https://doi.org/10.7289/V5/SP-PIFSC-17-003
CORAL REEF 

ECOSYSTEMS

of the Pacific Remote Islands Marine National Monument 

a 2000–2016 Overview

Shannon Boyle1, Vanessa De Anda1, Kara Koenig1, Erin O’Reilly1, Monique Schafer1, Tomoko Acoba2, 

Amanda Dillon2

, Adel Heenan2, Thomas Oliver2, Dione Swanson2, Bernardo Vargas-Ángel2,

Mariska Weijerman2

, Linda Wegley Kelly3, Russell Brainard4, Ivor Williams4

1 Bren School of Environmental Science and Management, University of California, Santa Barbara, CA, USA

2 Joint Institute for Marine and Atmospheric Research, University of Hawai‘i at Mānoa, Honolulu, HI, USA

3 San Diego State University, San Diego, CA, USA

4 Coral Reef Ecosystem Program, NOAA Pacific Islands Fisheries Science Center, Honolulu, HI, USA
The mission of the National Oceanic and Atmospheric Administration (NOAA)’s Pacific Islands Fisheries Science Center (PIFSC) is to conduct 

high-quality, timely research to support the stewardship of fisheries resources, protected species, and ecosystems in the central and western 

Pacific Ocean.

Front cover: Giant clams at Kingman Reef, Photo: NOAA Fisheries.

To obtain copies of this document, contact PIFSC:

NOAA Pacific Islands Fisheries Science Center

1845 Wasp Blvd. Building 176

Honolulu, HI 96818

(808) 725-5360

An online version is available at https://doi.org/10.7289/V5/SP-PIFSC-17-003.

Unless otherwise indicated, photographs in this publication are in the public domain. For all NOAA photos, please credit NOAA Fisheries.

This document may be referenced in the following manner:

Boyle, S., V. De Anda, K. Koenig, E. O’Reilly, M. Schafer, T. Acoba, A. Dillon, A. Heenan, T. Oliver, D. Swanson, B. Vargas-Ángel, M. Weijerman, 

I. Williams, L. Wegley Kelly, R. Brainard (2017). Coral reef ecosystems of the Pacific Remote Islands Marine National Monument: a 2000–2016 

overview. NOAA Pacific Islands Fisheries Science Center, PIFSC Special Publication, SP-17-003, 62 p.

Back cover: Grey reef sharks (Carcharhinus amblyrhynchos) and barracudas at Jarvis Island, Photo: NOAA Fisheries/James Morioka.
This booklet provides an overview of key findings about 

spatial patterns and temporal trends of the coral reef 

ecosystems observed during NOAA’s Pacific Reef Assessment 

and Monitoring Program research surveys conducted in the 

U.S. Pacific Remote Islands Marine National Monument from 

2000 to 2016 by the Coral Reef Ecosystem Program of the 

NOAA Pacific Islands Fisheries Science Center with financial 

support from NOAA’s Coral Reef Conservation Program. 

All data sets used in this booklet are documented at NOAA 

InPort Metadata catalog at https://inport.nmfs.noaa.gov/

inport/hierarchy/select/36446 and will soon be archived at 

the NOAA National Centers for Environmental Information. 

For more in-depth information, consult the scientific papers 

referenced throughout this booklet.

TABLE OF CONTENTS

02 | HISTORY OF CORAL REEF ECOSYSTEM MONITORING 

BY CREP

06 | THE PACIFIC REMOTE ISLANDS MARINE NATIONAL 

MONUMENT

12 | METHODS OVERVIEW

17 | PACIFIC REMOTE ISLANDS IN A PACIFIC-WIDE CONTEXT

29 |

41 | ISLAND HIGHLIGHTS

56 | CONCLUSIONS

57 | ACKNOWLEDGEMENTS

PACIFIC REMOTE ISLANDS IN A MONUMENT CONTEXT

18 Oceanography

23 Benthic Community

24 Fish Community

27 Microbial Community

30 Benthic Composition

35 Fish Composition

39 Integrating Ecosystem Components

42 Baker, Howland, and Jarvis Islands

48 Johnston Atoll

50 Kingman Reef

53 Palmyra Atoll

54 Wake Atoll

Spotband butterflyfish (Chaetodon punctofasciatus) at Wake Atoll, 

Photo: NOAA Fisheries/Andrew E. Gray. 

58 | ACRONYMS

59 | REFERENCES
2

HISTORY OF CORAL REEF ECOSYSTEM 

MONITORING BY CREP
3

A primary mission of CREP is to provide high-quality, scientific 

information about the status and trends of coral reef ecosystems 

of the U.S. and U.S.-affiliated Pacific Islands to the public, 

resource managers, policymakers, and scientists to support 

ecosystem-based management and conservation of coral reefs 

on local, regional, national, and international levels.

National coral reef conservation efforts in the United States were advanced in 1998, with 

the issuance of Executive Order #13089 by President Clinton to “preserve and protect the 

biodiversity, health, heritage, and social and economic value of U.S. coral reef ecosystems and 

the marine environment.” This executive order established the U.S. Coral Reef Task Force and 

emphasized the need to undertake a comprehensive approach to research, map, and monitor 

all U.S. coral reef ecosystems. In 2000, the U.S. Coral Reef Task Force developed the National 

Action Plan to Conserve Coral Reefs (USCRTF, 2000) and the Coral Reef Conservation Act of 

2000 laid out a national framework to address the degradation of U.S. coral reef ecosystems and 

other coral reef conservation issues (16 U.S. Code §6401[2000]). The Coral Reef Conservation 

Act also led to the creation of the national Coral Reef Conservation Program under the direction 

of the Secretary of Commerce. This legislation requires NOAA to conduct scientific research, 

mitigation, and outreach activities that directly contribute to the conservation of coral reef 

ecosystems. In response to mandates and with the support of NOAA’s Coral Reef Conservation 

Program, the NOAA Pacific Islands Fisheries Science Center initiated the Pacific Reef Assessment 

and Monitoring Program (Pacific RAMP) in early 2000, and established the Coral Reef Ecosystem 

Program (CREP) in 2001. In 2002, NOAA, in cooperation with the U.S. Coral Reef Task Force, 

released A National Coral Reef Action Strategy to address and reduce threats to coral reefs 

worldwide. 

Previous page: Threadfin butterflyfish (Chaetodon auriga) at Kingman Reef, Photo: NOAA Fisheries/Kevin Lino. 

Right: Giant blue clams at Kingman Reef, Photo: NOAA Fisheries. 
4

Figure 1. CREP monitors the status and trends of coral reef ecosystems of ~40 islands, atolls, 

and shallow banks spanning the waters of the Pacific Remote Island Areas, main Hawaiian 

Islands, Northwestern Hawaiian Islands, Mariana Archipelago, and American Samoa. 

Gray areas represent the U.S. Exclusive Economic Zones and the white areas represent the 

Pacific Remote Islands Marine National Monument, Papahānaumokuākea Marine National 

Monument, Marianas Trench Marine National Monument, and Rose Atoll Marine National 

Monument.

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!!

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0 1,250 2,500 KM

NORTHWESTERN

HAWAIIAN ISLANDS

MAIN HAWAIIAN

ISLANDS

PACIFIC REMOTE

ISLAND AREAS

AMERICAN

SAMOA

MARIANA 

ARCHIPELAGO

Marine Monument Boundary

Exclusive Economic Zone

To fulfill this mission, CREP conducts a comprehensive suite of 

interdisciplinary monitoring and research activities, including 

habitat mapping, oceanographic and climate studies, and longterm monitoring of multiple components of coral reef ecosystems 

in the U.S. Pacific islands (Fig. 1). CREP has conducted biennial Pacific 

RAMP surveys from 2000 to 2012, and triennial surveys from 2012 

to 2016, in each of the U.S. Pacific and U.S.-affiliated management 

jurisdictions. Using consistent survey methodologies across over 

40 Pacific island, atoll, and shallow-bank ecosystems enables 

comparative analyses across diverse gradients of biogeography, 

environmental conditions, and human uses. Accurate and upto-date characterizations of coral reef ecosystems are necessary 

to inform ecosystem-based management and evaluate the 

effectiveness of management actions for sustainable use and longterm conservation. Pacific RAMP survey results are also used to 

improve our understanding of ecosystem processes and the causeand-effect mechanisms that influence the status and resilience of 

coral reefs. 

The initial exploratory surveys of the Pacific RAMP in 2000–2003 

provided the first-ever baseline characterizations of the biodiversity, 

abundance, and distributions of coral reef habitats and associated 

resources across the U.S. Pacific Islands region. Those early surveys 

and the inherent logistical and budgetary constraints posed by 

the vast and remote U.S. Pacific Islands region have shaped many 

aspects of the long-term Pacific RAMP. By collecting biennial and 

triennial reef ecosystem ‘snapshot’ surveys during ship-based research expeditions, the Pacific RAMP was designed to observe the status and 

detect long-term changes in reef ecosystem conditions over periods of many years to several decades. They provide an improved understanding 

of island- and region-scale conditions that serve as background context to support more frequent and finer-scale local monitoring in populated 

island communities and jurisdictions designed to evaluate effectiveness of local management actions. 
5

Over the past few decades, there has been a steadily increasing shift toward 

ecosystem-based management in the United States and globally. Ecosystembased management requires efforts to monitor holistic ecosystem indicators, 

which include information on the status and trends of species, habitats, and 

environmental conditions in the biophysical and human systems. The goal of 

these ecosystem-based monitoring programs is to balance ecological scales 

with management scales so that monitoring meets the needs of management 

decision-making processes. In 2010, NOAA’s Coral Reef Conservation Program 

unified NOAA’s monitoring efforts by establishing the National Coral Reef 

Monitoring Program (NCRMP) which collects data across biological, climatic, and 

socio-economic domains. For the U.S. Pacific Islands, NCRMP augmented the 

ongoing Pacific RAMP surveys with long-term socio-economic surveys aimed 

at better establishing linkages between the ecological status of coral reefs and 

the human uses and benefits of coral reef ecosystems. Over the past 16 years, 

NOAA’s Pacific RAMP and NCRMP have been able to continually adapt to evolving 

management needs and changing political environments without detracting 

from the overarching goal of long-term coral reef ecosystem status and trends 

monitoring (Heenan et al., 2016).

As is typical for any long-term monitoring effort, CREP survey protocols have been 

refined over time to match the priority information needs for management given 

the resources available for monitoring. For example, ecological survey methods 

were refined to reduce observer variability and expand the suite of monitored 

indicators to assess impacts of ocean acidification. To date, CREP has conducted 

38 Pacific RAMP survey cruises, including nine to the Pacific Remote Islands 

Marine National Monument. Information on individual cruises can be found in 

the cruise reports for these expeditions at www.pifsc.noaa.gov/library/cruise.php. 

A monitoring report compiling the results of the past Pacific RAMP cruises (2000–

2017) is currently in production.

Red pencil and long-spine sea urchins at Kingman Reef, Photo: NOAA Fisheries.
6

THE PACIFIC REMOTE ISLANDS 

MARINE NATIONAL MONUMENT
7

The U.S. Pacific Remote Islands encompass seven islands and atolls scattered across the central Pacific, spanning natural gradients in 

oceanographic conditions. The islands and reefs can be divided into three groups based on ecological characteristics: (1) the equatorial 

upwelling islands, Baker, Howland, and Jarvis Islands; (2) the central transition islands, Kingman Reef and Palmyra Atoll; and (3) the northernmost 

oligotrophic islands, Johnston and Wake Atolls (Fig. 2). The equatorial islands are especially productive as they benefit from the combined 

effects of regional equatorial upwelling and localized topographic upwelling of the subsurface Equatorial Undercurrent that collectively bring 

cool, nutrient-rich waters to the sunlit surface where photosynthesis thrives. In contrast, the northernmost islands are situated in the nutrientpoor waters of the central gyre characterized by low biological productivity. The central transition islands, located at the northern edge of the 

enhanced productivity region, experience a moderate level of biological productivity (Miller et al., 2008). 

Figure 2. Pacific Remote Islands Marine National Monument boundaries and bathymetry (Becker 2009, Smith and 

Sandwell 1997) © 2008 The Regents of the University of California.

