NUMERIC NUTRIENT CRITERIA

FOR SARASOTA BAY

Prepared for:

Sarasota Bay Estuary Program

Prepared by:

Janicki Environmental, Inc.

August 2010
ACKNOWLEDGMENTS 

This report benefited from critical input from the Sarasota Bay Estuary Program staff and the 

Technical Advisory Committee. Particular support was provided by Mark Alderson and Dr. Jay 

Leverone. The water quality subcommittee also provided continued input during this project 

including: 

Lizanne Garcia, Kris Kaufman, Veronica Craw – Southwest Florida Water Management 

District 

Charles Kovach, Pete Wenner – Florida Department of Environmental Protection 

Rob Brown, Greg Blanchard – Manatee County 

Jack Merriam, John Ryan, Jon Perry – Sarasota County 

Gary Serviss – VHB, Inc. 

Amber Whittle – Florida Fish and Wildlife Conservation Commission 

David Tomasko – PBS&J 

Kellie Dixon – Mote Marine Laboratory 

We would also like to acknowledge the very important input provided by Jones Edmunds & 

Associates, Inc. for their contributions to the SIMPLE model application with critical work provided 

by Brett Cunningham, Jason Icerman, Suzi Kaufmann, and Lisa Foster. 
ii

EXECUTIVE SUMMARY 

One of the major objectives of the Clean Water Act (CWA) is to restore and maintain the chemical, 

physical and biological integrity of the Nation’s waters to provide “water quality which provides for 

the protection and propagation of fish, shellfish, and wildlife and provides for recreation in and on 

the water”. On January 14, 2009 the U.S. Environmental Protection Agency (USEPA) determined 

under the CWA section 303(4)(B) that new or revised water quality standards expressed as numeric 

nutrient criteria (NNC) are necessary to meet the requirements of the CWA in the State of Florida. 

These criteria are numeric limits on the amount of phosphorus and nitrogen that would be allowed 

in Florida’s waters. NNC will provide baselines against which to measure environmental progress, 

to facilitate the writing of protective NPDES permits, and to develop defensible TMDLs. 

The original USEPA schedule for proposed estuarine and coastal water criteria was January 2011. 

This schedule has been recently modified and now requires USEPA to propose estuarine and 

coastal waters nutrient criteria and downstream protective values in Florida by November 14, 

2011. This revised schedule will allow more time for peer review by the Science Advisory Board 

(SAB) as well as an extended public comment period. 

In October 2009, the Sarasota Bay Estuary Program (SBEP) Policy and Management boards directed 

the Technical Advisory Committee (TAC) to develop numeric nutrient criteria for the estuarine 

waters of the Sarasota Bay system. The primary objectives of this project were to: 

 develop a data base of water quality and nutrient loads for each of the major bay segments; 

 define the chlorophyll a thresholds that meet light attenuation and seagrass targets in each 

bay segment; 

 define the quantitative relationships between nutrient concentrations or loading and 

chlorophyll a concentrations in each bay segment; and 

 estimate the numeric nutrient criteria, i.e., the nutrient concentrations or loading consistent 

with the chlorophyll a thresholds, for each bay segment. 

This effort would fulfill the need for establishing NNC based on the best available data for the 

following SBEP estuarine segments: 

 Palma Sola Bay 

 Sarasota Bay 

 Roberts Bay 

 Little Sarasota Bay 

 Blackburn Bay 

A water quality subcommittee of the TAC began the NNC development process by reviewing 

existing seagrass and chlorophyll a data and proposing a set of chlorophyll a targets to support the 

development of the NNC. This review confirmed that the recent extents of seagrasses are meeting 

the established targets; the subcommittee thus determined that the recent chlorophyll a

concentrations and resultant water clarity must be protective of the seagrasses in each of the 

segments. Upon review of the chlorophyll a concentration data, it was deemed appropriate to 

include not only the data from the 2004-2005 time frame but also data from several antecedent 
iii

years (2001-2003). The resultant mean chlorophyll a concentrations from this overall period 

(2001-2005) were established as the targets for each segment. These targets are: 

 Palma Sola Bay – 8.5 μg/L 

 Sarasota Bay – 5.2 μg/L 

 Roberts Bay – 8.2 μg/L 

 Little Sarasota Bay – 8.2 μg/L 

 Blackburn Bay – 6.0 μg/L 

The subcommittee further recognized that there may be years in which these targets may be 

exceeded without causing significant reductions in seagrass cover. This means that there is some 

allowable, or acceptable, amount of variation that should not elicit a significant degradation in 

water quality and therefore seagrass coverage. The subcommittee defined this level of variation as 

“the standard deviation around the mean annual chlorophyll a concentrations in each segment for 

the entire period of record”. Therefore, a distinction is made between a target, i.e., a desired 

chlorophyll a concentration and a threshold, i.e., a chlorophyll a concentration above which 

undesirable chlorophyll a concentrations exist and should not be exceeded. The chlorophyll a

threshold for each segment is “the sum of the target and the standard deviation around the mean 

annual chlorophyll a concentrations for that segment”. Therefore, the sum of the mean 

chlorophyll a concentrations for 2001-2005 and the standard deviation around the mean annual 

chlorophyll a concentrations for that segment are the thresholds that were used in the 

development of the numeric nutrient criteria in the SBEP estuarine waters. They are: 

 Palma Sola Bay – 11.8 μg/L 

 Sarasota Bay – 6.1 μg/L 

 Roberts Bay – 11.0 μg/L 

 Little Sarasota Bay – 10.4 μg/L 

 Blackburn Bay – 8.2 μg/L 

The water quality data used in these analyses were provided by Sarasota and Manatee counties. 

These data included monthly chlorophyll a, TN, TP, salinity, color, turbidity, and other variables. 

The nutrient and hydrologic loading estimates were developed by applying the Spatially Integrated 

Model for Pollutant Loading Estimates (SIMPLE) which was designed and calibrated by Jones 

Edmunds & Associates, Inc. for Sarasota County. In addition to the water quality and nutrient 

loading data, estimates of residence times for each segment were derived based on the physical 

features and hydrologic loads for each segment. 

A linear regression model approach was used to develop statistically defensible relationships 

between potential stressors and water quality responses. The independent variables used in the 

model building process included nutrient loadings, nutrient concentrations, and estimates of 

residence time. The loadings data included monthly hydrologic, TN, and TP loads as well as 

cumulative total loads extending from two to six months (e.g., 2-month cumulative TN load = TN 

load current month + TN load one- month prior). The water quality constituents included TN and 

TP concentrations along with numerous other constituents. 

The stressor-response relationships for Roberts Bay, Little Sarasota Bay, and Blackburn Bay 

indicated very similar responses in chlorophyll a concentrations to changes in nutrient 

concentrations. Specifically, two terms, TN concentration and season, explained more than 60% of 
iv

the variation in the chlorophyll a data. These results indicate that there are significant relationships 

between chlorophyll a and TN concentrations in each of these segments and that these 

relationships vary between the wet and dry seasons. The relationship between chlorophyll a and 

TN concentrations in Sarasota Bay is more complex. This relationship depends upon location 

within the segment (north vs. south) and the ambient water color. 

Based on the quantitative relationships between chlorophyll a and TN concentrations in each of 

these segments and the chlorophyll a thresholds, the NNC expressed as mean annual TN 

concentrations were determined for each segment. These criteria are: 

 Roberts Bay – 0.54 mg/L, 

 Little Sarasota Bay – 0.60 mg/L, 

 Blackburn Bay – 0.43 mg/L, and 

 Sarasota Bay – 0.28-1.34 mg/L (based on ambient water color for the period 1998-2009). 

No significant relationship was found between chlorophyll a concentrations and either nutrient (TN 

or TP) concentrations or loadings in Palma Sola Bay. Given this result, an alternative method for 

proposing NNC for Palma Sola Bay was necessary. 

The SBEP water quality subcommittee of the TAC considered three potential candidate methods for 

estimating the TN criterion for Palma Sola Bay. These methods included a logistic regression 

approach, a changepoint analysis approach, and an approach similar to that used to define the 

chlorophyll a thresholds. All three potential candidate methods give relatively similar results. The 

subcommittee recommended the third option – i.e., that based on the 2001-2005 ambient TN 

data. The proposed NNC for Palma Sola Bay is: 

 a mean annual TN concentration of 0.93 mg/L. 

The full TAC concurred with the subcommittee’s recommendation on 23 July 2010. 
1

I. Introduction 

The Sarasota Bay Estuary Program (SBEP) began in June 1989 when Sarasota Bay was designated 

an "estuary of national significance" by the U.S. Congress as part of the Water Quality Act of 

1987. SBEP is one of 28 National Estuary Programs (www.epa.gov/nep/) in the United States. The 

Sarasota Bay Estuary Program is a member of the Association of National Estuary Programs 

(www.nationalestuaries.org/). 

The SBEP partners include: 

 Sarasota County, 

 Manatee County, 

 City of Sarasota, 

 City of Bradenton, 

 Town of Longboat Key, 

 Florida Department of Environmental Protection, 

 Southwest Florida Water Management District, and 

 U.S. Environmental Protection Agency. 

SBEP was initially tasked with characterizing the environmental conditions of Sarasota Bay and 

formulating a comprehensive restoration and protection plan based upon this analysis. The 

resulting plan was the Comprehensive Conservation and Management Plan (CCMP). 

The CCMP recommends specific actions to be taken by local governments as well as state and 

federal agencies to restore and protect Sarasota Bay. The CCMP was formally approved by the 

Governor of Florida and the Administrator of the U.S. Environmental Protection Agency in 1995. 

SBEP has been a focal point for the local government agencies and assists them in their efforts to 

protect water quality in the estuarine waters of the area. To this end, SBEP has provided a forum for 

the establishment of critical environmental endpoints to assure increasingly difficult funding 

opportunities are being effectively applied. 

II. Objectives 

The primary objectives of this project are: 

 To develop a data base of water quality and nutrient loads for each of the major bay 

segments; 

 To define the chlorophyll a thresholds that meet light attenuation and seagrass targets in 

each bay segment; 

 To define the quantitative relationships between nutrient concentrations or loading and 

chlorophyll a concentrations in each bay segment; and 

 To estimate the numeric nutrient criteria, i.e., the nutrient concentrations or loading 

consistent with the chlorophyll a thresholds, for each bay segment.
2

III. SBEP Goals and Targets 

Sarasota Bay is a coastal lagoonal system formed by a necklace of barrier islands to the west and 

the mainland of Manatee and Sarasota Counties to the east (Figure III-1). This coastal lagoon, with 

its unique ecological character of small embayments, tidal tributaries and small creeks, coves, inlets 

and passes, is bounded by Anna Maria Sound to the north and stretches all the way to just north of 

the Venice Inlet, which serves as its southern boundary. The overall watershed is approximately 

455 square miles. The bay itself is approximately 56 miles long and has an average depth of 6.5 

feet. 

Sarasota Bay is made of a series of smaller bays or segments. Each of these segments are unique 

from one another. They differ in overall size, shape and water depth, shoreline features, habitat 

and sediment characteristics. These unique characteristics lead to differences in water circulation, 

freshwater inputs, nutrient loads, as well as other consequences for health and vitality. Because of 

these differences, each embayment must be analyzed and managed independently from the others 

at the same time recognizing their connectivity. 

The Sarasota Bay Estuary Program recognizes the following segments as having their own unique 

set of conditions and influences: Palma Sola Bay, Sarasota Bay proper, Roberts Bay, Little Sarasota 

Bay, and Blackburn Bay. 

Figure III-1. - Sarasota Bay Estuary Program segments and their watersheds. 
3

Sarasota Bay was named an estuary of “national significance” in 1987 which led to its designation 

as a National Estuary Program by the EPA two years later. The Sarasota Bay Estuary Program is 

dedicated to improving and protecting the area’s greatest and most important natural asset - 

Sarasota Bay. The SBEP strives to improve water quality, increase habitat and enhance the natural 

resources of the area for use and enjoyment by the public. 

A Management Conference was formed comprising federal, state, regional and local officials who 

oversaw the development and implementation of a Comprehensive Conservation and Management 

Plan (CCMP) for Sarasota Bay. The Policy Committee established the goals, objectives, budgets and 

work plans for the conference. 

Several priority concerns were identified: 

 Declines in water and sediment quality 

 Loss of wetlands and other coastal habitats 

 Loss of seagrasses 

 Declines in finfish and shellfish populations 

 Overuse 

The Management Conference also developed plans of action to address these concerns through 

technical studies and citizen action plans which resulted in the development of the CCMP in 1995. 

Progress in the implementation of the CCMP has been documented. A State of the Bay report 

(SBEP, 2010) has been recently completed and a summary of these accomplishments is given in 

Appendix 1. 

In addition to other goals, the SBEP has established quantitative targets for the restoration and 

protection of seagrasses (Janicki et al., 2009) and for water quality, specifically chlorophyll a

concentrations (Janicki Environmental, 2010a). 

III-1. Seagrass Targets 

One of the primary SBEP goals is to maintain and/or restore seagrass coverage to its historic extent. 

The seagrass target project provided technically-defensible quantitative seagrass targets for the 

Sarasota Bay ecosystem. Establishment of seagrass targets provides a necessary basis for 

management decisions regarding water quality and other issues that can influence the distribution 

and persistence of this resource. Targets were defined through an analysis of historic and recent 

aerial surveys of the study area. 

The historic aerial photos used to establish the baseline extent of seagrass in the study area were 

dated circa 1950. Recent trends in and persistence of seagrass throughout the SBEP were 

determined through analysis of GIS shapefiles based on aerial surveys executed biannually by the 

Southwest Florida Water Management District since 1988. Due to anthropogenic modifications in 

the estuary such as shoreline build-out and the dredging of the Intracoastal Waterway (ICW), certain 

areas have been altered to the extent that they have no reasonable potential for restoration; these 

so-called non-restorable areas have been identified and removed from the analyses. 

The trend analyses show that Sarasota Bay proper is currently at its highest seagrass level since 

1950 and exceeds the baseline extent (Figures III-2 – III-65). The seagrass coverage in Roberts Bay 
4

and Blackburn bays also increased since the baseline period. In Palma Sola Bay, the seagrass 

coverage has remained very similar over the entire period of record. In contrast, Little Sarasota Bay 

has shown a decline in seagrasses since 1950. 

The definition of the most appropriate seagrass targets was reached with input from the Technical 

Advisory Committee (TAC). The TAC recommended that the greater of either the historic or recent 

(2004-2006) seagrass coverages be established as the target in each segment. The sole exception to 

this rule was Little Sarasota Bay. Since 1984, the direct connection to the Gulf of Mexico (Midnight 

Pass) has been closed. This physical alteration may have contributed to the difference in seagrass 

coverage between the historic and current coverages. However, a recent FDEP decision precludes 

re-opening of this pass. Therefore, the recent coverage in Little Sarasota Bay has been established 

as the target. Table III-1 presents the seagrass targets that were adopted by the SBEP Management 

and Policy boards. 

Figure III-2. Annual seagrass acreages in Palma Sola Bay. Horizontal line = seagrass target. 

0

200

400

600

800

1000

1200

1950 1988 1994 1999 2001 2004 2006
5

Figure III-3. Annual seagrass acreages in Sarasota Bay. Horizontal line = seagrass target. 

 

Figure III-4. Annual seagrass acreages in Roberts Bay. Horizontal line = seagrass target. 

0

1000

2000

3000

4000

5000

6000

7000

8000

1950 1988 1994 1999 2001 2004 2006

0

50

100

150

200

250

300

350

400

1950 1988 1994 1999 2001 2004 2006
6

Figure III-5. Annual seagrass acreages in Little Sarasota Bay. Horizontal line = seagrass target. 

Figure III-6. Annual seagrass acreages in Blackburn Bay. Horizontal line = seagrass target. 

0

100

200

300

400

500

600

700

800

900

1000

1950 1988 1994 1999 2001 2004 2006

0

50

100

150

200

250

300

350

400

450

500

1950 1988 1994 1999 2001 2004 2006
7

Table III-1. SBEP seagrass coverage and targets. Unit of 

measure=acres. 

Bay Segment Historical 

(1950) 

Current 

2004-2006 

Average 

Seagrass 

Target 

Palma Sola 1,031 1,015 1,031 

Sarasota 7,269 7,041 7,269 

Roberts 283 348 348 

Little Sarasota 883 702 702 

Blackburn 273 447 447 

Total 9,739 9,552 9,997 

III-2. Chlorophyll a Targets and Thresholds 

In October 2009, the SBEP Policy and Management boards directed the TAC to develop numeric 

nutrient criteria for the estuarine waters of the area. A subcommittee of the TAC began the process 

by reviewing the existing seagrass and chlorophyll a data and proposing a set of chlorophyll a

targets to support the development of the numeric nutrient criteria (Janicki Environmental, 2010). 

Given that the recent extents of seagrasses are meeting the established targets, the subcommittee 

determined that the recent chlorophyll a concentrations and resultant water clarity are protective of 

the seagrasses in each of the SBEP segments. Upon review of the chlorophyll a concentration data, 

it was deemed appropriate to include not only the data from the 2004-2005 period but also from 

several antecedent years (2001-2003). The resultant mean chlorophyll a concentrations from this 

overall period (2001-2005) were established as the targets for each segment (Table III-2). The 

subcommittee further recognized that there may be years in which these targets may be exceeded 

without causing significant reductions in seagrass cover. This means that there is some allowable 

amount of variation that should not elicit a significant degradation in water quality and therefore 

seagrass coverage. The subcommittee defined this level of variation as the standard deviation 

around the mean annual chlorophyll a concentrations in each segment for the entire period of 

record. Therefore, a distinction is made between a target, i.e., a desired chlorophyll a

concentration and a threshold, i.e., a chlorophyll a concentration above which undesirable 

chlorophyll a concentrations exist. The chlorophyll a threshold for each segment is the sum of the 

target and the standard deviation around the mean annual chlorophyll a concentrations in each 

segment. The thresholds shown in Table III-1 are used in later sections of this report in the 

development of the numeric nutrient criteria in the SBEP estuarine waters. 

Table III-2. Recommended chlorophyll a targets and thresholds (μg/L). 

Bay Segment Target Chlorophyll a

(μg/L) 

Inter-annual Variability 

(1 SD of Annual Means)

Threshold Chlorophyll a

(μg/L) 

Palma Sola 8.5 3.3 11.8 

Sarasota 5.2 0.9 6.1 

Roberts 8.2 2.8 11.0 

Little Sarasota 8.2 2.2 10.4 

Blackburn 6.0 2.2 8.2 
8

IV. Recent Water Quality Assessments 

This section provides an examination of water quality data for total nitrogen (TN), total phosphorus 

(TP), chlorophyll a, and salinity within the SBEP estuarine area to identify any spatial and temporal 

trends. Bay segments in the SBEP area include Palma Sola Bay, Sarasota Bay, Roberts Bay, Little 

Sarasota Bay, and Blackburn Bay (Figure IV-1). This summary will be used to assist in setting 

locally-appropriate numeric nutrient criteria for estuaries in the SBEP system. 

Figure IV-1. - Sarasota Bay Estuary Program segments and their watersheds. 
9

IV-1.0 Ambient Water Quality Sampling Programs in the SBEP Area 

Both Sarasota County and Manatee County collect water quality data within the SBEP area. The 

two monitoring programs are briefly described below. Maps showing the sampling sites from both 

programs are presented in Appendix 2. 

The Sarasota County ambient water quality monitoring program was initiated in 1998. Sarasota 

Bay was divided into 12 segments, each with multiple randomly chosen sampling sites. Samples 

are collected on a monthly basis from each segment. All sample locations are sampled once every 

year. Each sampling location is also re-sampled every year in the same month as the preceding 

years. This stratified random monitoring program characterizes overall estuarine health by 

describing entire bay segments rather than isolated locations in each water body. 

The Manatee County Environmental Management Department (EMD) ambient water quality 

monitoring program for Manatee County's estuarine waters is the Regional Ambient Monitoring 

Program (RAMP). The Manatee County RAMP program divides the County's estuarine area into 

two segments of 24,356 km2 hexagonal sampling areas each. The south segment includes Palma 

Sola Bay and Sarasota Bay north of the county line, both of which are within the SBEP area. 

Sampling points were randomly located within each hexagon at the start of the program. A 

hexagonal sampling area was included in the program if the randomly generated sampling point 

was at least 4ft deep by the nautical chart and verified during program reconnaissance. One-third 

of the sampling points in each segment, eight points, are sampled monthly. All sampling points in a 

segment are visited within each calendar quarter. In bay segments where both Sarasota and 

Manatee counties collected data, these data were averaged. 

Times series of monthly mean values for each bay segment were produced to allow visual 

inspection of trends over time and to allow a comparison between bay segments. Trends in 

chlorophyll a, TN, or TP concentrations were assessed using graphical plots and the seasonal 

Kendall Tau trend test (Hirsch et al., 1982; Hirsch and Slack, 1984; Reckhow, 1993). The seasonal 

Kendall Tau is a nonparametric test that estimates the median slope from all pair-wise comparisons 

in a timeseries of data. The statistical test accounts for seasonality and serial autocorrelation prior 

to evaluating the statistical significance of the trend in the time series. Therefore, the seasonal 

Kendall Tau is a sophisticated and robust method to evaluate trends in water quality data that often 

do not fit the assumptions necessary for the use of parametric statistics (e.g. linear regression). 

In addition to the examination of inter-annual variability, box and whisker plots were generated to 

examine within-year variability in water quality in each of the bay segments. 

Besides tidal action, rainfall provides a driver for changes to surface water quality. Both direct 

rainfall on a water body and stormwater runoff from the watershed cause nonpoint source loadings 

to be a major factor in most receiving waters’ quality. Annual rainfall for the 1998 though 2009 
10

period is summarized in Table IV-1. The rainfall data are described in Chapter V below. It may be 

expected that years with high rainfall would cause changes to water quality, such as lower salinity, 

in segments with larger watersheds, while segments with smaller watersheds that contribute runoff 

would show less of an effect. 

Table IV-1. Annual rainfall in the SBEP area 

sorted by rainfall. 

Year Rainfall (inches) 

2000 32.8 

2007 34.2 

2009 43.4 

2008 44.2 

2006 45.3 

2001 46.9 

1999 49.7 

2004 51.9 

2002 53.4 

1998 57.3 

2003 60.3 

2005 61.2 

IV-2.0 Ambient Water Quality Assessment 

The following summarizes annual and seasonal trends in salinity, TN, TP, and chlorophyll a for 

each SBEP bay segment. Results are based on a review of data for the period January 1998 through 

December 2009, except Palma Sola Bay that had data available only through December 2008. 

IV-2.1 Palma Sola Bay 

IV-2.1.1 Salinity 

Mean annual salinity for the 1998 through 2008 period in Palma Sola Bay averaged 29.8 parts per 

thousand (ppt) (Figure IV-2). The lowest annual value, 22.3 ppt occurred in 2008 and the highest 

annual value, 34.8 ppt, occurred in 2000, a very dry year (Table IV-1). There was no significant 

trend in salinity in Palma Sola Bay over this time period (p>0.05; Appendix 2). 

The box-and-whisker plots for salinity show values lower in the summer wet season than in the dry 

season, as would be expected (Figure IV-3). Monthly means range from 32.1ppt (May) to 25.0 ppt 

(October). 
11

Figure IV-2. Mean monthly salinity (ppt) observed in Palma Sola Bay. The line is 

a least squares fit to the data. 

Figure IV-3. Box-and-whisker plots of the mean monthly salinity (ppt) observed in Palma Sola Bay. 

IV-2.1.2 Chlorophyll a

Mean annual chlorophyll a concentrations for the 1998-2008 period in Palma Sola Bay averaged 

8.25 μg/L (Figure IV-4). The lowest annual value of 4.89 μg/L occurred in 2005, a significantly wet 

year (Table IV-1). Lower chlorophyll concentrations may be expected if higher volumes of 

freshwater are reducing residence time on an annual basis. The highest annual value, 11.3 μg/L, 

occurred in 1998, also a wet year. A significant decreasing trend in chlorophyll a concentrations 

was observed during the 1998-2008 period (p<0.0001, Appendix 3). 
12

Figure IV-4. Mean monthly chlorophyll a concentrations (μg/L) observed in Palma Sola Bay. 

Chlorophyll a monthly box-and-whisker plots show a definite seasonal signal (Figure IV-5). During 

the warmer summer months when nutrient loading is typically greatest and day length increases, 

the mean monthly chlorophyll a concentrations are much higher than those observed in the dry, 

cooler period of the year. Monthly means range from 12.4 μg/L (July) to 5.26 μg/L (November). 

