Tampa Bay Estuary Program 

Technical Report #07-00 

A SUMMARY OF SEAGRASS COVERAGE 

DATA FOR TAMPA BAY 

DATA REPORT: 1997 

FINAL REPORT 

August 2000 
A SUMMARY OF SEAGRASS COVERAGE 

DATA FOR TAMPA BAY 

DATA REPORT: 1997 

Prepared for: 

Tampa Bay Estuary Program 

Mail Station I-1/NEP 

100 8th Avenue SE 

St. Petersburg, FL 33701 

Prepared by: 

11 55 Eden Isle Drive NE 

St. Petersburg, FL 33704 

August 2000 
ACKNOWLEDGMENTS 

This report was prepared by Janicki Environmental, Inc. under Contract No. T-98-06 for the 

Tampa Bay Estuary Program. Mr. Dick Eckenrod and Ms. Holly Greening of the TBEP 

provided helpful comments. We thank Ms. Diana Burdick of the Southwest Florida Water 

Management District for her responsiveness and helpfulness in obtaining necessary data for 

the completion of this report. The Emergent and Submerged Habitat Subcommittee of the 

TBEP has been most helpful in its comments and direction for this effort, including review 

comments from Dr. Tom Cuba, Dr. Robin Lewis, Mr. Roger Johansson, and Mr. Walt 

Avery. 

NOTE FROM TBEP STAFF 

The most recent aerial photographs used by the Southwest Florida Water Management 

District (SWFWMD) to generate the mapping products in this data report were taken in 

1996-1 997. The SWFWMD is currently (at the time of this printing) photointerpreting 

aerial photographs taken in 1999. To provide timely interpretation of progress towards 

seagrass restoration goals, interpretation is not included in this data report, but will be 

discussed when the 1999 photointerpretation results are available. 

This report serves a both the SWFWMD and TBEP data report for the 1996 Tampa Bay 

seagrass coverage. 
TABLE OF CONTENTS 

ACKNOWLEDGMENTS 

1 

2 

3 

4 

5 

I NTRO D U CTlO N 

1 .1 Objectives 

1.2 Importance of Seagrasses in Tampa Bay 

1.3 Establishing the Seagrass Target for Tampa Bay 

METHODS 

RESULTS 

3.1 Bay-wide Summary of Trends 

3.2 

3.3 

3.4 Comparison of Spatial Characteristics 

Bay Segment Summary of Historical Trends 

Trends in Seagrass Coverage (1 990 to 1996) 

of 1950 and 1996 Seagrass Coverages 

CONCLUSIONS 

REFERENCES 

.. 

II 

1-1 

1-2 

1-2 

1-2 

2-1 

3-1 

3-1 

3-5 

3-1 3 

3-1 7 

4-1 

5-1 
INTROD UCTION

The Comprehensive Conservation and Management Plan (CCMP) of the Tampa Bay 

National Estuary Program (TBNEP) established the restoration of seagrasses in the bay to 

levels similar to those observed in the 1950's as one of its primary goals. Seagrasses are 

very important to the health of the bay ecosystem, and are thus of concern to those who 

manage this important resource. The TBNEP identified seagrasses as an excellent indicator 

of overall bay health. Seagrasses provide critical habitat for many of the bay's important 

biological resources, including finfish, shellfish, and benthos. 

Seagrass losses have been particularly apparent since 1950 and were due to a variety of 

factors, including dredge and fill projects, poor water clarity, altered bay hydrodynamics, 

and prop scarring (Lewis and Estevez, 1988; Wade and Janicki, 1993). Seagrass restoration 

rate is a function of many variables, including water quality, physical factors such as prop 

scarring and currents, and location of seagrass beds in relation to offshore transverse 

sandbars (Sargent et al., 1995; Sargent et al., 1996). Additionally, sustained cold weather 

can be detrimental to the rate of restoration. Seagrasses in Tampa Bay may be subject to 

biological damage as well, such as that due to Labyrinthula, a microorganism associated 

with seagrass disease. The Tampa Bay Estuary Program (TBEP) Technical Advisory 

Committee (TAC) recognizes that these and other factors may affect progress towards 

reaching adopted seagrass restoration goals, and is currently initiating actions which will 

assist with addressing factors in addition to water clarity and quality (including the 

initiation of measuring the depth of water at various seagrass beds around the bay, and the 

monitoring of potential seagrass disease). Actions needed to address additional factors, 

such as the bay-wide effects of prop scarring or the location of various seagrass beds, will 

be included in discussions of future monitoring needs. 

To address the issue of seagrass habitat loss, recommended seagrass protection and 

restoration targets were developed (Janicki et al., 1 995). Seagrass restoration targets were 

determined by comparing 1990 seagrass extent to that observed in 1950. Seagrass 

restoration targets were defined as those portions of Tampa Bay that had seagrasses in 

1950, did not have seagrasses in 1990, and had not been permanently altered to preclude 

restoration of seagrasses. The establishment of the bay-wide seagrass restoration target was 

dependent upon the availability and quality of bathymetric data (Janicki et al., 1995). The 

restoration targets were defined as areas that had lost seagrass coverage from 1950 to 1990 

and were illuminated by at least 20.5% of the incident subsurface light. 

Based on the results of the Janicki et al. (1995) study, the TBNEP TAC recommended 

seagrass restoration and protection goals to the TBNEP Management Committee. The 

TBNEP Management and Policy Committees adopted a minimum seagrass acreage goal of 

38,000 acres bay-wide. This goal includes protection of existing seagrasses estimated at 

25,600 acres in 1992 and a restoration target of an additional 12,350 acres. The TBNEP 

Management and Policy Committees also adopted a recommendation that progress 

towards seagrass acreage goals be reported to the Management Board every fifth year. 

1-1 
1.1 Objectives 

This report is an element of the data review and analysis performed by the Estuary Program 

to determine the status of seagrass restoration as a result of management activities designed 

to improve water quality in Tampa Bay. This data report examines the areal extents of 

seagrasses in Tampa Bay for in 1950, 1990, 1992, 1994, and 1996. The specific objective 

of this report is to provide an analysis of trends in seagrass areal extent baywide and by bay 

segment through 1996. Interpretation of progress towards seagrass restoration goals will be 

deferred until the 1999 photointerpretation results are available. Figure 1 displays a 

location map for the bay, including the bay segments. ArcView seagrass coverages for 

1950, 1990, 1992, 1994, and 1996 are available on the accompanying CD, which also 

contains the TBEP 1950 and current era shoreline coverages and bay segment boundaries. 