To protect and preserve the diversity and 

abundance of ocean life in these waters, all 

seven islands and atolls were established as 

the Pacific Remote Islands Marine National 

Monument (PRIMNM) by Presidential 

Proclamation #8336 in January 2009. To 

further care for and manage historic and 

scientific objects, such as the pelagic 

ecosystem, deep sea corals, and seamounts, 

the Monument protection was expanded 

around Jarvis Island, Johnston Atoll, and 

Wake Atoll by Presidential Proclamation 

#9173 in 2014. The Monument area is 

approximately 370,000 square nautical 

miles [nm2

] (1,269,065 square kilometers 

[km2

]). ^_

^_

^_

^_

^_

^_

^_

0 500 1,000

km o

BATHYMETRY (m)

- 0

-9,000

Equatorial Upwelling Islands

Central Transition Islands

Northernmost Oligotrophic Islands

PRIMNM Monument Boundaries

ECOLOGICAL GROUPING

WAKE

JOHNSTON

KINGMAN PALMYRA

JARVIS

BAKER

HOWLAND

Previous page: Grey reef sharks (Carcharhinus 

amblyrhynchos) and schools of anthias at Jarvis Island, 

Photo: NOAA Fisheries/Kelvin Gorospe.
8

ISLAND BAKER HOWLAND JARVIS KINGMAN PALMYRA JOHNSTON WAKE

Relative Shape 

and Size

Land Area (km2

)

Seafloor Area 

0-30 m (km2

)

Reef Area 

0-30 m (km2

)

Seafloor Area 

30-150 m (km2

)

Monument 

Area (km2

)

Population

Age (million years)

Ecological 

Grouping

Island Chain

2 2 4 0 2 3 7

4 3 4 48 53 194 19

4 2 4 37 42 94 13

2 2 3 37 9 49 3

51,658 315,085 53,503 442,447 407,785

0 0 0 0 4-20 4-5 94

~124 ~125 ~111 ~112 ~112 ~171

Equatorial 

Upwelling Island

Equatorial 

Upwelling Island

Equatorial 

Upwelling Island

Central 

Transition Island

Central 

Transition Island

Northernmost

Oligotrophic Island

Northernmost

Oligotrophic Island

Phoenix Islands Phoenix Islands Line Islands Line Islands Line Islands Line Islands Marshall Islands

>160

30-m contour

Table 1. Summary table of island characteristics across the PRIMNM. Blue area represents the 30-m depth contour around the islands. Colors indicate land area. All areas calculated 

using geographic information systems techniques. Monument areas were calculated by NOAA’s Pacific Island Regional Office. Population estimates were collected from both the Federal 

Fish and Wildlife Services and Wikipedia. The ages of Baker, Howland, Jarvis, Kingman, and Palmyra were obtained from the Seamount Biogeosciences Network (https://earthref.

org/SC/#top). Age of Johnston was determined through Fish and Wildlife Service documentation (http://www.fws.gov/refuge/Johnston_Atoll/about.html), and the age of Wake was 

obtained from the Pacific Islands Benthic Habitat Mapping Center (http://www.soest.hawaii.edu/pibhmc/pibhmc_pria.htm). 

Each of the Pacific Remote Islands is also unique in terms of size. Wake is the largest of the Pacific Remote Islands with a land area of 

approximately 7 km2

. The rest of the Pacific Remote Islands have land areas less than 5 km2. While these islands are small in size, reef areas range 

from approximately 2 km2

 surrounding Howland to 94 km2 surrounding Johnston (Table 1). With the exception of Johnston, Palmyra and Wake, 

which have small mission-focused human presence, the Pacific Remote Islands are currently uninhabited. 
9

0 1 2 4

km

0 1 2 4

km

0 1 2 4

km

0 2.5 5 10

km

0 2.5 5 10

km 0 1 2 4

km

0 2.5 5 10

km

The Pacific Remote Islands have a rich human history that dates back to Polynesian voyages through these waters. In the mid-1800s, some of 

the islands experienced active whaling and guano mining. Other islands were actively utilized in World War II and the Cold War. Currently on 

Wake Atoll, there is a U.S. Air Force installation with a resident military population of ~94; on Palmyra Atoll there is a contingent population of 

~30 researchers working seasonally with the U.S. Fish and Wildlife Service and The Nature Conservancy as part of the Palmyra Atoll Research 

Consortium; and on Johnston Atoll there is a small team of volunteers working with the U.S. Fish and Wildlife Service to eradicate invasive ants. 

Due to their remoteness and relative absence of significant human impacts, the PRIMNM is home to some of the least impacted coral reef 

ecosystems in the world. However, despite their remote location, relatively intact condition, and on-going conservation management efforts, 

the coral reefs remain vulnerable to global changes in climate. Studies in the PRIMNM present a unique opportunity to understand ecological 

responses to climate change and ocean acidification in the absence of direct confounding anthropogenic impacts, such as overfishing and 

land-based pollution, which are common in most other coral reefs around the world (Friedlander et al., 2010). 

Baker Island Howland Island Jarvis Island Kingman Reef

Palmyra Atoll Johnston Atoll Wake Atoll

Satellite images of the seven islands and 

atolls in the PRIMNM at various scales 

(© DigitalGlobe Inc. All rights reserved, 

Johnston Atoll: NASA/U.S. Geological 

Survey).
10

KINGMAN

1934 Franklin D. Roosevelt placed 

Kingman under naval administration

1935 U.S. Bureau of Air Commerce 

stationed supply ship in the lagoon 

as a seaplane base

1938 Seaplane base abandoned

1941 Franklin D. Roosevelt declared 

Kingman a naval defense sea area

1830-1870 Active whaling

2009 PRIMNM established

2014 Fishing vessel removed

2001 Named U.S. National Wildlife 

Refuge

2001-present Coral Reef Ecosystems 

Fishery Management Plan: 

designated no-take MPA

2007 Fishing vessel grounded on reef

JARVIS

1830-1870 Active whaling

1935-1942 Hui Panala‘au occupation: 

students from Kamehameha Schools 

sent to establish U.S. territories

1950’s Visited by whalers who 

harvested marine life for ship supplies

1974 Named U.S. National Wildlife 

Refuge

2001-present Coral Reef Ecosystems 

Fishery Management Plan: 

designated no-take MPA

2009 PRIMNM established

1858-1879 Guano mining

2014 PRIMNM expanded

HOWLAND

1830-1870 Active whaling

1935-1942 Hui Panala‘au occupation: 

students from Kamehameha Schools 

sent to establish U.S. territories

1943-1946 U.S. military present

1950’s Visited by whalers who 

harvested marine life for ship supplies

1962 Reef bombed by U.S. Atomic 

Energy Commission to use land as 

nuclear site

1974 Named U.S. National Wildlife 

Refuge

2001-present Coral Reef Ecosystems 

Fishery Management Plan: 

designated no-take MPA

2009 PRIMNM established

1859-1871 Peak guano mining

BAKER

1830-1870 Active whaling

1866-1872 Peak guano mining

1935-1942 Hui Panala‘au occupation: 

students from Kamehameha Schools 

sent to establish U.S. territories

1943-1946 U.S. military present— 

more than 15,000 men built and 

maintained airstrip

1965 Operation Magic Sword: 

biological carrier experiment 

1974 Named U.S. National Wildlife 

Refuge

2001-present Coral Reef Ecosystems 

Fishery Management Plan: 

designated no-take Marine Protected 

Area (MPA)

2009 PRIMNM established

1850

1900

1950

2000

TIMELINE
11

1934 Franklin D. Roosevelt placed Wake under 

naval administration

1935 Pan American Airways constructed 

“PAAville” village, made major alterations 

for airport

1941-1945 Japanese took control; Wake occupied 

by ~4,000 Japanese soldiers while U.S. bombed 

atoll

1975 Vietnamese refugee camp for more than 

8,000 refugees

1985 Designated U.S. National Historic Landmark

2014 PRIMNM expanded

1945-present Japanese surrendered and Wake 

placed under jurisdiction of U.S. Navy; used as 

missile launch test site

2009 PRIMNM established

2009 Named U.S. National Wildlife Refuge

2001-present Coral Reef Ecosystems Fishery 

Management Plan: designated low-use MPA

WAKE

1858-1910 Guano mining

1926 Named U.S.National Wildlife Refuge

1934 Franklin D. Roosevelt placed Johnston under 

naval administration

1939-1942 Construction for U.S. military 

operations— enlarged island, built islet, dredged 

coral

1958 Radioactive material weapon testing began 

1962 Spilled americium and plutonium over 

atoll—raked sand into “Mount Pluto” pile

1963-1964 Dredged coral to enlarge island, built 

runway, built two islands

1965 Operation Magic Sword: biological carrier 

experiment 

1971 U.S. transferred chemical munitions from 

Japan to Johnston for demilitarization

1985 Construction of Johnston Atoll Chemical 

Agent Disposal System (JACADS) facility

1990 JACADS began destruction of 6% of nation’s 

original stockpile of chemical agents on Johnston

2001 JACADS ends stockpile elimination; over 4 

million lbs. of nerve and mustard agents destroyed 

without releasing into the environment

2001-present Coral Reef Ecosystems Fishery 

Management Plan: designated low-use MPA

2009 PRIMNM established

2010 Yellow crazy ants detected; eradication and 

monitoring ongoing

2014 PRIMNM expanded

PALMYRA JOHNSTON

1830-1870 Active whaling

1991 Fishing vessel grounded on reef

2009 PRIMNM established

2014 Longline fishing vessel and barge removed

1922 Expansion of existing coconut plantation

1941-1945 U.S. military present; Palmyra housed 

~6,000 men, dredged channel, built causeways to 

connect islets, stripped vegetation for runway

2000 Purchased by The Nature Conservancy; 

established Palmyra Atoll Research Consortium

2001 Named U.S. National Wildlife Refuge

2011 Rat eradication begins

2001-present Coral Reef Ecosystems Fishery 

Management Plan: designated low-use MPA

2013 Declared “rat free” by U.S. Fish & Wildlife 

Service 

1850

1900

1950

2000

TIMELINE

Figure 3. Timeline of historical events for each island of the Pacific Remote Islands Marine National Monument (PRIMNM). 
12

METHODS OVERVIEW
13

Interdisciplinary biological, physical, and chemical surveys were 

conducted to document the status and trends of the conditions of, and 

processes influencing, the coral reef ecosystems around each of the 

Pacific Remote Islands. From 2000 to 2016, CREP conducted 10 Pacific 

RAMP cruises to Jarvis; 9 cruises to Baker, Howland, Kingman, and 

Palmyra; 6 cruises to Johnston; and 5 cruises to Wake (Fig. 4). 

CREP scientists have collected spatial and temporal observations of key 

oceanographic parameters to document time-varying oceanographic 

conditions that influence ecological processes and ecosystem health 

(Hoeke et al., 2009). The dominant physical drivers influencing coral 

reefs are temperature, salinity, ocean currents, and waves that are 

measured using both moored instruments for time series observations 

and profiling instruments that provide information about conditions at 

different depths. The dominant chemical parameters influencing coral 

reefs are carbonate chemistry, dissolved oxygen, and nutrients that are 

measured with recording instruments and water samples.

Figure 4. Timeline of Pacific RAMP research cruises to the PRIMNM.

PACIFIC RAMP

Fusilier damselfish (Lepidozygus tapeinosoma) and several species of anthias 

(Luzonichthys whitleyi and Pseudanthias bartlettorum) at Jarvis Island, Photo: 

NOAA Fisheries/Kevin Lino. Previous page: Diver takes photoquads above the 

reef at Baker Island, Photo: NOAA Fisheries/Kelvin Gorospe.

2000 BAKER, HOWLAND, JARVIS, KINGMAN, PALMYRA 

2004 BAKER, HOWLAND, JARVIS, KINGMAN, PALMYRA, JOHNSTON 

2005 WAKE

2007 WAKE

2009 WAKE

2011 WAKE

2014 WAKE

2016 JARVIS

2003

2013

2001 BAKER, HOWLAND, JARVIS, KINGMAN, PALMYRA 

2002 BAKER, HOWLAND, JARVIS, KINGMAN, PALMYRA 

2006 BAKER, HOWLAND, JARVIS, KINGMAN, PALMYRA, JOHNSTON 

2008 BAKER, HOWLAND, JARVIS, KINGMAN, PALMYRA, JOHNSTON 

2010 BAKER, HOWLAND, JARVIS, KINGMAN, PALMYRA, JOHNSTON 

2012 BAKER, HOWLAND, JARVIS, KINGMAN, PALMYRA, JOHNSTON 

2015 BAKER, HOWLAND, JARVIS, KINGMAN, PALMYRA, JOHNSTON 
14

Originally, rapid ecological assessment (REA) surveys were 

conducted along belt transects at semi-fixed and haphazardly 

selected sites. In 2008, the sampling design and method 

for the REA fish surveys were changed to a depth-stratified 

random approach (with shallow (0–6 m), mid (> 6–18 m), 

and deep (> 18–30 m) depth strata) using a stationary-pointcount (SPC) method to obtain more representative estimates 

of abundance, size, and diversity of reef fishes on shallow 

(< 30 m) reefs at island or atoll scales (Ayotte et al., 2015). In 

SPC surveys, some larger fish, such as sharks and jacks, are 

sometimes attracted to divers resulting in overestimation of 

abundance. The biomass of these groups is instead reported 

more accurately using the towed-diver survey methodology. 

The REA benthic surveys were changed from semi-fixed 

and haphazardly selected sites in mid-depths (6–18 m) to a 

depth-stratified random sampling (StRS) design covering the 

same depth strata as the REA fish surveys in 2013. The survey 

methods employed by CREP in the Pacific Remote Islands 

during the period of 2000–2017 (Fig. 5), are described in 

greater detail in the Coral Reef Ecosystem Monitoring Report 

for the Pacific Remote Islands 2000–2017 (in prep). 

Since 2009, microbial community data have been collected during all Pacific RAMP cruises in collaboration with San Diego State University to 

examine relationships between the metabolic energy requirements of microbes and those of reef fishes. For the Pacific Remote Islands, our 

colleagues collected and filtered large volumes of seawater adjacent to the coral reefs at a subset of our monitoring sites to determine the 

abundance and diversity of microbes present. Using standard equations (McDole et al., 2012), we converted the abundances of microbes and 

reef fishes in a 10 m3

 volume of reef water to their metabolic energy requirements, or how much energy fishes and microbes use to live. With 

these two values, we calculate the microbialization score as the microbial metabolic energy needs of a coral reef divided by the total metabolic 

energy needs of fish and microbes (McDole et al., 2012). This work has shown that in more human-impacted ecosystems, microbes dominate 

the food web, or specifically, the metabolic energy that moves between reef organisms as they eat each other.

