NPS) and the National Oceanic and 

Atmospheric Administration (NOAA) to provide 

a baseline characterization to enhance resource 

management of the park. The park is located 

along the north/central coast of St. Croix, 

United States Virgin Islands. Created in 1992, 

SARI was established to preserve, protect, 

and interpret nationally significant natural, 

historical, and cultural resources for the benefit 

of present and future generations (United States 

Congress 1992). The park’s roughly 1015 acres 

encompass a combination of marine, estuarine, 

and terrestrial habitats including the largest 

remaining mangrove forest within the U.S. 

Virgin Islands, coral reefs, seagrass beds, and a 

submarine canyon.

 Several excellent assessments of 

the cultural and ecological resources of the 

park have been conducted, most notably 

before and after the designation of park 

boundaries (National Park Service 1990; 

Island Resources Foundation 1993a, Island 

Resources Foundation 1993b), and for marina/

hotel development proposals within smaller 

areas of SARI (Antillean Engineers Inc. 1983, 

Sugar Bay Land Development Ltd. 1986, 

Coastal Consultants 1987). These reports 

were typically compilations of prior research 

coupled with targeted collection of new data 

such as current surveys to document flushing 

potential for proposed marinas. Topics not 

addressed in the present assessment that 

have been described in detail elsewhere 

include the park's historical significance, land 

ownership and zoning, resource use and 

conflicts, and recommendations to preserve the 

park's ecosystems and cultural resources (e.g. 

National Park Service 1990; Island Resources 

Foundation 1993a, Island Resources Foundation 

1993b). For example, the Area of Particular 

Concern reports on the Salt River watershed 

include a comprehensive list of management 

recommendations for preserving the ecological 

value of the site (Island Resources Foundation 

1993a, Island Resources Foundation 1993b). 

Several studies have compiled qualitative 

species lists for terrestrial and marine flora 

and fauna of SARI (e.g. Gerhard and Bowman 

1975, National Park Service 1990). Rather than 

repeat this information here, species lists were 

only included in the present assessment when 

either new data are available or a novel format 

and comparison are presented. For the most up 

to date information on the federally threatened 

or endangered species in the park, the US Fish 

and Wildlife Service should be consulted. In 

addition, the VI DPNR Division of Fish and 

Wildlife should be consulted for a current list of 

locally threatened or endangered species and 

associated monitoring activities. 

Despite a diversity of prior assessments, 

a fine-scale, spatially explicit characterization 

of the park’s ecological resources has not been 

conducted. Such an accounting of the spatial 

distribution of SARI’s marine, estuarine, and 

terrestrial habitats is an important missing 

component of the park’s ecological management 

plans. 

 The objective of this assessment is to 

provide the needed, spatially explicit inventory of 

Figure 1.2. Aerial photograph of Salt River Bay, 

taken during 2000.

Section 1 Introduction
10

park resources and discuss what is known about 

the park’s ecology within this spatial framework. 

The present assessment is not intended to 

replace the previously completed assessments 

of the park (e.g. Island Resources Foundation 

1993b), rather it is designed to build on and 

enhance the value of the information within 

them by providing habitat maps and related 

discussion regarding the spatial distribution of 

ecological resources. 

 There are three components to the 

present assessment: a text report, a time 

series of habitat maps, and data products such 

as aerial photographs and digital map files 

(see Appendix F). Since the 1940’s, aerial 

photographs of St. Croix have been obtained 

periodically by Government agencies. Although 

photographs rarely targeted SARI directly, 

many such photography acquisitions include 

portions of the park. These images provide a 

unique record and time series of changes in 

land cover and benthic features within SARI 

from the 1940’s, 1970’s, shortly before and after 

Hurricane Hugo (1989), up to conditions in 2000. 

A collection of available hard copy and digital 

scans of these images are included as a part 

of this assessment. Unfortunately, the oldest 

images, acquired by the US Navy in 1947, were 

not made available at the time this report and 

data were compiled.

Aerial photographs were the basis of the 

second and perhaps most useful component 

of this ecological assessment; maps of land, 

estuarine, and benthic cover. The long time 

series of high quality photographs allowed maps 

to be created based on 1970’s, 1988, 1992, 

and 2000 orthorectified images. Seagrass and 

mangrove coverage were mapped for all four 

years of imagery. Maps based on the most 

current imagery (2000) include these habitats 

as well as coral reef and hard bottom, sand 

and mud bottom, forest, development, and 

other land and marine cover types for a total 

of 50 map categories. These maps, valuable 

aids to management by themselves, frame the 

discussion of SARI’s ecological resources in the 

report component of this characterization.

 The report provides descriptions 

and interpretations of the image and map 

products in the context of previously completed 

environmental assessments and original 

research findings. A tremendous amount of 

research has been conducted within SARI, 

primarily within the submarine canyon due to 

the presence of the NOAA/NURP saturation 

diving facility, Hydrolab/Aquarius, from 1977 

to 1989 (See Locator Map, figure 1.1) which 

was operated in conjunction with the West 

Indies Lab, Fairleigh Dickinson University. 

Only those studies most relevant for the 

ecological characterization were used. A more 

comprehensive list of research related to SARI 

is available from NOAA through the Coral 

Literature Education and Outreach program 

(Appendix A). 

The present report is divided into 

sections based on major faunal groups (e.g. 

fish, birds), habitat types (e.g. land cover, 

coral reefs, mangroves), and environmental 

characteristics (e.g. geology, water quality, 

currents). Each section includes an overview, 

methods, results, and a discussion of linkages 

with other components of the SARI ecosystem 

and surrounding environment. All hard copy 

and electronic components of this ecological 

characterization are available from the National 

Park Service, Division of Resource Management 

in Christiansted, St. Croix, U.S. Virgin Islands.

REFERENCES

Antillean Engineers Inc. 1983. Environmental 

Assessment Report for the Proposed 

Docking Facility at Salt River Marina, 

Estate Salt River, Sugar Bay, St. Croix, 

United States Virgin Islands. For Lica 

Corporation. Christiansted, St. Croix. Pp. 

1-111 and Appendices

Coastal Consultants. 1987. Environmental 

Assessment Report for Columbus 

Landing: A Marina, Restaurant, 

Shopping and Office Complex, at Estate 

Morningstar on Sugar Bay (Salt River) 

St. Croix, U.S. Virgin Islands. For Haines 

Enterprises Inc. Kingshill, St. Croix. Pp. 

1-64 and Appendices

Section 1 Introduction
11

Section 1 Introduction

Island Resources Foundation. 1993. Salt River 

Bay Area of Particular Concern and Area 

of Preservation and Restoration: Draft 

Management Plan. June 1993. Pp. 1-50 

and Figures

Island Resources Foundation. 1993b. Salt River 

Bay and Watershed Area of Particular 

Concern and Area of Preservation and 

Restoration: A Comprehensive Analytic 

Study. September 1993. Pp. 1-60 and 

Figures

National Park Service. 1990. Alternatives 

study and environmental assessment: 

Columbus landing site, St. Croix, U.S. 

Virgin Islands. Division of Planning 

Design and Compliance, Southeast 

Region, National Park Service. Atlanta, 

GA. Pp. 1-129 and Appendices

Sugar Bay Land Development Ltd. 1986. 

Environmental Assessment Report: 

Virgin Grand Beach Resort. For 

Government of the Virgin Islands. 

Dayton, OH. 

United States Congress. 1992. Salt River Bay 

National Historical Park and Ecological 

Preserve at St. Croix, Virgin Islands, 

Act of 1992. Public Law 102-247, 102d 

Congress, February 24, 1992.
12

Section 2 Aerial Photographs & Mapping Methods

64°46'0"W

64°46'0"W

64°45'30"W

64°45'30"W

64°45'0"W

64°45'0"W

64°44'30"W

64°44'30"W

17°45'30"N

17°45'30"N

17°46'0"N

17°46'0"N

17°46'30"N

17°46'30"N

17°47'0"N

17°47'0"N

17°47'30"N

17°47'30"N

0 500 Meters

All

Mapping

Categories

2000

Figure 2.1. Map of all benthic, mangrove, and land cover map classifications in SARI based on 2000 aerial 

photograph.
13

Section 2 Aerial Photographs & Mapping Methods

Park Boundary

Classification

Benthic, Artificial

Coral Reef and Colonized Hardbottom,

Aggregated Patch Reefs

Coral Reef and Colonized Hardbottom,

Colonized Bedrock

Coral Reef and Colonized Hardbottom,

Colonized Pavement

Coral Reef and Colonized Hardbottom,

Colonized Pavement with Sand Channels

Coral Reef and Colonized Hardbottom,

Linear Reef

Coral Reef and Colonized Hardbottom,

Scattered Coral/Rock in Unconsolidated Sediment

Coral Reef and Colonized Hardbottom,

Spur and Groove

Uncolonized Hardbottom,

Reef Rubble

Uncolonized Hardbottom,

Uncolonized Bedrock

Uncolonized Hardbottom,

Uncolonized Pavement

Macroalgae,

Continuous - 90% to 100% cover

Macroalgae, Patchy (Discontinuous) -

10% to less than 50% cover

Macroalgae, Patchy (Discontinuous) -

50% to less than 90% cover

Seagrass, Continuous -

90% to 100% cover

Seagrass, Patchy (Discontinuous) -

10% to less than 50% cover

Seagrass, Patchy (Discontinuous) -

50% to less than 90% cover

Benthic,

Unconsolidated Sediments, Mud

Benthic,

Unconsolidated Sediments, Sand

Benthic, Unknown

Land, Bare Areas,

Other

Land, Bare Areas,

Rock

Land, Bare Areas,

Sand/Beach

Land, Bare Areas,

Soil

Developed, Commercial

Developed, Residential

Inland Water Bodies,

Freshwater Pond

Inland Water Bodies,

Saltwater Pond

Forest/Trees, Closed -

>65% canopy coverage

Forest/Trees, Open -

15%-65% canopy coverage

Forest/Trees, Sparse -

1%-15% canopy coverage

Shrubs/Bushes, Closed - 

>65% canopy coverage

Shrubs/Bushes, Open - 

15%-65% canopy coverage

Shrubs/Bushes, Sparse - 

1%-15% canopy coverage

Vegetated Field

Roads, Paved

Roads, Unpaved

Mangrove, Avicennia germanis,

Closed - >65% canopy cover

Mangrove, Avicennia germanis,

Open - 15%-65% canopy coverage

Mangrove, Avicennia germanis,

Sparse - 1%-15% canopy coverage

Mangrove, Dead

Mangrove, Laguncularia racemosa,

Closed - >65% canopy cover

Mangrove, Laguncularia racemosa,

Open - 15%-65% canopy coverage

Mangrove, Laguncularia racemosa,

Sparse - 1%-15% canopy coverage

Mangrove, Mixed,

Closed - >65% canopy cover

Mangrove, Mixed,

Open - 15%-65% canopy coverage

Mangrove, Mixed,

Sparse - 1%-15% canopy coverage

Mangrove, Rhizophora mangle,

Closed - >65% canopy cover

Mangrove, Rhizophora mangle,

Open - 15%-65% canopy coverage

Mangrove, Rhizophora mangle,

Sparse - 1%-15% canopy coverage

Figure 2.1. (Cont.) Legend for map of all benthic, mangrove, and land cover map classifications in SARI.
14

OVERVIEW

Benthic habitat, mangrove, and land 

cover maps were created to provide the park 

with a spatial inventory of its resources, and to 

enable an examination of changes in seagrass 

and mangrove distribution through time. A total 

of 184 aerial photographs were obtained of the 

Salt River study area. Maps were created from 

a subset of aerial photographs acquired from the 

1970’s through 2000. The most recent map 

provides a thorough inventory of park resources, 

covering 50 benthic, mangrove, and land 

cover classifications within SARI boundaries 

during 2000. That year, 2.50 km2

 of benthic 

habitat area, 1.45 km2 of land cover area, and 

approximately 0.19 km2 of mangrove area were 

mapped. During the 1970’s, 1988, and 1992, 

only the 3 seagrass and 13 mangrove classes 

were mapped to examine distribution changes in 

those habitats beginning with the oldest year of 

imagery available, before and after the passage 

of Hurricane Hugo in 1989 up to conditions 

in 2000. Seagrass and mangrove coverage 

shifted notably in size and shape before and 

after the passage of the hurricane. In 2000, 

forest cover dominated terrestrial areas, and 

coral reef and colonized hard bottom dominated 

in benthic areas. These maps, as well as the 

orthorectified photo mosaics generated for them, 

will facilitate present inventory and monitoring 

efforts for the park, and can be utilized to direct 

future studies.

METHODS

A search was conducted to locate and 

obtain all aerial photographs of the study region. 

Several agencies were contacted through 

email or telephone, including the Federal 

Emergency Management Agency (FEMA), 

the U.S. Geological Survey (USGS), the U.S. 

Department of Agriculture (USDA), NOAA’s 

National Geodetic Survey (NGS), and the U.S. 

Army Corps of Engineers (USACE). Local (St. 

Croix) contacts included the University of the 

Virgin Islands, the Island Resources Foundation, 

the Conservation Data Center, and the St. 

Croix Environmental Association. A complete 

set of these images is available at the National 

Park Service Office on St. Croix (see pg. 84 for 

contact information).

 A subset of images taken by the 

National Geodetic Survey (NGS) were selected 

to construct georeferenced photographic 

mosaicks (images tiled together to form a single 

image), from which all habitat and land cover 

maps were constructed. Year 2000 images, 

the most recent available, were used to produce 

an inventory of the land and benthic features 

within the park. In order to examine changes 

in seagrass and mangrove habitats through 

time, both the oldest and most recent imagery 

available was used. In addition, due to the 

major impacts of Hurricane Hugo in 1989, the 

closest available images to before and after the 

storm’s passage were also used. Photographs 

selected were from 1988, 1992, and 2000. The 

oldest available photographs taken in 1971 

and 1977, did not cover the full extent of the 

study region during any single year. Therefore, 

a composite “1970s” mosaic covering the 

desired spatial extent for this assessment was 

constructed from a combination of both years of 

Section 2 Aerial Photographs & Mapping Methods

Figure 2.2. Taking GPS data to orthorectify aerial 

photographs.

Section 2 Aerial Photographs & Mapping Methods
15

photography (See Table 2.1. for information on 

the photographs used to produce each mosaic).

 To produce mosaics, scans of selected 

photographs were “orthorectified” or linked to 

coordinates in geographic space. Geomatica 

OrthoEngine version 9.1.2 software was 

used to incorporate several pieces of data 

for the orthorectification process and mosaic 

construction. First, precise geographic 

coordinates (latitude/longitude) were obtained 

for landmarks within each image using survey 

grade GPS equipment. Approximately 10-15 of 

these landmarks, called “ground control points” 

(GCP’s), were visually identified in each image. 

Most GCP’s persisted from the 1970s through 

January of 2000, and were visible in nearly all 

photographs in all years. A small number of 

additional GCPs were also included in some 

photographs that had large gaps between the 

perennial GCPs. Calibration data from the 

cameras used to take the photographs was 

obtained to correct for lens distortion. USGS 

Digital Terrain Model data was also obtained 

to correct for terrain (elevation) effects. The 

three datasets were then processed with scans 

of aerial photographs using the Geomatica 

OrthoEngine software to produce mosaicks for 

each year.

 A hierarchical classification scheme 

was created to map targeted habitats within 

the park boundary (Figure 2.1, Table 2.2). 

The 20 benthic habitat categories used in 

this assessment were based on a previous 

mapping effort in Puerto Rico and the Virgin 

Islands (Kendall et al. 2002), but were modified 

for the specific objectives of this assessment. 

Thirteen mangrove categories were adopted, 

based on knowledge of species observed at 

SARI (Gladfelter 1988, Knowles 1993), and 

canopy coverage categories defined by the 

Food and Agriculture Organization (DiGregorio 

and Jansen 2000). Similarly, the 17 land cover 

categories used were based on cover types 

utilized in other land cover mapping studies in 

semi-rural tropical areas (Vargas 1974, Smith 

and Brown 1992), and on land cover categories 

relating to resource use/development activities 

of concern to the health of the Salt River Bay 

watershed (USVI Department of Planning and 

Natural Resources 1993). The entire suite of 

50 categories was mapped using the year 2000 

mosaic (Table 2.2). During previous years, only 

the seagrass and mangrove classifications were 

utilized. 

Maps were digitized from the 

orthorectified photo-mosaics using the Habitat 

Digitizer (Kendall et al. 2002) and Image 

Analysis software extensions in ArcView 3.2. 

On-screen digitizing was conducted at 1:1500 

to maximize accuracy and polygon detail, while 

maintaining reasonable digitizing time. The 

minimum mapping unit (MMU) was restricted 

to 100 m2, disallowing the digitization of smaller 

polygons which were difficult to discern given 

the scale and scanning resolution of the 

imagery. With the Habitat Digitizer extension 

activated, polygons were drawn around discreet, 

visually interpreted photographic signatures, and 

assigned a classification category. In addition 

to the original photographs, image diapositives 

and several pieces of collateral information were 

available to assist with habitat identification. 

Previous mapping efforts, descriptive 

references, hand-drawn maps included in 

regional studies, and field mapping of the St. 

Croix Environmental Association mangrove 

restoration plots aided with the digitization 

process (Kendall et al. 2002, Knowles 1993, 

USVI Department of Planning and Natural 

Resources 1993, Gladfelter 1988, Gerhard 

and Bowman 1975). Maps were based on two 

dimensional area and do not take into account 

vertical relief.

Some portions of the marine/estuarine 

environment were not directly interpretable in 

Section 2 Aerial Photographs & Mapping Methods

Date Scale Number of 

Photos 

NOAA/NGS

Roll Number 

1/20/2000 1:20,000 3 00ACN01 

1/31/1992 1:20,000 3 92BCN02 

11/24/1988 1:20,000 3 88ECN 

11/14/1977 1;20,000 1 100-993 

11/20/1971 1:30,000 3 100-722 

Table 2.1. List of photographs used to create orthorectified photographic mosaics
16

Section 2 Aerial Photographs & Mapping Methods

2000 1992 1988 1970's # Polygons Total Area (hectares) # Polygons Total Area (hectares) # Polygons Total Area (hectares) # Polygons Total Area (hectares)

Benthic Habitats

Artificial 7 0.4

Coral Reef and Hardbottom

Coral Reef and Colonized Hardbottom

Aggregated Patch Reefs 2 0.3

Colonized Bedrock 2 1.3

Colonized Pavement 5 80.7

Colonized Pavement with Sand Channels 3 6.7

Linear Reef 7 13.0

Scattered Coral/Rock in Unconsolidated Sediment 2 0.1

Spur and Groove 3 2.8

Uncolonized Hardbottom

Reef Rubble 3 7.1

Uncolonized Bedrock 10 2.7

Uncolonized Pavement 2 1.7

Submerged Vegetation

Macroalgae

Patchy (discontinuous) – 10% to less than 50% cover 15 10.9

Patchy (discontinuous) – 50% to less than 90% cover 6 0.4

Continuous – 90% to 100% cover 2 0.8

Seagrass

Patchy (discontinuous) – 10% to less than 50% cover 76 7.3 63 6.2 56 5.9 55 8.9

Patchy (discontinuous) – 50% to less than 90% cover 59 9.5 45 12.9 65 12.2 49 13

Continuous – 90% to 100% cover 27 12.7 29 10.4 27 13.9 26 12.9

Unconsolidated Sediments

Mud 24 25.1

Sand 41 11.4

Unknown 1 55.0

Mangroves

Avicennia germanis (Black Mangrove)

Sparse – 1% to 15% canopy coverage 6 0.7 19 2.4 5 0.1 5 0.3

Open – 15% to 65% canopy coverage 14 1.8 19 3.1 21 3.2 10 3.1

Closed - >65% canopy coverage 7 3 1 < 0.1 11 10.9 12 8.3

Laguncularia racemosa (White Mangrove)

Sparse – 1% to 15% canopy coverage 0 0 3 < 0.1 0 0 0 0

Open – 15% to 65% canopy coverage 8 0.6 8 0.8 1 < 0.1 3 0.1

Closed - >65% canopy coverage 0 0 0 0 2 < .1 0 0 0

Table 2.2. Heirarchical classification scheme used for mapping benthic, mangrove, and land cover habitats 

within SARI. Area mapped and number of polygons are given for each year and category mapped.
17

2000 1992 1988 1970's # Polygons Total Area (hectares) # Polygons Total Area (hectares) # Polygons Total Area (hectares) # Polygons Total Area (hectares)

Mangroves (Continued)

Rhizophora mangle (Red Mangrove)

Sparse – 1% to 15% canopy coverage 4 0.1 16 0.9 0 0 3 0.1

Open – 15% to 65% canopy coverage 13 0.9 31 1.8 12 0.43 13 0.5

Closed - >65% canopy coverage 18 2.8 6 0.2 27 6.1 17 7.3

Mixed

Sparse – 1% to 15% canopy coverage 0 0 3 0.2 0 0 0 0

Open – 15% to 65% canopy coverage 9 0.5 8 0.8 5 0.2 1 < 0.1

Closed - >65% canopy coverage 2 < 0.1 0 0 8 1.2 3 0.4

Dead 12 8.1 20 12 0 0 4 0.1

Land Cover

Bare Areas

Rock 7 0.5

Sand/Beach 17 1.3

Soil 32 2.1

Developed

Commercial 7 1.4

Residential 14 1.7

Inland Water Bodies

Freshwater Pond 1 0.1

Saltwater Pond 5 2.4

Natural and Semi-Natural Areas

Forest/Trees

Sparse – 1% to 15% canopy coverage 11 1.5

Open – 15% to 65% canopy coverage 60 16.8

Closed - >65% canopy coverage 25 87.8

Shrubs/Bushes

Sparse – 1% to 15% canopy coverage 31 4.6

Open – 15% to 65% canopy coverage 65 5.1

Closed - >65% canopy coverage 10 1.4

Vegetated Field 50 14.2

Roads

Paved 14 1.3

Unpaved 8 2.9

Section 2 Aerial Photographs & Mapping Methods

Table 2.2 (Continued). Heirarchical classification scheme used for mapping benthic, mangrove, and land cover 

habitats within SARI. Area mapped and number of polygons are given for each year and category mapped.
18

photographs due either to turbidity or 

depth. For example, benthic habitat 

at the bottom of Salt River Canyon 

and in the deep regions approximately 

0.5 – 1 km north of the bay, could not 

be seen in aerial photographs. As 

a result, these areas were labeled 

as “unknown” bottom type. Also, a 

large region of high turbidity obscured 

portions of the bottom in the bays 

throughout all years of photography. 

The area encompassed deeper (>1.5 

m) portions of the Salt River Bay, 

the Marina, Sugar Bay, the dredged 

basin, abandoned marina cut, and 

western and southern portions of 

Triton Bay. Though field investigation 

of the deep offshore areas was not 

feasible for this study, ground truthing 

was possible in the much shallower 

bays. Thirty two points distributed 

throughout the bays were checked, 

revealing that areas up to 2 m deep 

typically exhibited patchy (50% to less 

than 90%) algae cover (Appendix E). 

Areas deeper than 2 m consistently 

exhibited mud substrate, devoid of 

vegetation. These observations 

corroborate those of Gerhard and 

Bowman (1975), indicating that 

vegetative growth in Salt River 

Bay ceases at approximately 2 m. 

Therefore, sections of the turbid 

region less than 2 m deep were 

assigned the patchy algal cover (50% 

to less than 90%) classification, and sections 

over 2 m were designated as mud.

 Following the completion of a draft map 

for 2000, features in the imagery that were 

difficult to interpret due to confusing signatures, 

shadows, or high turbidity were checked for 

accuracy. A GIS theme was created with points 

located within polygons in question, or across 

gradients between polygons. Points were 

loaded into a GPS unit, and visited in the field 

for ground validation of habitat type, with a total 

of 166 benthic, terrestrial, and mangrove forest/

marsh locations visited. In the field, habitat type 

and depth where appropriate, was recorded, 

and used to revise draft maps (Appendix E).

RESULTS

Prints, diapositives, and scans (25 

micron resolution) for a total of 184 images of 

the SARI. Most photos were taken at a scale of 

1:20,000, although scales ranged from 1:4,000 

to 1:50,000. The majority (173) were obtained 

from NOAA’s NGS, including 115 color, 28 

color infrared, and 30 black and white infrared 

photographs taken between 1971 and 2000. An 

additional 11 black and white photographs taken 

between 1971 and 1991 were obtained from 

Section 2 Aerial Photographs & Mapping Methods

Table 2.3. List of all photographs obtained of the SARI area. 

Sources include NOAA, and FSA (USDA).

Date Photo Type Scale Source Count

1940's B&W Unknown US Navy Unknown

1971 B&W 1:20,000 USDA 5

11/20/1971 color 1:30,000 NOAA, NGS 10

11/14/1977 B&W infrared 1;20,000 NOAA, NGS 3

11/14/1977 color 1:20,000 NOAA, NGS 9

11/14/1977 color infrared 1:20,000 NOAA, NGS 4

11/30/1977 color 1;50,000 NOAA, NGS 8

11/30/1977 color 1:30,000 NOAA, NGS 3

12/3/1977 color 1:50,000 NOAA, NGS 5

12/3/1977 color 1:30,000 NOAA, NGS 3

12/7/1977 color 1:4,000 NOAA, NGS 11

12/7/1977 color 1:20,000 NOAA, NGS 5

12/7/1977 color infrared 1:4,000 NOAA, NGS 18

12/7/1977 color infrared 1:20,000 NOAA, NGS 6

12/17/1977 B&W infrared 1:4,000 NOAA, NGS 22

12/17/1977 B&W infrared 1:20,000 NOAA, NGS 5

1/31/1985 B&W 1:40,000 USDA 3

11/24/1988 color 1:20,000 NOAA, NGS 7

1991 B&W 1:65,000 USDA 3

1/31/1992 color 1;20,000 NOAA, NGS 4

2/7/1999 color 1:20,000 NOAA, NGS 3

2/18/1999 color 1:20,000 NOAA, NGS 10

3/3/1999 color 1:20,000 NOAA, NGS 2

3/19/1999 color 1:20,000 NOAA, NGS 3

12/16/1999 color 1:20,000 NOAA, NGS 2

1/20/2000 color 1:19,500 NOAA, NGS 19

2/2/2000 color 1:20,000 NOAA, NGS 8

2/26/2000 color 1:20,000 NOAA, NGS 3
19

the United States Department of Agriculture 

(USDA), Aerial Photography Field Office (Table 

2.3). Copies of the 1947 US Navy photographs 

were unavailable at the time the data were 

compiled for this report.

 Orthorectified photographs produced 

for the 1970s, 1988, 1992 and 2000 had a pixel 

size of 0.5 meters, and an average positional 

accuracy (root mean squared error) ranging 

from 1.09 – 2.59 m (Table 2.4.). For year 

2000, a total of 747 polygons were drawn and 

classified for benthic, land cover and mangrove 

habitats. Approximately 2.50 km2

 of benthic 

habitat area, 1.45 km2 of land cover area, and 

0.19 km2 of mangrove area were mapped 

within SARI’s boundaries. Habitat polygons 

ranged in size from 100 m2 (minimum mapping 

unit), to 664,413 m2 (66 hectares) for a section 

of colonized pavement in 2000. During the 

1970’s, 1988, and 1992, a total of 201, 240 

and 263 polygons respectively were drawn for 

mangrove and seagrass habitats.

In 2000, non-vegetated benthic habitats 

covered approximately 153 hectares. Of 

that, approximately 70% was coral reef and 

colonized hard bottom, 23% was unconsolidated 

sediment, and 7% was uncolonized hard bottom. 

Most of the coral reef and colonized hard 

bottom consisted of large regions of colonized 

pavement, located on the shelf to the east and 

west of Salt River Canyon. A large reef rubble 

beach and shore located on the north shore of 

Judith’s Fancy, extended seaward approximately 

100-150 meters from the beach, and accounted 

for much of the uncolonized hard bottom. See 

Section 8 for a quantitative description of reef 

habitats. The large area of muddy bottom in the 

middle of Salt River Bay accounted for 70% of 

the unconsolidated sediment. 