1.2 Importance of Seagrasses in Tampa Bay 

Seagrasses in Tampa Bay provide critical habitat for recreationally and commercially 

important fish and invertebrate species. Seagrasses in Florida provide juvenile nursery and 

adult feeding areas for red drum, spotted seatrout, spot, silver perch, sheepshead, snook, 

shrimp, and the bay scallop (Zieman and Zieman, 1989). Seagrass meadows are also 

important feeding areas for the Florida manatee. Seagrasses serve to improve water quality 

by reducing nutrients in the water column and are an important component of the energy 

and nutrient cycles in coastal environments. 

Five species of seagrasses are found in Tampa Bay. These are turtle grass (Thalassia 

testudinurn), manatee grass (Syringodium filiforme), shoal grass (Halodule wrightii), 

widgeon grass (Ruppia maritima), and star grass (Halophila engelmannii) (Lewis et al., 

1985). Increases in seagrass bed extents in Tampa Bay are typically accomplished by 

vegetative growth and propagule colonization. Propagules are defined as any portion of a 

seagrass plant that is capable of colonizing a new site, and include seeds and plant 

fragments with leaves and roots ((Fonseca et al., 1998). 

In Tampa Bay, seagrasses typically grow at depths no deeper than six to eight feet. Light is 

one of the limiting factors on the depth at which seagrasses can be found. Light 

requirements for growth vary by seagrass species. Turtle grass, the most common seagrass 

species in Tampa Bay, has an estimated light requirement of 20.5% of the incident 

subsurface light (Dixon and Leverone, 1995). For the purposes of seagrass restoration 

target setting, this was assumed to be the minimum light requirement for seagrasses in 

Tampa Bay (Janicki and Wade, 1996). 

1.3 Establishing the Seagrass Target for Tampa Bay 

To establish a seagrass restoration target for Tampa Bay, a benchmark time period was 

needed. The 1950 period was selected as the benchmark period for historical seagrass 

coverage, given that this was the earliest period for which a complete data set existed and 

this period preceded the most rapid population growth in the Tampa Bay watershed. The 

1-2 
areal coverage of the 1950 seagrass beds was developed using data collected by the 

Florida Department of Natural Resources (FDNR) and the U.S. Fish and Wildlife Service 

(USFWS). Seagrass meadows were mapped from 1 :24,000-scale color photography, and 

obtained in digital form from the FDNR. A GIS coverage of the data was created, and 

horizontally rectified to geographically coincide with mapped data for the time period 

(Janicki and Wade, 1995). 

The 1950 seagrass coverage was compared with the 1990 seagrass coverage using GIS 

technology and the best available bathymetry for 1990. The seagrass restoration target for 

Tampa Bay was derived from comparison of these data sets (Janicki et al., 1995). The 1990 

seagrass coverage data were obtained from the Southwest Florida Water Management 

District (SWFWMD) Surface Water Improvement and Management (SWIM) Program. 

SWFWMD developed the GIS coverage from photo-interpretation of 1 :24,000-scale aerial 

photography flown in December 1990. 

A GIS coverage of bathymetry was developed using hydrographic soundings data from the 

NOAA National Geophysical Data Center that contained more than 350,000 data points 

collected during the years 1947-1958 in the Tampa Bay area (Janicki et al., 1995). The 

point soundings and shoreline delineation were used to interpolate a bathymetric GIS 

coverage utilizing Triangular Irregular Network interpolation software from ESRl (1 993) 

(Janicki et al., 1995). 

The 1950 GIS seagrass coverage was overlain with the 1990 GIS seagrass coverage to 

determine where seagrass losses had occurred. The areas from which seagrasses were lost 

were overlain on the 1990 bathymetry and shoreline coverages to identify those areas 

where restoration might be expected. Those areas that had been dredged or filled since 

1 950 were classified as non-restorable. The seagrass restoration acreage was estimated by 

the difference in the 1950 and 1990 coverages less these non-restorable areas (Janicki et 

al., 1995). Based on the results of this study, the TBNEP Management and Policy 

Committees adopted a minimum seagrass acreage goal of 38,000 acres bay-wide, 

including the protection of 25,650 acres and restoration of an additional 12,350 acres 

(TBNEP, 1996). 

As noted above, evaluation of progress toward goals will be conducted once the most 

recent photointerpretation products (1 999) are available. 
Egmont 

RRA CEIA BAY 

RIVER 

Figure 1. Tampa Bay segments and locations. 

1-4 
2 METHODS 

Aerial photography of seagrasses in the bay has been gathered approximately every two 

years since 1988 by the SWFWMD, resulting in seagrass coverages for 1988, 1990, 1992, 

1994, and 1996. Some of the 1988 areas mapped as seagrasses were later found to 

actually represent attached macro-algae. From 1990 on, the aerial photography was field 

checked to verify presence of seagrasses (Kurz et al., 1999). For the purposes of this data 

report, only the SWFWMD seagrass coverages for 1990, 1992, 1994, and 1996 are 

utilized, as the seagrass coverages from each of these years were field checked for 

accuracy. The 1990-1996 period includes all seagrass coverages for which data were 

collected using consistent methods, and is the period during which progress towards TBEP 

seagrass goals is estimated. 

The SWFWMD aerial photography was 1 :24,000-scale true color, and with the exception 

of the 1996 photography, was obtained during the late faII/early winter time period 

(November-February) when water clarity in Tampa Bay is typically greatest (Kurz et al., 

1999). The month(s) during which the aerial photos were taken varied from sampling 

period to sampling period (Tomasko, 1999), so that the greatest water clarity conditions 

would prevail, as follows: 

1990 - November, December 1990 

1992 - February 1993 

1994 -January 1995 

1996 - April, May 1997. 

To develop GIS coverages from the aerial photography, the SWFWMD analyzed the 

photos using zoom transfer methodology registered to U.S. Geological Survey (USGS) 7.5- 

minute quadrangles. The minimum mapping unit for seagrasses was 0.5 acres. Seagrass 

polygons were delineated on mylar overlays and transferred to an ARC/INFO database. 

The SWFWMD coverages for 1990, 1992, 1994, and 1996 contain two classes of seagrass 

coverage, patchy and continuous. For the purposes of this data report, the acreages of both 

classes were combined to yield total seagrass acreage. The coverages containing both 

classes of seagrass acreage can be found on the CD accompanying this report. The 

seagrass classes are given by the coverage attribute "Lev4", where Lev4 = 91 13 denotes 

patchy seagrass, and Lev4 = 91 16 denotes continuous seagrass. 

In addition to the SWFWMD seagrass photography, the City of Tampa Bay Study Group 

has been monitoring seagrasses in Hillsborough Bay since 1986. The data from this 

monitoring program for Hillsborough Bay do not show the same areal extent of seagrasses 

as those from the SWFWMD photography, possibly due to the different mapping 

techniques utilized by the two monitoring programs. These data are discussed later in this 

document, in Section 3.3. 