AUTONOMOUS REEF MONITORING STRUCTURE (ARMS) – biodiversity

BIOEROSION MONITORING UNIT (BMU) – coral reef removal

CALCIFICATION ACCRETION UNIT (CAU) – coral reef growth

RAPID ECOLOGICAL ASSESSMENT (REA) – detailed species-level surveys of 

benthic and fish community structure

TOWED DIVER – broad surveys of benthic cover, macroinvertebrates, and large fish

TETHERED OPTICAL ASSESSMENT DEVICE (TOAD) – optical validation and 

habitat characterization

BIOLOGICAL

PHYSICAL/

CHEMICAL MAPPING

MOORED INSTRUMENTS – collection of continuous oceanographic data

CTD CASTS – measurements of conductivity, temperature and depth

WATER SAMPLES – nutrients, chl-a, carbonate chemistry

MULTIBEAM SONAR – generates bathymetry, habitat characterization

SATELLITE IMAGERY – estimates bathymetry, habitat characterization

Figure 5. Summary of CREP survey methods.

METHODS
15

Fish REA survey sites

Benthic REA survey sites

Climate stations

Towed-diver tracks

SURVEY SITES

Randomized hard-bottom 

location at depths of 0–30 m

Paired 15 m diameter cylinders

Photographs of benthos taken 

along transects

Stationary-point-count surveys of 

fishes

AREA & UNITS: RANDOM REA SITES

TRANSECT

AREA & UNITS: RANDOM REA SITES

Depths of 0–30 m

Surveys along two transects of 10 m2 

Quadrat and belt surveys along 

transects

15 m

AREA & UNITS

Depths of 0–30 m

Surveys of 1.5–2.5 km

1 m

60 m to boat

mounted 

camera

5 m wide

5 m wide

Figure 6. Schematic diagrams of Rapid Ecological Assessment (REA) method and towed-diver method. REA method shows 1. One of two divers conducting a belt-transect survey along 

a 25-m transect line (top left) and 2. One of two divers conducting a stationary-point-count (SPC) survey at a random REA site (below left). Towed-diver method shows one of two divers 

conducting a towed-diver survey (top right). An example of survey efforts and site locations at Jarvis Island (below right).

REA METHOD TOWED-DIVER METHOD

JARVIS
16

Several methods are deployed by the ocean and climate change team 

to measure the balance between the production and removal of calcium 

carbonate, a major reef building material, within the reef ecosystem. If 

bioerosion, or the removal of calcium carbonate substrate, is excessive, then 

coral destruction will exceed coral growth, which can lead to a flattening of the 

reef. Calcification accretion units (CAUs), coral cores, and carbonate chemistry 

are used to compute net ecosystem calcification and production. Coral cores, 

bioerosion monitoring units (BMUs), and carbonate chemistry are used to 

estimate net removal of calcium carbonate through bioerosion and chemical 

dissolution (Fig. 7). Collectively, these methods are used to determine the 

balance of calcium carbonate in the system, and indicate whether the reef 

will be able to persist over time.

In addition to oceanographic characteristics, information on the condition, 

abundance, diversity, and distribution of biological communities around 

these islands is collected using towed-diver surveys (Fig. 6), towed optical 

assessment device (TOAD) surveys, and rapid ecological assessments (REA) 

(Fig. 6). Towed-diver surveys encompass various habitats along a ~15-m depth 

contour and provide a broad overview of benthic cover, key macroinvertebrate 

presence, and abundance and size of large fish (> 50 cm). During each toweddiver survey, underwater video footage and still photographs of the benthos 

are collected (Kenyon et al., 2006). The TOAD surveys are used for benthic 

habitat characterization in depths greater than 30 m. REA surveys were 

adopted beginning in 2001, to gain more detailed site-specific information 

on the benthic community structure and associated fish assemblages. 

5 m

15 m

25 m

1 m









STR transects

Water samples

10 m

Water 

Sample

Reference stake

Autonomous 

Reef

Monitoring 

Structure 

5 m (ARMS)

Subsurface 

Temperature 

Recorder (STR)



Bioerosion

Monitoring 

Unit (BMU)

Calcification 

Accretion 

Unit (CAU)

- Photoquadrats

- Topographic

 site photographs

Figure 7. Climate station installation at a sample island location showing 

depths and instrumentation; additional monitoring efforts include coral cores 

and reef-area photomosaics.
17

PACIFIC REMOTE ISLANDS

IN A PACIFIC-WIDE CONTEXT
18

The CREP uses standardized survey methods across all of the U.S. Pacific Islands to enable direct comparison of reef ecosystem metrics across 

broad biogeographic, geologic, oceanographic, and human-impact gradients. To better understand the status of coral reefs in the PRIMNM on 

a broader scale, a Pacific-wide comparison was performed for oceanographic conditions, benthic community, fish community and the microbial 

community. 

OCEANOGRAPHY

Coral reef ecosystems are influenced by a diverse suite of oceanographic and meteorological factors, including but not limited to temperature, 

wind, waves, currents, nutrients, carbonate chemistry, light, and productivity. These factors all vary on daily, seasonal, interannual, and longer 

time scales. A combination of satellite-derived and in-situ information collected during Pacific RAMP surveys was analyzed to assess the 

variability of each of these factors across the U.S. Pacific Islands. Satellite observations provide broad spatial coverage and a historical context of 

surface processes, whereas in-situ observations provide subsurface measurements of the physical and chemical conditions directly influencing 

coral reef communities. Synthesis and integration of these data sets increase our understanding of the ecological processes that influence the 

status and trends in the condition of coral reefs in the PRIMNM and how the reefs of the PRIMNM compare to other coral reef ecosystems across 

the Pacific. 

Long-term averages of satellite-derived sea-surface temperature (SST) highlight some of the differences observed in oceanic conditions. Due to 

the PRIMNM’s expansive geographic range, the average SST varies considerably across the monument. Jarvis Island exhibits a noticeably cooler 

SST than its closest neighbors, Palmyra and Kingman, due to equatorial upwelling and locally intense topographic upwelling of the strong 

eastward flowing subsurface Equatorial Undercurrent (Gove et al., 2006). The northernmost Pacific island chains, the main Hawaiian Islands and 

Northwestern Hawaiian Islands, have lower SSTs (23–27 ̊C) compared to the other Pacific regions, whereas islands of the Mariana Archipelago 

and American Samoa show higher than Pacific-wide average SSTs, upwards of 28–29 ̊C (Fig. 8).

Similar to SST, satellite-derived long-term averages of chlorophyll-a concentrations (chl-a; a proxy for primary productivity) show significant 

variability across the Pacific, exhibiting highest concentrations in the equatorial region, particularly at Jarvis (0.22 mg m-3), Baker, and Howland 

Islands due to wind-driven equatorial upwelling. The lower chlorophyll-a concentrations seen at Wake and Johnston Atolls are similar to 

concentrations within the Mariana Archipelago and American Samoa (Fig. 9), which are all located in oligotrophic gyres.

Previous page: Two-spot red snapper (Lutjanus bohar) at Palmyra Atoll, Photo: NOAA Fisheries/Andrew E. Gray.
19

Figure 8. Long-term average sea surface temperature across the Pacific 

Ocean for 2003–2016, from satellite-derived data (NOAA POES AVHRR) 

for the geographic area 25°S–35°N, 135°E–145°W. White space indicates 

areas with no data. Black areas are island midpoints (http://gis.ncdc.

noaa.gov/all-records/catalog/search/resource/details.page?id=gov.

noaa.ncdc:C00284). 

Figure 9. Long-term average chlorophyll-a concentrations across the 

Pacific for 2003–2016, from satellite-derived data (National Aeronautics 

and Space Administration Aqua MODIS). White space indicates areas 

with no data. Black areas are island midpoints (https://oceandata.sci.

gsfc.nasa.gov/MODIS-Aqua/L3SMI). 

!

!

!

!

!

!

!

km 0 900 1,800 o

140°E 160°E 180° 160°W

30°N

20°N

10°N

0°

10°S

0.02

0.06

0.10

0.14

0.18

0.22

WAKE

JOHNSTON

KINGMAN

PALMYRA

BAKER JARVIS

HOWLAND

CHL-a (mg m-3)

!

!

!

!

!

!

!

o

WAKE JOHNSTON

KINGMAN

PALMYRA

BAKER JARVIS

HOWLAND

TEMP (°C)

0 875 1,750

 km

30°N

20°N

10°N

0°

10°S

20°S

150°E 170°E 170°W 150°W

20

22

24

26

28

30

32
20

Coral reefs rely on the ability of reef-building corals and crustose coralline algae to build, or calcify, and maintain the calcium carbonate structures 

that provide the three-dimensional habitat for the entire reef ecosystem. Corals precipitate mineral carbonate out of seawater and incorporate 

it into their skeletons. Their ability to calcify depends on the chemical conditions of their seawater environment. A common metric used to 

describe whether the environment is more or less conducive to calcification is the saturation state relative to the mineral aragonite (Ωarag). When 

seawater has a higher Ωarag, conditions are more favorable for calcification of reef building corals and crustose coralline algae and vice versa. 

During the last few decades, Ωarag and pH have been declining and are expected to continue to decline as the oceans absorb increasing levels of 

human-induced CO2

, in a process often referred to as ocean acidification. Using multiple methods, CREP scientists are actively monitoring both 

the changes in carbonate chemistry on coral reefs as well as rates of calcification, accretion, and bioerosion to assess the ability of coral reefs to 

persist. Across the Pacific Basin there are strong natural Ωarag gradients. Baseline observations of Ωarag ranged from 3.07 at Lisianski Island in the 

Northwestern Hawaiian Islands to 3.93 at Swains Island in American Samoa (Fig 10). American Samoa and the Mariana Archipelago exhibited 

the highest regional mean aragonite saturation states of 3.85 and 3.7, respectively. The Pacific Remote Islands, Northwestern Hawaiian Islands, 

and main Hawaiian Islands all possess average aragonite saturation states within the 3.2–3.6 range.

In the pre-industrial era, similar cross-Pacific gradients in aragonite saturation state were present, but Ωarag levels were likely about 0.5–1 unit 

higher (~3.5–4.5; Ricke et al., 2013). Reduction of a full unit of saturation state can reduce coral calcification by around 15–20% (Chan and 

Connolly, 2013) and reduce net accretion of crustose coralline algae by as much as 70–86% (Kuffner et al., 2008, Jokiel et al., 2008, Johnson et 

al., 2014). Reef ecosystems exposed to Ωarag consistently below 3.0 generally have little or no carbonate reef structure (Manzello et al., 2008).

In relation to aragonite saturation state, carbonate accretion rates were highly variable across the Pacific regions (Fig. 10), ranging from 0.015 g 

CaCO3

 cm-2yr-1 at Kure Atoll in the Northwestern Hawaiian Islands to 0.133 g CaCO3 cm-2yr-1 at Rose Atoll in American Samoa. American Samoa 

and the Pacific Remote Islands exhibited the highest carbonate accretion rates of the U.S. Pacific Islands with regional averages of 0.089 g 

CaCO3

 cm-2yr-1 and 0.062 g CaCO3 cm-2yr-1, respectively. The PRIMNM’s northernmost oligotrophic islands, Johnston and Wake, had two of the 

lowest average carbonate accretion rates, with values of 0.020 g CaCO3

 cm-2yr-1 and 0.017 g CaCO3 cm-2yr-1, respectively. Regional averages for 

the Mariana Archipelago and the Northwestern Hawaiian Islands were 0.039 g CaCO3

 cm-2yr-1 and 0.021 g CaCO3 cm-2yr-1, respectively. Much of 

the habitat provided by coral reefs comes from the structural complexity of their calcium carbonate foundations. Net carbonate accretion rates 

provide an indicator of the reef’s growth overall; hence, the low rates observed, especially around the Northwestern Hawaiian Islands, could be 

cause for concern.
21

Figure 10. Most recent mean aragonite saturation state per island from 2013 to 2015 (main Hawaiian Islands 2013, Mariana Archipelago and Wake Atoll 2014, American Samoa, 

Northwestern Hawaiian Islands, and Pacific Remote Islands 2015) (top). Aragonite saturation state values were calculated from dissolved inorganic carbon and total alkalinity values 

measured from in situ water sampling close to the substrate. Lagoonal sites were removed from the analysis. Error bars indicate standard error (± 1 SE) of the mean. Islands with no error 

bars only had one water sample. Mean carbonate accretion rate per island from 2012 to 2015. Carbonate accretion rates were measured via CAUs (bottom). Error bars indicate standard 

error (± 1 SE) of the mean. No CAU samples were recovered from the main Hawaiian Islands until late 2016 and those samples are still being processed and analyzed. CAUs were not 

deployed at Aguijan, Alamagan, or FDP in the Marianas.