 Seagrass and algae patches shift in size, 

shape and position throughout the time series 

of maps. Notably, a large region of seagrass 

visible southwest of the channel to Salt River 

Canyon during the 70’s, 1988, and 1992, is no 

longer present in 2000. A large, continuous area 

of seagrass in the north-central portion of the 

bay appears to persist between years, though its 

size and shape is variable. See Section 9 for a 

quantitative analysis of seagrass.

Dramatic changes in mangroves coincide 

with the passage of Hurricane Hugo in the fall 

of 1989. Large patches of red (Rhizophora 

mangle) and black mangroves (Laguncularia 

racemosa) mapped before the storm in1988 

were largely denuded or destroyed by 1992. By 

2000, Red and black mangroves appeared to be 

returning to some of these areas, however large 

areas of dead mangrove persisted, particularly 

in lower Sugar Bay. See Section 10 for a 

quantitative analysis of mangrove change.

Terrestrial cover during 2000 was 

dominated by the forests of the steeper 

mountainous areas in the southern portions 

of the park. Field and shrub cover were 

concentrated in northeastern and northwestern 

limits of land near the shore. Though much of 

the area has been designated as low or medium 

density residential (R-1 or R-3) or waterfront 

pleasure (W-1) (Island Resources Foundation 

1993b), relatively few structures have been 

completely built. For a more complete 

description of land cover and land use, see 

Section 13.

MAP USES

 The maps and orthorectified photography 

provide a foundation on which future monitoring 

and research projects within the National Park 

can be based. For example, the distribution 

of organisms based on preferred habitat 

Table 2.4. Estimated horizontal spatial accuracy of 

orthorectified photo mosaicks by time period. Values are 

in meters.

Section 2 Aerial Photographs & Mapping Methods

Year X Y

2000 2.13 2.59

1992 1.53 1.20

1988 1.09 1.21

1977 1.83 1.86

1971 1.90 1.38
20

characteristics may be related to mapped 

habitats, and habitat boundaries. Maps facilitate 

selection of study sites for targeted research 

in specific habitats or on specific organisms 

in the park. Maps also provide a baseline of 

information to which future natural changes, 

restoration activities, and human induced 

impacts may be compared. 

REFRENCES

Di Gregorio, A. and Jansen, L.J.M. 2000 Land 

Cover Classification System, FAO, 

Rome, 179 pp. 

Gerhard, L.C. and J. Bowman. 1975. 

Sedimentation in the Salt River 

estuary, St. Croix, U.S. Virgin Islands. 

Special Publication No. 8., West Indies 

Laboratory, St. Croix, U.S. Virgin Islands. 

Pp. 8-21. 

Gladfelter, W.B. 1988. Marine Field Trip Sites, 

St. Croix U.S.V.I.: Mangroves. In

Tropical Organisms and Communities. 

St. Croix, U.S.V.I., Argus Inc. pp 54-56.

Island Resources Foundation. 1993b. Salt River 

Bay and Watershed Area of Particular 

Concern and Area of Preservation and 

Restoration: A Comprehensive Analytic 

Study. September 1993. Pp. 1-60 and 

Figures

Kendall, M.S., C.R. Kruer, K.R. Buja, J.D. 

Christensen, M. Finkbeiner, R.A. Warner, 

M.E. Monaco. 2002. Methods used 

to map the benthic habitats of Puerto 

Rico and the U.S. Virgin Islands. NOAA 

Technical Memorandum NOS NCCOS 

CCMA 152. NOAA, Silver Spring. 45 

pgs.

Knowles, W. 1993. Wildlife use of Saltwater 

wetlands on St. Croix. Annual narrative 

report for fiscal year 1993. U.S. Virgin 

Islands, Division of Fish and Wildlife. 69 

pp.

Salt River Bay and Watershed (APR) Area 

of particular concern & area for 

preservation and restoration: A 

comprehensive analytic study. 1993.

Virgin Islands Department of Planning 

and Natural Resources, Coastal Zone 

Management Program. Pp. 25-29.

Smith, S. and C. Brown. 1992. Land Use/Land 

Cover Classification Using Digitally 

Merged Spot Panchromatic and Landsat 

Thematic Mapper Imagery. NOAA, 

Springfield, VA. 78 pgs.

Vargas, P.S., 1974. A Detailed Procedure for the 

use of small-scale photography in land 

use classification. NASA Technical Note, 

NASA TN D-7542. Washington D.C. 38 

pgs.

Section 2 Aerial Photographs & Mapping Methods
21

Section 2 Aerial Photographs & Mapping Methods
22

OVERVIEW

 The trade winds dominate the weather 

pattern for SARI. Winds are most intense 

during the winter months and have an easterly 

or east-northeasterly orientation. Wind speeds 

decrease during spring but re-intensify during 

summer months while shifting to a more 

easterly or east-southeasterly orientation. Fall 

winds maintain the westward flow but achieve 

the lowest average intensity. These typical 

weather patterns are interrupted in the winter 

by weak cold fronts and in the summer and fall 

by tropical cyclones which dramatically change 

the direction and intensity of the dominant 

wind patterns. Wind generated waves drive 

water circulation patterns inside and along the 

mouth of Salt River Bay. Rainfall is seasonal 

with a late summer and early fall wet season 

during which most of the annual precipitation 

occurs, contrasting with a late winter and early 

spring dry season. Periods of heavy rain from 

thunderstorms and tropical storms cause the 

only occurrences of freshwater flow down Salt 

River Gut into Sugar Bay (Figure 1.1). Air 

temperatures usually range from ~26° to 30°C 

annually with a daily range of ~2°C. 

METHODS

 Climate data and information were 

obtained from two primary sources, the NOAA/

Atlantic Oceanographic and Meteorological 

Laboratory (NOAA/AOML) and through literature 

search. The NOAA/AOML data provide an 

hourly record of conditions at one site within 

SARI, whereas the literature search provided 

additional descriptive information on climate 

which was compiled and summarized (e.g. 

Island Resources Foundation 1977).

 In 2002 NOAA/AOML installed a 

Coral Reef Early Warning System (CREWS) 

Station in SARI near the west wall of Salt 

River Canyon (17o 47.045’ N, 64o 45.689’ W) 

as one component of NOAA’s Coral Health 

and Monitoring Program. The station records 

several oceanic and atmospheric parameters 

on an hourly basis, including several of interest 

for characterizing climate at SARI such as air 

temperature, wind direction, and wind speed. At 

the time of this assessment, hourly data from 

the CREWS station were available for the period 

between April 2002 and October 2003. All 

parameters were not recorded on all dates and 

times due to periodic maintenance required by 

the instruments. Despite these interruptions, 

the station provides a tremendous volume of 

nearly continuous data on key parameters 

for characterizing environmental conditions 

at SARI. Only the most pertinent summary 

analyses are included in this report. A quality 

control procedure was used to check the data 

for clearly erroneous sensor values which 

were eliminated prior to analysis. Hourly wind 

direction, wind speed, and air temperature are 

plotted based on an average of all 18 months 

of available data. Minimum and Maximum 

monthly air temperatures are also plotted based 

on all available data. Raw wind direction data 

with outliers eliminated is plotted. Additional 

parameters on wind gust speed, direction, 

and duration where collected by the CREWS 

Section 3 Climate

Figure 3.1. NOAA/AOML Coral Reef Early 

Warning System (CREWS) station.

Section 3 Climate
23

sensors, however, these data where not 

analyzed as part of this assessment. 

RESULTS

 St. Croix lies in the region of the 

Caribbean dominated by the trade winds. These 

easterly winds vary seasonally in magnitude 

and direction. During the winter weather period, 

roughly from December through February, the 

trade winds achieve their maximum intensity, 

10 to more than 20 knots, and typically blow 

from east-northeast. During spring, roughly 

March through May, wind speed is reduced 

and is primarily out of the east. During the 

summer, June through August, winds typically 

increase to moderate intensity and typically 

blow from the east or east-southeast. In 

fall, September through November, winds 

typically achieve lowest velocities but maintain 

the dominant easterly or east-southeasterly 

orientation. During the summer and fall periods, 

thunderstorms and hurricanes can occur which 

have dramatic influence on local wind direction 

and intensity. 

 Tropical storms and hurricanes occur 

between June and November with a clear 

peak in abundance in August and September. 

Since the 1930’s, twenty eight storms have 

passed within 60 nautical miles of St. Croix for 

an average occurrence of one every 2.6 years 

(Caribbean Hurricane Network). Four of those 

storms were category three or higher on the 

Saffir Simpson intensity scale (winds over 110 

miles per hour). Hurricane Hugo passed directly 

over St. Croix in September of 1989. This slow 

moving category 4 storm had the most notable 

impacts on SARI of recent storms.

 Rainfall in the assessment area is 

seasonably variable as well. Typical rainfall for 

the SARI area is 35-45 inches annually. Most 

occurs during the late summer and fall wet 

season from August to November during short, 

but intense thunderstorms. The dry season 

occurs in late winter and early spring, roughly 

from February through April. 

 Data from the CREWS Station used in 

the assessment included 9531 observations 

taken hourly between April 2, 2002 and October 

3, 2003. This data represents a typical 18 

month period of weather for the assessment 

site. Deviations from the usual weather pattern 

occurred during this period, providing examples 

of the natural variability of the climate in the 

region. Such deviations in the CREWS data 

are noted and discussed relative to more typical 

weather conditions.

 A plot of average daily air temperature 

during this period indicates a seasonal 

fluctuation from a low of ~27 °C in February 

to a maximum of ~29 °C in September with a 

typical daily range of ~2 °C (Figure 3.2). When 

air temperatures were averaged by hour, the 

22

24

26

28

30

Air Temperature (C)

max

min

2002

Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug

2003

Jul Aug Sept

Section 3 Climate

Figure 3.2. Minimum and maximum air temperature from April 2002 to October 2003.
24 Wind Direction

110

112.5

115

117.5

120

122.5

125

8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7

AM PM

Section 3 Climate

0

10

20

30

Wind Speed (Knots)

Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

2002 2003

26.5

27.0

27.5

28.0

28.5

29.0

Air Temperature (C)

8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7

AM PM

Figure 3.3. Mean hourly air temperature over the course of a 24 hour period, based on CREWS data pooled 

from April 2002 to October 2003.

Figure 3.4. Mean hourly wind direction over the course of a 24 hour period, based on CREWS data pooled 

from April 2002 to October 2003.

Figure 3.5. Wind speed plotted from raw CREWS data from June 2002 to October 2003.

 
25

lowest air temperatures were observed at ~7 AM 

(Atlantic Standard Time) around sunrise and the 

highest were observed at 4 PM prior to sunset 

(Figure 3.3). 

 Wind direction changed during the 

course of the day with winds blowing more 

directly out of the east during daylight hours 

and gradually shifting to east southeast at night 

(Figure 3.4). An abrupt change back to easterly 

winds occurs each morning around sunrise 

over a period of ~2 hours. This daily change 

in wind direction was consistent regardless of 

season. Wind intensity was highly variable 

throughout the year and depended on the timing 

of weak cold fronts during winter months (known 

locally as the “Christmas Winds”) and changes 

in the Bermuda High and Equatorial Trough 

during summer and fall. Such changes in wind 

intensity pattern occur on variable timescales 

but generally lasted a few days to a week. 

These periodic changes can be observed in 

the raw data plotted in Figure 3.5. Deviations 

from the typical weather pattern for this area 

included a winter period of unusually reduced 

and consistent wind intensity with typical speeds 

of less than 10 knots. Winds increased in spring 

to more typical intensity and variability during 

summer and fall with winds of 15-20 knots not 

uncommon.

 Wind intensity also displayed a 

predictable pattern over the course of each day 

(Figure 3.6). Winds are generally the calmest 

during the few hours before dawn and increase 

sharply after sunrise to a maximum speed 

around mid-day. Winds gradually diminish 

through the evening hours and remain fairly low 

during the night. It should also be noted that 

the topography of the landforms around SARI 

are considerable. Depending on the specific 

location within the park, local wind speed and 

direction may deviate widely from the typical 

patterns described here. 

ECOLOGICAL LINKAGES

 Winds play the dominant role in 

controlling currents in Salt River Bay and 

along the bay mouth. The easterly direction 

of winds throughout the year maintains an 

east to west longshore current. This current 

plays the principle role in the gradual process 

of transporting shelf sediments into Salt River 

Canyon down the east canyon wall. 

10

10.5

11

11.5

12

12.5

13

Wind Speed (Knots)

9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7

AM PM

8

Section 3 Climate

Figure 3.6. Mean hourly wind speed over the course of a 24 hour period, based on CREWS data pooled from April 

2002 to October 2003.
26

Section 3 Climate

 Waves generated by the easterly winds 

refract around the Judith’s Fancy headland 

and transport water over the reef crest and into 

Salt River Bay. This is the major driver of the 

current patterns within the assessment area 

(See Currents, Section 6).

 Intense rain from hurricanes or even 

thunderstorms can cause flash flooding in 

the Salt River watershed and result in a large 

freshwater discharge down Salt River Gut into 

Sugar Bay. This can temporarily reduce salinity 

and aggravate already high turbidity levels in 

the assessment area. 

REFERENCES

Island Resources Foundation. 1977. Marine 

Environments of the Virgin Islands. 

Tech. Suppl. No. 1. Prepared for the 

Virgin Islands Government, Coastal 

Zone Management Program. Pp.1-188.

NOAA/Atlantic Oceanographic and 

Meteorological Laboratory. Coral Reef 

Early Warning System (CREWS) Station 

http://www.coral.noaa.gov/crews.
27
28

OVERVIEW

The geological formations of Salt River 

provide the foundation for the region’s ecology. 

Limestone in the south and a variety of rock 

types in the northern portion of the drainage 

comprise the two main geologic formations. 

Holocene reef accretion has significantly 

modified the submerged topography of Salt 

River Canyon and greatly constricted the mouth 

of the estuary. The distribution of sediment 

types in the bays is controlled by depth and 

proximity to terrigenous sources and the bay 

mouth. Terrigenous sediments are flushed 

into the bays down the watershed’s main 

drainage and by erosion of exposed headlands. 

Sediments are dominated by terrigenous types 

in the deepest and southernmost portions of the 

bays. Shallow northern portions of the bays are 

dominated by carbonate sediments primarily 

derived from calcareous algae. Sediments 

outside the bays in Salt River Canyon are almost 

exclusively carbonate and are primarily derived 

from bioerosion of reef corals. Longshore drift 

carries sediment from east to west along the 

shelf. The sediment budget within the canyon is 

characterized by gradual long term build up and 

sudden periodic purging by major storms. Even 

though prevailing conditions have likely occurred 

more than 95% of the time over the last century 

they are only responsible for about a third of the 

total sediment transport in and around Salt River 

Canyon. 

METHODS

 Literature on the geology and geological 

processes within the SARI area were compiled 

for both the bay and canyon/shelf areas. 

These sources often included maps and text 

descriptions on the extent of rock or sediment 

bodies and their relationship with the system’s 

ecology. These diverse sources were then 

combined and condensed into a generalized 

description of the overall geological setting for 

SARI. 

RESULTS

 The major geologic formations for the 

Salt River watershed consist of two primary 

lithologic units (Justus et al 1975, Gill et al 

2002a; Gill et al 2002b). Most of the drainage 

basin and area south of SARI is underlain by 

the Miocene Kingshill Formation. The northern 

portion of the basin including the exposed 

bedrock around the shoreline of SARI consists 

of the Cretaceous Judith’s Fancy Formation. 

The Kingshill Formation is primarily limestone 

whereas the Judith’s Fancy Formation is 

a mixture of volcanoclastics, sandstone, 

mudstone, and contains a few small dioritic or 

gabbroic intrusions. The main stream bed of Salt 

River consists of eroded surface sediments. 

 Sediment in Sugar and Salt River Bay 

consists of two distinct types. Carbonate 

sediments with course grain size (>4 phi) 

are typically located along the sides of Sugar 

Bay and the main body of Salt River Bay 

where water depth is less than ~2m. Finer 

sediments (<4 phi) such as terrigenous silt and 

clay with low carbonate content are primarily 

found in the southernmost reaches of Sugar 

Bay and in the deep, central axis of Sugar 

and Salt River Bays (Justus et al 1975). In 

addition to these differences in sediment type 

Section 4 Geology

Figure 4.1. Beach composed of coral rubble.

Section 4 Geology
29

according to water depth, there is also a gradual 

change from mostly terrigenous sediments 

in the southernmost reaches of Sugar Bay to 

carbonate marine sediments toward the mouth 

of Salt River Bay. Triton Bay presumably 

exhibits a similar distribution of sediment types 

according to depth and proximity to the marine 

environment, although it has not been directly 

evaluated. The carbonate sediments within the 

bays are derived from calcareous algae such 

as Halimeda as well as a variety of benthic 

organisms such as mollusks, foraminifera, and 

echinoids. Terrigenous sediments originate 

primarily from upland erosion and subsequent 

transport to the bays by freshwater runoff down 

the Salt River streambed as well as from a few 

outcrops exposed to wave action (Gerhard and 

Petta 1974). 

 The abundance of terrigenous sediment 

declines abruptly seaward of the reef at the 

mouth of Salt River Bay. This indicates that 

the reef is generally an effective depositional 

barrier that separates bay from canyon and shelf 

sedimentation (Hubbard 1989). Exceptions 

to this general pattern have been observed 

following extreme events such as tropical storms 

or hurricanes, when carbonate sediments 

offshore have been observed to be covered 

with a thin layer of brown, terrestrially-derived 

sediment (Williams 1988). In general, however, 

the shelf and canyon environments of SARI 

are subject to sedimentary processes largely 

separate from those inshore of the bay mouth. 

 The sediment budget and geology of 

the shelf and canyon at Salt River have been 

studied extensively by Hubbard (1989, 1992). 

Sediments outside the bays are carbonate; 

primarily a product of bioerosion of corals. The 

dominant longshore drift in the area is east to 

west, driven by the trade winds. As a result, 

the shelf to the east serves as the major source 

of sediment to the floor of Salt River Canyon. 

Large quantities of material move from the 

shelf with the longshore current, down the 

east wall of the canyon to settle on the canyon 

floor. Once settled, sediments await flushing to 

deeper water through storm driven processes. 

Carbonate sediments produced on the wall and 

shelf to the west of the canyon are either carried 

away westward by longshore currents or are 

rapidly channeled to the canyon floor through 

the numerous vertical cuts in the reef along the 

west wall. Consequently, the west canyon wall 

receives much less sediment than does the east 

wall.

 The floor of Salt River Canyon is 

composed primarily of medium to course 

grained carbonate sand (~0.27-0.99 mm) 

with sediments becoming increasingly finer 

down canyon. Normally the sand surface on 

the canyon floor is a featureless slope with 

occasional mounds of the burrowing shrimp 

Callianassa sp. During storms however, sand 

ripples form on the canyon floor which are then 

eroded by water rushing out of Salt River Bay 

(see Currents, Section 6). 

 The balance between sediment input and 

export in the canyon is controlled by gradual, 

long term accretion and brief, intense erosion 

processes. During predominant or non-storm 

weather conditions, there is gradual transport of 

66,000 kg of sediment to the canyon floor per 

year, with only 18,000 kg of sediment exiting 

the base of the canyon annually. The gradual 

annual net increase of 48,000 kg of canyon 

sediment during predominant conditions is offset 

by massive erosion events associated with 

tropical storms and hurricanes (Williams 1988). 

Such erosion events last only a few hours and 

are due to the intense down canyon currents 

associated with storm surge exiting Salt River 

Bay along the axis of the canyon (see Currents, 

Section 6). For example, during normal, nonstorm weather conditions, ~33 kg of sediment 

move over the shelf edge at Salt River Canyon 

on a day to day basis. Even heavy weather can 

increase this amount to ~440 kg/day. During 

a storm in 1979, ~350,000 kg of sand were 

removed in a single day, a quantity equal to 5-

10 years of sediment accumulation. In a more 

extreme example, Hurricane Hugo moved 

~2,000,000 kg of sand from Salt River Canyon 

into deeper water in a 4-6 hour period. Down 

canyon currents of up to 4 m/s occurred along 

the base of the western canyon wall during the 

passage of Hugo, removing up to 2 m of sand. 

This transport rate was 11 orders of magnitude 

above that measured during fair weather. 

Section 4 Geology
30

ECOLOGICAL LINKAGES

 The sedimentary processes of SARI 

are linked to the ecology of the enclosed 

bay habitats as well as the canyon and 

reefs offshore. The prevalence of carbonate 

sediments in the bays in areas with water 

depth less than ~2m is due in part to the 

high turbidity of the system. The calcareous 

alga Halimeda, responsible for much of the 

carbonate sediments in the bay, doesn’t receive 

sufficient light in water depths more than 2m. 

The turbidity not only influences the distribution 

of carbonate sediment with respect to depth, but 

probably also effects the position of carbonate 

sediments in the bays relative to proximity to the 

bay mouth. Waters become progressively less 

turbid in the bay from the southernmost reaches 

of Sugar and Triton Bays toward the reef at the 

mouth of Salt River Bay (see Water Quality, 

Section 7). 

 Carbonate sediments produced on 

the shelf and wall are primarily a result of 

bioerosion of corals due to parrotfish and other 

rasping grazers. To some extent, they are 

also the result of simple physical breakdown of 

the reef. The east to west longshore drift and 

associated transport of these sediments has a 

major influence on the morphology and benthic 

communities of the east versus west walls of 

the canyon. On the east slope, large quantities 

of sediment transported from the shelf into the 

canyon discourages extensive growth of hard 

corals (see Reef and Hardbottom, Section 8). 

In contrast, more vigorous coral growth and 

a steeper wall formation are observed on the 

west wall, where less sediment is received (see 

Currents, Section 6). 

REFERENCES

Gerhard, L.C., and T.J. Petta. 1974. Mixed 

carbonate and terrigenous marine 

environment, Sugar Bay, St. Croix. 

In: Guidebook to the Geology and 

Ecology of some Marine and Terrestrial 

Environments, St. Croix US Virgin 

Islands. HG Multer and LC Gerhard, 

Eds. Special Publication Number 5. West 

Indies Laboratory, St. Croix USVI. Pp. 

51-54

Gerhard, L.C., and J. Bowman. 1975. 

Sedimentation in the Salt River Estuary, 

St. Croix US Virgin Islands. Special 

Publication Number 8. West Indies 

Laboratory, St. Croix USVI. Pp. 1-56

Gill, I.P., Hubbard, D.K., McLaughlin, P.P., 

and Moore, C.H. 2002. Geology of 

central St. Croix, U.S. Virgin Islands. 

In: Geology and Hydrogeology of the 

Caribbean Islands Aquifer System of 

the Commonwealth of Puerto Rico and 

the U.S. Virgin Islands. U.S. Geological 

Survey Professional Paper 1418. Pp. 

79-97.

Gill, I.P., Hubbard, D.K., McLaughlin, P.P., and 

Moore, C.H. 2002. Distribution and 

types of porosity within the Kingshill 

aquifer. In: Geology and Hydrogeology 

of the Caribbean Islands Aquifer System 

of the Commonwealth of Puerto Rico and 

the U.S. Virgin Islands. U.S. Geological 

Survey Professional Paper 1419. Pp. 

123-131.

Hubbard, D.K. 1986. Sedimentation as a control 

of reef development: St. Croix, USVI. 

Coral Reefs 5:117-125

Hubbard, D.K. 1989. Depositional Environments 

of Salt River Estuary and Submarine 

Canyon, St. Croix, USVI. In: Terrestrial 

and Marine Geology of St. Croix, US 

Virgin Islands. D.K. Hubbard, Ed.. 

Special Publication Number 8. West 

Indies Laboratory, St. Croix, USVI. Pp. 

181-196

Hubbard, D.K. 1992. Hurricane-induced 

sediment transport in open-shelf 

tropical systems- An example from St. 

Croix, U.S. Virgin Islands. Journal of 

Section 4 Geology
31

Section 4 Geology

Sedimentary Petrology 62:946-960

Williams, S.L. 1988. Disturbance and recovery 

of a deep-water Caribbean seagrass 

bed. Marine Ecology Progress Series 

42:63-71
32

64°46'0"W

64°46'0"W

64°45'30"W

64°45'30"W

64°45'0"W

64°45'0"W

17°46'0"N

17°46'0"N

17°46'30"N

17°46'30"N

17°47'0"N

17°47'0"N

17°47'30"N

17°47'30"N

0 500Meters

Bathymetry

Park Boundary

Depth (m)

-533 - -50

-50 - -25

-25 - -10

-10 - -6

-6 - -5

-5 - -4

-4 - -3

-3 - -2

-2 - -1

-1 - 0

Section 5 Bathymetry

Figure 5.1. Interpolated bathymetry for SARI, based on the available soundings conducted in 1982 and 1977 from 

NOAA Geophysical Data System (GEODAS).
33

OVERVIEW 

A bathymetry map for the Salt River Bay 

area was created based on soundings from 

NOAA hydrographic surveys. This map may 

be used for modeling, zoning, and research 

planning, but should not be used for navigation.

Although the accuracy assessment of 

this map is based on recently collected data, 

the soundings from which the map was created 

are more than 20 years old. Bathymetry can 

change over time due to natural processes 

such as deposition and sediment transport as 

well as anthropogenic factors such as dredging 

and filling which have had a large impact on 

the bathymetry of Salt River Bay in the past. 

The areas of Salt River Bay most influenced by 

these activities include the dredged areas of the 

marina, the channel to Triton Bay and the NOAA 

dock, the basin northeast of Triton Bay, and the 

abandoned marina cut on the east side of Triton 

Bay (Figure 1.1). Natural processes responsible 

for changes in bathymetry due to movement of 

sediments include sedimentation from runoff and 

removal of sediment from the bays and canyon 

during storms. Continuing development of 

the watershed is likely to increase erosion and 

sedimentation rates.

METHODS 

Soundings data used in creating the 

bathymetry map were obtained from the 

GEOphysical DAta System (GEODAS) which is 

a compilation of all NOAA hydrographic survey 

data. Soundings available for the Salt River 

area were from surveys conducted in 1977 

and 1982, with the majority (95%) of the data 

from the 1982 surveys. All soundings were 

adjusted to mean high water. Soundings used 

for accuracy assessment were obtained during a 

March 2004 field mission. 

Soundings data were interpolated using 

the triangulated irregular network (TIN) method 

in the 3D-Analyst extension for ArcMap 8.3. 

This method involves automated creation of a 

network of non-overlapping triangles from all 

combinations of three nearest points. Each 

triangle is given a depth value based on the 

measured depths at each vertex of the triangle. 

Lines and polygons of known depth can also be 

used to increase the accuracy of the resulting 

bathymetry map. For this analysis, soundings 

were used as mass points (i.e. one dimensional 

point data) and a shoreline shapefile (derived 

from the 2000 aerial photograph) was used as 

a hard zero depth fill (i.e. a two-dimensional 

polygon for which depth was set to zero). 

Emergent reefs to the west of the mouth of Salt 

River Bay and Whitehorse Reef were digitized 

from the 2000 aerial photograph and used as 

hard fills with a value of 0.15m since they are 

barely submerged features where no depth 

sounding data were available. This forced the 

bathymetric model nearly to the surface in these 

areas to match the approximate depth of these 

reefs. The resulting TIN file (which is made up 

of triangles of various sizes) was converted to a 

5m grid for analysis and display.

To assess the accuracy of the 

bathymetry map, 51 points randomly selected 

from the region shoreward of the barrier 

reef were sampled using a hand-held depth 

echosounder (Appendix E). The measured 

depth at these points was compared to the 

predicted depth at the same location from the 

bathymetry map. The correlation coefficient 

between the observed and predicted values 

was calculated to assess the overall map 

accuracy. In addition, the error distribution 

was examined in order to assess potential bias 

and to determine the reliability of predictions 

within different depth intervals. Although the 

accuracy of the bathymetry map is likely to vary 

between different areas of the study region 

(due to factors such as uneven distribution of 

soundings and differences in bottom slope), this 

spatial variation could not be estimated from the 

limited number of accuracy assessment points 

available.

RESULTS

The average mapped depth in Salt River 

Section 5 Bathymetry

Section 5 Bathymetry
34

Bay (shoreward of the barrier reef) is 2.2m with 

a maximum depth of 5.4m found in mid-bay. 

The average depth within the park boundaries 

(including bay and canyon waters) is 23m. 