Figure IV-5. Box-and-whisker plots of the mean monthly chlorophyll a concentrations (μg/L) 

observed in Palma Sola Bay. 
13

IV-2.1.3 Total Nitrogen 

The mean annual TN concentrations for the 1998-2008 period in Palma Sola Bay averaged 0.77 

mg/L (Figure IV-6). The lowest annual concentration (0.59 mg/L) occurred in 2004; the highest 

annual value of 1.09 mg/L occurred in the drought year of 2001. There was no significant trend in 

TN concentrations in Palma Sola Bay over this time period (p>0.05; Appendix 3). 

The box-and-whisker plot for TN suggests some intra-annual trend in TN concentrations (Figure IV7). Values are somewhat higher in the late summer months. Monthly means range from 1.03 mg/L 

(September) to 0.59 mg/L (April). Higher monthly values during the summer are likely the result of 

increased TN loading during the wetter summer months. 

Figure IV-6. Mean monthly TN concentrations (mg/L) observed in Palma Sola Bay. 

Figure IV-7. Box-and-whisker plots of the mean monthly TN concentrations (mg/L) observed in 

Palma Sola Bay. 
14

IV-2.1.4 Total Phosphorus 

Mean annual TP for the 1998-2008 period in Palma Sola Bay averaged 0.16 mg/L. The lowest 

annual value (0.07 mg/L) occurred in 2004, a moderately wet year (Table IV-1). The highest annual 

value (0.33 mg/L) occurred in 2008. A statistically significant, but slight increasing trend in TP 

concentrations was observed during the 1998-2008 period (p<0.0001, Appendix 3). 

Figure IV-8. Mean monthly TP concentrations (mg/L) observed in Palma Sola Bay. 

Unlike TN, there was very little within-year variability in TP concentrations (Figure IV-9). Monthly 

means for March, April, and May are as high as summer month values. Monthly means range from 

0.22 mg/L (May) to 0.10 mg/L (November). 

Figure IV-9. Box-and-whisker plots of the mean monthly TP concentrations (mg/L) observed in 

Palma Sola Bay. 
15

IV-2.2 Sarasota Bay 

IV-2.2.1 Salinity 

Mean annual salinity for the 1998 through 2009 period in Sarasota Bay averaged 34.5 ppt (Figure 

IV-10). The lowest annual value, 31.9 ppt, occurred in 1998, a wet year as shown in Table IV-1. 

The highest mean annual salinity, 36.3 ppt, occurred in 2008, a dry year. There was a significant 

increasing trend in salinity in Sarasota Bay over this time period (p<0.01; Appendix 3). 

Figure IV-10. Mean monthly salinity (ppt) observed in Sarasota Bay. 

The salinity box-and-whisker plots show values somewhat lower in the summer wet season than in 

the dry season, as would be expected, but the within-year variation is not great with monthly 

means varying less than 3 ppt. Monthly means range from 35.3 ppt (June) to 32.8 ppt (January). 

Figure IV-11. Box-and-whisker plots of the mean monthly salinity (ppt) observed in Sarasota Bay. 
16

IV-2.2.2 Chlorophyll a

Mean annual chlorophyll a for the 1998 through 2009 period in Sarasota Bay averaged 5.0 μg/L 

(Figure IV-12). The lowest annual value of 3.3 μg/L occurred in 2006, a year of moderate rainfall 

(Table IV-1). The highest annual value, 6.0 μg/L, occurred in 2009, a dry year. There was a 

statistically significant but slight decreasing trend in chlorophyll a concentrations in Sarasota Bay 

during this period (p<0.03, Appendix 3). 

Figure IV-12. Mean monthly chlorophyll a concentrations (μg/L) observed in Sarasota Bay. 

Box-and-whisker plots of the mean monthly chlorophyll a concentrations show a definite seasonal 

signal (Figure IV-13). During the warmer summer months the mean monthly chlorophyll a 

concentrations were approximately 3X higher than those observed in the dry period. Monthly 

means range from 9.3 μg/L (September) to 2.8 μg/L (February)." 

Figure IV-13. Box-and-whisker plots of the mean monthly chlorophyll a concentrations (μg/L) 

observed in Sarasota Bay. 
17

IV-2.2.3 Total Nitrogen 

The mean annual TN concentrations for the 1998 through 2009 period in Sarasota Bay averaged 

0.35 mg/L (Figure IV-14). The lowest annual value of 0.28 mg/L occurred in 2006, a moderately 

dry year (Table IV-1). The highest mean annual concentration of 0.41 mg/L occurred in 2004, a 

somewhat wetter year. There was no statistically significant trend in TN concentrations in Sarasota 

Bay during this period (p>0.05, Appendix 3). 

The box-and-whisker plot for mean monthly TN concentrations suggests some within-year variation 

with somewhat higher concentrations in the late summer months (Figure IV-15). Monthly means 

range from 0.49 mg/L (September) to 0.29 mg/L (February). 

Figure IV-14. Mean monthly TN concentrations (mg/L) observed in Sarasota Bay. 

Figure IV-15. Box-and-whisker plots of the mean monthly TN concentrations (mg/L) observed in 

Sarasota Bay. 
18

IV-2.2.4 Total Phosphorus 

Mean annual TP concentrations for the 1998-2009 period in Sarasota Bay averaged 0.13 mg/L 

(Figure IV-16). The lowest mean annual concentration of 0.06 mg/L occurred in 2009, while the 

highest annual value, 0.22 mg/L, occurred in 2002. There was a statistically significant but slight 

decreasing trend in Sarasota Bay TP concentrations during this period (p<0.03, Appendix 3). 

Figure IV-16. Mean monthly TP concentrations (mg/L) observed in Sarasota Bay. 

The box-and-whisker plot of mean monthly TP concentrations shows higher concentrations more 

likely during the summer months (Figure IV-17). Monthly means range from 0.18 mg/L (July) to 

0.09 mg/L (November), a two-fold difference. 

Figure IV-17. Box-and-whisker plots of the mean monthly TP concentrations (mg/L) observed in 

Sarasota Bay. 
19

IV-2.3 Roberts Bay 

IV-2.3.1 Salinity 

Mean annual salinity for the 1998-2009 period in Roberts Bay averaged 31.3 pp (Figure IV-18). 

The lowest annual value, 28.6 ppt, occurred in 2003, a wet year (Table IV-1). The highest annual 

value, 33.6 ppt, occurred in the 2000 drought year. There was no statistically significant trend in 

salinity in Roberts Bay during this period (p>0.05, Appendix 2). 

Figure IV-18. Mean monthly salinity (ppt) observed in Roberts Bay. 

The salinity box-and-whisker plots for salinity show the most distinct seasonal pattern among the 

SBEP segments, with summer wet season salinities much lower than in the dry season as would be 

expected (Figure IV-19). Roberts Bay exhibits this wide within-year variation due to the significant 

freshwater inputs delivered by Phillippi Creek. Monthly means range from 34.9 ppt to 27.2 ppt. 

Figure IV-19. Box-and-whisker plots of the mean monthly salinity (ppt) observed in Roberts Bay. 
20

IV-2.3.2 Chlorophyll a

Mean annual chlorophyll a concentrations for the 1998-2009 period in Roberts Bay averaged 7.3 

μg/L (Figure IV-20). The lowest mean annual concentration of 3.6 μg/L occurred in 2007, a dry 

year (Table IV-1). The highest mean annual concentration, 11.6 μg/L, occurred in the drought year 

of 2001. There was no statistically significant trend in chlorophyll a concentrations in Roberts Bay 

during this period (p>0.05, Appendix 3). 

The box-and-whisker plot of mean monthly chlorophyll a concentrations shows significant withinyear variation (Figure IV-21), with values during the hotter summer months over five times as high 

as the cooler period of the year. Monthly means range from 16.8 μg/L to 2.97 μg/L. 

Figure IV-20. Mean monthly chlorophyll a concentrations (μg/L) observed in Roberts Bay. 

Figure IV-21. Box-and-whisker plots of the mean monthly chlorophyll a concentrations (μg/L) 

observed in Roberts Bay. 
21

IV-2.3.3 Total Nitrogen 

The mean annual TN concentrations for the 1998 through 2009 period in Roberts Bay North 

averaged 0.43 mg/L (Figure IV-22). There was very little inter-annual variation in TN 

concentrations. The lowest annual value of 0.36 mg/L occurred in 2007 with the highest mean 

annual TN concentration of 0.48 mg/L observed in 2002. There was no statistically significant 

trend in TN concentrations in Roberts Bay during this period (p>0.05, Appendix 3). 

Figure IV-22. Mean monthly TN concentrations (mg/L) observed in Roberts Bay. 

The box-and-whisker plot for TN presents a distinct seasonal trend in TN concentrations (Figure IV23). The highest TN concentrations were observed in the late summer months (July, August, and 

September) and lowest during the winter months. Monthly means range from 0.59 mg/L 

(September) to 0.34 mg/L (April). 

Figure IV-23. Box-and-whisker plots of the mean monthly TN concentrations (mg/L) 

observed in Roberts Bay. 
22

IV-2.3.4 Total Phosphorus 

Mean annual TP concentrations for the 1998 through 2009 period in Roberts Bay averaged 0.17 

mg/L (Figure IV-24). The lowest mean annual TP concentration (0.09 mg/L) occurred in 2009 and 

the highest annual mean annual (0.22 mg/L) was observed in 2001. There was a significant 

decreasing trend in Roberts Bay TP concentrations during this period (p<0.0001, Appendix 3). 

Figure IV-24. Mean monthly TP concentrations (mg/L) observed in Roberts Bay. 

There was an appreciable within-year variation in Roberts Bay TP concentrations (Figure IV-25). 

Mean monthly TN concentrations ranged from 0.21 mg/L (August) to 0.14 mg/L (January). 

Figure IV-25. Box-and-whisker plots of the mean monthly TP concentrations (mg/L) observed in 

Roberts Bay. 
23

IV-2.4 Little Sarasota Bay

IV-2.4.1 Salinity 

Mean annual salinity for the 1998-2009 period in Little Sarasota Bay averaged 30.8 ppt (Figure IV26). The lowest annual value, 27.3 ppt, occurred in 2005, a wet year (Table IV-1). The highest 

mean annual salinity, 33.6 ppt, was observed 2007. There was no statistically significant trend in 

salinity in Little Sarasota Bay during this period (p>0.05, Appendix 3). 

Figure IV-26. Mean monthly salinity (ppt) observed in Little Sarasota Bay. 

The box-and-whisker plots for the mean monthly salinity in Little Sarasota Bay show a clear 

seasonal pattern, with summer wet season salinities much lower than those observed in the dry 

season (Figure IV-27). Monthly mean salinity ranged from 34.6 ppt (June) to 25.8 ppt (September). 

Figure IV-27. Box-and-whisker plots of the mean monthly salinity (ppt) observed in Little Sarasota 

Bay. 
24

IV-2.4.2 Chlorophyll a

Mean annual chlorophyll a concentrations averaged 7.3 μg/L in Little Sarasota Bay during the 1998-

2009 period (Figure IV-28). The lowest mean annual chlorophyll a concentration of 4.9 μg/L 

occurred in 2007 and the highest mean annual chlorophyll a concentration, 11.2 μg/L, occurred in 

2007. There was a statistically significant but slight decreasing trend in chlorophyll a 

concentrations in Little Sarasota Bay during this period (p<0.05, Appendix 3). 

Figure IV-28. Mean monthly chlorophyll a concentrations (μg/L) observed in Little Sarasota Bay. 

The mean monthly chlorophyll a concentrations exhibited a distinct seasonal signal (Figure IV-29). 

Monthly means ranged from 15.3 μg/L (September) to 3.4 μg/L (January). 

Figure IV-29. Box-and-whisker plots of the mean monthly chlorophyll a concentrations (μg/L) 

observed in Little Sarasota Bay. 
25

IV-2.4.3 Total Nitrogen 

The mean annual TN concentrations in Little Sarasota Bay for the 1998 through 2009 period 

averaged 0.49 mg/L (Figure IV-30). The lowest mean annual TN concentration of 0.43 mg/L was 

observed in 1998 while the highest mean annual TN concentration was 0.56 mg/L found in 2001. 

There was no statistically significant trend in Little Sarasota Bay TN concentrations during this 

period (p>0.05, Appendix 3). 

Figure IV-30. Mean monthly TN concentrations (mg/L) observed in Little Sarasota Bay. 

The TN concentrations in Little Sarasota Bay were higher in the late summer months (Figure IV-31). 

Monthly mean TN concentrations ranged from 0.64 mg/L (September) to 0.39 mg/L (January). 

Figure IV-31. Box-and-whisker plots of the mean monthly TN concentrations (mg/L) observed in 

Little Sarasota Bay. 
26

IV-2.4.4 Total Phosphorus 

Mean annual TP concentrations in Little Sarasota Bay averaged 0.17 mg/L during the 1998-2009 

period (Figure IV-32). The lowest mean annual TP concentration was 0.09 mg/L in 2009; while the 

highest mean annual concentration was 0.22 mg/L in 1999. There was a statistically significant 

decreasing trend in Little Sarasota Bay TP concentrations during this period (p<0.02, Appendix 3). 

Figure IV-32. Mean monthly TP concentrations (mg/L) observed in Little Sarasota Bay. 

There was little within-year variation in TP concentrations in Little Sarasota Bay during this period 

(Figure IV-33). 

Figure IV-33. Box-and-whisker plots of the mean monthly TP concentrations (mg/L) observed in 

Little Sarasota Bay. 
27

IV-2.5 Blackburn Bay

IV-2.5.1 Salinity 

Mean annual salinity in Blackburn Bay in the 1998-2009 period averaged 33.5 ppt (Figure IV-34). 

The lowest mean annual salinity was 30.3 ppt which occurred in 2005, a relatively wet year (Table 

IV-1). The highest annual mean salinity was 35.7 ppt and occurred in 2000. There was no 

statistically significant trend in Blackburn Bay salinity during this period (p>0.05, Appendix 3). 

Figure IV-34. Mean monthly salinity (ppt) observed in Blackburn Bay. 

Figure IV-35. Box-and-whisker plots of the mean monthly salinity (ppt) observed in Blackburn Bay. 
28

IV-2.5.2 Chlorophyll a

Mean annual chlorophyll a concentrations for the 1998-2009 period in Blackburn Bay averaged 5.3 

μg/L (Figure IV-36). The lowest annual mean chlorophyll a concentration was 3.0 μg/L and 

occurred in 2007. The highest annual mean chlorophyll a concentration was 9.3 μg/L and was 

observed in 2001. There was a significant decreasing trend in chlorophyll a concentrations in 

Blackburn Bay during this period (p<0.0001, Appendix 3). 

Figure IV-36. Mean monthly chlorophyll a concentrations (μg/L) observed in Blackburn Bay. 

The mean monthly chlorophyll a concentrations show a definite seasonal signal, with the highest 

concentrations observed during the summer months (Figure IV-37). Monthly mean concentrations 

ranged from 11.9 μg/L (September) to 1.9 μg/L (January). 

Figure IV-37. Box-and-whisker plots of the mean monthly chlorophyll a concentrations (μg/L) 

observed in Blackburn Bay. 
29

IV-2.5.3 Total Nitrogen 

The mean annual TN concentrations during the 1998-2009 period in averaged 0.34 mg/L (Figure 

IV-38). The lowest annual mean TN concentration of 0.26 mg/L occurred in 1998. The highest 

annual mean concentration of 0.41 mg/L was observed in 2005. There was a statistically significant 

increasing trend in TN concentrations in Blackburn Bay during this period (p<0.05, Appendix 3). 

Figure IV-38. Mean monthly TN concentrations (mg/L) observed in Blackburn Bay. 

The box-and-whisker plot for mean monthly TN concentrations show a distinct pattern with the 

highest TN concentrations observed from July through October (Figure IV-39). The monthly mean 

TN concentrations ranged from 0.49 mg/L (September) to 0.23 mg/L (May). 

Figure IV-39. Box-and-whisker plots of the mean monthly TN concentrations (mg/L) observed in 

Blackburn Bay. 
30

IV-2.5.4 Total Phosphorus 

The annual mean TP concentrations in Blackburn Bay averaged 0.15 mg/L during the 1998-2009 

period (Figure IV-40). The lowest annual mean of 0.06 mg/L occurred in 2009. The highest annual 

mean TP concentration was 0.21 mg/L and was observed in 2001. There was no statistically 

significant trend in Blackburn Bay TP concentrations during this period (p>0.05, Appendix 3). 

Figure IV-40. Mean monthly TP concentrations (mg/L) observed in Blackburn Bay. 

There was a slight seasonal trend in TP concentrations with slightly higher concentrations observed 

during the summer months (Figure IV-41). Monthly mean TP concentrations ranged from 0.17 

mg/L (October) to 0.12 mg/L (November). 

Figure IV-41. Box-and-whisker plots of the mean monthly TP concentrations (mg/L) observed in 

Blackburn Bay. 
31

IV-3 Summary 

The five SBEP bay segments exhibit a range of water quality characteristics based on watershed 

size, tributaries, estuary shape and size, and flushing rate and circulation. Because of the limited 

size and similar land use of most of the watersheds, flushing and tidal exchange appears to be a 

critical factor in water quality in the bay segments. 

Sarasota Bay and Blackburn Bay have the best tidal exchange with the Gulf of Mexico. These two 

segments have the highest average annual salinity and lowest average annual TN, TP, and 

chlorophyll a concentrations of the SBEP segments. 

Palma Sola Bay and Little Sarasota Bay have the most restricted tidal exchange, and have the lowest 

salinity and highest TN, TP, and chlorophyll a concentrations of the segments. Roberts Bay 

receives significant nonpoint source loading from Phillippi Creek but has tidal exchange with the 

Gulf of Mexico via Big Sarasota Pass. 

Temporal trends in the four parameters varied significantly. Salinity showed an increasing trend in 

all segments except Palma Sola which had a slight downward trend. Trends in TN varied from 

slightly increasing (Palma Sola Bay) to strongly decreasing (Sarasota Bay). TP trends were strongly 

decreasing except for Palma Sola Bay which had a slightly increasing trend, and Sarasota Bay which 

had a very slight decreasing trend. Chlorophyll a trends decreased in all five segments. 

Seasonality also varied by parameter. Salinity seasonal variation was largest in Roberts and Little 

Sarasota Bays, moderate in Sarasota and Blackburn Bays, and lowest in Palma Sola Bay. TN 

showed a strong to moderate seasonal variation in all segments. TP seasonality was evident but 

much more muted that TN. Chlorophyll a seasonality was the most distinct, with large differences 

in wet/summer and dry/winter concentrations in all segments. Palma Sola Bay showed the least 

difference. 
32 

V. Characterization of Nutrient Loadings to the Sarasota Bay Estuary Segments 

This section provides a brief summary of the model used to develop hydrologic and nutrient 

loading estimates for each segment within the SBEP area and a discussion of the temporal trends in 

these loadings. 

V-1.   Nutrient Loading Estimates for Sarasota Bay 

Nutrient and hydrologic loads were estimated for the period 1988-2008 for five bay segments 

within the greater Sarasota Bay watershed (from north to south): Palma Sola Bay, Sarasota Bay, 

Roberts Bay, Little Sarasota Bay and Blackburn Bay (Figure III-1). Drainage basins for each bay 

segment were delineated based on drainage boundaries provided by Manatee and Sarasota 

counties and are the same basins used to develop loading estimates for Roberts Bay for the time 

period 1994-2008 (2009 RBay WMP). Nutrient loading estimates were derived for each of the 114 

drainage basins using the Spatially Integrated Model for Pollutant Loading Estimates (SIMPLE) which 

was designed and calibrated by Jones Edmunds & Associates, Inc (JEA 2009 SIMPLE design report). 

The SIMPLE model consists of six modules that produce pollutant loading estimates for the primary 

point and non-point sources within a watershed: 1) Direct Runoff, 2) Baseflow, 3) Irrigation, 4) 

Point Source, 5) Septic Tanks, and 6) Atmospheric Deposition. We used the SIMPLE model to 

estimate nutrient loads for the first five sources, but calculated atmospheric deposition externally 

(see below for more detail). Nutrient loads from the SIMPLE model were combined with loads 

from atmospheric deposition to estimate Total Nutrient Loads to each bay segment. 

Rainwater runoff and groundwater flow, both tightly coupled to precipitation, are the primary 

mechanisms by which nutrients are transported from the watershed to Sarasota Bay. In order to 

estimate nonpoint source nutrient loads related to these hydrologic processes, the Direct Runoff 

and Baseflow modules reference an externally generated table of monthly hydrologic values that 

estimate rainfall, runoff and baseflow for all combinations of land use and soil type in the Sarasota 

Bay watershed. Below, we describe the external hydrologic engine that estimates these hydrologic 

values. Then, we briefly outline the modules that estimate nutrient loads from runoff and baseflow. 

Finally, we outline the modules that estimate non-point source contributions from irrigation and 

point source contributions from wastewater treatment facilities and septic tanks. 

V-1.1 Estimation of Hydrologic Values 

The hydrologic engine used to estimate rainfall, runoff and baseflow was provided by Jones 

Edmunds and Associates, Inc. (JEA) as a continuous simulation spreadsheet model and was recoded 

to run using the Statistical Analysis Software package (SAS version 9.2). Parameter estimates 

derived from the original spreadsheet model, which was run by JEA for Sarasota County (1994-

2008), were compared with estimates derived from the recoded SAS engine to ensure identical 

model outputs prior to estimating hydrologic parameters for the pre-NEXRAD time period and for 

the Manatee County portion of the Sarasota Bay watershed. 

Precipitation and evapotranspiration data were the inputs required to run the hydrologic engine. 

Monthly rainfall estimates were made using NEXRAD rainfall data for 1994-2008 and data from 

SWFWMD and National Weather Service rain gauges for the pre-NEXRAD period from 1989-1993. 

Rainfall for the pre-NEXRAD period was estimated for each 2km x 2km NEXRAD pixel using the 

inverse-distance squared method to interpolate rainfall between gauges. Losses of water to 
33 

evapotranspiration were modeled as a function of water table level, soil moisture, and land use 

with potential evapotranspiration data provided by the U.S. Geological Survey. 

Runoff and baseflow were estimated on a daily time-step for each combination of NEXRAD pixel, 

land use and soil type and were then summed to obtain monthly values. Runoff estimates were 

based on those of the Natural Resource Conservation Service (NRCS, 1986) and accounted for 

antecedent moisture conditions as well as differences in runoff volume from pervious and 

impervious surfaces, and as a result of changes in soil saturation as a function of rainfall. Baseflow 

was calculated using the Dupuit-Forcheimer equation which is a function of the horizontal and 

vertical distances travelled by groundwater and hydraulic conductivity for each soil type. 

Estimates of monthly rainfall, runoff and groundwater were produced by the hydrologic engine and 

exported to a geodatabase table that was referenced by the Direct Runoff and Baseflow modules 

during execution of the SIMPLE model. 

V-1.2 Direct Runoff 

Monthly nutrient loads (lbs/month) and hydrologic loads (ft3

/month) from runoff were estimated for 

each drainage basin. Runoff volumes and nutrient concentrations were a function of the relative 

proportions of each land use and hydrologic soil type within each basin and were adjusted for land 

use changes over time using a time-stamped land use coverage for Sarasota county provided by 

JEA. The time-stamped land use coverage for Manatee county was created following the same 

procedure used to create the Sarasota coverage. Briefly, each land use polygon was time-stamped 

by intersecting historic (1990) and current (2004 for Sarasota county, 2007 for Manatee county) 

land use coverages obtained from the Southwest Florida Water Management District and then 

intersecting the resulting coverage with the parcel database retrieved from Manatee and Sarasota 

county Property Appraisers to create a land use coverage that described historic and current land 

uses and the year in which land uses changed over time. The soil coverage was retrieved from the 

USDA’s Natural Resources Conservation Service. The spatial coverage for lands treated by best 

management practices (BMPs) was created for Manatee County by subsetting from the land use 

coverage all polygons classified as reservoirs, golf courses, open lands, and medium/high-density 

residential lands and lands permitted by SWFWMD’s Environmental Resource Permit. SWFWMD 

aerial photography from 2008 was used to identify and digitize any additional BMPs. All BMPs 

were considered to be wet detention for the purposes of estimating pollutant removal efficiencies. 

