Analysis of Changes in Seagrass Coverage, 1996-

1999 and 1999-2001, for Anna Maria Sound, 

Sarasota, Roberts, Little Sarasota, and 

Blackburn Bays 

Final Report 

Submitted by: L.K. Dixon and J. S. Perry 

 Mote Marine Laboratory 

 1600 Ken Thompson Parkway 

 Sarasota, FL 34236 

Submitted to: Gary Raulerson 

 Sarasota Bay Nation Estuary Program 

 111 South Orange Ave, Suite 200W 

 Sarasota, FL 34236 

November 20, 2003

MML Technical Report No. 920 

This document is printed on recycled paper and with non-destructive ink. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page iTable of Contents 

Page No

Table of Contents.................................................................................................................. i 

List of Figures........................................................................................................................ i 

List of Tables....................................................................................................................... iii 

List of Appendices............................................................................................................... iii 

Acknowledgments............................................................................................................... iii 

Executive Summary............................................................................................................ iv 

Introduction...........................................................................................................................1 

Methods..................................................................................................................................1 

Study Area .........................................................................................................................1 

Seagrass Mapping .............................................................................................................3 

Change Analysis................................................................................................................3 

Bathymetry ........................................................................................................................6 

Water Quality....................................................................................................................6 

Thermal Extremes ............................................................................................................7 

Detailed Light Record.......................................................................................................9 

Results and Discussion..........................................................................................................9 

Change polygons...............................................................................................................9 

Flight Times.....................................................................................................................14 

Polygon depths ................................................................................................................17 

Segment Water Quality ..................................................................................................22 

Available light..................................................................................................................25 

Temperature....................................................................................................................33 

Summary..........................................................................................................................35 

References............................................................................................................................37 

List of Figures 

Page No

Figure 1. Study area for seagrass change analyses.........................................................2 

Figure 2. Examples of shoreline change and seagrass change that were 

eliminated from consideration. .......................................................................5 

Figure 3. Water quality gradient used to compute mean segment and 

polygon water quality value for the given month ...........................................6 

Figure 4. Selected polygons of seagrass change used for analyses, 1996-

1999. Northern study area............................................................................10 

Figure 5. Selected polygons of seagrass change used for analyses, 1996-

1999. Southern study area............................................................................11 

Figure 6. Selected polygons of seagrass change used for analyses, 1999-

2001. Northern study area.............................................................................12 

Figure 7. Selected polygons of seagrass change used for analyses, 1999-

2001. Southern study area............................................................................13 

Figure 8. Approximate areas covered and dates of the 1996 aerial 

photography. .................................................................................................15 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page iiList of Figures (Continued) 

Page No

Figure 9. Seasonal fluctuation in Thalassia testudinum shoot density and 

biomass, as measured in Tampa Bay. ...........................................................16 

Figure 10. Examples of the variety of coverages under the patchy and 

continuous seagrass designations. Darker tones indicate higher 

biomass values and/or shoot density. White space is equivalent to 

bare bottom. ..................................................................................................16 

Figure 11. Elevations of seagrass polygons of no change, by segment, for 

ë9113-Patchyí and ë9116-Continuousí. ........................................................17 

Figure 12. Elevations of general categories of seagrass change, by segment, 

for 1996-1999................................................................................................18 

Figure 13. Elevations of general categories of seagrass change, by segment, 

for the 1999-2001..........................................................................................18 

Figure 14. Elevations of specific change categories of seagrass for Segments 

5, 6, and 7, for 1996-1999.............................................................................19 

Figure 15. Distribution of polygon depths by general change category for 

Segment 7, 1996-1999. .................................................................................21 

Figure 16. Distribution of polygon depths by general change category for 

Segment 2, 1996-1999. .................................................................................21 

Figure 17. Distribution of total nitrogen by segment for 1999-2001. ............................23 

Figure 18. Distribution of salinity by general change category for Segment 8, 

1996-1999. ....................................................................................................24 

Figure 19. Distribution of salinity by segment for unchanged polygons (9113 

and 9116) during both 1996-1999 and 1999-2001. ......................................24 

Figure 20. Distribution of light fraction at depth by general change category 

for Segment 7, 1996-1999.............................................................................25 

Figure 21. Distribution of light fraction at depth by general change category 

for Segment 10, 1999-2001...........................................................................27 

Figure 22. Distribution of light fraction at depth by specific change category 

for Segment 8, 1996-1999.............................................................................28 

Figure 23. Distribution of polygon depths by specific change category for 

Segment 8, 1996-1999. .................................................................................28 

Figure 24. Mean light fraction at depth for 1996-1999, by segment and 

specific change category. ..............................................................................29 

Figure 25. Mean polygon elevation for 1996-1999 by segment and specific 

change category. ...........................................................................................29 

Figure 26. Light duration parameters for Segment 5 using compensation 

irradiance of 25 μE m2

 sec-1..........................................................................31 

Figure 27. Light duration parameters for Segment 5 using compensation 

irradiance of 200 μE m2

 sec-1........................................................................32 

Figure 28. Time series of modeled temperatures for a single polygon. .........................34 

Figure 29. Time series of modeled water column depths for a single polygon. ............34 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page iiiList of Tables 

Page No

Table 1. Categories of seagrass change. .......................................................................4 

Table 2. Distribution of polygon depths by general change category and 

evaluation of potential for low light or exposure effects based on 

relative depth distribution. ............................................................................21 

Table 3. Distribution of fraction of light at the bottom of the water column 

by general change category and evaluation of potential for low 

light based on depth distributions by change category. ................................27 

List of Appendices 

Page No

Appendix A Distribution of polygon change categories by time period and by 

segment. ......................................................................................................A-1 

Appendix B Distribution of water quality parameters by time period and by 

segment. ......................................................................................................B-1 

Appendix C Period water quality means, mapped by segment.......................................C-1 

Appendix D Time series of water quality parameter for the larger change 

polygons, by time period and by segment. .................................................D-1 

Acknowledgments

This project would not have been possible without the seagrass mapping performed by the 

Southwest Florida Water Management District, the cooperation of their contractor Avineon, 

Inc., the excellent weather archives maintained by Dr. Don Hayward, and the unfailing 

cheerfulness and skill of Ms. Allison Rekow, the cooperation of the entire Chemical Ecology 

Staff, and the support of the Southwest Florida Water Management District and the Sarasota 

Bay National Estuary Program.
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page ivExecutive Summary 

Seagrass mapping performed by the Southwest Florida Water Management was subjected to 

a change analysis between 1996 and 1999 and from 1999 to 2001 with respect to water 

quality and possible exposure effects. Only polygons larger than apparent changes in 

adjacent shorelines (due to accuracy increases) were retained for analysis. Photography in 

different seasons made distinctions between seasonal and interannual changes problematic. 

The study area was within the boundaries of the Sarasota Bay National Estuary Program, or 

from Anna Maria Sound to the Venice Inlet. 

Change polygons were categorized both by general and specific change category and further 

segregated by bay segment. Monthly water quality data for the periods were used to create a 

time series of mean values and departures from segment means for each polygon. 

Bathymetry and attenuation coefficients were combined to calculate available light at the 

bottom of the water column. Water quality data were examined by general and specific 

change category using all data and again using only ëgrowing seasoní values (April-October). 

Detailed light and temperature were modeled for each polygon using an empirically derived 

model of tidally varying depths, attenuation coefficients, insolation records, and a heat flux 

approach. Despite modeling assumptions, relative comparisons of light and temperature 

distributions were permissible between change categories within a given segment, although 

actual exposures could not be assessed. 

Stable patchy polygons were generally deeper in northern Sarasota Bay. Grasses were 

shallower overall in Palma Sola Bay and the southern portion of the study area with less 

difference in depth between stable categories. The depths of stable polygons were also 

significantly and inversely correlated with attenuation coefficient and total nitrogen 

concentrations across the study area. General loss categories (gain, unchanged, or loss) 

indicated that light limitation may have played a role in seagrass losses in eastern Palma Sola 

Bay and Sarasota Bay proper between 1996 and 1999. Very few segments had change 

distribution consistent with light limitation in the 1999-2001 analysis, but light records were 

limited for this time period. Several segments experienced losses in the shallowest polygons, 

consistent with losses due to exposure and dessication and/or thermal extremes. Water 

quality gradients within a given segment were not strong and so provided little explanation 

for seagrass changes within a segment. Also within a given segment, the light levels 

experienced by specific change categories were often contradictory. A specific loss category 

could have experienced a higher light level than a specific gain category, indicating more 

than one factor was responsible for seagrass losses. Salinity effects alone did not appear 

responsible for seagrass losses or gains. 

Detailed light analyses focused on 1996-1999 when data were more complete. When a 

relatively low compensation point was evaluated, all segments recorded significant 

differences in time below compensation by general change category and many were 

consistent with light limitation. The durations of modeled high and low temperatures were 

similar to depth distributions and did not appear to be a controlling factor in either general or 

specific seagrass change. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 1- 

Introduction: 

The Southwest Florida Water Management District (SWFWMD) has performed aerial 

mapping of seagrasses in the major waterbodies within their jurisdiction for a number of 

years and has produced coverages for 1988, 1990, 1992, 1994, 1996, 1999 and 2001. In 

many of the subregions, since the precipitous declines noted between 1950 and 1982, grasses 

have made small but consistent gains in coverage through 1996, with recovery attributed to 

improving water clarity due to reduced nitrogen loading (Johansson and Greening, 1999). In 

comparing 1996 with 1999 data, however, seagrass acreage exhibited declines in many 

regions (Tomasko, 2002). More recently, change analyses for the 1999-2001 time period 

exhibited modest recoveries in some regions and continued losses in others (Tomasko, 2003). 

Climatic conditions between 1996 and 1999 mappings were unusual in that an El Nino/ 

Southern Oscillation event resulted in high rates of rainfall and riverine flows for southwest 

Florida. The seagrass recovery observed between 1988 and 1996 had taken place under 

relatively drier conditions. Except in the mouths of rivers and enclosed bays with riverine 

discharges, salinity was not considered the sole source of seagrass loss. Freshwater 

discharges in southwest Florida are typically highly colored and the resulting reduced water 

clarity of the an El Nino period, potentially coupled with increased epiphytism from higher 

nutrient loading was postulated to have resulted in light levels that were insufficient to 

maintain seagrasses at depth. Since 1998, rainfall and flows were reduced in 1999 and in 

2000 were at the lowest levels since 1960. Flows in 2001 were somewhat larger but were still 

well below 1998 levels. The reduced flows in the period between the 1999 and 2001 

mapping events were expected to allow increased light levels to reach seagrasses and support 

increased seagrass biomass. 

The Project reported here was designed to examine areas of seagrass change within Sarasota 

Bay in relation to the monitored water clarity and clarity components, depth distribution, 

nitrogen concentration as a surrogate for epiphytism, and potential exposure during extreme 

weather events, and to identify likely causes for change. It should be emphasized that the 

project employed a selected subset of all change polygons and there was to be no assessment 

of total acreages of seagrass or change in seagrass. 