The deepest part of the canyon within the park 

boundaries is 289m. Using a tidal range of 

0.3m, the total area of the intertidal zone within 

the bay is estimated to be 2.4 hectares (Figure 

5.1). 

Notable bathymetric features within the 

park boundaries include the canyon walls (the 

western wall is vertical or overhanging in some 

places and steeper than the eastern wall), the 

barrier reef extending across the mouth of Salt 

River Bay, and the channel through the barrier 

reef. Dredged areas include the Marina, the 

southern tip of Triton Bay, a channel through 

the sand bar at the mouth of Triton Bay, and the 

abandoned marina cut and dredged basin east 

of Salt River Bay (see Locator Map, Figure 1.1).

The accuracy assessment R2 for the 

linear regression of predicted versus observed 

depth (Figure 5.2) was 0.82. In other words, 

the bathymetry map accounts for 82% of 

the observed variability in depth. The mean 

absolute error was 0.43m, with no apparent 

relationship between error and predicted or 

observed depth, i.e. the mean error of 0.43m is 

a reasonable estimate of the expected error at 

both deep and shallow sites within the bay. No 

estimate of accuracy is available for the canyon 

or other areas beyond the barrier reef.

ECOLOGICAL LINKAGES 

Salt River, Triton, and Sugar Bays 

comprise a shallow estuary connected to a deep 

submarine canyon through a narrow break in 

the reef crest at the mouth of Salt River Bay. 

This unique geomorphology has important 

consequences for the ecology of the bay-canyon 

system and is responsible for Salt River Bay’s 

value as a small protected harbor or “hurricane 

hole.” The narrow channel between the bay and 

the canyon allows for flux of water, nutrients, 

and marine organisms between these two areas, 

while protecting the bay from waves. 

The bay’s bathymetric profile 

is responsible for many aspects of the 

Section 5 Bathymetry

R2 = 0.821

-6

-5

-4

-3

-2

-1

0

-5 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0

Observed Depth (m)

Predicted Depth (m) Figure 5.2.. Linear regression of predicted versus observed depth in SARI.
35

distribution of chemical and biological 

parameters. For example, the areas of the 

bay deeper than 2 m, where light availability 

at the substrate level is limited, are unsuitable 

for submerged aquatic vegetation. The deeper 

areas of the mid-bay are also more subject to 

anoxia and have limited biological communities 

(Gerhard and Bowman, 1975). The intertidal 

zone within the bay is an important foraging area 

for many wading birds (see bird section).

 The contrasting bathymetric profiles of 

the east and west canyon walls are the result 

of the interplay between longshore currents, 

sediment transport, and coral growth. Higher 

sedimentation rates along the eastern wall 

discourage extensive coral growth and accounts 

for the occurrence of a more gradual slope on 

that side of the canyon (see currents, geology, 

and reefs sections). Lower sedimentation rates 

along the western wall result in more vigorous 

coral growth and the formation of steeper, 

often overhanging slopes. An excellent three 

dimensional sketch of the differing canyon walls 

can be found in Hubbard 1986.

Accurate GIS bathymetry maps provide 

a foundation for many different types of spatial 

analysis including benthic habitat delineation 

(e.g., Kendal et al., 2004) and habitat suitability 

modeling (e.g., Rubec et al., 1999). They 

are also useful for identifying depth strata for 

selection of stratified random sampling points. 

The map will facilitate such analyses and field 

investigations for continued monitoring and 

research conducted in SARI.

REFERENCES

Gerhard, L. C., and J. Bowman. 1975. 

Sedimentation in the Salt River 

Estuary, St. Croix, U.S. Virgin Islands. 

Special Publication No. 8. West 

Indies Laboratory, Fairleigh Dickinson 

University.

Hubbard, D.K. 1986. Sedimentation as a control 

of reef development: St. Croix, USVI. 

Coral Reefs 5:117-125

Hubbard, D. K. 1992. Hurricane-induced 

sediment transport in open-shelf 

tropical systems – an example from St. 

Croix, U.S. Virgin Islands. Journal of 

Sedimentary Petrology. 62(2): 946-960.

Kendall, M.S., O.P. Jensen, M.E. Monaco, 

D. Field, C. Alexander, G. McFall, R. 

Bohne,. In Press.. Benthic mapping on 

the Georgia bight: sonar, video transects, 

and an innovative approach to accuracy 

assessment. Journal of Coastal 

Research.

NOAA/GEOphysical DAta System: http://www.

ngdc.noaa.gov/mgg/geodas/geodas.html.

Rubec, P. J., Bexley, J. C. W., Norris, H., Coyne, 

M. S., Monaco, M. E., Smith, S. G., and 

J. S. Ault. 1999. Suitability modeling to 

delineate habitat essential to sustainable 

fisheries. American Fisheries Society 

Symposium 22:108-133.

Section 5 Bathymetry
36

64°46'0"W

64°46'0"W

64°45'30"W

64°45'30"W

64°45'0"W

64°45'0"W

17°46'0"N

17°46'0"N

17°46'30"N

17°46'30"N

17°47'0"N

17°47'0"N

17°47'30"N

17°47'30"N

0 500 Meters

Currents

Surface

Bottom

Longshore Current

Longshore Current

Flood

Ebb

Flood

Ebb

Flood/Ebb

Ebb

Ebb

Ebb

Wind Driven

Section 6 Currents

Figure 6.1. Map of generalized currents in SARI.
37

OVERVIEW

Water currents in SARI are largely wind 

and wave driven with only a minor influence 

attributable to the small tides (less than 30 cm) 

in this part of the Caribbean. The dominant 

currents along the north coast of St. Croix 

run from east to west driven by easterly trade 

winds. Wind and waves transport surface 

water southward over the reef crest at the 

mouth of Salt River Bay. This causes water 

to accumulate within the bay until sufficient 

volume builds, tide ebbs, and/or winds relax 

causing water to flow out through the opening 

in the reef into the head of Salt River Canyon. 

Once in the canyon, currents oscillate up and 

down the axis of the canyon at low velocity 

(~10-15 cm/s) until the tide ebbs at which time 

current flows more regularly down canyon at 

a higher velocity (~20 cm/s). Despite these 

general patterns, bay, canyon, and longshore 

currents are highly variable, with intensities 

changing dramatically depending upon local 

wind conditions. For example, the intense 

winds and waves associated with Hurricane 

Hugo in 1989 transported a large volume of 

surface water into the bays, causing storm 

surge within them up to 1.0-1.5 m. When such 

a large volume of water exits the bays through 

the channel into the canyon, consistent down 

canyon current speeds of ~200 cm/s have been 

observed.

METHODS

 Literature on the current patterns within 

the SARI area were compiled for both fair 

weather and storm conditions. Current patterns 

were rarely the sole subject under investigation, 

rather, studies addressed some component of 

SARI currents tangentially as they related to 

some other topic such as sediment transport,

marina development, or algal growth. These 

sources often included maps and text 

descriptions of currents for discrete seasons, 

conditions, or portions of SARI (e.g. bay during 

summer vs. canyon during storm). These 

diverse sources were then combined and 

condensed to form the generalized description 

and map of overall SARI current patterns. 

RESULTS

 The Salt River system is not truly 

estuarine and does not display the typical 

current patterns of an estuary. For the last 

several decades an ephemeral stream has 

run into Sugar Bay only during times of heavy 

rainfall. Rainwater from the ~12 km2 watershed 

flows down the streambed into the marsh south 

of Sugar Bay. The stream bed flattens into a 

sheet flow percolating through the marsh and 

mangroves and then reconcentrates most flow 

into a single discharge into Sugar Bay. During 

at least one period of heavy rain, a slight salt 

wedge was observed to form with surface 

waters exhibiting reduced salinity compared to 

waters deeper in the bay. Typically, however, 

the salinity of the bay approximates that of 

the open Caribbean to the north, or is slightly 

higher due to evaporation (Shepard and Dill 

1977). 

Currents within SARI are driven 

primarily by winds and to a lesser degree by 

tides. Tides in this part of the Caribbean are 

quite small, generally less than 30 cm and 

exhibit a diurnal pattern (one high and one low 

per day). Seaward of the reef, a fairly regular 

east-to-west current is driven by wind and 

waves breaking on the eastern end of the reef. 

The dominant trade winds from the northeast 

push water along the surface over the reef crest 

into Salt River Bay, before continuing westward. 

Typical wave height is 0.3-1 m with periods of 

4-6 seconds. To compensate for the volume 

of water entering the bay over the reef crest, 

water exits through the channel connecting the 

bay and the head of Salt River Canyon. This 

flow through the reef cut and down the canyon 

is not continuous. Release of the water built 

up in the bay is triggered by the falling tide or 

relaxation of the trade winds. Once through 

the cut in the fringing reef, currents continue 

down the axis of the canyon especially during 

Section 6 Currents

Section 6 Currents
38

times when the bay water exhibits elevated 

salinity and therefore greater density than shelf 

waters (Shepard and Dill 1977). Currents in 

the canyon are highly oscillatory, alternating 

along the axis of the canyon at irregular intervals 

averaging about 30 minutes. A tidal cycle can 

be partially discerned in these oscillations, 

particularly during ebb tides when currents flow 

more consistently down canyon and achieve 

velocities higher than those of the oscillating 

currents. Down canyon currents follow a 

predicable flow pattern once through the reef. 

At first, currents in the head of the canyon move 

along the eastern wall. However, below a depth 

of 20 m, flow shifts to the western side of the 

canyon. During fair weather, currents within the 

canyon are slow, rarely exceeding ~10-15 cm/s 

during oscillating periods, and flowing faster 

during falling tides at ~20 cm/s. Longshore 

currents superimposed on this bay and canyon 

flow are typically weak (~5 cm/s) and move in a 

westerly direction along the north shore. Flow 

in Triton and Sugar Bays to the south reverse 

direction with the tides, resulting in exchange of 

water between the bay mouth and the southern 

reaches of these inner bays. Despite these 

general patterns, bay, canyon, and longshore 

currents are highly variable with intensities 

changing dramatically according to local wind 

conditions.

 During storms, greater amounts of water 

are forced over the reef into the estuary by 

larger waves (Hubbard 1989), resulting in an 

exaggeration of the processes described above. 

Water levels can be elevated within Triton 

and Sugar Bays by more than 30 cm during 

small storms to over a meter during powerful 

hurricanes. As storms pass, or when winds 

forcing and holding water in the bays relax or 

change direction, water trapped within the bays 

is released through the channel in the barrier 

reef. Down canyon currents exceeding 50 

cm/s have been measured during small storms 

(Williams 1988). This process was examined in 

detail during Hurricane Hugo in 1989 (Hubbard 

1992) when water was piled against the shore 

and into the bays as the category 4 hurricane 

approached. Wave heights on the north coast 

reached 3.5 m. As Hugo approached, storm 

surge reached 1.0-1.5 m on the north shore of 

St. Croix. Wind direction changed as the storm 

passed overhead, and the mass of water in Salt 

River, Triton, and Sugar Bays was released 

into the head of the canyon through the reef 

cut. For a period of 4-6 hours, net down canyon 

currents reaching 200 cm/s and oscillatory 

flows up to 400 cm/s occurred along the base 

of the western canyon wall. Based on sediment 

scour patterns, the zone of maximum flow was 

probably confined to the west wall. 

ECOLOGICAL LINKAGES

 Down canyon currents driven by major 

hurricanes are an important mechanism 

for periodically flushing canyon sediments, 

and offsetting the usual imbalance between 

sediment import and export (Hubbard 1992). 

Water trapped within the bays by storm winds 

and waves flushes through the reef cut, carrying 

large quantities of sediment and organic debris 

down the canyon (See Geology, Section 4). 

This continually discourages coral growth along 

the lower portions of the western canyon wall 

where currents can be most intense (See Reef 

and Hardbottom, Section 8). 

 The east to west direction of longshore 

drift along the north shore of St. Croix is also 

suggested as a controlling mechanism on the 

faunal differences between the east and west 

walls of Salt River Canyon (Hubbard 1989)(See 

Reef and Hardbottom, Section 8). Over twice 

as much sediment is carried over the east wall 

into the canyon compared to the west wall (see 

Geology, Section 4), resulting in different benthic 

assemblages on each side of the canyon. On 

the east side, there is an abundance of algal 

covered cobbles, with sponges and gorgonians 

as the dominant benthic fauna. Corals are small 

and include mostly sediment tolerant species. 

In contrast, the west wall has much greater 

coral cover and larger colonies (See Reef and 

Hardbottom, Section 8). 

Section 6 Currents
39

REFERENCES

Hubbard, D.K. 1989. Depositional 

Environments of Salt River Estuary and 

Submarine Canyon, St. Croix, USVI. In: 

Terrestrial and Marine Geology of St. 

Croix, US Virgin Islands. DK Hubbard, 

Ed. Special Publication Number 8. West 

Indies Laboratory, St. Croix, USVI. Pp. 

181-196

Hubbard, D.K. 1992. Hurricane-induced 

sediment transport in open-shelf 

tropical systems- An example from St. 

Croix, U.S. Virgin Islands. Journal of 

Sedimentary Petrology 62:946-960

Josselyn, M.N., G.M. Cailliet, T.M. Niesen, R. 

Cowen, A.C. Hurley, J. Connor, and S. 

Hawes. 1983. Composition, Export and 

Faunal Utilization of Drift Vegetation 

in the Salt River Submarine Canyon. 

Estuarine, Coastal and Shelf Science

17:447-465

Shepard, F.P., and R.F. Dill. 1977. Currents 

in submarine canyon heads off North 

St. Croix, US Virgin Islands. Marine 

Geology 24:M39-M45 

Williams, S.L. 1988. Disturbance and recovery 

of a deep-water Caribbean seagrass 

bed. Marine Ecology Progress Series 

42:63-71

Section 6 Currents
40

Section 7 Water Quality

OVERVIEW

Waters within Salt River Bay are 

designated by the Virgin Islands Department 

of Environmental Protection (DEP) as Class 

B according to the EPA’s Integrated Reporting 

format. Class B waters are designated for 

Primary Contact Recreation and Aquatic Life 

Use Support with allowable pollutant levels set 

according to the Virgin Islands Water Quality 

Standards (Division of Environmental Protection, 

2002). Water quality in portions of Sugar and 

Triton Bays farthest from the mouth of Salt 

River Bay periodically have lower DO and 

higher turbidity levels than allowable for Class 

B waters. The marina has had low levels of DO 

during almost all sampling times and occasional 

spikes in bacterial load. These conditions will 

probably continue to occur periodically until 

the factors that influence these parameters 

have changed. Erosion and discharges in the 

watershed appear to be primary threats to water 

quality. Contaminants such as pesticides and 

heavy metals are not currently monitored at 

SARI.

METHODS

Water quality data for the ecological 

assessment were obtained from two primary 

sources, the NOAA/Atlantic Oceanographic 

and Meteorological Laboratory (NOAA/AOML) 

and the USVI/DPNR/Division of Environmental 

Protection (DEP). The NOAA/AOML data 

provide an hourly record of conditions at one site 

in the study area whereas the DEP data provide 

a monthly to annual record of conditions at 10 

sites (see Locator Map, Figure 1.1). A recent 

inventory of water quality data was conducted 

for all National Parks including SARI by the 

NPS/Water Resources Division (NPS/WRD, 

1999). Their search included all information 

in the EPA’s data storage and retrieval system 

(STORET), discharges by industrial facilities, 

drinking water intakes, water gauges, and 

water impoundments. This search indicated 

no data types for SARI exist except for those 

in STORET. Since the primary purpose of the 

NPS/WRD report was to create in inventory 

of data holdings, not to create customized 

interpretation on water quality for any particular 

park, the report was used in this assessment 

only to cross-check data obtained directly from 

STORET. 

 As described in section 3 on climate, in 

2002 NOAA/AOML installed a Coral Reef Early 

Warning System (CREWS) station in SARI near 

the west wall of Salt River Canyon (17 degrees 

47.045 minutes N, 64 degrees, 45.689 minutes 

W) as one component of NOAA’s Coral Health 

and Monitoring Program. The station records 

several parameters of interest for monitoring 

water quality such as water temperature, salinity, 

and both photosynthetically active radiation 

(PAR; μmol quanta m-2s-1) and ultra-violet 

(UVB; mW/cm2) radiation at the water surface 

and 1 m depth. The hourly data is nearly 

continuous for April 2002 through October 2003, 

except for brief periods needed for instrument 

maintenance. 

Maximum daily water temperature and 

salinity are plotted for all 18 months of available 

data. Values of PAR at the surface (PARS) 

and 1 m depth (PAR-1) were available only for 

April 2002 through Dec 2002. Mean PARS 

and PAR-1 were calculated hourly for this nine 

Figure 7.1. Sediment plume flowing from Sugar 

Bay, visible in 1970’s aerial photograph.

Section 7 Water Quality
41

month period to examine how light patterns 

change in the area over the course of one day. 

Sufficient data are not yet available to examine 

the differences in PAR between seasons. UVB 

data were unavailable at the time this report was 

written. 

DEP has collected several variables on 

water quality in SARI periodically since 1972 

and more frequently after 1981. Variables 

include dissolved oxygen, fecal coliform, 

nutrients, salinity, temperature, and turbidity. 

Data were collected irregularly between 1 and 

8 times a year at 2 to 10 stations throughout 

the bay. Data before 1981 were not considered 

in this analysis due to their age, extremely low 

sample size (in most cases, only one station 

visit annually), and inconsistent methodology. 

DEP data are periodically provided to the EPA 

and archived into the STORET system. A 

complete set of all DEP water quality data for 

SARI (Stations 33a-33j) (see Locator Map, 

Figure 1.1) collected after 1981 were obtained 

by accessing the STORET archives and cross 

checking those records against raw data sheets 

from DEP. A quality control procedure was 

used to check, reformat, and prepare the data 

for analysis. Data records not yet in STORET 

from 2000 to 2002 were entered into the 

database directly from DEP field sheets, and 

screened for obvious errors. No analyses were 

attempted for nutrients, pH, or total suspended 

solids since there were very few records for 

those variables. Mean and standard error are 

reported for dissolved oxygen, fecal coliform, 

turbidity, temperature, and salinity by station. 

Where sufficient data were present, yearly and 

seasonal trends were explored for each variable 

at key stations. Additionally, differences in mean 

value of these parameters before versus after 

Hurricane Hugo were explored. Differences 

in mean values of parameters among stations 

were examined using the Tukey-Kramer multiple 

means comparison procedure once values were 

transformed to meet statistical assumptions. 

Other observations on water quality based on 

this dataset that are relevant to the ecological 

assessment are provided. 

RESULTS

Data from the CREWS Station used 

in the analysis included 9531 observations of 

the various parameters taken hourly between 

April 2, 2002 and October 3, 2003. A plot of 

water temperature from September 2002 to 

August 2003 indicates a seasonal fluctuation 

from ~27 °C in February/March to ~29.5 °C in 

September/October with an average daily range 

of 0.25-0.75 °C (Figure 7.2). Lowest hourly 

water temperatures were observed at ~7 AM 

(local time) around sunrise and the highest were 

observed at 5 PM around sunset. 

Values of PARS and PAR-1 both followed 

a bell shaped pattern over the course of the day 

(Figure 7.3). PAR began increasing from zero at 

approximately 6AM (depending on the season), 

peaked at noon, and declined to zero again by 

6PM. Peak PARS values were approximately 

two times higher than peak PAR-1 values. 

Department of Environmental Protection 

water quality data used for analysis consisted 

Section 7 Water Quality

2002

27

28

29

30

Water Temp (C)

Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug

2003

Figure 7.2. Water temperature (C) from CREWS station between September 2002 and August 2003.
42

of 257 station visits and spanned 1981 to 

2002. The number of visits and parameters 

recorded were highly variable among stations. 

Stations with the largest number of visits were 

the Columbus Landing (station A) and Marina 

(station C) with 58 and 66 respectively (see 

Locator Map, Figure 1.1). In contrast, other 

stations were only visited between 15 and 

17 times over the 20 years of data collection. 

Further adding to the irregularities in sampling, 

not all variables were recorded during each 

station visit. As a result, comparisons among 

stations and variables must be interpreted with 

caution and should be used to design more 

robust sampling and investigation rather than 

to draw conclusions. An excellent summary of 

additional caveats for interpreting STORET data 

is given in the NPS/WRD (1999) report.

Average values of dissolved oxygen, 

fecal coliform, salinity, temperature, and turbidity 

are listed by station in Table 7.1 (see Locator 

map, Figure 1.1). Significant differences were 

found among stations for dissolved oxygen and 

turbidity according to distance from the mouth 

of the bay. When data across all seasons and 

years were pooled, stations nearest the bay 

mouth, namely Columbus Landing (station A) 

and Deep Grassbed (station E) had lowest 

Section 7 Water Quality

Water Quality Parameters

Oxygen Oxygen Fecal Coliform Fecal Coliform Salinity Temperature Turbidity

Station ID Description Latitude Longitude (% Sat.) (mg/l) (#/100ml) Filter (PSU) (C) (NTU)

33A Columbus Landing -64.7589 17.7803 83.7 +/- 1.8 6.8 +/- 0.1 4.8 +/- 3.2 14.5 +/- 13.1 36.3 +/- 0.2 27.8 +/- 0.2 1.0 +/- 0.2

33B Shallow Grassbed -64.7589 17.7772 74.7 +/- 3.4 6.7 +/- 0.3 0.2 +/- 0.2 67.8 +/- 66.4 36.4 +/- 0.4 27.5 +/- 0.4 3.3 +/- 0.7

33C Salt River Marina -64.7619 17.7751 66.9 +/- 1.5 5.3 +/- 0.1 50.5 +/- 24.5 26.2 +/- 13.0 35.9 +/- 0.2 28.5 +/- 0.2 2.6 +/- 0.2

33D Sugar Bay -64.7592 17.7707 65.7 +/- 4.2 5.4 +/- 0.3 0.6 +/- 0.4 79.3 +/- 54.7 36.1 +/- 0.4 28.2 +/- 0.5 4.3 +/- 0.8

33E Deep Grassbed -64.7558 17.7785 81.4 +/- 1.2 6.9 +/- 0.2 0.2 +/- 0.2 33.0 +/- 30.7 36.3 +/- 0.4 27.4 +/- 0.3 1.3 +/- 0.3

33F Beach -64.7555 17.7753 77.7 +/- 2.6 6.6 +/- 0.2 0.0 +/- 0.0 62.3 +/- 34.0 36.5 +/- 0.4 27.8 +/- 0.5 4.2 +/- 1.0

33G Old NOAA Dock -64.7542 17.7739 70.2 +/- 3.2 5.8 +/- 0.2 42.8 +/- 41.4 63.4 +/- 38.7 36.4 +/- 0.4 28.1 +/- 0.4 3.6 +/- 0.5

33H Bird Sanctuary -64.7526 17.7708 69.5 +/- 3.2 5.5 +/- 0.2 0.3 +/- 0.3 59.9 +/- 56.8 36.2 +/- 0.4 28.3 +/- 0.5 3.0 +/- 0.6

33I Steeple -64.7521 17.7771 73.2 +/- 2.9 5.9 +/- 0.2 2.3 +/- 1.4 1.0 +/- 0.0 36.4 +/- 0.4 27.7 +/- 0.4 4.6 +/- 0.8

33J East Cove -64.7530 17.7799 81.0 +/- 4.0 6.6 +/- 0.2 0.2 +/- 0.2 58.3 +/- 57.0 36.7 +/- 0.4 27.7 +/- 0.3 2.1 +/- 0.5

Grand Means: N/A N/A 73.8 +/- 1.0 6.1 +/- 0.1 14.9 +/- 6.1 39.7 +/- 9.6 36.2 +/- 0.1 28.0 +/- 0.1 2.6 +/- 0.2

values are mean+/- SEM

0

1000

2000

9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7

Surface

1 meter

PAR

AM PM

Figure 7.3. Mean hourly PAR (photosynthetically active radiation) at the surface (PARS) and at 1 meter (PAR-1) over 

the course of a 24 hour period. Averages are based on CREWS data pooled from April through December, 2002.

Table 7.1. Average values of dissolved oxygen, fecal coliform, salinity, temperature, and turbidity listed by station. DEP 

data was pooled from 1981-2002. Values are mean +/- SEM.
43

-4

-3

-2

-1

0

1

2

3

100 300 500 700 900 1100 1300

log NTU

A

C

B

D

E

F

H

I

J

G

Distance to Bay Mouth (m)

log NTU = -0.46336 + 0.0012875 Dist. (m)

Analysis of Variance Statistics

R2 = 0.236467

P < 0.001

levels of turbidity at 1.0 to 1.3 nephelometric 

turbidity units (NTU), presumably due to their 

proximity to clear oceanic water and their large 

distance from runoff sources (Figure 7.4). In 

contrast, stations farthest from the bay mouth 

such as Sugar Bay (station D) had over four 

times higher mean turbidity values. The 20 year 

average for turbidity at the Steeple (station I), 

Sugar Bay (station G), NOAA Dock, and Beach 

stations was higher than allowable levels for 

Class B waters (not to exceed 3 NTU) although 

the most recent values have been within 

acceptable limits. 

Stations farthest from the bay mouth, 

including Marina, Sugar Bay, NOAA Dock, 

and Bird Sanctuary (see Locator Map, Figure 

1.1) had lowest levels of dissolved oxygen 

with mean values of 5.0 to 5.7 mg/l (Figure 

7.5). In contrast, the station closest to the 

bay mouth, Columbus Landing, had a mean 

dissolved oxygen value of 6.8 mg/l. For these 

areas, factors contributing to low dissolved 

oxygen probably include high turbidity, poor 

circulation, slightly higher mean temperature, 

and proximity to large areas of sediment with 

high organic content. The 20 year average of 

dissolved oxygen levels at the Marina is below 

allowable levels for Class B waters (less than 

5.5 mg/l). In 1998, the DEP listed this station 

as having “Impaired Waters” with respect to 

dissolved oxygen due to erosion from derelict 

land, marina, boat, and residential discharges. 

Mean values in 2000 and 2001 remained below 

5.5 mg/l indicating that unacceptably low oxygen 

levels most likely will continue to occur in the 

Marina until changes in practices that effect 

oxygen levels are implemented. Other sites, 

especially those far from the bay mouth such as 

the Bird Sanctuary and Sugar Bay, had average 

dissolved oxygen values very close to the lowest 

allowable level.

Temperature was the only variable with 

a consistent seasonal trend across all stations. 

Also of note, when selected stations were 

examined individually (listed in parenthesis) 

there were no significant seasonal or yearly 

Section 7 Water Quality

Figure 7.4. Log transformed NTU (nephelometric 

turbidity unit) data plotted against distance from the Salt 

River Bay mouth. Data pooled from all DEP sites sampled 

during 1981 to 2002 was used in this analysis. Letters 

denote sampling sites (see Locator Map, Figure 1.1).

Figure 7.5. Dissolved oxygen (mg/l) plotted against 

distance from the Salt River Bay mouth. Data pooled from 

all DEP sites sampled during 1981-2002 where used in 

this analysis. sites (see Locator Map, Figure 1.1).

log NTU = -0.46336 + 0.0012875 Dist. (m)

Analysis of Variance Statistics

R2 = 0.236467

P < 0.001

Dissolved oxygen (mg/l) = 7.2504491 - 0.0015501 Dist. (m)

Analysis of Variance Statistics

R2 = 0.343154

P < 0.001

4

5

6

7

8

9

100 300 500 700 900 1100 1300

A

C

B

D

E

F

G

H

I

J

Dissolved Oxygen (mg/l)

Distance to Bay Mouth (m)

Dissolved oxygen (mg/l) = 7.2504491 - 0.0015501 Dist. (m)

Analysis of Variance Statistics

R2 = 0.343154

p < 0.001
44

trends in dissolved oxygen (Marina), fecal 

coliform (Marina), turbidity (Marina, Bird 

Sanctuary), or salinity (Sugar Bay). Interestingly, 

there was a significant decline in turbidity at 

Sugar Bay during the period for which data 

area available between 1984 and 1994. The 

NTU values declined from ~7.5 to ~1.5, despite 

the loss of the mangroves surrounding this 

site after Hurricane Hugo in 1989. A reduction 

in freshwater runoff from Salt River Gut is a 

possible influence on this trend that could be 

investigated further. The growth of mangroves 

planted to reforest areas lost during Hurricane 

Hugo is expected to further improve water 

quality around this site.