V-1.3 Baseflow 

As with runoff, nutrient loads (lbs/month) and hydrologic loads (ft3

/month) from baseflow were 

estimated for each drainage basin as a function of land use and soil type within the basin. Event 

mean concentrations for baseflow were held constant across land uses and soil types and were 

derived from literature values and used previously in other southwest Florida estuaries.

V-1.4 Irrigation 

The spatial coverage for irrigated lands in Manatee County consisted of residential, commercial and 

agricultural lands, and golf courses. The source of irrigated water was assumed to be groundwater 

unless otherwise indicated by the coverage of areas with access to reuse water as provided by the 

Counties. Irrigation rate was assigned for lands in both Sarasota and Manatee Counties using a 

relationship between average parcel age and market value and was calibrated through field 

observations of lawn health by Jones-Edmunds. Healthier lawns on golf courses and residential 
34 

lands were assumed to receive a higher rate of irrigation than less healthy lawns. Medium 

irrigation rates were assumed for agricultural lands. Nutrient loads from irrigation were corrected 

for irrigation of impervious areas and infiltration to groundwater so as not to overestimate irrigation 

loadings. 

V-1.5 Point Sources 

Daily water quality data including nutrient concentrations and flows were obtained from Florida 

Department of Environmental Protection, Sarasota County and Manatee County for the major point 

sources (> 0.1 MGD) for the model period, including 1989-1993 and 2008 to expand the existing 

water quality dataset for Sarasota County provided by Jones-Edmunds. Smaller non-delegated 

facilities treating <0.05 MGD were included in Sarasota County dataset but were not obtained for 

Manatee County. When data were not available for a given time period, monthly averages were 

calculated using existing data for that point source. Improvements to the existing dataset were 

made by replacing previously averaged values with newly acquired data for the major point sources 

and by correcting total effluent volumes for the City of Sarasota plant to account for surface water 

discharge as well as reuse. The only major point source in Manatee County, the Southwest 

Wastewater Treatment Plant, was converted to advanced wastewater treatment prior to 1989 with 

effluent being disposed via deep injection well and into the reuse system rather than being 

discharged directly to surface waters. Therefore, flows for this point source were considered to be 0 

MGD. 

Non-compliant effluent (i.e., sewage spills, reuse spills) was accounted for in the point source 

module by referencing tables containing information on the location, volume and concentrations of 

non-compliant spills. Spill data were obtained from Manatee and Sarasota Counties. 

V-1.6 Septic Tanks 

The spatial coverage for septic tanks throughout the bayshed was estimated by first assigning points 

representing septic tanks to each developed parcel and then by removing points from parcels that 

intersected the central sewer coverage provided by the Counties. A concentration of low, medium 

or high corresponding to literature values was then assigned to each septic tank based on the 

hydrologic soil group, presence or absence of BMPs and distance from each tank to the nearest 

surface water as estimated using GIS. Failure rate was assigned as a percentage of tanks based on 

hydrologic soil group and tank age. 

V-1.7 Atmospheric Deposition 

Total atmospheric deposition is defined as the sum of wet deposition (rainfall) and dry deposition 

(gaseous constituent interaction and dust fallout) directly to the surface of the bay. Deposition of 

pollutants to the watershed of the bay is incorporated into nonpoint source loading estimates. 

Three types of data were used to estimate total atmospheric deposition: 

 an estimate of the hydrologic load directly to the surface of the bay via precipitation; 

 an estimate of the pollutant concentration in that precipitation; and 

 an estimate of dry deposition, either from empirical data or model-based estimates. 
35 

Precipitation-derived hydrologic loads to the bay surface were estimated as the total monthly 

rainfall using the rainfall dataset used to generate hydrologic loads to the watershed (described 

above). 

Mean monthly pollutant concentrations for total nitrogen (TN) in rainfall were obtained from the 

National Atmospheric Deposition Program (NADP) Verna Wellfield site in Sarasota County. This 

site represents the nearest long-term site measuring precipitation concentration data. TN loadings 

from precipitation were estimated by multiplying the monthly precipitation-weighted mean TN 

concentrations from the Verna site and the monthly bay surface hydrologic loads to estimate 

monthly wet TN loads to the bay. Estimates of wet deposition for nitrogen were calculated as 

follows:

 Nwetm=[N]m * Hm, 

 Nwetm = wet deposition of nitrogen (kg/month) for each month m, 

 

 [N]m= mean precipitation-weighted nitrogen concentration (g/m3

) in the rainfall 

measured at the Verna Wellfield for each month m, and 

 Hm= estimated hydrologic load (m3

/month) from rainfall for each month m to the 

bay surface. 

Concentrations for total phosphorus (TP) in rainfall were unavailable from the Verna site and had to 

be estimated from a relationship between rainfall concentrations of nitrogen and phosphorus which 

were based on data collected by the Tampa Bay Atmospheric Deposition Study (TBADS) were 

utilized (Poor, 2000). This program, running from 1996 to 2006, included sampling elements for 

both wet and dry deposition at an intensive monitoring site located on the Gandy Bridge 

Causeway. The data available from TBADS include concentrations for nitrogen and phosphorus, 

wet and dry deposition rates, and an estimate of the ratio of dry:wet deposition, and have been 

used to estimate atmospheric deposition to Tampa Bay (Pribble et al., 2001). 

Estimates of dry deposition for both nitrogen and phosphorus were based on data collected at the 

TBADS site. Dry deposition was estimated using the TBADS-derived seasonal dry:wet deposition 

ratio, which was 1.05 for the dry season (months 1-6 and 11-12) and 0.66 for the wet season 

(months 7-10), as follows: 

 Ndrym= Seasonal Deposition Ratio * Nwetm, 

 Ndrym = dry deposition of nitrogen (kg/month) for each month m, and 

 Nwetm = wet deposition of nitrogen (kg/month) for each month m. 

Total atmospheric deposition to a surface of the bay was given as the sum of the wet and dry 

deposition, as follows: 

 Ntotm= Nwetm + Ndrym, 

 Ntotm = total atmospheric deposition of nitrogen (kg/month) for each month m to the 

surface of the bay. 

 
36 

V-2. Temporal Trends in Hydrologic and Nutrient Loadings by Bay Segment 

Hydrologic and nutrient loads were estimated for the period 1989-2008 for five bay segments 

within the SBEP area (from north to south): Palma Sola Bay, Sarasota Bay, Roberts Bay, Little 

Sarasota Bay, and Blackburn Bay (Figure V-1). 

Figure V-1. - Sarasota Bay Estuary Program segments and their watersheds. 

The total annual hydrologic, TN, and TP loads to each bay segment are presented in Figure V-2 

through V-4 and are discussed in the following sections 
37 

Figure V-2. – Annual hydrologic loads by bay segment. BB=Blackburn Bay, 

LS=Little Sarasota Bay, PS=Palma Sola Bay, RB=Roberts Bay, SB=Sarasota Bay. 

Figure V-3. – Annual TN loadings by bay segment. BB=Blackburn Bay, LS=Little Sarasota Bay, 

PS=Palma Sola Bay, RB=Roberts Bay, SB=Sarasota Bay. 
38 

Figure V-4. – Annual TP loadings by bay segment. BB=Blackburn Bay, LS=Little Sarasota Bay, 

PS=Palma Sola Bay, RB=Roberts Bay, SB=Sarasota Bay. 

Table V-1 presents the relative contribution to the recent (2008) loads to each bay segment. The 

contributions from direct runoff and base flow exceed 50% for each segment. Atmospheric 

deposition is relatively more important in Sarasota and Palma Sola bays, i.e., those segments with 

the greatest surface area. 

Table V-1. Relative contribution (%) for each load type to the 2008 loads to each bay segment. 

Load Type BB LSB PSB RB SB 

Atmospheric 

Deposition 4.0 15.6 20.4 2.3 31.7

Base Flow 21.9 25.0 19.4 27.6 15.3

Direct Runoff 59.8 56.0 49.5 59.2 42.5

Irrigation 1.7 2.3 2.3 2.5 1.3

Septic 12.6 1.1 8.4 4.1 4.3

Point Source 0.0 0.0 0.0 4.3 4.8

V-2.1 Palma Sola Bay 

The highest annual hydrologic loads to Palma Sola Bay were observed during wetter years 

(generally >55 inches) of 1992, 1995, and 2003 (Figure V-2). Drier years, in terms of total rainfall 

(<40 inches), occurred in 1990, 1999, 2000, and 2007 and corresponded to the lowest observed 

hydrologic loads during those years. As expected, the highest annual nutrient loadings for TN and 

TP were observed during years of peak hydrologic loads in 1988, 1992, 1995, 2003, and 2005 

(Figures V-3 and V-4). 

Box-and-whisker plots of the hydrologic and nutrient loadings for Palma Sola Bay are presented in 

Figures V-5-V-7. The bars represent the range of observations, while the upper and lower margins 

of the box indicate the 25th and 75th percentiles. The solid line is the median value and the dot is 
39 

the mean value. Mean hydrologic loads for Palma Sola Bay were highest during the wet season 

between June and October when average monthly loads ranged from 2.6 – 4.6 million cubic 

meters (Figure V-5). September had the highest average hydrologic loads in all bay segments, with 

October dropping sharply. During the dry season from November to May, average hydrologic 

loads to Palma Sola Bay ranged from 1.0 – 1.8 million cubic meters per month. For all bay 

segments, May had the lowest hydrologic loads. Interestingly, March consistently had the highest 

hydrologic loads observed during the dry season. As a rule, the average monthly hydrologic load 

to each of the bay segments during the wet season was 2.5 times greater than that during the dry 

season. 

Figure V-5. – Average monthly hydrologic loads to Palma Sola Bay (1989-2008). 

Average monthly loads for TN and TP were highest during the wet season (June-October) as 

expected from trends in rainfall and hydrologic loadings, and peaked in September (Figures V-6 and 

V-7). TN loads to Palma Sola ranged from 8.002 to 10,089 lbs/month between June-September and 

declined to 2,494 to 43,982 lbs/month during the dry season. TP loads displayed the same 

seasonal trends with the highest loads at 1,736 lbs in September at the end of the wet season and 

485 lbs in May at the end of the dry season. As with hydrologic loads, wet- season nutrient loads 

were consistently greater than dry-season loads for TN (2.5 X greater) and TP (2 X greater). 

Figure V-6. – Average monthly TN loads to Palma Sola Bay (1989-2008). 
40 

Figure V-7. – Average monthly TP loads to Palma Sola Bay (1989-2008). 

V-2.2 Sarasota Bay 

As with Palma Sola Bay, higher-than-average annual hydrologic loads to Sarasota Bay were 

observed during wetter years of 1992, 1995, and 2003, as well as 2005 (Figure V-2). Drier years 

occurred in 1990, 1999, 2000, and 2007 and corresponded to the lowest observed hydrologic 

loads during those years. The highest annual nutrient loadings for TN and TP were observed during 

years of peak hydrologic loads in 1992, 1995, 2003, and 2005 (Figures V-3 and V-4). Sarasota Bay 

also had noticeably higher than average TN in 1989 despite an average hydrologic load that year. 

Monthly hydrologic loads to Sarasota Bay were highest during the wet season between June and 

October when average loads ranged from 17.2 – 28.5 million cubic meters (Figure V-8). The 

highest hydrologic loads were observed in September. Average hydrologic loads were lowest to 

Sarasota Bay from November to May, with May consistently having the lowest monthly loads. Dry 

season loads ranged from 7.8 – 11.8 million cubic meters per month. Average monthly hydrologic 

loads during the wet season were 2.5 times greater than those during the dry season. 

Figure V-8. – Average monthly hydrologic loads to Sarasota Bay (1989-2008). 

Peak nutrient loads were observed between June-October with the highest monthly loads observed 

in September (Figures V-9 and V-10). Sarasota Bay received between 30,465 and 54,704 lbs 

TN/month between June-October but only one-third those amounts during the dry season, 14,180 

to 25,437 lbs/month. Sarasota Bay also received higher TP loads during the wet season peaking at 
41 

8,187 lbs/month, but only one-fourth the TP load during the dry season at 2,256 lbs/month in May. 

As with hydrologic loads, wet- season nutrient loads were consistently greater than dry-season loads 

for TN (2 times greater) and TP (2 times greater). 

Figure V-9. – Average monthly TN loads to Sarasota Bay (1989-2008). 

Figure V-10. – Average monthly TP loads to Sarasota Bay (1989-2008). 

V-2.3 Roberts Bay 

The highest annual hydrologic loads to Roberts Bay were observed during wetter years of 1992, 

1995, 2003, and 2005 (Figure V-2). Drier years occurred in 1990, 1999, 2000, and 2007 and 

corresponded to the lowest observed hydrologic loads during those years. The highest annual 

nutrient loadings for TN and TP were observed in 1992, 1995, 2003, and 2005 during years of 

peak hydrologic loads (Figures V-3 and V-4). Higher than average annual nutrient loads were also 

observed during 1997 for Roberts Bay. 

Mean hydrologic loads for Roberts Bay were highest between June and October when average 

monthly loads ranged between 12.3 – 19.7 million cubic meters (Figure V-11). September had the 

highest average hydrologic loads. The lowest hydrologic loads were observed between November 

and May when average loads to Roberts Bay ranged from 5.1 – 7.4 million cubic meters per month. 

As a rule, the average monthly hydrologic load to Roberts Bay during the wet season was 2.5 times 

greater than that during the dry season. 
42 

Figure V-11. – Average monthly hydrologic loads to Roberts Bay (1989-2008). 

TN and TP loads were also highest from June-October, peaking in September (Figures V-12 and V13). Roberts Bay received between 41,177 and 57,156 lbs TN/month between June-September 

while only one-third those amounts during the dry season, 15,622 to 21,585 lbs/month. Higher TP 

loads were observed for Roberts Bay during the wet season at 11,955 lbs/month compared to 4,620 

lbs/month during the dry season. As with hydrologic loads, wet- season nutrient loads were 

consistently 3X greater than dry-season loads for TN and TP. 

Figure V-12. – Average monthly TN loads to Roberts Bay (1989-2008). 
43 

Figure V-13. – Average monthly TP loads to Roberts Bay (1989-2008). 

V-2.4 Little Sarasota Bay 

Little Sarasota Bay received the highest annual hydrologic loads during 1992, 1995, 2003, and 

2005 (Figure V-2). The highest TN and TP loads were observed during the same years (Figures V-3 

and V-4). Lowest hydrologic loads occurred in 1990, 1999, 2000, and 2007. 

Mean hydrologic loads for Little Sarasota Bay were highest between June and October when 

average monthly loads ranged from 3.0 – 5.0 million cubic meters (Figure V-14). The highest loads 

occurred in September and dropped off in October at the end of the wet season. Between 

November and May, average hydrologic loads to Little Sarasota Bays ranged from 1.3 – 1.9 million 

cubic meters per month, with May having the lowest hydrologic loads. The average monthly 

hydrologic load to Little Sarasota Bay was 2.5 times greater during the wet season than during the 

dry season. 

Figure V-14. – Average monthly hydrologic loads to Little Sarasota Bay (1989-2008). 
44 

Average monthly loads for TN and TP (Figure V-15 and V-16) were highest during the wet season 

(June-October) as expected from trends in rainfall and hydrologic loadings, and peaked in 

September and TN loads to Little Sarasota Bay ranged from 6,253 to 11,380 lbs/month between 

June-September and dropped to 3,013 to 4,408 lbs/month during the dry season. Monthly TP 

averages during the wet season were between 1,260 and 1,948 lbs/month, but dropped to between 

561 and 805 lbs/month during the dry season. Average wet- season nutrient loads were 

consistently greater than dry-season loads for TN (2.5 times greater) and TP (2 times greater).

Figure V-15. – Average monthly TN loads to Little Sarasota Bay (1989-2008). 

Figure V-16. – Average monthly TP loads to Little Sarasota Bay (1989-2008). 

V-2.5 Blackburn Bay 

Blackburn Bay received the highest annual hydrologic loads during 1992, 1995, 2003, and 2005 

(Figure V-2). As was the case throughout the greater Sarasota Bay watershed, the lowest hydrologic 

loads to Blackburn Bay were observed in 1990, 1999, 2000, and 2007. The highest annual 

loadings for TN and TP were observed in 1992, 1995, 2003, and 2005 (Figures V-3 and V-4). 

Higher than average annual nutrient loads were also observed during 1997 for Blackburn Bay. 

As was true for all bay segments within the Sarasota Bay watershed, Blackburn Bay experienced the 

highest monthly hydrologic loads during the wet season between June and October when loads 
45 

were between 3.1 – 5.1 million cubic meters (Figure V-17). Hydrologic loads were highest in 

September averaging 5.1 million cubic meters. The lowest monthly hydrologic loads were 

observed in May during the end of the dry season (November to May) when average hydrologic 

loads to Blackburn Bay ranged from 1.1 – 1.9 million cubic meters per month. Average hydrologic 

loads to Blackburn Bay during the wet season were 2.5 times greater than that during the dry 

season. 

Figure V-17. – Average monthly hydrologic loads to Blackburn Bay (1989-2008). 

The highest average monthly nutrient loads were observed during the wet season from JuneOctober, with a peak loading in September, corresponding to higher than average hydrologic 

loadings during those months (Figures V-18 and V-19). TN loads to Blackburn Bay ranged from 

11,699 to 15,048 lbs/month between June-September and dropped to between 2,782 to 5,008 

lbs/month during the dry season. TP loads were also highest in September at 2,406 lbs/month and 

lowest in May at 592 lbs/month. As with hydrologic loads, wet- season nutrient loads were 

consistently greater than dry-season loads for TN (2.5 times greater) and TP (2 times greater). 

Figure V-18. – Average monthly TN loads to Blackburn Bay (1989-2008). 
46 

Figure V-19. – Average monthly TP loads to Blackburn Bay (1989-2008). 

V-3. Temporal Trends in Residence Times by Bay Segment 

A box model was developed to estimate the hydraulic residence times within the SBEP segments. 

The box model was based on observed salinity distributions within the system and estimated 

freshwater inflows from the SIMPLE model to the system. Methods were similar to those described 

by Hagy et al. (2000), with the exception that the SBEP system was assumed to be well mixed 

vertically, so that all transport was horizontal. Hydraulic residence time is also named the pulse 

residence time (PRT), as residence times are dependent upon introducing a pulse of tracer into a 

selected segment at the beginning of the box model simulation and tracking the time necessary for 

the concentration of this tracer to decrease to a certain level. 

The specific method used to estimate the pulse residence times for each segment is given in 

Appendix 4. 

The box model iterations resulted in segment- and monthly-specific estimates of PRT. For each 

segment, the median PRT for each year was calculated, and then the median PRT of the annual 

values for each segment were calculated. These segment-specific PRTs are provided in Table V-2, 

and represent the median hydraulic residence time within each segment given the observed 

conditions of 1994-2007. 

Table V-2. Median annual pulse residence time for each segment based 

on 1994-2007 conditions. 

Segment Pulse Residence Time (days) 

Palma Sola Bay 35.8 

Sarasota Bay 28.8 

Roberts Bay 2.8 

Little Sarasota Bay 19.2 

Blackburn Bay 3.0 

A time series plot of the annual PRTs for each segment for the 1994-2007 period is provided in 

Figure V-20. As show in Table V-2, the PRTs are in units of days, so that a shorter PRT indicates 

more rapid exchange between the segment and the Gulf, and a longer PRT indicates slower 
47 

exchange. Not surprisingly, the smaller segments with large freshwater inflows relative to the 

segment size (Roberts Bay, Blackburn Bay) have much shorter residence times (on the order of 10 

times shorter) than do those with smaller inflows and relatively larger segment volumes (Sarasota 

Bay, Little Sarasota Bay). As can be seen from Figure V-20, the interannual variability in PRT is 

small for all segments, with only about 10% variability in PRT in those segments with longer 

residence times, and almost no variability in PRT in those segments with shorter residence times. 

 

Figure V-20. Median annual PRTs (days) for each segment, based on monthly PRTs for each years. 
48

VI. Relationships between Chlorophyll and Nutrient Loads and Concentrations 

The objective of this section is to present the methods and results obtained in the development of 

quantifiable relationships between chlorophyll a and nutrient loadings and/or concentrations for 

each bay segment in the SBEP area. A summary of the potential empirical approaches to establish 

NNC was recently completed for the three National Estuary Programs on the Florida Gulf Coast 

(Janicki Environmental, 2010b). 

In most estuarine ecosystems N is the most limiting nutrient (a nutrient whose concentration in the 

environment of an organism determines the growth and productivity of that organism) (Boynton et., 

1982; Howarth, 1988; Chapra, 1997; National Research Council, 2000; Pennock et al., 2000). 

Aquatic ecosystems are commonly characterized by their N:P ratios. Receiving waters with ratios 

less than 10:1 are considered nitrogen limited, while ratios higher than 10:1 are assumed to be 

phosphorus limited (FDEP, 2000). In Sarasota Bay, ratios between total nitrogen (TN) and total 

phosphorus (TP) are typically well below 10 (Lowrey, 1992), which is consistent with presumed 

nitrogen limitation. In Roberts Bay, FDEP (2005) calculated a median TN:TP ratio of 2.4, indicating 

strong nitrogen limitation of phytoplankton growth. In addition, empirically derived relationships 

also point to the primary role of nitrogen in the eutrophication processes in Sarasota Bay (i.e., 

Tomasko et al. 1992 and 1996), as was found in the earliest studies in Tampa Bay (i.e., Johansson 

1991). More recent assessments also support the finding of nitrogen-limitation of macroalgae in 

Sarasota Bay (Dillon and Chanton, 2008). 

VI-1 Data Sources 

The water quality data used in these analyses are described in Section IV. The estimates of 

hydrologic, TN, and TP loadings used are described in Section V. Residence times used in these 

analyses are also described in Section V. 

VI-2 Analytical Approach 

A linear regression approach was used to develop statistically defensible relationships. Linear 

regression is a parametric statistical technique that is used to explore the relationship between two 

or more variables. In ordinary least-squares regression, the relationship between the dependent 

variable (y-axis) and independent variable (x-axis) is developed. This is done by fitting a straight 

line through the set of points such that the sum of squared residuals of the model is as small as 

possible. That is to say, the vertical distances between the individual points and the fitted line are 

minimized. 

In linear regression, it is assumed that the data are independent samples from the population that is 

being sampled. For example, the data should come from samples that are representative of the 

spatial and temporal variability of the system. Another important assumption of linear regression is 

that the error term of the model is normally distributed, with constant variance. Often times, one or 

more of the variables exhibits a non-linear relationship with the other variables. While there are 

non-linear regression techniques that can be employed, one should attempt to transform the data 

before resorting to nonlinear methods. Often, linear relationships can be developed using 

transformed data and these models will satisfy the assumptions of linear regression. 
49

The stepwise regression procedure (SAS 9.2, 2010) was used to identify the independent variables 

that have a significant relationship with chlorophyll a. In the stepwise procedure, the independent 

variables are added to the model one at a time and the F statistic for the variable must be significant 

in order for the variable to be included in the model. Unlike the forward procedure which only 

adds additional variables to the model, the stepwise procedure examines the F statistic for all 

variables already included in the model after each step. Variables that are no longer significant 

based on the F statistic are removed. The result is a ranked list of significantly contributing 

variables. 

Diagnostic statistics and plots are commonly used to determine if the regression model meets the 

assumptions of linear regression. The most commonly used statistics are the statistical significance 

of the model parameters and the coefficient of determination (R2

). The statistical significance of the 

model parameters tests whether the slope and intercept of the model are significantly different from 

zero. The coefficient of determination is a measure of the variance in the dependent variable that is 

explained by the model. A plot of the residuals versus the independent variable can be used to 

judge if the assumption of constant variance is met. Additional plots of residuals versus other 

variables can also be instructive. For example, a time-series plot of the residuals can be used to 

assess whether or not the residuals vary seasonally. Additional diagnostics can be run to identify 

outliers and test for leverage or influential points. Data points that are identified by these additional 

diagnostics should be further investigated to determine if they are the result of a data entry error or 

other problems that merit removing them from the analysis. 

The independent variables used in the model building process included loadings, concentrations, 

and estimates of residence time. The loadings data included monthly hydrologic, TN, and TP loads 

as well as cumulative total loads extending from two to six months (e.g., 2-month cumulative TN 

load = TN load current month + TN load one- month prior). The water quality constituents 

included TN and TP concentrations along with numerous other constituents. The results of the 

analyses for each segment are presented below. 