Methods: 

Study Area 

The study area consisted of Anna Maria Sound, Sarasota Bay, Roberts Bay, Little Sarasota 

Bay, and Blackburn Bay (Figure 1). Areas directly surrounding the passes were not included 

due to the likelihood of bathymetric change on the flood tidal deltas in these regions. Change 

in coverage was evaluated by bay segment utilizing the Sarasota Bay National Estuary 

Program segmentation scheme (Estevez and Palmer, 1990). A total of 12 segments from 

Anna Maria Sound through Blackburn Bay were evaluated. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

7

6

1

8

2

5

3

10

11

# Sarasota

Bay

#

Palma Sola

Bay

Longboat #

Pass

#

Anna Maria

Sound 7

10

13

11

14

16

New #Pass

#

BigPass

#

Little Sarasota

Bay

#

Blackburn

Bay

#

Roberts

Bay

Venice

Inlet

27°10'27°20'

82°35'82°35'

82°30'82°30'

27°20'

27°20'

27°30'

27°30'

82°40'82°40'

82°35'82°35'

0 2 Miles

Figure 1. Study area for seagrass change analyses.
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 3- 

Seagrass Mapping 

Seagrass mapping was available as Geographic Information System (GIS) coverages from 

SWFWMD. Categories of seagrass were designated as either >Continuousí or ëPatchyí, with 

a minimum mapping unit of 0.5 acres. The time periods used for the project included the 

coverages designated as 1996, 1999, and 2001. (Mapping designations adopted by 

SWFWMD were maintained for this project, regardless of the calendar date of the 

photography.) 

GIS shapefiles were obtained from www.swfwmd.state.fl.us for 1996 and 1999. The 2001 

dataset was in final preparation at this project's commencement and therefore retrieved 

directly from SWFWMD's contractor, Avineon, Inc. with SWFWMDís permission. The 

2001 files are now available at the above mentioned website. The photography effort 

conducted for the 1996 maps covered a wide range of dates between April and October 1997 

due to unfavorable field conditions. The 1999 images were flown in December 1999. The 

2001 photography was flown in January 2002, but an unexpected turbidity plume around 

New Pass and Big Pass prevented interpretation of those areas and the region was reflown in 

January of 2003. The shapefiles for the 2003 effort were obtained from the Sarasota Bay 

National Estuary Program, although comparatively little was used in the change analysis 

since passes were subsequently excluded. Seasonal patterns of biomass which have maxima 

during summer and early fall were expected to complicate the comparison of the 1996 to 

1999 data, while the comparison of 1999 to 2001 should be relatively free of these seasonal 

artifacts. 

Change Analysis 

Change analyses were conducted through the union of two shapefiles into a third shapefile 

which then contained polygons with attributes from both of the original files. Through this 

step, new shapes were created where attributes describe both initial and final conditions. For 

example, if a polygon coded as seagrass in one time period migrated to slightly deeper water 

but was in the same general location in a second time period, the new shapefile would create 

three polygons: a central portion where seagrass was unchanged, regions where seagrass had 

been lost, and regions of gain. 

 

Change categories were created using the original Florida Land Use Codes and Classification 

System codes used to categorize the seagrass coverages. Categories are defined below 

(SWFWMD, 2001): 

ì9113 - Patchy seagrass. This category appears as singular, isolated patches of seagrass 

or extensive areas of patch strands mixed with open bottom. Typically these areas appear as 

round clumps, or as elongated strands mixed with sand. The photosignature for 9113 usually 

has a rough texture when viewed through a stereoscope, and is bluish-gray to almost black 

depending on water depth and turbidity. 9113 can be found on the deeper and shallower 

edges of continuous seagrass beds or can be large and expansive and cover the entire bed.î 

ì9116 - Continuous seagrass. These areas exhibit a continuous and uniform signature. 

Small, (less than one-quarter acre) sandy bottom features may be interspersed within the 

bed, but these areas are not dominant. Areas that appear as continuous beds of seagrass 

communities, regardless of species composition, will be mapped. The photosignature for 

9116 is more smooth than that of 9113 but still has some texture. It also can be bluish-gray 

to almost black, but has only a few areas of open bottom showing through to interrupt the 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 4- 

continuous signature. 9116 usually can be found in the center of large, healthy seagrass beds 

and sometimes runs parallel to the shoreline for hundreds of meters.î

In practice, these designations are often presented as ëContinuousí containing no more than 

25% of unvegetated bottom within the polygon, while ëPatchyí has more than 25% of 

unvegetated bottom within the polygon (Kurz, et al., 1999). The possible changes involving 

seagrass produced eight new categories for analysis under three generalized headings as 

listed in Table 1. 

Table 1. Categories of seagrass change. 

Gain (G) 

 Other-9116 Bare to Continuous 3 

 Other-9113 Bare to Patchy 2 

 9113-9116 Patchy to Continuous 1 

Unchanged (U) 

 No Change No Change(Continuous) 9116 

 No Change No Change(Patchy) 9113 

Loss (L) 

 9116-9113 Continuous to Patchy -1 

 9113-Other Patchy to Bare -2 

 9116-Other Continuous to Bare -3 

Since 1988, slight modifications have improved the SWFWMD seagrass mapping 

techniques, which, while providing increasingly accurate estimates of actual coverage, 

complicate direct comparisons of successive mapping efforts for change detection. The first 

mapping effort in 1988 was conducted using areas of seagrass delineated from photos at a 

1:24000 scale. The 1990 effort was similarly performed and, when compared to 1988 in a 

GIS environment, resulted in numerous ìsliversî of change. The ìsliversî were considered 

artifacts of re-mapping all the seagrass polygons in their entirety, as many of the changes 

were on the order of a pen width. The artifacts could also have been contributed as a result 

of the accuracy of the geo-registration of the individual photos. In the mapping performed 

for subsequent years, changes to a polygon were mapped rather than the entire polygon, thus 

reducing spurious changes. 

The 1999 photography, however, increased the accuracy of ground control points such that 

while mapping accuracy remained at 1:24,000, positional accuracy was increased to 

1:12,000. In addition, previous shorelines were updated. Shoreline changes observed 

between 1996 and 1999 could have reflected true changes, i.e., along unarmored passes, 

beaches or vegetated shorelines. Shoreline changes observed along hardened seawalls or 

protected shorelines, however, were attributed to the increase in positional accuracy. 

Seagrass change polygons were expected to have similar artifacts. A primary task of the 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 5- 

Example of Eliminated Change Polygons

9113 - Patchy, No Change

1 - Bare to Patchy

Coastline Change - Water to Land

Example of Eliminated Change Polygons

9116 - Continuous Seagrass

3 - Bare to Continuous

-3 - Continuous to Bare

Coastline Change - Land to Water

Coastline Change - Water to Land

seagrass change analysis was to segregate true changes in seagrass coverage from those 

resulting from positional accuracy increases, prior to investigating water quality or other 

factors associated with change polygons. Since the 2001 mapping employed the same 

shoreline as used for the 1999 effort, positional accuracies were similar, and so artifacts were 

not expected to be as prevalent in the 1999-2001 change analysis. 

An analysis of shoreline change between 1996 and 1999 was conducted in order to create a 

threshold size above which true seagrass change was probable and not an artifact of the 

higher resolution product or differences in geolocation. Excluding areas where shoreline 

change was possible (passes or inlets), the 95th percentile of all coastline change polygons 

was identified as 0.67 acres. Seagrass change polygons below this threshold were 

automatically eliminated from consideration. 

Many seagrass features, however, were linear in nature, i.e. along channels and the fringes of 

narrow bays to the south of the study area. A small shift in registration of a seagrass polygon 

could produce a large 

(but narrow) change 

polygon, the short axis 

of which could be 

comparable to the 

distance that the 

shoreline had apparently 

moved. Seagrass 

ëchangeí in these 

instances was considered 

spurious. The shoreline 

shifts are clearly 

illustrated in the canal 

systems of Anna Maria 

(Figure 2, left) with the 

shift in the shoreline 

carried over into the 

seagrass changes. 

Figure 2, right, illustrates an area near Midnight Pass. Here, an eastward shift in shoreline 

converted grassbeds to land with a comparable expansion of seagrass. The axis of the 

seagrass change polygon was comparable to that of the shoreline and so was considered not 

true change. Similar examples were present in all segments. 

Accordingly, any polygons that changed from land to grass or grass to land were eliminated. 

Finally, a visual inspection of the remaining polygons was performed. Seagrass change 

polygons were selected if the change in seagrass coverage along the axis of the shift in 

adjacent shorelines was substantially greater than the shoreline change. Comparable 

numbers of seagrass polygons of no change were also selected to include in the analyses, 

using both patchy and continuous categories. 

Figure 2. Examples of shoreline change and seagrass change 

that were eliminated from consideration. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 6- 

Seagrass Polygon

June, 1998 Color (PCU)

15 - 18

18 - 21

21 - 24

24 - 27

27 - 30

Bathymetry 

Bathymetric data were retrieved from the National Ocean Service/National Oceanic and 

Atmospheric Administration Geophysical Data System for Hydrographic Survey Data, Ver. 

4.0. Some 63,000 survey points from the 1950ís were used from thirteen surveys. Data were 

reported to the nearest 0.1 meter. These points were projected from their native geographic 

datum to that used by SWFWMD and a 30x30 meter bathymetric grid interpolated. The 

seagrass change polygons created above were overlaid on top of the grid and a depth 

distribution and mean depth calculated for each change polygon. 

Water Quality 

Monthly water quality data had been collected for Sarasota and Manatee Counties since 

January, 1995 and November, 1995 respectively. Sarasota County data were retrieved 

through June, 2002 from database archives at Mote Marine Laboratory (MML). Manatee 

County data were retrieved from the EPAís STORET (legacy and modern) databases. 

Parameters of interest included light attenuation coefficients, total nitrogen, turbidity, color, 

chlorophyll and salinity. Attenuation coefficients were not available in the northern portion 

of the study area during 2001. Data reported to be less than the detection limit were 

evaluated at one half of the detection limit. Attenuation coefficients were computed from 

raw light readings as necessary. 

Water quality data were segregated into two time periods to span the dates of the aerial 

photography flights. The í96-99í data comprised observations between April 1, 1997, and 

December 31, 1999; the í99-01í 

time period encompassed from 

December 1, 1999 through January 

31, 2001. In both data sets, station 

observations were pooled by month, 

and each month was separately 

contoured and gridded at 30 m by 30 

m resolution. From the resulting 

gridded data, spatial means of both 

individual change polygons and of 

entire segments (Figure 3) were 

computed by month. Polygon 

means were further reduced to 

compute the monthly departure 

between the segment mean water 

quality parameter and the polygon 

mean . water quality parameter, in 

order to capture spatial distributions 

that might exist within a given 

segment. The mean water column depth within individual polygons was also combined with 

the monthly mean attenuation coefficient for the polygon to compute the approximate 

Figure 3. Water quality gradient used to compute 

mean segment and polygon water quality 

value for the given month. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 7- 

fraction of photosynthetically active radiation (PAR, 400-700 nm) available at the bottom. 