0.00

0.04

0.08

0.12

0.16

Baker

Howland

Jarvis

Kingman

Johnston

Palmyra

Wake

OFU

Rose

Swains

Tau

Tutuila

PACIFIC REMOTE ISLANDS AMERICAN SAMOA

CARBONATE ACCRETION

RATE (g cm-2yr-1)

ARAGONITE SATURATION

STATE (

Ωarag)

3.0

3.3

3.6

3.9

Hawaii

Kauai

Lanai

Maui

Molokai

Niihau

Oahu

MAIN HAWAIIAN ISLANDS MARIANA ARCHIPELAGO

NORTHWESTERN 

HAWAIIAN ISLANDS Maro FFS Kure Lisianski P & H

Aguijan

Alamagan

Asuncion

FDP

Guam

Guguan

Maug

Pagan

Rota

Saipan

Sarigan

Tinian
22

Figure 11. Pacific-wide open ocean climatological distributions of aragonite saturation state (Ωarag) in surface waters (from 

GLODAP v2), benthic in-situ aragonite saturation state (within island circles), and mean carbonate accretion rate per island 

from 2012 to 2015. Size of bubble indicates island-level carbonate accretion rate measured via CAUs. Climatological aragonite 

saturation state source: Jiang et al., 2015; colors show gridded values based on interpolation through Data Interpolating 

Variational Analysis (DIVA) Software.

The distinctions seen in patterns of 

aragonite saturation state and CAU 

accretion rate (Fig. 10) highlight 

the importance of tracking both 

environmental exposures to the 

seawater carbonate chemistry 

and ecological responses to that 

chemistry. For example, you can see 

that while the equatorial islands are 

exposed to low aragonite saturation 

states, largely due to their upwelling 

environment, they still manage 

high rates of net accretion (Fig. 

11). Conversely, coral reefs at Wake 

and Johnston show similar in-situ 

aragonite saturation states, but low 

rates of accretion. There is strong 

forcing of net accretion on CAUs 

by aragonite saturation state (e.g. 

in American Samoa both aragonite 

saturation and accretion rates are 

high), but this distinction is likely 

modified by the relative high and 

low productivity of the equatorial 

islands and northern oligotrophic 

islands, respectively.

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160°0'0"W

160°0'0"W

140°0'0"E

140°0'0"E

170°0'0"W

170°0'0"W

180°0'0"

180°0'0"

150°0'0"E

150°0'0"E

170°0'0"E

170°0'0"E

160°0'0"E

160°0'0"E

30°0'0"N 30°0'0"N

20°0'0"N 20°0'0"N

10°0'0"N 10°0'0"N

0°0'0" 0°0'0"

10°0'0"S 10°0'0"S

20°0'0"S 20°0'0"S

Maug

Asuncion

Pagan

Saipan

Tinian

Rota

Guam

Wake

Johnston

Howland

Baker

Kingman

Palmyra

Swains

Tau OFU Rose

Tutuila

French Frigate

Jarvis

Farallon de Pajaros

Aguijan

Alamagan

Sarigan

Kure Midway

Pearl & Hermes

Lisianski

Laysan

Maro

Agrihan

Niihau

Kauai

OahuMolokai

Hawaii Lanai Maui

Guguan

CARBONATE ACCRETION 

RATE (g cm-2 yr-1)

CLIMATOLOGICAL

Ω arag

Island Midpoint

- High: 4.3

- Low: 2.0

!

!

!

! 0.01 - 0.04

0.04 - 0.07

0.07 - 0.10

0.10 - 0.14

2013 - 2015 Ω arag

!( 3.0 - 3.2

!( 3.2 - 3.5

!( 3.5 - 3.6

!( 3.6 - 3.7

!( 3.7 - 3.9

km

!

0 320 640 1,280 1,920 2,560 o
23

BENTHIC COMMUNITY

Percent cover of different benthic substrates is one of the most widely used metrics of reef condition. Live coral cover is the end product of a 

series of biological and environmental processes; significant changes in percent cover through time are indicative of disturbances. While the 

balance between algal communities and hard corals can be altered by coral mortality events, the ability of reef ecosystems to return to their 

natural balance after a disturbance, often termed resilience, is crucial for recovery and survival of coral reefs. This highlights the importance of 

long-term monitoring for management and conservation of coral reef ecosystems. In general, coral reefs of the PRIMNM have relatively high 

percent live coral cover and relatively low algal cover compared to the other U.S. Pacific regions. However, natural variability in coral cover 

occurs across the Pacific as a result of varying oceanic conditions and substrate. For example, the remote reefs of the Northwestern Hawaiian 

Islands have oceanographic conditions that naturally support predominantly algal-dominated reef communities (Vroom and Braun, 2010).

Across the U.S. Pacific Islands, results from REA surveys conducted from 2013 to 2015, showed island-wide mean estimates of live coral cover 

ranged between 2% at Midway Atoll and 36.4% at Wake Atoll (Fig. 12). Except for Johnston Island (4.9%), the PRIMNM region exhibited relatively 

high island-wide live coral cover with an overall mean greater than 26%. 

0

10

20

30

40

Wake

Swains

Kingman

Maug

Tau

Asuncion

Baker

Pal

myra

Saipan

Aguijan

Tutuila

Howland

Guam

Alamagan

Tinian

Pagan

Maro

Lisianski

Guguan

Hawaii

Maui

Rose

FFS

Jarvis

Molokai

Sarigan

Lanai

Rota

FDP

Oahu

Laysan

Johnston

Kauai

Kure

P & H

Niihau

Mid

way

OFU

CORAL COVER (%)

CORAL COVER

PACIFIC REMOTE ISLANDS AMERICAN SAMOA NORTHWESTERN HAWAIIAN ISLANDS MAIN HAWAIIAN ISLANDS MARIANA ARCHIPELAGO

Figure 12. Mean coral cover (%) on forereef habitats from REA StRS surveys and for the Northwestern Hawaiian Islands from benthic visual estimates at SPC fish sites, conducted during 

the most recent survey years (2013–2015). OFU includes Ofu and Olosega Islands; P & H: Pearl and Hermes Atoll; FFS: French Frigate Shoals; FDP: Farallon de Pajaros. Error bars indicate 

standard error (± 1 SE) of the mean. 
24

FISH COMMUNITY

Gradients of oceanic productivity as well as other factors, such as sea surface temperature (SST), contribute to large natural variability in fish 

biomass, particularly for sharks, other piscivores, and planktivores (Nadon et al., 2012, Williams et al., 2015). As such, the highly productive 

waters of the equatorial upwelling islands tended to have high biomass of large-bodied fishes (sharks and other piscivores), which contributed 

to high total fish biomass. In addition to natural variability, there are clear negative relationships between human population density and largefish biomass (Williams et al., 2011, Williams et al., 2015) (Fig.13).

Figure 13. Pacific-wide 

long-term climatological 

mean of chlorophyll-a 

(mg·m-3) from 2003 to 

2016, and total reef fish 

biomass (g·m-2), from 

stratified random SPC 

surveys (depths of 0–30 

m, n > 25 per island) 

conducted during the 

most recent survey 

years (2009–2015). Size 

distribution is shown by 

pie-chart slices: biomass 

of small-bodied (0–20 

cm in total length; light 

orange), mid-sized 

(20–50 cm in total 

length; medium orange), 

and large-bodied (≥ 50 

cm in total length; dark 

orange) fishes. Size of 

pie-chart shows mean 

total reef fish biomass. 

Kure

Midway

Howland

Tau Rose

Baker

Palmyra

Kingman

Jarvis

Swains

OFU

Tutuila

Wake

Johnston

Farallon de Pajaros

Maug

Asuncion

Agrihan

Pagan

Alamagan

Guguan

Sarigan

Saipan

Tinian

Aguijan

Rota Guam

Pearl & Hermes

Lisianski

Laysan

Maro

French Frigate

Hawaii

Maui

Lanai

Molokai Oahu Kauai Niihau

150°0'0"W

150°0'0"W

160°0'0"W

160°0'0"W

170°0'0"W

170°0'0"W

180°0'0"

180°0'0"

170°0'0"E

170°0'0"E

160°0'0"E

160°0'0"E

150°0'0"E

150°0'0"E

140°0'0"E

140°0'0"E

30°0'0"N 30°0'0"N

20°0'0"N 20°0'0"N

10°0'0"N 10°0'0"N

0°0'0" 0°0'0"

10°0'0"S 10°0'0"S

0 350 700 1,400 2,100 2,800

km o

450 g·m-2

0 - 20

20 - 50

≥ 50

- Low : 0.02

- High : 0.30

TOTAL FISH 

BIOMASS (g·m-2)

CHL-a (mg m-3 SIZE CLASS (cm) )

Island Midpoint
25

Total reef fish biomass varied from 11.1 g·m-2 at Oahu to 246.8 g·m-2 at Kingman 

Reef (Fig. 14). In general, total fish biomass was lower at inhabited, heavily 

impacted islands, such as the main Hawaiian Islands and the southern Mariana 

Islands, and higher at remote, uninhabited islands. The PRIMNM and the 

Northwestern Hawaiian Islands exhibited the highest total reef fish biomass in 

the U.S. Pacific regions with mean total fish biomass of 125.0 g·m-2 and 120.9 

g·m-2, respectively. By contrast, average reef fish biomass was 45.6 g·m-2 in the 

Marianas, 45.0 g·m-2 in American Samoa, and 28.2 g·m-2 in the main Hawaiian 

Islands. 

Figure 14. Pacific-wide comparisons of total reef-fish biomass (g·m-2) from stratified random SPC surveys (depths of 0–30 m) conducted during the most recent survey years (2009–2015). 

P & H is Pearl and Hermes Atoll; FDP is Farallon de Pajaros; FFS is French Frigate Shoals; and OFU includes Ofu and Olosega Islands; AGS is Alamagan, Guguan, and Sarigan. Error bars 

indicate standard error (± 1 SE) of the mean. 

0

100

200

Kingman

P & H

Jarvis

Lisianski

Mid

way

Pal

myra

Kure

Maro

Baker

Howland

FFS

AGS

Asuncion

Agrihan

FDP

Laysan

Pagan

Johnston

Niihau

Wake

Maug

Swains

Rose

Tau

Tutuila

Hawaii

Molokai

Maui

Lanai

Aguijan

Kauai

Rota

Guam

Saipan

Tinian

Oahu

FISH BIOMASS

PACIFIC REMOTE ISLANDS AMERICAN SAMOA NORTHWESTERN HAWAIIAN ISLANDS MAIN HAWAIIAN ISLANDS MARIANA ARCHIPELAGO

FISH BIOMASS (g m-2)

OFU

Whitespot hawkfish (Paracirrhites hemistictus) at Jarvis Island, 

Photo: NOAA Fisheries/Andrew E. Gray. 
26

These differences in total 

fish biomass can be largely 

attributed to the substantial 

differences in the fish size 

distribution among islands 

(Fig. 15). The distribution of 

small-bodied fishes (0–20 cm in 

length) was relatively uniform 

across U.S. Pacific regions, 

with the exception of the 

equatorial upwelling islands 

within the PRIMNM, where 

biomass of small-bodied fishes 

was very high due to enhanced 

productivity. Biomass of midsized fishes (20–50 cm in total 

length) differed across the 

regions and was substantially 

lower in the highly populated 

regions of the main Hawaiian 

Islands and the southern 

Mariana Islands compared to 

less populated areas across the 

Pacific. The greatest differences 

of reef fish biomass across the 

regions can be attributed to 

the relative lack of large-bodied 

fishes (≥ 50 cm in total length) 

at inhabited islands. 

Figure 15. Pacific-wide comparisons of reef-fish biomass (g·m-2) per size class from stratified random SPC surveys (depths of 0–30 m; n > 

25 per island) conducted during the most recent survey years (2009–2015). Note the differences in scale on the y-axes. Biomass of smallbodied (0–20 cm in total length; top row), mid-sized (20–50 cm in total length; middle row), and large-bodied (≥ 50 cm in total length; 

bottom row) fishes. P & H is Pearl and Hermes Atoll; FDP is Farallon de Pajaros; FFS is French Frigate Shoals; and OFU includes Ofu and 

Olosega Islands. Error bars indicate standard error (± 1 SE) of the mean. 

0

10

20

30

40

0

20

40

60

80

0

50

100

150

200

Small−Bodied Fishes (0–20 cm)

Mid−Sized Fishes (20–50 cm)

Large−Bodied Fishes (50+ cm)

Baker

Howland

Jarvis

Kingman

Johnston

Palmyra

Wake

Rose

Swains

Tau

Tutuila

Hawaii

Kauai

Lanai

Maui

Molokai

Niihau

Oahu

Agrihan

Aguijan

Asuncion

FDP

Guam

Maug

Pagan

Rota

Saipan

Tinian

AGS

FFS

Kure

Laysan

Lisianski

Maro

Midway

P & H

FISH BIOMASS (g m-2)

PACIFIC REMOTE ISLANDS AMERICAN SAMOA MAIN HAWAIIAN ISLANDS MARIANA ARCHIPELAGO

NORTHWESTERN 

HAWAIIAN ISLANDS

OFU
27

MICROBIAL COMMUNITY

Nutrient-rich organic material released by coral reefs constitutes an important foundation for the marine trophic food web and the associated 

biodiversity of coral reef ecosystems. In any coral reef, this organic material forms the base of a microbial and “macrobial” food web of higher 

consumers. When a reef ecosystem shifts from being dominated by corals to being dominated by macroalgae, the microbial community and 

recycling mechanisms are disrupted. For example, the organic material released by these non-calcifying organisms (fleshy macroalgae and 

turf algae) is taken up by fast growing, opportunistic microbial communities; and, hence, shift these energetic materials away from supporting 

higher consumers, like fish (Fig. 16). This phenomenon is referred to as microbialization (McDole et al., 2012).