VI-3 Roberts Bay 

A series of bivariate plots were examined to investigate relationships between chlorophyll a and 

other potential explanatory variables. TN concentration was identified as the variable that makes 

that greatest contribution to explaining the variability in chlorophyll a concentrations in Roberts 

Bay. As can be seen in Figure VI-1, there is a pattern of increasing chlorophyll a concentrations 

with increasing TN concentrations. 
50

Figure VI-1. Relationship between monthly average chlorophyll a and TN concentrations 

in Roberts Bay. 

A regression model between chlorophyll a and TN concentrations was developed and the residuals 

from this model were examined to identify any other explanatory variables that might contribute to 

the overall variance accounted for by the model. The residual analysis revealed a seasonal 

difference in residuals. Specifically, given the same TN concentrations, higher chlorophyll a 

concentrations can be expected during the wetter, warmer summer months (July-October) than 

during the remainder of the year. Therefore, a seasonal term was added to the regression equation. 

The season term is a dummy variable which equals one during July-October and zero other months 

of the year. The final regression equation is: 

[Chlorophyll a] = -5.73 + (27.07 * [TN]) + (3.41 * season) 

The model was fit with 133 observations and resulted in an R2 value of 0.62. The regression was 

highly significant with a probability of a greater |F| value of < 0.0001. The slope and parameter 

coefficients were also highly significant. A plot of predicted versus observed chlorophyll a

concentrations is presented in Figure VI-2. The fit is generally good with some overestimation at 

low concentrations and underestimation at hogher levels. Residual plots for the Roberts Bay 

chlorophyll a regression model are presented in Appendix 5. 

VI-4 Little Sarasota Bay 

A series of bivariate plots were examined to investigate relationships between chlorophyll a and 

other potential explanatory variables in Little Sarasota Bay. TN concentration was identified as the 

variable that makes that greatest contribution to explaining the variability in chlorophyll a

concentration. As can be seen in Figure VI-3 there is a pattern of increasing chlorophyll a

concentrations with increasing TN concentrations. 
51

Figure VI-2. Predicted versus observed chlorophyll a concentrations for Roberts Bay (R2=0.62). 

A regression model between chlorophyll a and TN concentrations was developed and the residuals 

from this model were examined to identify any other explanatory variables that might contribute to 

the overall variance accounted for by the model. As was found in Roberts Bay, the residual 

analysis revealed a seasonal difference in residuals. Specifically, given the same TN 

concentrations, chlorophyll a concentrations can be expected to be higher in Little Sarasota Bay 

during the wetter, warmer summer months (July-October) than during the remainder of the year. 

Therefore, a seasonal term was added to the regression equation. The season term is a dummy 

variable which equals one during July-October and zero other months of the year. The final 

regression equation is: 

[Chlorophyll a] = -4.48 + (21.59 * [TN]) + (2.97 * season) 

Figure VI-3. Relationship between monthly average chlorophyll a and TN concentrations 

in Little Sarasota Bay. 
52

The model was fit with 133 observations and resulted in an R2 value of 0.57. The regression was 

highly significant with a probability of a greater |F| value of < 0.0001. The slope and parameter 

coefficients were also highly significant. A plot of predicted versus observed chlorophyll a

concentrations is presented in Figure VI-4. Residual plots for the Little Sarasota Bay chlorophyll a

regression model are presented in Appendix 5. 

Figure VI-4. Predicted versus observed chlorophyll a concentrations in Little Sarasota Bay 

(R2

=0.57). 

VI-5 Blackburn Bay 

A series of bivariate plots were examined to investigate relationships between chlorophyll a and 

other potential explanatory variables. TN concentration was identified as the variable that makes 

that greatest contribution to explaining the variability in chlorophyll a concentration. As can be 

seen in Figure VI-5, there is a pattern of increasing chlorophyll a concentrations with increasing TN 

concentrations. 

A regression model between chlorophyll a and TN concentrations was developed and the residuals 

from this model were examined to identify any other explanatory variables that might contribute to 

the overall variance accounted for by the model. Similar to both Roberts Bay and Little Sarasota 

Bay, this analysis revealed a seasonal difference in residuals. Specifically, given the same TN 

concentrations, chlorophyll a concentrations can be expected to be higher in Blackburn Bay during 

the wetter, warmer summer months (July-October) than during the remainder of the year. 

Therefore, a seasonal term was added to the regression equation. The season term is a dummy 

variable which equals one during July-October and zero other months of the year. The final 

regression equation is: 

[Chlorophyll a] = -3.55 + (23.72 * [TN]) + (1.73 * season) 
53

Figure VI-5. Relationship between monthly average chlorophyll a and TN concentrations 

in Blackburn Bay. 

The model was fit with 133 observations and resulted in an R2 value of 0.73. The regression was 

highly significant with a probability of a greater |F| value of < 0.0001. The slope and parameter 

coefficients were also highly significant. A plot of predicted versus observed chlorophyll a

concentrations is presented in Figure VI-6. Residual plots for the Blackburn Bay chlorophyll a

regression model are presented in Appendix 5. 

Figure VI-6. Predicted versus observed chlorophyll a concentrations in Blackburn Bay (R2=0.73).

VI-6 Sarasota Bay 

In order to investigate potential relationships between chlorophyll a and explanatory variables in 

Sarasota Bay, a series of bivariate plots were examined. TN concentration was identified as the 
54

variable that makes the greatest contribution to explaining the variability in chlorophyll a

concentrations in Sarasota Bay. As expected, there is a pattern of increasing chlorophyll a

concentrations with increasing TN concentrations (Figure VI-7). As in the regressions developed for 

Roberts Bay, Little Sarasota Bay, and Blackburn Bay, initial efforts revealed a seasonal difference in 

residuals. This indicates that given the same TN concentration, higher chlorophyll a concentrations 

are expected during the summer months. Therefore, a seasonal term was added to the regression 

equation. The season term is a dummy variable which equals one during the wet season (JuneOctober) and zero other months of the year. 

Unlike Roberts Bay, Little Sarasota Bay, and Blackburn Bay, Sarasota Bay is a substantially larger 

system with greater spatial variability in TN concentrations. Specifically, TN concentrations in the 

northern portion of the bay (Figure VI-8) are greater than those in the southern portion (Table VI-1). 

In contrast, there is less spatial variability in the chlorophyll a concentrations. As a result, given the 

same TN concentrations, higher chlorophyll a concentrations are found in the southern portion of 

the bay. Therefore, a region term was added to the regression equation to account for the spatial 

differences in TN and chlorophyll a concentrations in Sarasota Bay. 

Further analysis of the residuals from the regression model revealed that color also 

contributed to explaining the variation in chlorophyll a and was added to the regression 

equation. The final regression equation obtained is: 

 [Chlorophyll a] = -1.06 + (3.58 * [TN]) + (0.32 * color) + (2.03 * season) – (4.84 * region)

Figure VI-7. Relationship between monthly average chlorophyll a and TN concentrations in 

Sarasota Bay. 
55

Figure VI-8. Northern and southern portions of the Sarasota Bay segment. 

Table VI-1. Comparison of water quality within Northern and Southern Sarasota Bay. Values 

represent medians for the period 1998-2009. 

Variable Northern Sarasota Bay Southern Sarasota Bay 

Chlorophyll a (μg/l) 5.2 3.4 

TN (mg/l) 0.56 0.28 

Color (PtCo units) 20 10 

The model was fit with 156 observations and resulted in an R2

 value of 0.67. The regression was 

highly significant with a probability of a greater |F| value of < 0.0001. The slope and parameter 

coefficients were also significant. A plot of predicted versus observed chlorophyll a concentrations 

is presented in Figure VI-8. Residual plots for the Sarasota Bay chlorophyll a regression model are 

presented in Appendix 5. 

Northern

Region
56

Figure VI-8. Predicted versus observed chlorophyll a concentrations in Sarasota Bay (R2=0.67).

VI-7 Palma Sola Bay 

A series of bivariate plots were examined to investigate relationships between chlorophyll a and 

other potential explanatory variables in Palma Sola Bay. Specifically, examination of the 

relationship between chlorophyll a concentrations and both TN concentrations and loads were 

examined. As can be seen in Figures VI-9 and VI-10, there is no apparent relationship between 

chlorophyll a concentrations and either TN concentrations or loads. A similar lack of relationships 

was found for TP concentrations and loads, as well as a series of cumulative loading. 

Figure VI-9. Relationship between monthly average chlorophyll a and TN 

concentrations in Palma Sola Bay. 
57

Figure VI-10. Relationship between monthly average chlorophyll a and TN 

loading in Palma Sola Bay. 

Several other analytical tools were applied to discern if a quantitative relationship between 

chlorophyll a concentrations and either TN concentrations or loads could be found. Specifically, 

various applications of both logistic regression techniques and changepoint analyses were 

investigated. 

Logistic regression was used to predict the probability of a chlorophyll a concentration greater than 

the threshold value of 11.8 μg/l for Palma Sola Bay as a function of TN concentration. A season 

term was incorporated to account for the differential effects of TN concentration on phytoplankton 

production depending on water temperature and photoperiod. One hundred and seventy-one 

observations were used in the regression and 49 chlorophyll exceedances (i.e., chlorophyll a > 

11.8 μg/l) occurred in the dataset. The resulting logistic regression equation was: 

( 1| )

( 1| )

( ) 2.1521 2.0486* 0.74*1( )

1

y x

y x

p LOG TN Wet

p





   

The model R2 was 0.24 and suggested that the odds of a value exceeding the threshold during the 

wet season was more than twice [i.e., e(0.74)] that of the dry season (Figure V-11). In order to use 

logistic regression for prediction, one must assign a probability cutpoint from which to define an 

exceedance. The SAS program (SAS, 2010) uses a jackknife routine to estimate the probability 

cutpoint that results in the highest predictive accuracy of the model and therefore confidence in 

“making the right call”. 

Applying this jackknife procedure to the TN and chlorophyll a concentration data for Palma Sola 

Bay identified a probability cutpoint of 0.45 which resulted in 76% classification success 

(sensitivity=47% and specificity=87%). Based on these results, a TN concentration that is 

predicted to result in a chlorophyll a concentration exceedance in the wet season is 0.57 mg/l and 

in the dry season 1.31 mg/l. Using these values and calculating a weighted mean TN 

concentration results in an annual average annual TN concentration of 1.06 mg/l. It is important to 
58

note that these estimates do not include uncertainty in the model estimates which may be 

substantial, therefore the results should be applied with a degree of caution. 

Figure V-11. Predicted probabilities of a chlorophyll a value greater than 11.8 in wet 

and dry season in Palma Sola Bay. Horizontal line indicates cutpoint probability for 

assigning a predicted value as an exceedance. 

Changepoint analysis was performed to identify a potential threshold TN value that was associated 

with a non-linear increase in chlorophyll a concentrations. Changepoint analysis performs an 

iterative search through the data sorted in increasing order of TN values to identify a “changepoint” 

in the relationship that maximizes the difference in chlorophyll concentrations between two groups 

of data. In this way a threshold value for TN is identified. No a priori threshold is specified. The 

decision tree approach defines the breakpoint as that which maximizes the difference by 

minimizing the p value associated with the F test. The point in the covariate (TN concentration) at 

which the p value is minimized, after adjustment for multiple comparisons, is assigned as the 

breakpoint defining the split of the chlorophyll data into 2 groups. Once the first split is made the 

process continues to test for subsequent splits that are conditional on the first split. This is called 

“conditional inference” or “conditional probability analysis” which has been popularized recently 

by the USEPA as a potential approach for establishing numeric nutrient criteria. 

For this analysis, the state threshold for chlorophyll-a in marine waters (11 μg/l) was used as a 

criterion value for evaluating the potential of the identified changepoint value of TN to serve as a 

potential numeric nutrient criterion. That is, if the identified changepoint resulted in a group of 

chlorophyll data with an average value above 11 μg/l then the TN changepoint was deemed as a 

potential value for numeric nutrient criterion development. 

The results of changepoint analysis for Palma Sola Bay is provided in Figure V-12. A statistically 

significant TN changepoint value of 0.756 mg/l was identified as the value that maximized the 

difference in the distribution of chlorophyll a concentrations between two groups. The average 
59

chlorophyll a concentration when TN concentrations were below 0.756 mg/l was 7.69 μg/l and 

the average chlorophyll a concentration when TN concentrations were above 0.756 g/l was 11.6 

μg/l. Since the average chlorophyll a concentration in the high TN group was above the state 

threshold, we consider this TN value to be potentially meaningful in allowing Palma Sola Bay to 

continue to meet its designated uses. 

Figure V-12. Results of changepoint analysis in Palma Sola Bay with distribution of chlorophyll a values 

displayed in boxplots and the TN changepoint identified as 0.75.

Mean Chlorophyll a

7.7 μg/l

Mean Chlorophyll a

11.6 μg/l

Palma Sola Bay

Decision Tree
60

VII. Recommended SBEP Numeric Nutrient Criteria 

We have applied the stressor-response relationships described in Section VI to estimate draft 

numeric nutrient criteria for each SBEP segment. The strategy for developing the numeric nutrient 

criteria is based on the chlorophyll a thresholds identified in Section III and the quantitative 

relationships between chlorophyll a and nutrients derived in Section VI. The following describes 

the approach used. 

VII-1 Roberts, Little Sarasota, and Blackburn Bays 

The stressor-response relationships for Roberts Bay, Little Sarasota Bay, and Blackburn Bay that 

were identified in Section VI indicated very similar responses in chlorophyll a concentrations to 

changes in nutrients. Specifically, two terms, TN concentration and season, explained more than 

60% of the variation in the chlorophyll a data. 

For each of these segments, the regression was used to estimate the TN concentrations that 

correspond to the chlorophyll a thresholds identified in Section III. This resulted in an estimated 

TN concentration for each season. The annual mean of the seasonally-specific TN concentrations 

was calculated by weighting for the number of months in each season. This weighted annual mean 

TN concentration is that TN concentration that corresponds to the chlorophyll a threshold 

concentration, and therefore is the proposed numeric nutrient criterion for each segment. 

Figures VII-1 – VII-3 present comparisons of the proposed numeric criteria for Roberts Bay, Little 

Sarasota Bay, and Blackburn Bay, expressed as an annual geometric mean TN concentration, to the 

recent ambient geometric mean TN concentrations measured in each segment. The geometric 

means are used to achieve consistency with the approach used by EPA in the proposed freshwater 

numeric nutrient criteria. 

Figure VII-1. Comparison of the proposed TN criterion to observed TN concentrations 

(expressed as geometric means) in Roberts Bay. 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

[TN] (mg/l)

Ambient [TN] (mg/l) [TN] Criterion (mg/l)

ROBERTS BAY
61

Figure VII-2. Comparison of the proposed TN criterion to observed TN concentrations 

(expressed as geometric means) in Little Sarasota Bay. 

Figure VII-3. Comparison of the proposed TN criterion to observed TN concentrations 

(expressed as geometric means) in Blackburn Bay. 

VII-2 Sarasota Bay 

As shown in Section VI, the relationship between chlorophyll a concentrations and nutrients in 

Sarasota were more complex than those observed in Roberts Bay, Little Sarasota Bay, or Blackburn 

Bay. This resulted from the spatial variability within Sarasota Bay and the influence of color on the 

relationship between chlorophyll a concentrations and TN concentrations in that segment. 

Therefore, application of the regression derived for Sarasota Bay to estimate the proposed numeric 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

[TN] (mg/l)

Ambient [TN] (mg/l) [TN] Criterion (mg/l)

LITTLE SARASOTA BAY

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

[TN] (mg/l)

Ambient [TN] (mg/l) [TN] Criterion (mg/l)

BLACKBURN BAY
62

nutrient criterion is more complex. Since color influences the relationship between chlorophyll a 

concentrations and TN concentrations, the TN concentration that corresponds to the threshold 

chlorophyll a concentrations for Sarasota Bay will vary from year-to-year depending upon the 

ambient color observed in a year. 

To estimate the TN concentration that corresponds to the threshold chlorophyll a concentrations for 

Sarasota Bay, the mean color for each region and season was calculated for a given year. This 

mean color was used to calculate the TN concentration for each region and season. The annual 

mean of these TN concentrations was calculated by weighting for the number of months in each 

season, as was done for Roberts Bay, Little Sarasota Bay, or Blackburn Bay. This weighted annual 

mean TN concentration is that TN concentration that corresponds to the chlorophyll a threshold 

concentration for a given year. These mean annual TN concentrations are the proposed numeric 

nutrient criterion for Sarasota Bay. 

Figures VII-4 presents a comparison of the proposed numeric criteria for Sarasota Bay expressed as 

an annual mean TN concentration, to the recent ambient geometric mean TN concentrations 

measured in Sarasota Bay. 

Figure VII-4. Comparison of the proposed TN criterion to observed TN concentrations 

(expressed as geometric means) in Sarasota Bay. 

VII-3 Palma Sola Bay 

No significant quantitative relationship was found between chlorophyll a concentrations and either 

the TN or TP concentrations or loadings in Palma Sola Bay. Therefore, the approach to derive a 

numeric nutrient criterion for Palma Sola Bay will necessarily differ from that used for the other 

SBEP segments. 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

[TN] (mg/l)

Ambient [TN] (mg/l) [TN] Criterion (mg/l)

SARASOTA BAY
63

The SBEP water quality subcommittee of the TAC considered three potential candidate methods for 

estimating the TN criterion for Palma Sola Bay: 

 The logistic regression results suggested wet and dry season TN concentrations of 0.57 mg/l 

and 1.31 mg/l, respectively. The annual mean, weighting for season, gives a result of 1.06 

mg/l as a candidate TN criterion. Note that the logistic model fit was weak – r2

=0.25. 

 The changepoint analysis identified a breakpoint in the TN concentrations of approximately 

0.76 mg/l. 

 Following the logic used by the subcommittee to establish chlorophyll a concentrations for 

the SBEP segments 

- the mean TN concentration for the 2001-2005 period was 0.74 mg/l 

- the standard deviation of the annual mean TN concentrations for the period of 

record was 0.19 mg/l 

- therefore, this method results in a candidate TN criterion of 0.93 mg/l. 

All three potential candidate methods give relatively similar results. 

The subcommittee recommended the third option – i.e., that based on the 2001-2005 ambient TN 

data. The full TAC concurred with the subcommittee’s recommendation on 23 July 2010. 

Figures VII-5 presents a comparison of the proposed numeric criteria for Palma Sola Bay expressed 

as an annual mean TN concentration, to the recent ambient geometric mean TN concentrations 

measured in Palma Sola Bay. 

Figure VII-5. Comparison of the proposed TN criterion to observed TN concentrations 

(expressed as geometric means) in Palma Sola Bay. 

0

0.2

0.4

0.6

0.8

1

1.2

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

[TN] (mg/l)

Ambient [TN] (mg/l) [TN] Criterion (mg/l)
64

References 

Boynton, W.R., W.M. Kemp, and C.W. Keefe. 1982. A comparative analysis of nutrients and other 

factors influencing estuarine phytoplankton, p. 69-90. In: V.S. Kennedy (ed.), Estuarine 

Comparisons. Academic Press, New York. 

Chapra, S. C. 1997. Surface Water-Quality Modeling. WCB McGraw-Hill, Boston 

Massachusetts. 843p. 

Dillon, K.S. and J.P. Chanton. 2008. Nitrogen stable isotopes of macrophytes assess stormwater 

nitrogen inputs to an urbanized estuary. Estuaries and Coasts. 31: 360-370. 

Florida Department of Environmental Protection (FDEP). 2005. Nutrient TMDL for Roberts Bay 

(WBID 1968D). Florida Department of Environmental Protection, Tallahassee, FL. 55 pp. 

Florida Department of Environmental Protection (FDEP). 2000. Memorandum: Updated Guidance 

on Implementation of the Grizzle-Figg Legislation (Section 403.086,Florida Statutes). 5p. 

Hagy, James D., Lawrence P. Sanford, and Walter R. Boynton. 2000. Estimation of Net Physical 

Transport and Hydraulic Residence Times for a Coastal Plain Estuary Using Box Models. Estuaries. 

23:328-340. 

Hirsch, R.M., J.R. Slack, and R.A. Smith. 1982. Techniques of trend analysis for onthly water 

quality data. Water Resources Research. 18:107-121. 

Hirsch, R.M. and J.R. Slack. 1984. A nonparametric trend test for seasonal data with serial 

dependence. Water Resources Research. 20:727-732. 

Howarth, R.W. 1988. Nutrient Limitation of Net Primary Productivity in Marine Ecosystems. 

Annual Review of Ecology and Systematics. 19:89-110. 

Janicki, A., M. Dema, R. Nijbroek. 2009. Seagrass Targets for the Sarasota Bay Estuary Program. 

Prepared for the Sarasota Bay Estuary Program. Prepared by Janicki Environmental, Inc. 

Janicki Environmental, Inc. 2010a. Chlorophyll Endpoints to Support the Development of Numeric 

Nutrient Criteria for the Sarasota Bay Estuary Program. Prepared for the Sarasota Bay Estuary 

Program. 

 

Janicki Environmental, Inc. 2010b. Empirical Approaches to Establishing Numeric Nutrient Criteria 

for Southwest Florida Estuaries. Prepared for the Tampa Bay Estuary Program, Sarasota Bay Estuary 

Program, and Charlotte Harbor National Estuary Program. 

Jones Edmunds & Associates. 2009. Sarasota County Pollutant Loading Model Development 

(W552) SIMPLE-Monthly Design Report. Prepared for Sarasota County and Southwest Florida 

Water Management District. 49pp. 
65

Lowrey, S. 1992. Physical and chemical properties – Bay water and sediment quality. pp. 4.1 – 

4.20, In: (P.Roat, C. Ciccolella, H. Smith, and D. Tomasko, eds.). Sarasota Bay: Framework for 

Action. Sarasota Bay National Estuary Program, Sarasota, FL. 

Natural Resources Conservation Service. 1986. Technical Release 55: Urban Hydrology for Small 

Watersheds. U.S. Department of Agriculture. 

National Research Council, 2000. Clean Coastal Waters: Underdstanding and Reducing the Effects 

of Nutrient Pollution. National Academy Press, Washington, DC. 

Pennock, J.R., J.N. Boyer, J.A. Herrera-Silveira, R.I. Iverson, T.E. Whitledge, B. Mortazavi, F.A. 

Comin. 1999. Nutrient behavior and phytoplankton production in Gulf of Mexico estuaries. In: 

Biogeochemistry of Gulf of Mexico Estuaries. Eds. T.S Bianchi, J.R. Pennock, and R.R. Twilley. 

John Wiley & Sons. 

Poor, N. 2000. Tampa Bay Atmospheric Deposition Study (TBADS) Final Interim Report: June 

2000. Tampa Bay Estuary Program Technical Publication #06-00. 

Pribble, J.R. , D.L. Wade, A.J. Janicki, A.P. Squires, H. Zarbock, R. Montgomery and G. Morrison. 

1997. Empirical and mechanistic approaches to establishing pollutant load reduction goals in the 

tidal Peace and Myakka rivers. Final report to the Southwest Florida Water Management District. 

Pribble, R., A. Janicki, H. Zarbock, S. Janicki, and M. Winowitch. 2001. Estimates of Total 

Nitrogen, Total Phosphorus, Total Suspended Solids, and Biochemical Oxygen Demand Loadings 

to Tampa Bay, Florida: 1995-1998. Prepared by Janicki Environmental. Prepared for Tampa Bay 

Estuary Program. Tampa Bay Estuary Program Technical Publication #05-01. 

Sarasota Bay Estuary Program (SBEP). 2010. State of the Bay. Prepared by Sarasota Bay Estuary 

Program. 

SAS 9.2 (TS2M3). 2010. SAS Institute, Inc. Cary, North Carolina. 

Tomasko, D., Alderson, M. Clark, P. Culter, J., Dixon, K., Edwards, R., Estevez, E., Heyl, M., 

Lowrey, S., Sheng, P., and J. Stevely. 1992. Technical synthesis of Sarasota Bay. Pp. 14.1-14.16. In: 

(P.Roat, C. Ciccolella, H. Smith, and D. Tomasko, eds.). Sarasota Bay: Framework for Action. 

Sarasota Bay National Estuary Program, Sarasota, FL. 

 

Tomasko, D.A., Dawes, C.J., 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., Corbett, C.A., Greening, H.S., and G.E. Raulerson. 2005. Spatial and temporal 

variation in seagrass coverage in Southwest Florida: assessing the relative effects of anthropogenic 

nutrient load reductions and rainfall in four contiguous estuaries. Marine Pollution Bulletin. 50: 

797-805. 
Appendix 1. 