The resulting data provided a monthly time series of water quality data within a segment, 

within individual polygons, and the differences between the two. 

 The above water quality data were further segregated to isolate the growing season of April 

through October. The season was identified with reference to seagrass metrics previously 

measured in Tampa Bay and Charlotte Harbor (Dixon and Leverone, 1995; Dixon and 

Kirkpatrick, 1999) under the premise that environmental conditions which can limit 

photosynthesis are of greater importance during warmer than during cooler temperatures 

(Tomasko and Hall, 1999). 

Thermal Extremes 

As a surrogate for the exposure and dessication of seagrass beds, thermal extremes of 

seagrass beds within the Sarasota Bay system were evaluated through the use of a heat flux 

model which incorporated tides and was specific to the depth distribution within individual 

polygons. Hourly predicted tides for Sarasota were obtained from Tides and Currents for 

WindowsTM, Nautical Software, Version 2.5I and referenced to mean lower low water 

(MLLW). Tides measured at the MML facility on New Pass (relative to mean low water, 

MLW) were collapsed to hourly values, and used to compute a tidal offset, measured water 

level less predicted. Large positive or negative offsets were confirmed as reasonable based 

on other weather data (wind speed direction, temperatures, records of tropical storms) or 

discarded if instrumental malfunction was suspected (progressive or step trends in offset 

data). Offsets ranged between -0.4 and 1.0 m. 

Data from 1994-1995 were used to develop an empirical regression model of tidal offset. 

Possible independent terms included barometric pressure, wind speed and wind speed 

squared, wind direction normalized to a variety of compass headings, cumulative wind speed 

squared over a variety of periods from three to eighteen hours, and interactive terms. 

Stepwise regression was used to eliminate terms. The final model incorporated terms for 

barometric pressure and a multiplicative term consisting of the six hour cumulative wind 

speed squared and the sin of the wind direction plus 15  ̊. Standard error of the estimate was 

0.08m. Use of the model with weather data from subsequent years achieved comparable 

accuracies predicting tidal offsets within 0.07-0.09 m (RMS error). Missing wind speed data 

were replaced with the mean of the remaining data, 3.31 m/sec. Missing wind directions or 

barometric readings were replaced with the last observation. The regression model of tidal 

offset was then used with the predicted tides to generate an unbroken tidal record over the 

project period. 

Hourly water column depths over seagrass polygons were then estimated from the predicted 

tides, the modeled tidal offsets, and the polygon elevations determined from gridded 

bathymetric data. The implicit assumption was that water levels fluctuated uniformly across 

the study area, both in amplitude and in timing. This is known not to be the case, but was 

used as an approximation for the following reasons. Timing of tidal amplitude along the 

coast is relatively coherent, and differs by less than 0.5 hours between Venice and Anna 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 8- 

Maria; amplitude differences are on the order of 10% (NOAA, 1994). Regions behind 

barrier islands are likely to lag both in amplitude and in timing, but times of maxima and 

minima are unlikely to lag more than one-quarter of a typical 12 hour semi-diurnal period, 

(i.e., 3 hours). Differences in tidal amplitude are more difficult to assess in the absence of a 

hydrodynamic model, but the subdivision and analysis of the seagrass polygon data by 

segments allow the relative comparison of depths among polygon categories of a given 

segment. 

The heat flux model consisted of the summation of insolation, net longwave radiation 

(infrared) from the water surface, sensible heat flux due to conduction of heat from the water 

to the atmosphere, and latent heat flux due to evaporation. Insolation values were obtained 

from MMLís weather station and were adjusted for the fraction of reflection at the air-water 

interface, determined as a function of solar elevation (Kirk, 1994). Data were reported in 

W/m2

; missing data were replaced with the hourly means from the same calendar days in 

other years. Net longwave radiation, was computed as blackbody radiation at the 

temperature of the water, less water vapor absorption. In practice, black body radiation was 

scaled to achieve annual values near 45-50 W/m2

 as reported for these latitudes (Stewart, 

2002). Missing water temperature data, if unavailable from either the MML station or from 

Venice, were replaced with the daily and hourly means from other years. Sensible heat loss 

was computed as a function of air and water temperature, while latent heat loss from 

evaporation was a function of wind speed and relative humidity. Missing relative humidity 

data were replaced with the mean of other observations. 

The net heat lost or gained was applied in hourly steps to a water column determined from 

elevation and predicted tide plus weather offset. Tidal increases in water column were 

assumed to import water at a temperature given by the MML weather station at New Pass 

and to mix instantaneously with the existing water column. Tidal decreases in water column 

were considered heat lost. Water columns were not allowed to decrease to less than 0.05 m 

and so actual dessication of seagrass tissues was not addressed. Temperatures within a given 

polygon were computed as a linear mixture of the temperature records of differing water 

column depths, combined in proportion to the depth distribution within a given polygon. 

This technique was superior to using mean polygon depths as the thermal fluctuations were 

non-linear with water column depth and shallow polygons exhibited much larger thermal 

variations than deeper polygons under similar ambient conditions. 

The modeling technique, while continuously autocorrecting through the import of thermally 

accurate water with each rising tide, nevertheless adequately represented the thermal 

variations, both diurnal and seasonal, of a large (3.2X106

 m2) polygon of varying depths 

bounding New Pass. The RMS error over a three year period of continuous simulation was 

less than 0.5  ̊C. Polygons located farther from New Pass would be expected to exhibit larger 

seasonal and diurnal fluctuations as the waters of a rising tide would be from shallower, more 

thermally variable parcels of water. Although the absolute accuracy of the modeled 

temperatures cannot be assessed with the available data, comparisons among seagrass change 

categories within a given segment would be expected to provide relative information useful 

for assessing possible differences in exposure. Modeled temperature records of the 

individual polygons were further reduced to compute minima, maxima, and durations above 

or below given critical temperatures: 10 ̊, 15 ̊, 32 ̊ and 35 ̊C, drawn from Zieman and Zieman 

(1989). 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 9- 

Detailed Light Record 

A more detailed record of PAR was also prepared for individual polygons to accommodate 

the nonlinear attenuation of light with depth. The depth distributions of individual polygons 

were combined with linear interpolations between the polygonsí monthly mean attenuation 

coefficients, hourly tidal heights, and record of insolation. Measurements of underwater 

spectral irradiance between 0 and 2 m were used to compute a conversion factor between 

W/m2 (the insolation record) and PAR (L.K. Dixon, unpublished data). Factors so 

determined varied by less than a few percent between 0.3 and 2.0 m and so attenuation 

coefficients determined for PAR could be approximately applied to insolation. 

The time series of computed insolation at the bottom of water columns of various depths 

were linearly combined in the proportion of the depth distribution of the individual polygons. 

Data were further reduced to compute the fraction of immediately subsurface insolation 

available at depth, the number of days per month above selected compensation values, mean 

insolation during daylight hours, maximum insolation per month, number of days per month 

above reported saturation values, and the longest number of continuous days per month 

below selected compensation points (where rates of photosynthesis are balanced by 

respiration rates). Compensation points evaluated were 25, 50, 90, and 200 μE m-2 sec-1. 

These values were selected from studies utilizing entire seagrass shoots or in situ plants of 

either Thalassia testudinum or Halodule wrightii (Dawes and Tomasko, 1988; Fourquean and 

Zieman, 1991; Dunton and Tomasko, 1991). Compensation points were also increased to 

adjust for an assumed epiphytic attenuation of 43% as measured on seagrasses of both 

species during the growing season at a number of locations in Sarasota Bay (Dixon and 

Kirkpatrick, 1999). 

Results and Discussion: 

Change polygons 

A total of 860 polygons were selected for the 96-99 analysis; 789 were chosen for 99-01. 

Distribution by segment and category appear in Appendix A, together with mean elevations 

and approximate total areas. It should be repeated that the selected polygons are essentially 

all polygons for which a change axis appeared substantially larger that that of an adjacent 

shoreline change. Polygons were individually reviewed and represent a conservative subset 

of seagrass change. Unbalanced distribution of either area or numbers of polygons by 

change category is a result of overall polygon characteristics within a segment, rather than of 

the selection process. The polygons were selected to investigate probable causes of seagrass 

loss and gain and cannot be used to make statements about overall areal changes in seagrass 

within the Sarasota Bay system. Areas are provided in Appendix A solely to provide 

estimates of the general robustness of the change analysis. Polygons used are illustrated in 

Figures 4 through 7. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 10- 

1996-1999 Selected Seagrass Polygons

Gains

Unchanged

Losses

Figure 4. Selected polygons of seagrass change used for analyses, 1996-1999. Northern 

study area. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 11- 

1996-1999 Selected Seagrass Polygons

Gains

Unchanged

Losses

Figure 5. Selected polygons of seagrass change used for analyses, 1996-1999. Southern 

study area. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 12- 

1999-2001 Selected Seagrass Polygons

Gains

Unchanged

Losses

Figure 6. Selected polygons of seagrass change used for analyses, 1999-2001. 

Northern study area. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 13- 

1999-2001 Selected Seagrass Polygons

Gains

Unchanged

Losses

Figure 7. Selected polygons of seagrass change used for analyses, 1999-2001. 

Southern study area.
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page 14- 

Flight Times 

While two of the three periods of seagrass photography were flown in the winter when water 

clarity and cloud conditions were expected to be optimal, the 1996 photography was flown 

between April and October, 1997, due to logistical and weather complications. Approximate 

dates and regions of flights for the 1996 mapping are illustrated in Figure 8 and much was 

flown when seasonal biomass typically peaks (Dixon and Leverone, 1995; Figure 9). A 

change analysis of stable seagrass beds between a summer and a winter period (August 1997 

to December 1999) may easily have produced spurious changes, and the effect may vary by 

species of seagrass. Seasonally, the deep edges of Thalassia beds thin during winter but do 

not disappear entirely (Dixon and Leverone, 1995). Halodule beds, however, are reported to 

have ephemeral seasonal appearances (COT-BSG, 2003), and can be completely absent 

during the winter, only to reappear the following spring at a shoot density beyond that 

expected for vegetative expansion. The degree of contrast between seagrass blades and 

unvegetated bottom, the resolution of the photography, and water depth and clarity are other 

issues that will also affect whether seasonal bed thinning is visible between successive 

periods of photography. 

The two seagrass categories that are mapped, however, do not translate well to average 

biomass or shoot density values (typically measured on meter or sub-meter scales) except on 

very large spatial scales. The categories are operationally defined by percent of bare space 

visible in the photography and are more appropriately considered as a measure of the open 

area between sections of comparatively dense seagrass shoots. Within a given polygon of 

either patchy or continuous designation, the grassed areas can experience a wide range in 

shoot density or biomass without any change in classification (Figure 10). 

While the issue is complex, a seasonal decrease in biomass could prevent recognition of 

seagrass in the 1:24,000 scale photos during winter biomass and shoot density reductions. 

The most probable type of change so affected would be a change from patchy to bare. 