2-1 
Additional aerial photography exists for 1982, as described in Lewis et al. (1985). The 

methodology used in developing the 1982 seagrass coverage was different than that 

employed by the SWFWMD for the 1990, 1992, 1994, and 1996 seagrass coverages, so 

that direct comparisons between 1982 coverages and later coverages were not made. The 

1990, 1992, 1994, and 1996 SWFWMD seagrass coverages provide the best dataset for 

examining changes in seagrass coverage in Tampa Bay. 

Bay segment-specific seagrass acreages for 1990, 1992, 1994, and 1996 were estimated by 

intersecting the SWFWMD seagrass coverages with the segmentation scheme for Tampa 

Bay. Changes in seagrass acreage between years resulted from the difference in seagrass 

acreage within each bay segment. Trends in bay-wide seagrass acreage were estimated 

using the 1950 seagrass acreage and the 1990, 1992, 1994, and 1996 acreages. Bay 

segment-specific trends were based on changes in seagrass acreage within each bay 

segment. Changes in seagrass acreage from 1990 to 1996, for the entire bay and for each 

bay segment, were estimated, providing recent seagrass changes from coverages developed 

utilizing the same methodology for seagrass delineation. These recent changes in seagrass 

acreage provide the TBEP with data for tracking progress towards its seagrass goals. 
3 RESULTS 

Seagrass beds covered approximately 40,400 acres in Tampa Bay during the 1950 baseline 

period (Figure 2). Of this total, approximately half was found in Old Tampa Bay (OTB) and 

Boca Ciega Bay (BCB) (10,700 acres and 10,800 acres, respectively), with most of the 

remainder found in Middle Tampa Bay (9,600 acres) (MTB) and Lower Tampa Bay (LIB) 

(6,100 acres). Hillsborough (HB) Bay contained approximately 2,300 acres, and Terra Ceia 

Bay (TCB) and Manatee River (MR) contained approximately 700 and 200 acres, 

respectively. 

v, 

2 

Y 

12,000 

10,000 

8,000 

6,000 

4,000 

2,000 

0 

/I I 

OTB HB MTB LTB BCB TCB MR 

Figure 2. 1950 seagrass acreage for Tampa Bay segments. 

3.1 Bay-wide Summary of Trends 

The estimated seagrass acreage in Tampa Bay in 1990 was approximately 25,200 acres 

(Figure 3). In 1992, seagrasses covered approximately 25,800 acres (Figure 4), increasing 

to 26,500 acres in 1994 (Figure 5) and 26,900 acres in 1996 (Figure 6). Acreages for all 

segments are rounded to the nearest 10 acres in Figures 3-6. These bay-wide seagrass 

acreages are shown by year in Table 1. The following figures present maps of the seagrass 

areas: Figure 7 - 1950, Figure 8 - 1990, Figure 9 - 1992, Figure 10 - 1994, and Figure 11 - 

1996. ArcView seagrass coverages for 1950, 1990, 1992, 1994, and 1996 are available on 

the accompanying CD. 
Year 

1950 

1990 

I 1992 I 25,750 I -1 4,670 I + 530 

Seagrass Acreage Net Change Since 1950 Net Change Since 1990 

40,420 - - 

_ 25,230 -1 5,200 

I 1994 I 26,520 I -1 3,900 I + 1,290 

Figure 3. 

0 

OTB HB MTB LT B BCB TCB MR 

7,000 

6,000 

5,000 

v) 4,000 

2! ' 3,000 

2,000 

1,000 

1990 seagrass acreage for Tampa Bay segments. 

3-2 
v) 

2 

Y 

7,000 

6,000 

5,000 

4,000 

3,000 

2,000 

1,000 

0 

OTB HB MTB LT B BCB TCB MR 

Figure 4. 1992 seagrass acreage for Tampa Bay segments. 

8,000 

7,000 

6,000 

5,000 

v) 

4,000 Y 

3,000 

2,000 

1,000 

0 

OTB HB MTB LT B BCB TCB MR 

Figure 5. 1994 seagrass acreage for Tampa Bay segments. 

3-3 
v) 

2 

Y 

8,000 

7,000 

6,000 

5,000 

4,000 

3,000 

2,000 

1,000 

0 

Figure 6. 

OTB HB MTB 

1996 seagrass acreage for Tampa 

LTB BCB TCB MR 

Bay segments. 

3-4 
3.2 Bay Segment Summary of Historical Trends 

The greatest losses between 1950 and 1990 occurred in Old Tampa Bay (approximately 

5,100 acres), Middle Tampa Bay (approximately 4,300 acres), and Boca Ciega Bay 

(approximately 4,000 acres). Lower Tampa Bay seagrass coverage increased by 

approximately 100 acres during the 1950 to 1990 time period. Hillsborough Bay 

experienced the largest percentage decrease, losing approximately 98% of its seagrass 

coverage over the time period. The changes in seagrass coverage between 1950 and 1990 

are shown in Figure 12, with the restorable seagrass acreage signified by declines in 

seagrass acreage. Figure 13 shows the change in seagrass acreage between 1990 and 

1996. The following describes the trends in seagrass coverage by bay segment. 

Old Tampa Bay 

1950 - Seagrass coverage in Old Tampa Bay during the 1950 baseline period was 

extensive, covering the entire shoreline with the exception of some parts of the 

northwestern portions of the segment. Safety Harbor contained only a small area of 

seagrass, and the northern shoreline of Mobbly Bay had no seagrass. Another area 

of shoreline with no seagrasses extended from north of the western end of the 

Courtney Campbell Causeway to an area about halfway to Safety Harbor. The total 

seagrass acreage for the segment was approximately 10,700 acres in 1950. 

1990 - By 1990, net seagrass losses of approximately 5,100 acres had occurred, leaving 

only 5,600 acres in Old Tampa Bay. Some of the largest areas sustaining losses 

included the eastern shoreline of the Old Tampa Bay, where dredging and filling 

had occurred. The western shoreline of the segment had also experienced seagrass 

losses, especially north of the Howard Frankland Bridge, due to dredging and filling 

and likely due to water quality impacts of runoff from the adjacent urban area. The 

area of seagrasses around the mouth of Mobbly Bay was also greatly reduced in 

size. 

1992 - By 1992, net seagrass coverage in Old Tampa Bay had increased since 1990 by 

approximately 300 acres, to a total of approximately 5,900 acres. A large portion of 

this increase occurred inside and around the western mouth of Mobbly Bay. The 

increased seagrass acreage in Mobbly Bay was largely due to Halophila (Johansson, 

2000). Increased seagrass coverage was also found south of the eastern end of the 

Courtney Campbell Causeway, where seagrasses had increased shoreward from 

those found in 1990. 

1994 - Seagrass coverage in Old Tampa Bay during 1994 showed very little change from 

that in 1992. Overall, a net increase of approximately 30 acres of seagrass 

occurred. A small decrease in seagrass cover was noted just north of the western 

end of the Howard Frankland Bridge, due north of Cabbage Patch Point. 