The parameters with the highest 

variability were fecal coliform concentration 

values. Variations were large among stations 

and even among dates at the same station. 

Lowest values for fecal coliform were at the 

Columbus Landing and East Cove stations 

which are both close to the bay mouth and are 

presumably well flushed relative to sites farther 

inside the bays. High spikes in fecal coliform 

occurred at several stations. While none of the 

stations were listed by the DEP as “Impaired” 

for bacterial load, and mean fecal coliform levels 

were below that designated for Class B (not to 

exceed 70/100ml), spikes in fecal coliform above 

200 at several stations were not uncommon in 

the late 1980’s and mid 1990’s.

ECOLOGICAL LINKAGES

 Many of the human uses and virtually 

all ecological processes are dependent on 

maintaining good water quality in SARI. 

Practices that promote water quality should 

be supported, such as the recent restoration 

of the mangrove forest in Sugar Bay which 

was justified in part to enhance water quality. 

Mangrove prop roots trap and stabilize 

sediments thereby reducing turbidity in some 

parts of SARI. 

Poor flushing in the marina and 

inner reaches of the bays leave those areas 

particularly susceptible to low water quality and 

long residence time of pollutants once impaired. 

The presence and impact of toxins such as 

heavy metals in the water and sediments have 

been evaluated in the vicinity of the marina in 

the past but are not currently monitored.

REFERENCES

Division of Environmental Protection. 2002. The 

2002 integrated water quality monitoring 

and assessment report for the United 

States Virgin Islands. DEP/Department 

of Planning and Natural Resources/

Government of the US Virgin Islands. Pp. 

1-144

NOAA/Atlantic Oceanographic and 

Meteorological Laboratory. Coral Reef 

Early Warning System (CREWS) Station 

http://www.coral.noaa.gov/crews

NPS/Water Resources Division. 1999. Baseline 

water quality data inventory and analysis: 

Buck Island Reef National Monument, 

Christiansted National Historic Site, and 

Salt River Bay National Historic Park and 

Ecological Preserve. Technical Report 

NPS/NRWRD/NRTR-99/206. National 

Park Service, Water Management 

Division, Fort Collins, Colorado. Pp. 1-

623

STORET. United States/Environmental 

Protection Agency data storage and 

retrieval system for water quality 

monitoring data. Accessed Legacy and 

Modern databases June 2003. http://

www.epa.gov/storet/ 

Section 7 Water Quality
45
46

Section 8 Reef & Hardbottom

64°46'0"W

64°46'0"W

64°45'30"W

64°45'30"W

64°45'0"W

64°45'0"W

17°45'30"N

17°45'30"N

17°46'0"N

17°46'0"N

17°46'30"N

17°46'30"N

17°47'0"N

17°47'0"N

17°47'30"N

17°47'30"N

0 500 Meters

Reef

& Hardbottom

2000

Park Boundary

Classification

Coral Reef and Colonized Hardbottom,

Aggregated Patch Reefs

Coral Reef and Colonized Hardbottom,

Colonized Bedrock

Coral Reef and Colonized Hardbottom,

Colonized Pavement

Coral Reef and Colonized Hardbottom,

Colonized Pavement with Sand Channels

Coral Reef and Colonized Hardbottom,

Linear Reef

Coral Reef and Colonized Hardbottom,

Scattered Coral/Rock in Unconsolidated Sediment

Coral Reef and Colonized Hardbottom,

Spur and Groove

Uncolonized Hardbottom,

Reef Rubble

Uncolonized Hardbottom,

Uncolonized Bedrock

Uncolonized Hardbottom,

Uncolonized Pavement

Figure 8.1. Map of colonized and uncolonized hardbottom in SARI during 2000 
47

OVERVIEW

Over 116 hectares of reef and hard 

bottom were mapped within SARI for this 

assessment. This is an underestimate of the 

total area. The deep waters in the northern 

portion of SARI were mapped as ‘unknown’ 

because the extreme water depth precluded 

visual classification, but probably contain large 

areas of reef/hard bottom. Ten coral reef and 

hard bottom types were identified within SARI 

although additional types may occur in the 

deeper waters offshore. Virtually all field studies 

of SARI reefs have focused on the canyon 

walls, which were among the most studied reef 

systems in the world when the NOAA/NURP 

saturation diving facility was in operation at the 

site (1977-1989). Following Hurricane Hugo 

and the closing of these facilities, research on 

SARI reefs was virtually abandoned until 2001 

when monitoring projects were reinitiated at 

two sites by UVI and VIDPNR. Over nearly 

three decades of research, 41 species of corals 

and 86 species of sponges have been found 

in the canyon. Percent cover of live coral and 

other sessile organisms in the canyon varies 

by depth and position on the walls. In general, 

the west wall is steeper and has greater coral 

coverage than the east wall. Species richness 

and diversity of corals decrease with depth 

along both walls. Extensive reefs are a key 

component of the tropical marine ecosystem 

within SARI boundaries. These reefs provide 

habitat for a diverse assemblage of fish and 

invertebrates and form a physical barrier which 

insulates the backreef and bay areas of SARI 

from waves and storms. 

METHODS

 Previous studies characterizing the 

reefs within the SARI area were compiled 

and condensed into a general description. 

A wide variety of studies on reef ecology 

have been conducted within the submarine 

canyon at SARI, however, only those that 

are most applicable to the present ecological 

characterization are included here. Material that 

is more geological in nature is summarized in 

the Geology section. Area and location of the 

different reef types was summarized based on 

the 2000 aerial photographs and maps created 

with this assessment. All area estimates are 

based on two dimensional maps, resulting 

in an underestimation of the area of vertical 

features such as shelf edges and canyon walls. 

Calculation of percentages excludes the area of 

deep water labeled as ‘unknown’ in the northern 

portion of SARI.

RESULTS

 Total coral reef and hard bottom area 

within SARI mapped in this assessment was 

116.3 hectares (Figure 8.1). This excludes the 

area of artificially constructed rock breakwaters 

and armored shorelines within the bay. This is 

an underestimate of the total hard bottom area 

within SARI since the aerial photos only allowed 

mapping to a depth of approximately 25 m and 

there are known reef habitats in the canyon 

and at the shelf edge within SARI that are 

deeper than this limit. Nearly 70% of the hard 

bottom within SARI was classified as colonized 

pavement. Area, number of polygons, and the 

percentage of the total hard bottom for each reef 

classification are presented in Table 8.1. 

 Despite comprising only ~3 hectares or 

less than 3% of the total hard bottom area within 

SARI, virtually all previous studies characterizing 

coral reefs in the park were conducted on 

the walls of the Salt River submarine canyon. 

These studies were typically associated with 

the NOAA/NURP saturation diving facility 

located at the head of the canyon, which offered 

excellent access to these habitats until it was 

closed following Hurricane Hugo in 1989. The 

studies examined many sections of the canyon 

walls using various survey methods, rarely at 

the same exact location, using inconsistent 

methods, and often resulting in widely different 

conclusions for the same general area. Virtually 

no studies have been conducted on reefs within 

SARI outside of the canyon. As a result, the 

Section 8 Reef & Hardbottom

Section 8 Reef & Hardbottom
48

following characterization is biased strongly 

toward describing only the canyon walls prior to 

Hurricane Hugo.

 The east and west walls of Salt 

River submarine canyon have quite different 

morphologies and distributions of sessile 

biota. A total of 41 species of corals have been 

observed during studies in the canyon, 33 on the 

east wall and 38 on the west wall. An inventory 

of the coral species found during previous 

research and monitoring activities in the canyon 

is provided in Appendix B. 

 The southern half of the east wall is 

gently sloping with an unconsolidated cobble/

boulder substrate. Percent cover of live coral 

in this area is relatively low, ranging from 0 to 

7% (Boulon, 1978; Rogers et al. 1984). Farther 

toward the north, the wall becomes steeper, the 

substrate more solidified, and percent cover 

of live coral increases. At depths between 

10 and 18 m, live coral cover is usually less 

than 10% and is dominated by Diploria and 

Montastrea species. Continuing northward 

along the east wall where depths reach between 

19 and 21 m, live coral cover is higher, typically 

between 10 and 70% and is dominated by 

Montastrea cavernosa and Agaricia species. 

A depth of 18 m appears to have an optimal 

combination of light intensity, grazing pressure, 

and sedimentation rates for coral recruitment 

and survival on the east wall. Algal biomass was 

high at 9 m on the east wall (25 +/ -20 g/m2) 

relative to other sites in the canyon (Rogers et 

al. 1984). 

 In contrast, the entire west wall is very 

steep and composed of solid substrate which 

forms overhanging cliffs separated by sedimentfilled cuts that extend from the top of the wall 

to the canyon floor. Live coral cover along 

the west wall is typically between 20 and 60% 

(Boulon, 1978; Rogers et al., 1983; Rogers 

et al., 1984). The dominant species include 

Porites species, Montastraea cavernosa, 

Madracis decactis, and Agaricia species, with 

the latter being most dominant offshore and 

with increasing depth (Boulon 1978; Rogers et 

al. 1983). A depth of 9 m appears optimal for 

coral recruitment and survival on the west wall. 

Algal biomass was low at 9 m on the west wall 

(5 +/- 4 g/m2) relative to other sites in the canyon 

(Rogers et al. 1984). 

 The west wall also contains numerous 

overhangs and caves, home to a diverse 

assemblage of sessile organisms including 

sponges, corals, bivalves, brachiopods, 

bryozoans, and serpulid worms. The abundant 

Section 8 Reef & Hardbottom

Coral Reef or Hardbottom Type Number of 

Polygons 

Area 

(Hectares) 

Percent of 

Total Reef 

Area 

Aggregated Patch Reefs 2 0.3 <1 

Colonized Bedrock 2 1.3 1

Colonized Pavement 5 80.7 69

Colonized Pavement with Sand Channels 3 6.7 6

Linear Reef 7 13.0 11

Reef Rubble 3 7.1 6

Scattered Coral/Rock in Unconsolidated Sediment 2 0.1 <1 

Spur and Groove 3 2.8 2

Uncolonized Bedrock 10 2.7 2

Uncolonized Pavement 2 1.7 1

TOTALS 39 116.3 100

Table 8.1. Area, number of polygons and percentage of total reef and hard bottom mapped during 

2000. 
49

cave habitat and its corresponding biotic 

assemblage is different from exposed portions 

of the wall and further enhances the overall 

biodiversity of SARI. The sessile biota of 

these habitats between 15 and 40 m were 

characterized in 1982 (Rasmussen 1983; 

Rasmussen and Brett 1985). Total area of 

cave substrate covered with sessile biota 

increased with depth from 43% at 15 m to ~80% 

at the deeper caves. Demosponges were the 

dominant taxa at all depths covering between 

30 and 54% of the substrate. Demosponges, 

ascidians, and sclerosponges all increased in 

coverage with depth. Diversity and richness 

levels were highest in caves at ~20 m and 

deeper. 

 Despite the differences mentioned 

above, the east and west walls also share 

several characteristics. Recruitment of corals 

is roughly even between the two walls, and 

tends to be associated with areas of low algal 

biomass and relatively high densities of urchins 

and fish (Rogers et al. 1984). Dead coral cover 

is highest at 9 m on both walls often exceeding 

70% of the bottom, and is typically between 50 

and 60% at other depths. Agaricia lamarki

dominates deeper portions of both walls 

between 27 and 37 m. Cover of live coral at 

a depth of 37 m is lower than many shallower 

areas, generally below 10%. Species richness, 

evenness, and diversity of corals also decreases 

with depth along both walls (Rogers et al. 1984) 

although the east wall of the canyon is more 

diverse than the west wall at comparable depths 

(Coulston et al. 1990). Diadema antillarum

density was highest in shallow areas (2.6 ind./m2 

at 9 m on the west wall) and decreased to 0 

individuals at 37 m on both walls (Rogers et al. 

1984). 

 Sponges are another important 

component of the sessile biota of SARI coral 

reef environments. The distribution of sponges 

at three sites, one on the west wall at 18 m 

and two on the east wall at 18 and 24 m, were 

assessed in 1983 (Targett and Schmahl 1984). 

Despite having different bottom characteristics 

and corresponding coral communities, the east 

and west canyon walls had similar abundance 

and types of sponges at the sites examined. 

Eighty-six species of sponges were found. 

All three sites had similar density and area 

coverage of sponges. Density was between 

16 and 20 individuals per m2. Coverage was 

typically between 20 and 30% of the substrate 

but was quite variable. No single species 

dominated the assemblage at any site. 

 Hurricane Hugo had a significant 

and easily measurable effect on some SARI 

features such as the mangroves in Sugar Bay 

(See Mangroves, Section 10) and the volume 

of sediment on the canyon floor (see Geology, 

Section 4). In contrast, overall changes to 

the coral coverage due to the storm were 

characterized as “minor” in a post-storm 

assessment, with most species losing only 2 

to 14% coverage (Kesling 1990). Exceptions 

were Dichocoenia stokesi (81% loss, although 

this species was never abundant and limited to 

only shallow portions of the west wall prior to 

the storm), Diploria clivosa (28%), Colpophyllia 

natans (24%) (Kesling, 1990) and the complete 

devastation of an Acropora cervicornis patch 

(100%) (Coulston et al. 1990). Coral damage 

was patchy and mostly occurred along the 

east wall and shallow portions of the west wall. 

Sponges and gorgonians were more affected 

by the storm. Sponges decreased by 13% 

and gorgonians by 28% overall (Kesling 1990). 

Where living components of the reef were lost, 

they were replaced by bare rubble, sand, and 

algae-covered coral rubble. Monitoring data for 

the west wall at Salt River collected before and 

after Hurricane Allen in 1980 resulted in fewer 

significant changes in benthic cover (Rogers et 

al. 1983). In contrast, qualitative assessments 

indicate that extensive changes in benthic 

cover can be observed following such storms 

(Coulston et al. 1990). The techniques used to 

quantify changes have generally not supported 

such qualitative observations and probably need 

to be modified to improve sensitivity (Coulston et 

al. 1990) or confidence in the results. 

 In 2001, a new monitoring program using 

video transects was initiated with the objective 

of tracking changes in benthic cover at reef sites 

around St. Croix (Nemeth et al. 2003). The 

program includes one site each on the west (6 

m deep) and east (12 m deep) canyon walls 

Section 8 Reef & Hardbottom
50

at Salt River. The data allow comparison with 

other reef sites around St. Croix. Fish are also 

surveyed regularly at these sites by the Division 

of Fish and Wildlife, VIDPNR, as part of a coral 

reef monitoring program (see Fish, Section 

11). At the time this report was written, only 

the 2002 data and report were available and 

therefore discussion of the findings is limited. 

The real value of this activity is not the data in 

this first report, rather it will come from the long 

term dataset generated by continued semiannual monitoring. A total of 24 surveys were 

conducted in 2001 and 2002, six each on the 

east and west walls per year. Coverage of live 

coral (~10%), dead coral with turf algae (70-

80%), macroalgae (~5%), and sponges (~4%) 

were so similar between the two walls that the 

investigators recommend surveying only one of 

these sites in future monitoring. Coral bleaching 

was observed on 7-13% of colonies. Disease 

was observed on 2% of east wall colonies and 

17% of west wall colonies.

ECOLOGICAL LINKAGES

 Sedimentation is a major control on 

reef characteristics at SARI (see Geology, 

Section 4). Transport of shelf sediments and 

the potential mobility of the unconsolidated 

substrate on the southern portion of the eastern 

canyon wall during storms (Boulon 1978) serve 

to limit coral growth in that area. Apart from the 

canyon, other key reef features are the linear 

reefs, which form a physical barrier at the mouth 

of the bays. This barrier insulates seagrass, 

algae, and mangrove areas within the bays from 

potentially destructive wave energy. These 

habitats in turn insulate the reef from terrestrially 

borne sediments and runoff. The combination 

of reefs, mangroves, and seagrass beds within 

SARI provide an excellent combination of habitat 

types for a wide variety of aquatic organisms 

(see Fish, Section 11). 

REFERENCES

Boulon, R.H. 1978. Coral distributions in the Salt 

River Submarine Canyon, St. Croix, US 

Virgin Islands. Final Scientific Report 

NOAA Hydrolab; Mission 78-6B. Pp. 1-18

Coulston, M.L., M. Taylor, and C.A. Kesling. 

1990. Environmental Monitoring in the 

Salt River Submarine Canyon , St. Croix, 

Virgin Islands. Final Scientific Report 

NOAA Aquarius; Mission 89-3. 

Kesling, C.A. 1990. Preliminary report: Effects 

of Hurricane Hugo on the benthic coral 

reef community of Salt River Submarine 

Canyon, St. Croix, US Virgin Islands. 

Final Scientific Report NOAA Aquarius; 

Mission 89-4C Pp. 1-20 and in Diving 

for Science; Proc. Of the 10th Annual 

American Academy of Underwater 

Sciences Diving Symposium. Japp, W., 

St. Petersburg, Fl. 

Nemeth, R.S., S. Herzlied, M. Taylor, S. Harold, 

and W. Toller. 2003. Video monitoring 

assessment of coral reefs in St. Croix, 

United States Virgin Islands. Year two 

final report to VI Department of Planning 

and Natural Resources. Pp. 1-9 and 

Appendices.

Rasmussen, K.A. 1983. An ecologic and 

taphonomic analysis of submarine cave 

communities: Salt River Canyon, St. 

Croix, U.S.V.I. Masters Thesis. University 

of Rochester. Rochester, New York. Pp. 

1-148.

Rasmussen, K.A., and C.E. Brett. 1985. 

Taphonomy of Holocene cryptic biotas 

from St. Croix, Virgin Islands: Information 

loss and preservational biases. Geology

13:551-553

Rogers, C.S., M. Gilnak, and H.C. Fitz III. 1983. 

Monitoring of coral reefs with linear 

transects: A study of storm damage. 

Journal of Experimental Marine Biology 

Section 8 Reef & Hardbottom
51

Section 8 Reef & Hardbottom

and Ecology 66:285-300

Rogers, C.S., H.C. Fitz III, M. Gilnack, J. Beets, 

and J. Hardin. 1984. Scleractinian 

coral recruitment patterns at Salt River 

Submarine Canyon, St. Croix, US Virgin 

Islands. Coral Reefs 3:69-76

Targett, N.M., and G.P. Schmahl. 1984. 

Chemical ecology and distribution of 

sponges in the Salt River Canyon, 

St. Croix, USVI. NOAA Technical 

Memorandum OAR NURP-1. Pp. 12-30
52

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Seagrass

2000

Park Boundary

Classification

Seagrass, Continuous -

90% to 100% cover

Seagrass, Patchy (Discontinuous) -

10% to less than 50% cover

Seagrass, Patchy (Discontinuous) -

50% to less than 90% cover

Section 8 Reef & Hardbottom

Figure 9.1. Map of seagrass distributions in SARI in 2000.
53

OVERVIEW

 The seagrass and algal communities of 

Salt River Canyon are among the better studied 

components of the SARI ecosystem as several 

NOAA/NURP Hydrolab/Aquarius missions 

during the 1980’s were dedicated, at least 

partly, to those bottom types. The distribution 

of seagrass in the canyon was mapped at that 

time; however, the changes in distribution and 

present extent cannot be determined from 

aerial photos due to the depth of the canyon 

floor. Only algae and the seagrass Halophila 

decipiens are found growing on the canyon 

floor. Coverage there is seasonal with a 

peak during summer months. In contrast, the 

seagrass and algal communities of Salt River 

Bay have not received much in situ attention 

in the past, although their historical extent can 

be mapped using aerial photographs. Over 

the last three decades the seagrass areas 

of SARI have experienced major changes in 

distribution with a decline in total area. The 

most dramatic changes in coverage occurred 

behind the fringing reef west of the entrance to 

Salt River Bay. The area of seagrass present 

in the bays in 1970’s covered 24.6 hectares. 

By 1988, a year prior to Hurricane Hugo, the 

area of seagrass remained relatively stable at 

24.2 hectares. Three years after the passage 

of Hugo, the 1992 aerial photos indicated that 

coverage of seagrass was reduced by 12% to 

21.3 hectares within the bays with most loss 

occurring in the western back reef area. By 

2000, this coverage had changed little extending 

over 21.6 hectares. 

METHODS

 

 Extent of seagrass was digitized 

from orthorectified aerial photos acquired 

in the 1970’s, 1988, 1992, and 2000. 

Submerged vegetation was mapped using 

a hierarchical classification scheme with 

attributes discriminating between seagrass and 

macroalgae, and degree of patchiness. The 

minimum mapping unit, scale of digitizing, 

and other details of the mapping process are 

described in Section 2, Aerial Photographs and 

Mapping Methods. Overall extent of seagrass 

in Salt River Bay from historical imagery (1970s, 

1988, and 1992) was estimated using the 

simplifying assumption that actual seagrass 

coverage within patchy categories is at the 

mid point of each patchiness range. Seagrass 

coverage in the bay for each year was therefore 

calculated as:

 Unfortunately, no historical changes 

in vegetation distribution on the floor of Salt 

River Canyon could be determined from aerial 

photographs due to the depth of the canyon 

floor and difficulty determining meadow 

boundaries for sparse Halophila decipiens beds 

in water 30 feet deep. As a result, the canyon 

floor was mapped as sand. Therefore, the 

algae and seagrass in Salt River Canyon was 

characterized based on published reports from 

studies rather than maps. This literature was 

compiled from published literature and NOAA 

technical reports. 

RESULTS

 Seagrass coverage in Salt River Bay 

has declined slightly since the 1970’s (Figure 

9.1, Table 9.1). A 10-15% reduction in overall 

coverage from the 1970’s meadow extent 

occurred between 1988 and 1992, coincident 

with the passage of Hurricane Hugo. The 

majority of the loss in seagrass coverage 

occurred between Columbus Landing and 

the cut in the reef at the mouth of Salt River 

Bay. Seagrass coverage by 2000 was only 

slightly greater than that observed in 1992 and 

remained 13% below 1970’s coverage levels. 

 1.0(polygon area labeled Continuous Seagrass)

 0.3(polygon area labeled Patchy Seagrass 10% - 50%) 

+ 0.7(polygon area labeled Patchy Seagrass 50% - 90%)

 _____________________________________________

= Estimated total seagrass coverage 

Section 9 Seagrass & Algae

Section 9 Seagrass & Algae
Section 9 Seagrass & Algae

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Figure 9.2. Map of seagrass distributions in SARI by time period.

54

Section 9 Seagrass & Algae
55

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Seagrass2000

Park Boundary

Classification

Seagrass, Continuous -90% to 100% cover

Seagrass, Patchy (Discontinuous) -10% to less than 50% coverSeagrass, Patchy (Discontinuous) -50% to less than 90% cover

Section 9 Seagrass & Algae

Figure 9.2. Map of seagrass distributions in SARI by time period.
An important caveat in quantifying any changes 

in seagrass coverage among years is that 

turbidity levels were not consistent among the 

four time periods of aerial photography used to 

create the maps. This was particularly apparent 

in the 1970’s imagery which had higher turbidity 

levels in the southern portions of the bay than 

subsequent years. This limited the interpretation 

of submerged features in the southern and 

eastern portions of Salt River Bay and likely 

resulted in an underestimate of the seagrass 

coverage for this period. Most of the seagrass 

in the bays consists of two species, Thalassia 

testudinum and Syringodium filiforme, with 

lesser areas of Halodule wrightii. 

 Seagrass and algae in Salt River 

Canyon were studied intensively by several 

investigators between 1980 and 1989 on 

saturation dives using NOAA’s Hydrolab. 

Halophila decipiens, seagrass detritus, and 

macroalgae were reported to be the major 

sources of primary production, organic matter, 

and vegetated habitat in Salt River Canyon. 

H.decipiens is the only seagrass that has been 

observed naturally growing on the canyon 

floor where it is the dominant macrophyte 

during summer. The canyon floor is below the 

depth/light limit for other Caribbean seagrass 

species. Presence of H.decipiens is seasonal. 

There is a fall/winter decline in coverage due 

to disturbance by cyclonic storms in the fall, 

lower irradiance levels associated with winter, 

and large swells characteristic of winter weather 

patterns which can disturb the sediment to a 

depth of 30 m (Williams 1988). For example, 

as a result of Tropical Storm Klaus (1984), 

Halimeda incressata declined to 58% of its 

density of the previous summer and 99% of 

H.decipiens and Caulerpa sp. were eliminated 

between 15 and 23 m. There is sufficient light 

for growth of H.decipiens only from April to 

August. A study in May, 1985, estimated that 

H.decipiens covered 37% of the canyon floor 

between depths of 14 and 32 m (Kenworthy et 

al 1989). Overall upper and lower depth limits 

of this species are approximately 8 and 40 m 

during summer months in Salt River Canyon. 

Measurements of biomass during summer range 

between 5-12 g dry weight per m2 depending on 

year and depth. 

 Josselyn et al. (1983) studied 

composition and movements of the large 

amount of drift vegetation found in Salt River 

Canyon. Seagrass blades dominated the 

drifting vegetation. Thalassia testudinum

and Syringodium filiforme were in the drift 

year round, whereas Halodule wrightii and 

H.decipiens were found only during the summer 

mission. Except for the H.decipiens, Salt 

River Bay is the primary source of this drifting 

vegetation. Residence time in the canyon for 

drift vegetation was highly variable, ranging 

from less than a day during storm conditions 

to several weeks during periods of calm. Net 

movement of the material is down canyon. 

Section 9 Seagrass & Algae

Table 9.1. Area of seagrass polygons, and estimated overall seagrass area by map classification and period of 

photography. Overall seagrass area was calculated by assuming that actual coverage of patchy categories was at the 

midpoint of each patchyness range.

1970 1988 1992 2000 

polygon seagrass polygon seagrass polygon seagrass polygon seagrass 

Continuous Seagrass 12.9 12.9 13.9 13.9 10.4 10.4 12.7 12.7

Patchy 50-90% Seagrass 13.0 9.1 12.2 8.5 12.9 9.0 9.5 6.7

Patchy 10-50% Seagrass 8.9 2.7 5.9 1.8 6.2 1.9 7.3 2.2

total seagrass coverage 24.6 24.2 21.3 21.6

% of 70's seagrass extent n/a 98% 86% 87%

56

Section 8 Reef & Hardbottom
57

ECOLOGICAL LINKAGES

 Salt River Canyon provides an ecological 

connection between Salt River Bay and the 

deep sea communities north of St. Croix. The 

dominant trade winds from the northeast push 

water along the surface over the reef crest into 

the bay. Water and the vegetation from within 

the bays which is carried with it, must then exit 

through the open channel at the head of Salt 

River Canyon (Josselyn et al 1983). Energy, 

in the form of high seagrass productivity in the 

shallow areas of the bay, is then funneled rapidly 

down canyon by currents and is made available 

to deep sea ecosystems (see Currents, Section 

6). During summer months H.decipiens is 

one of the major sources of organic matter to 

the depths below 30 m (Josselyn et al 1986). 

Observations from a submersible revealed a 

large amount of detrital seagrass deposited in 

the ~3000 m depths off the canyon (Suchanek 

et al 1985). 

 Water quality in the bays may affect 

production of seagrass in the canyon (see Water 

Quality, Section 7). The solar irradiance that 

drives primary production on the canyon floor is 

influenced by weather and discharge from Salt 

River Bay. When strong onshore winds occur, 

bottom currents carry turbid water from the bay, 

through the channel in the fringing reef, and into 

the head of Salt River Canyon. Turbid waters 

are then diluted and cleared as they mix with 

clear offshore water farther down the canyon. 

Even though it is deeper in the middle of the 

canyon, the irradiance can be higher there than 

in the shallower head of the canyon due to this 

discharge of turbid water (Josselyn et al 1986). 

 The role that seagrass plays in stabilizing 

coastal sediments is well documented. 

Terrestrial runoff from the Salt River watershed 

flows across seagrass beds before exiting Salt 

River Bay. The seagrass beds trap some of 

these terrestrial sediments thereby partially 

protecting the coral reefs further offshore from 

the harmful effects of sedimentation. 