Sarasota Bay Estuary Program 

Comments on EPA Proposed Freshwater 

Numeric Nutrient Criteria 
Sarasota Bay Estuary Program (SBEP) response to the EPA’s Proposed Water Quality 

Standards for the State of Florida’s Lakes and Flowing Waters and Methodology for 

Deriving Downstream Protection Values for Sarasota Bay, FL 

These comments are provided for EPA’s review and use in developing the Sarasota Bay Estuary 

Program’s (SBEP) numeric nutrient criteria for Sarasota Bay. Additional comments and 

recommendations will be provided through the Florida Department of Environmental Protection 

(FDEP) in June 2010. 

Background

Sarasota Bay is a fifty mile long coastal lagoon on the southwest coast of Florida (Figure 1). It is 

comprised of one large bay segment (Big Sarasota Bay) and several smaller embayments 

including Palma Sola Bay in the north and a series of three contiguous embayments (Roberts 

Bay, Little Sarasota Bay, and Blackburn Bay) to the south. The Bay has four inlets or passes 

(Venice Inlet, Big Sarasota Pass, New Pass and Longboat Pass). The SBEP area is bounded to 

the north by Anna Maria Sound, which opens into Tampa Bay and to the south by Venice Inlet. 

There are numerous, small tidal creeks that enter the bay along the eastern shoreline, ranging in 

size from the largest (Phillippi Creek: drainage area of 36,417 acres) to the smallest (Palma Sola 

Creek: drainage area of 900 acres). The watershed is highly developed and consists of 

agricultural, residential, commercial and light industrial land uses. 

Circulation is primarily driven by tidal exchange with the Gulf of Mexico. Big Sarasota Bay 

circulation is forced by the tides at Anna Maria Sound, Longboat Pass, New Pass and Big Pass. 

Tidal circulation in Little Sarasota Bay is forced by tides at Venice Inlet and the Intracoastal 

Waterway running through the middle of the bay. The closing of Midnight Pass in Little 

Sarasota Bay in 1983 permanently altered the circulation in the three lower embayments. 

History of Nutrient Management in Sarasota Bay

Sarasota Bay was named an “Estuary of National Significance” in the Water Quality Act of 1987 

and was formally designated as a National Estuary Program (NEP) in 1989. The Program’s 

Comprehensive Conservation and Management Plan (CCMP), which provides specific actions to 

be implemented by the community to reduce pollutants (including nutrients) and restore lost 

habitat, was signed in 1995. In 2004, the SBEP became an independent State Agency with 

authority to oversee water quality management and protection. 

Sarasota Bay is a nitrogen limited system (Lowrey, 1992; FDEP, 2005). Ratios between total 

nitrogen (TN) and total phosphorus (TP) in Sarasota Bay are typically well below 10 (i.e., 

Lowrey, 1992), which is consistent with presumed nitrogen limitation. Roberts Bay (a segment 

of Sarasota Bay- see Figure 1) had a median TN:TP ratio of 2.4, which also indicates strong 

nitrogen limitation of phytoplankton growth (FDEP, 2005). 

From its inception, the SBEP recognized that wastewater and stormwater were the primary 

sources of anthropogenic nitrogen input (the other source being atmospheric deposition) entering 
the bay. As such, wastewater treatment and reclamation and stormwater treatment and 

prevention became the two most important action items in the CCMP with the goal of reducing 

nitrogen inputs to the bay by 48%. Each of these action items contained a number of specific 

elements designed to reach this nutrient reduction goal (CCMP, 1995). 

Figure 1. Map of Sarasota Bay, its watershed and tributaries.
Through the cooperation of SBEP partners - local municipal and county governments, the 

Southwest Florida Water Management District (SWFWMD), the Florida Department of 

Environmental Protection (DEP) and the Environmental Protection Agency (EPA) - in 

implementing these action items, we have documented significant improvements in water quality 

and the resultant recovery of seagrass throughout the estuary over the past twenty years. The 

highlights of these improvements and recovery are: 

1. Nitrogen loads- using the EPA approved Watershed Management Model- to Sarasota Bay 

have been reduced by 46% since 1988 (Tomasko et al., 2005). Author’s note: recent 

estimates of TN load reduction using WMM approximate 64% (Tomasko et al, 2009, 

Estuarine Research and Coastal Federation Conference, Portland Oregon) - this 

information has not been published. 

2. As of 2008, seagrass acreage is 24% higher than 1950 acreage. (Figure 2). 

3. Total seagrass acreage (2008) has increased 46% since 1988 (Figure 2). 

4. Continuous seagrass beds have increased 180% since 1988 (Figure 2). 

5. Sarasota Bay is meeting designated uses with respect to nutrients. Bay scallops returned 

to Sarasota Bay seagrass beds in 2008. Fisheries data show high abundances of juvenile 

fish within seagrass beds in all bay segments (Serviss and Sauers, 2003). These findings 

support the attainment of full aquatic life support and use. 

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

1950 1988 1994 1999 2001 2004 2006 2008

Year

Seagrass (Acres)

Continuous Patchy

 Figure 2. Total seagrass cover (in acres) for Sarasota Bay. (SWFWMD, 2008). 
Nitrogen Reduction Measures

Declines in total nitrogen (TN) concentrations and loads are a result of extensive capital 

improvement projects undertaken by our partners ($375 million). Pollution reduction efforts 

have focused on three major tributaries and coastal areas: Phillippi Creek; Whitaker Bayou, and 

Manatee County (coastal wastewater seepage from agriculture reuse and Bowlees Creek). 

Phillippi Creek- South Bay

Phillippi Creek drains 38% of the Sarasota Bay watershed. Annual TN concentrations averaged 

3.12 mg/l from 1970 through 1988 (Figure 3). Nitrogen loading from Phillippi Creek has 

decreased approximately 60% since that time. These nitrogen load reductions are the result of 

three major infrastructure programs: 1) the construction of a major watershed stormwater 

treatment facility, 2) construction of an AWWTP, allowing for the removal of nineteen 

ineffective WWTPs, and 3) a major septic tank replacement program within the watershed. 

Figure 3. Nitrogen concentrations in Phillippi Creek, the main tributary to Sarasota Bay. 

(PBSJ, 2009). 

Whitaker Bayou- Central Bay

Whitaker Bayou, a tributary which was once the largest anthropogenic contributor of nitrogen to 

Sarasota Bay (Figure 4), has seen a ten-fold reduction in nitrogen loads due to the following 

improvements: 1) upgrading the City of Sarasota wastewater treatment plant to AWT standards, 

2) expansion of the City’s reclaimed water system, 3) converting remaining areas of Whitaker 

Bayou from septic systems to central sewer, and 4) consolidation of the remaning WWTPs in the 

watershed. In 2016, the City is expected to cease discharging wastewater into Whitaker Bayou. 
 Figure 4. Nitrogen loads to Whitaker Bayou. (Tomasko et al., 2005). 

Manatee County- North Bay

Manatee County’s southwest regional WWTP (15 mgd) in north Sarasota Bay no longer 

discharges to the surface waters of the state. This was accomplished through 1) construction of a 

tail water recovery system in 1980, 2) permitting deep well injection of wastewater in 1991, and 

3) wastewater reuse. No septic tanks or package plants remain in service in the Sarasota Bay 

watershed portion of Manatee County and there is no direct discharge of wastewater in the 

northern Bay. 

The Bowlees Creek watershed has seen significant water quality improvements as a result of 

several wastewater and stormwater treatment projects. First, Lake Brennan was expanded into a 

regional stormwater treatment system. Second, the stormwater drainage system at the 

Sarasota/Bradenton Airport was reconstructed utilizing modern water quality treatment 

technologies. Finally, sewer systems were replaced or upgraded in the lower portions of the 

watershed. 

Educational Programs

The SBEP and partners have developed broad scale adult and in-school educational programs to 

promote pollution prevention and stewardship including: Florida Friendly Landscaping, 

Neighborhood Environmental Stewardship Teams and Water Wise initiatives. Local water use 

has been reduced to 80 gallons/per person/day. 
Florida Yards are required in all new development in approximately 80% of the watershed. 

Substantial public relations initiatives have been aimed at reducing water consumption and 

pollution abatement. 

Adoption of Local Fertilizer Ordinances

Finally, Sarasota County and the Cities of Sarasota and Longboat Key recently adopted fertilizer 

ordinances which prohibit, among other things, fertilizer application during the summer (wet) 

months. This ordinance covers 80% of the Sarasota Bay watershed. 

Numeric Nutrient Criteria Setting in Sarasota Bay: Role of the Sarasota Bay Estuary Program

For the past several years, the SBEP has been working with its partners to establish local water 

quality targets for the maintenance and restoration of seagrasses. To date, we have held a 

number of technical advisory committee meetings specifically to address this issue not only as a 

response to the impending criteria being developed by the EPA, but also for our partners and 

stakeholders as a framework to better understand the local response of seagrasses to nutrient 

loads so that we may better manage our estuary and its watershed. The specific role of the SBEP 

is to facilitate information exchange, modeling and technical data in support of EPA’s rule 

making process. The SBEP supports third party review. 

We recognize the timeliness for completing this task as it relates to the ongoing development of 

numeric nutrient criteria for estuarine and coastal waters in Florida by the EPA and FDEP. Their 

schedule calls for draft criteria to be established by January 2011. We have set an aggressive 

timetable in order to provide preliminary results by early June, 2010, for consideration by the 

EPA as site-specific criteria based on the best local data and knowledge. 

The basic strategy for establishing water quality and loading criteria follows that utilized over the 

past 13 years by the Tampa Bay Estuary Program (TBEP) and the Nitrogen Management 

Consortium. The paradigm depends upon knowledge of the quantitative relationships between 

light attenuation and ambient water quality (e.g., chlorophyll a) and between chlorophyll 

concentrations and nutrient loading. Empirical modeling techniques are being used to identify 

these quantitative relationships. 

The objectives of the project for setting nutrient criteria are: 

 To develop a database of nutrient loads and concentrations for each major bay segment

for the period 1989-2008 and for a future scenario and updating load estimates based on a 

new watershed loading model. 

 To define the quantitative relationships between chlorophyll a concentrations and light 

attenuation for each bay segment; 

 To estimate the chlorophyll thresholds to meet the light attenuation and seagrass targets 

for each bay segment; 

 To define the quantitative relationships between nutrient loading and chlorophyll a

concentrations for each bay segment; and 
 To estimate the numeric nutrient criteria, i.e., the nutrient loading consistent with the 

chlorophyll a thresholds, for each bay segment. These estimates will incorporate 

additional hydrological factors, including circulation and residence time, and water 

clarity parameters. 

Our initial efforts have resulted in establishing seagrass targets for each of the main bay 

segments (Table 1). Seagrass targets were based on either historical (1950) coverage or the 

average of the two most recent surveys (2004 - 2006). These targets will be re-evaluated every 

five years. This process was vetted at the technical and management levels of the program; in 

May 2009, the SBEP policy board formally approved and adopted the seagrass acreages as 

restoration goals. 

The SBEP has also established and approved interim chlorophyll a targets (also Table 1). The 

period 2001 – 2005 was selected as the performance window to include multiyear conditions 

antecedent to the most recent seagrass surveys. This time period also included years that had a 

wide range in annual rainfall. Since the average seagrass coverage from 2004 – 2006 for all bay 

segments are at or above 1950 coverage, water quality conditions from our performance window 

must be sufficient for seagrass to meet the designated target acreages. 

Historic chlorophyll thresholds (FAC 62-303) were established in 2004 by FDEP to evaluate 

nutrient impairment by major bay segment as identified in the EPA 1998 303d report. FDEP 

evaluated impairment in 2005, 2007 and 2009 using these historic chlorophyll thresholds. All 

Sarasota Bay segments have been de-listed by the FDEP for nutrients (chlorophyll a).

Table 1. Sarasota Bay Seagrass and Chlorophyll a Targets by Bay Segment. Chlorophyll a

Values Represent the Average of the Annual Means for the Period 2001 – 2005. 

Sarasota Bay Segment 

Seagrass Target 

(Acres) 

Chlorophyll a Target 

(μg/L) 

Palma Sola 1,031 8.3 

Sarasota Bay 7,269 5.0 

Roberts Bay 348 7.6 

Little Sarasota Bay 702 7.2 

Blackburn Bay 447 5.6 

TOTAL 9,997 

SBEP Concerns with the Proposed Rule

The SBEP has concerns regarding the draft rule for numeric nutrient criteria for lakes and 

streams within the Sarasota Bay watershed. This rule is based on the initial premise that 
Sarasota Bay loads are above its assimilative capacity. However, Sarasota Bay is below the 

chlorophyll thresholds in each of its bay segments and no segment has been deemed “impaired” 

for nutrients by the FDEP. Additionally, seagrass acreages are at or above their targets. 

The SBEP approach to establishing the approved loading targets is similar to the approach used 

in Tampa Bay (Greening and Janicki, 2006; Janicki and Wade, 1996) and follows EPA’s 

technical guidance which states that quantifying stressor-response relationships is the preferred 

approach in establishing numeric nutrient criteria. Specifically, the SBEP will be defining these 

quantitative relationships between nutrient loads and chlorophyll levels in all Sarasota Bay 

segments. There is considerable evidence to demonstrate that existing loads to Sarasota Bay are 

providing for the full aquatic life protection and support for all designated uses related to 

nutrients in the estuary. 

There are other concerns that deal specifically with the application of the USGS Spatially 

Referenced Regression on Watershed Attributes (SPARROW) model for the southeastern US. 

This model was used to calculate both existing and baseline loads for Sarasota Bay that were 

used to estimate protective loads for Sarasota Bay. While the SPARROW model may work well 

for its expressed purpose, i.e., to examine landscape characteristics that influence delivery of 

nitrogen from sources within the watersheds in the southeastern US, its application to the 

Sarasota Bay watershed is questionable. The Sarasota Bay load estimates that are being 

developed are driven by local data sources (particularly point sources, atmospheric deposition, 

and fertilizer shipping), while the SPARROW coefficients are based on regional (southeastern 

US) data. Thus, the scaling of SPARROW to such a small basin as Sarasota Bay needs to be 

validated. 

Estimates using SPARROW do not fully reflect the time-varying loads to an estuary and its 

resulting response to those loads. Rather, the downstream load is based on a load normalized to 

the hydrologic conditions experienced in 2002. The proposed DPV for TN (.54 mg/l) is less than 

the natural concentrations cited in the Lemon Bay model by EPA. 

Finally, the SBEP has concerns with the methodology for proposed downstream protection value 

(DPV) for estuarine protection for Sarasota Bay. The proposed DPV is inappropriate based on 

the fact that current nutrient loadings to the bay are not above their assimilative capacity based 

on recent trends and current acreages of seagrass, the primary response variable. The proposed 

TN concentration- 0.54 mg/L- for downstream protection is less than the concentration from 

natural areas derived by the EPA using the Lemon Bay Watershed Model. The SBEP will 

propose an alternative quantitative methodology based on scientifically defensible approaches, to 

derive and quantify the protective load to Sarasota Bay and its tributary streams. 
SBEP Recommendations

In conclusion, we have summarized the site-specific work that has been completed for Sarasota 

Bay, including the establishment of seagrass and chlorophyll a targets, the ongoing development 

of quantitative relationships among seagrasses, light, chlorophyll and nutrients, and the 

development of a new locally based nutrient loading model. This process has given us a 

comprehensive understanding of the relationships between nutrient loading and water quality 

responses in the Bay. 

Specifically, we recommend that the EPA consider adopting the downstream protective loads 

that will be established by the SBEP for the estuarine and coastal waters rule. The SBEP 

will present draft criteria to the FDEP and EPA by June, 2010. 

Thank you for your advanced consideration of this information regarding numeric nutrient 

criteria developed by the SBEP in the water quality standards rule making process. 

References

FDEP. 2005. Nutrient TMDL for Roberts Bay (WBID 1968D). Florida Department of 

Environmental Protection, Tallahassee, FL. 55 pp 

Greening, H. and A. Janicki. 2006. Toward reversal of eutrophic conditions in a subtropical 

estuary: water quality and seagrass response to nitrogen loading reductions in Tampa Bay, 

Florida, USA. Environmental Management Vol. 38, No. 2, pp. 163-178. 

Janicki, A.J. and D.L. Wade. 1996. Estimating Critical Nitrogen Loads for the Tampa Bay 

Estuary: An Empirically Based Approach to Setting Management Targets. Technical 

Publication #06-96 of the Tampa Bay National Estuary Program. Prepared by Coastal 

Environmental, Inc. 

Lowrey, S. 1992. Physical and chemical properties – Bay water and sediment quality. Pp. 4.1 

– 4.20, In: (P.Roat, C. Ciccolella, H. Smith, and D. Tomasko, eds.). Sarasota Bay: 

Framework for Action. Sarasota Bay National Estuary Program, Sarasota, FL. 

PBS&J. 2009. Status and trends in pollutant loads and natural resource responses in Sarasota 

Bay. Final Report SBEP to the City of Sarasota. 15p. 

CCMP. 1995. Sarasota Bay: The Voyage to Paradise Reclaimed. The Comprehensive 

Conservation Management Plan for Sarasota Bay. Sarasota Bay National Estuary Program. 

Serviss, G.M. and S. Sauers. 2003. Sarasota Bay Juvenile Fisheries Habitat Assessment. 

Final Report to the Sarasota Bay National Estuary Program. 212 p. 

SWFWMD. 2008. Seagrass distribution from Tarpon Springs to Boca Grande. Final Report. 
Tomasko, D.A., C.A. Corbett, H.S. Greening, G.E. Raulerson. 2005. Spatial and temporal 

variation in seagrass coverage in Southwest Florida: assessing the relative effects of 

anthropogenic nutrient load reductions and rainfall in four contiguous estuaries. Mar. Poll. 

Bull. 50: 797-805. 

Tomasko, D.A., M. Alderson and J. Leverone. 2009. Response of water quality and seagrass 

coverage to large-scale reductions in nitrogen loads to Sarasota Bay. Oral Presentation to the 

20th Biennial Conference of the Coastal and Estuarine Research Federation. November 1-5, 

2009. Portland, OR. 

Other Relevant Literature Reviewed

Dillon, K.S. and J.P. Chanton. 2008. Nitrogen stable isotopes of macrophytes assess 

stormwater nitrogen inputs to an urbanized estuary. Estuaries and Coasts. 31: 360-370. 

 

Johansson, J.O.R. 1991. Long-term trends of nitrogen loading, water quality and biological 

indicators in Hillsborough Bay, Florida. Pp. 157-176. In: (Treat, S.F., and P.A. Clark, eds.). 

Proceedings, Tampa Bay Area Scientific Information Symposium 2. Southwest Florida 

Regional Planning Council, St. Petersburg, FL. 528 pp. 

 

National Research Council, 1993. Managing Wastewater in Coastal Urban Areas. National 

Academy Press, Washington, DC. 

 

 Tomasko, D.A., Dawes, C.J., and M.O. Hall. 1996. The effects of anthropogenic nutrient 

enrichment on turtle grass (Thalassia testudinum) in Sarasota Bay, Florida. Estuaries 19: 

448-456. 
Appendix 2. 

Water Quality Sampling Programs 
Ambient Water Quality Sampling Programs in the SBEP Area 

Both Sarasota County and Manatee County collect water quality data within the SBEP area. 

The two monitoring programs are briefly described below. 

This Sarasota County ambient water quality monitoring program was initiated in 1995. 

Sarasota Bay was divided into 12 segments, each with multiple randomly chosen sampling 

sites. The Sarasota County Ambient Water Quality Monitoring Network segmentation 

scheme is shown in Figure 1. All program sample locations are sampled once every year. 

Each site is re-sampled every year in the same month as the preceding years. This 

randomized, stratified monitoring program characterizes overall estuarine health by 

describing entire bay segments rather than isolated locations in each water body. 

Figure 1. Sarasota County Ambient Water Quality Segments. 

Aqueous samples are taken from mid-depth from the entire coastal estuarine system in 

Sarasota County, including Sarasota Bay, Roberts Bay (Sarasota), Little Sarasota Bay, 

Blackburn Bay, Lyons Bay, Dona Bay, Roberts Bay (Venice), Lemon Bay and the estuarine 

portion of the Myakka River. 
Dataloggers are deployed at the same stations defined by the sampling program. 

Datalogger site selection produces a balanced distribution of data from throughout the 

study area. Two dataloggers are deployed monthly to measure temperature, salinity, 

dissolved oxygen concentration, percent oxygen concentration, pH, and specific 

conductance at 15 minute intervals for at least one complete 24-hour period. Field meter 

readings are taken at top, middle and bottom depths. 

The Manatee County Environmental Management Department (EMD) ambient water 

quality monitoring program for Manatee County's estuarine waters is the Regional Ambient 

Monitoring Program. RAMP began in November, 1995 and is the successor to EMD's old 

AWP station network that had operated since 1988. RAMP evolved from a series of Tampa 

Bay Estuary Program sponsored workshops on the methods, variables and field techniques 

of estuarine water quality monitoring to improve data compatibility among the water 

quality monitoring programs of the different jurisdictions. All RAMP implementations use 

the same sampling design and include the same set of core measurements. The RAMP 

concept has been endorsed by the Tampa Bay, Sarasota Bay, and Charlotte Harbor 

National Estuary Programs. 

The Manatee County RAMP program divides the County's estuarine area into two segments 

of 24, 3.56km2 hexagonal sampling areas each. The south segment includes Palma Sola 

Bay, and Sarasota Bay north of the county line, both of which are within the SBEP area. 

Sampling points were randomly located within each hexagon at the start of the program. A 

hexagonal sampling area was included in the program if the randomly generated sampling 

point was at least 4ft deep by the nautical chart and verified during program 

reconnaissance. The statistical basis of the RAMP design allows for the addition of preselected stations if there was no overriding physical reason for the station's geographic 

placement at a particular point. One-third of the sampling points in each segment, eight 

points, are sampled monthly. All sampling points in a segment are visited within each 

calendar quarter. 

In bay segments where both Sarasota and Manatee counties sample, averaged data from 

both programs are presented. Also, based on discussions with representatives of the 

sampling programs, it was decided to exclude data from segment 12 from the analysis. 

Segment 12 is in Big Sarasota Pass and likely reflects Gulf of Mexico water quality 

characteristics as much or more so than bay water characteristics, especially during flood 

tide sampling events. 

Maps of the sampling locations in Sarasota Bay are provided below in Figure 2. It should 

be noted that the rotating sampling schedule for Sarasota County’s sites are regular 

(monthly), and are shown for each month. Manatee County’s sampling rotation is not as 

regular so symbols representing each sampling grid cell are illustrated. 
Figure 2a. Sarasota Bay Sampling Sites - January 

Figure 2b. Sarasota Bay Sampling Sites - 

February

Figure 2c. Sarasota Bay Sampling Sites – March. 

Figure 2d. Sarasota Bay Sampling Sites – April.
Figure 2e. Sarasota Bay Sampling Sites - May

Figure 2f. Sarasota Bay Sampling Sites - June

Figure 2g. Sarasota Bay Sampling Sites – July.

Figure 2h. Sarasota Bay Sampling Sites - August
Figure 2i. Sarasota Bay sampling sites – 

September. 

Figure 2j. Sarasota Bay sampling sites – October.

Figure 2k. Sarasota Bay sampling sites - 

November

Figure 2l. Sarasota Bay sampling sites – 

December.

Appendix 3. 