3-5 
1996 - Between 1994 and 1996, net seagrass acreage in Old Tampa Bay declined by 

approximately 150 acres, to approximately 5,800 acres. Seagrass losses were most 

evident in the Mobbly Bay area, which had seen a large increase in seagrass acreage 

from 1990 to 1992. Losses also occurred along the northeastern shore north of the 

Courtney Campbell Causeway. Several small areas of increased seagrass coverage 

were also found, however. The seagrass cover north of Cabbage Patch Point, where 

losses had occurred between 1992 and 1994, increased between 1994 and 1996. 

Increases in seagrass coverage were also found both north and south of the mouth 

of Allen Creek, with offshore expansion of 1994 seagrass beds. 

Table 2 summarizes the seagrass acreage data for Old Tampa Bay. The acreages presented 

in tabular format are rounded to the nearest 10 acres. From 1950 to 1990, seagrass 

coverage in Old Tampa Bay declined by approximately 5,100 acres. From 1990 to 1996, 

net seagrass coverage in Old Tampa Bay increased by approximately 200 acres. 

Seagrass Acreage easuremen Net Change Since 1990 

Hillsborough Bay 

1950 - Seagrass coverage in Hillsborough Bay in 1950 totaled approximately 2,320 acres. 

Large areas of seagrasses were found along the eastern shore of the bay from East 

Bay southward towards the Alafia River, and from the mouth of the Alafia River 

southward through The Kitchen and towards Big Bend. Along the western shore of 

Hillsborough Bay, smaller seagrass beds were found off Gadsden Point, from Catfish 

Point northward to Ballast Point, and north of Ballast Point. Seagrasses were also 

found in McKay Bay. 

1990 - By 1990, Hillsborough Bay contained only 47 acres of seagrasses, most of which 

was in the mouth of The Kitchen. Extensive dredging and filling had resulted in the 

loss of seagrasses in the Big Bend area and in the Port Sutton area. Only very small 

remnants of the western shore seagrass beds of 1950 existed in 1990. 
1992 - Seagrass acreage in 1992 was approximately the same as in 1990, although the 

distribution of seagrasses within Hillsborough Bay was not the same as in 1990. 

The seagrass beds found at the mouth of The Kitchen in 1990 had declined slightly 

in extent, and the seagrass patches along the western shore of Hillsborough Bay had 

increased slightly in extent. 

Year Seagrass Acreage 

1950 2,321 

1990 47 

1992 46 

1994 147 

1996 193 

1994 - Seagrass coverage in 1994 in Hillsborough Bay showed a net increase of more than 

100 acres over that found in 1992, totaling 147 acres. The seagrass beds at the 

mouth of The Kitchen, which had decreased in size from 1990 to 1992, increased 

in size from 1992 to 1994. Seagrasses, primarily Ruppia (Johansson, 2000), were 

found along the eastern shore of the bay between the Port Sutton peninsula and 

Archie Creek, and the seagrass beds found along the western shore in 1992 

increased in size. 

Net Change Since Previous 

Measurement Net Change Since 1990 

(Gains : Losses) 

- - 

-2,2 74 - -1 -1 

+ 101 +l00 

+ 46 +146 

(+24: -25) 

(+ 106: -5) 

(+60 : -14) 

1996 - By 1996, seagrass beds in Hillsborough Bay covered 193 acres. The seagrass beds 

between the Port Sutton peninsula and Archie Creek, along the eastern shore, had 

increased in extent, as had the beds near the mouth of The Kitchen. The seagrass 

beds found along the western shore between Catfish Point and Ballast Point also 

increased in size. There were no significant seagrass losses between 1994 and 

1996 in this segment. 

Table 3 summarizes the seagrass coverage data for Hillsborough Bay. The acreages 

presented in tabular format are rounded to the nearest acres, given the relatively small 

amount of seagrasses found in Hillsborough Bay. By 1990, seagrass area declined by 

approximately 2,300 acres from the benchmark period of 1950. From 1990 to 1996, 

seagrass coverage in Hillsborough Bay increased by approximately 150 acres (Table 3). 

~ 

Middle Tampa Bay 

1950 - The seagrass beds in Middle Tampa Bay comprised almost one-quarter of all the 

seagrasses found in the bay in 1950, covering approximately 9,600 acres. Extensive 

3-7 
seagrass beds occurred along the eastern shoreline from the Big Bend area 

southward to the mouth of the Little Manatee River, into the mouth of the river, and 

southward into Cockroach Bay and towards Piney Point. Along the western shore, 

seagrass beds were found along the shoreline of northeast St. Petersburg to the 

North Shore area, and again from just north of Coquina Key southward to Pinellas 

Point. The region along the southern shoreline of the lnterbay Peninsula also 

contained extensive seagrass beds. 

1990 - Seagrass acreage in this segment had a net decline of approximately 5,300 acres by 

1990, with the greatest reductions in acreage occurring along the eastern shore. 

From the Big Bend area southward to the Little Manatee River, only the shoreward 

seagrass beds remained, with the exception of one small area offshore. Similarly, 

south of the river, only the most shoreward seagrass beds remained, although the 

losses here were not as severe. Along the western shore, dredging and filling for the 

Venetian Isles area resulted in seagrass losses, with some offshore losses south of 

downtown St. Petersburg. In the northern part of the segment, along the lnterbay 

Peninsula, seagrass losses were not as severe, with only the most offshore areas 

showing a decline in seagrass coverage. 

1992 - Between 1990 and 1992, seagrass acreage in Middle Tampa Bay showed a slight 

net decline, by approximately 40 acres. No obvious changes were found when 

comparing the 1990 and 1992 seagrass coverages. 

1994 - By 1994, seagrass beds in Middle Tampa Bay had a net increase of more than 500 

acres from those observed in 1992. New seagrass beds appeared southwest of 

Apollo Beach, and the 1992 seagrass beds between the mouth of the Little Manatee 

River and Cockroach Bay spread shoreward. It should be noted that the attached 

macro-algae Caulerpa was also observed north and south of the channel into 

Cockroach bay during the early 1990’s (Johansson, 2000). An increase of seagrass 

acreage occurred just west of Gadsden Point south of the lnterbay Peninsula. 

1996 - Between 1994 and 1996, the Middle Tampa Bay segment lost seagrasses, with a net 

seagrass acreage reduction of more than 240 acres to approximately 5,500 acres. 

The major areas of loss included the beds west of Gadsden Point south of the 

lnterbay Peninsula, and north of the mouth of the Little Manatee River, around 

Pelican Cove. 

Table 4 summarizes the seagrass coverage data for Middle Tampa Bay. The acreages 

presented in tabular format are rounded to the nearest 10 acres. From 1950 to 1990, 

seagrass coverage in Middle Tampa Bay declined by approximately 4,300 acres, while 

from 1990 to 1996, seagrass coverage showed a net increase of approximately 200 acres. 