 The seagrass, algal beds, and 

associated epiphytes in both the canyon and 

bay are utilized by a diverse assemblage of 

organisms. Dozens of fish and invertebrate 

species utilize algae and seagrass as a direct 

or indirect source of food or as structural shelter 

during some stage of their life history (see Fish, 

Section 11). The seagrass meadows of SARI 

represent the only large patch of this bottom 

type along the northwestern third of St. Croix. 

REFERENCES

Josselyn, M.N., G.M. Cailliet, T.M. Niesen, R. 

Cowen, A.C. Hurley, J. Connor, and S. 

Hawes. 1983. Composition, Export and 

Faunal Utilization of Drift Vegetation 

in the Salt River Submarine Canyon. 

Estuarine, Coastal and Shelf Science

17:447-465

Josselyn, M., M. Fonseca, T. Niesen, and R. 

Larson. 1986. Biomass, production and 

decomposition of a deep water seagrass, 

Halophila decipiens Ostenf. Aquatic 

Botany 25:47-61

Kenworthy, W.J., C.A. Currin, M.S. Fonseca, 

and G. Smith. 1989. Production, 

decomposition, and heterotrophic 

utilization of the seagrass Halophila 

decipiens in a submarine canyon. 

Marine Ecology Progress Series 51:277-

290

Suchanek, T.H., S.L. Williams, J.C. Ogden, D.K. 

Hubbard, and I.P. Gill. 1985. Utilization 

of shallow-water seagrass detritus by 

Caribbean deep-sea macrofauna: δ13C 

evidence. Deep Sea Research 32:201-

214

Williams, S.L., V.A. Breda, T.W. Anderson, 

and B.B. Nyden. 1985. Growth and 

sediment disturbances of Caulerpa spp. 

(Chlorophyta) in a submarine canyon. 

Marine Ecology Progress Series 21:275-

281

Williams, S.L. 1988. Disturbance and recovery 

of a deep-water Caribbean seagrass 

bed. Marine Ecology Progress Series 

Section 9 Seagrass & Algae
42:63-71

58

Section 9 Seagrass & Algae
59
60

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Mangroves

2000

Park Boundary

Classification

Mangrove, Avicennia germanis,

Closed - >65% canopy cover

Mangrove, Avicennia germanis,

Open - 15%-65% canopy coverage

Mangrove, Avicennia germanis,

Sparse - 1%-15% canopy coverage

Mangrove, Dead

Mangrove, Laguncularia racemosa,

Closed - >65% canopy cover

Mangrove, Laguncularia racemosa,

Open - 15%-65% canopy coverage

Mangrove, Laguncularia racemosa,

Sparse - 1%-15% canopy coverage

Mangrove, Mixed,

Closed - >65% canopy cover

Mangrove, Mixed,

Open - 15%-65% canopy coverage

Mangrove, Mixed,

Sparse - 1%-15% canopy coverage

Mangrove, Rhizophora mangle,

Closed - >65% canopy cover

Mangrove, Rhizophora mangle,

Open - 15%-65% canopy coverage

Mangrove, Rhizophora mangle,

Sparse - 1%-15% canopy coverage

Section 10 Mangroves

Figure 10.1. Map of mangrove distributions in SARI in 2000.
61

OVERVIEW

The mangrove forests of SARI Bay were 

once considered the finest in the US Virgin 

Islands. However, over the last three decades 

these forests have experienced among the most 

dramatic changes of any terrestrial or benthic 

feature in St. Croix. Major losses in mangrove 

cover occurred primarily due to the devastating 

winds associated with Hurricane Hugo in 1989. 

Specifically, the area of mangrove forest present 

in 1970’s photography covered 20.2 hectares 

and by 1988, a year prior to the devastation 

caused by Hugo, the area of this forest had 

increased to the maximum extent observed in 

this assessment, covering 22.2 hectares. Most 

of the mangroves prior to the storm occurred 

in mature, closed canopy forests from ~4 to 

6 m tall. Three years after the passage of 

Hugo, the 1992 aerial photos indicated that 

12 hectares of mangrove forest were dead 

with most remaining live mangrove canopies 

reduced to open or sparse coverage. Live 

mangroves in 1992 covered only 43% of their 

1988 extent. Since 1992, gains in mangrove 

habitat have occurred as a result of both natural 

growth as well as a restoration project by the 

St. Croix Environmental Association which was 

initiated in 1999. As a result of the restoration 

effort, 1.4 hectares of the lost mangrove forest, 

primarily on the western side of Sugar Bay, have 

been replanted. Survival rate for restoration 

seedlings is estimated at 80%. Natural regrowth accounts for 0.9 hectares of forest since 

1992. The most recent aerial photos of this 

area (2000) indicate that naturally occurring and 

restoration mangroves now cover 12 hectares or 

54% of the extent of the 1988 forest. 

METHODS

Extent of mangrove forests was digitized from 

orthorectified aerial photos acquired in the 

1970s, 1988, 1992, and 2000 (Figure 10.1). 

Mangroves were mapped using a hierarchical 

classification scheme with attributes defining 

species and canopy density. Canopy density 

categories where based on the Florida Land 

Use and Land Cover Classification scheme 

(Smith 1992). Closed was defined as having 

a canopy that obscured more than 65% of the 

ground, typically with tree crowns interlocking, 

touching or very slightly separated. Open was 

defined as having a canopy that obscured 15-

65% of the ground, with crowns not typically 

interlocking. Sparse was defined as having 

a canopy that obscures only 1-15% of the 

ground. The minimum mapping unit and scale 

of digitizing were consistent with that described 

in the general mapping section. Identification 

of the extent of different mangrove species from 

historical imagery (1970s, 1988, and 1992) 

was guided by an early map of the forest (NPS 

Lands Office), several narrative accounts (e.g. 

Knowles 1993), and by matching tone and 

texture signatures visible in the 2000 imagery for 

each species which were visited in the field. 

Apart from two 100 m test plots, 

mangrove restoration activities were conducted 

between 1999 and 2001. Each year, thousands 

of red mangrove propagules were planted in 

three large rectangular plots on the western side 

of Sugar Bay. In addition to those large plots, 

a fringe planting of propagules was conducted 

along much of the eastern shore of Sugar 

Figure 10.2. Restoration planted red mangrove 

seedling.

Section 10 Mangroves

Section 10 Mangroves
62

Section 10 Mangroves 64°46'30"W

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Figure 10.2. Map of mangrove distributions in SARI by time period.
63

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Park Boundary

Classification

Mangrove, Avicennia germanis,Closed - >65% canopy cover

Mangrove, Avicennia germanis,Open - 15%-65% canopy coverageMangrove, Avicennia germanis,Sparse - 1%-15% canopy coverageMangrove, Dead

Mangrove, Laguncularia racemosa,Closed - >65% canopy cover

Mangrove, Laguncularia racemosa,Open - 15%-65% canopy coverageMangrove, Laguncularia racemosa,Sparse - 1%-15% canopy coverage

Mangrove, Mixed,Closed - >65% canopy cover

Mangrove, Mixed,Open - 15%-65% canopy coverageMangrove, Mixed,Sparse - 1%-15% canopy coverage

Mangrove, Rhizophora mangle,Closed - >65% canopy cover

Mangrove, Rhizophora mangle,Open - 15%-65% canopy coverageMangrove, Rhizophora mangle,Sparse - 1%-15% canopy coverage

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9

2

Figure 10.2. Map of mangrove distributions in SARI by time period.

Section 10 Mangroves
64

Section 10 Mangroves

0 100 Meters

Mangrove

Restoration

1997 R. mangle test plot

1999 R. mangle planting

2000 R. mangle planting

2001 R. mangle 2 row planting

2001 R. mangle 4 row planting

2001 R. mangle planting

A. germanis plot

Sugar

Bay

Figure 10.3. Map of St. Croix Environmental Association (SEA) mangrove restoration plots.
65

Bay. A small zone of black mangroves was 

also planted in 2001 although <1% survived 

long term. Detailed methods of restoration 

activities are available in Riley and Kent 

1999 and SEA 2004. Restoration mangroves 

were not visible in the 2000 imagery due to 

the small size of individual seedlings. These 

plots were therefore delineated with the aid 

of GPS waypoints acquired by walking or 

kayaking around the perimeter of each plot. 

GPS positions were used as a guide to digitize 

the boundaries of the restoration areas and 

the results are presented on a separate map 

(Figure 10.3). 

Table 10.1. Estimated mangrove area for each map classification and time period of photography. 

Values are in m2

.

Section 10 Mangroves

Figure 10.4. Two rows of seedlings were planted along a 

portion of the eastern side of Sugar Bay. Remains of the 

mangroves killed by Hurricane Hugo lie landward of the 

seedlings.

Canopy 

Density 1970 1988 1992 2000 

Avicennia germanis Closed 82907 109043 551 29965 

Open 30801 31903 31068 18358 

Sparse 3153 967 24151 7453 

TOTAL 116861 141913 55770 55776 

Laguncularia racemosa Closed 0 645 0 0

Open 1320 437 854 6150 

Sparse 0 0 0 0

TOTAL 1320 1082 854 6150 

Rhizophora mangle Closed 73121 60614 2171 27620 

Open 4986 4309 18072 9288 

Sparse 932 0 8907 1157 

TOTAL 79039 64923 29150 38065 

Mixed mangrove forest Closed 4318 11780 0 383

 Open 421 2302 8346 5347 

 Sparse 0 0 2344 0

TOTAL 4739 14082 10690 5730 

TOTALS (natural) Closed 160346 182082 2722 57968 

Open 37528 38951 58340 39143 

Sparse 4085 967 35402 8610 

Dead (not in Total below) 1076 0 120188 80556 

Restoration (up to 2004) 0 0 0 13915 

TOTAL natural and restoration 201959 222000 96464 119636 

% of 1988 (max) total extent 91% 100% 43% 54%
RESULTS

 Changes in coverage for each species 

of mangrove are summarized by year in Table 

10.1. Total mangrove forest area during the 

time periods covered by this assessment ranged 

from a high of 22.2 hectares in 1988 to a low of 

9.6 hectares in 1992, a decline of 57%. Typical 

mangrove zonation patterns were observed 

in all years of imagery with red mangroves 

nearest the shoreline, white mangroves most 

inland, and black mangroves in between. In 

all years, black mangroves accounted for over 

half the total mangrove forest extent with red 

mangroves comprising another third of the total. 

Most of the remaining mangrove forest area was 

composed of a mixture of species. Only small 

areas were mapped as white mangroves in any 

year. This is at least partly due to the difficulties 

of discriminating between white mangroves 

and bordering upland coastal forests as these 

habitats rapidly transition on the steep slopes 

along this part of St.Croix’s coast. 

 In the 1970’s and in 1988 the forest was 

primarily classified as closed canopy (Figure 

10.5, Table 10.1). Three years after Hurricane 

Hugo, approximately half the total mangrove 

forest was mapped as dead, and most of the 

remaining half was categorized as open or 

sparse canopy. The total area classified as 

open and sparse in 1992 had by 2000 become 

classified as closed and open respectively, 

indicating a slow recovery of the forest injured 

during Hugo (Figure 10.5, Table 10.1). The total 

area mapped as dead in 1992 was still extensive 

by 2000 although some areas were recovering 

naturally and others becoming reestablished 

from the restoration project. 

ECOLOGICAL LINKAGES

 The role that mangroves play 

in stabilizing coastal sediments is well 

documented. This was cited as one of the 

principle justifications for the Sugar Bay 

mangrove restoration. The watershed’s main 

outlet from Salt River Gut into Sugar Bay flows 

through the center of the largest mangrove 

stand lost during Hurricane Hugo. The 

seagrass beds, coral reefs, and other benthic 

habitats on the insular shelf beyond this area 

benefit from a healthy mangrove forest which 

buffers the harmful effects of terrestrial runoff. 

 Mangroves also play a role in regulating 

water temperature on tidal flats. Before 

Hurricane Hugo defoliated and ultimately 

killed the extensive mangroves in Sugar and 

Triton Bays, the large tidal flats in those areas 

were insulated from intense sunlight. The 

0

5

10

15

20

25

1970 1988 1992 2000

Restoration

Dead

Sparse

Open

Closed

Area (hectares)

Hurricane

Hugo 1989

Restoration

Began 1999

Figure 10.5. Graph of mangrove cover by cover classification and time period.

66

Section 10 Mangroves
67

changes from a shaded, cool water community 

in the once living mangrove root system to 

the current sun-exposed community have not 

been quantified. As the restoration mangroves 

continue to grow and form interlocking canopies 

and root systems that shade the tidal flat, 

community structure and water quality will 

presumably return to pre-Hugo conditions.

 The physical structure provided by the 

mangroves is utilized by a diverse assemblage 

of terrestrial and aquatic organisms. Many 

bird species utilize the emergent portions for 

roosting and nesting (see Birds, Section 12). 

Dozens of fish species utilize the submerged 

portion of prop roots during some stage of 

their life history (see Fish, Section 11). A 

recent study by VIDPNR’s Division of Fish 

and Wildlife recommended the reforestation 

of hurricane damaged mangroves to enhance 

fish nursery habitat in the Salt River area 

(Tobias et al 1996). A tremendous diversity of 

algae, sponges, tunicates, mollusks, and other 

sessile invertebrates also utilize the mangrove 

prop roots as a settlement substrate. These 

encrusting organisms are then used as food 

and habitat by a diversity of other organisms. 

Excellent summaries of the ecological role of 

mangroves in coastal systems are given in 

Hogarth (1999) and Tomlinson (1986). The 

mangroves of SARI represent the only large 

patch of this forest type along the northwestern 

quarter of St.Croix. 

REFERENCES

Hogarth, P.J. 1999. The biology of mangroves. 

Oxford University Press Inc., New York, 

USA. 228 Pp. 

Land Use/Land Cover Classification Using 

Digitally Merged Spot Panchromatic 

and Landsat Thematic Mapper Imagery. 

Smith, S., and Brown, C. University of 

Florida, Department of Civil Engineering. 

NOAA, Washington D.C. 1992.

Riley, R. Jr., and C.S. Kent. 1999. Riley 

encased methodology: Principles and 

processes of mangrove habitat creation 

and restoration. Mangroves and Salt 

Marshes. 3:207-213.

St.Croix Environmental Association (SEA). 2004. 

Mangrove restoration at Salt River Bay, 

St.Croix. Prepared by Carol CramerBurke. Final report to non-point source 

management program. 2 Pp. 

Tobias, W.J. 1996. The determination of 

mangrove habitat for nursery ground 

of recreational fisheries in St.Croix. 

Government of the USVI, Departement 

of Planning and Natural Resources, Div. 

of Fish and Wildlife. Project F-7 1-30 Pp. 

Tomlinson, P.B. 1986. The botany of mangroves. 

Cambridge University Press, Cambridge, 

UK. 419 Pp.

Section 10 Mangroves
68

OVERVIEW

 SARI encompasses large areas of 

mangrove forest, seagrass meadows, and 

reefs within close proximity to each other. This 

variety of benthic habitats is required by many 

tropical marine fish to complete their life cycle 

(Christensen et al. 2003). Seagrass and sand 

areas are used by many larval fish as initial 

settlement sites when they transition from ocean 

drifting forms to bottom dwelling forms. The 

prop roots of red mangroves provide structural 

refuge and foraging habitat for juveniles of 

many species. A recent study at SARI found 

57 species of fish utilizing mangrove habitat 

(Adams and Tobias 1994). Numerous reef 

types such as the east and west walls of the 

canyon provide habitat for perhaps the largest 

diversity of adult and juvenile fish species. 

Nearly 200 species of fish have been observed 

on SARI reefs to date (Kaufman and Ebersole 

1984, Workman et al. 1985, Adams and Tobias 

1994, Tobias 2002), and this despite nearly 

all sampling effort expended only on the 

canyon walls. The park also includes a large 

area of shelf edge habitat and easy access to 

offshore waters. This connection to pelagic 

environments further enhances the biodiversity 

of fishes within SARI and the ecological linkages 

with the adjacent oceanic ecosystem.

METHODS

 Literature on the species and distribution 

of fish fauna within SARI were compiled for 

the bay, canyon/shelf, and pelagic areas. 

These sources often included species lists 

and discussion of the fish fauna’s association 

with specific habitats or bottom types and 

their relationship with the region’s ecology. 

Information in these published sources was 

combined and condensed into a generalized 

description of the ichthyofauna and their habitats 

at SARI. Appendix D lists the species observed 

on the most robust of these assessments. 

Distribution, area, and changes in key fish 

habitats are quantified based on the maps 

created for this assessment. 

RESULTS

 As with other resources in SARI, the 

studies of fish fauna can be divided into those 

focused outside the bays and those within. One 

study characterized the mangrove ichthyofauna 

for a period of several years after Hurricane 

Hugo. Several studies have been conducted 

on the fish communities occupying the east and 

west reef walls of the Salt River canyon. Two 

studies used fish attraction devices to at least 

partly examine pelagic species in the area.

 Red mangrove prop-roots provide 

structural refuge and foraging habitat for a 

diverse community of fish. This habitat was 

sampled monthly at SARI between 1990 and 

1993 using baited fish traps and visual transects 

(Adams and Tobias, 1994). Sites were spread 

around the Salt River Bay, Sugar Bay, and Triton 

Bay to cover a range of mangrove density, 

human impact, and turbidity levels. A total 

of 57 species were observed (Appendix D). 

Fish caught in traps included 40 species and 

19 families, and those observed on transects 

included 48 species and 26 families. Most 

abundant families were Lutjanidae, Haemulidae, 

and Gerreidae which together accounted for 

82% of the fish observed on transects and 

72% of fish caught in traps. Length frequency 

histograms indicate that most of the fish caught 

were juveniles. Species richness was greater 

close to the Bay mouth relative to sites farther 

in Triton and Sugar Bay. The study highlighted 

the importance of Salt River mangroves as a 

Section 11 Fish

Figure 11.1. Fish on a reef in Salt River National 

Historical Park and Ecological Preserve.

Section 11 Fish
69

nursery ground to many important recreational 

and commercial fish species, and emphasized 

that this habitat should be included in fisheries 

and habitat management plans. These 

data provide a useful reference dataset for 

comparison with future studies, particularly 

along the shoreline of the recent mangrove 

restoration in Sugar Bay (see Mangroves, 

Section 10). 

 The linear distance of tidal shoreline 

that is occupied by red mangroves should 

be monitored due to this habitat’s role as an 

ichthyofaunal nursery (Tobias1996). Total length 

of tidal mangrove shoreline in maps from the 

present assessment was approximately 4180, 

4625, 4420, and 4740 m based on 1970’s, 

1988, 1992, and 2000 imagery respectively. In 

1970’s and 1988 this length consisted entirely 

of live mangroves, whereas in 1992 and 2000 

significant portions consisted of dead trees 

due to Hurricane Hugo. In 1992, 2860 m was 

live and 1560 was dead. In 2000, 3610 m 

was live and 1130 was dead (see Mangroves, 

Section 10). The recently completed mangrove 

restoration in Sugar Bay has resulted in the 

successful establishment of seedlings over 

most of the shoreline formerly occupied by dead 

trees. As these trees grow and form interlocking 

root structures, an extensive habitat for juvenile 

fish will be restored.

 Studies of the fish outside the bay have 

primarily focused on the fish associated with 

the canyon walls (e.g. Bortone et al. 1978, 

Kaufman and Ebersole 1984). Kaufman and 

Ebersole (1984), based out of Hydrolab, used a 

timed-roving diver technique to census species 

along the east and west walls of the canyon at 

a depth of ~16 m. Species were categorized 

according to trophic group, coloration, and 

“defense mode”. During 16 censuses, a total 

of 108 species were recorded (Appendix D). 

Species richness was higher on the west wall 

(86 species total) than on the east wall (65 

species total). Species composition differed on 

the two walls, with 43 species found exclusively 

on the west wall and 22 species found only on 

the east. Trophic ratios were similar between 

the walls, the only difference being that there 

were more planktivores and fewer opportunistic 

feeders on the west wall compared to the east. 

More species employed the “seek shelter” mode 

of defense on the west wall whereas more 

fish on the east wall use the “run and dodge” 

mode. Differences in morphology of the west 

and east walls were used to explain much of 

the differences in distribution of trophic group, 

coloration, and defensive mode. The steeper 

drop off and higher density of hard corals and 

shelter resulted in more planktivores, shelter 

seeking species, and bold colored or barred 

fish on the west wall. The more gradual slope, 

lower density of hard corals and shelter sites 

on the east wall resulted in more species that 

are stripped and dodge and run as a means 

of predator avoidance. In separate studies, 

Rogers et al (1984) and Clavijo (1978) found 

that herbivorous fish declined in abundance 

along both walls with increasing depth. 

 Most recently, the VIDPNR Division 

of Fish and Wildlife (Toller 2002, Nemeth et 

al 2004) began monitoring programs using 

a variety of fish census techniques to survey 

fish communities around St.Croix including 

a site at the west canyon wall at SARI. The 

sites are also surveyed annually for benthic 

cover characteristics by the University of 

the Virgin Islands, Center for Marine and 

Environmental Studies, as part of a coral reef 

monitoring program (see Reef and Hardbottom, 

Section 8). While not intended to provide a 

comprehensive inventory of reef fish at SARI, 

the data allow comparison with several other 

reef sites around St.Croix. Point counts, belt 

transects, and roving diver surveys are all part 

of the monitoring program. At the time this 

report was written, only the 2002-2004 data 

and 2002-2003 reports (Toller 2002, Nemeth 

et al 2004) were available. The real value of 

this activity is not the data in these first years of 

monitoring, which have limited sample size, but 

instead will be the long term dataset generated 

by continued semiannual monitoring using 

multiple techniques. A total of 91 species have 

been observed in this program so far (Appendix 

D). A list of species observed, frequency 

of occurrence, abundance, and minimum/

maximum/average size are provided for each 

time period and census technique.

 In addition to these research and 

monitoring projects, the walls of Salt River 

Canyon are among the most popular 

Section 11 Fish
70

recreational dive areas in St.Croix with several 

mooring buoys providing easy access to both 

the east and west walls. A volunteer based 

organization, the Reef Environmental Education 

Foundation (REEF), organizes and trains 

recreational divers to conduct fish surveys using 

a random swim technique. To date, REEF 

divers have documented a total of 185 species 

in 69 hours of survey time on dives conducted 

on both walls of the canyon (Appendix D). 

While these data are collected by individuals 

with limited training in fish identification, the 

large number of visitors to SARI involved in 

this program make it an important and growing 

dataset. Caveats for data interpretation, a 

complete description of the survey method, and 

summary data are available at http://www.reef.

org/.

 Despite the large amount of effort spent 

monitoring the fish community on the canyon 

walls of SARI, this habitat composes only 3 

hectares or less than 3% of the total coral reef 

and hard bottom (two dimensional area) within 

SARI that was mapped in this assessment. This 

disproportionate survey effort is no doubt due 

to the access once afforded to these sites by 

NOAA/NURP’s saturation diving facilities within 

the canyon, the current placement of mooring 

buoys which maintain easy access to these 

sites, and the fact that the canyon walls are 

among the most impressive reefs on St. Croix. 

Other reef types within SARI have received 

almost no attention despite their much larger 

extent (113 hectares or 97% of the total reef/

hardbottom within SARI). 

 Pelagic fish have received less study but 

are a notable component of the fish assemblage 

of SARI due to its proximity to deep oceanic 

habitat. In fact, the deepest point within SARI 

is ~289 m, located along the steep, continuing 

drop off on the north side of St.Croix, making it 

likely that SARI is visited by a variety of open 

water species. Two studies using fish attraction 

devices (FADs) which tend to attract pelagic fish 

have been conducted in the area (Workman et 

al, 1985; Friedlander et al, 1994). One study 

which used hook and line to sample fish, most 

commonly caught 3 species: blackfin tuna 

(Thunnus atlanticus), little tunny (Euthynnus 

alletteratus), and dolphin (Coryphaena 

hippurus) which together accounted for 92% 

of the catch (Friedlander et al, 1994). Another 

study, which used FADs close to the reef and 

a variety of additional assessment techniques 

most frequently observed 3 different species: 

yellowtail snapper (Ocyurus chrysurus), creole 

wrasse (Clepticus parra), and mackerel scad 

(Decapterus macarellus) (Workman et al, 1985). 

Lack of controls, the biases associated with 

sampling pelagic fish, and the biases associated 

with the use of FADs limit the use of these 

studies as quantitative characterizations of 

the pelagic fish of SARI. Nevertheless, these 

studies document the presence of pelagic 

species in and around SARI. 

ECOLOGICAL LINKAGES

 A diverse assemblage of fish can find 

a suitable combination of habitats for larval 

settlement, juvenile growth, and adult life stages 

all within the relatively small boundaries of SARI. 

Inshore mangroves and seagrass beds provide 

an important nursery area for fish that ultimately 

migrate to the reefs outside the bay as adults. 

Seagrass beds enhance biodiversity of nearby 

reefs (Kendall 2003), and mangroves have been 

shown to enhance biomass of commercially 

important fish found on reefs nearby (Mumby 

et al, 2004). Mangroves, in particular have 

a limited distribution around St.Croix, with 

SARI containing one of the largest forests and 

mangrove shorelines on the island. This habitat 

may serve as an important nursery to juvenile 

fish that ultimately migrate to the reefs of SARI 

and elsewhere along the north shore of St.Croix.

 Pelagic fish are frequent visitors to 

the canyon and shelf edge reef and provide 

an ecological link with open ocean habitats. 

Fifty-five hectares of the area within the SARI 

boundary was too deep to be mapped using 

aerial photography. Depths increase rapidly 

northward of the SARI boundary as well. Salt 

River Canyon links into the nearby Christiansted 

Canyon and continues down the steep St.Croix 

insular shelf such that water depths exceed 

4000 m a mere 11 kilometers offshore from 

Section 11 Fish
71

Section 11 Fish

SARI. The frequency, duration, and ecological 

impact of SARI interactions with pelagic fish are 

poorly understood.

REFERENCES

Adams, A.J., and W.J. Tobias. 1994. Red 

mangrove prop-root habitat as finfish 

nursery area: a case study of Salt River 

Bay, St.Croix, USVI. Proceedings of the 

forty-sixth annual Gulf and Caribbean 

Fisheries Institute, Corpus Christi, USA. 

22-46 Pp.

Bortone, S.A., R.W. Hastings, and J.L. Oglesby. 

1978. Quantification of reef fish 

assemblages: a comparison of several 

in situ methods. NOAA Hydrolab Report, 

Mission NULS-1. 23 Pp. 

Christensen, J.D., C.F.G. Jeffrey, C. Caldow, 

M.E. Monaco, M.S. Kendall, and R.S. 

Appledorn. Cross-shelf habitat utilization 

patterns of reef fishes in southwestern 

Puerto Rico. Gulf and Caribbean 

Research. 14: 9-28.

Clavijo, I.E. 1978. Diel and depth variation in 

the population densities of herbivorous 

fishes on the walls in Salt River 

submarine canyon. Final Scientific 

Report; NOAA, Mission 78-3a

Tobias, W.J. 1996. The determination of 

mangrove habitat for nursery ground of 

recreational fisheries in St.Croix. 

Government of the USVI, Departement 

of Planning and Natural Resources, Div. 

of Fish and Wildlife. Project F-7 1-30 Pp. 

Friedlander, A., J, Beets, and W. Tobias. 1994. 

Effects of fish aggregating device design 

and location on fishing success in the 

US Virgin Islands. Bulletin of Marine 

Science. 55:592-601

Kaufman, L.S. and J.P. Ebersole. 1984. 

Microtopography and the organization of 

two assemblages of coral reef fishes in 

the West Indies. Journal of Experimental 

Marine Biology and Ecology. 78:253-268

Kendall, M.S. 2003. A method for investigating 

seascape ecology of reef fish. Gulf and 

Caribbean Fisheries Institute 

Mumby, P.J., and others. 2004. Mangroves 

enhance the biomass of coral reef fish 

communities in the Caribbean. Nature. 

427:533-536

Nemeth, R.S., S. Herzlieb, E.S. Kadison, M. 

Taylor, P. Rothenberger, S. Herold, and 

W. Toller. 2004. Coral reef monitoring in 

St. Croix and St. Thomas, United States 

Virgin Islands. Year three final report 

submitted to Department of Planning and 

Natural Resources. Center for Marine 

and Environmental Studies, University 

of the Virgin Islands and Division of Fish 

and Wildlife, DPNR. ~120 pp.