Change from continuous to patchy coverage would require the individual seagrass patches 

within a polygon to reduce and/or fragment so that more than 25% of unvegetated bottom 

becomes visible. If a seasonal change in biomass was detected during photo interpretation, 

then changes based on photography flown between April and August would be the most 

susceptible to artifact. Of the 1996 photography, the least likely seasonal artifacts were in 

the regions flown in October and January, or northern Sarasota Bay, portions of Palma Sola 

Bay, New Pass, and Roberts Bay. 

There were indeed large polygons of loss in Sarasota Bay between 1996 and 1999, in an area 

which was flown in August for the 1996 mapping. Reference to the original photos for some 

of the largest polygons of loss indicated that much of the change appeared to be large regions 

of very small patches in 1996 which were no longer visible in December 1999 (i.e., a 

conversion of patchy to bare). These losses were consistent with the postulated seasonal 

biomass changes. With the existing photography, however, it is not possible to further 

allocate losses between seasonal and interannual changes. The protocol of winter flights, 

adopted by SWFWMD for all subsequent and future flights, will remove this uncertainty 

from future seagrass change evaluations. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

Aproximate Flight Zones

04/199705/199708/199710/199701/2003

Figure 8. Approximate areas covered and dates of the 1996 aerial photography.
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 16- 

Figure 9. Seasonal fluctuation in Thalassia testudinum shoot density and biomass, as 

measured in Tampa Bay. 

 

 

 

 

 

 

 

 

Patchy 

 

Patchy 

 

Patchy 

 

 

 

 

 

 

 

 Continuous Continuous Continuous 

Figure 10. Examples of the variety of coverages under the patchy and continuous 

seagrass designations. Darker tones indicate higher biomass values and/or 

shoot density. White space is equivalent to bare bottom. 

JAN FEB APR JUN AUG OCT

Month

0

50

100

150

200

Shoot Density, (# m/ 2

)

FEB APR JUN AUG OCT DEC

Month

0

10

20

30

40

50

Above Ground Biomass, (g D

W

m/ 2

)
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 17- 

Polygon depths 

The elevations of seagrass polygons where no change had occurred (Category 9113 and 

9116) displayed significant differences (Kruskal-Wallis, p<0.05) by category for all segments 

(Figure 11), particularly for the central segments of Sarasota through Roberts Bays. Patchy 

polygons were generally deeper than the continuous beds in the central regions (with the 

exception of the shallow beds of Palma Sola Bay), and the pattern was present in the 

individual time periods as well. This was consistent with the observed seagrass growth 

patterns in the regions, in which deep edges of beds sometimes exhibit very heterogeneous 

edges. Fewer differences in depths between the stable continuous and stable patchy polygons 

were apparent for the shallower segments to the south and in Palma Sola Bay (Segments 2 

and 3). 

1 2 3 5 6 7 8 10 11 13 14 16

Segment

-3

-2

-1

0

Depth

m( , rel. M

L

L

W)

Patchy

Continuous

Category

Figure 11. Elevations of seagrass polygons of no change, by segment, for ë9113-Patchyí 

and ë9116-Continuousí. 

Examining depth distribution by general change category and segment indicated that 

polygons exhibiting any type of loss between 1996 and 1999 (Figure 12) were generally 

deeper in the northern Sarasota Bay segments. Segments 5, 6, 7, and 13 had significantly 

different depths by general change category (non-parametric Kruskal-Wallis, p<0.05), 

although median depths of loss polygons in Segment 13 were shallower than the other 

categories. Patterns were less obvious elsewhere and in the 99-01 polygons (Figure 13) and 

polygon elevations ranged widely within all categories. Further investigation of Segments 5, 

6, and 7 during 1996-1999 indicated that detailed categories of loss (Table 1) were not 

uniformly consistent with respect to depths and inferred reduction in available light with 

increasing depth (Figure 14). Even within a given segment, some categories of loss occurred 

at shallower depths than did some types of gains. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 18- 

1 2 3 5 6 7 8 10 11 13 14 16

Segment

-3

-2

-1

0

Depth

m( , rel. M

L

L

W)

Loss

Unch.

Gain

Change 96-99

Figure 12. Elevations of general categories of seagrass change, by segment, for 1996-

1999. 

1 2 3 5 6 7 8 10 11 13 14 16

Segment

-3

-2

-1

0

Depth

m( , rel. M

L

L

W)

Loss

Unch.

Gain

Change 99-01

Figure 13. Elevations of general categories of seagrass change, by segment, for the 1999-

2001. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 19- 

5 6 7

Segment

-3

-2

-1

0

Depth

m( , rel. M

L

L

W)

-3

-2

-1

9113

9116

1

2

3

Change 96-99

Figure 14. Elevations of specific change categories of seagrass for Segments 5, 6, and 7, 

for 1996-1999. 

Distributions of depths among polygon categories are more pertinent for seagrasss change 

analysis than are measures of central tendency, however. The tails of the distribution, the 

very deep and the very shallow, are where environmental constraints on seagrasses occur, 

either through reduced light at depth, or increased exposure, light, and/or thermal extremes 

(of both high and low temperature). Non-parametric Kolmogorov-Smirnov tests were used 

to compare the cumulative distributions between pairs of change categories. General change 

categories (loss, unchanged, and gain) were first evaluated by time period and segment, 

followed by the evaluation of specific change categories (-3, -2, -1, 9113, 9116, 1, 2, and 3) if 

general change categories proved significant. Table 2 summarizes the results as to whether 

significant differences in depth distributions were present. Table 2 also provides qualitative 

information as to whether exposure effects were likely to differentiate between categories. 

Figure 15 illustrates for Segment 7 (96-99) that loss polygons were significantly different 

and generally deeper than other categories. (Data are illustrated against a standard normal 

distribution but are unstandardized to retain the magnitude of differences between change 

categories.) Light limitation probably plays a large role for many of the seagrass loss 

polygons in this segment. Unchanged polygons are among the shallowest in this segment 

and so impacts from exposure or recovery from exposure are unlikely in Segment 7. In 

Figure 16, on the other hand, the distribution of Segment 2 polygons at depth is comparable 

between change categories and there are no significant differences in depth distribution. The 

loss polygons, however, appear to have a few extremely shallow examples (between -0.2 and 

0.0m) and exposure effects could be important in this segment and time period. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 20- 

Table 2. Distribution of polygon depths by general change category and evaluation of 

potential for low light or exposure effects based on relative depth distribution 

Time 

Period Segment 

Sig. Diff. in 

Polygon Depth, 

(K-S, p<=0.05) 

Possible 

Exposure 

Effects Comments 

 

96-99 1 Only a few deep 'L' polygons 

96-99 2 Y A number of 'L' were very shallow 

96-99 3 'L' generally deeper 

96-99 5 Y 'L' generally deeper 

96-99 6 Y 'L' generally deeper 

96-99 7 Y 'L' generally deeper 

96-99 8 

96-99 10 

96-99 11 

96-99 13 Y Y Some 'L' were very shallow 

96-99 14 Y Some 'L' were very shallow 

96-99 16 Some 'L' were very deep 

 

99-01 1 Y 'L' and 'G' were generally shallower than 'U' 

99-01 2 

99-01 3 Y Only one polygon of 'L' 

99-01 5 Y 'L' generally shallower 

99-01 6 'U' and 'G' categories in very shallow water 

99-01 7 

99-01 8 Y 'L' generally shallower 

99-01 10 

99-01 11 Y 'L' polygons either very deep or very shallow 

99-01 13 

99-01 14 'L' polygons generally deeper 

99-01 16 Y 'L' deeper overall than other categories 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 21- 

-3 -2 -1 0

Depth (m, rel. MLLW)

-3

-2

-1

0

1

2

3

E

x

p

e

cte

d

Std. N

o

mr al Distrib

utio

n

Loss

Unch.

Gain

Category

Figure 15. Distribution of polygon depths by general change category for Segment 7, 

1996-1999. 

-1.5 -1.0 -0.5 0.0

Depth (m, rel. MLLW)

-3

-2

-1

0

1

2

3

E

x

p

e

cte

d

Std. N

orm

al Distrib

utio

n

Loss

Unch.

Gain

Category

Figure 16. Distribution of polygon depths by general change category for Segment 2, 

1996-1999. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 22- 

Segment Water Quality 

The entire Sarasota Bay study area exhibited wide ranges of the water quality parameters 

investigated. Light attenuation coefficients, turbidity, color, chlorophyll, total nitrogen, and 

salinity were all significantly different both between periods (96-99 and 99-01; KruskalWallis, p<=0.05) and between segments. The distributions of the mean monthly water 

quality parameters by period and by segment appear in Appendix B with segment means 

mapped by time period in Appendix C. The combination of multiple gradients across the 

study area makes possible a wide variety of controlling influences on seagrasses in the 

region. While water quality gradients across the entire study area were pronounced, the 

gradients within any one segment were much less noticeable, due in part to the 

morphological segment boundaries employed. 

The largest three polygons of each of the three general change categories (Loss, Unchanged, 

Gain) within each segment were also selected. The time series of the polygon-specific water 

quality values appear in Appendix D and illustrate that water quality was highly variable over 

the study period. Most importantly, Appendix D visually indicates that there was no single 

ëcontrollingí water quality parameter among those investigated that was consistently 

associated with the general seagrass change categories. 

As turbidity, chlorophyll, and color are components of light attenuation, analytical efforts 

centered on total nitrogen (as a possible surrogate for ephiphytic growth), salinity, and 

remaining light at depth. When analyzed by time period and by segment, there were few 

significant differences between general change categories for total nitrogen distributions. In 

96-99 data, loss polygons in Segment 7 were significantly higher in nitrogen than either 

unchanged or gain polygons. Differences were on the order of <0.1 mg/L of total N. In 

Segment 8, however, loss and unchanged polygons both experienced significantly lower total 

nitrogen concentrations. During the 99-01 period, significant differences in nitrogen between 

change categories were limited to Segments 1 and 8, with loss polygons lower in total 

nitrogen in Segment 1 than in other categories and nitrogen higher in the loss polygons of 

Segment 8 than for other changes. In general, the gradient across specific categories of 

change did not correspond with polygon nitrogen concentrations in any consistent way. 

While a relationship has been previously observed between nitrogen loading to the region 

and seagrass productivity (Tomasko and Hall, 1996), water column total nitrogen was 

relatively uniform across the various seagrass change categories within a given segment. 