3-8 
Year 

1950 

1990 

1992 

Net Change Since Previous 

(Gains : Losses) 

Seagrass Acreage Measu re men t Net Change Since 1990 

9,600 - - 

5,310 -4,290 - 

5,2 70 -40 -40 

(+ 340 : -380) 

Lower Tampa Bay 

1994 

1996 

1950 - Lower Tampa Bay contained approximately 6,100 acres of seagrasses in 1950. 

Almost the entire nearshore area of this segment supported seagrass beds, with the 

exceptions of a few areas near the mouth of the bay. 

5,780 +510 + 470 

5,540 -240 + 230 

(+ 680 : -1 70) 

(+ 380 : -620) 

1990 - Very little change was evident in the total seagrass extent found in Lower Tampa 

Bay by 1990. Seagrass acreage had a net increase of only a small increment (40 

acres), with most of this found along the northwestern shoreline of the segment. 

Seagrass increases were found south of Pinellas Point and in association with the 

Skyway Bridge causeway, with some seagrass losses found along the southeastern 

shoreline, west of Terra Ceia Bay and near the mouth of the bay. 

1992 - Seagrass acreage showed a net increase of approximately 100 acres in Lower Tampa 

Bay between 1990 and 1992. An area of new seagrasses was observed west of the 

mouth of Bishop Harbor offshore of the beds found in 1990. There were no other 

obvious changes in seagrass coverage. 

1994 - Seagrass acreage in Lower Tampa Bay showed a net decline of approximately 40 

acres between 1992 and 1994. Losses of seagrasses occurred southwest of Pinellas 

Point, and along the southeastern shore of Mullet Key. 

1996 - Between 1994 and 1996, seagrass acreage showed a net increase in Lower Tampa 

Bay of approximately 200 acres. The seagrass beds west of the mouth of Bishop 

Harbor first seen in 1992 were not found in the 1996 coverage. Seagrass bed 

coverage north of the mouth of Anna Maria Sound extended northeastward into 

Tampa Bay. Some increase in seagrasses was found east of Egmont Key. The 

seagrasses along the southeastern shore of Mullet Key that had disappeared between 

1992 and 1994 were again found in 1996, although they did not cover the same 

extent as in 1992. It is not known if the decrease in seagrass acreage along this 

portion of Mullet Key between 1992 and 1994, and the following increase between 

3-9 
1994 and 1996, is an artifact of the photointerpretation or if these changes 

represented “real world” conditions. Seagrass coverage in Lower Tampa Bay in 

1996 totaled approximately 6,400 acres. 

Net Change Since Previous 

Year Seagrass Acreage Measurement 

(Gains : Losses) 

1950 6,100 

1990 6,140 + 40 

- 

1992 6,240 +l00 

(+120:-20) 

1994 6,200 -40 

1996 6,3 80 +180 

(+80: -120) 

(+510 : -330) 

Table 5 summarizes the seagrass coverage data for Lower Tampa Bay. The acreages 

presented in tabular format are rounded to the nearest 10 acres. From 1950 to 1990, 

seagrass coverage in Lower Tampa Bay increased by approximately 40 acres. From 1990 

to 1996, seagrass coverage in Lower Tampa Bay increased by approximately 200 acres. 

Net Change Since 1990 

- 

- 

+l00 

+ 60 

+ 240 

Boca Ciega Bay 

1950 - There were approximately 10,800 acres of seagrasses in Boca Ciega Bay in 1950. 

The interior of Mullet Key was almost completely covered with seagrass beds, as 

was the area around Cabbage Key and Pine Key. Seagrass beds covered what is 

now the area of lsla del Sol, extending eastward to the mainland north of Maximo 

Channel. Seagrasses were found in Clam Bayou, and along the west coast of 

Gulfport nearly to Treasure Island. Seagrass beds also extended along the 

northeastern shore of Boca Ciega Bay, southeast of Conch Key. 

1990 - By 1990, seagrass coverage in Boca Ciega Bay showed a net decline to 

approximately 6,800 acres, with some areas lost to dredge and fill activities. This 

was especially evident along the eastern shore of Treasure Island and Redington 

Shores, with very few small patches of seagrass found from lsla del Sol northward. 

1992 - Between 1990 and 1992, seagrass coverage in Boca Ciega Bay sowed a net increase 

of approximately 140 acres. A small area of seagrasses was found north of lsla del 

Sol, which had expanded since 1990. An area of seagrasses was also found east of 

Conch Key, at the northern end of Boca Ciega Bay, where none were found in 

1990. 
1994 - Seagrass coverage in 1994 showed a net increase of 170 acres of seagrasses over 

that found in 1992. The most significant expansion was found in the northern 

portion of Boca Ciega Bay, where the patch east of Conch Key extended 

southeastward along the shoreline of mainland. Additional gains occurred at the 

southeastern mouth of Long Bayou, around Dog Leg Key. 

Year 

1950 

1990 

1992 

1994 

1996 

1996 - A net increase in seagrass coverage of 580 acres was found between 1994 and 

1996 in Boca Ciega Bay, to a total of approximately 7,700 acres. The area near 

Conch Key showed expanded seagrass coverage, with lesser expansions of the area 

around Indian Key, the area east of the Skyway Bridge Causeway, and the seagrass 

beds west of Summer Resort Key. 

Net Change Since Previous 

(Gains : Losses) 

10,800 - - 

6,810 -3,990 - 

Seagrass Acreage Measurement Net Change Since 1990 

6,950 +140 +140 

7,120 + 170 +310 

7,700 + 580 + 890 

(+160: -20) 

(+ 300 : -1 30) 

(+ 650 : -70) 

Table 6 summarizes the seagrass coverage data for Boca Ciega Bay. From 1950 to 1990, 

seagrass coverage in Boca Ciega Bay decreased by approximately 4000 acres. From 1990 

to 1996, seagrass coverage in Boca Ciega Bay increased by approximately 900 acres. 

Terra Ceia Bay 

1950 - In 1950, seagrasses covered approximately 700 acres in Terra Ceia Bay. Seagrasses 

were found along the southern shoreline from the mouth of Terra Ceia Bay eastward 

into Clambar Bayou and Champlain Bayou. Seagrasses also extended along the 

eastern shore from the Snead Island Cutoff northward to Palmetto Point, covering 

Peterson Bayou. Seagrasses were also found along the northwestern shore, from 

Sea Breeze Point to Flounder Pass. 

1990 - Seagrass coverage in Terra Ceia Bay experienced a net increase of approximately 

300 acres between 1950 and 1990. Seagrasses beds had declined in size in 

Peterson Bayou, but increased in size from Sea Breeze Point to Flounder Pass, and 

extended west of Flounder Pass along the southern shore of Rattlesnake Key to the 

mouth of Terra Ceia Bay. Seagrasses had also extended along the eastern shore of 

3-11
Snead Island, and beds were found north of Sea Breeze Point near the northern end 

of Terra Ceia Bay. 