Rogers, C.S., H.C. Fitz III, M. Gilnack, J. Beets, 

and J. Hardin. 1984. Scleractinian 

coral recruitment patterns at Salt River 

Submarine Canyon, St.Croix, US Virgin 

Islands. Coral Reefs. 3:69-76

Workman, I.K., A.M. Landry Jr., J.W. Watson Jr., 

and J.W. Blackwell. 1985. A midwater 

fish attraction device study conducted 

from hydrolab. Bulletin of Marine 

Science. 37:377-386
72

OVERVIEW

 SARI is utilized by a diverse assemblage 

of birds including year round residents, 

overwintering residents, and species stopping 

briefly at St. Croix during annual migrations. 

An accounting of these species has been 

conducted several times in recent decades, both 

before and after Hurricane Hugo, and continues 

to be the subject of ongoing research. Results 

are not presented here since they are published 

elsewhere. The most recent bird survey data 

for the area was collected by Department of 

Planning and Natural Resources (VIDPNR), 

Division of Fish and Wildlife (DFW), however, 

these data were not available during preparation 

of this report. DFW should be contacted directly 

for these surveys and data interpretation. 

Instead of summarizing the various avifaunal 

reports as has been done elsewhere, and given 

that the most recent bird survey information are 

not yet widely available, the focus of this portion 

of the ecological assessment is on important 

bird habitats within SARI. Namely, there is a 

~200 m2 heron rookery within a large patch of 

red mangroves near the marina, a ~4000 m2

tern nesting beach west of Judith’s Fancy, two 

freshwater ponds, ~12 hectares of natural and 

restoration mangroves, ~1 hectare of sand and 

mud salt flat, ~1.3 hectares of sandy beach, and 

an additional ~2.4 hectares of other intertidal 

foraging habitats for wading and shore birds. A 

recent publication describing habitat preferences 

for Virgin Island avifauna (Rodriguez 2002) 

coupled with the land and marine habitat maps 

provided here allow quantification of important 

habitats on a species by species basis for SARI. 

METHODS

 Literature review, discussions with local 

experts, and field observations were used to 

identify key locations within SARI for roosting, 

nesting, and foraging activities of several 

avifauna species. Particular attention is given 

to mangrove habitats and shore birds due to 

recent changes in the extent of these habitats, 

and the high visibility of these birds within SARI. 

Literature reviews were narrowly focused on the 

habitat components of each study rather than on 

providing a thorough inventory of bird species, 

due to the unavailability of the most recent 

survey data.

 Nesting and roosting sites described in 

the literature were observed in the field, and the 

extent of those habitats was calculated based 

on the 2000 aerial photography. The area of 

intertidal foraging habitat for wading birds was 

estimated using the bathymetry model (see 

Bathymetry, Section 5). 

RESULTS

 The presence of avian bones in pre 

Columbian kitchen middens near Columbus 

Landing indicates that birds have been used by 

humans at SARI for centuries (Wetmore 1918). 

Interestingly, some of the bones present in the 

middens are from species not known to occur on 

St. Croix in present times. Whether these birds 

were captured locally and then extirpated or 

were captured elsewhere and then transported 

to SARI is not known. 

 Avifauna within portions of SARI, 

most notably the mangroves in Sugar 

Bay, have been studied intermittently by a 

number of researchers over the past several 

decades. Unfortunately, no consistent, longterm monitoring data are available for SARI 

Section 12 Birds

Figure 12.1. Pelicans roosting on dead mangrove 

stumps. 

Section 12 Birds
73

mangroves, and virtually no information is 

available for inland avifauna at SARI. Instead, a 

few brief studies, some prior to Hurricane Hugo, 

and several broad scale assessments of the bird 

communities of the entire Virgin Islands have 

been conducted with limited specific reference 

to the Salt River Bay area.

 Unfortunately, among the best avifauna 

information published in a peer reviewed journal 

for the area is based on surveys conducted 

prior to Hurricane Hugo in the formerly well 

developed mangrove forest of Sugar Bay 

(Wauer and Sladen, 1992). During the 12 

surveys conducted between October 1986 

and March 1987, 35 species were observed. 

Eight months after Hurricane Hugo, Wauer and 

Wunderle (1992) surveyed birds all over St. 

Croix and found no change in species richness, 

a minimal change in species composition, and 

a significant decline in average number of birds. 

Included in that study were before and after 

pictures taken at ground level of the damage 

to mangroves at Salt River, which illustrate the 

dramatic changes to that habitat. A quantitative 

examination of the impacts of the severe 

hurricane to these forests is included in the 

mangroves section of this report (Section 10).

 Another report based on information 

for Salt River prior to Hurricane Hugo lists the 

bay as a nesting site for the Yellow-crowned 

Night-Heron (Nyctanassa violacea), Green 

Heron (Butorides virescens), Little Blue Heron 

(Egretta caerulea), Yellow Warbler (Dendroica 

petechia), and White-crowned Pigeon (Columba 

leucocephala) among others (Scott and 

Carbonell eds., 1986). Prior to Hurricane Hugo, 

Sladen (1988) noted that 26 of the 44 bird 

species known to breed on St. Croix nest at Salt 

River. SARI is currently a feeding and roosting 

site for Osprey (Pandion haliaetus), Brown 

Pelican (Pelecanus occidentalis), at least five 

species of herons, and many shorebirds. Cattle 

Egrets (Bubulcus ibis) and Little Blue Herons 

currently nest in a ~200 m2 rookery within a 

much larger patch of red mangroves near Salt 

River Marina.

 The most extensive bird survey 

information available for SARI is based on Virgin 

Islands Department of Planning and Natural 

Resources (VIDPNR), Division of Fish and 

Wildlife (DFW) surveys conducted between 

April 1989 and September 1995 which appear 

in a report, Wildlife use of Saltwater Wetlands in 

the USVI, prepared by DFW (1993). Additional 

surveys have since been conducted and are the 

subject of a report in preparation by the DFW, 

comparing historical to more recent data. The 

DFW has also marked a tern nesting site which 

covers ~4000 m2 on the northeast side of SARI, 

west of Judith’s Fancy. The area is composed 

of rock, coral rubble, sand, and other dredge 

spoil. VIDPNR/DFW should be contacted for the 

most recent data, nesting activity, and reports in 

press. 

 Another source with some Salt River 

avifauna data is the US Virgin Islands Rapid 

Bird Assessment (Rodrigues, 2002). This report 

provides a good summary of historical bird 

information, some new survey data, a species 

by species accounting of bird status in the 

USVI and worldwide, specific birding records by 

location within the USVI, and a list of preferred 

habitats for each species. The information on 

habitat preference could be used in combination 

with the land cover maps presented in this report 

(Section 13, Land Cover, Soils and Land Use) to 

quantify potential habitat for each bird species 

occurring within SARI. 

ECOLOGICAL LINKAGES

 The mangrove habitat at SARI has been 

shown to be of critical importance to locally 

breeding/nesting birds as well as overwintering 

and migrating North American songbirds (Wauer 

and Sladen, 1992). In 1989, Hurricane Hugo 

profoundly changed the characteristics of this 

important bird habitat (see Mangroves, Section 

10). The restoration of Sugar Bay mangroves 

and gradual regrowth provides an opportunity 

for an interesting time series examining bird 

populations in a recovering mangrove forest. 

 The shallow mud, sand, and seagrass 

areas of Salt River provide a large foraging area 

for wading and shore birds. The size of this 

area is approximately 4.7 hectares. This was 

estimated as the combined area of the salt flats 

and beaches as delineated in the 2000 aerial 

Section 12 Birds
74

photography plus the intertidal zone as derived 

in the bathymetry section of this report.

REFERENCES

Knowles, W. 1993. Wildlife use of Saltwater 

wetlands on St. Croix. Annual narrative 

report for fiscal year 1993. U.S. Virgin 

Islands, Division of Fish and Wildlife. Pp. 

1-69

Rodriguez, A.S.L. 2002. U.S.Virgin Islands 

Rapid Bird Assessment. The Nature 

Conservancy. Pp. 1-114

Scott, D.A., and M. Carbonell (Eds). 1986. A 

Directory of Neotropical Wetlands. 

IUCN, Cambridge, and International 

Wildfowl and Wetlands Research 

Bureau. Pg. 588

Sladen, F.W. 1988. Salt River Bay and Environs: 

A Natural Resource Summary. Prepared 

for the Virgin Islands Natural Heritage 

Trust. St. Croix, Virgin Islands.

Wauer, R.H., and F.W. Sladen. 1992. Importance 

of Virgin Islands mangrove habitats to 

migrant and wintering birds. Ornitologia 

Neotropica???. 5:50-54

Wauer, R.H., and J.M. Wunderle Jr. 1992. 

The effect of Hurricane Hugo on bird 

populations on St. Croix, U.S. Virgin 

Islands. Wilson Bulletin. 104:656-673

Wetmore, A. 1918. Bones of birds collected by 

Theodoor de Booy from kitchen midden 

deposits in the Islands of St.Thomas 

and St. Croix. Proceedings of the U.S. 

National Museum. 54:513-522

Section 12 Birds
75
76

Section 13 Land Cover, Soils, & Land Use

64°46'30"W

64°46'30"W

64°46'0"W

64°46'0"W

64°45'30"W

64°45'30"W

64°45'0"W

64°45'0"W

17°45'30"N

17°45'30"N

17°46'0"N

17°46'0"N

17°46'30"N

17°46'30"N

17°47'0"N

17°47'0"N

17°47'30"N

17°47'30"N

0 500 Meters

Land Cover

2000

Park Boundary

Land Cover

Land, Bare Areas, 

Other

Land, Bare Areas, 

Rock

Land, Bare Areas, 

Sand/Beach

Land, Bare Areas, 

Soil

Developed, Commercial

Developed, Residential

Inland Water Bodies, 

Freshwater Pond

Inland Water Bodies, 

Saltwater Pond

Forest/Trees, Closed - 

>65% canopy coverage

Forest/Trees, Open - 

15%-65% canopy coverage

Forest/Trees, Sparse - 

1%-15% canopy coverage

Shrubs/Bushes, Closed - 

>65% canopy coverage

Shrubs/Bushes, Open - 

15%-65% canopy coverage

Shrubs/Bushes, Sparse - 

1%-15% canopy coverage

Vegetated Field

Roads, Paved

Roads, Unpaved

Figure 13.1. Map of land cover in SARI during 2000.
77

Section 13 Land Cover, Soils, & Land Use

OVERVIEW

The terrestrial environs within SARI were 

characterized based on aerial photographs, land 

cover maps produced in this assessment, and 

literature review. The park has been subject 

to notable human use, particularly dredging 

to enhance boat access, and commercial and 

residential construction. Dredging has altered 

the natural contours of the bays, and has as 

resulted in top soils containing salt where spoils 

have been deposited. However, although most 

parcels in the area are zoned for residential 

development or waterfront pleasure, only 7.3 

hectares out of approximately 145 hectares 

land area were classified as developed in 

2000. There is much visible evidence of past 

construction that in 2000 appears abandoned 

or incomplete. Topsoils consist primarily of 

loam of varying composition, and are not well 

suited for agriculture. The majority of terrestrial 

vegetation is forest of varying canopy cover (106 

hectares), with vegetated fields and shrubs/

bushes also covering notable extents (14 and 

11 hectares respectively). Eroded terrigenous 

soils dominated sediments in some areas of 

in the bays, demonstrating the influence that 

land activities can have on bay turbidity, reef 

development, and seagrass growth. In addition, 

periodic severe disturbance to forests and soils 

can be expected to occur in the hurricaneprone region, compounding existing human 

disturbance.

METHODS

Literature review and year 2000 

aerial photography were the primary sources 

of information for the characterization of 

vegetation, land use, and soils in SARI. 

Seventeen mutually exclusive land cover types 

were mapped (See Aerial Photographs and 

Mapping Methods, Section 2). Areas reported 

here for vegetation, bare areas, and land use 

categories were calculated using this map 

(Figure 13.1). Vegetation maps created from 

1995 aerial photographs and produced as part 

of the Rapid Ecological Assessment for St. 

Croix (University of the Virgin Islands 2000) 

were also referenced for this report. However, 

their maps and classification schemes were not 

incorporated directly, as the scope and scale 

of that effort differed from the intent of this 

characterization.

A large portion of the soil type 

descriptions included this report are based on a 

1998 U.S. Department of Agriculture, National 

Resources Conservation Service (USDA/NRCS) 

soil survey of the U.S. Virgin Islands (USDA/

NRCS 1998). Additional sources of newer 

terrestrial soil data are scant, and even relatively 

recent reports (1990’s) which contain regional 

descriptions mainly reference a previously 

conducted NRCS survey (Rivera et al. 1970). 

Additional information was obtained from field 

observations and literature review. Most reports 

were written during the mid 1990’s or earlier. 

Therefore, wherever possible, evidence of 

current (2000) use or persistence of the effects 

of past use were verified in year 2000 aerial 

photo mosaicks, and during 2004 field surveys.

As with soils and land use, 

supplementary information on vegetation was 

obtained from previously published surveys 

and reports. Plant species observed in other 

surveys within the park were compiled in 

Appendix C, though all are over ten years old 

and the park is in need of a comprehensive 

survey of current flora. In this section, only 

terrestrial vegetation is discussed, and 

mangroves were not included. For information 

on mangroves in SARI, see the Mangroves, 

section 10.

Figure 13.2. Salt River Bay from an upland forest 

overlook.

Section 13 Land Cover, Soils, & Land Use
78

RESULTS 

Of the non-aquatic areas, unvegetated 

soil covered the most area, approximately 2 

hectares. Sand/beach covered the second 

largest area, approximately 1 hectare, and 

bare rock covered 0.6 hectares (Table 13.1). 

Inland aquatic areas accounted for 2.5 

hectares, mostly from five saltwater ponds 

(2.4 hectares). At least two of the ponds are 

man made; one on the northeastern side of 

East Cove, and the Abandoned Marina Cut 

(Figure 1.1). A single freshwater pond was 

located on the southeastern side of Sugar Bay, 

covering approximately 0.1 hectares. A berm 

approximately 10 feet above sea level prevents 

seawater from entering this pond during high 

tides or even during moderate storm surge 

conditions. While seepage from Sugar Bay or 

the adjacent salt flat may effect salinity in this 

pond, it is not a typical salt pond as may be 

suspected by casual inspection of the aerial 

photographs.

There are a total of 11 NRCS soil types 

of varying grade (slope) within the park (USDA/

NRCS 1998) (Table 13.2.). The majority of top 

soils are approximately 0-9” deep, consisting 

of gravelly, sandy, stony, or clay loam. These 

include the Arawak, Cramer-Victory, Glynn, 

Solitude, and Victory-Southgate soil series (a 

family of soils with similar vertical structure, 

color, texture, composition and arrangement) 

and complexes (a mixture of two or more soil 

types that are either too intertwined or too 

patchy to map separately). Tidal areas around 

Sugar Bay and Triton Bay are flat (0-2% grade) 

sections of sandy clay loam and black muck 

(fine, well decomposed organic soil) from the 

Sandy Point/Sugar Beach series, and patches 

of gravelly fine sandy loam from the Solitude 

series. These are frequently flooded by the 

waters of the estuary, and typically contain 

some salt. The Salt River floodplain south 

of the Sugar Bay tidal region consists of clay 

loam from the Carib series, frequently flooded 

by freshwater from the upland watershed. 

Beaches are located on the northern facing 

shores, flanking the mouth of the bay. The 

eastern shore consists of fine sand formed from 

calcareous deposits, classified as the Jaucas 

series. The beach west of the mouth is also 

calcareous, but with a surface layer composed 

of large weathered coral pieces, characteristic 

of the Redhook series. A point that extends into 

the north western mouth of Triton Bay is also 

composed of Jaucas series sand. The majority 

of soils within the park are not well suited for 

crops (NPS 1990, USDA/NRCS 1998).

Dredge and fill activities have taken 

place since the 1960’s in various locations 

around the bays to create marinas and improve 

boat access. Although most projects were 

never completed, dredging resulted in dramatic 

alterations to the natural shape shoreline and 

bathymetry of the bays. Dredge disposal from 

these activities were deposited in several 

locations around the bay perimeter, creating new 

land and influencing soil characteristics. For 

instance, spoils have been deposited around the 

Section 13 Land Cover, Soils, & Land Use

Table 13.1. Estimated area of natural and semi-natural unvegetated map classifications for year 2000. 

Bare Areas

Inland Water Bodies

Total 62 6.5 100%

Category Classification Number of Total Area Percent

Polygons (hectares) of Total

Rock 7 0.5 8%

Sand/Beach 17 1.3 19%

Soil 32 2.1 33%

Freshwater Pond 1 0.1 2%

Saltwater Pond 5 2.4 38%
79

Dredged Basin, and the soil there has been 

reported to contain elevated amounts of salt 

(NPS 1990). Additional locations of dredge 

fill are: on the peninsula between East Cove 

and the Dredged Basin, on the peninsula west 

of the Abandoned Marina Cut, and east of the 

salt pond located west of Estate Judith’s Fancy. 

Along the western side of the bay extending 

from north of the Salt River Marina to just south 

of the Columbus Landing Site (Island Resources 

Foundation 1993) (Reference land marks on the 

“Locator Map”, Figure1.1). 

During land cover mapping, the 

only classification categories for human 

land use included roads (gravel and paved) 

and developed areas (commercial and 

residential). Of these, unpaved roads cover 

the most area, 2.9 hectares and are located 

primarily in the northwestern, central areas 

of the park, and around the dredged basin. 

Residentially developed areas accounted for 

approximately 1.7 hectares. Dwellings were 

scattered in the developments of Estate Salt 

River on the northwestern side of SARI, Estate 

Morningstar in the southwest quadrant, Estate 

Montpellier on the peninsula between Triton 

and Sugar Bay, and Estate Judith’s Fancy on 

the northeastern side of the park. Commercial 

development, consisting of the Salt River 

Marina and the uncompleted resort at Estate 

Judith’s Fancy, encompasses 1.4 hectares. 

Paved roads and account for approximately 

1.3 hectares, concentrated primarily along the 

western length of the park (Table 13.3).

 The bulk of the land within the 

boundaries of the park is zoned for low and 

medium density residential development, 

and for waterfront pleasure. Although large 

residentially zoned areas are owned by various 

corporations, most have not been developed. 

A handful of tracts show evidence of attempted 

development, but appear abandoned in 2000 

aerial photography. The largest and most 

Table 13.2. Soils found within SARI boundaries, summarized from the 1998 USDA/NRCS Soil Survey of the United 

States Virgin Islands.

Section 13 Land Cover, Soils, & Land Use

Soil Series Soil Description Total Area 

(hectares)

Arawak Gravelly loam, very stony 36.8

Carib Clay loam, frequently flooded. Slightly saline to non-saline 16.1

Cramer-Victory Complex Gravelly clay loam and loam (patchy) 33.9

Glynn Gravelly loam, rarely flooded 5.7

Jaucas Sand, on calcareous coastal beaches, rarely flooded 1.0

Pitts, Quarries Areas where rock, gravel or sand have been removed by 

humans 0.1

Redhook Extremely stony sand, rubbly, rarely flooded 2.3

Salt Flats Flooded, unvegetated areas of saline flats, saline marshes 

and salt ponds 0.7

Sandy Point and Sugar Beach Frequently flooded, sandy clay loam and black muck 

(patchy) 24.4

Solitude Gravelly fine sandy loam, frequently flooded. Slightly to 

strongly saline 15.2

Southgate-Rock Outcrop Complex Gravelly loam, extremely stony surface, exposed bedrock 0.5

Ustorthents Altered from natural state by human activity 7.6

Victory-Southgate Complex Very stony loam and gravelly loam (patchy) 20.7
80

conspicuous of these is an abandoned 

resort located in Estate Judith’s Fancy, on 

the peninsula between East Cove and the 

Dredged Basin. A number of hotel and marina 

developments have been attempted or proposed 

there, from the 1950's through the mid-1980's. 

(Island Resources Foundation 1993). Remnants 

of these efforts include the degrading remains of 

a hotel, a large pool, and several small cement 

pads scattered over the peninsula. There has 

also been more recent development that has 

occurred after the 2000 photographs were 

taken. For instance, during 2004 field activities, 

a multi-acre area of recently cleared land was 

observed on the bay side slopes of Judith’s 

Fancy, apparently in preparation for residential 

development. The extent of these areas, 

however, could not be quantified for lack of more 

recent aerial photography.

Additional land use designations in the 

park include public (owned by federal or local 

government), and mixed waterfront-pleasureindustrial. The Columbus Landing site is owned 

by the Government of the Virgin Islands due to 

its historical and cultural significance. Once the 

site of a prehistoric ceremonial ball court and 

the 17th century French and Dutch fortification, 

Fort Sale, the five-acre area has been impacted 

by vehicular traffic and archaeological looting 

(Island Resources Foundation 1993). A second 

public area occupies the southeastern leg of 

the park, extending into the former 4.5 hectare 

Nature Conservancy Wildlife Sanctuary east 

of Triton Bay. Salt River Marina is located 

on the west side of the mouth to Sugar Bay. 

The facility includes 36 slips, a boat ramp, 

restaurant, and dive shop. To the east of the 

marina is Gold Coast Yachts, a boat 

construction facility. Together, the marina, boat 

yard and associated road cover approximately 

1.4 hectares. On the western shore of Triton 

Bay, is the site of the former Fairleigh Dickinson 

University/West Indies Marine Research 

Laboratory where operations for the NOAA 

Undersea Research Program saturation diving 

facilities (Hydrolab and Aquarius) were once 

based. Currently, the majority of the peninsula 

(approximately 23 out of 25 hectares) is 

occupied by a private residence.

The 1998 NRCS survey identified two 

small soil areas as human-altered. A very small 

patch less than 1⁄2 hectare east of Judith’s Fancy 

near the easternmost point of the park, was at 

one time excavated, probably for the purposes 

of mining gravel, sand, or stone for construction. 

The second patch, approximately 1 hectare, 

located in the upper Salt River floodplain, was 

the former site of a tropical fish hatchery for 

which mangroves were cleared over 15 years 

ago (NPS 1990). In year 2000 aerial photo 

mosaicks, half a dozen square “footprints” most 

likely from this operation are visible interrupting 

the forest cover. A raised dirt road was also 

constructed prior to 1977, from the area of the 

former hatchery, extending northwest into the 

southern tip of Sugar Bay. The roadway lies 

approximately 0.5 – 1.0 m above sea level, 

and is topped with bare packed soil and some 

upland vegetation. Today, much of the roadway 

persists though it is not used. Small, sparsely 

distributed white mangroves fringe its sides (See 

Mangroves, section 10). 

Section 13 Land Cover, Soils, & Land Use

Table 13.3. Number of polygons and estimated area of roads and developed areas by map 

classification during 2000. 

Category Classification Number of 

Polygons

Area

(hectares)

Percent of 

Total

Developed Commercial 7 1.4 19%

Residential 14 1.7 23%

Roads Paved 14 1.3 18%

Unpaved 8 2.9 40%

Total 43 7.3 100%
81

Agricultural activity was evident in 1992 

aerial photographs in the southern Salt River 

floodplain. The area was used to grow feed 

for livestock (NPS 1990). Though northern 

portions of the plot closer to Sugar Bay are now 

overgrown, apparently because soil was too 

moist for tractor operation (NPS 1990), southern 

portions retain evidence of the agricultural use. 

In year 2000 aerial photographs, parallel crop 

rows oriented from the northwest to southwest 

remain visible across approximately 1.4 

hectares. 

Most of the natural and seminatural cover in the park consists of forest 

(106 hectares). Approximately 83% of the 

forest canopy is closed, 16% is open, and 

1% is sparse (see Aerial Photography and 

Mapping Methods, Section 2 for description 

of classifications). The bulk of forest cover is 

located in the southern inland portions of the 

park. Smaller patches exist in western portions 

of Estate Judith’s Fancy, between the Columbus 

Landing Site and Salt River Marina, and along 

the northwestern ocean front shores (Figure 

13.1). Due to the topography and relatively low 

rainfall, dry forest communities are characteristic 

of these areas, including semi-deciduous forest 

and gallery semi-deciduous forest (confined to 

riparian corridors where additional moisture is 

available from runoff) (University of the Virgin 

Islands, 2000). Vegetated fields covered 

approximately 14 hectares, the second most 

extensive natural and semi-natural cover 

in the park. Shrubs and bushes account 

for approximately 11 hectares, or 8% of the 

vegetated areas (Table 13.4). Most of the 

shrub and field cover is concentrated in the 

northeastern and northwestern portions of the 

park. 

The Salt River watershed drains 

approximately 3000 acres, and although the 

“river” flows only intermittently, a freshwater 

wetland is located south of the mangrove 

line in Salt River Gut, prior to discharging 

in the mangrove marshes. Vegetation in 

the freshwater wetland is characterized by 

cattails (Typha domingensis). The swamp fern 

(Achrosticum danaefolium) is also occasionally 

found in the area.

ECOLOGICAL LINKAGES

The Salt River watershed is the 

third largest on St. Croix. Rain events 

flush terrigenous sediments into the bays, 

particularly down the Salt River Gut, where 

they are deposited in the benthic sediments 

of the estuary (Gerhard and Bowman 1975) 

(See Geology, Section 4). Activities including 

building, road construction, dredging, and 

vegetation removal, will cause increases in 

sediment input and turbidity in the bay. These 

will in turn, influence benthic vegetation growth 

Table 13.4. Number of polygons and estimated area of natural and semi-natural vegetative land cover during 

2000. 

Section 13 Land Cover, Soils, & Land Use

Vegetation Cover Number of 

Polygons

Area

(hectares)

Percent of 

Vegetative Cover

Forest/Trees Closed - >65% canopy coverage 25 88 67%

Open - 15%-65% canopy coverage 60 17 13%

Sparse - 1%-15% canopy coverage 11 1 1%

Shrubs/Bushes Closed - >65% canopy coverage 10 1 1%

Open - 15%-65% canopy coverage 65 5 4%

Sparse - 1%-15% canopy coverage 31 5 3%

Vegetated Field 50 14 11%

Total 252 131 100%
82

Section 13 Land Cover, Soils, & Land Use

(Gerhard and Bowman 1975) as well as coral 

recruitment and growth in and around Salt River 

Canyon (Hubbard 1989) (See Seagrass and 

Algae, and Reef and Hardbottom, Sections 9 

and 8 respectively).

Activities which affect the hydrology of 

wetlands can influence vegetation communities, 

particularly in the freshwater and mangrove 

wetlands. The alteration of lands for agricultural 

activity in the lower Salt River floodplain, for 

example, has altered water flow to the wetland 

communities located nearby (Island Resources 

Foundation 1993).

Hurricanes are known to affect 

the development and succession of forest 

communities (see Climate, Section 3). 

Hurricane Hugo in 1989 had visible impacts 

on inland forest cover as seen in SARI aerial 

photographs (See Mangroves, Section 10) 

that were still evident in 2000. Organisms 

that utilize vegetation habitats (i.e. birds) are 

consequently impacted by these severe events. 

The effects of such storms can be compounded 

by anthropogenic forest alterations, such as 

clearing for agriculture or development (See 

Birds, Section 12).

REFERENCES

Gerhard, L.C. and J. Bowman. 1975. 

Sedimentation in the Salt River estuary, 

St. Croix, U.S. Virgin Islands. West 

Indies Laboratory/Fairleigh Dickinson 

University Special Publication No. 8. 56 

pgs.

Hubbard, D.K. 1989. Depositional 

environments of Salt River estuary and 

submarine canyon, St. Croix, U.S.V.I. 

In Terrestrial and Marine Geology of St. 

Croix, U.S. Virgin Islands. West Indies 

Laboratory Special Publication No. 8. 

D.K. Hubbard ed. pp. 181-196.

Island Resources Foundation. 1993. Salt River 

Bay Area of Particular Concern and Area 

of Preservation and Restoration: Draft 

Management Plan. June 1993. Pp. 1-50 

and Figures

Jackson, and W.E. McKinzie. 1970. Soil survey 

of the Virgin Islands of the United States. 