Water Quality Trend Tests 
Chlorophyll a

(ug/l)

Palma Sola Bay Trends Appendix - Display 1 X Monthly Data Time Series X Chlorophyll a X Not Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Chlorophyll a

(ug/l)

Palma Sola Bay Trends Appendix - Display 2 X Monthly Data Time Series X Chlorophyll a X Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

98 99 00 01 02 03 04 05 06 07 08 09 10

Chlorophyll a

(ug/l)

Palma Sola Bay Trends Appendix - Display 3 X X Seasonal Univariate Statistics X Chlorophyll a X X X

0

5

10

15

20

25

30

35

40

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

Palma Sola Bay Trends Appendix - Display 4 X

Autocorrelation Statistics for Chlorophyll a

X

Unadjusted for Seasonal Medians X

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.063 0.126 -0.126

1 0.463 0.109 0.218 -0.218

2 0.296 0.117 0.233 -0.233

3 0.180 0.120 0.239 -0.239

4 0.008 0.121 0.241 -0.241

5 -0.012 0.121 0.241 -0.241

6 0.005 0.121 0.241 -0.241

7 -0.165 0.121 0.241 -0.241

8 -0.062 0.122 0.243 -0.243

9 -0.029 0.122 0.243 -0.243

10 0.104 0.122 0.243 -0.243

11 0.165 0.122 0.244 -0.244

12 0.278 0.123 0.246 -0.246

13 0.141 0.125 0.251 -0.251

14 -0.002 0.126 0.252 -0.252

15 -0.007 0.126 0.252 -0.252

Correlation

Palma Sola Bay Trends Appendix - Display 5 X Correlogram for Chlorophyll a

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Chlorophyll a

01234 5 6 7 8 9 10 11 12 13 14 15

Palma Sola Bay Trends Appendix - Display 6 X

Seasonal Kendall Tau Trend Test Statistics

Chlorophyll a X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.207 .004 0.079 -0.3
Palma Sola Bay Trends Appendix - Display 7 X

Seasonal Kendall Tau Trend Test Statistics

Chlorophyll a X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.20671 .00430537 0.079404 -0.3

Adjusted (ug/l)

Palma Sola Bay Trends Appendix - Display 8 X Time Series Plot of Data Adjusted for Season and Detrended Chlorophyll a X

Zero Reference Line Shown

-10

0

10

20

30

98 99 00 01 02 03 04 05 06 07 08 09 10

Palma Sola Bay Trends Appendix - Display 9 X

Autocorrelation Statistics for Chlorophyll a

X

Adjusted for Seasonal Median and Detrended

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.063 0.126 -0.126

1 0.302 0.109 0.218 -0.218

2 0.185 0.112 0.225 -0.225

3 0.195 0.114 0.227 -0.227

4 0.100 0.115 0.230 -0.230

5 0.177 0.115 0.231 -0.231

6 0.148 0.116 0.233 -0.233

7 -0.016 0.117 0.234 -0.234

8 0.088 0.117 0.234 -0.234

9 -0.046 0.117 0.235 -0.235

10 -0.036 0.117 0.235 -0.235

11 0.004 0.117 0.235 -0.235

12 -0.029 0.117 0.235 -0.235

13 -0.064 0.117 0.235 -0.235

Palma Sola Bay Trends Appendix - Display 9 X

Autocorrelation Statistics for Chlorophyll a

X Adjusted for Seasonal Median and Detrended

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

14 -0.089 0.118 0.235 -0.235

15 -0.120 0.118 0.236 -0.236

Correlation

Palma Sola Bay Trends Appendix - Display 10 X Correlogram for Chlorophyll a

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Chlorophyll a

01234 5 6 7 8 9 10 11 12 13 14 15
Salinity

(ppt)

Palma Sola Bay Trends Appendix - Display 11 X Monthly Data Time Series X Salinity X Not Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

45

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Salinity

(ppt)

Palma Sola Bay Trends Appendix - Display 12 X Monthly Data Time Series X Salinity X Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

45

98 99 00 01 02 03 04 05 06 07 08 09 10

Salinity

(ppt)

Palma Sola Bay Trends Appendix - Display 13 X X Seasonal Univariate Statistics X Salinity X X X

0

5

10

15

20

25

30

35

40

45

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

Palma Sola Bay Trends Appendix - Display 14 X

Autocorrelation Statistics for Salinity

X

Unadjusted for Seasonal Medians X

Lagged

Salinity Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.063 0.126 -0.126

1 0.633 0.109 0.218 -0.218

2 0.500 0.123 0.246 -0.246

3 0.453 0.131 0.261 -0.261

4 0.212 0.137 0.273 -0.273

5 0.093 0.138 0.276 -0.276

6 0.249 0.138 0.277 -0.277

7 0.169 0.140 0.280 -0.280

8 0.299 0.141 0.282 -0.282

9 0.396 0.143 0.287 -0.287

10 0.334 0.148 0.295 -0.295

11 0.359 0.151 0.301 -0.301

12 0.365 0.154 0.308 -0.308

13 0.193 0.157 0.315 -0.315

14 0.170 0.158 0.317 -0.317

15 0.064 0.159 0.318 -0.318

Correlation

Palma Sola Bay Trends Appendix - Display 15 X Correlogram for Salinity

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Salinity

01234 5 6 7 8 9 10 11 12 13 14 15

Palma Sola Bay Trends Appendix - Display 16 X

Seasonal Kendall Tau Trend Test Statistics

Salinity X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.276 0 0.052 0.267
Palma Sola Bay Trends Appendix - Display 17 X

Seasonal Kendall Tau Trend Test Statistics

Salinity X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.27563 .000101447 0.051933 0.26667

Adjusted (ppt)

Palma Sola Bay Trends Appendix - Display 18 X Time Series Plot of Data Adjusted for Season and Detrended Salinity X

Zero Reference Line Shown

-12

-11

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7

98 99 00 01 02 03 04 05 06 07 08 09 10

Palma Sola Bay Trends Appendix - Display 19 X

Autocorrelation Statistics for Salinity

X

Adjusted for Seasonal Median and Detrended

Lagged

Salinity Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.063 0.126 -0.126

1 0.549 0.109 0.218 -0.218

2 0.410 0.120 0.239 -0.239

3 0.361 0.125 0.250 -0.250

4 0.173 0.129 0.258 -0.258

5 0.050 0.130 0.260 -0.260

6 0.171 0.130 0.260 -0.260

7 0.181 0.131 0.262 -0.262

8 0.296 0.132 0.264 -0.264

9 0.360 0.135 0.269 -0.269

10 0.250 0.138 0.277 -0.277

11 0.244 0.140 0.280 -0.280

12 0.227 0.142 0.284 -0.284

13 0.103 0.143 0.286 -0.286

14 0.041 0.144 0.287 -0.287

15 -0.055 0.144 0.287 -0.287

Correlation

Palma Sola Bay Trends Appendix - Display 20 X Correlogram for Salinity

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Salinity

01234 5 6 7 8 9 10 11 12 13 14 15
Total Nitrogen

(mg/L)

Palma Sola Bay Trends Appendix - Display 21 X Monthly Data Time Series X Total Nitrogen X Not Adjusted for Seasonal Medians X

0.0

0.5

1.0

1.5

2.0

2.5

3.0

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Total Nitrogen

(mg/L)

Palma Sola Bay Trends Appendix - Display 22 X Monthly Data Time Series X Total Nitrogen X Adjusted for Seasonal Medians X

0.0

0.5

1.0

1.5

2.0

2.5

3.0

98 99 00 01 02 03 04 05 06 07 08 09 10

Total Nitrogen

(mg/L)

Palma Sola Bay Trends Appendix - Display 23 X X Seasonal Univariate Statistics X Total Nitrogen X X X

0.0

0.5

1.0

1.5

2.0

2.5

3.0

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

Palma Sola Bay Trends Appendix - Display 24 X

Autocorrelation Statistics for Total Nitrogen

X

Unadjusted for Seasonal Medians X

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.063 0.126 -0.126

1 0.430 0.109 0.218 -0.218

2 0.213 0.116 0.231 -0.231

3 0.161 0.117 0.234 -0.234

4 -0.064 0.118 0.236 -0.236

5 -0.047 0.118 0.236 -0.236

6 0.094 0.118 0.237 -0.237

7 0.166 0.119 0.237 -0.237

8 0.020 0.119 0.239 -0.239

9 0.081 0.119 0.239 -0.239

10 0.173 0.120 0.239 -0.239

11 0.011 0.121 0.241 -0.241

12 -0.022 0.121 0.241 -0.241

13 0.051 0.121 0.241 -0.241

14 -0.044 0.121 0.242 -0.242

15 -0.024 0.121 0.242 -0.242

Correlation

Palma Sola Bay Trends Appendix - Display 25 X Correlogram for Total Nitrogen

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Nitrogen

01234 5 6 7 8 9 10 11 12 13 14 15

Palma Sola Bay Trends Appendix - Display 26 X

Seasonal Kendall Tau Trend Test Statistics

Total Nitrogen X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.083 0.303 0.415 -.009
Palma Sola Bay Trends Appendix - Display 27 X

Seasonal Kendall Tau Trend Test Statistics

Total Nitrogen X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.083141 0.30273 0.41546 -.00875

Adjusted (mg/L)

Palma Sola Bay Trends Appendix - Display 28 X Time Series Plot of Data Adjusted for Season and Detrended Total Nitrogen X

Zero Reference Line Shown

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

98 99 00 01 02 03 04 05 06 07 08 09 10

Palma Sola Bay Trends Appendix - Display 29 X

Autocorrelation Statistics for Total Nitrogen

X

Adjusted for Seasonal Median and Detrended

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.063 0.126 -0.126

1 0.387 0.109 0.218 -0.218

2 0.195 0.114 0.229 -0.229

3 0.197 0.116 0.231 -0.231

4 -0.065 0.117 0.234 -0.234

5 -0.042 0.117 0.234 -0.234

6 0.114 0.117 0.235 -0.235

7 0.167 0.118 0.235 -0.235

8 0.088 0.119 0.237 -0.237

9 0.068 0.119 0.238 -0.238

10 0.135 0.119 0.238 -0.238

11 -0.128 0.120 0.239 -0.239

12 -0.096 0.120 0.240 -0.240

13 -0.096 0.121 0.241 -0.241

Palma Sola Bay Trends Appendix - Display 29 X

Autocorrelation Statistics for Total Nitrogen

X

Adjusted for Seasonal Median and Detrended

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

14 -0.093 0.121 0.242 -0.242

15 -0.078 0.121 0.242 -0.242

Correlation

Palma Sola Bay Trends Appendix - Display 30 X Correlogram for Total Nitrogen

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Nitrogen

01234 5 6 7 8 9 10 11 12 13 14 15
Total Phosphorous

(mg/L)

Palma Sola Bay Trends Appendix - Display 31 X Monthly Data Time Series X Total Phosphorous X Not Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Total Phosphorous

(mg/L)

Palma Sola Bay Trends Appendix - Display 32 X Monthly Data Time Series X Total Phosphorous X Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

98 99 00 01 02 03 04 05 06 07 08 09 10

Total Phosphorous

(mg/L)

Palma Sola Bay Trends Appendix - Display 33 X X Seasonal Univariate Statistics X Total Phosphorous X X X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

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

Palma Sola Bay Trends Appendix - Display 34 X

Autocorrelation Statistics for Total Phosphorous

X

Unadjusted for Seasonal Medians X

Lagged Total

Phosphorous Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.063 0.126 -0.126

1 0.379 0.109 0.218 -0.218

2 0.320 0.114 0.228 -0.228

3 0.272 0.118 0.235 -0.235

4 -0.036 0.120 0.240 -0.240

5 -0.066 0.120 0.240 -0.240

6 0.029 0.120 0.241 -0.241

7 0.016 0.120 0.241 -0.241

8 -0.099 0.120 0.241 -0.241

9 -0.069 0.121 0.241 -0.241

10 0.056 0.121 0.242 -0.242

11 -0.103 0.121 0.242 -0.242

12 -0.096 0.121 0.243 -0.243

13 0.043 0.122 0.243 -0.243

14 0.121 0.122 0.243 -0.243

15 -0.055 0.122 0.244 -0.244

Correlation

Palma Sola Bay Trends Appendix - Display 35 X Correlogram for Total Phosphorous

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Phosphorous

01234 5 6 7 8 9 10 11 12 13 14 15

Palma Sola Bay Trends Appendix - Display 36 X

Seasonal Kendall Tau Trend Test Statistics

Total Phosphorous X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.097 0.182 0.268 -.001
Palma Sola Bay Trends Appendix - Display 37 X

Seasonal Kendall Tau Trend Test Statistics

Total Phosphorous X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.097196 0.18177 0.26846 -.00125

Adjusted (mg/L)

Palma Sola Bay Trends Appendix - Display 38 X Time Series Plot of Data Adjusted for Season and Detrended Total Phosphorous X

Zero Reference Line Shown

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

98 99 00 01 02 03 04 05 06 07 08 09 10

Palma Sola Bay Trends Appendix - Display 39 X

Autocorrelation Statistics for Total Phosphorous

X

Adjusted for Seasonal Median and Detrended

Lagged Total

Phosphorous Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.063 0.126 -0.126

1 0.417 0.109 0.218 -0.218

2 0.323 0.115 0.231 -0.231

3 0.261 0.119 0.238 -0.238

4 -0.025 0.121 0.242 -0.242

5 -0.096 0.121 0.242 -0.242

6 0.040 0.121 0.243 -0.243

7 -0.039 0.121 0.243 -0.243

8 -0.075 0.121 0.243 -0.243

9 -0.064 0.122 0.243 -0.243

10 0.050 0.122 0.244 -0.244

11 -0.084 0.122 0.244 -0.244

12 -0.148 0.122 0.244 -0.244

13 0.094 0.123 0.246 -0.246

14 0.123 0.123 0.246 -0.246

15 -0.042 0.124 0.247 -0.247

Correlation

Palma Sola Bay Trends Appendix - Display 40 X Correlogram for Total Phosphorous

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Phosphorous

01234 5 6 7 8 9 10 11 12 13 14 15
Chlorophyll a

(ug/l)

Sarasota Bay Trends Appendix - Display 1 X Monthly Data Time Series X Chlorophyll a X Not Adjusted for Seasonal Medians X

0

2

4

6

8

10

12

14

16

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Chlorophyll a

(ug/l)

Sarasota Bay Trends Appendix - Display 2 X Monthly Data Time Series X Chlorophyll a X Adjusted for Seasonal Medians X

0

2

4

6

8

10

12

14

16

98 99 00 01 02 03 04 05 06 07 08 09 10

Chlorophyll a

(ug/l)

Sarasota Bay Trends Appendix - Display 3 X X Seasonal Univariate Statistics X Chlorophyll a X X X

0

2

4

6

8

10

12

14

16

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

Sarasota Bay Trends Appendix - Display 4 X

Autocorrelation Statistics for Chlorophyll a

X

Unadjusted for Seasonal Medians X

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.431 0.107 0.213 -0.213

2 0.226 0.113 0.226 -0.226

3 0.011 0.115 0.229 -0.229

4 -0.204 0.115 0.229 -0.229

5 -0.336 0.116 0.232 -0.232

6 -0.338 0.120 0.239 -0.239

7 -0.268 0.123 0.247 -0.247

8 -0.215 0.125 0.251 -0.251

9 -0.018 0.127 0.254 -0.254

10 0.174 0.127 0.254 -0.254

11 0.320 0.128 0.256 -0.256

12 0.414 0.131 0.262 -0.262

13 0.384 0.136 0.271 -0.271

14 0.215 0.140 0.279 -0.279

15 0.062 0.141 0.282 -0.282

Correlation

Sarasota Bay Trends Appendix - Display 5 X Correlogram for Chlorophyll a

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Chlorophyll a

01234 5 6 7 8 9 10 11 12 13 14 15

Sarasota Bay Trends Appendix - Display 6 X

Seasonal Kendall Tau Trend Test Statistics

Chlorophyll a X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.127 0.03 0.152 -0.077
Sarasota Bay Trends Appendix - Display 7 X

Seasonal Kendall Tau Trend Test Statistics

Chlorophyll a X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.12685 0.030380 0.15161 -0.07675

Adjusted (ug/l)

Sarasota Bay Trends Appendix - Display 8 X Time Series Plot of Data Adjusted for Season and Detrended Chlorophyll a X

Zero Reference Line Shown

-3

-2

-1

0

1

2

3

4

5

6

7

8

9

10

11

98 99 00 01 02 03 04 05 06 07 08 09 10

Sarasota Bay Trends Appendix - Display 9 X

Autocorrelation Statistics for Chlorophyll a

X

Adjusted for Seasonal Median and Detrended

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.135 0.107 0.213 -0.213

2 0.034 0.107 0.214 -0.214

3 0.030 0.107 0.215 -0.215

4 0.004 0.107 0.215 -0.215

5 -0.030 0.107 0.215 -0.215

6 0.035 0.107 0.215 -0.215

7 0.090 0.107 0.215 -0.215

8 0.005 0.108 0.215 -0.215

9 0.043 0.108 0.215 -0.215

10 0.011 0.108 0.215 -0.215

11 -0.050 0.108 0.216 -0.216

12 -0.075 0.108 0.216 -0.216

13 0.002 0.108 0.216 -0.216

Sarasota Bay Trends Appendix - Display 9 X

Autocorrelation Statistics for Chlorophyll a

X Adjusted for Seasonal Median and Detrended

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

14 -0.030 0.108 0.216 -0.216

15 0.064 0.108 0.216 -0.216

Correlation

Sarasota Bay Trends Appendix - Display 10 X Correlogram for Chlorophyll a

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Chlorophyll a

01234 5 6 7 8 9 10 11 12 13 14 15
Salinity

(ppt)

Sarasota Bay Trends Appendix - Display 11 X Monthly Data Time Series X Salinity X Not Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

45

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Salinity

(ppt)

Sarasota Bay Trends Appendix - Display 12 X Monthly Data Time Series X Salinity X Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

45

98 99 00 01 02 03 04 05 06 07 08 09 10

Salinity

(ppt)

Sarasota Bay Trends Appendix - Display 13 X X Seasonal Univariate Statistics X Salinity X X X

0

5

10

15

20

25

30

35

40

45

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

Sarasota Bay Trends Appendix - Display 14 X

Autocorrelation Statistics for Salinity

X

Unadjusted for Seasonal Medians X

Lagged

Salinity Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.624 0.107 0.213 -0.213

2 0.560 0.120 0.239 -0.239

3 0.483 0.129 0.258 -0.258

4 0.429 0.136 0.272 -0.272

5 0.422 0.141 0.282 -0.282

6 0.424 0.146 0.291 -0.291

7 0.436 0.150 0.300 -0.300

8 0.419 0.155 0.310 -0.310

9 0.449 0.159 0.318 -0.318

10 0.418 0.164 0.328 -0.328

11 0.467 0.168 0.336 -0.336

12 0.547 0.173 0.345 -0.345

13 0.432 0.179 0.358 -0.358

14 0.380 0.183 0.366 -0.366

15 0.274 0.186 0.372 -0.372

Correlation

Sarasota Bay Trends Appendix - Display 15 X Correlogram for Salinity

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Salinity

01234 5 6 7 8 9 10 11 12 13 14 15

Sarasota Bay Trends Appendix - Display 16 X

Seasonal Kendall Tau Trend Test Statistics

Salinity X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.421 0 .005 0.322
Sarasota Bay Trends Appendix - Display 17 X

Seasonal Kendall Tau Trend Test Statistics

Salinity X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.42130 0 .00498998 0.32167

Adjusted (ppt)

Sarasota Bay Trends Appendix - Display 18 X Time Series Plot of Data Adjusted for Season and Detrended Salinity X

Zero Reference Line Shown

-13

-12

-11

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

98 99 00 01 02 03 04 05 06 07 08 09 10

Sarasota Bay Trends Appendix - Display 19 X

Autocorrelation Statistics for Salinity

X

Adjusted for Seasonal Median and Detrended

Lagged

Salinity Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.495 0.107 0.213 -0.213

2 0.427 0.115 0.230 -0.230

3 0.359 0.121 0.242 -0.242

4 0.306 0.125 0.250 -0.250

5 0.265 0.128 0.255 -0.255

6 0.273 0.130 0.259 -0.259

7 0.308 0.132 0.264 -0.264

8 0.302 0.135 0.269 -0.269

9 0.342 0.137 0.274 -0.274

10 0.262 0.140 0.281 -0.281

11 0.307 0.142 0.284 -0.284

12 0.306 0.145 0.289 -0.289

13 0.213 0.147 0.294 -0.294

14 0.248 0.148 0.296 -0.296

15 0.132 0.150 0.300 -0.300

Correlation

Sarasota Bay Trends Appendix - Display 20 X Correlogram for Salinity

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Salinity

01234 5 6 7 8 9 10 11 12 13 14 15
Total Nitrogen

(mg/L)

Sarasota Bay Trends Appendix - Display 21 X Monthly Data Time Series X Total Nitrogen X Not Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Total Nitrogen

(mg/L)

Sarasota Bay Trends Appendix - Display 22 X Monthly Data Time Series X Total Nitrogen X Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

98 99 00 01 02 03 04 05 06 07 08 09 10

Total Nitrogen

(mg/L)

Sarasota Bay Trends Appendix - Display 23 X X Seasonal Univariate Statistics X Total Nitrogen X X X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

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

Sarasota Bay Trends Appendix - Display 24 X

Autocorrelation Statistics for Total Nitrogen

X

Unadjusted for Seasonal Medians X

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.482 0.107 0.213 -0.213

2 0.404 0.115 0.229 -0.229

3 0.235 0.120 0.240 -0.240

4 0.092 0.122 0.243 -0.243

5 0.149 0.122 0.244 -0.244

6 0.069 0.123 0.245 -0.245

7 0.134 0.123 0.245 -0.245

8 0.115 0.123 0.246 -0.246

9 0.248 0.124 0.247 -0.247

10 0.229 0.125 0.251 -0.251

11 0.250 0.127 0.254 -0.254

12 0.187 0.129 0.258 -0.258

13 0.234 0.130 0.260 -0.260

14 0.213 0.132 0.263 -0.263

15 0.134 0.133 0.266 -0.266

Correlation

Sarasota Bay Trends Appendix - Display 25 X Correlogram for Total Nitrogen

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Nitrogen

01234 5 6 7 8 9 10 11 12 13 14 15

Sarasota Bay Trends Appendix - Display 26 X

Seasonal Kendall Tau Trend Test Statistics

Total Nitrogen X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.193 .001 0.09 -.009
Sarasota Bay Trends Appendix - Display 27 X

Seasonal Kendall Tau Trend Test Statistics

Total Nitrogen X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.1926 .00104595 0.090172 -.00875

Adjusted (mg/L)

Sarasota Bay Trends Appendix - Display 28 X Time Series Plot of Data Adjusted for Season and Detrended Total Nitrogen X

Zero Reference Line Shown

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

98 99 00 01 02 03 04 05 06 07 08 09 10

Sarasota Bay Trends Appendix - Display 29 X

Autocorrelation Statistics for Total Nitrogen

X

Adjusted for Seasonal Median and Detrended

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.344 0.107 0.213 -0.213

2 0.322 0.111 0.221 -0.221

3 0.208 0.114 0.228 -0.228

4 0.145 0.116 0.231 -0.231

5 0.253 0.116 0.233 -0.233

6 0.159 0.118 0.237 -0.237

7 0.217 0.119 0.238 -0.238

8 0.160 0.121 0.241 -0.241

9 0.207 0.122 0.243 -0.243

10 0.089 0.123 0.246 -0.246

11 0.060 0.123 0.246 -0.246

12 -0.011 0.123 0.246 -0.246

13 0.044 0.123 0.246 -0.246

Sarasota Bay Trends Appendix - Display 29 X

Autocorrelation Statistics for Total Nitrogen

X Adjusted for Seasonal Median and Detrended

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

14 0.103 0.123 0.247 -0.247

15 0.072 0.124 0.247 -0.247

Correlation

Sarasota Bay Trends Appendix - Display 30 X Correlogram for Total Nitrogen

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Nitrogen

01234 5 6 7 8 9 10 11 12 13 14 15
Total Phosphorous

(mg/L)

Sarasota Bay Trends Appendix - Display 31 X Monthly Data Time Series X Total Phosphorous X Not Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Total Phosphorous

(mg/L)

Sarasota Bay Trends Appendix - Display 32 X Monthly Data Time Series X Total Phosphorous X Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

98 99 00 01 02 03 04 05 06 07 08 09 10

Total Phosphorous

(mg/L)

Sarasota Bay Trends Appendix - Display 33 X X Seasonal Univariate Statistics X Total Phosphorous X X X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

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

Sarasota Bay Trends Appendix - Display 34 X

Autocorrelation Statistics for Total Phosphorous

X

Unadjusted for Seasonal Medians X

Lagged Total

Phosphorous Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.261 0.107 0.213 -0.213

2 0.162 0.109 0.218 -0.218

3 0.285 0.110 0.220 -0.220

4 0.184 0.113 0.225 -0.225

5 0.096 0.114 0.228 -0.228

6 0.084 0.114 0.228 -0.228

7 0.083 0.114 0.229 -0.229

8 0.028 0.115 0.229 -0.229

9 0.017 0.115 0.229 -0.229

10 0.197 0.115 0.229 -0.229

11 0.083 0.116 0.232 -0.232

12 0.100 0.116 0.232 -0.232

13 0.109 0.116 0.233 -0.233

14 0.060 0.117 0.234 -0.234

15 0.094 0.117 0.234 -0.234

Correlation

Sarasota Bay Trends Appendix - Display 35 X Correlogram for Total Phosphorous

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Phosphorous

01234 5 6 7 8 9 10 11 12 13 14 15

Sarasota Bay Trends Appendix - Display 36 X

Seasonal Kendall Tau Trend Test Statistics

Total Phosphorous X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.122 0.035 0.382 -.002
Sarasota Bay Trends Appendix - Display 37 X