Table 7. Terra Ceia Bay seagrass acreages. 

Net Change Since Previous 

Year Seagrass Acreage Measurement Net Change Since 1990 

(Gains : Losses) 

1950 700 - - 

1990 1,000 + 300 - 

i 1992 1,000 0 0 

1992 - There was no net change in total seagrass coverage between 1990 and 1992. 

1994 

1996 

1994 - Total seagrass acreage did not change between 1992 and 1994, but some changes 

in location of beds were found. The 1994 coverage showed no seagrasses north of 

Sea Breeze Point, and the bed found in 1992 between Bird Key and Gus Point had 

expanded in size. 

1,000 0 0 

9 70 -30 -30 

(0 : 0) 

(+ 30 : -60) 

1996 - Seagrass coverage in Terra Ceia Bay experienced a net decline of approximately 30 

acres between 1994 and 1996. No obvious changes in seagrass bed size are seen 

in the 1996 coverage. The total seagrass coverage in Terra Ceia Bay in 1996 was 

approximately 970 acres. 

Table 7 summarizes the seagrass coverage data for Boca Ciega Bay. The acreages 

presented in tabular format are rounded to the nearest 10 acres. From 1950 to 1990, 

seagrass coverage in Terra Ceia Bay increased by approximately 300 acres. From 1990 to 

1996, seagrass coverage in Terra Ceia Bay decreased by approximately 30 acres. 

Manatee River 

1950 - In 1950, approximately 200 acres of seagrasses were found in the Manatee River. 

These were found along the northern bank from just upstream of Hooker Point 

downstream to Hooker Point, and downstream of McKay Point. Along the southern 

shore, seagrasses extended from McNeil Point downstream. The largest seagrass 

beds were near the mouth of the river 

1990 - Seagrass coverage in the Manatee River experienced a net increase of 160 acres 

between 1950 and 1990. Along the northern shoreline, seagrasses had extended 

upstream past Point Ogden, from Hooker Point downstream to McKay Point, and 

3-1 2 
from McKay Point to the mouth of the river. 

shoreline extended from Point Pleasant downstream to the mouth of the river. 

Seagrasses along the southern 

Year 

1950 

1992 - Total seagrass acreage in 1992 was the same as that for 1990, with no obvious 

changes apparent. 

Net Change Since 

(Gains : Losses) 

Seagrass Acreage Previous Measurement Net Change Since 1990 

200 - - 

1994 - By 1994, seagrass coverage in the segment showed a net increase of 10 acres. 

1992 

1994 

1996 - The seagrass coverage in 1996 remained unchanged from that found in 1994. 

360 0 0 

370 +10 +10 

(0 : 0) 

(+10:0) 

Table 8 summarizes the seagrass coverage data for Manatee River. The acreages presented 

in tabular format are rounded to the nearest 10 acres. From 1950 to 1990, seagrass 

coverage in the Manatee River increased by approximately 160 acres. From 1990 to 1996, 

seagrass coverage in the Manatee River remained relatively unchanged. 

1996 370 0 +10 

(+lo:-10) 

I 1990 I 360 I +160 I - I 

3.3 Trends in Seagrass Coverage (1 990 to 1996) 

To examine recent trends in Tampa Bay seagrass acreage, the most appropriate comparison 

is between the seagrass coverage in 1990 (Figure 3) and that in 1996 (Figure 6). This 

comparison is made over the longest time span for which data were collected using the 

same methods, as discussed previously. In 1990, approximately 25,200 acres of seagrasses 

were found in Tampa Bay (Janicki et al., 1995). From 1990 to 1996, areas from which 

seagrasses were lost totaled approximately 2,400 acres, while new seagrass beds covered 

approximately 4,000 acres (Figure 13). This resulted in a net gain of approximately 1,700 

acres of seagrasses bay wide. Over half of this gain occurred in Boca Ciega Bay, with the 

remainder distributed more or less evenly among the four mainstem segments of the bay. 

The following discusses recent trends in seagrasses by bay segment. 

3-1 3
Old Tampa Bay

In 1990, seagrasses covered approximately 5,600 acres in Old Tampa Bay. By 1996, 

seagrass coverage had a net increase of approximately 200 acres, to approximately 5,800 

acres, an increase of 3.6%. 

Three areas displayed appreciable loss of seagrasses, including the areas northwest of the 

eastern end of the Courtney Campbell Causeway, along the northeastern shore of Old 

Tampa Bay, and around the southern end of the peninsula separating Safety Harbor from 

Mobbly Bay. Seagrass losses were also found along the western shore of Old Tampa Bay, 

north of the western end of the Howard Franklin Bridge and north of Cabbage Patch Point. 

increases in seagrass coverage were greatest along the western shore of Old Tampa Bay. A 

large patch of seagrass formed south of the western end of the Howard Frankland Bridge. 

More new seagrasses were found north and south of Largo Inlet, extending from the mouth 

of the Cross Bayou Canal almost to the Courtney Campbell Causeway. Between the 

Courtney Campbell Causeway and Safety Harbor, seagrass beds found in 1990 extended 

both shoreward and offshore. Some new small seagrass beds were found in Safety Harbor 

in 1996, along the western and eastern shores, and up into Mobbly Bay. Along the eastern 

shore of Old Tampa Bay, very few areas of new seagrasses were found, with the most 

extensive extending from Rocky Point to south of the mouth of Fish Creek. 

Hillsborough Bay 

Only 47 acres of seagrasses were found in Hillsborough Bay in 1990. This acreage 

increased to 193 acres by 1996. The net increase in coverage of 146 acres is similar to that 

found in Old Tampa Bay over the same time period, and this 311 % increase over the 

1990-1 996 time period was the greatest percentage increase of any bay segment. 

Very few areas lost seagrasses in Hillsborough Bay between 1990 and 1996. Some small 

losses occurred around Green Key, offshore of The Kitchen, and along the western shore of 

Hillsborough Bay. A few small seagrass patches around the Big Bend area were also lost. 

The largest new seagrass area found in 1996 occurred offshore of The Kitchen. The 

seagrass beds found in 1990 had extended northward, and into Hog and Hominy Cove. 

Another small patch of new seagrasses was found south of the mouth of Bullfrog Creek. 

Additional new seagrass beds along the eastern shore of Hillsborough Bay were found 

between the mouth of Archie Creek and the Port Sutton peninsula. Along the western 

shore of Hillsborough Bay, between Catfish Point to just north of Ballast Point, new small 

scattered seagrass beds were found near the shore. 