One way to look at larger patterns of microbialization is to compare metabolic rates between microbes and fish. Given the mass of an organism, 

regardless of whether a fish or a bacterium, we can calculate how much energy it needs to survive, i.e., the metabolic needs of that organism. 

By counting and noting the sizes of fish and microbes, we can calculate the total metabolic needs of each group at a particular reef. We have 

a strong argument that microbialization is occurring when the microbes’ metabolic needs constitute an increasing proportion of the total 

metabolic needs of the reef ecosystem (i.e., both fish and microbes; Fig. 17). 

Figure 16. Conceptual depiction of 

microbialization positive feedback loop. 

Figure adapted from original diagram by 

Andreas Haas.

MICROBIALIZATION

increased 

macroalgae

increased organic 

materials

higher microbial 

biomass

less coral 

cover

less fish

lower water 

quality
28

Figure 17. Proportion of Total Reef Metabolic Rate composed of 

Microbial Metabolic Rate (i.e. “Microbialization Score”) against 

the cumulative human impact scores (NCEAS) on U.S. Pacific 

coral reefs. Black line is the linear regression line showing the 

positive relationship between cumulative human impact 

score and the microbialization score (y = 8.19x-26.1, R2

 = 0.68, 

95% CI = 5.994 to 10.39). Regions are indicated by color and 

islands are indicated by the first three letters of their name. 

Higher microbialization scores may indicate a vulnerability of 

that ecosystem to phase shifts between coral and macroalgal 

dominated states. 

It is also evident that as human impacts on reef ecosystems increases, so does the share of a reef’s energy needs going through microbes. In low 

impacted reef areas, microbial energy needs are about 20% of the total energy used on a reef (e.g., Baker, Jarvis, Palmyra, Kingman), and this 

increases to about 90% of total energy in highly impacted reefs (Maui, Kauai, Oahu; Fig. 17). A strong significant positive correlation between the 

microbial share of reef metabolism (i.e., microbialization) and the cumulative human impact scores on reefs from National Center of Ecological 

Analysis and Synthesis (NCEAS) can be seen on islands from the four archipelagic regions of Pacific RAMP as a result of reef degradation and 

lower fish biomass (McDole et al., 2012). 

The shift towards increased microbial biomass and metabolism at the potential expense of higher trophic levels might create a sustained 

positive feedback loop (Fig. 16). Consequently, once a regime shift to an algal-dominated state has occurred, the process of microbialization 

has the potential to make returning to a coral-dominated state more difficult. 

NIH OAH KAU

GUA MAI SAI

JOH LAN MOL

HAW

TUT TIN

100

80

60

40

20

0

AGU

TAU

SWN

AGR ROT

HOW

MAU

FDP

BAK

ROS

ASC

PAL

KIN

JAR

GUG WAK

0 5 10 15 20

MICROBIALIZATION SCORE (%)

HUMAN IMPACT SCORE (FROM NCEAS)

OFU

PACIFIC REMOTE ISLANDS

AMERICAN SAMOA

MAIN HAWAIIAN ISLANDS

MARIANA ARCHIPELAGO

AGR AGRIHAN 

AGU AGUIJAN

ASC ASUNCION 

BAK BAKER 

FDP FARALLON DE PAJAROS

GUA GUAM 

GUG GUGUAN 

HAW HAWAII 

HOW HOWLAND 

JAR JARVIS 

JOH JOHNSTON ATOLL 

KAU KAUAI 

KIN KINGMAN REEF 

LAN LANAI 

MAI MAUI 

MAU MAUG 

MOL MOLOKAI 

NIH NIIHAU 

OAH OAHU 

OFU OFU & OLOSEGA 

PAL PALMYRA ATOLL 

ROS ROSE ATOLL 

ROT ROTA 

SAI SAIPAN 

SWN SWAINS 

TAU TAU 

TIN TINIAN 

TUT TUTUILA 

WAK WAKE ATOLL 
29

PACIFIC REMOTE ISLANDS

IN A MONUMENT CONTEXT
30

BENTHIC COMMUNITY

Spatial Comparisons of Benthic Cover

Percent cover of benthic functional groups, including coral, 

crustose coralline algae (CCA), macroalgae, and turf algae, is 

a widely utilized indicator of coral reef condition. CREP uses 

both towed-diver and REA surveys to measure percent cover; 

however, these methods sometimes produce different 

results, which should be acknowledged when evaluating 

percent cover estimates. Visual estimates during broadscale towed-diver surveys sometimes overestimate coral 

and CCA cover in a given segment (~2,000 m2

). Additionally, 

the towed-diver surveys do not differentiate between 

macroalgal cover and turf algal cover. Because turf and 

macroalgae have different ecological roles in the coral reef 

ecosystem, REA surveys should be used when evaluating 

these two functional groups. Generally, high live coral cover 

and high CCA cover, as commonly observed for reefs in the 

PRIMNM, are indicative of healthy coral reefs. Based on 

percent cover observed throughout the U.S. Pacific, reefs 

exhibiting coral cover above 20% are considered to be in 

fair condition, reefs exhibiting coral cover above 30% are 

considered very good, and reefs exceeding 40% coral cover 

are considered excellent. For CCA cover, reefs exceeding 

10% cover are considered to be in good condition and 

reefs exceeding 20% cover are considered excellent. These 

reference points were used to score the islands in the reef 

condition index summarized later in the document. Above: Crustose coralline algae at Kingman Reef in 2012, Photos: NOAA Fisheries; 

Previous page: Periclimenes shrimp under a Stichodactyla sea anemone at Palymra Atoll, 

Photo: NOAA Fisheries/Megan Moews-Asher.
31

From 2014–2015 REA surveys, live coral cover in the PRIMNM ranged from 4.9% at Johnston Atoll to 36.4% at Wake Atoll, both in the northernmost 

oligotrophic island group. The central transition islands exhibited live coral cover at 34.0% and 28.5% at Kingman and Palmyra, respectively. 

The equatorial islands exhibited live coral cover at 28.9%, 23.4%, and 17.8 % at Baker, Howland, and Jarvis respectively. No obvious patterns 

between islands groups were observed (Fig. 12). 

For CCA cover, estimates in the northernmost islands of the PRIMNM were 9.5% at Wake and 13.82% at Johnston. The central transition islands 

exhibited CCA cover at 9.8% and 18.9% for Kingman and Palmyra, respectively. CCA cover at the equatorial islands was highest at Howland with 

CCA cover estimated at 26.9%. CCA cover was an estimated 25.6% at Jarvis and 24.2% at Baker. 

Generally, reefs with lower percent macroalgal cover are considered healthier. Throughout the U.S. Pacific, reefs exhibiting macroalgal cover 

less than 10% are considered to be in good health, reefs exhibiting macroalgae cover between 10% and 20% are considered to be in fair health. 

Johnston exhibited the lowest macroalgal cover at 6.4%, while Wake exhibited macroalgal cover at 16.5%. The central transition islands exhibited 

macroalgal cover at 7.2% and 12.8% for Kingman and Palmyra, respectively. For all the PRIMNM, Jarvis exhibited the highest macroalgal cover 

with estimates at 25.4%, likely a result of the high productivity. The other equatorial islands, Howland and Baker, exhibited macroalgal cover 

at 14.9% and 15.6%, respectively. 

Turf algal cover at the PRIMNM was highest at Johnston, which exhibited exceptionally high turf algal cover of 64.0%. With the exception 

of Johnston, turf algal cover for all of the PRIMNM remained below 29%. Wake exhibited turf algal percent cover at 28.6%. Kingman and 

Palmyra exhibited turf algal cover at 29.0% and 24.3%, respectively. Turf algal cover at Jarvis, Howland, and Baker was 25.5%, 24.8%, and 22.3%, 

respectively. Turf algal cover was not included in the reef condition index.

Temporal Comparisons of Benthic Cover

Although there were changes in benthic cover over time, some significant, there were no obvious steadily increasing or decreasing trends from 

2006 to 2015 at any of the Pacific Remote Islands. Percent cover has remained relatively stable for all of the functional groups at each of the 

islands, with the exception of Johnston. Beginning in 2010, there was a significant increase in turf algae and corresponding decrease in CCA 

cover at Johnston (Fig. 18). In 2010, percent cover of turf algae at Johnston was only 12.5% in 2010, but increased to 64.0% by 2015. Conversely, 

percent cover of CCA at Johnston was estimated at 57.7% in 2010, but decreased to 13.8% in 2015. The most significant temporal change 

observed in the PRIMNM occurred during the 2015–2016 El Niño warming event and will be discussed in the island highlights section on Jarvis 

Island. 
32

Figure 18. Temporal trends in percent cover for four primary benthic functional groups, including coral, CCA, macroalgae, and turf algae in the forereef habitats from REA surveys 

conducted in 2005–2015, shown by island group. In 2014, survey design changed from REA sites to stratified random sampling design (StRS), survey design change indicated by dashed 

vertical line. Error bars indicate standard error (± 1 SE) of the mean.

0

20

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200520062007200820092010201120122013201420152005200620072008200920102011201220132014201520052006200720082009201020112012201320142015

EQUATORIAL ISLANDS NORTHERNMOST ISLANDS

Baker Howland Jarvis Kingman Palmyra Johnston Wake

CENTRAL TRANSITION ISLANDS

TURF 

COVER (%)

MACROALGAE 

COVER (%)

CCA

 COVER (%)

CORAL 

COVER (%)
33

Figure 19. Mean generic richness of adult hard corals for each island estimated from 

2014–2015 REA StRS surveys. Generic richness is the total count of unique genera in a 

sampling area. Error bars indicate standard error (± 1 SE) of the mean.

Coral Diversity

Coral reefs represent the most biologically diverse marine ecosystems 

in the world, and numerous studies have shown that diverse systems 

are more resilient to disturbances through time (Folke et al., 2004; 

Hughes et al., 2005; Worm et al., 2006). Generic richness is the total 

number of unique genera recorded around each island and, among 

other measures, is often used as an indicator of coral diversity. Since 

larger reef ecosystems often support a wider range of habitat types, 

oceanographic conditions, and taxa, we computed an average generic 

richness per habitat stratum weighted by stratum area for each island 

based on our 2014–2015 StRS REA surveys. Kingman and Palmyra had 

the highest weighted coral generic richness values with mean values 

of 22.7 and 23.7 species, respectively. Johnston had the lowest generic 

coral richness with 5.8 species (Fig. 19). 

Disease

Disease occurrence was calculated as the number of diseased colonies 

divided by the total number of colonies for adult hard scleractinian 

corals. Disease occurrence estimates are for all diseases except for 

lesions resulting from barnacle infestation and tubeworm infestation. 

Disease occurrence on hard corals across the PRIMNM during 2009–2015 

sampling years ranged from 0.1% at Baker in 2010 to 3.3% on Palmyra in 

2010. Diseases present included, among others: white syndrome, subacute tissue loss, skeletal growth anomalies, pigmentation responses, 

as well as fungal, algal, and cyanobacterial infections. In 2005 and 2006 

surveys, Johnston exhibited significantly greater mean overall disease 

occurrence than other islands in the Pacific (Vargas-Ángel, 2009). This 

trend is further evaluated in the island highlights section.

0

5

10

15

20

25

Baker Howland Jarvis Kingman Palmyra Johnston Wake

GENERIC RICHNESS

Coral diversity observed during benthic survey transect at Kingman Reef, 

Photo: NOAA Fisheries/Bernardo Vargas-Ángel.
34

Figure 20. Mean bleaching occurrence—for adult hard corals at all depths and reef zones from 2014 to 2015, estimated from StRS method. The occurrence was calculated as the sum 

of all infected colonies divided by the total number of colonies. In the permanent site studies (2009–2013), occurrence is the sum of all infected colonies divided by the sum of the total 

colonies at each island. For StRS surveys (2014–2015), the occurrence is the mean occurrence by island calculated for each StRS sampling site. 

0

10

20

30

40

2009201020112012201320142015

20092010201120122013201420152009201020112012201320142015

EQUATORIAL ISLANDS NORTHERNMOST ISLANDS

BLEACHING OCCURENCE (%)

Baker Howland Jarvis Kingman Palmyra Johnston Wake

CENTRAL TRANSITION ISLANDS

Coral Bleaching

REA StRS surveys measure bleaching and disease occurrence on hard scleractinian corals. Bleaching occurrence is presented as prevalence, 

calculated as the number of colonies exhibiting signs of bleaching (irrespective of severity or extent) divided by the total number of colonies for 

adult hard scleractinian corals. From 2009 to 2015, bleaching occurrence in the PRIMNM was generally low, below 5% at most islands. (Fig. 20). 