United States Department of Agriculture, 

Soil Conservation Service.

National Park Service, Division of Planning, 

Design and Compliance. 1990. 

Alternatives study and environmental 

assessment, Columbus Landing site St. 

Croix, U.S. Virgin Islands. 130 pgs.

Nicholas V., L. Brokaw, and L.R. Walker. 1991. 

Summary of the effects of Caribbean 

hurricanes on vegetation. Biotropica, 

23(4): 442-447.

Riviera, L.H., W.D. Frederick, C. Farris, E.H. 

Jensen, L. Davis, C.D. Palmer, L.F. 

Jackson and W.E. McKinzie. 1970. Soil 

Survey, United States Virgin Islands. 

U.S. Department of Agriculture, Soil 

Conservation Service.

United States Department of Agriculture, Natural 

Resources Conservation Service. 1998. 

Soil survey of the United States Virgin 

Islands. 219 pp.

University of the Virgin Islands, Island 

Resources Foundation, Conservation 

Data Center. 2000. “Rapid Ecological 

Assessment for St. Croix”. CD-ROM. 
83

Section 13 Land Cover, Soils, & Land Use
84

Section 14 Data Gaps and Threats

Salt River Bay National Historical Park 

and Ecological Preserve contains a diverse 

cross section of habitats and ecosystems. 

Ideally, data would be available on the complete 

range of these resources to ensure that 

informed management decisions can be made. 

For this ecological characterization, every 

attempt was made to locate and incorporate all 

of the most relevant and recent data available 

on the park’s resources. However, there have 

only been a limited number of studies conducted 

within SARI on a limited range of topics. As 

a result, the information in this and other park 

characterizations to date is cobbled together 

from a diversity of reports and studies intended 

for other uses, is rarely based on up to date 

conditions, is not comprehensive for the entire 

park, and is typically not even representative of 

all the habitats or biotic groups within the park. 

Compilation of this available data and the spatial 

characterization completed here highlight many 

information gaps that require additional study or 

monitoring.

 Virtually all terrestrial and marine flora 

and fauna lack a comprehensive and systematic 

baseline inventory. Such programs fill a critical 

information gap in assessing resources, guiding 

future research and monitoring, and informing 

management actions. Particularly lacking 

have been studies on SARI reefs outside the 

canyon, algae and seagrass communities 

within the bays, and the mangrove and upland 

forest communities. Since the closure of the 

NOAA/NURP FDU facilities in the 1990’s, 

canyon studies have been virtually abandoned. 

In addition to a lack of key assessment and 

monitoring programs within SARI, the import 

and export of biotic and abiotic material across 

SARI boundaries and reciprocal influences 

with outside ecosystems are even more poorly 

characterized. 

 Despite this, there are currently a 

handful of ongoing programs in place that will 

undoubtedly provide important, up-to-date 

data on some park resources. The aerial 

photographs compiled for this assessment 

and that will likely continue to be periodically 

obtained in the future, provide a valuable 

time series of data for use on a wide range of 

topics. In addition to the seagrass, mangrove, 

benthic, and land cover maps presented here, 

photographs also provide historical information 

on such topics as shoreline change, land 

use and development, and forest health and 

succession. The NOAA CREWS station 

provides nearly continuous point data on key 

atmospheric and marine parameters near 

the submarine canyon. Inside the bays, the 

VIDPNR/DEP continues to collect several key 

variables concerning water quality in the face of 

increasing human pressures. As the University 

of the Virgin Islands CMES and VIDPNR coral 

reef and fish monitoring program continues, 

important long-term data on fish diversity 

and abundance as well as benthic cover will 

be produced. These few existing monitoring 

programs should be maintained and, in many 

cases, expanded in spatial and temporal scope. 

 The human threats to the park’s 

ecosystems are diverse. As noted in the water 

quality section of this and other reports, upland 

erosion from development and land clearing 

within the watershed can have adverse effects 

on the turbidity and sedimentation rates of park 

waters. Relict crop rows in the marsh south of 

Sugar Bay have affected the hydrology of the 

Salt River Gut and water flow to Sugar Bay. 

Figure 14.1. Mangrove prop roots damaged by an 

improperly moored vessel in Triton Bay.

Section 14 Data Gaps and Threats
85

Local government ACE projects redirect flow 

of runoff around nearby housing areas such as 

Mon Bijou which increases speed and volume 

of runoff reaching SARI. Spills or discharges 

of human waste in the vicinity of the marina 

and the many live-aboard boats in that region 

of the park contribute to the high bacterial load, 

hypoxia, and elevated turbidity that periodically 

occur in that area. Other human threats to 

park resources include more direct physical 

degradation of and damage to natural habitats. 

As observed during ground surveys, the prop 

roots of ~30m of red mangrove fringe in Triton 

Bay were recently crushed back to the shoreline, 

presumably by a large boat improperly moored. 

A portion of the upland area behind Sugar Bay 

is fenced with barbed wire to contain horses. 

Trash and other large debris including furniture, 

tires, entire automobiles, and derelict boats litter 

the mangroves and dirt roads behind Sugar 

Bay, as well as the beaches east and west 

of Salt River Bay. Fishing and dive moorings 

on the walls of Salt River Canyon have been 

installed to reduce anchor impacts to the reef, 

however, seagrass and algae within the bays 

are frequently damaged by vessel groundings 

and anchor/chain drag.

 Harvest of natural resources is also 

intense. Over harvest of fish, conch, and lobster 

is pervasive in the region. The high density of 

land crab burrows in the swamp in Sugar Bay 

is matched by an equally high density of pipe 

traps. Informal surveys during ground truthing 

of the maps of this area revealed that virtually 

every land crab burrow was occupied by a trap. 

 The goal of this characterization was to 

compliment existing research and assessments 

on SARI ecology by providing new tools and 

products that managers may use to guide 

future science within the park (see Appendix 

F). It is hoped that the maps created, the aerial 

photographs collected, summary information 

provided, and the data gaps highlighted in the 

present assessment will facilitate the design of 

a formal stratified monitoring program for many 

of the park’s habitats. The park has within its 

borders a wide variety of tropical ecosystem 

components including terrestrial, wetland, bay, 

and open water regions with diverse habitat 

types such as coastal forests, mangroves, algal 

and seagrass beds, mud and sand, and several 

types of coral reef and hard bottom. With the 

information provided in this characterization, 

park managers now have additional tools to aid 

in the stewardship of this diverse ecosystem. 

Section 14 Data Gaps and Threats

Figure 14.2. Assorted catch of a Salt River fisherman.
86

Section 15 Additional Information

Additional information in the following subject 

areas is available from the web sites listed 

below. 

http://www.nps.gov/sari/ ...for information on 

the National Park Service on St.Croix, general 

information on SARI, hard copy, and scans of 

aerial photographs of SARI, and all other data 

products in this report.

Written requests for information on other 

inquiries should be sent to...

2100 Church Street #100

Christiansted VI 00820-4611

or by phone at 340-773-1460

or fax at 340-773-2950

or by email at Zandy_Hillis-Starr@nps.gov

http://biogeo.nos.noaa.gov/ ...for information on 

benthic and land cover maps in this report 

http://geodesy.noaa.gov/ ...for information on 

NOAA aerial photography 

http://www.coral.noaa.gov/ ...for information on 

NOAA’s Coral Reef

Early Warning System 

http://www.dpnr.gov.vi/ ...for information on 

the local government involved in research and 

management at SARI. The site includes links to 

information on such topics as water quality and 

wildlife monitoring in the U.S. Virgin Islands.

http://www.coral.noaa.gov/ ...for information 

on Comprehensive bibliography of Salt River 

research 

88

Appendices
89

Year Principal Investigators Title Located

1978 C. Birkeland and S. Neudecker Comparative Study of Chaetodontid Foraging Patterns X

1978 C. Smith and J. Tyler Regulatory Mechanisms in Coral Reef Fish Communities X

1978 D. Arneson and L. Meiklejohn Diel and Depth Variation in the Population Densities of 

Commercially Important Carnivorous Fishes

1978 D. Hubbard, J. Sadd, H. 

Tonnemacher, and C. Phips

Sediment Transport Processes of Salt River Submarine 

Canyon St. Croix, U.S. Virgin Islands X

1978 I. Clavijo Diel and Depth Variation in the Population Densities of 

Herbivorous Fishes

1978 P. Colin, A. Arneson, and R. Boulon Spawning of Western Atlantic Reef Fishes

1978 P. Colin, A. Arneson, and R. Boulon Coral Distribution in the Salt River Canyon X

1978 P. Winkler and R. Bolton Oxygen Consumption of Reef Fishes During Quiescent 

Periods of their Circadian Activity Cycles

1978 R. Clarke and G. Dale The Role of Light in Nocturnal/Diurnal Changeover 

Patterns of Certain Coral Reef Fishes

1978 R. Hanlon and R. Hixon Response of Squids to Night Lights and Reef Behavior of 

Octopuses X

1978 R. Vaissiere, A Meinesy, C. 

Falconetti, and D. Bay

Comparison of Mediterranean and Caribbean Benthionic 

Biological Systems X

1978 S. Bortone, R. Hastings, D. Siegel, 

R. Bolton Quantification of Reef Fishes X

1979 D. Hubbard, S. McGowan, H. 

Tonnemacher, J. Sadd Geologic Development of Salt River Canyon X

1979 D. Meyer, G. Minnery, C. Messing, 

L. Somers

The Comparative Feeding Behavior of Crinoids and 

Ophiuroids X

1979 D. Olsen, K. Turbe, B. Friedman Optimum Yield for Virgin Islands Black Coral Fishery X

1979 E. Williams, J. Kimmel, R. Waldner, 

L.Williams

Manipulation of Large External Isopods (Genus Anilocra) 

on Brown and Blue Chromis X

1979 J. Ogden, S. Miller, W. McFarland, 

N. Wolf, M. Shulman, J. Ebersole

The Settlement and Recruitment of Postlarval Fishes into 

the Coral Reef Community X

Appendix A: Coral Literature Education and Outreach Program Reference List

Appendix A. Hydrolab/Aquarius Bibliography
90

Year Principal Investigators Title Located

1979 W. Gladfelter, W. Johnson, J. 

Davidson

Structure of the Planktivorous Fish Community Along a 

Depth Gradient

1980

A. Hurley, M. Josselyn, R. Cowen, 

S. Hawes, G. Cailliet, T. Niessen, J. 

Connor

The Sources, Dispersal, and Utilization of Benthic Drifting 

Plants in the Salt River Submarine Canyon X

1980 D. Olsen, G. McCrain, B. Friedman Characteristics of Black Coral Trees in Salt River 

Canyon: Management Data X

1980 H. Lasker, M. Russel, M. Gottfried, 

D. Gordon

Resource Availability and Suspension Feeding by 

Gorgonians X

1980 I. Clavijo, A. Bardales, L. Amador, 

J. Ramirez, J. Morell, A. Mendez

Diel Migrations of Scarus Guacamaia and Scarus

Coelestinus X

1980 M. Reaka, C. VanZant, N. Wolf, F. 

Pecora, J. Lansteiner

An Experimental Analysis of Ecological Processes That 

Structure Fish and Invertebrate Reef Communities X

1980 P. Winkler, I. Szurley, and L. 

Greiner

In Situ Oxygen Consumption of Reef Fishes During 

Quiescence

1980 S. Neudecker, W. Hamilton, P. 

Lobel

Social Behavior and Feeding Ecology of Caribbean 

Chaetodontids X

1980 T. Suchanek, D. Duggins, B. 

Rivest, P. Banko

Influence of Sediment Bioturbators on the Success of 

Seagrass Communities X

1980 W. Johnson, J. Davidson, V. 

Chase, F. Johnson, S. Hamilton

Resource Utilization Patterns in a Deep-Water 

Planktivorous Fish Community at Salt River Canyon X

1980 Y. Sadovy, I. Clavijo, K. Boulon Social Behavior in Eupomacentrus partitus X

1981 C. Rogers, M. Gilnack, C. Fitz, J. 

Beets, J. Hardin

Relationship of Coral Recruitment and Grazing Intensity 

to the Distribution of Algae and Corals in Salt River 

Canyon

X

1981 D. Hubbard, J. Westerfield, J. 

Bayes, A. Miller, I. Gill, R. Burke Geological Development of Salt River Submarine Canyon X

1981 E. Reese, T. Hourigan, R. Stanton, 

B. Carlson, P. Motta

Feeding and Space-Related Behavior of Three Species 

of Pomacanthid Fishes

1981 E. Williams, L. Williams, R. 

Waldner, M. Dowgiallo

Manipulation of Large External Isopods (Genus Anilocra) 

on Brown and Blue Chromis and Coneys X

1981 G. Gitschlag Development and Testing of Underwater Fish Marking 

and Release Techniques X

1981 G. Helfman, J. Meyer, D. 

Dallmeyer, E. Bozeman Trumpetfish Distribution and Predation X

1981 G. Samson, E. Igleria, A. Lee, J. 

Arteaga Fish Behavior in Relation to Commercial Fish Traps

Appendix A. Hydrolab/Aquarius Bibliography
91

Year Principal Investigators Title Located

1979 W. Gladfelter, W. Johnson, J. 

Davidson

Structure of the Planktivorous Fish Community Along a 

Depth Gradient

1980

A. Hurley, M. Josselyn, R. Cowen, 

S. Hawes, G. Cailliet, T. Niessen, J. 

Connor

The Sources, Dispersal, and Utilization of Benthic Drifting 

Plants in the Salt River Submarine Canyon X

1980 D. Olsen, G. McCrain, B. Friedman Characteristics of Black Coral Trees in Salt River 

Canyon: Management Data X

1980 H. Lasker, M. Russel, M. Gottfried, 

D. Gordon

Resource Availability and Suspension Feeding by 

Gorgonians X

1980 I. Clavijo, A. Bardales, L. Amador, 

J. Ramirez, J. Morell, A. Mendez

Diel Migrations of Scarus Guacamaia and Scarus

Coelestinus X

1980 M. Reaka, C. VanZant, N. Wolf, F. 

Pecora, J. Lansteiner

An Experimental Analysis of Ecological Processes That 

Structure Fish and Invertebrate Reef Communities X

1980 P. Winkler, I. Szurley, and L. 

Greiner

In Situ Oxygen Consumption of Reef Fishes During 

Quiescence

1980 S. Neudecker, W. Hamilton, P. 

Lobel

Social Behavior and Feeding Ecology of Caribbean 

Chaetodontids X

1980 T. Suchanek, D. Duggins, B. 

Rivest, P. Banko

Influence of Sediment Bioturbators on the Success of 

Seagrass Communities X

1980 W. Johnson, J. Davidson, V. 

Chase, F. Johnson, S. Hamilton

Resource Utilization Patterns in a Deep-Water 

Planktivorous Fish Community at Salt River Canyon X

1980 Y. Sadovy, I. Clavijo, K. Boulon Social Behavior in Eupomacentrus partitus X

1981 C. Rogers, M. Gilnack, C. Fitz, J. 

Beets, J. Hardin

Relationship of Coral Recruitment and Grazing Intensity 

to the Distribution of Algae and Corals in Salt River 

Canyon

X

1981 D. Hubbard, J. Westerfield, J. 

Bayes, A. Miller, I. Gill, R. Burke Geological Development of Salt River Submarine Canyon X

1981 E. Reese, T. Hourigan, R. Stanton, 

B. Carlson, P. Motta

Feeding and Space-Related Behavior of Three Species 

of Pomacanthid Fishes

1981 E. Williams, L. Williams, R. 

Waldner, M. Dowgiallo

Manipulation of Large External Isopods (Genus Anilocra) 

on Brown and Blue Chromis and Coneys X

1981 G. Gitschlag Development and Testing of Underwater Fish Marking 

and Release Techniques X

1981 G. Helfman, J. Meyer, D. 

Dallmeyer, E. Bozeman Trumpetfish Distribution and Predation X

1981 G. Samson, E. Igleria, A. Lee, J. 

Arteaga Fish Behavior in Relation to Commercial Fish Traps

Appendix A. Hydrolab/Aquarius Bibliography
92

Year Principal Investigators Title Located

1982 R. Steneck Role of Productivity and Herbivory in Structuring Tropical 

Algal Communities X

1982 T. Suchanek Competition Among Encrusting Colonial Invertebrates in 

Open Reef Habitats X

1983 A. Szmant-Froelich Role of Herbivorous Fish in Nitrogenous Regeneration of 

Coral Reefs X

1983 C. Falconetti Morphological Variation of Caulerpa: Study of 

Macrobenthic Species on the Shelf Bottom

1983 D. Bay Sociobiology and Sex Change of Labroid Fishes

1983 E. Williams Early Life History and Host Relationships of the Isopod 

Anilocra chromis X

1983 I. Workman Attraction of Pelagic Fishes to Midwater Structures X

1983 J. Coyer Influence of Fish Predators on Activity Patterns of 

Diadema antillarum X

1983 M. Reaka Patterns of Life History and Behavior in Coral Reef 

Organisms

1983 M. Robblee, C. McIvor Assessment of Deep Halophila Seagrass Meadow as 

Fish Habitat and Feeding Ground

1983 N. Downing, C. Al-Zehar Artificial Reef Utilization by Grouper Fish

1983 N. Targett Chemical Ecology and Histocompatibility of Sponges

1983 R. Bray Planktivorous Fish as Nutrient Importers in Tropical Reef 

Communities

1983 S. Williams Growth of Caulerpa spp. and its Relationship to Sediment 

Habitat X

1983 T. Niesen Ecological Function and Fishery Resources of Halophila

Beds

1984 A. Landry Evaluation of Multilevel Artificial Structures in the 

Attraction of Deep Reef Fishes

1984 A. Szmant-Froelich Nutrient Regeneration in Coral Reef Sediments

1984 C. Bouchon

Irradiance Measurements, Correlation Bathymetric 

Distribution of Scleractinian Corals in Salt River Canyon, 

St. Croix

Appendix A. Hydrolab/Aquarius Bibliography
93

Year Principal Investigators Title Located

1984 C. Smith and J. Tyler Diversity and Relative Abundance of Fish Larval Stages X

1984 D. Hubbard Geological Development of Salt River Submarine Canyon X

1984 E. William Early Life History and Host Relationships of the Isopod 

Anilocra chromis X

1984 I. Workman

Evaluation of the Potential of Using Fish-Attracting 

Devices to Attract Harvestable Concentrations of Coastal 

Pelagic Fishes Into Shallow Caribbean Waters

1984 K. Sebens Effect of Water Flow on Coral Respiration and 

Productivity

1984 M. Coulston

Assessment of the Queen Conch (Strombus gigas) 

Population and Predation Studies of Hatchery-Reared 

Juveniles in Salt River Canyon, St. Croix, V.I.

X

1984 N. Targett Chemical Ecology of Space Competition Between 

Sponges and Corals

1984 R. Larson Ecological Function and Fishery Resources of Halophila

in the Caribbean

1984 S. Williams Diurnal Growth Patterns in Halophila and Caulerpa

1984 W. Johnson 

Role of Cleaning Stations in Overall Fish Community 

Organization Along a Depth Gradient at Salt River 

Canyon, St. Croix

1985 C. Smith and J. Tyler

Growth and metamorphosis of coral reef fish larval 

stages in the Salt River canyon, St. Croix, USVI: Final 

Scientific Report Mission 85-5

X

1985 K. Sebens, M. Patterson, R. Olson Effect of Water Flow on Coral Respiration and 

Productivity

1985 M. Hay

Does the Tropical Seaweed Halimeda Reduce Herbivory 

by Growing at Night?: Diel Patterns of Growth, Nitrogen 

Content, Herbivory, and Chemical Versus Morphology 

Defenses

1985 N. Targett, J. Porter Chemical Interactions Between Sponges and Corals

1988 C. Butman

Field Studies of the Roles of Spatial Scale and BoundaryLayer Flow Regime in Active Habitat Selection by Settling 

Larvae: Preliminary Sampling

1988 G. King Oxygen Dynamics and Anaerobic Metabolism in 

Sediments of Salt River Canyon

1988 H. Foushee An Observational and Survey Study of Crew Composition 

and Member Satisfaction in Subsea Habitats

1988 J. Porter The Energetics of Sediment Removal and Zooplankton 

Feeding in Caribbean Reef-Building Corals

Appendix A. Hydrolab/Aquarius Bibliography
94

Year Principal Investigators Title Located

1988 K. Sebens Effect of Water Movement on Zooplankton Feeding by 

Corals

1988 M. Patterson Field Measurement of Diffusional Boundary Layers and 

Turbulent Enhancement in Scleractinian Reef Corals

1988 R. Steneck

Patterns and Processes Structuring Tropical Algal 

Communities Along a Depth Gradient: The Dynamic 

Roles of Productivity and Herbivory

1988 T. Fisher Primary Productivity and Nutrient Fluxes of the Benthic 

Microflora of Coral Reef Sediments

1989 A. Miller, M. Boardman, K. Parsons

Spatial Resolution and Taphonomic Gradients in 

Accumulating Molluscan Remains, Salt River, St. Croix: 

Postponed Due to Hurricane Hugo

1989 C. Harvell Chemical and Structural Defenses of Caribbean 

Gorgonians: Pattern and Process Over a Depth Gradient X

1989 G. Helfman, L. Kaufman Effects of Ontogeny and Refuge Quality on ThreatSensitivity in Recently-Recruited Coral Reef Fishes

1989 G. King Effects of Animal Disturbance on Microbiological 

Processes in Sediments of Salt River Canyon

1989 G. Wellington Ultraviolet Light and its Effect on Reef-Building Corals

1989 J. Ebersole, L. Kaufman

Adaptive Selection of Local Habitat and Passive 

Movement of Larvae as Factors Influencing Composition 

of Assemblages of Fishes on Coral Reefs

1989 J. Woodley

The Trophic Impact of Deposit and Suspension-Feeding 

Ophiuroids on Recruitment of Other Coral Reef 

Organisms: A Feasibility Study

1989 L. Madin

In Situ Studies of the Distribution, Behavior, and 

Community Ecology of Zooplankton, Micronekton, and 

Benthos at a Deep-Sea Station Near St. Croix, USVI

1989 M. Coulston, O. Hewlett, Z. Hillis, 

M. Taylor, R. Simms, M. Herko

Environmental Monitoring in the Salt River Submarine 

Canyon X

1990 C. Petersen The Evolution of Mating Systems and Fertilization Rates 

in Hermaphroditic Fishes

This list and some of the publications, are available online at the website of the NOAA/OAR/Atlantic, 

Oceanographic and Meteorological Laboratory (AOML),

http://www.aoml.noaa.gov/general/lib/crews.htm.

Although a complete list (with the possible exception of 1985) of Hydrolab and Aquarius mission 

abstracts for Salt River was compiled, a complete collection of mission reports could not be located.

Reports or related publications that were available or acquired for approximately 50 out of 103 missions,

and are indicated with an X in the "Located" column.

Appendix A. Hydrolab/Aquarius Bibliography
95
96

Coral Species East Wall West Wall References Cited

Acropora cervicornis x x a, e

Acropora palmata x a, e

Agaricia agaricites x x a, c, d, e

Agaricia fragilis x x a, e

Agaricia lamarcki x x d, e

Colpophyllia natans x x a, b, c, d, e

Dendrogyra cylindrus x b, e

Dichocoenia stokesii x x a, b, c, d, e

Diploria clivosa x x a, b

Diploria labyrinthiformis x x a, b, c, d, e

Diploria strigosa x x a, b, c, d, e

Eusmilia fastigiata x x a, b, d, e

Favia fragum x x a, e

Helioseris cucullata x x a, d, e

Isophyllastrea rigida x x d, e

Isophyllia sinuosa x x d, e

Madracis decactis x x a, c, d, e

Madracis mirabilis x c, e

Manicina areolata x e

Meandrina meandrites x x a, b, c, d, e

Millepora alcicornis x x a, b, c

Millepora complanata x b

Montastraea annularis x x a, b, d, e

Montastraea cavernosa x x a, b, c, d, e

Montastraea faveolata x x c

Montastraea franksi x c

Mussa angulosa x a, e

Mycetophyllia aliciae x x e

Mycetophyllia ferox x x a, b, c, d, e

Mycetophyllia lamarckiana x a, e

Phyllangia americana x a

Porites astreoides x x a, b, c, d, e

Porites furcata x a

Porites porites x x b, c, d, e

Scolymia cubensis x x a

Scolymia lacera x a

Siderastrea radians x x a, b

Siderastrea siderea x x a, b, c, d, e

Appendix B. List of coral species found during previous research and 

monitoring activities in Salt River Canyon 

Appendix B. Coral Species List for Salt River Canyon
97

Appendix B. Coral Species List for Salt River Canyon

Coral Species East Wall West Wall References Cited

Stephanocoenia mechelinii x x b, c, d, e

Stylaster roseus x a

Tubastraea aurea x x a, b

References

a. Boulon, RH. 1978. Coral distributions in the Salt River Submarine Canyon, St.Croix, US Virgin Islands. Final 

Scientific Report NOAA Hydrolab; Mission 78-6B. Pp. 1-18.

b. Kesling, CA. 1990. Preliminary report: Effects of Hurricane Hugo on the benthic coral reef community of Salt 

River Submarine Canyon, St.Croix, US Virgin Islands. Final Scientific Report NOAA Aquarius; Mission 89-4C Pp. 