More detailed investigation by specific change category (-3, -2, etc.) was often contradictory, 

with some gain and loss categories exhibiting similar total nitrogen concentrations, or some 

loss categories exhibiting relatively high nitrogen and other loss categories appearing much 

lower. It was anticipated that total nitrogen might serve as a useful surrogate for epiphytic 

attenuation on seagrass blades, an effect which further reduces available light. There proved 

to be low gradient of nitrogen concentration within individual segments, however, reducing 

the usefulness of nitrogen to evaluate seagrass change within a segment. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 23- 

Nitrogen concentrations between segments varied widely (Figure 17 ), however, and a large 

body of literature leads us to expect ecological effects from differing concentrations. The 

water quality values of the polygons of no change (9113, 9116) were averaged by time 

period, by segment and by category. A simple but significant regression was developed in 

which the depth of the polygons of no change were significantly predicted by attenuation 

coefficient and total nitrogen alone (n=48, r2=0.378, p<0.0001). Additionally, an important 

component of attenuation is chlorophyll, itself a function of nitrogen. It is evident that 

nitrogen plays an important role in regulating the maximum depths at which seagrasses can 

exist in the Sarasota Bay system, but under current nitrogen loadings, it does not appear to be 

the most important variable within a segment for predicting seagrass change. 

Figure 17. Distribution of total nitrogen by segment for 1999-2001. 

Salinity values were similarly evaluated. High salinities were not expected to be 

problematical for seagrasses in the Sarasota Bay system based on reported tolerances, but 

excursions of freshwater are linked to leaf loss (Zieman and Zieman, 1989). In 96-99, 

Segment 8 loss categories experienced significantly different salinities than either unchanged 

or gain categories (Figure 18) with differences most apparent in the low salinity 

distributions. The lowest salinities were between 7-13 PSU for all categories. The lowest 

salinities of the loss category polygons were approximately 2-5 PSU lower than non-loss 

categories. For Segment 10 on the other hand, the salinities of loss polygons were 

significantly higher. In 99-01 data, salinity of loss polygons was depressed overall in 

Segment 8. No other segment experienced significant differences by loss category, although 

distributions often differed by ~1 PSU in the low salinity ëtailsí. Other than Segment 8 in 96-

99, observed differences, based on spatially interpolated data developed from monthly 

samplings, did not appear substantive enough to account for losses. 

0.0 0.5 1.0 1.5 2.0 2.5

Total Nitrogen (mg/L)

-5

-4

-3

-2

-1

0

1

2

3

4

5

E

x

pected

Std. N

o

mr al Distrib

utio

n

16

14

13

11

10

8

7

6

5

3

2

1

99-01
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 24- 

0 10 20 30 40

Salinity (PSU)

-4

-3

-2

-1

0

1

2

3

4

E

x

pected

Std. N

o

mr al Distrib

utio

n

Loss

Unch.

Gain

Category

Figure 18. Distribution of salinity by general change category for Segment 8, 1996-1999. 

The salinity distribution of polygons of no change (9113 and 9116) in both 96-99 and 99-01 

appear in Figure 19. Segments 8, 13, 14, and 16 routinely experience salinity depressions 

below 15 PSU with Segment 13 as low as 7-8 PSU. The remaining segments have minima 

between 18 and 28 PSU. The low values experienced by polygons of no change would 

appear to indicate that the few salinity differences observed by loss category, while 

statistically significant, were not environmentally relevant. 

0 10 20 30 40 50

Salinity (PSU)

-5

-4

-3

-2

-1

0

1

2

3

4

5

E

x

pected

Std. N

o

mr al Distrib

utio

n

16

14

13

11

10

8

7

6

5

3

2

1

Unchanged

Figure 19. Distribution of salinity by segment for unchanged polygons (9113 and 9116) 

during both 1996-1999 and 1999-2001. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 25- 

Available light 

Light levels at the seagrass bed are a function of both water column depths and attenuation 

coefficients (which are in turn a function of chlorophyll, turbidity, and water color). To 

integrate depth and water column characteristics, the fraction of immediately subsurface light 

still available to the seagrasses was calculated from the mean monthly attenuation value of 

each polygon together with mean water column depths (bed elevation plus the additional 

water column between MLLW and mean tide level). This approach did not account for 

attenuation by epiphytes. With the exception of Segment 13 during 1999-2001, all segments 

displayed significant differences (Kruskal-Wallis, p<=0.05) in available light fraction 

between general change categories. Most (20 of the 24 segment-period combinations) were 

highly significant (p<=0.001). Counterintuitively, however, in nine of the 24 combinations, 

median values of available light for the loss polygons were greater than the median light 

received by polygons of no change. When investigated by exact change category, the pattern 

was as inconsistent as it appeared for total nitrogen. 

Distributions of light fraction, however, were more useful. Significant differences 

(Kolmogorov-Smirnov, p<=0.05) appeared between general change categories for all but one 

of the segment-time period combinations (Table 3). Many of the segment comparisons, 

particularly in 96-99, displayed the lowest light distributions for the general loss category. 

The results in Segment 7 (Figure 20) were somewhat expected based on the depth 

distribution of polygons by change category within the segment. Even in segments where 

depth distributions were comparable across change categories (Segment 10, 99-01, Figure 

21), light distributions were significantly lower for the general loss category. Results from 

Segments 1-8 in the 99-01 time period should be viewed with caution as 2001 data on light 

attenuation were not available for these segments and as attenuation coefficients in 2001 

from other segments were elevated over 2000 data. Qualitative and quantitative distributions 

of light fraction by change category were almost identical for the data truncated to the 

growing season (April-October). 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Light Fraction at Depth

-4

-3

-2

-1

0

1

2

3

4

E

x

pected Std. No mr al Distrib

ution

Loss

Unch.

Gain

Category, 96-99

Figure 20. Distribution of light fraction at depth by general change category for Segment 

7, 1996-1999. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 26- 

Table 3. Distribution of fraction of light at the bottom of the water column by general 

change category and evaluation of potential for low light based on depth 

distributions by change category 

Time 

Period Segment 

Sig. Diff. in 

Light Frac., 

(K-S, p<=0.05)

Possible Low 

Light Effects 

Comments 

 

96-99 1 Y 'L','U' comparable light, lower than 'G' 

96-99 2 Y 'L' higher at high light 

96-99 3 Y Y 'L' lowest light overall 

96-99 5 Y Y 'L' lowest light overall 

96-99 6 Y Y 'L' lowest light overall 

96-99 7 Y Y 'L' lowest light overall 

96-99 8 Y Y ëLí lowest light overall, medium at high light

96-99 10 Y 'L' highest light overall 

96-99 11 Y Y 'L' lowest light overall 

96-99 13 Y 'G' lowest light overall, 'L' lower at low light 

96-99 14 Y 'L' highest light overall 

96-99 16 Y 'L', 'G' comparable light and lower than 'U' 

 

99-01* 1 Y 'L' highest light overall 

99-01* 2 Y Y 'L' lowest light overall 

99-01* 3 Y 'U' lowest light overall, few 'L' 

99-01* 5 Y 'L' highest light overall 

99-01* 6 Y 'L' higher at low light, lower at high light 

99-01* 7 Y all very comparable 

99-01* 8 Y 'L' higher light overall 

99-01 10 Y 'L lower light overall, esp. at high light 

99-01 11 Y 'L' lower at low end, higher at high light 

99-01 13 all very comparable 

99-01 14 Y all very comparable 

99-01 16 Y Y 'L' lowest light overall 

* - Data from 2001 unavailable 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 27- 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Light Fraction at Depth

-4

-3

-2

-1

0

1

2

3

4

E

x

p

e

cte

d

Std. N

orm

al Distrib

utio

n

Loss

Unch.

Gain

Category, 99-01

Figure 21. Distribution of light fraction at depth by general change category for Segment 

10, 1999-2001. 

Even for segments with complete data sets and large separations in both light and depth 

distributions by general change category, segregation of the light distributions by specific 

change category again produced conflicting results. Figure 22 illustrates Segment 8, 96-99, 

for the specific change categories. Depth distributions appear in Figure 23, and it was 

apparent that a single shallow polygon produced the very high light levels of the -3 loss 

category. With little variation in attenuation coefficients within segments, the fraction of 

light available was largely a function of the depth of the water column within a given 

segment. The seagrass in the shallow polygon was more likely lost as a result of exposure 

rather than low light levels. This illustrates the complexity of assigning probable cause to 

changes in seagrass coverage. 

The distribution of light fraction by specific change category was examined in the more 

complete data record of 1996-1999 (e.g., Figure 22). In all segments with the exception of 

Segments 10 and 14, the change category of -2 (patchy to unvegetated) experienced lower 

light levels in both the center and in the low light ëtailí of the distribution. Means of light 

fraction by specific categories and by segment for 96-99 also illustrated this (Figure 24). 

The other loss categories, in aggregate, generally experienced as much or higher light levels 

than did unchanged or gain polygons. In fact, the loss category of -3 (continuous to 

unvegetated) often experienced the highest mean light levels. Segment and category means 

of polygon elevation (Figure 25) also illustrated that the -3 and -1 loss categories were 

generally shallower than other polygons and indicated that there was more than one factor 

responsible for changes in seagrass coverage in the Sarasota Bay system. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 28- 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Light Fraction at Depth

-4

-3

-2

-1

0

1

2

3

4

E

x

pected

Std. N

o

mr al Distrib

utio

n

-3

-2

-1

9113

9116

1

2

3

Category

Figure 22. Distribution of light fraction at depth by specific change category for Segment 

8, 1996-1999. 

-3 -2 -1 0

Depth (m, rel. MLLW)

-3

-2

-1

0

1

2

3

E

x

pected

Std. N

o

mr al Distrib

utio

n

-3

-2

-1

9113

9116

1

2

3

Category

Figure 23. Distribution of polygon depths by specific change category for Segment 8, 

1996-1999. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 29- 

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Lig

ht Fra

ctio

n

at D

e

pth

-3

-2

-1

9113

9116

1

2

3

Category

Figure 24. Mean light fraction at depth for 1996-1999, by segment and specific change 

category. 

1 2 3 5 6 7 8 10 11 13 14 16

Segment

-2.0

-1.5

-1.0

-0.5

0.0

D

e

pth

m( , rel. M

L

L

W)

-3

-2

-1

9113

9116

1

2

3

Category

Figure 25. Mean polygon elevation for 1996-1999 by segment and specific change 

category. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 30- 

Further analyses of light levels with respect to seagrass change examined the duration of low 

light events as interpolated from available data. Selected seagrass compensation points were 

evaluated against a modeled record of hourly light records for individual polygons. Modeled 

water column elevations, the insolation record, and linear interpolation of attenuation 

coefficients between monthly estimates were used to generate the record of available light. 

A number of assumptions were implicitly included and discussed in the methods section, and 

while comparisons between segments may be subject to errors due to known approximations, 

inferences within segments but between change categories should be robust. 

Analyses concentrated on the 96-99 period due to the completeness of the water quality 

record. Parameters examined included monthly values of total duration below selected 

compensation points, as well as the longest period of time where light levels were 

continuously below the compensation point. Larger values of the two parameters were 

indicative of lower ambient light levels. Using 25 μE m-2sec-1 as a compensation point and 

within a given segment, the polygons of general loss categories had either similar or longer 

durations below the compensation point than did unchanged or gain polygons. Differences 

between change categories were more prevalent in the center of the distribution and at the 

low light, longer duration tails rather than in the short duration region. All segments 

exhibited significant differences by general change category, with differences consistent with 

light limitation in Segments 3, 5, 6, 7, 11, and 16 (Figure 26). Segments 5 and 7 in 

particular exhibited a number of months where ambient light in a loss polygon did not exceed 

the estimated compensation point for the entire month. 