Data from the City of Tampa Bay Study Group also show increased in seagrass acreage in 

Hillsborough Bay, although the acreages reported are not the same as those obtained from 

the SWFWMD photography. The SWFWMD coverages yield an increase of 146 acres by 

1996 over the 47 acres reported in 1990. The City of Tampa monitoring program found 

3-1 4 
only 5 acres of seagrass in 1990, 13 acres in 1992, 49 acres in 1994, and 100 acres in 

1996 (Kurz and Avery, 1999). 

Middle Tampa Bay

Seagrasses covered approximately 5,300 acres in Middle Tampa Bay during 1990. By 

1 996, seagrasses covered approximately 5,500 acres. 

In Middle Tampa Bay, most seagrass losses between 1990 and 1996 occurred along the 

northeastern shore of the segment, along the offshore edge of the 1990 seagrass beds. This 

was most prominent from north of the mouth of the Little Manatee River to the southern 

shore of Apollo Beach. Other offshore edge seagrass losses occurred south of the mouth of 

the river, southward past Little Cockroach Bay. Some small seagrass losses were found 

along the offshore edge of the beds south of the lnterbay Peninsula, and scattered along the 

northwestern shore of the segment. 

The most significant increases in Middle Tampa Bay seagrass acreage from 1990 through 

1996 were found along the southeastern shore of the segment. These increases were 

generally in the shoreward direction from those beds found in 1990, especially in Little 

Cockroach Bay and south of the mouth of Cockroach Bay, in South Stop. Other increases 

were found inshore of the 1990 beds along the southern shore of the lnterbay Peninsula, 

and in Bayou Grande along the northwestern shore of the segment. 

Lower Tampa Bay 

Lower Tampa Bay contained approximately 6,100 acres of seagrasses in 1990. By 1996, 

approximately 6,400 acres of seagrasses were found in the segment. 

Seagrass losses from 1990 to 1996 in Lower Tampa Bay occurred primarily along the 

offshore edge of the beds along the southeastern shore of the segment. Small areas of 

seagrass loss were found from north of the southern end of the Skyway Bridge to south of 

Rattlesnake Key. 

Increases in seagrass acreage were generally distributed around the coastline of Lower 

Tampa Bay. The most significant single new seagrass bed was found north of the mouth of 

Anna Maria Sound. The seagrass bed found east of Egmont Key in 1990 had extended 

southward by 1996. Other new seagrass beds, that were small and dispersed, were found 

along both the southeastern and northwestern shores of the segment. 

Boca Ciega Bay

Boca Ciega Bay contained approximately 6,800 acres of seagrasses in 1990. This acreage 

had increased to approximately 7,700 in 1996, accounting for 900 acres of the net baywide 1,700-acre increase in seagrass coverage. In Boca Ciega Bay, this increase amounted 

to a 13% increase in coverage. 

3-1 5
Areas from which seagrasses were lost between 1990 and 1996 in Boca Ciega Bay were 

dispersed in the southern region of the segment, with the total area amounting to 

approximately 150 acres. The largest single loss was found southwest of Pinellas Point, 

where approximately 20 acres were lost along the western side of a bed. 

New seagrasses were found covering approximately 1,000 acres in 1996. Approximately 

half the increases were found in the southern portion of Boca Ciega Bay, where 1990 

seagrass beds had expanded. Most significantly, the northern portion of the segment 

experienced two large seagrass bed expansions. At the head of Boca Ciega Bay, east of 

Conch Key and southward along the northeastern shore of the segment, a large new area of 

seagrasses was found, accounting for approximately 200 acres of the new seagrasses found 

since 1990. Along the eastern mouth of Long Bayou, around Dog Leg Key, a large bed 

extended from around the Jungle area northward to the Seminole Bridge and about half the 

distance across the mouth of the bayou. This area of seagrass accounted for almost 90 

acres of the increase in the segment. New seagrasses were found along the western shore 

near the mouth of the bayou as well. 

Terra Ceia Bay

In 1990, seagrasses in Terra Ceia Bay covered approximately 1,000 acres. Very little 

change was found in 1996, when 970 acres of seagrasses were found. 

Seagrass losses in Terra Ceia Bay were found near the mouth of the bay, along the 

southeastern shore of the bay, and near the head of the bay, north of Seabreeze Point. The 

losses in the northern region were mainly along the northwestern shore, at the mouth of 

Frog Creek, with some losses around the mouth of McMullen Creek as well. These losses 

in the northern portion of Terra Ceia Bay amounted to approximately 20 acres. 

Only one significant area of seagrass increases was found. This occurred on the western 

side of the seagrass bed found in 1990 between Gus Point and Bird Key, where seagrass 

coverage increased by approximately 20 acres from the 1990 bed. 

Manatee River 

Very little change in seagrass coverage was found in the Manatee River between 1990 and 

1996. The 1990 coverage of 360 acres increased to 370 acres by 1996. Small areas of 

seagrass losses were found near the mouth of the river along the southern shoreline, and 

some small losses were found around McKay Point on the northern shore of the river as 

well. Two areas of seagrass increase were found, one near McNeil Point along the 

southern shore of the river, and the other along the northern shore of the river between the 

two bridges for US 41. 

3-1 6
3.4 Comparison of Spatial Characteristics of 1950 and 1996 Seagrass Coverages 

Segment 

Old Tampa Bay 

Hillsborough Bay 

Middle Tampa Bay 

Lower Tampa Bay 

Boca Ciega Bay 

Manatee River 

Terra Ceia Bay 

A comparison of the spatial characteristics of the 1950 and 1996 seagrass coverages was 

made to estimate the extent of the areas that supported seagrasses in 1950 but did not 

support seagrasses in 1996. A polygon-by-polygon comparison of the 1950 and 1996 

seagrass coverages (less non-restorable areas) results in the maps shown in Figures 14 and 

15. The coverages used to create these maps are available on the CD accompanying this 

report. 

Area 

(acres) 

5,660 

1,670 

4,060 

1,270 

1,660 

120 

40 

Table 9 presents the breakdown by bay segment of the area of bay bottom that supported 

seagrasses in 1950 that did not support seagrasses in 1996, as shown in Figure 14. These 

data show that approximately two-thirds of the areal difference between the 1996 coverage 

polygons and the 1950 coverage polygons is found in Old Tampa Bay and Middle Tampa 

Bay. 

Segment 

Old Tampa Bay 

Hillsborough Bay 

Middle Tampa Bay 

Lower Tampa Bay 

Boca Ciega Bay 

Terra Ceia Bay 

Manatee River 

Total 1950 Seagrass Area Non-Restorable Area 

(acres) (acres) 

1 0,700 1,230 

2,320 510 

9,600 1,260 

6,100 690 

10,800 3,560 

700 150 

200 30 

Portions of the 1950 seagrass acreage were in areas that are non-restorable due to dredging 

and filling operations. The total and non-restorable acreages based on the 1950 seagrass 

coverage and bay bottom alterations since then are shown in Table 10 for each segment. 