Seasonal Kendall Tau Trend Test Statistics

Total Phosphorous X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.12222 0.035065 0.38163 -.00166667

Adjusted (mg/L)

Sarasota Bay Trends Appendix - Display 38 X Time Series Plot of Data Adjusted for Season and Detrended Total Phosphorous X

Zero Reference Line Shown

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

98 99 00 01 02 03 04 05 06 07 08 09 10

Sarasota Bay Trends Appendix - Display 39 X

Autocorrelation Statistics for Total Phosphorous

X

Adjusted for Seasonal Median and Detrended

Lagged Total

Phosphorous Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.244 0.107 0.213 -0.213

2 0.154 0.109 0.217 -0.217

3 0.274 0.110 0.219 -0.219

4 0.214 0.112 0.224 -0.224

5 0.132 0.114 0.227 -0.227

6 0.128 0.114 0.228 -0.228

7 0.117 0.115 0.229 -0.229

8 0.057 0.115 0.230 -0.230

9 -0.008 0.115 0.231 -0.231

10 0.196 0.115 0.231 -0.231

11 0.071 0.117 0.233 -0.233

12 0.074 0.117 0.233 -0.233

13 0.102 0.117 0.234 -0.234

14 0.055 0.117 0.234 -0.234

15 0.084 0.117 0.235 -0.235

Correlation

Sarasota Bay Trends Appendix - Display 40 X Correlogram for Total Phosphorous

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Phosphorous

01234 5 6 7 8 9 10 11 12 13 14 15
Chlorophyll a

(ug/l)

Roberts Bay Trends Appendix - Display 1 X Monthly Data Time Series X Chlorophyll a X Not Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Chlorophyll a

(ug/l)

Roberts Bay Trends Appendix - Display 2 X Monthly Data Time Series X Chlorophyll a X Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

98 99 00 01 02 03 04 05 06 07 08 09 10

Chlorophyll a

(ug/l)

Roberts Bay Trends Appendix - Display 3 X X Seasonal Univariate Statistics X Chlorophyll a X X X

0

5

10

15

20

25

30

35

40

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

Roberts Bay Trends Appendix - Display 4 X

Autocorrelation Statistics for Chlorophyll a

X

Unadjusted for Seasonal Medians X

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.455 0.107 0.213 -0.213

2 0.218 0.114 0.227 -0.227

3 -0.082 0.115 0.231 -0.231

4 -0.179 0.116 0.231 -0.231

5 -0.249 0.117 0.233 -0.233

6 -0.285 0.119 0.237 -0.237

7 -0.262 0.121 0.242 -0.242

8 -0.229 0.123 0.246 -0.246

9 -0.093 0.125 0.250 -0.250

10 0.132 0.125 0.250 -0.250

11 0.258 0.126 0.251 -0.251

12 0.367 0.128 0.255 -0.255

13 0.337 0.132 0.263 -0.263

14 0.108 0.135 0.270 -0.270

15 -0.042 0.135 0.270 -0.270

Correlation

Roberts Bay Trends Appendix - Display 5 X Correlogram for Chlorophyll a

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Chlorophyll a

01234 5 6 7 8 9 10 11 12 13 14 15

Roberts Bay Trends Appendix - Display 6 X

Seasonal Kendall Tau Trend Test Statistics

Chlorophyll a X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.104 0.111 0.285 -0.132
Roberts Bay Trends Appendix - Display 7 X

Seasonal Kendall Tau Trend Test Statistics

Chlorophyll a X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.10390 0.11082 0.28539 -0.13214

Adjusted (ug/l)

Roberts Bay Trends Appendix - Display 8 X Time Series Plot of Data Adjusted for Season and Detrended Chlorophyll a X

Zero Reference Line Shown

-20

-10

0

10

20

30

40

98 99 00 01 02 03 04 05 06 07 08 09 10

Roberts Bay Trends Appendix - Display 9 X

Autocorrelation Statistics for Chlorophyll a

X

Adjusted for Seasonal Median and Detrended

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.281 0.107 0.213 -0.213

2 0.058 0.109 0.219 -0.219

3 -0.092 0.109 0.219 -0.219

4 -0.006 0.110 0.220 -0.220

5 0.003 0.110 0.220 -0.220

6 -0.012 0.110 0.220 -0.220

7 -0.012 0.110 0.220 -0.220

8 -0.090 0.110 0.220 -0.220

9 -0.037 0.110 0.220 -0.220

10 -0.019 0.110 0.220 -0.220

11 -0.068 0.110 0.220 -0.220

12 -0.052 0.110 0.221 -0.221

13 0.032 0.110 0.221 -0.221

Roberts Bay Trends Appendix - Display 9

X Autocorrelation Statistics for Chlorophyll a

X

Adjusted for Seasonal Median and Detrended

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

14 -0.075 0.110 0.221 -0.221

15 -0.021 0.111 0.221 -0.221

Correlation

Roberts Bay Trends Appendix - Display 10 X Correlogram for Chlorophyll a

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Chlorophyll a

01234 5 6 7 8 9 10 11 12 13 14 15
Salinity

(ppt)

Roberts Bay Trends Appendix - Display 11 X Monthly Data Time Series X Salinity X Not Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

45

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Salinity

(ppt)

Roberts Bay Trends Appendix - Display 12 X Monthly Data Time Series X Salinity X Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

45

98 99 00 01 02 03 04 05 06 07 08 09 10

Salinity

(ppt)

Roberts Bay Trends Appendix - Display 13 X X Seasonal Univariate Statistics X Salinity X X X

0

5

10

15

20

25

30

35

40

45

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

Roberts Bay Trends Appendix - Display 14 X

Autocorrelation Statistics for Salinity

X

Unadjusted for Seasonal Medians X

Lagged

Salinity Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.496 0.107 0.213 -0.213

2 0.177 0.115 0.230 -0.230

3 -0.001 0.116 0.232 -0.232

4 -0.045 0.116 0.232 -0.232

5 0.020 0.116 0.232 -0.232

6 -0.001 0.116 0.232 -0.232

7 -0.017 0.116 0.232 -0.232

8 -0.014 0.116 0.232 -0.232

9 -0.109 0.116 0.232 -0.232

10 0.018 0.117 0.233 -0.233

11 0.189 0.117 0.233 -0.233

12 0.310 0.118 0.235 -0.235

13 0.185 0.121 0.241 -0.241

14 -0.004 0.122 0.244 -0.244

15 -0.074 0.122 0.244 -0.244

Correlation

Roberts Bay Trends Appendix - Display 15 X Correlogram for Salinity

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Salinity

01234 5 6 7 8 9 10 11 12 13 14 15

Roberts Bay Trends Appendix - Display 16 X

Seasonal Kendall Tau Trend Test Statistics

Salinity X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.202 .002 0.14 0.192
Roberts Bay Trends Appendix - Display 17 X

Seasonal Kendall Tau Trend Test Statistics

Salinity X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.20187 .00201845 0.13981 0.19214

Adjusted (ppt)

Roberts Bay Trends Appendix - Display 18 X Time Series Plot of Data Adjusted for Season and Detrended Salinity X

Zero Reference Line Shown

-30

-20

-10

0

10

98 99 00 01 02 03 04 05 06 07 08 09 10

Roberts Bay Trends Appendix - Display 19 X

Autocorrelation Statistics for Salinity

X

Adjusted for Seasonal Median and Detrended

Lagged

Salinity Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.439 0.107 0.213 -0.213

2 0.248 0.113 0.227 -0.227

3 0.153 0.115 0.231 -0.231

4 0.065 0.116 0.232 -0.232

5 0.093 0.116 0.232 -0.232

6 0.071 0.116 0.233 -0.233

7 0.065 0.117 0.233 -0.233

8 0.140 0.117 0.234 -0.234

9 0.041 0.117 0.235 -0.235

10 0.048 0.117 0.235 -0.235

11 -0.005 0.118 0.235 -0.235

12 -0.029 0.118 0.235 -0.235

13 0.014 0.118 0.235 -0.235

14 0.023 0.118 0.235 -0.235

15 0.083 0.118 0.235 -0.235

Correlation

Roberts Bay Trends Appendix - Display 20 X Correlogram for Salinity

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Salinity

01234 5 6 7 8 9 10 11 12 13 14 15
Total Nitrogen

(mg/L)

Roberts Bay Trends Appendix - Display 21 X Monthly Data Time Series X Total Nitrogen X Not Adjusted for Seasonal Medians X

0.0

0.2

0.4

0.6

0.8

1.0

1.2

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Total Nitrogen

(mg/L)

Roberts Bay Trends Appendix - Display 22 X Monthly Data Time Series X Total Nitrogen X Adjusted for Seasonal Medians X

0.0

0.2

0.4

0.6

0.8

1.0

1.2

98 99 00 01 02 03 04 05 06 07 08 09 10

Total Nitrogen

(mg/L)

Roberts Bay Trends Appendix - Display 23 X X Seasonal Univariate Statistics X Total Nitrogen X X X

0.0

0.2

0.4

0.6

0.8

1.0

1.2

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

Roberts Bay Trends Appendix - Display 24 X

Autocorrelation Statistics for Total Nitrogen

X

Unadjusted for Seasonal Medians X

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.514 0.107 0.213 -0.213

2 0.245 0.116 0.231 -0.231

3 0.053 0.118 0.235 -0.235

4 -0.123 0.118 0.235 -0.235

5 -0.178 0.118 0.236 -0.236

6 -0.240 0.119 0.238 -0.238

7 -0.222 0.121 0.242 -0.242

8 -0.178 0.122 0.245 -0.245

9 -0.105 0.123 0.247 -0.247

10 0.092 0.124 0.248 -0.248

11 0.184 0.124 0.248 -0.248

12 0.286 0.125 0.250 -0.250

13 0.184 0.128 0.255 -0.255

14 0.117 0.129 0.257 -0.257

15 0.023 0.129 0.258 -0.258

Correlation

Roberts Bay Trends Appendix - Display 25 X Correlogram for Total Nitrogen

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Nitrogen

01234 5 6 7 8 9 10 11 12 13 14 15

Roberts Bay Trends Appendix - Display 26 X

Seasonal Kendall Tau Trend Test Statistics

Total Nitrogen X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.044 0.504 0.527 .002
Roberts Bay Trends Appendix - Display 27 X

Seasonal Kendall Tau Trend Test Statistics

Total Nitrogen X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.044156 0.50363 0.52685 .00154762

Adjusted (mg/L)

Roberts Bay Trends Appendix - Display 28 X Time Series Plot of Data Adjusted for Season and Detrended Total Nitrogen X

Zero Reference Line Shown

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

98 99 00 01 02 03 04 05 06 07 08 09 10

Roberts Bay Trends Appendix - Display 29 X

Autocorrelation Statistics for Total Nitrogen

X

Adjusted for Seasonal Median and Detrended

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.442 0.107 0.213 -0.213

2 0.180 0.113 0.227 -0.227

3 0.104 0.114 0.229 -0.229

4 -0.002 0.115 0.230 -0.230

5 0.021 0.115 0.230 -0.230

6 -0.024 0.115 0.230 -0.230

7 -0.036 0.115 0.230 -0.230

8 -0.075 0.115 0.230 -0.230

9 -0.100 0.115 0.230 -0.230

10 -0.017 0.115 0.231 -0.231

11 -0.048 0.115 0.231 -0.231

12 -0.005 0.115 0.231 -0.231

13 -0.033 0.115 0.231 -0.231

Roberts Bay Trends Appendix - Display 29 X

Autocorrelation Statistics for Total Nitrogen

X

Adjusted for Seasonal Median and Detrended

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

14 0.018 0.115 0.231 -0.231

15 0.062 0.115 0.231 -0.231

Correlation

Roberts Bay Trends Appendix - Display 30 X Correlogram for Total Nitrogen

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Nitrogen

01234 5 6 7 8 9 10 11 12 13 14 15
Total Phosphorous

(mg/L)

Roberts Bay Trends Appendix - Display 31 X Monthly Data Time Series X Total Phosphorous X Not Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Total Phosphorous

(mg/L)

Roberts Bay Trends Appendix - Display 32 X Monthly Data Time Series X Total Phosphorous X Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

98 99 00 01 02 03 04 05 06 07 08 09 10

Total Phosphorous

(mg/L)

Roberts Bay Trends Appendix - Display 33 X X Seasonal Univariate Statistics X Total Phosphorous X X X

0.0

0.1

0.2

0.3

0.4

0.5

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

Roberts Bay Trends Appendix - Display 34 X

Autocorrelation Statistics for Total Phosphorous

X

Unadjusted for Seasonal Medians X

Lagged Total

Phosphorous Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.518 0.107 0.213 -0.213

2 0.364 0.116 0.232 -0.232

3 0.368 0.120 0.240 -0.240

4 0.257 0.124 0.248 -0.248

5 0.108 0.126 0.252 -0.252

6 0.122 0.127 0.253 -0.253

7 0.088 0.127 0.254 -0.254

8 0.144 0.127 0.254 -0.254

9 0.146 0.128 0.256 -0.256

10 0.195 0.128 0.257 -0.257

11 0.240 0.130 0.259 -0.259

12 0.192 0.131 0.263 -0.263

13 0.187 0.132 0.265 -0.265

14 0.201 0.133 0.267 -0.267

15 0.145 0.134 0.269 -0.269

Correlation

Roberts Bay Trends Appendix - Display 35 X Correlogram for Total Phosphorous

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Phosphorous

01234 5 6 7 8 9 10 11 12 13 14 15

Roberts Bay Trends Appendix - Display 36 X

Seasonal Kendall Tau Trend Test Statistics

Total Phosphorous X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.329 0 0.031 -.007
Roberts Bay Trends Appendix - Display 37 X

Seasonal Kendall Tau Trend Test Statistics

Total Phosphorous X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.32857 .000000318 0.031076 -.00666667

Adjusted (mg/L)

Roberts Bay Trends Appendix - Display 38 X Time Series Plot of Data Adjusted for Season and Detrended Total Phosphorous X

Zero Reference Line Shown

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

0.34

0.36

98 99 00 01 02 03 04 05 06 07 08 09 10

Roberts Bay Trends Appendix - Display 39 X

Autocorrelation Statistics for Total Phosphorous

X

Adjusted for Seasonal Median and Detrended

Lagged Total

Phosphorous Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.378 0.107 0.213 -0.213

2 0.218 0.112 0.223 -0.223

3 0.300 0.113 0.226 -0.226

4 0.216 0.116 0.232 -0.232

5 0.083 0.118 0.235 -0.235

6 0.090 0.118 0.236 -0.236

7 0.046 0.118 0.236 -0.236

8 0.050 0.118 0.236 -0.236

9 -0.016 0.118 0.237 -0.237

10 -0.026 0.118 0.237 -0.237

11 -0.028 0.118 0.237 -0.237

12 -0.144 0.118 0.237 -0.237

13 -0.112 0.119 0.238 -0.238

14 -0.018 0.119 0.239 -0.239

15 -0.010 0.119 0.239 -0.239

Correlation

Roberts Bay Trends Appendix - Display 40 X Correlogram for Total Phosphorous

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Phosphorous

01234 5 6 7 8 9 10 11 12 13 14 15
Chlorophyll a

(ug/l)

Little Sarasota Bay Trends Appendix - Display 1 X Monthly Data Time Series X Chlorophyll a X Not Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Chlorophyll a

(ug/l)

Little Sarasota Bay Trends Appendix - Display 2 X Monthly Data Time Series X Chlorophyll a X Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

98 99 00 01 02 03 04 05 06 07 08 09 10

Chlorophyll a

(ug/l)

Little Sarasota Bay Trends Appendix - Display 3 X X Seasonal Univariate Statistics X Chlorophyll a X X X

0

5

10

15

20

25

30

35

40

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

Little Sarasota Bay Trends Appendix - Display 4 X

Autocorrelation Statistics for Chlorophyll a

X

Unadjusted for Seasonal Medians X

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.503 0.107 0.213 -0.213

2 0.251 0.115 0.231 -0.231

3 -0.055 0.117 0.235 -0.235

4 -0.149 0.117 0.235 -0.235

5 -0.266 0.118 0.236 -0.236

6 -0.301 0.120 0.241 -0.241

7 -0.275 0.123 0.246 -0.246

8 -0.266 0.125 0.251 -0.251

9 -0.084 0.128 0.255 -0.255

10 0.109 0.128 0.256 -0.256

11 0.279 0.128 0.256 -0.256

12 0.357 0.130 0.261 -0.261

13 0.350 0.134 0.268 -0.268

14 0.180 0.138 0.275 -0.275

15 -0.034 0.138 0.277 -0.277

Correlation

Little Sarasota Bay Trends Appendix - Display 5 X Correlogram for Chlorophyll a

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Chlorophyll a

01234 5 6 7 8 9 10 11 12 13 14 15

Little Sarasota Bay Trends Appendix - Display 6 X

Seasonal Kendall Tau Trend Test Statistics

Chlorophyll a X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.128 0.05 0.151 -0.115
Little Sarasota Bay Trends Appendix - Display 7 X

Seasonal Kendall Tau Trend Test Statistics

Chlorophyll a X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.1278 0.050474 0.15075 -0.115

Adjusted (ug/l)

Little Sarasota Bay Trends Appendix - Display 8 X Time Series Plot of Data Adjusted for Season and Detrended Chlorophyll a X

Zero Reference Line Shown

-20

-10

0

10

20

30

98 99 00 01 02 03 04 05 06 07 08 09 10

Little Sarasota Bay Trends Appendix - Display 9 X

Autocorrelation Statistics for Chlorophyll a

X

Adjusted for Seasonal Median and Detrended

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.308 0.107 0.213 -0.213

2 0.114 0.110 0.220 -0.220

3 -0.077 0.110 0.221 -0.221

4 0.064 0.111 0.221 -0.221

5 -0.005 0.111 0.221 -0.221

6 -0.041 0.111 0.221 -0.221

7 -0.042 0.111 0.222 -0.222

8 -0.119 0.111 0.222 -0.222

9 -0.058 0.111 0.223 -0.223

10 -0.068 0.111 0.223 -0.223

11 -0.105 0.112 0.223 -0.223

12 -0.087 0.112 0.224 -0.224

13 0.040 0.112 0.224 -0.224

Little Sarasota Bay Trends Appendix - Display 9 X

Autocorrelation Statistics for Chlorophyll a

X

Adjusted for Seasonal Median and Detrended

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

14 0.023 0.112 0.225 -0.225

15 -0.021 0.112 0.225 -0.225

Correlation

Little Sarasota Bay Trends Appendix - Display 10 X Correlogram for Chlorophyll a

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Chlorophyll a

01234 5 6 7 8 9 10 11 12 13 14 15
Salinity

(ppt)

Little Sarasota Bay Trends Appendix - Display 11 X Monthly Data Time Series X Salinity X Not Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

45

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Salinity

(ppt)

Little Sarasota Bay Trends Appendix - Display 12 X Monthly Data Time Series X Salinity X Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

45

98 99 00 01 02 03 04 05 06 07 08 09 10

Salinity

(ppt)

Little Sarasota Bay Trends Appendix - Display 13 X X Seasonal Univariate Statistics X Salinity X X X

0

5

10

15

20

25

30

35

40

45

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

Little Sarasota Bay Trends Appendix - Display 14 X

Autocorrelation Statistics for Salinity

X

Unadjusted for Seasonal Medians X

Lagged

Salinity Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.617 0.107 0.213 -0.213

2 0.293 0.119 0.239 -0.239

3 0.027 0.122 0.244 -0.244

4 -0.047 0.122 0.244 -0.244

5 -0.002 0.122 0.244 -0.244

6 0.017 0.122 0.244 -0.244

7 -0.012 0.122 0.244 -0.244

8 -0.044 0.122 0.244 -0.244

9 -0.092 0.122 0.244 -0.244

10 0.077 0.122 0.245 -0.245

11 0.225 0.123 0.245 -0.245

12 0.311 0.124 0.248 -0.248

13 0.150 0.127 0.254 -0.254

14 0.020 0.128 0.256 -0.256

15 -0.076 0.128 0.256 -0.256

Correlation

Little Sarasota Bay Trends Appendix - Display 15 X Correlogram for Salinity

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Salinity

01234 5 6 7 8 9 10 11 12 13 14 15

Little Sarasota Bay Trends Appendix - Display 16 X

Seasonal Kendall Tau Trend Test Statistics

Salinity X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.163 0.013 0.236 0.217
Little Sarasota Bay Trends Appendix - Display 17 X

Seasonal Kendall Tau Trend Test Statistics

Salinity X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.16310 0.012735 0.23566 0.21667

Adjusted (ppt)

Little Sarasota Bay Trends Appendix - Display 18 X Time Series Plot of Data Adjusted for Season and Detrended Salinity X

Zero Reference Line Shown

-30

-20

-10

0

10

98 99 00 01 02 03 04 05 06 07 08 09 10

Little Sarasota Bay Trends Appendix - Display 19 X

Autocorrelation Statistics for Salinity

X

Adjusted for Seasonal Median and Detrended

Lagged

Salinity Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.596 0.107 0.213 -0.213

2 0.347 0.119 0.237 -0.237

3 0.163 0.122 0.245 -0.245

4 0.087 0.123 0.246 -0.246

5 0.078 0.123 0.247 -0.247

6 0.104 0.124 0.247 -0.247

7 0.086 0.124 0.248 -0.248

8 0.115 0.124 0.248 -0.248

9 0.035 0.125 0.249 -0.249

10 0.053 0.125 0.249 -0.249

11 0.029 0.125 0.249 -0.249

12 0.018 0.125 0.249 -0.249

13 -0.022 0.125 0.249 -0.249

14 0.030 0.125 0.249 -0.249

15 0.064 0.125 0.249 -0.249

Correlation

Little Sarasota Bay Trends Appendix - Display 20 X Correlogram for Salinity

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Salinity

01234 5 6 7 8 9 10 11 12 13 14 15
Total Nitrogen

(mg/L)

Little Sarasota Bay Trends Appendix - Display 21 X Monthly Data Time Series X Total Nitrogen X Not Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Total Nitrogen

(mg/L)

Little Sarasota Bay Trends Appendix - Display 22 X Monthly Data Time Series X Total Nitrogen X Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

98 99 00 01 02 03 04 05 06 07 08 09 10

Total Nitrogen

(mg/L)

Little Sarasota Bay Trends Appendix - Display 23 X X Seasonal Univariate Statistics X Total Nitrogen X X X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

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

Little Sarasota Bay Trends Appendix - Display 24 X

Autocorrelation Statistics for Total Nitrogen

X

Unadjusted for Seasonal Medians X

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.560 0.107 0.213 -0.213

2 0.274 0.117 0.234 -0.234

3 0.002 0.120 0.239 -0.239

4 -0.115 0.120 0.239 -0.239

5 -0.204 0.120 0.240 -0.240

6 -0.206 0.121 0.243 -0.243

7 -0.249 0.123 0.245 -0.245

8 -0.256 0.125 0.249 -0.249

9 -0.149 0.127 0.253 -0.253

10 0.066 0.127 0.254 -0.254

11 0.212 0.127 0.255 -0.255

12 0.279 0.129 0.257 -0.257

13 0.211 0.131 0.262 -0.262

14 0.116 0.132 0.264 -0.264

15 -0.067 0.133 0.265 -0.265

Correlation

Little Sarasota Bay Trends Appendix - Display 25 X Correlogram for Total Nitrogen

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Nitrogen

01234 5 6 7 8 9 10 11 12 13 14 15

Little Sarasota Bay Trends Appendix - Display 26 X

Seasonal Kendall Tau Trend Test Statistics

Total Nitrogen X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.014 0.838 0.82 0
Little Sarasota Bay Trends Appendix - Display 27 X

Seasonal Kendall Tau Trend Test Statistics

Total Nitrogen X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.014493 0.83760 0.82029 0

Adjusted (mg/L)

Little Sarasota Bay Trends Appendix - Display 28 X Time Series Plot of Data Adjusted for Season and Detrended Total Nitrogen X