If higher compensation points were used, changes in the distribution of the above parameters 

for a given segment or change category altered in predictable ways (Figure 27); duration 

below the compensation point and the continuous time below the compensation point both 

increased. Separation between general change categories was greatest for lower 

compensation points, however. The use of higher compensation points also increased the 

number of months where polygons of all change categories did not exceed the compensation 

point, and so their use for a species commonly accepted to be depth and light-limited appears 

less reasonable. Without further knowledge as to the species distribution within the Sarasota 

Bay system and the length of time that a given species can survive when photosynthesis does 

not exceed respiration, however, the change analysis cannot differentiate between appropriate 

compensation points except in a qualitative sense. 

Returning to the 25 μE m-2sec-1 compensation point, and examining the continuous number 

of days in a month when light levels did not exceed the compensation point, an interesting 

pattern appears between segments. In Segments 1, 3, 5, 6, 7, and 8, the longest continuous 

durations appeared between July and December, and were predominantly in August through 

October of 1999. Many were longer than 10 days. The remaining segments experienced 

much lower continuous durations with the larger ones during the winter months, October 

through February. Increased periods of light below the compensation point during the 

warmer growing season would be expected to have a more deleterious impact than low light 

periods during cooler periods. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 31- 

10 15 20 25 30 35

Total Duration < Icomp (days/month

-4

-3

-2

-1

0

1

2

3

4

E

x

p

ecte

d

Std. N

o

mr al Distrib

utio

n

Loss

Unch.

Gain

Category, 96-99

0 10 20 30 40

Continuous Duration < Icomp (days/month)

-4

-3

-2

-1

0

1

2

3

4

E

x

pected

Std. N

o

mr al Distrib

utio

n

Loss

Unch.

Gain

Category, 96-99

Figure 26. Light duration parameters for Segment 5 using compensation irradiance of 25 

μE m2

 sec-1
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 32- 

15 20 25 30 35

Total Duration < Icomp (days/month)

-4

-3

-2

-1

0

1

2

3

4

E

x

pected

Std. N

o

mr al Distrib

utio

n

Loss

Unch.

Gain

Category, 96-99

0 10 20 30 40

Continuous Duration < Icomp (days/month)

-4

-3

-2

-1

0

1

2

3

4

E

x

pected

Std. N

o

mr al Distrib

utio

n

Loss

Unch.

Gain

Category, 96-99

Figure 27. Light duration parameters for Segment 5 using compensation irradiance of 

200 μE m2

 sec-1
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 33- 

The analysis of the modeled light record by specific change categories displayed similar 

patterns to the other parameters. While some segments exhibited expected patterns of 

extended low light duration with losses, others did not, indicating that some losses of 

seagrass can be attributed to causes other than low light levels. Due to the low within 

segment variation in attenuation coefficients and the dependence of light fractions and 

durations on water column depth, detailed light simulations have very similar distributions to 

that observed for polygon depths. 

 

Temperature 

The modeled temperature of a single polygon (Figure 28) illustrates that the winters of 1995-

6, 1996-7, and 2000-2001 contained some extreme cold days, but that the winter of 1997-8 

experienced an extended cold season. The summer of 1995 and 2000 were both warm for 

extended periods of time. Consistent with the cold winter (and presumed cold fronts) of 

1995-6, there were a number modeled low tide events during this season (Figure 29). 

As expected, the minima of modeled temperatures were lower in the shallower polygons, and 

as such, the temperature distributions were expected to appear similar to depth distributions. 

Durations below selected set points (10 ̊C and 15 ̊C) were both evaluated. While some 

segments (Segments 8, 11, and 13) experienced longer durations, durations for all categories 

were seldom predicted to be longer than ~10 hours, differences between change categories 

were slight (<1 hour) and none were statistically significant. In some segments, loss 

categories of -1 and -3 experienced generally longer durations of temperatures below set 

points than did loss category -2. This result is again a product of the elevation and assumed 

water column depth above a polygon. In most instances, however, distribution of 

temperatures for gain or unchanged categories were very similar to that modeled for loss 

polygons. 

High temperatures were also evaluated. Duration above high temperature set points (32 ̊C, 

35 ̊C) were surprising in that the longest average durations were experienced by unchanging 

or gain polygons. In some segments, loss polygons experienced among the highest 

temperatures, while in other segments, gain or unchanged polygons experienced as high or 

higher temperatures. Modeled thermal maxima and/or minima did not appear to be a 

controlling factor of seagrass change. 

The model of thermal extremes for seagrasses does not incorporate actual exposure and 

dessication of grasses since it was not possible to verify the water column depths and actual 

tidal regimes above polygons under this project. Grasses are observed to be exposed at times 

in Sarasota Bay and so the probability for losses in shallow polygons due to exposure (see 

Figure 25) remains high but cannot be quantified at this time. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 34- 

1994 1996 1998 2000 2002

Year

5

15

25

35

M

o

deled

P

oly

g

o

n

Temperature D( eg

C)

Figure 28. Time series of modeled temperatures for a single polygon. 

1994 1996 1998 2000 2002

Year

0.5

1.0

1.5

2.0

2.5

M

o

deled

P

oly

g

o

n

Depth

m( )

Figure 29. Time series of modeled water column depths for a single polygon. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 35- 

Summary 

A subset of seagrass change polygons was selected for the Sarasota Bay area and analyzed 

for the 1996-1999 and 1999-2001 periods. Polygons with changes similar to nearby 

shoreline changes were not included so as not to include spurious change due to 

improvements in locational accuracy between different periods of photo-interpretation. As 

not all polygons were included, no attempt was made to weight the remaining polygons for 

differences in areas. Analyses focused on the 1996-1999 time period due to the 

completeness of the water quality record available. 

Seasonal differences in biomass could account for some of the losses observed between 1996 

and 1999, as the 1996 photography was flown between April and October, in comparison to 

December-January flights for the remaining periods. The large areas of loss in central 

Sarasota Bay were predominantly due to the disappearance of numerous small patches at 

depth, and were consistent with seasonal patterns of Halodule growth observed nearby. Not 

all of the loss may have been seasonal however, as some gains were noted between 1999 and 

2001 in the same regions. 

Looking at unchanged seagrass polygons, patchy seagrass predominated at depth in central 

Sarasota and Roberts Bays. General loss categories were also predominantly deeper in 

Sarasota Bay (Segments 5, 6, 7, and 8). The distribution of polygon depths was more useful 

than mean or median values for interpreting losses and gains, however. Depth distributions 

were significantly different by general change category in Segments 5, 6, 7, and 13, but 

losses were deeper in Segment 5, 6, and 7, and shallower in Segment 13. Segments 2, 6, 8, 

13, and 14 had been identified as potentially subject to exposure losses due the number of 

shallow polygons in those segments. Using specific change categories (patchy to bare, etc.), 

loss categories did not exhibit a consistent depth gradient in any segment. A number of 

segments exhibited losses of patchy to bare (-2) at depth, while losses of continuous to 

patchy (-1) and continuous to bare (-3) occurred at very shallow depths. Some categories of 

gain received less light than did some loss categories. It was clear that reduced light at depth 

was not the only cause of seagrass loss. 

Monthly water quality values (total nitrogen, salinity, attenuation coefficients and other 

attenuators) were spatially interpolated and means computed for all segments and polygons. 

Gradients within a segment were generally not high, and so there was little variation in water 

quality either among all polygons or between any change categories for polygons within a 

given segment. The few significant differences observed between change categories in 

salinity or nitrogen within a segment did not appear to be environmentally relevant when 

viewed in respect to distributions experienced by polygons of no change. Variations in water 

column nitrogen, while not associated with change categories within a segment, was 

significantly corrected (together with attention is efficient) with the depth of stable seagrass 

beds for the entire Sarasota Bay system. As a result, total nitrogen should continue to be 

considered in any seagrass restoration plan. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 36- 

The light fraction available at depth was computed for all polygons from monthly attenuation 

coefficients and estimated water column depths. As gradients in attenuation were low across 

a given segment, distributions of light fraction were generally very similar to that expected 

based on polygon depth. Significant differences existed in all polygons and light fractions 

were lower in the general loss category for Segments 3, 5, 6, 7, 8, 11, and 13. Specific 

categories of change were as varied for light fraction as they were for depths. 

Using a number of assumptions, detailed estimates of time series of light at depth and 

polygon temperature were prepared and compared to literature values where deleterious 

effects are thought to occur. Both estimates depended largely on the water column depths of 

individual polygons and the assumption that the difference between MLLW and mean tide 

level (MTL) was uniform across the bay with respect to the tidal reference station. It is 

expected that any differences between MTL and MLLW were smaller within segment than 

between segments and so comparisons between change categories within a segment were 

correspondingly more robust than comparisons between segments. Differences in 

distribution of duration of light below selected compensation points and between change 

categories again reduced to patterns similar to that expected from the depth distributions. 

The gradient of light available did not uniformly correspond with a progression of specific 

loss and gain categories. There were few differences in the distribution of thermal extremes 

by change category, either general or specific. Actual exposure and dessication, which could 

not be evaluated due to uncertainties in MTL across segments, remain a likely cause of losses 

in the shallowest polygons. 

Low light was associated with seagrass losses, particularly in 1996-1999 and in north and 

central Sarasota Bay. An incomplete record of water quality hampered comparisons in 1999-

2001, but low light was again associated with general losses in some segments. Selected 

categories of loss were associated with very shallow polygons in some segments and may be 

attributed to exposure. Depressed salinities were present in Segments 8, 13, 14, and 16 but 

values were comparable to areas with no change. Salinity effects alone did not appear 

responsible for seagrass losses or gains. Nitrogen did not vary among the change categories 

within a given segment but was significantly and inversely related to the depths of stable 

polygons of seagrass. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 37- 

References: 

City of Tampa - Bay Studies Group. 2003. Seagrass and Caulerpa monitoring in Hillsborough Bay 

14th Annual Report. City of Tamp Department of Sanitary Sewers, Tampa FL. 

Dawes, C.J. and D.A. Tomasko. 1988. Depth distribution of Thalassia testudinum in two meadows 

on the east coast of Florida USA: A difference in effect of light availability. Marine Ecology 

Progress Series 9: 123-130.

Dixon, L.K. and G.J. Kirkpatrick. 1999. Causes of light attenuation with respect to 

seagrasses in Upper and Lower Charlotte Harbor. Mote Marine Laboratory Technical Report 

No. 650. Sarasota, FL. 

Dixon, L.K. and J.R. Leverone. 1995. Light requirements of Thalassia testudinum in Tampa 

Bay, Florida. Mote Marine Laboratory Technical Report No. 425. Sarasota, FL. 