Spikes in bleaching occurrence occurred at Baker and Howland in 2010 due to a moderate El Niño warm event with mean occurrence reaching 

38.1% and 35.1%, respectively (Vargas-Ángel et al., 2011). Noteworthy is the absence of these high bleaching occurrences in neighboring Jarvis 

Island. The coral bleaching events at Baker and Howland, as well as the massive 2015-2016 coral bleaching event at Jarvis, are evaluated further 

in the island highlights section. 
35

FISH COMMUNITY

Total Reef-Fish Biomass and Composition

Across the study period, the highest average total reef-fish biomass was observed at Jarvis Island (179.9 g·m-2) (Fig. 14 and 21) and Kingman Reef 

(246.8 g·m-2), both located in equatorial, nutrient-rich waters (Fig. 13). By contrast, in the northern oligotrophic waters, average fish biomass was 

lowest at Wake (52.6 g·m-2), followed by Johnston (54.9 g·m-2). 

Reef fishes play an important role in the function of coral reef ecosystems through the transfer of energy from primary producers at the food 

web base to top predators and nutrient recycling in microbial and detrital food pathways. It can be useful to consider fishes functionally, as 

defined by consumer groups, especially as some functional groups can promote ecosystem resilience. The four key functional groups are 

primary consumers, secondary consumers, planktivores, and piscivores. Primary consumers are fishes that eat algae and detritus (fine organic 

matters within algal turfs) and are believed to be important contributors to resilience of coral reef ecosystems (Green and Bellwood, 2009). 

Secondary consumers include omnivores, fishes that consume both algae and other organisms, and benthic invertivores, those that feed on 

benthic organisms such as crustaceans and other invertebrates. Planktivorous fishes consume both zooplankton and phytoplankton and are 

generally found feeding in the water column. Lastly, piscivores are fishes that consume other fish. Functional classification of Pacific reef fishes 

is based largely on diet information taken from FishBase (Froese and Pauly, 2017). 

Across the PRIMNM, like total reef-fish biomass, biomass of the four functional groups also varied considerably (Fig. 21). For example, biomass of 

primary consumers was markedly low at Kingman (19.7 g·m-2) relative to total biomass and accounted for less than 8% of total reef-fish biomass, 

on average, from 2010 to 2015. Estimates of total reef-fish biomass at Kingman were instead driven primarily by extremely high biomass of 

piscivorous fishes (top predators) (157.6 g·m-2), making up over 63% of total reef-fish biomass. By contrast, at Johnston and Wake, primary 

consumers accounted for a much higher proportion of the total fish community. Primary consumers made up 38% and 43% of total reef-fish 

biomass at Johnston and Wake, respectively, whereas piscivores were much less abundant at these islands. 

Both mean piscivore biomass (8.8 g·m-2) and mean planktivore biomass (4.6 g·m-2) were lowest at Wake. Similarly, biomass of both piscivores 

(16.4 g·m-2) and planktivores (8.3 g·m-2) was also relatively low at Johnston. At both islands, these two functional groups contributed least to 

overall fish biomass. Both planktivore and piscivore biomass were significantly higher at the equatorial upwelling islands (Kingman, Palmyra, 

Jarvis) due to the nutrient-rich water and high productivity. 
36

Figure 21. Trends in mean total reef-fish biomass (g·m-2) from fore-reef SPC surveys from 2010 to 2016, ordered by island, from left to right. Stacked bars show biomass per trophic group 

based on fish diet. Primary consumers include fishes that eat algae and detritus; secondary consumers include fishes with a wide variety in diet (omnivores) and fishes that eat invertebrates (following Williams et al., 2011). Error bars indicate standard error (± 1 SE) of the mean.

The nutrient-rich water promotes high biomass of large predatory fishes, as well as high biomass of planktivores that feed on the abundant 

plankton surrounding the islands. The northern oligotrophic islands of Johnston and Wake are located in areas with naturally lower productivity 

and lower phytoplankton density compared to the other islands in the PRIMNM. Thus, due to the natural variability in oceanographic drivers, it 

is not unexpected for these islands to have lower biomass for these groups. 

0

100

200

300

400

20102012201420162010201220142016

2010201220142016

2010201220142016

2010201220142016

2010201220142016

2010201220142016

BAKER HOWLAND JARVIS KINGMAN PALMYRA JOHNSTON WAKE

FISH BIOMASS (g m-2)

Planktivores

Primary Consumers

Secondary Consumers

Piscivores 
37

Large Fish Biomass

Compared to SPC surveys, towed-diver surveys provide better estimates of 

large-fish (≥ 50 cm in total length) biomass because the surveys allow divers to 

cover much larger areas during each survey (~22,000 m

2

 per survey compared to 

353 m

2

); thereby increasing the frequency of encounters with large, rare fishes. 

Towed-diver surveys across the study period show that there were substantial 

differences in the biomass of large-bodied fishes across islands in the PRIMNM 

corresponding to the gradient in productivity (Fig. 22). Biomass of large fishes 

was highest at Jarvis, averaging 74.2 g · m-2 across the 2001–2015 study period. 

At Johnston, large-fish biomass, was considerably lower, averaging 5.8 g·m-2 

across the 2004–2015 study period.

Likely, the primary reason for the stark differences in large fish biomass across 

the PRIMNM is the range of oceanic productivity, as mentioned herein. Jarvis is 

highly productive, and therefore supports a high abundance of both planktivores 

and piscivores as described above (Williams et al., 2015). For example, these 

conditions support high biomass of both sharks and rays. Similarly, Baker and 

Howland Islands also occur in productive waters, which is reflected in the 

high biomass of these same groups across the study period at these islands. 

By contrast, Johnston and Wake occur in the oligotrophic region of lowest 

oceanic productivity and they have substantially lower total large-fish biomass 

than the productive equatorial islands. Similar to Johnston, average large-fish 

biomass at Wake across the study period (2005–2014) was low, 19.5 g·m-2, which 

was only 26% of the large-fish biomass observed at Jarvis. Notably, large-fish 

biomass appeared to decline at both Johnston and Wake over the study period. 

Interestingly, abundance of large parrotfish was highest at Wake, where there 

have been relatively high numbers of bumphead parrotfish (Bolbometopon 

muricatum).

Reef sharks at Kingman Reef, Photo: NOAA Fisheries.
38

Figure 22. Trends in 

mean biomass (g·m-2) 

of large-bodied fishes 

(≥ 50 cm total length) 

from towed-diver 

surveys across the 

2001–2015 study 

period at Baker, 

Howland, Jarvis, 

Kingman, Palmyra, 

Johnston, and Wake. 

Total large fish biomass 

is shown for each 

island in top row. The 

following rows show 

biomass of key families: 

jacks (Carangidae), 

parrotfishes 

(Scaridae), rays 

(Myliobatidae), sharks 

(Carcharhinidae), 

snappers (Lutjanidae), 

and surgeonfishes 

(Acanthuridae). 

Sampling at all islands 

began in 2001, with the 

exception of Johnston 

and Wake, beginning 

in 2004 and 2005, 

respectively. Total large 

fish biomass is scaled 

to maximum large 

fish biomass found at 

each island with each 

subsequent family 

scale to maximum 

biomass found across 

the PRIMNM (note the 

differences in scale on 

the y-axes). Error bars 

indicate standard error 

(± 1 SE) of the mean. 

0

50

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150

2000

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30

4005

10

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50

1000

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8005

100369

2001200520102015200120052010201520012005201020152001200520102015200120052010201520012005201020152001200520102015

BAKER HOWLAND JARVIS KINGMAN PALMYRA JOHNSTON WAKE

FISH BIOMASS (g m-2)

TOTAL JACKS PARROTFISHES RAYS SHARKS SNAPPERS SURGEONFISHES
39

INTEGRATING ECOSYSTEM COMPONENTS

With the transition toward ecosystem-based management, it is useful to develop indicators that integrate across ecosystem components to 

describe the overall condition or status of coral reefs. Following an approach developed for a suite of NCRMP Coral Reef Condition Report Cards, 

CREP has created a Benthic Condition Index, a Reef Fish Condition Index, and a Climate Condition Index that use various Pacific RAMP data sets 

collected in recent years. An overall Coral Reef Condition Index is composed of equally-weighted Benthic Condition, Fish Condition, and Climate 

Condition Indices. 

The components of the Benthic Condition Index are benthic cover, including coral, crustose coralline algae, and macroalgae; coral generic 

richness; adult coral colony densities; juvenile coral colony densities; and partial mortality rates of coral. Colony densities and partial mortality 

were based on selected coral genera that are ecologically important and abundant at each island. Scores increased with increasing values for 

all indicators other than macroalgae cover and partial mortality, for which scores decreased with increasing values. The components of the Reef 

Fish Condition Index are reef fish biomass, mean size of target families, and a combined predator index comprised of shark abundance and 

total piscivore biomass. The components of the Climate Condition Index are temperature stress, reef material growth, and ocean acidification. 

Scoring for the components was based on a variety of approaches, all with the goal of generating values on a 0–100 scale, where 90+ represents 

excellent conditions and less than 60 represents very poor conditions.

The Coral Reef Condition Index provides an interdisciplinary synthesis of the status of the coral reef ecosystems for each of the islands/atolls 

in the PRIMNM that is comparable with the other U.S. islands and atolls across the Pacific. The Coral Reef Condition Index values calculated for 

each island in the PRIMNM are displayed as excellent (dark green), good (light green), fair (yellow), poor (orange), or very poor (red) in Figure 

23. The overall Coral Reef Condition Index is fair for Johnston (78) and Baker (78) and good for Jarvis (80), Howland (81), Wake (83), Palmyra 

(84), and Kingman (86). The Reef Fish Condition Index scores were typically the highest of the three indices. All islands scored between good 

and excellent. In common with other uninhabited (or very lightly populated in the case of Wake) locations, reef-fish communities at each of 

the PRIMNM islands are relatively intact, with scores ranging from 84 at Baker to 100 at Jarvis. The Benthic Condition Index for all islands in 

the PRIMNM were fair to good, with scores ranging from 76 at Jarvis to 89 at Kingman. The fair Benthic Condition Index values at Jarvis and 

Johnston were primarily due to benthic composition and generic richness components of the index. At Jarvis, the low coral cover score (68), 

the low macroalgae score (65), and the lower generic richness score (70) led to fair benthic condition scores (76). At Johnston, a low coral cover 

score (43) and low generic richness score (62) decreased Johnston’s overall score (79). The Climate Condition Index scores were the lowest of 

the three indices, ranging from poor scores at Jarvis (65) and Johnston (66) to fair scores at Howland (70), Baker (70), Palmyra (71), Kingman (72), 

and Wake (73).
40

Figure 23. Coral Reef Condition Index across the PRIMNM. Reef Fish Condition, Climate Condition, and Benthic Condition Indices are 

represented within the pie chart components, with the circle in the middle representing the Coral Reef Condition Index (an equally 

weighted average of all 3 indices). Index condition ranges from excellent (dark green), good (light green), fair (yellow), poor (orange), 

to very poor (red). 

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

91

73

85

83

93

70

80

81

84

70

80

78

88

66

79

78

97

71

85

84

98

72

89

86

100

65

76

80

WAKE

JOHNSTON

KINGMAN

PALMYRA

JARVIS

BAKER

HOWLAND

INDEX CONDITION

INDEX COMPONENT

TOTAL BENTHIC

FISH

CLIMATE

km

0 500 1,000 o

EXCELLENT

GOOD

FAIR

POOR 

VERY POOR

The Climate Condition Index scores 

were relatively low due to the 

extended period of anomalously 

warm water temperatures 

associated with the 2015–2016 El 

Niño and 2014–2016 global coral 

bleaching event. In addition, ocean 

acidification scores were based on 

comparison with pre-industrial 

levels that were more optimal 

for growth of coral reefs and are, 

therefore, relatively low at most 

or all coral reef locations in the 

PRIMNM. Despite these relatively 

low scores for the Climate Condition 

Index, the overall Coral Reef 

Condition Indices for all the islands 

remained fair to good through 

the end of 2015 (the last year of 

consistent data). Unfortunately, 

mass coral bleaching in 2015–2016 

at the equatorial upwelling islands 

of Jarvis (high mortality), Howland, 

and Baker (low mortality), as 

discussed in the island highlights 

section, will likely decrease the 

Coral Reef Condition Index scores 

following the next round of Pacific 

RAMP surveys. 
41

ISLAND HIGHLIGHTS
42

BAKER, HOWLAND, AND JARVIS ISLANDS: 

CORAL BLEACHING

Coral bleaching is characterized by the observed whitening 

of corals that results from the loss of their symbiotic 

algae, called zooxanthellae, whose pigments provide 

the colors normally associated with healthy corals. A 

variety of stressors can induce coral bleaching, including 

anomalously warm (or cold) water temperatures, increases 

in solar radiation, reduced salinity, sedimentation and 

other land-based pollution, or bacteria and other infections 

(Brown, 1997). Bleaching events often coincide with El Niño 

episodes characterized by anomalously warm sea surface 

temperatures. Though bleaching does not mean the coral 

is dead, it can eventually lead to coral mortality, which can 

have devastating impacts on coral reef ecosystems. 