Zero Reference Line Shown

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

98 99 00 01 02 03 04 05 06 07 08 09 10

Little Sarasota Bay Trends Appendix - Display 29 X

Autocorrelation Statistics for Total Nitrogen

X

Adjusted for Seasonal Median and Detrended

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.446 0.107 0.213 -0.213

2 0.216 0.113 0.227 -0.227

3 0.048 0.115 0.230 -0.230

4 0.020 0.115 0.230 -0.230

5 0.028 0.115 0.230 -0.230

6 0.039 0.115 0.230 -0.230

7 -0.031 0.115 0.230 -0.230

8 -0.151 0.115 0.230 -0.230

9 -0.137 0.116 0.232 -0.232

10 -0.068 0.117 0.233 -0.233

11 -0.068 0.117 0.233 -0.233

12 -0.029 0.117 0.234 -0.234

13 -0.068 0.117 0.234 -0.234

Little Sarasota Bay Trends Appendix - Display 29 X

Autocorrelation Statistics for Total Nitrogen

X

Adjusted for Seasonal Median and Detrended

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

14 -0.014 0.117 0.234 -0.234

15 -0.051 0.117 0.234 -0.234

Correlation

Little Sarasota Bay Trends Appendix - Display 30 X Correlogram for Total Nitrogen

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Nitrogen

01234 5 6 7 8 9 10 11 12 13 14 15
Total Phosphorous

(mg/L)

Little Sarasota Bay Trends Appendix - Display 31 X Monthly Data Time Series X Total Phosphorous X Not Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Total Phosphorous

(mg/L)

Little Sarasota Bay Trends Appendix - Display 32 X Monthly Data Time Series X Total Phosphorous X Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

98 99 00 01 02 03 04 05 06 07 08 09 10

Total Phosphorous

(mg/L)

Little Sarasota Bay Trends Appendix - Display 33 X X Seasonal Univariate Statistics X Total Phosphorous X X X

0.0

0.1

0.2

0.3

0.4

0.5

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

Little Sarasota Bay Trends Appendix - Display 34 X

Autocorrelation Statistics for Total Phosphorous

X

Unadjusted for Seasonal Medians X

Lagged Total

Phosphorous Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.526 0.107 0.213 -0.213

2 0.388 0.116 0.232 -0.232

3 0.361 0.121 0.242 -0.242

4 0.286 0.125 0.250 -0.250

5 0.171 0.127 0.255 -0.255

6 0.190 0.128 0.256 -0.256

7 0.094 0.129 0.259 -0.259

8 0.141 0.130 0.259 -0.259

9 0.172 0.130 0.260 -0.260

10 0.182 0.131 0.262 -0.262

11 0.200 0.132 0.264 -0.264

12 0.119 0.133 0.266 -0.266

13 0.089 0.133 0.267 -0.267

14 0.186 0.134 0.267 -0.267

15 0.097 0.135 0.269 -0.269

Correlation

Little Sarasota Bay Trends Appendix - Display 35 X Correlogram for Total Phosphorous

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Phosphorous

01234 5 6 7 8 9 10 11 12 13 14 15

Little Sarasota Bay Trends Appendix - Display 36 X

Seasonal Kendall Tau Trend Test Statistics

Total Phosphorous X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.325 0 0.022 -.007
Little Sarasota Bay Trends Appendix - Display 37 X

Seasonal Kendall Tau Trend Test Statistics

Total Phosphorous X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.32543 .000000432 0.022159 -.00666667

Adjusted (mg/L)

Little Sarasota Bay Trends Appendix - Display 38 X Time Series Plot of Data Adjusted for Season and Detrended Total Phosphorous X

Zero Reference Line Shown

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

0.12

0.13

0.14

0.15

0.16

0.17

0.18

0.19

0.20

0.21

0.22

0.23

0.24

0.25

0.26

0.27

0.28

0.29

0.30

0.31

0.32

0.33

0.34

98 99 00 01 02 03 04 05 06 07 08 09 10

Little Sarasota Bay Trends Appendix - Display 39 X

Autocorrelation Statistics for Total Phosphorous

X

Adjusted for Seasonal Median and Detrended

Lagged Total

Phosphorous Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.416 0.107 0.213 -0.213

2 0.245 0.113 0.225 -0.225

3 0.255 0.115 0.229 -0.229

4 0.168 0.117 0.233 -0.233

5 0.058 0.118 0.235 -0.235

6 0.080 0.118 0.235 -0.235

7 -0.039 0.118 0.236 -0.236

8 -0.016 0.118 0.236 -0.236

9 0.015 0.118 0.236 -0.236

10 -0.029 0.118 0.236 -0.236

11 -0.012 0.118 0.236 -0.236

12 -0.156 0.118 0.236 -0.236

13 -0.163 0.119 0.238 -0.238

14 -0.038 0.120 0.239 -0.239

15 -0.090 0.120 0.239 -0.239

Correlation

Little Sarasota Bay Trends Appendix - Display 40 X Correlogram for Total Phosphorous

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Phosphorous

01234 5 6 7 8 9 10 11 12 13 14 15
Chlorophyll a

(ug/l)

Blackburn Bay Trends Appendix - Display 1 X Monthly Data Time Series X Chlorophyll a X Not Adjusted for Seasonal Medians X

0

10

20

30

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Chlorophyll a

(ug/l)

Blackburn Bay Trends Appendix - Display 2 X Monthly Data Time Series X Chlorophyll a X Adjusted for Seasonal Medians X

0

10

20

30

98 99 00 01 02 03 04 05 06 07 08 09 10

Chlorophyll a

(ug/l)

Blackburn Bay Trends Appendix - Display 3 X X Seasonal Univariate Statistics X Chlorophyll a X X X

0

10

20

30

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

Blackburn Bay Trends Appendix - Display 4 X

Autocorrelation Statistics for Chlorophyll a

X

Unadjusted for Seasonal Medians X

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.518 0.107 0.213 -0.213

2 0.189 0.116 0.232 -0.232

3 -0.018 0.117 0.234 -0.234

4 -0.132 0.117 0.234 -0.234

5 -0.258 0.117 0.235 -0.235

6 -0.329 0.120 0.239 -0.239

7 -0.311 0.123 0.246 -0.246

8 -0.217 0.126 0.252 -0.252

9 -0.045 0.127 0.255 -0.255

10 0.222 0.127 0.255 -0.255

11 0.367 0.129 0.258 -0.258

12 0.391 0.133 0.266 -0.266

13 0.373 0.137 0.274 -0.274

14 0.239 0.141 0.282 -0.282

15 -0.063 0.142 0.285 -0.285

Correlation

Blackburn Bay Trends Appendix - Display 5 X Correlogram for Chlorophyll a

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Chlorophyll a

01234 5 6 7 8 9 10 11 12 13 14 15

Blackburn Bay Trends Appendix - Display 6 X

Seasonal Kendall Tau Trend Test Statistics

Chlorophyll a X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.229 0 0.037 -0.141
Blackburn Bay Trends Appendix - Display 7 X

Seasonal Kendall Tau Trend Test Statistics

Chlorophyll a X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.22857 .000414614 0.037203 -0.14143

Adjusted (ug/l)

Blackburn Bay Trends Appendix - Display 8 X Time Series Plot of Data Adjusted for Season and Detrended Chlorophyll a X

Zero Reference Line Shown

-10

0

10

20

30

98 99 00 01 02 03 04 05 06 07 08 09 10

Blackburn Bay Trends Appendix - Display 9 X

Autocorrelation Statistics for Chlorophyll a

X

Adjusted for Seasonal Median and Detrended

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.350 0.107 0.213 -0.213

2 -0.021 0.111 0.222 -0.222

3 -0.040 0.111 0.222 -0.222

4 0.051 0.111 0.222 -0.222

5 -0.001 0.111 0.222 -0.222

6 -0.076 0.111 0.222 -0.222

7 -0.124 0.111 0.222 -0.222

8 -0.079 0.112 0.223 -0.223

9 -0.026 0.112 0.224 -0.224

10 0.107 0.112 0.224 -0.224

11 0.054 0.112 0.225 -0.225

12 -0.028 0.112 0.225 -0.225

13 0.089 0.112 0.225 -0.225

Blackburn Bay Trends Appendix - Display 9 X

Autocorrelation Statistics for Chlorophyll a

X Adjusted for Seasonal Median and Detrended

Lagged

Chlorophyll

a Correlation

Standard

Error

Upper

Limit

Lower

Limit

14 0.100 0.113 0.226 -0.226

15 -0.091 0.113 0.226 -0.226

Correlation

Blackburn Bay Trends Appendix - Display 10 X Correlogram for Chlorophyll a

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Chlorophyll a

01234 5 6 7 8 9 10 11 12 13 14 15
Salinity

(ppt)

Blackburn Bay Trends Appendix - Display 11 X Monthly Data Time Series X Salinity X Not Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

45

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Salinity

(ppt)

Blackburn Bay Trends Appendix - Display 12 X Monthly Data Time Series X Salinity X Adjusted for Seasonal Medians X

0

5

10

15

20

25

30

35

40

45

98 99 00 01 02 03 04 05 06 07 08 09 10

Salinity

(ppt)

Blackburn Bay Trends Appendix - Display 13 X X Seasonal Univariate Statistics X Salinity X X X

0

5

10

15

20

25

30

35

40

45

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

Blackburn Bay Trends Appendix - Display 14 X

Autocorrelation Statistics for Salinity

X

Unadjusted for Seasonal Medians X

Lagged

Salinity Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.592 0.107 0.213 -0.213

2 0.267 0.118 0.237 -0.237

3 0.081 0.121 0.241 -0.241

4 -0.007 0.121 0.242 -0.242

5 -0.058 0.121 0.242 -0.242

6 -0.047 0.121 0.242 -0.242

7 -0.053 0.121 0.242 -0.242

8 -0.079 0.121 0.242 -0.242

9 -0.111 0.121 0.243 -0.243

10 -0.040 0.122 0.243 -0.243

11 0.059 0.122 0.243 -0.243

12 0.074 0.122 0.244 -0.244

13 0.016 0.122 0.244 -0.244

14 -0.043 0.122 0.244 -0.244

15 -0.078 0.122 0.244 -0.244

Correlation

Blackburn Bay Trends Appendix - Display 15 X Correlogram for Salinity

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Salinity

01234 5 6 7 8 9 10 11 12 13 14 15

Blackburn Bay Trends Appendix - Display 16 X

Seasonal Kendall Tau Trend Test Statistics

Salinity X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.147 0.024 0.284 0.123
Blackburn Bay Trends Appendix - Display 17 X

Seasonal Kendall Tau Trend Test Statistics

Salinity X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.14675 0.023813 0.28355 0.12313

Adjusted (ppt)

Blackburn Bay Trends Appendix - Display 18 X Time Series Plot of Data Adjusted for Season and Detrended Salinity X

Zero Reference Line Shown

-20

-10

0

10

98 99 00 01 02 03 04 05 06 07 08 09 10

Blackburn Bay Trends Appendix - Display 19 X

Autocorrelation Statistics for Salinity

X

Adjusted for Seasonal Median and Detrended

Lagged

Salinity Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.557 0.107 0.213 -0.213

2 0.241 0.117 0.234 -0.234

3 0.126 0.119 0.238 -0.238

4 0.066 0.119 0.239 -0.239

5 -0.008 0.120 0.239 -0.239

6 0.016 0.120 0.239 -0.239

7 0.001 0.120 0.239 -0.239

8 -0.012 0.120 0.239 -0.239

9 -0.067 0.120 0.239 -0.239

10 -0.097 0.120 0.240 -0.240

11 -0.085 0.120 0.240 -0.240

12 -0.094 0.120 0.241 -0.241

13 -0.103 0.121 0.241 -0.241

14 -0.097 0.121 0.242 -0.242

15 -0.050 0.121 0.242 -0.242

Correlation

Blackburn Bay Trends Appendix - Display 20 X Correlogram for Salinity

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Salinity

01234 5 6 7 8 9 10 11 12 13 14 15
Total Nitrogen

(mg/L)

Blackburn Bay Trends Appendix - Display 21 X Monthly Data Time Series X Total Nitrogen X Not Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Total Nitrogen

(mg/L)

Blackburn Bay Trends Appendix - Display 22 X Monthly Data Time Series X Total Nitrogen X Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

98 99 00 01 02 03 04 05 06 07 08 09 10

Total Nitrogen

(mg/L)

Blackburn Bay Trends Appendix - Display 23 X X Seasonal Univariate Statistics X Total Nitrogen X X X

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

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

Blackburn Bay Trends Appendix - Display 24 X

Autocorrelation Statistics for Total Nitrogen

X

Unadjusted for Seasonal Medians X

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.544 0.107 0.213 -0.213

2 0.236 0.117 0.233 -0.233

3 -0.033 0.118 0.237 -0.237

4 -0.163 0.118 0.237 -0.237

5 -0.294 0.119 0.239 -0.239

6 -0.322 0.122 0.244 -0.244

7 -0.294 0.125 0.250 -0.250

8 -0.183 0.128 0.256 -0.256

9 -0.053 0.129 0.258 -0.258

10 0.164 0.129 0.258 -0.258

11 0.322 0.130 0.259 -0.259

12 0.364 0.133 0.265 -0.265

13 0.257 0.136 0.273 -0.273

14 0.135 0.138 0.276 -0.276

15 -0.089 0.139 0.277 -0.277

Correlation

Blackburn Bay Trends Appendix - Display 25 X Correlogram for Total Nitrogen

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Nitrogen

01234 5 6 7 8 9 10 11 12 13 14 15

Blackburn Bay Trends Appendix - Display 26 X

Seasonal Kendall Tau Trend Test Statistics

Total Nitrogen X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.126 0.051 0.039 .005
Blackburn Bay Trends Appendix - Display 27 X

Seasonal Kendall Tau Trend Test Statistics

Total Nitrogen X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

0.12597 0.051368 0.038672 .005

Adjusted (mg/L)

Blackburn Bay Trends Appendix - Display 28 X Time Series Plot of Data Adjusted for Season and Detrended Total Nitrogen X

Zero Reference Line Shown

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

98 99 00 01 02 03 04 05 06 07 08 09 10

Blackburn Bay Trends Appendix - Display 29 X

Autocorrelation Statistics for Total Nitrogen

X

Adjusted for Seasonal Median and Detrended

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.450 0.107 0.213 -0.213

2 0.145 0.114 0.227 -0.227

3 -0.008 0.114 0.229 -0.229

4 -0.042 0.114 0.229 -0.229

5 -0.107 0.114 0.229 -0.229

6 -0.090 0.115 0.229 -0.229

7 -0.126 0.115 0.230 -0.230

8 -0.042 0.115 0.231 -0.231

9 -0.006 0.116 0.231 -0.231

10 0.070 0.116 0.231 -0.231

11 0.108 0.116 0.231 -0.231

12 0.100 0.116 0.232 -0.232

13 0.044 0.116 0.233 -0.233

Blackburn Bay Trends Appendix - Display 29 X

Autocorrelation Statistics for Total Nitrogen

X

Adjusted for Seasonal Median and Detrended

Lagged

Total

Nitrogen Correlation

Standard

Error

Upper

Limit

Lower

Limit

14 0.017 0.116 0.233 -0.233

15 -0.074 0.116 0.233 -0.233

Correlation

Blackburn Bay Trends Appendix - Display 30 X Correlogram for Total Nitrogen

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Nitrogen

01234 5 6 7 8 9 10 11 12 13 14 15
Total Phosphorous

(mg/L)

Blackburn Bay Trends Appendix - Display 31 X Monthly Data Time Series X Total Phosphorous X Not Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

JAN98 JAN99 JAN00 JAN01 JAN02 JAN03 JAN04 JAN05 JAN06 JAN07 JAN08 JAN09 JAN10

Adjusted

Total Phosphorous

(mg/L)

Blackburn Bay Trends Appendix - Display 32 X Monthly Data Time Series X Total Phosphorous X Adjusted for Seasonal Medians X

0.0

0.1

0.2

0.3

0.4

0.5

98 99 00 01 02 03 04 05 06 07 08 09 10

Total Phosphorous

(mg/L)

Blackburn Bay Trends Appendix - Display 33 X X Seasonal Univariate Statistics X Total Phosphorous X X X

0.0

0.1

0.2

0.3

0.4

0.5

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

Blackburn Bay Trends Appendix - Display 34 X

Autocorrelation Statistics for Total Phosphorous

X

Unadjusted for Seasonal Medians X

Lagged Total

Phosphorous Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.570 0.107 0.213 -0.213

2 0.412 0.118 0.235 -0.235

3 0.529 0.123 0.246 -0.246

4 0.435 0.131 0.263 -0.263

5 0.262 0.137 0.273 -0.273

6 0.298 0.139 0.277 -0.277

7 0.233 0.141 0.282 -0.282

8 0.168 0.142 0.285 -0.285

9 0.155 0.143 0.286 -0.286

10 0.126 0.144 0.288 -0.288

11 0.129 0.144 0.288 -0.288

12 0.052 0.145 0.289 -0.289

13 0.032 0.145 0.289 -0.289

14 0.057 0.145 0.289 -0.289

15 0.097 0.145 0.290 -0.290

Correlation

Blackburn Bay Trends Appendix - Display 35 X Correlogram for Total Phosphorous

 X Unadjusted for Seasonal Median X

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Phosphorous

01234 5 6 7 8 9 10 11 12 13 14 15

Blackburn Bay Trends Appendix - Display 36 X

Seasonal Kendall Tau Trend Test Statistics

Total Phosphorous X

Unadjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.283 0 0.082 -.007
Blackburn Bay Trends Appendix - Display 37 X

Seasonal Kendall Tau Trend Test Statistics

Total Phosphorous X

Adjusted for Seasonal Medians

Tau

Statistic

P-Value

Without

Serial

Correlation

P-Value

With Serial

Correlation

Slope

Statistic

-0.28312 .000009705 0.081598 -.00714286

Adjusted (mg/L)

Blackburn Bay Trends Appendix - Display 38 X Time Series Plot of Data Adjusted for Season and Detrended Total Phosphorous X

Zero Reference Line Shown

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

0.34

0.36

0.38

0.40

98 99 00 01 02 03 04 05 06 07 08 09 10

Blackburn Bay Trends Appendix - Display 39 X

Autocorrelation Statistics for Total Phosphorous

X

Adjusted for Seasonal Median and Detrended

Lagged Total

Phosphorous Correlation

Standard

Error

Upper

Limit

Lower

Limit

0 1.000 0.062 0.123 -0.123

1 0.509 0.107 0.213 -0.213

2 0.302 0.115 0.231 -0.231

3 0.432 0.118 0.237 -0.237

4 0.338 0.124 0.248 -0.248

5 0.178 0.128 0.255 -0.255

6 0.215 0.129 0.257 -0.257

7 0.142 0.130 0.260 -0.260

8 0.005 0.131 0.261 -0.261

9 -0.041 0.131 0.261 -0.261

10 -0.078 0.131 0.261 -0.261

11 -0.063 0.131 0.262 -0.262

12 -0.176 0.131 0.262 -0.262

13 -0.177 0.132 0.264 -0.264

14 -0.156 0.133 0.265 -0.265

15 -0.117 0.133 0.267 -0.267

Correlation

Blackburn Bay Trends Appendix - Display 40 X Correlogram for Total Phosphorous

 X Adjusted for Seasonal Median and Detrended

Zero Reference Line Shown U=Upper 95% Confidence Limit L=Lower 95% Confidence Limit

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Lagged Total Phosphorous

01234 5 6 7 8 9 10 11 12 13 14 15
Appendix 4. 

Residence Time Calculations 
The method used in this effort is predicated on a well-defined flow path for freshwater beginning at 

the head of an estuary. For a lagoonal system, it is necessary to define the flow path for freshwater 

entering the estuary at a given point. For the Sarasota Bay Estuary system, two segment groupings 

were used to represent separate freshwater flow paths, defined as follows for each grouping (Figure 

V-9): 

• Northern: Palma Sola Bay flows downstream to Sarasota Bay. The northern half of Little 

Sarasota Bay flows downstream to Roberts Bay, which in turn flows downstream to Sarasota 

Bay. Sarasota Bay flows downstream to the Gulf of Mexico. 

• Southern: Southern half of Little Sarasota Bay flows downstream to Blackburn Bay. 

Blackburn Bay flows downstream to Dona and Roberts Bay. 

For each of the segments in these groupings, non-advective transports were estimated based on 

observed salinity. Exchange coefficients for non-advective transport were estimated using mean 

water column salinity data, obtained from the FDEP IWR database. The algorithm for exchange 

coefficients estimation was based on the salinity mass balance equations developed for each 

segment of the Sarasota Bay Estuary system. The salinity mass balance equations are provided 

below for each segment, based on the assumption that for a given month, the mass of salinity 

coming into the segment is balanced by the mass of salinity leaving the segment. Here, as in Figure 

1, Q is the freshwater inflow to the segment from its watershed, C is the salinity in the segment, and 

E is the non-advective exchange rate between two segments. 

Northern Grouping 

Palma Sola Bay: 

0= -QPSBCPSB + ESB,PSB(CSB-CPSB) 

Little Sarasota Bay North: 

0= -0.5QLSBCLSB + ERB,LSB(CRB-CLSB) 

Roberts Bay: 

0= -(0.5QLSB+QRB)CRB + 0.5QLSBCLSB + ESB,RB(CSB-CRB) - ERB,LSB(CRB-CLSB) 

Sarasota Bay: 

0= -(0.5QLSB+QRB+QSB+QPSB)CSB + (0.5QLSB+QRB)CRB + QPSBCPSB 

 - ESB,RB(CSB-CRB) - ESB,PSB(CSB-CPSB) + EGOM,SB(CGOM-CSB) 

Southern Grouping 

Little Sarasota Bay South: 

0= -0.5QLSBCLSB + EBB,LSB(CBB-CLSB) 

Blackburn Bay: 

0= -(0.5QLSB+QBB)CBB + 0.5QLSBCLSB – EBB,LSB(CBB-CLSB) + EDARB,BB(CDARB-CBB) 

For the northern grouping, there are four equations and four unknowns, so that the equations can 

be solved for the non-advective exchange rates (E-values) as follows: 
Sarasota Bay/Palma Sola Bay: 

ESB,PSB = QPSBCPSB/(CSB-CPSB) 

Roberts Bay/Little Sarasota Bay North: 

ERB,LSB = 0.5QLSBCLSB/(CRB-CLSB) 

Sarasota Bay/Roberts Bay: 

ESB,RB = (0.5QLSB+QRB)CRB/(CSB-CRB) 

Gulf of Mexico/Sarasota Bay: 

EGOM,SB = (0.5QLSB+QRB+QSB+QPSB)CSB/(CGOM-CSB) 

For the southern grouping, there are two equations and two unknowns, so that the equations can 

be solved for the non-advective exchange rates (E-values) as follows: 

Blackburn Bay/Little Sarasota Bay South: 

EBB,LSB = 0.5QLSBCLSB/(CBB-CLSB) 

Dona and Roberts Bay/Blackburn Bay: 

EDARB,BB = (0.5QLSB+QBB)CBB/(CDARB-CBB) 

Monthly exchange coefficients were calculated using hydrologic loading data and salinity 

concentration data for 1994-2007. The median exchange coefficients over all months for a given 

boundary were determined, and used for calculation of the PRTs, described below. 

Equations for dilution of a simulated conservative tracer were developed based on the methods of 

Hagy et al. (2000). The PRT was defined as the length of time required to reduce the mass of a 

tracer in a given segment to e-1 times the initial mass. This calculation was performed using the 

monthly inflows for each month of the 1994-2007 period, so that a segment-specific PRT was 

calculated for each month’s inflows. 

The box model equations for mass balance provided above were used to estimate the change in 

mass of tracer (∆M) present in each box (segment) of the model for relatively small time increments 

(∆t=1 hour). The equation for Palma Sola Bay is provided below: 

Palma Sola Bay: 

∆MPSB = -QPSBCPSB∆t + ESB,PSB(CSB-CPSB)∆t, 

with CPSB and CSB updated after each time step until the mass of the tracer in Palma Sola Bay 

declines to e-1 of its original value. Similar equations were used for each of the segments, 

modifying the mass balance equations provided above to provide tracking of conservative tracer 

masses in each segment. For the boundary conditions, the salinity values in the Gulf of Mexico and 

Dona and Roberts Bay were set to 36 ppt, and the tracer mass was set to 0. 
Figure 2-1. Box model schematic for Sarasota Bay Estuary Program. PSB - Palma Sola Bay; 

SB - Sarasota Bay; RB - Roberts Bay; LSB - Little Sarasota Bay; BB - Blackburn Bay; 

DARB – Dona and Roberts Bay. 
Appendix 5. 

Regression Analysis Results