Dunton, K.H. and D.A. Tomasko. 1991. Seasonal variations in the photosynthetic performance of 

Halodule wrightii measured in situ in Laguna Madre, Texas. In: The Light Requirements of 

Seagrasses: Proceedings of a Workshop to Examine the Capability of Water Quality Criteria, 

Standards and Monitoring Programs to Protect Seagrasses, Kenworthy, W.J. and D.E. Haunert (eds.), 

NOAA Technical Memorandum NMFS-SEFC-287.

Estevez, E.D., and Palmer, C.L.P., 1990. A segmentation system for the Sarasota Bay 

Project National Estuary Program. Mote Marine Laboratory Technical Report No. 161. 

Sarasota, FL. 

Fourqurean, J.W. and J.C. Zieman. 1991b. Photosynthesis, respiration and whole plant carbon 

budget of the seagrass Thalassia testudinum. Marine Ecology Progress Series 69: 161-170.

Johansson, J.O.R. and H.S. Greening. 1999. Seagrass restoration in Tampa Bay: A resourcebased approach to estuarine management. In. Seagrasses: Monitoring, Ecology, Physiology, 

and Management. S.A. Bortone, Ed. CRC Press. Boca Raton, FL. 

Kirk, J.T.O. 1994. Light and photosynthesis in aquatic ecosystems. Second Edition. 

Cambridge University Press. Cambridge, Great Britain. 

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 Florida coastal waters. 

Southwest Florida Water Management District. Tampa, FL. 

Nation Oceanic and Atmospheric Administration. 1994. Tide Tables 1995: High and low 

water predictions ñ East Coast of North and South America including Greenland. 

Southwest Florida Water Management District. 2001. Metadata for Data Layer SG99. 

SWFWMD. Brooksville, FL. 

Stewart, R.H. 2002. Introduction to physical oceanography. Texas A&M University. 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page 38- 

Tomasko, D. A., 2002. Status and trends of seagrass coverage in Tampa Bay, with reference 

to other Southwest Florida estuaries. In: Seagrass Management: It's not just nutrients! 

Greening, H.S., editor. Tampa Bay Estuary Program, St. Petersburg, FL. 

Tomasko, D.A., 2003. Presentation: 2002 Seagrass mapping efforts in 

Southwest Florida. Southwest Florida Water Management District, Sarasota, 

FL.,01/14/2003. 

Tomasko, D.A., C.J. Dawes and M.O. Hall. 1996. The effects of anthropogenic nutrient 

enrichment on turtle grass (Thalassia testudinum) in Sarasota Bay, Florida. Estuaries. 19: 

448-456. 

Tomasko, D.A. and Hall, M.O., 1999. Productivity and biomass of the seagrass Thalassia 

testudinum along a gradient of freshwater influence in Charlotte Harbor, Florida. Estuaries, 

No.3A, pp 592-602. 

Zieman, J.C. and R.T. Zieman. 1989. The ecology of the seagrass meadows of the west 

coast of Florida: A community profile. U.S. Fish and Wildlife Service Biological Report 

85(7.25) September, 1989. Washington, D.C. 
Appendix A 

Distribution of polygon change categories by time period and by segment.
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page A-1-

Period Segment Change 

Category 

Number of 

Polygons 

Mean Elevation 

(m, MLLW) Area (m2

) 

96-99 1 -3 3 -0.8 12,600 

96-99 1 -2 6 -1.3 24,300 

96-99 1 -1 17 -0.7 135,000 

96-99 1 9113 6 -1.2 936,900 

96-99 1 9116 9 -0.7 1,032,300 

96-99 1 1 1 -0.8 6,300 

96-99 1 2 19 -0.7 711,000 

96-99 2 -3 3 -0.1 4,500 

96-99 2 -2 17 -0.4 75,600 

96-99 2 -1 9 -0.2 84,600 

96-99 2 9113 10 -0.3 232,200 

96-99 2 9116 9 -0.4 1,197,900 

96-99 2 1 2 -1.0 2,700 

96-99 2 2 23 -0.3 1,145,700 

96-99 2 3 3 -0.7 66,600 

96-99 3 -3 5 -0.4 30,600 

96-99 3 -2 19 -0.7 163,800 

96-99 3 -1 4 -0.5 24,300 

96-99 3 9113 7 -0.3 183,600 

96-99 3 9116 5 -0.5 216,900 

96-99 3 2 14 -0.4 174,600 

96-99 3 3 3 -0.9 2,700 

96-99 5 -3 3 -0.9 6,300 

96-99 5 -2 33 -1.3 403,200 

96-99 5 -1 11 -0.8 45,000 

96-99 5 9113 11 -1.2 431,100 

96-99 5 9116 5 -0.6 2,003,400 

96-99 5 1 1 -1.2 1,800 

96-99 5 2 20 -0.8 653,400 

96-99 5 3 1 -1.4 900 

96-99 6 -3 2 -0.1 8,100 

96-99 6 -2 27 -1.0 342,000 

96-99 6 -1 10 -0.1 183,600 

96-99 6 9113 19 -0.4 692,100 

96-99 6 9116 7 -0.2 790,200 

96-99 6 2 19 -0.5 1,901,700 

96-99 6 3 3 -0.4 34,200 

96-99 7 -3 5 -1.1 54,900 

96-99 7 -2 20 -1.6 1,427,400 

96-99 7 -1 20 -0.8 120,600 

96-99 7 9113 20 -0.8 1,285,200 

96-99 7 9116 24 -0.5 981,000 

96-99 7 2 18 -0.6 1,168,200 

96-99 8 -3 1 -0.1 1,800 

96-99 8 -2 6 -1.3 547,200 

96-99 8 -1 1 -0.2 2,700 

96-99 8 9113 8 -0.8 205,200 

96-99 8 9116 10 -0.4 290,700 

96-99 8 1 4 -1.1 10,800 

96-99 8 2 6 -0.4 576,900 

96-99 8 3 1 -1.2 2,700 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page A-2-

Period Segment 

Change 

Category 

Number of 

Polygons 

Mean Elevation 

(m, MLLW) Area (m2) 

96-99 10 -3 5 -0.9 74,700

96-99 10 -2 10 -0.8 163,800

96-99 10 -1 21 -0.6 126,900

96-99 10 9113 9 -1.0 318,600

96-99 10 9116 9 -0.8 1,566,900

96-99 10 1 2 -1.6 43,200

96-99 10 2 22 -0.8 245,700

96-99 10 3 1 -1.2 6,300

96-99 11 -3 1 -0.4 6,300

96-99 11 -2 4 -1.3 45,000

96-99 11 -1 4 -1.0 20,700

96-99 11 9113 6 -0.9 603,000

96-99 11 9116 1 -0.7 4,500

96-99 11 1 4 -1.2 34,200

96-99 11 2 10 -0.7 122,400

96-99 11 3 3 -1.3 13,500

96-99 12 2 1 0.0 18,900

96-99 13 -3 3 -0.5 10,800

96-99 13 -2 10 -0.8 90,900

96-99 13 -1 6 -0.4 63,000

96-99 13 9113 9 -0.6 476,100

96-99 13 9116 7 -0.5 215,100

96-99 13 1 7 -0.9 52,200

96-99 13 2 9 -0.6 98,100

96-99 13 3 3 -0.9 17,100

96-99 14 -3 3 -0.5 7,200

96-99 14 -2 12 -0.6 73,800

96-99 14 -1 6 -0.4 34,200

96-99 14 9113 16 -0.6 330,300

96-99 14 9116 15 -0.6 482,400

96-99 14 1 15 -0.7 115,200

96-99 14 2 22 -0.6 475,200

96-99 14 3 10 -0.7 157,500

96-99 16 -3 5 -0.6 12,600

96-99 16 -2 11 -0.7 66,600

96-99 16 -1 8 -0.6 36,900

96-99 16 9113 12 -0.7 299,700

96-99 16 9116 10 -0.4 237,600

96-99 16 1 6 -1.0 47,700

96-99 16 2 21 -0.5 389,700

96-99 16 3 11 -0.8 63,000

99-01 1 -3 1 -0.7 1,800

99-01 1 -2 5 -0.8 23,400

99-01 1 -1 1 -0.4 7,200

99-01 1 9113 12 -1.1 155,700

99-01 1 9116 19 -0.9 2,877,300

99-01 1 1 2 -1.1 9,900

99-01 1 2 52 -0.7 594,900

99-01 2 -2 3 -0.6 14,400

99-01 2 -1 2 -0.2 18,000

99-01 2 9113 9 -0.3 80,100

99-01 2 9116 15 -0.3 3,307,500

99-01 2 1 2 -0.2 45,900

99-01 2 2 36 -0.2 596,700

99-01 2 3 2 -0.3 25,200
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page A-3-

Period Segment 

Change 

Category 

Number of 

Polygons 

Mean Elevation 

(m, MLLW) Area (m2) 

99-01 3 -1 1 -0.5 3,600 

99-01 3 9113 10 -0.5 193,500 

99-01 3 9116 15 -0.6 667,800 

99-01 3 1 1 -0.5 12,600 

99-01 3 2 11 -0.4 74,700 

99-01 3 3 2 -0.3 42,300 

99-01 5 -3 2 -0.5 10,800 

99-01 5 -1 10 -0.7 78,300 

99-01 5 9113 26 -1.0 351,000 

99-01 5 9116 8 -0.8 971,100 

99-01 5 1 1 -1.2 5,400 

99-01 5 2 15 -0.8 248,400 

99-01 5 3 2 -1.2 9,000 

99-01 6 -2 4 -0.6 17,100 

99-01 6 -1 4 -0.5 37,800 

99-01 6 9113 10 -0.8 169,200 

99-01 6 9116 10 -0.7 3,035,700 

99-01 6 1 1 -0.2 7,200 

99-01 6 2 17 -0.5 207,000 

99-01 6 3 2 -0.4 22,500 

99-01 7 -3 1 -0.5 14,400 

99-01 7 -2 9 -1.1 78,300 

99-01 7 -1 3 -0.7 20,700 

99-01 7 9113 21 -1.0 1,196,100 

99-01 7 9116 11 -0.7 2,320,200 

99-01 7 1 8 -1.3 115,200 

99-01 7 2 17 -0.6 541,800 

99-01 7 3 1 -0.8 26,100 

99-01 8 -3 1 -0.9 5,400 

99-01 8 -2 5 -0.2 48,600 

99-01 8 -1 6 -0.8 35,100 

99-01 8 9113 11 -0.9 137,700 

99-01 8 9116 8 -1.0 953,100 

99-01 8 1 6 -1.6 185,400 

99-01 8 2 8 -0.4 38,700 

99-01 8 3 2 -0.6 32,400 

99-01 10 -3 4 -0.8 62,100 

99-01 10 -2 10 -1.2 252,900 

99-01 10 -1 5 -1.2 41,400 

99-01 10 9113 12 -0.9 135,000 

99-01 10 9116 16 -0.9 1,692,000 

99-01 10 1 13 -1.2 167,400 

99-01 10 2 27 -0.9 414,000 

99-01 10 3 7 -1.3 86,400 

99-01 11 -2 5 -0.9 93,600 

99-01 11 -1 4 -1.0 18,900 

99-01 11 9113 12 -1.1 642,600 

99-01 11 9116 11 -0.6 185,400 

99-01 11 1 4 -1.1 36,900 

99-01 11 2 9 -0.9 154,800 

99-01 11 3 3 -1.0 22,500 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page A-4-