1-20 and in Diving for Science; Proc. Of the 10th Annual American Academy of Underwater Sciences Diving 

Symposium. Japp, W., St. Petersburg, Fl.

c. Nemeth, RS, S Herzlied, M Taylor, S Harold, and W Toller. 2003. Video monitoring assessment of coral reefs 

in St.Croix, United States Virgin Islands. Year two final report to VI Department of Planning and Natural 

Resources. Pp. 1-9 and Appendices.

d. Rogers, CS, M Gilnak, and HC Fitz III. 1983. Monitoring of coral reefs with linear transects: A study of storm 

damage. Journal of Experimental Marine Biology and Ecology 66:285-300

e. Rogers, CS, HC Fitz III, M Gilnack, J Beets, and J Hardin. 1984. Scleractinian coral recruitment patterns at 

Salt River Submarine Canyon, St.Croix, US Virgin Islands. Coral Reefs 3:69-76
98

Appendix C. Plant Species LIst

Scientific Name Common Name Reference Cited

Acacia macrancantha stink casha d

Acacia tortuosa casha a, c, d

Achyranthes indica man-better-man d

Acrostichum daneaifolium swamp fern c, d

Agave eggersiana* Egger's agave* c

Agave spp. century plant e

Ageratum conyzoides goat weed d

Albizia lebbek Tibet e

Annona muricata soursop d

Annona squamosa sugar apple d

Antigonon leptopus Mexican love d

Bambusa vulgaris bamboo d

Batis maritima saltwort e

Bidens pilosa beggarticks a, d

Blutaparon vermiculare salt weed d

Boerhavia coccinea boerhavia, hog weed a

Borrichia aborescens sea oxeye e

Bourreria succulenta pigeon-berry d

Bucida buceras gregre a, d

Bursera simaruba turpentine tree, gumbo-limbo a, d

Caesalipinia bonduc / C. crista grey knickers, nickerbean d

Cakile lanceolata searocket a, d, e

Calotripis procera giant milkweed d

Canavalia maritima baybean d

Capparis cynophallophora Jamaican caper a, d

Capparis flexuosa limber caper a, d

Capparis frondosa rat-bean d

Capparis indica caper d

Carcia papaya papaya d

Cassia siamea yellow cassia d

Cassytha filiformis love vine e

Cenchrus echinatus sandburr d

Chrysophyllum pauciflorum caimito de perr d

Cissus sicyoides pinekoop a, d

Citharexylum fruticosa pasture fiddle, fiddle wood d

Cleome viscosa tickweed, spider flower d

Appendix C. List of Plant Species Observed in Salt River National Historic 

Park and Ecological Preserve
99

Appendix C. Plant Species List

Scientific Name Common Name Reference Cited

Clitoria ternatea butterfly pea a

Cocoloba uvifera seagrape d, e

Cocos nucifera coconut palm a, b, d, e

Commelina diffusa blue day-flower d

Commelina elegans d

Comocladia dononaea Christmas bush d

Conocarpus erectus buttonwood b, c, d, e

Cordia alba white manjack a, b, d

Cordia collococca red manjack a, d

Corton rigidus maran a

Corton spp. corton d

Crescentia cujete calabash b

Crotalaria sp. yellow sweet pea a

Cryptostegia grandiflora Indian rubber, rubber vine d, e

Delonix regia flamboyant tree d

Distichlis spicata beach grass d

Epidendrum bifidum* c

Epidendrum ciliare* spider orchid* c

Eugenia rhombea spiceberry d

Eugenia spp. pencil bush d

Ficus citrifolia shortleaf fig d

Guaicacum officinale* lignumvitae* d

Guapira fragrans black mampoo d

Hibiscus sp. hibiscus b

Hippomane mancinella manchineel a, c, d

Ipomoea pes-capre beach morning glory d, e

Ipomoea sp. goats foot a, d, e

Jacquinea arborea a

Jatropha gossypifolia physic nut, bellyache bush a

Kalanchoe pinnata leaf of life d, e

Lantana camara yellow sage d

Lantana invulcrata wild sage d

Lantana spp. sages d

Laportea sp. stinging nettle a

Leucaena leucacephala tan-tan a, c, d, e

Ludwigia sp. d

Malphigia infestissima* stingbush* a, c, d

Malphigia woodburyana* cow-itch, cowage cherry* a

Malvastrum corchorifolium false mallow e
100

Appendix C. Plant Species List

Scientific Name Common Name Reference Cited

Malvastrum coromandelianum threelobe false mallow e

Mammilaria nivosa* wolly nipple* c

Mangifera indica mango d

Melicoccus bijugatus genip a, d, e

Merremia quinquefolia merremia, merremia vine a, e

Momordica charantia maiden apple d

Morinda citrifolia painkller e

Morisonia americana rat-apple d

Opuntia spp. d

Panicum maxium guinea grass a, d

Petiveria alliacea garlic weed d

Pilosocereus royenii pipe organ cactus d

Piscidia piscipula fish poision trees d

Pisonia aculeata prickly mampoo d

Pithecellobium unguis-cati bread and cheese a, d, e

Pluchea symphitifolia sweet scent d

Portulaca oleracea little hogweed, purslane e

Psychotria nervosa wild coffee d

Randia aculeata box-briar d

Rhizophora mangle red mangrove a, b

Rivina humilis cat's blood a, d

Roystonea regia royal palms b

Sansevieria sp. snake plant a, e

Schaefferia frutescens Florida boxwood d

Schinus terebinthifolius Christmasberry e

Sesuvium portulacastrum sea purslane a, d, e

Sida acuta broom weed a, e

Spartina patens salt grass d

Stachytarpheta jamaicensis blue porterweed a

Suriana maritima bay cedar d

Tabebuia heterophylla pink cedar d, e

Tamarindus indica tamarind b

Tecoma stans ginger thomas a, d, e

Terminalia catappa West Indian almond, tropical almond a, d, e

Thespesia populnea haiti-haiti, seaside maho a, d, e

Triphasia trifolia sweet lime, limeberry a, d

Typha domingensis cattail d

Yucca aloifolia spanish bayonet e

Yucca spp. a, d

100
101

Scientific Name Common Name Reference Cited

Zanthoxyllum flavum satin wood c

Zanthoxylum martinicense white prickle d

Zanthoxylum monophyllum yellow prickle d

* Indicates species is locally listed as threatened or endangered by The Virgin Islands Department of 

Planning and Natural Resources, Division of of Fish and Wildlife, 1991.

Documents cited:

a) Coastal Consultants, 1987. Environmental Assessment Report for Columbus 

Landing: A Marina, Restaurant Shopping and Office Complex at Estate Morningstar on Sugar Bay (Salt 

River). 64 pgs.

b) Haines Enterprises, Inc. 1983. Major Class I Environmental Assessment Report for the Proposed Docking 

Facility at Salt River Marina, Estate Salt River, Sugar Bay, St. Croix, United States Virgin Islands. 87 pgs.

c) Virgin Islands Department of Planning and Natural Resources, 1993. Salt River Bay and Watershed 

(APR) Area of Particular Concern (APC) and Area for Preservation and Restoration (APR), A Comprehensive 

Analytic Study. 60 pgs.

d) Government of the U.S. Virgin Islands. 1990. Alternatives Study and Environmental Assessment, 

Columbus Landing Site, St. Croix, U.S. Virgin Islands.

 e) Sugar Bay Land Development, Ltd., 1986. Environmental Assessment Report Preliminary Submittal.

Appendix C. Plant Species List

101
Appendix D. Fish Species List

102

Scientific Name Mangrove Canyon Walls Pelagic FAD References Cited

Abudefduf saxatilis x x a, c, d, e

Acanthemblemaria aspera x d

Acanthemblemaria chaplini x d

Acanthemblemaria maria x d

Acanthemblemaria spinosa x d

Acanthostracion polygonia x c, d, e

Acanthostracion quadricornis x d, f

Acanthurus bahianus x c, d, e

Acanthurus chirurgus x x a, c, d, e

Acanthurus coeruleus x x a, c, d, e

Alectis ciliaris x f

Aluterus scriptus x d, e

Amblycirrhitus pinos x d

Anisotremus surinamensis x d

Anisotremus virginicus x x a, d ,e

Antennarius multiocellatus x d

Apogon binotatus x c, d 

Apogon lachneri x c, d

Apogon maculatus x d

Apogon townsendi x c, d, e

Archosargus rhomboidalis x a

Aulostomus maculatus x a, d, e

Balistes vetula x d, e

Bodianus rufus x c, d, e

Bothus lunatus x c, d, e

Bothus ocellatus x c

Calamus calamus x d

Cantherhines macrocerus x d, e

Cantherhines pullus x d, e

Canthidermis sufflamen x d, f

Canthigaster rostrata x c, d, e

Caranx bartholomaei x e

Caranx crysos x d, e

Caranx hippos x d

Caranx latus x x a, e, f

Caranx ruber x x x a, b, c, d, e, f

Centropomus undecimalis x a

Centropyge argi x d

Centropyge aurantonotus x d

Appendix D. List of fish species found within the boundaries of SARI
Appendix D. Fish Species List

Scientific Name Mangrove Canyon Walls Pelagic FAD References Cited

Cephalopholis cruentatus x c, d, e

Cephalopholis fulvus x c, d, e

Chaenopsis limbaughi x d

Chaetodon aculeatus x c, d, e

Chaetodon capistratus x x a, c, d, e

Chaetodon ocellatus x d, e

Chaetodon sedentarius x d

Chaetodon striatus x x a, c, d, e

Chilomycterus antennatus x d

Chromis cyanea x c, d, e

Chromis insolata x d

Chromis multilineata x c, d, e

Chromis scotti x d

Clepticus parrae x x a, c, d, e, f

Coryphaena hippurus x b

Coryphopterus dicrus x d

Coryphopterus eidolon x d

Coryphopterus glaucofraenum x c, d, e

Coryphopterus lipernes x c, d, e

Coryphopterus personatus/hyalinus x c, d, e

Cryptotomus roseus x c

Dactylopterus volitans x c

Dasyatis americana x c, d, e

Decapterus macarellus x d, f

Decapterus tabl x d

Diodon holocanthus x d

Diodon hystrix x x a, c, d, f

Echeneis naucrates x e

Elagatis bipinnulata x d

Emblemaria pandionis x c, d

Emblemariopsis bahamensis x d

Emmelichthyops atlanticus x d

Enchelycore carychroa x d

Enneanectes altivelis x d

Enneanectes boehlkei x d

Epinephelus adscensionis x c, d, e

Epinephelus guttatus x c, d, e

Epinephelus itajara x c

Epinephelus striatus x d

Equetus acuminatus x a

Equetus punctatus x x a, d, e

Eucinostomus jonesi x a

103
Appendix D. Fish Species List

104

Scientific Name Mangrove Canyon Walls Pelagic FAD References Cited

Euthynnus alletteratus x f

Fistularia tabacaria x d

Garmannia saucra x d

Gerres cinereus x x a, c, d, e

Ginglymostoma cirratum x e

Gnatholepis thompsoni x c, d

Gobiosoma chancei x d

Gobiosoma evelynae x d

Gobiosoma genie x c, d

Gobiosoma louisae x d

Gobiosoma pallens x d

Gobiosoma prochilos x d

Gobiosoma tenox x c

Gramma loreto x c, d, e

Gymnothorax funebris x x a, d, e

Gymnothorax miliaris x d

Gymnothorax moringa x c, d

Gymnothorax vicinus x c

Haemulon aurolineatum x x a, c, d, e

Haemulon carbonarium x x a, d, e

Haemulon chrysargyreum x x a, c, d

Haemulon flavolineatum x x a, c, d, e

Haemulon macrostomum x a

Haemulon parra x x a, d

Haemulon plumieri x x a, c, d, e

Haemulon sciurus x x a, c, d, e

Haemulon striatum x a

Halichoeres bivittatus x x a, c, d, e

Halichoeres garnoti x c, d, e

Halichoeres maculipinna x x a, c, d, e

Halichoeres pictus x c, d, e

Halichoeres poeyi x c

Halichoeres radiatus x c, d

Hemiramphus brasiliensis x f

Heteroconger longissimus x d

Heteropriacanthus cruentatus x d

Hirundichthys speculiger x d

Holacanthus bermudensis x d

Holacanthus ciliaris x c, d

Holacanthus tricolor x c, d, e

Holocentrus adscensionis x c, d, e

Holocentrus rufus x c, d, e
Appendix D. Fish Species List

105

Scientific Name Mangrove Canyon Walls Pelagic FAD References Cited

Hypoplectrus chlorurus x d, e

Hypoplectrus guttavarius x d, e

Hypoplectrus indigo x d

Hypoplectrus nigricans x d, e

Hypoplectrus puella x d, e

Hypoplectrus unicolor x c, d, e

Inermia vittata x c, d, f

Katsuwonus pelamis x b

Kyphosus sectatrix/incisor x d, e

Labrisomus nuchipinnis x a

Lachnolaimus maximus x d

Lactophrys bicaudalis x c, d, e

Lactophrys triqueter x c, d, e, f

Liopropoma carmabi x d

Liopropoma rubre x c, d

Lucayablennius zingaro x c, d

Lutjanus analis x x a, c, d, e

Lutjanus apodus x x a, c, d, e

Lutjanus griseus x x a, d

Lutjanus jocu x a

Lutjanus mahogoni x x a, c, d, e

Lutjanus synagris x x a, d

Malacanthus plumieri x d

Malacoctenus triangulatus x d

Melichthys niger x d, e, f

Microgobius carri x d

Microspathodon chrysurus x x a, d, e

Monacanthus tuckeri x c, d

Mugil curema x a

Mulloidichthys martinicus x x a, c, d, e

Mycteroperca bonaci x d

Mycteroperca interstitialis x d

Mycteroperca tigris x d

Mycteroperca venenosa x d

Myripristis jacobus x c, d, e

Neoniphon marianus x c, d, e

Nicholsina usta x a

Ocyurus chrysurus x x a, c, d, e, f

Odontoscion dentex x x a, c, d

Ophioblennius atlanticus x d

Opistognathus aurifrons x c, d

Paradiplogrammus bairdi x d
Appendix D. Fish Species List

106

Scientific Name Mangrove Canyon Walls Pelagic FAD References Cited

Paranthias furcifer x d

Phaeoptyx conklini x c

Phaeoptyx pigmentaria x d

Phaeoptyx xenus x d

Platax orbicularis x a

Plectrypops retrospinis x d

Pomacanthus arcuatus x c, d, e

Pomacanthus paru x x a, c, d, e

Priacanthus cruentatus x c

Priolepis hipoliti x c

Pseudupeneus maculatus x c, d, e

Ptereleotris calliurus x d

Ptereleotris helenae x c, d

Remora remora x d

Risor ruber x d

Rypticus bistrispinus x d

Rypticus saponaceus x c, d, e

Sargocentron coruscum x c

Sargocentron vexillarium x c, d

Scarus coeruleus x d

Scarus guacamaia x c, f

Scarus iserti x x a, c, d, e

Scarus taeniopterus x c, d, e

Scarus vetula x x a, c, d, e

Scomberomorus cavalla x f

Scomberomorus regalis x b, c, d, e, f

Scorpaena plumieri x c, d

Seriola dumerili x d

Serranus baldwini x c, d

Serranus tabacarius x c, d, e

Serranus tigrinus x c, d, e

Serranus tortugarum x d

Sparisoma atomarium x c, e

Sparisoma aurofrenatum x x a, c, d, e

Sparisoma chrysopterum x x a, c, d, e

Sparisoma radians x a

Sparisoma rubripinne x x a, d, e

Sparisoma viride x x a, c, d, e

Sphoeroides spengleri x x a, c, d

Sphoeroides testudineus x a

Sphyraena barracuda x x x a, b, c, d, e, f

Sphyraena picudilla x d
Appendix D. Fish Species List

107

Scientific Name Mangrove Canyon Walls Pelagic FAD References Cited

Stegastes adustus x x a, c, d, e

Stegastes diencaeus x c, d

Stegastes leucostictus x x a, d, e

Stegastes partitus x x a, c, d, e

Stegastes planifrons x c, d, e

Stegastes variabilis x x a, d

Synodus intermedius x c, d, e

Thalassoma bifasciatum x c, d, e

Thunnus atlanticus x b

Tylosurus crocodilus x x b, d

Xyrichtys splendens x c, d

References

a. Adams, AJ, and WJ Tobias. 1994. Red mangrove prop-root habitat as finfish nursery area: a case study of 

Salt River Bay, St.Croix, USVI. Proceedings of the forty-sixth annual Gulf and Caribbean Fisheries Institute, 

Corpus Christi, USA. 22-46 Pp.

b. Friedlander, A., J Beets, and W. Tobias. 1994. Effects of fish aggregating device design and location on 

fishing success in the US Virgin Islands. Bulletin of Marine Science. 55:592-601.

c. Kaufman, LS, JP Ebersole. 1984. Microtopography and the organization of two assemblages of coral reef 

fishes in the West Indies. Journal of Experimental Marine Biology and Ecology. 78:253-268.

d. Reef Environmental Education Foundation (REEF). http://www.reef.org/.

e. Toller, W, 2002. Quantitative estimates of species composition and abundance of fishes, and fish 

species/habitat associations in St. Croix, U.S. Virgin Islands. Final Report: Patterns of habitat utilization by reef 

fish on St. Croix, F07017, Study3.

e. Nemeth, RS, S Herzlieb, ES Kadison, M Taylor, P Rothenberger, S Herold, and W Toller. 2004. Coral reef 

monitoring in St. Croix and St. Thomas, United States Virgin Islands. Year three final report submitted to 

Department of Planning and Natural Resources. Center for Marine and Environmental Studies, University of the 

Virgin Islands and Division of Fish and Wildlife, DPNR. 1- 120 Pp.

f. Workman, IK, AM Landry Jr., JW Watson Jr., and JW Blackwell. 1985. A midwater fish attraction device study 

conducted from hydrolab. Bulletin of Marine Science. 37:377-386
108

Appendix E. Ground Truth Points

Site Longitude Latitude Depth

(m) Field Notes

1 -64.754959 17.775354 0.9 continuous seagrass

2 -64.755575 17.775571 1.3 seagrass

4 -64.753864 17.776698 2

5 -64.754026 17.777177 1.1

6 -64.753510 17.777275 0.7 Thalassia (seagrass)

7 -64.752949 17.777316 0.9 Halimeda (algae)

8 -64.757206 17.777837 1.8

9 -64.757500 17.778006 0.4

10 -64.757503 17.778358 0.5 seagrass

11 -64.755971 17.778615 1.6

12 -64.755939 17.779168 1.7

13 -64.753091 17.779637 0.7

14 -64.754529 17.779647 1.8

15 -64.754276 17.779749 1.5 Thalassia & Syringodium (seagrass)

16 -64.758710 17.780025 2

17 -64.758293 17.780294 2.5

18 -64.757053 17.780513 2

19 -64.753441 17.772506 0.02 benthic: algae mat, Rhizophora mangle (red mangrove)

20 -64.758675 17.770331 mud

21 -64.759827 17.772779 0.7 algae

22 -64.759638 17.773741 seagrass

23 -64.752188 17.774306 algae

24 -64.756236 17.774937 continuous seagrass

25 -64.753257 17.775287 1.6 10-90% algae

26 -64.754073 17.775504 10-90% algae, seagrass approx 20 m NE

27 -64.758532 17.775824 algae shallower than 2 m, mud deeper

28 -64.754830 17.776538 algae

29 -64.754356 17.776697 1.9 algae

30 -64.754058 17.777643 seagrass

31 -64.759067 17.777738 seagrass

33 -64.753208 17.779056 2 seagrass

34 -64.758443 17.779335 seagrass wrack

Appendix E. Mapping Field Notes and Bathymetry Measurements from Sites 

Visited During Ground Truth Activities
109

Appendix E. Ground Truth Points

Site Longitude Latitude Depth

(m) Field Notes

35 -64.758728 17.779361 scattered bedrock

36 -64.757406 17.780485 Thalassia & Syringodium (seagrass)

38 -64.755772 17.780596 2.5 rubble patches with some seagrass 

39 -64.754481 17.780716 live patch reef with wood planks and seagrass around margins

40 -64.756538 17.780948 mostly dead elkhorn, with seagrass growing on top. Some live coral

41 -64.757972 17.780993 patch reef or colonized bedrock

44 -64.757021 17.781306 large live elkhorn & dead and down coral

45 -64.757411 17.781320 algae

46 -64.758591 17.781442 sand

51 -64.756524 17.782275 scattered coral

54 -64.751322 17.782474 reef rubble

55 -64.751390 17.782712 seagrass ring. Approx 30 m E is also seagrass

58 -64.751537 17.782998 reef rubble

59 -64.749426 17.783171 reef rubble to bedrock @ point of land

60 -64.751209 17.783427 reef rubble from beach to just beyond breakers

61 -64.749187 17.783567 from cliff looks like bedrock

62 -64.748040 17.783890 from cliff looks like bedrock

63 -64.756405 17.783947 linear reef

64 -64.757508 17.785768 no algae/sg - patch reef

68 -64.756897 17.787760 reef with sand channels not oriented in any direction - patch reef?

69 -64.751274 17.787810 patches of dark red encrusting sponge

70 -64.756130 17.788557 linear reef

71 -64.747274 17.790327 linear reef

72 -64.750097 17.790987 no spur and groove. Linear reef

73 -64.749775 17.791391 linear reef

74 -64.748485 17.791911 not spur and groove

75 -64.758832 17.771059 0.6 algae shallower than 2 m, mud deeper

76 -64.759481 17.771279 0.7 no sand, no mangrove at adjacent land

77 -64.759619 17.772709 2.2 algae shallower than 2 m, mud deeper

79 -64.759453 17.773341 1.4

80 -64.758057 17.773415 1.6 algae shallower than 2 m, mud deeper

81 -64.759133 17.773904 1.5

82 -64.753304 17.774504 0.8 10-90% alage

83 -64.757242 17.774584 1.8 15m West is seagrass. Point is seagrass/algae mix 10-90%

84 -64.758466 17.775028 3.3
110

Appendix E. Ground Truth Points

Site Longitude Latitude Depth

(m) Field Notes

85 -64.753901 17.775091 2.1 algae shallower than 2 m, mud deeper

86 -64.757176 17.775130 2.6 algae shallower than 2 m, mud deeper

87 -64.756494 17.775390 2 algae

88 -64.758248 17.775654 3

90 -64.756532 17.775863 3.8 mud

92 -64.759861 17.777175 0.2 sand w/ seagrass around margins of water.

93 -64.752717 17.777357 1 seagrass/algae mix 10-90%

94 -64.755250 17.777546 4.5

95 -64.751063 17.777695 2.5 mud

96 -64.750914 17.777843 2.3 mud

97 -64.750800 17.777973 2.3 mud

98 -64.755562 17.778067 4.3

99 -64.755824 17.778114 4.5 sand. Northward goes to algae to algae/seagrass to seagrass

100 -64.756584 17.778129 2.1 mostly seagrass. Some algae

101 -64.752628 17.779653 0.8 algae

102 -64.756676 17.779878 1.8 mostly thalassia (seagrass)

104 -64.758291 17.780506 2.5 syringodium (seagrass)

105 -64.751275 17.779468 1.6 mangrove is Rhizophora mangle

106 -64.764084 17.763439 paved

107 -64.756162 17.764636 pt is paved.

108 -64.760123 17.765373 black mangrove

109 -64.750215 17.765928 was shrubs, now forest. Bare soil area is gone

110 -64.761631 17.766059 forest from rd to 17.76611 64.76147. Point is in forest.

111 -64.761115 17.768437 Likely paved. Abandoned car is blocking road

112 -64.755584 17.768885 paved, sorta

113 -64.754933 17.768898 Point is in forest. Rd. is paved

114 -64.760689 17.769132 Paved. Switches to gravel @ 17.77092 64.76176

115 -64.757781 17.769690 Fringe is mixed black and white approx 3 m wide

116 -64.759840 17.770016 Blk mangrove from water to 2m in. Point is not in mangrove

117 -64.760952 17.770145 forest

118 -64.752320 17.771944 black around fringe. Upland is forest

120 -64.756636 17.772304 Point is not paved. Switches from paved to gravel at 17.77028 64.75583

121 -64.754117 17.772706 Black from pond, north to road. Road is gravel.

122 -64.760328 17.772914 No mangrove at point or to road.

123 -64.759964 17.773547 No mangrove at point or to road.
111

Appendix E. Ground Truth Points

Site Longitude Latitude Depth

(m) Field Notes

124 -64.760582 17.774408 Unpaved

125 -64.751547 17.775103

Red mang around pond interspersed w/dead. Red along beach on bay 

side. White fringe along path to bay.

126 -64.763411 17.775103 Paved

127 -64.762432 17.775362 Unpaved (dark gravel)

129 -64.761523 17.776355 Unpaved (gravel). Switches to paved at 17.77683 64.76144

130 -64.750957 17.776695 Forest

131 -64.751000 17.777075 Vegetated field with some scattered shrubs

132 -64.750396 17.777286 Shrubs

133 -64.749274 17.777873 Switches from unpaved to paved away from the water

135 -64.760842 17.777978 Sparse forest just W of corner. Vegetated field at corner. Rd. is unpaved

136 -64.759560 17.778142

Point is in forest. But along road on both sides is black and white 

mangroves

137 -64.761711 17.778458 Vegetated field

138 -64.749630 17.778503 Shrubs

139 -64.760653 17.778532 Point is in sparse forest in vegetated field. Bushes along road.

140 -64.758511 17.778856 Vegetated field mixed with bushes.

141 -64.759400 17.778877 Unpaved

142 -64.750125 17.779041 vegetated field, was probably dead grass before

143 -64.749472 17.779724 Shrubs without leaves in vegetated field. Rd. is paved

144 -64.751342 17.780001 Point is in shrubs. Toward road is vegetated field.

145 -64.750960 17.780446 Shrubs without leaves in vegetated field.

146 -64.750707 17.780920 Trees bordered by shrubs without leaves

147 -64.747780 17.781190 Point is in shrubs. Road is paved.

148 -64.747426 17.781203 Shrubs interspersed with bare areas.

149 -64.752124 17.781409 Forest

150 -64.760235 17.764871 Upland forest

151 -64.760008 17.765765 Black mangrove on both sides of trail & around pond. White along road.

152 -64.761429 17.766028 Pt. is in black mangrove. From pt to rd. is also black. Lots of land crabs 

153 -64.760718 17.766065 black mangrove

154 -64.760539 17.766911 black and white mixed

155 -64.759401 17.767305 white along dike

156 -64.760809 17.767339 point is in upland forest

157 -64.757336 17.767804 point is in forest, but black mangrove frings on land side of dead zone

158 -64.758797 17.767870 black mangrove fringe approx 4 m wide to upland forest transition
112

Appendix E. Ground Truth Points

Site Longitude Latitude Depth

(m) Field Notes

159 -64.760289 17.768165 Mostly white mangrove. Forest is approx 6 m wide along road.

160 -64.760096 17.769472

Point is on edge of mangrove/forest interface. From pt to water is black 

mangrove.

161 -64.759515 17.769904 Red is approx 3 m wide, switches to black and white mixed

162 -64.759635 17.769932 mostly black, mixed w/white.

163 -64.752715 17.771367 Red mangrove

164 -64.752603 17.771400 Red mangrove along fringe. No black or white

165 -64.758573 17.771433 Point is on red to black transition.Red along shore.

166 -64.758383 17.771495 Point is in black mangroves

167 -64.760317 17.771795 Red mangroves

168 -64.760167 17.771849

Red mangrove from point toward N. South along water there are no 

mangroves at all.

169 -64.753484 17.772256 Red mangrove. Black on fringe on W side of bare area

170 -64.754080 17.772416 All black mangrove around pond. Bare area is sand

171 -64.757450 17.772518 Black mangrove approx 10 m wide along fringe

172 -64.751928 17.772787 Black mangrove

173 -64.752738 17.772912 Red mangrove along water.

174 -64.753808 17.773214 Red mangrove fringe approx 8 m wide. Switches to sparse black

175 -64.760145 17.773355 Red mangrove

176 -64.751990 17.773389 Pt is on transition from red to white mang. No black mangrove

177 -64.757582 17.773403 Red mangrove along water. Switch to black mangrove around pond

178 -64.752032 17.774177

Pt. is on transition from blk mangrove to forest. Water's edge is red 

mangrove.

179 -64.754381 17.774457 Red mangrove. 

180 -64.757056 17.774691 No mangrove or dead mangrove. Bedrock

181 -64.760783 17.775357

White mangrove along marina road about 3 m wide. Red from water to 

white mangrove.

182 -64.759795 17.775370 Point is at red mangrove. White fringe along road approx 3 m wide.

185 -64.751331 17.775675

Red mang.around margin of pond, some dead. Along path is 3 m fringe 

of white, red along beach at bay side.

186 -64.759522 17.775794 No mangrove around path to water

187 -64.759329 17.775925 Red mangrove by water

190 -64.759409 17.777971 Red mangrove from beach to 17.77802 64.75931

191 -64.758688 17.778137 Red mangrove from beach to about 7-10 m inland

193 -64.750368 17.778823 Red mangrove

194 -64.751707 17.780146 Not mangrove

195 -64.752576 17.781166

White mangrove 2-3 m toward land from water. Red and white mixed all 

the way around pond.
113
114

Appendix F. Data Products List

Appendix F. List of Data Products From This Project Available From NPS

Product Description Format (s)

Aerial Photographs hard copy prints, hard copy diapositives, digital

1970's Orthorectified Mosaic imagine file

1988 Orthorectified Mosaic imagine file

1992 Orthorectified Mosaic imagine file

2000 Orthorectified Mosaic imagine file

1970's map of seagrass and mangrove distribution GIS shapefile

1988 map of seagrass and mangrove distribution GIS shapefile

1992 map of seagrass and mangrove distribution GIS shapefile

2000 map of benthic and land cover GIS shapefile

Bathymetry Grid grid file
115

Acknowledgements

Acknowledgements

This report could not have been possible without numerous people who generously shared data 

and information, and provided comments during review. Many thanks to the following people:

Anchor Dive Center Staff

Ursula Anlauf

Richard Berey

Ann Borowik

William Cissel

Mary Lou Coulston

Barry Devine

Laurie Dunton

Louis Florit

Jim Hendee

Dennis Hubbard

Aaron Hutchins

Carol Cramer-Burke

Douglas McNair

Derek Manzello

Violetta Mayor

Rudy O’Riley

Linda Pikula

Bruce Potter

Joan Rikon

Bill Rohring

Andy Shepard

Syed Syedali

William Tobias

Wes Toller

Hank Tonnemacher

115
United States Department of Commerce

Carlos M. Gutierrez

Secretary

National Oceanic and Atmospheric Administration

Vice Admiral Conrad C. Lautenbacher, Jr. USN (Ret.)

Under Secretary of Commerce for Oceans and Atmosphere

National Ocean Service

Richard W. Spinrad

Assistant Administrator for Ocean Service and Coastal Zone Management

United States Department of the Interior

Gale A. Norton

Secretary

National Park Service

Fran P. Mainella

Director

Southeast Regional Office

Patricia Hook

Director