Above left: One of the few remaining table Acropora corals at Jarvis Island in the foreground 

with red turf algae growing over damaged corals in 2017, Photo: NOAA Fisheries/Tate Wester;

Above: Bleached Pavona corals at Jarvis Island in 2016, Photo: NOAA Fisheries/Bernardo 

Vargas-Ángel; Previous page: Manta ray at Howland Island, Photo: NOAA Fisheries. 
43

The mortality rate is often closely related to the 

intensity of the bleaching event (Hoegh-Guldberg, 

1999), which can be expressed as Degree Heating 

Weeks (DHW). DHWs indicate how much thermal 

stress has accumulated in an area within a given 

period by expressing the duration and magnitude 

by which temperatures have exceeded a reference 

coral bleaching threshold, defined as 1°C above the 

highest summertime mean sea surface temperature 

(Liu et al., 2006). Climate models project that 

bleaching events are expected to increase in 

frequency and intensity in the future. Bleachingassociated coral mortality rates are also expected 

to increase over the next couple of decades. Baker, 

Howland, and Jarvis have all been impacted by 

these ocean warming events, causing disruption 

to the benthic community structure. Between 

2009 and 2010, Baker and Howland experienced 

20.65 DHW and Jarvis experienced 20.05 DHW 

(NOAA Coral Reef Watch 50-km Virtual Stations, 

2000). Between 2015 and 2016, Baker and Howland 

experienced 22.7 DHW and Jarvis experienced 35.8 

DHW (Fig. 24). In comparison, the Central Transition 

Islands experienced approximately 9 DHW between 

2009–2010 and 2015–2016, and the Northernmost 

Islands experienced 0 DHW between 2009 and 

2010. During 2015–2016, the Northernmost Islands, 

Wake and Johnston, experienced 2 DHW and 9 

DHW, respectively. 

Figure 24. Degree Heating Weeks (DHW; °C weeks) across the PRIMNM from 2000–2016. 

Data Source: NOAA Coral Reef Watch 50-km Virtual Stations. 

0

10

20

30

0

10

20

30

0

10

20

30

2000 2002 2004 2006 2008 2010 2012 2014 2016

DEGREE HEATING WEEKS (°C WEEKS)

EQUATORIAL ISLANDS

CENTRAL TRANSITION ISLANDS

NORTHERNMOST ISLANDS

Howland and Baker

Jarvis

Kingman

Palmyra

Johnston

Wake
44

BAKER AND HOWLAND ISLANDS: 

2010 BLEACHING EVENT

Baker and Howland Islands have high inter-annual 

variability in temperature due to their location on the 

equator and the El Niño-Southern Oscillation. During 

the 2009–2010 El Niño event, sea surface temperature 

exceeded the coral bleaching threshold of 29.7oC (1 

degree C above the climatological maximum monthly 

mean; method source: Liu et al., 2006) continuously 

from October 22, 2009, to January 7, 2010 (Fig. 25). Sea 

surface temperature continued to fluctuate around the 

bleaching threshold from mid-January through midMarch, until the temperature progressively decreased 

after March 15, 2010. 

A Pacific RAMP cruise surveyed the coral reefs around 

Baker and Howland in February 2010, shortly after the 

El Niño event. The surveys observed bleaching at both 

islands, with mean bleaching occurrence estimated at 

38% for Baker and 35% for Howland. Despite similar 

degree heating week measurements in 2010, bleaching 

was not observed during surveys at Jarvis Island in April 

2010. By 2012, the following survey year, bleaching 

occurrence had decreased to 11% for Baker and 4% for 

Howland (Fig. 20), indicating potential recovery since 

live coral cover did not decrease from 2009 to 2012. This 

is evident when comparing the long-term averages of 

coral cover from 2005 to 2015 (Fig. 18).

Figure 25. Sea Surface Temperature (SST; °C) at Howland and Baker Islands from 11/28/2000 to 

10/13/2016. Data Source: NOAA Coral Reef Watch 50-km Virtual Stations, 2000. 

25

26

27

28

29

30

31

2002 2004 2006 2008 2010 2012 2014 2016

TEMPERATURE (°C )

BLEACHING THRESHOLD

MAX MONTHLY MEAN TEMP

2000

Bleached corals at Howland Island in 2010, Photo: NOAA Fisheries/Bernardo Vargas-Ángel. 

BAKER AND HOWLAND
45

Reduction of local and global stressors is essential for 

sustaining benthic community health and promoting coral 

resilience after a bleaching (or other disturbance) event. 

Stressors can be reduced by decreasing land-based pollution 

and increasing connectivity and gene flow to bolster coral 

recovery from periodic bleaching events (Hughes et al., 

2003, Hughes et al., 2010). Additionally, increasing grazer 

and detritivore biomass decreases macroalgal and turf 

algal cover and increases encrusting algae, including reefbuilding crustose coralline algae. Furthermore, biomass of 

large parrotfish appears to be positively associated with 

increased live coral cover. The scraping and excavating 

of parrotfish open new sites on the reef that facilitate the 

settlement, survival, and growth of CCA and coral (Heenan 

and Williams, 2013). A healthy herbivorous fish community 

may have contributed to Baker and Howland’s observed 

recovery from the 2010 bleaching event and prevented a 

possible phase shift to an algal-dominated reef (Fig. 18).

Table Acropora at Baker Island in 2017 (Photo: NOAA Fisheries/Tate Wester); 

Redlip parrotfish (Scarus rubroviolaceus) and crustose coralline algae at Baker Island in 2017, 

Photo: NOAA Fisheries/Kevin Lino.
46

JARVIS ISLAND: 2015-2016 BLEACHING EVENT

Jarvis Island was severely impacted by the strong 2015–2016 El Niño, during which abnormally high sea surface temperatures continuously 

exceeded the coral bleaching threshold of 28.7 oC from April 16, 2015 to February 29, 2016. SST continued to fluctuate around the bleaching 

threshold from early March through mid-May of 2016, until the temperature progressively returned to normal conditions after May 19, 2016 

(Fig. 26). Conditions at Jarvis surpassed the coral bleaching threshold for 43 consecutive weeks, 3.7 times longer than conditions at Baker and 

Howland in 2009–2010. Based on REA StRS image analysis, the hard coral cover at Jarvis declined from 17.8% in 2015 (pre-bleaching event), to 

0.31% in 2016 (post-bleaching event), representing a decrease of 98% across all depths. 

Forereef coral communities at Jarvis Island during the 2015–

2016 bleaching event, Photo: Woods Hole Oceanographic 

Institution/Cohen Lab.

Forereef coral communities at Jarvis Island in 2006 before 

the bleaching event, Photo: NOAA Fisheries/Bernardo 

Vargas-Ángel.

Red turf algae growing over dead and damaged coral 

at Jarvis Island in 2016 after the bleaching event, Photo: 

NOAA Fisheries/Bernardo Vargas-Ángel.
47

Time series of percent coral cover (2001–2016) 

from two complementary data sets, illustrate 

the catastrophic mortality that occurred in 

the mid-depth (6–18 m) reef habitats (Fig. 27). 

The mass mortality of the coral community 

may have negative impacts elsewhere in the 

ecosystem. NOAA is currently studying not 

only how changes in coral cover are affecting 

the islands, but also how other biological 

aspects associated with the thermal stress 

have changed. A more comprehensive 

publication addressing these changes is 

forthcoming. Through the continuance of 

long-term monitoring, NOAA will quantify the 

impacts of the 2015–2016 El Niño on the coral 

reef ecosystem at Jarvis and track recovery. 

While Jarvis showed severe heating and 

severe coral mortality due to the 2015–

2016 El Niño, Baker and Howland were less 

exposed to high temperature anomalies and 

qualitative reports from 2017 surveys show 

no major in coral cover (quantitative results 

pending). As the frequency of these high 

temperature events is projected to increase 

in coming years, it is important to track how a 

coral reef ecosystem system with few human 

impacts, such as Jarvis Island, responds to 

climate events. 

Figure 27. Time series of 

percent coral cover for 

forereef strata at mid-depths 

(6–18 m) at Jarvis Island 

from 2001 to 2012 benthic 

towed-diver surveys (green) 

and from 2015 to 2016 REA 

StRS surveys (red). 

Figure 26. Sea Surface Temperature (SST) at Jarvis Island from 11/28/2000 to 10/13/2016. Data Source: NOAA 

Coral Reef Watch 50-km Virtual Stations, 2000. 

24

25

26

27

28

29

30

31

2002 2004 2006 2008 2010 2012 2014 2016

TEMPERATURE (°C )

BLEACHING THRESHOLD

MAX MONTHLY MEAN TEMP

2000

JARVIS

0

10

20

30

20022004200620082010201220142016

Towed Diver Survey

2000

REA StRS

PERCENT COVER (%)
48

JOHNSTON ATOLL

Johnston Atoll was impacted by human presence more than any other island within 

the PRIMNM. The U.S. Navy dredged and filled the atoll to expand Johnston, making 

it an essential fueling depot for military aircraft and submarines (Rauzon, 2016; Coles 

et al., 2001). Johnston became a busy terminal during World War II (Rauzon, 2016; 

Magier et al., 2012). In 1958, President Kennedy initiated nuclear weapon testing 

at Johnston. In 1962, the Bluegill Triple Prime test failed and spilled americium and 

plutonium across the atoll. The contaminated sand was raked into a pile now referred 

to as “Mount Pluto.” In 1969, the U.S. military removed its chemical weapon stockpile 

from Johnston after an accidental leakage of VX nerve gas in Okinawa (Rauzon, 2016). 

The Johnston Atoll Chemical Agent Disposal System (JACADS) was created in 1971, 

and incinerators and disassembly units were built on the downwind side of the island 

in 1985 (Rauzon, 2016; Magier et al., 2012; Coles et al., 2001). 

By 2000, JACADS had successfully destroyed 4 million pounds of toxic chemicals 

on Johnston, including 5,600 bombs, 13,300 land mines, 43,600 mortars, 72,300 

rockets, and 277,800 projectiles. However, 30,000 gallons of herbicide Agent Orange 

were reported to have leaked into the soil (Rauzon, 2016). The JACADS facility was 

dismantled after the mission was completed (Rauzon, 2016; Magier et al., 2012). 

Johnston Atoll was decommissioned as a military base and most of the buildings were 

removed by 2004. Although there were multiple ecological disturbances experienced 

at Johnston Atoll, there is not enough baseline information to quantify the impacts 

of chemical contaminants on coral reef health (Johannes and Betzer, 1975). The 

sediments and fish in the northwest region of Johnston Island near the detonation 

areas and where the Agent Orange was stored exhibited the highest concentration 

of chemical pollutants. Contaminants in fish tissues were also higher at sites with 

polluted sediments (Lobel and Lobel, 2008). However, recent studies reveal that the 

remaining herbicide Agent Orange in the soil no longer poses significant ecological 

risks to the atoll (Lobel et al., 2003). 

Johnston Atoll Chemical Agent Disposal System (JACADS) building,

Photo: U.S. Army Chemical Materials Agency.

Barrels of Agent Orange in storage at Johnston Atoll circa 1976, 

Photo: U.S. Government. 
49

Disease Occurrence

Pacific RAMP surveys conducted in 2005–2006 revealed that the coral 

disease occurrence was significantly higher at Johnston than any other 

island in the PRIMNM (Vargas-Ángel, 2009). While the anthropogenic 

disturbances at Johnston have not been directly linked to higher 

coral disease occurrence, the low occurrence of coral disease at other 

islands within the PRIMNM could suggest that the higher coral disease 

occurrence at Johnston may be associated with the past environmental 

disturbances. Notably, sites with closest proximity to environmental 

stressors (such as Agent Orange storage sites, explosive detonation 

areas, open burn pits) exhibited the highest levels of coral disease 

prevalence for all diseases at Johnston. Of the coral diseases present at 

Johnston, white-syndrome is particularly concerning, as it leads to rapid 

tissue loss. White-syndrome occurred primarily at Johnston Atoll with 

one case of white-syndrome at Wake (Vargas-Ángel, 2009).

Above left: Skeletal growth anomalies on a colony of Montipora at Johnston Atoll, 

Photo: NOAA Fisheries/Bernardo Vargas-Ángel; Above: White-syndrome observed on 

Acropora cytherea during a benthic survey at Johnston Atoll in 2017, Photos: NOAA 

Fisheries/Brett Schumacher.
50

KINGMAN REEF

Kingman Reef is notable for its remarkably high fish biomass 

and high coral cover, but also for recurrent outbreak level 

populations of the corallivorous crown-of-thorns (Acanthaster 

planci) sea stars. Kingman Reef is also known for its large 

population of giant clams (Tridacna maxima and Tridacna 

squamosa).

Crown-of-thorns Sea Stars 

Crown-of-thorns sea stars (COTS) are coral-eating invertebrates 

that can inflict devastating impacts to the ecological integrity of 

coral reefs. COTS outbreaks can alter coral community structure 

and functioning (Colgan, 1987; Pratchett, 2007), promote 

macroalgal growth (Moran, 1986; Bradbury et al., 1985), and 

affect fish population dynamics (Williams 1986, Hart 1996). 

CREP implements towed-diver surveys to assess the status of 

COTS populations; densities greater than 1,500 organisms 

km-2 are considered outbreak conditions (Moran, 1992). COTS 

populations at Kingman have consistently exhibited outbreak 

levels at multiple locations around the reef since the inception 

of the surveys in 2002 (Fig. 28). The backreef region of Kingman 

Reef experienced the highest COTS densities with populations 

reaching more than 10,000 organisms km-2. Although Kingman 

Reef is not a high island with terrestrial runoff, high nutrient 

loadings and specific climatic and ecological conditions 

are correlated with COTS outbreaks across the Indo-Pacific 

(Timmers, 2012). Despite persistent COTS outbreaks, Kingman 

has relatively high coral cover and relatively low macroalgal 

cover, per 2014–2015 REA and towed-diver surveys (Fig. 18).