Period Segment 

Change 

Category 

Number of 

Polygons 

Mean Elevation 

(m, MLLW) Area (m2) 

99-01 13 -3 7 -0.7 89,100 

99-01 13 -2 8 -0.7 155,700 

99-01 13 -1 4 -0.5 75,600 

99-01 13 9113 13 -0.6 406,800 

99-01 13 9116 11 -0.7 246,600 

99-01 13 1 2 -0.9 13,500 

99-01 13 2 11 -0.8 174,600 

99-01 13 3 3 -0.5 11,700 

99-01 14 -3 8 -0.7 132,300 

99-01 14 -2 11 -0.7 92,700 

99-01 14 -1 8 -0.6 302,400 

99-01 14 9113 21 -0.6 548,100 

99-01 14 9116 19 -0.6 889,200 

99-01 14 1 6 -0.9 98,100 

99-01 14 2 12 -0.5 125,100 

99-01 14 3 5 -0.7 54,900 

99-01 16 -3 10 -0.8 194,400 

99-01 16 -2 12 -0.8 128,700 

99-01 16 -1 8 -0.6 61,200 

99-01 16 9113 9 -0.5 178,200 

99-01 16 9116 14 -0.4 561,600 

99-01 16 2 13 -0.5 101,700 

99-01 16 3 1 -0.8 19,800 
 

Appendix B 

Distribution of water quality parameters by time period and by segment.
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page B-1- 

96-99 Period

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0

1

2

3

4

5

Atten

u

atio

n

C

oefficient m( -1

)

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0

5

10

15

20

T

urbidity

N( T

U)
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page B-2- 

96-99 Period

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0

50

100

150

C

olor (P

C

U)

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0.0

0.5

1.0

1.5

2.0

T

otal Nitro

g

e

n

m( g

L/ )
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page B-3- 

96-99 Period

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0

10

20

30

40

50

60

C

hloro

p

h

yll a (u

g

/

L)

1 2 3 5 6 7 8 10 11 13 14 16

Segment

10

20

30

40

S

alinity (P

S

U)
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page B-4- 

99-01 Period

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0

1

2

3

4

Atte

n

u

atio

n

C

o

e

fficie

nt m( -1

)

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0

5

10

15

20

T

urbidity

N( T

U)
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page B-5- 

99-01 Period

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0

50

100

150

200

C

olor (P

C

U)

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0

1

2

3

T

otal Nitro

gen

m( g

L/ )
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays -Page B-6- 

99-01 Period

1 2 3 5 6 7 8 10 11 13 14 16

Segment

0

10

20

30

40

C

hloro

p

h

yll a (u

g

/

L)

1 2 3 5 6 7 8 10 11 13 14 16

Segment

10

20

30

40

50

S

alinity (P

S

U)
 

Appendix C 

Period water quality means, mapped by segment
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

1996 - 1999 Mean K

0.5 - 0.70.7 - 0.90.9 - 1.11.1 - 1.31.3 - 1.5
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

*

*

* *

*

*

*

1999 - 2001 Mean Light Attenuation

0.5 - 0.70.7 - 0.90.9 - 1.11.1 - 1.31.3 - 1.5

* Data not available from 2001
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

1996 - 1999 Mean Color

5 - 1010 - 1515 - 2020 - 2525 - 30
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

1999 - 2001 Mean Color

5 - 1010 - 1515 - 2020 - 2525 - 30
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

1996 - 1999 Mean Chlorophyll

0 - 22 - 44 - 66 - 88 - 10
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

1999 - 2001 Mean Chlorophyll

0 - 22 - 44 - 66 - 88 - 10
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

1996 - 1999 Mean Turbidity

3 - 3.43.4 - 3.83.8 - 4.24.2 - 4.64.6 - 5
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

1999 - 2001 Mean Turbidity

3 - 3.43.4 - 3.83.8 - 4.24.2 - 4.64.6 - 5
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

1996 - 1999 Mean Total Nitrogen

0 - 0.20.2 - 0.40.4 - 0.60.6 - 0.80.8 - 1
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

1996 - 1999 Mean Salinity

25 - 2727 - 2929 - 3131 - 3232 - 35
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound,  Sarasota, Roberts, Little Sarasota, and Blackburn Bays 

1999 - 2001 Mean Salinity

25 - 2727 - 2929 - 3131 - 3232 - 35
Appendix D 

Time series of water quality parameter for the larger change polygons, by 

time period and by segment.
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-1-

Segment 1

1997 1998 1999 2000

Year

0

1

2

3

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-2-

Segment 1

1997 1998 1999 2000

Year

20

25

30

35

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

50

60

70

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

1

2

3

4

5

6

7

8

T

urbidity (N

T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-3-

Segment 2

1997 1998 1999 2000

Year

0

1

2

3

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-4-

Segment 16

1999 2000 2001 2002 2003

Year

10

20

30

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

50

100

150

200

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

1

2

3

4

5

6

7

8

9

10

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-5-

Segment 3

1997 1998 1999 2000

Year

0

1

2

3

4

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

5

10

15

20

25

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-6-

Segment 3

1997 1998 1999 2000

Year

20

25

30

35

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

50

60

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

1

2

3

4

5

6

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-7-

Segment 5

1997 1998 1999 2000

Year

0

1

2

3

4

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

5

10

15

20

25

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-8-

Segment 5

1997 1998 1999 2000

Year

25

30

35

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

50

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

2

4

6

8

10

12

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-9-

Segment 6

1997 1998 1999 2000

Year

0

1

2

3

4

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

5

10

15

20

25

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-10-

Segment 6

1997 1998 1999 2000

Year

20

25

30

35

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

50

60

70

80

90

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

2

4

6

8

10

12

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-11-

Segment 7

1997 1998 1999 2000

Year

0

1

2

3

4

5

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

C

hlorop

hyll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-12-

Segment 7

1997 1998 1999 2000

Year

10

20

30

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

50

60

70

80

90

100

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

2

4

6

8

10

12

T

urbidity (N

T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-13-

Segment 8

1997 1998 1999 2000

Year

0

1

2

3

4

5

6

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

2.0

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-14-

Segment 8

1997 1998 1999 2000

Year

0

10

20

30

40

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

50

100

150

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

5

10

15

20

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-15-

Segment 10

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

2.0

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

C

hlorop

hyll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-16-

Segment 10

1997 1998 1999 2000

Year

20

25

30

35

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

5

10

15

20

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

5

10

15

20

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-17-

Segment 11

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

2.0

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-18-

Segment 11

1997 1998 1999 2000

Year

20

25

30

35

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

5

10

15

20

25

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

5

10

15

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-19-

Segment 13

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

2.0

2.5

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-20-

Segment 13

1997 1998 1999 2000

Year

10

20

30

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

50

60

70

80

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

5

10

15

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-21-

Segment 14

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

2.0

2.5

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

2.0

2.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

50

60

70

80

90

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-22-

Segment 14

1997 1998 1999 2000

Year

10

20

30

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

50

60

70

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

5

10

15

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-23-

Segment 16

1997 1998 1999 2000

Year

0

1

2

3

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0.0

0.5

1.0

1.5

2.0

Total Nitrogen (m

g

L/ )

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

10

20

30

40

50

60

70

80

90

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-24-

Segment 16

1997 1998 1999 2000

Year

10

20

30

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

50

100

150

200

250

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1997 1998 1999 2000

Year

0

1

2

3

4

5

6

7

8

9

10

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-25-

Segment 1

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

20

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-26-

Segment 1

1999 2000 2001 2002 2003

Year

25

30

35

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

10

20

30

40

50

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

1

2

3

4

5

6

7

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-27-

Segment 2

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

20

C

hlorop

hyll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-28-

Segment 2

1999 2000 2001 2002 2003

Year

25

30

35

40

45

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

10

20

30

40

50

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

1

2

3

4

5

6

7

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-29-

Segment 3

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

2.5

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

20

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-30-

Segment 3

1999 2000 2001 2002 2003

Year

25

30

35

40

45

Salinity (PSU)

G

G

G

U

U

U

L

Category

1999 2000 2001 2002 2003

Year

10

20

30

40

50

Color (P

C

U)

G

G

G

U

U

U

L

Category

1999 2000 2001 2002 2003

Year

1

2

3

4

5

6

7

8

9

T

urbidity

N( T

U)

G

G

G

U

U

U

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-31-

Segment 5

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g/L)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

20

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-32-

Segment 5

1999 2000 2001 2002 2003

Year

25

30

35

40

45

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

10

20

30

40

50

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

1

2

3

4

5

6

7

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-33-

Segment 6

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

2.5

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

20

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-34-

Segment 6

1999 2000 2001 2002 2003

Year

20

25

30

35

40

45

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

10

20

30

40

50

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

1

2

3

4

5

6

7

8

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-35-

Segment 7

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-36-

Segment 7

1999 2000 2001 2002 2003

Year

25

30

35

40

45

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

10

20

30

40

50

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-37-

Segment 8

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

2.5

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

10

20

30

40

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-38-

Segment 8

1999 2000 2001 2002 2003

Year

10

20

30

40

50

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

20

40

60

80

100

120

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-39-

Segment 10

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

2.5

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

10

20

30

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-40-

Segment 10

1999 2000 2001 2002 2003

Year

20

25

30

35

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

10

20

30

40

50

60

70

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

20

25

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-41-

Segment 11

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

2.0

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

20

25

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-42-

Segment 11

1999 2000 2001 2002 2003

Year

25

30

35

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

10

20

30

40

50

60

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

20

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-43-

Segment 13

1999 2000 2001 2002 2003

Year

0

1

2

3

4

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.5

1.0

1.5

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

10

20

30

40

50

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-44-

Segment 13

1999 2000 2001 2002 2003

Year

0

10

20

30

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

50

100

150

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

20

25

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-45-

Segment 14

1999 2000 2001 2002 2003

Year

0

1

2

3

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

10

20

30

40

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-46-

Segment 14

1999 2000 2001 2002 2003

Year

10

20

30

40

Salinity (PSU)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

20

40

60

80

100

120

Color (P

C

U)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

5

10

15

T

urbidity

N( T

U)

G

G

G

U

U

U

L

L

L

Category
Mote Marine Laboratory 

Analysis of Changes in Seagrass Coverage, 1996-1999 and 1999-2001, for Anna Maria Sound, Sarasota, 

Roberts, Little Sarasota, and Blackburn Bays - Page D-47-

Segment 16

1999 2000 2001 2002 2003

Year

0

1

2

3

4

Atten

uation

Coefficient m( -1

)

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Total Nitrogen

m( g

L/ )

G

G

G

U

U

U

L

L

L

Category

1999 2000 2001 2002 2003

Year

0

10

20

30

40

50

C

hlorop

h

yll a (u

g/L)

G

G

G

U

U

U

L

L

L

Category