Table 10. Total and non-restorable seagrass acreage based on 1950 seagrass 

coverage and subseauent alterations of the bav bottom. 

3-17 
Table 11 presents the breakdown by bay segment of the area of bay bottom that supported 

seagrasses in 1996 that did not support seagrasses in 1950, as shown in Figure 15. These 

data show that approximately 8,190 acres of the 26,900 acres of seagrasses found in 1996 

were found in areas that did not support seagrasses in 1950. The acreages shown in Table 

11 result from the differences in acreages between the 1996 acreages and the restorable 

acreages not supporting 1996 seagrasses. These acreages correspond to those identified in 

Figure 15. The coverages used to create Figure 15 are available on the CD accompanying 

this report. 

Segment Area 

(acres) 

Old Tampa Bay 

Hillsborough Bay 

Middle Tampa Bay 

Lower Tampa Bay 

Terra Ceia Bay 

Manatee River 

Boca Ciega Bay 

1,960 

50 

1,250 

2,240 

1,910 

540 

240 









4 CONCLUSIONS 

In 1950, seagrasses covered approximately 40,420 acres in Tampa Bay. By 1990, seagrass 

acreage in the bay had declined to approximately 25,230 acres. The causes of this decline 

include declining water quality, physical factors such as dredge and fill projects, prop 

scarring, and altered bay hydrodynamics, and location of seagrass beds in relation to 

offshore transverse sand bars. 

Net increases in seagrass acreage occurred bay-wide from 1990 to 1996. In 1990, the baywide seagrass acreage was 25,230 acres. Seagrass acreage increased to 25,750 acres in 

1992, to 26,520 acres in 1994, and to 26,920 acres in 1996. From 1990 to 1996, 

seagrasses extended over an additional 1,690 acres in the bay. 

Increases in seagrass acreage within each bay segment varied from 1990 to 1996. More 

than half of the increase, approximately 900 acres, occurred in Boca Ciega Bay, where the 

northern portion of the segment had significant gains in seagrass acreage. In Boca Ciega 

Bay, seagrass acreage increased by 13% from 1990 to 1996. The Old Tampa Bay, Middle 

Tampa Bay, and Lower Tampa Bay segments experienced increases of more than 200 acres 

each, or about 4% within each segment. An increase of approximately 150 acres was 

found in Hillsborough Bay, resulting in a four-fold increase in seagrass acreage in that 

segment. The Manatee River segment gained almost no seagrass acreage during the 

period, and the Terra Ceia Bay segment lost approximately 30 acres of seagrass beds (3%). 

The rate of increase in seagrass acreage from 1990 to 1996 was approximately 1 %per year 

bay-wide. Seagrass restoration rate is a function of many variables, including water quality, 

physical factors such as prop scarring and currents, and location of seagrass beds in relation 

to offshore transverse sandbars. Additionally, sustained cold weather can be detrimental to 

the rate of restoration. Seagrasses in Tampa Bay may be subject to biological damage as 

well, such as that due to Labyrinthula, a microorganism associated with seagrass disease. 

The TBEP Technical Advisory Committee (TAC) recognizes that these and other factors may 

affect progress towards reaching adopted seagrass restoration goals, and is currently 

initiating actions which will assist with addressing factors in addition to water clarity and 

quality (including the initiation of measuring the depth of water at various seagrass beds 

around the bay, and the monitoring of potential seagrass disease). Actions needed to 

address additional factors, such as the bay-wide effects of prop scarring or the location of 

various seagrass beds, will be included in discussions of future monitoring needs. 

The major findings of this report are summarized as follows: 

0 the 1990 seagrasses covered approximately 2,400 acres in areas where seagrasses 

were not found in 1996; 
0 the 1996 seagrasses covered approximately 4,000 acres in areas where seagrasses 

were not found in 1990; and 

0 the rate of increase in bay-wide seagrass acreage slowed during 1994 to 1996, 

when seagrass acreage increased by approximately 400 acres, compared to the 

increases observed between 1992 and 1994 (700 acres) and between 1990 and 

1992 (600 acres). 

The causes leading to these findings should be the subject of further study. As discussed 

above, the TBEP recognizes that factors other than water quality should be considered 

when examining progress towards seagrass restoration goals. The causes of bay-wide and 

segment-specific seagrass acreage losses and gains should be addressed, so that future 

management decisions can be based on a fuller understanding of the factors involved in 

seagrass recovery in Tampa Bay. 
5 REFERENCES 

Dixon, L.K. and J.R. Leverone. Light requirements of Thalassia testudinum in 

Tampa Bay, Florida. Prepared for: Southwest Florida Water Management District SWIM 

Program. Prepared by: Mote Marine Laboratory. 

1995. 

Janicki, A.J., D.L. Wade, and D.E. Robison. 1995. Habitat protection and restoration 

targets for Tampa Bay. Tech. Pub #07-93, Tampa Bay National Estuary Program. Prepared 

by Coastal Environmental, Inc. 

Johansson, J.O.R. 2000. Personal communication, City of Tampa Bay Study Group. June 

9, 2000. 

Kurz, R.C., and W. Avery. 1999. Chapter 7 - Seagrass Coverage. In "Baywide 

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Kurz, R.C., D.A. Tomasko, D. Burdick, T.F. Ries, K. Patterson, and R. Finck. 1999. 

Summary of recent trends in seagrass distributions in southwest Florda coastal waters. 

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Lewis, R.R. Ill and E.D. Estevez. 1988. The ecology of Tampa Bay, Florida: An estuarine 

profile. U.S. Fish. Wildl. Serv. Biol. Rep. 85(7-18). 132 p. 

Lewis, R.R. Ill, R.G. Gilmore, Jr., D.W. Crewz, and W.E. Odum. 1985. Mangrove habitat 

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Fishery Resources. Florida Chapter of the American Fisheries Society. 

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Sargent, F.J., T.J. Leary, D.E. Kuhl, A.P. Lamb, M.M. Colby, G.M. Macaulay, and P.J.

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Petersburg, FL. 

Tampa Bay National Estuary Program. 1996. Charting the Course for Tampa Bay. Tampa 

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Agency, Region IV. 263 pp. 

Tampa Bay Regional Planning Council (TBRPC). 1986. Habitat restoration study for the 

Tampa Bay Region. Prepared by TBRPC, St. Petersburg, Florida. 283 p. 

5-1 
Tomasko, D.A. 1999. Personal communication. 

Wade, D.L. and A.J. Janicki. 1993. Physical impacts to habitats in Tampa Bay. Tech. Pub. 

#03-93, Tampa Bay National Estuary Program. Prepared by Coastal Environmental, Inc. 

Zieman, R.C. and R.T. Zieman. 1989. The Ecology of the Seagrass Meadows of the West 

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