Figure 28. Crown-of-thorns (COTS) sea star outbreaks where densities exceeded 1500 organisms 

per km2

. Densities were calculated from towed-diver surveys at Kingman Reef conducted 

from 2001 to 2015. Colors represent different survey years. COTS at Kingman have historically 

demonstrated higher densities within the backreef reef zone. 

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CROWN-OF-THORNS DENSITY KINGMAN

Two COTS prey on coral at Kingman Reef, Photo: NOAA Fisheries/Bernardo Vargas-Ángel; 

Close-up of coral predation, Photo: NOAA Fisheries/James Morioka.
51

Figure 29. Mean giant clam densities (organisms per 100 m 2) from towed-diver surveys at 

Kingman Reef. Towed-diver surveys indicate highest concentration of these clams in the 

southeastern clam garden.

0 21

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GIANT CLAMS DENSITY

Mean Interpolated Density

Giant Clams per 100 m2

Giant Clams

Giant clams are a valuable food source and exports of clam meat 

coupled with shell harvesting are linked to their stock depletion. 

Habitat degradation and decreases in spawning success, as giant 

clam abundance declines, are also exacerbating population 

decreases (Teitelbaum and Friedman, 2008). Tridacna maxima

and T. squamosa, both found at Kingman, are listed as species of 

“least concern” by the International Union for Conservation of 

Nature (IUCN) (Wells 1996). Their status, however, has not been 

evaluated by the IUCN since 1996. A petition was submitted to 

the Secretary of Commerce by the National Marine Fisheries 

Service to protect giant clams, including T. maxima and T. 

squamosa under the Endangered Species Act, and results are 

still pending (Meadows, 2016). 

Extant species of giant clams are only found in the IndoPacific region (Newman and Gomez, 2002). These filter feeders 

form symbiotic relationships with photosynthetic algae, 

zooxanthellae that transfer carbon to host tissues (Klumpp 

et al., 1992). The zooxanthellae need sunlight to perform 

photosynthesis, thus giant clams are found in depths up to 

20 meters and prefer clear, oceanic waters where light can 

penetrate to the bottom (Meadows, 2016). Their growth is 

limited by nitrogen in the environment, and addition of organic 

or inorganic nitrogen in the form of ammonium or nitrate can 

stimulate tissue growth (Hawkins and Klumpp, 1995). 

Giant clams at Kingman Reef, Photo: NOAA Fisheries/James Morioka.

KINGMAN
52

Giant clams provide numerous ecological 

services to reefs. Predators, scavengers, 

and other feeders rely on their tissues, 

zooxanthellae discharges, and wastes for 

food. Their shells and mantle cavities allow 

for the colonization of epibionts, small 

organisms which live on the surface of their 

tissues. Furthermore, water filtering allows 

them to mitigate eutrophication. Giant 

clams also produce calcium carbonate shell 

material that is eventually incorporated into 

the reef framework (Neo et al., 2015). Toweddiver surveys revealed densities as high as 

105 organisms 100 m-2 located within the 

southeastern clam garden; this is equivalent 

to about 1 clam for every square meter of reef 

habitat. Mean densities within this area for all 

survey years ranged from 50 to 85 clams 100 m-2, or about 5–8 clams 10 m-2 (Fig. 29). These 

are the highest giant clam densities observed 

across the Pacific Islands region in Pacific 

RAMP surveys. 

 Giant clams at Kingman Reef, 

Photo: NOAA Fisheries/Kelvin Gorospe.
53

Monoculture of Rhodactis howesii at Palmyra Atoll in 2008, 

Photo: NOAA Fisheries. 

PALMYRA ATOLL

In 1991, the longline vessel, F/V Hui Feng No. 1, ran aground on the western 

terrace of Palmyra Atoll (USFWS, n.d.). The shipwreck led to leaching of 

iron, a limiting ocean nutrient, which fueled the proliferation of the invasive 

corallimorph Rhodactis howesii (Work et al., 2008; Kenyon, 2011). Multiple means 

of reproduction (sexual, budding, fragmentation, and fission) allow Rhodactis 

to quickly spread, smothering and killing the surrounding corals. At Palmyra, 

the spread of Rhodactis rapidly transformed the shipwreck reef area from a 

species-rich coral assemblage into a dense, monotypic stand of corallimorphs 

(Kenyon, 2011). Surveys indicated that in 2005–2006, the corallimorph outbreak 

extended 50–100 m from the ship and coral cover was estimated at 30% around 

the shipwreck (Work et al., 2008). By 2007, the corallimorph population had 

spread out to about 1100 m from the ship, and the surrounding coral cover 

surrounding had decreased to 1%. At the height of the invasion, prior to the 

shipwreck removal in 2013, the corallimorph invasion carpeted over 3 km2

 (741 

acres) of reef once dominated by reef-building corals (Work et al., 2008). 

Due to the devastation of the reef on this remote and relatively pristine atoll, 

the U.S. Fish and Wildlife Service removed the shipwreck as the first step in 

restoring the reef by cutting off the nutrient supply, a necessary resource for 

Rhodactis. The Hui Feng No. 1 wreck site was declared clean and free of debris on 

December 31, 2013 (USFWS, n.d.). Along with the shipwreck removal, the U.S. 

Fish and Wildlife Service performed restoration efforts with the goal to remove 

70% of the corallimorph by 2016 (Kenyon, 2011). Only partial removal occurred, 

and monitoring is ongoing to track the recovery process. Despite this invasion, 

island-wide mean coral cover and fish biomass were comparable to the other 

islands in the PRIMNM, and the Coral Reef Condition Index had a similar score 

(84) as neighboring Kingman Reef (86). Vibrant Acropora community not affected by corallimorph infestation in 

Palmyra Atoll in 2015, Photo: NOAA Fisheries. 
54

WAKE ATOLL

Two large fish species of interest in the Indo-Pacific 

are the humphead wrasse (Cheilinus undulatus) and 

bumphead parrotfish (Bolbometopon muricatum). 

The humphead wrasse is the largest member of the 

wrasse family and can reach a maximum length of 

2 m and weight of 190 kg (Sadovy et al., 2003). The 

bumphead parrotfish is the largest herbivorous and 

corallivorous fish on coral reefs, and can reach 1.5 m 

in length and weigh over 75 kg (Muñoz et al., 2014). 

Populations of both of these ecologically important 

species have declined in parts of their range over the 

last several decades (Kobayashi, et al., 2011; Sadovy 

et al., 2003). The bumphead parrotfish is a highlyprized fishery target and cultural resource, and the 

humphead wrasse is among the most prized in the 

live reef-fish trade and has considerable cultural 

value (Muñoz et al., 2014; Sadovy et al., 2003). Both 

fish species are particularly sensitive to fishing 

pressure, and due to their population decline, 

humphead wrasse and bumphead parrotfish are 

IUCN Red Listed as Endangered and Vulnerable, 

respectively. They are also species of concern for 

the National Marine Fisheries Service. 

Bumphead parrotfish (Bolbometopon muricatum) at Wake Atoll, 

Photo: NOAA Fisheries/Kevin Lino.
55

Humphead wrasse and bumphead parrotfish at 

Wake Atoll, Photo: NOAA Fisheries/Kevin Lino.

Figure 30. Number of individual humphead 

wrasse and bumphead parrotfish observed 

per fore-reef towed-diver transect segment 

from 2005 to 2014 at Wake Atoll. Bubble sizes 

represent the number of sightings and are 

colored by the representative year. 

Among the PRIMNM, Wake is notable for having a relatively low large fish biomass; however, the sightings of these two large species of concern 

are more common at Wake. The total number of sightings of humphead wrasse recorded on transect per year was 67 (2005), 34 (2007), 18 (2009), 

24 (2011), and 3 (2014) (Fig. 30 left). The total number of sightings of bumphead parrotfish sighted on transect per year was 51 (2005), 62 (2007), 

221 (2009), 40 (2011), and 5 (2014) (Fig. 30 right). Both humphead and bumphead abundance were lower in 2014 than in other years, but it is not 

clear whether those represent real population declines or are instead caused by some short-term phenomena at the time of the 2014 surveys. 

Any decline of bumpheads at Wake would be substantial, as Wake densities have been higher than at other U.S. Pacific Islands. Specifically, 

mean abundance of bumphead parrotfish at Wake over the five survey years was 2.8 individuals per hectare, whereas their abundance at the 

other 5 U.S. Pacific islands recorded by NRCMP surveys averaged less than 0.1 individuals per hectare over the same time period.

In addition to possible temporal trends, there are also spatial patterns in bumphead parrotfish abundance. Over several years of surveys, the 

CREP team has observed bumphead parrotfish concentrated around the northwest corner of the atoll, which is thought to be the spawning 

aggregation area for this species (Muñoz et al., 2014). These spatial observations helped identify an area with high bumphead abundance, 

which allowed researchers to study mating and spawning aggregation behaviors and develop crucial baselines of population density, sex ratio 

composition, and productivity of a spawning aggregation in a place where bumphead parrotfish are not exploited. 

HUMPHEAD WRASSE BUMPHEAD PARROTFISH

2005

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56

CONCLUSIONS

Standardized ecological and climatological monitoring 

surveys conducted by CREP are focused on long-term 

trends of ecosystem health and status across the entire 

Pacific. Overall, the Pacific Remote Islands Marine 

National Monument fare well when compared to other 

islands in the U.S. Pacific, often having both higher coral 

cover and higher fish biomass. The reef ecosystems are 

largely intact due to their remote location and relative 

absence of human presence. While these islands are not 

subjected to direct human pressures such as land-based 

sedimentation or fishing, they are significantly affected 

by climate change and recurring climate patterns 

such as El Niño-Southern Oscillation. Climate change, 

especially rising ocean temperatures, remains a major 

threat to the Monument and may impact the health of 

the reef ecosystems. To track possible changes in the 

future, it is necessary for CREP to continue their Pacificwide monitoring program. Additionally, marine debris 

and invasive species are a growing threat to these areas, 

despite their remote location. Thus, monitoring these 

risks may help to inform management in the future. 

School of sea chubs at Wake Atoll, Photo: NOAA Fisheries/Paula Ayotte.
57

Pencil urchin at Kingman Reef, Photo: NOAA Fisheries/Charles Young.

ACKNOWLEDGEMENTS

The authors would like to thank the dedicated scientists from the 

CREP, our many partners, and the officers and crews of the NOAA 

Ships Hi‘ialakai, Oscar Elton Sette, and Townsend Cromwell over the 

past 17 years for their outstanding efforts, often in challenging 

conditions, to collect the interdisciplinary data used in this report. 

We also thank the NOAA Coral Reef Conservation Program, 

especially Jennifer Koss and Justine Kimball, the NOAA Ocean 

Acidification Program, especially Libby Jewett and Dwight Gledhill, 

the NOAA Fisheries Office of Habitat Conservation, especially Anita 

Pritchett and Tauna Rankin, and the Pacific Islands Regional Office 

for guidance and financial support. We thank Forest Rohwer and 

the Rohwer and Wegley-Kelly Lab at San Diego State University 

for their collaboration in monitoring the microbial communities of 

coral reefs. This booklet was greatly advanced by the partnership 

with the Bren School of Environmental Science and Management, 

University of California, Santa Barbara, that provided support for five 

student co-authors (Boyle, O’Reilly, Schafer, Koenig, and De Anda) 

that worked on this as part of the Master of Environmental Science 

and Management program. Constructive suggestions provided 

by Hoku Johnson of PIFSC and L. Hokulani Ka‘aekuahiwi Pousima, 

Samantha Brooke, Heidi Hirsh, and Richard Hall of the Pacific 

Islands Regional Office helped with the structure of this booklet. 

Data support came from Troy Kanemura and Kevin Trick of PIFSC. 

Finally, we would like to acknowledge the many great suggestions 

for improvement from partners at the U.S. Fish and Wildlife Service. 
58

ACRONYMS

ARMS Autonomous Reef Monitoring Structure

AVHRR Advanced Very High Resolution Radiometer

BMU Bioerosion Monitoring Unit

CAU Calcification Accretion Unit

CCA crustose coralline algae

CREP Coral Reef Ecosystem Program

CTD conductivity, temperature and depth

DHW degree heating weeks

IUCN International Union for Conservation of Nature

JACADS Johnston Atoll Chemical Agent Disposal System

MODIS Moderate Resolution Imaging Spectroradiometer

MPA marine protected area

NCEAS National Center of Ecological Analysis and Synthesis

NCRMP National Coral Reef Monitoring Program

NOAA National Oceanic and Atmospheric Administration

Pacific RAMP Pacific Reef Assessment and Monitoring Program

PIFSC Pacific Islands Fisheries Science Center

POES Polar Operational Environmental Satellites

PRIMNM Pacific Remote Islands Marine National Monument

REA Rapid Ecological Assessment

SPC stationary-point-count method

SST sea surface temperature

StRS depth-stratified random sampling

TOAD Tethered Optical Assessment Device

USCRTF U.S. Coral Reef Task Force

Heller’s barracuda (Sphyraena helleri) at Jarvis Island, 

Photo: NOAA Fisheries/Kevin Lino.
59

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