PROPOSED 

NUMERIC NUTRIENT CRITERIA 

FOR CLEARWATER HARBOR 

AND SAINT JOSEPH SOUND 

 Prepared for: 

Pinellas County Watershed Management Section 

 Department of Environment and Infrastructure 

300 South Garden Avenue 

Clearwater, Florida 33756 

Prepared by: 

Janicki Environmental, Inc. 

1155 Eden Isle Drive NE 

Saint Petersburg, Florida 33704 

September, 2011
2 

1.0 Introduction 

The Florida Department of Environmental Protection (FDEP) is currently developing a rule to 

establish numeric nutrient criteria for a number of water body types. The following summarizes 

FDEP’s view on the development of numeric nutrient criteria in Florida (FDEP website, 2011). 

The overarching FDEP goal is to “manage nutrients in surface (and groundwater) at loadings or 

concentrations that result in protection and maintenance of healthy, well-balanced aquatic 

communities”. Absent site-specific analyses, criteria should be based on a quantifiable linkage 

between anthropogenic nutrient enrichment and a biological response (such as seagrass growth) 

that can be used to numerically interpret the narrative nutrient criteria. There is value in knowing 

whether nutrient concentrations are potentially elevated to environmentally harmful levels, but it is 

important to identify adverse biological effects and determine if they are linked to nutrients before 

deciding that nutrient reductions should be pursued. 

The Department recognizes the role of site-specific factors that affect numeric responses and 

proposes to base new standards on establishing a systematic numeric interpretation of the existing 

narrative criteria. This concept is intended to implement Rule 62-302.530 (47)(b), FAC, which 

states, “in no case shall nutrient concentrations of a body of water be altered so as to cause an 

imbalance in natural populations of aquatic flora or fauna.” 

As envisioned by FDEP, the narrative nutrient criteria would continue to apply to all waterbodies, 

and numeric interpretations would be applied when adequate scientific information is available. 

The narrative criteria would be implemented using a systematic structure that numerically interprets 

the narrative nutrient criteria for each waterbody in a hierarchical manner. 

This document provides background information concerning the estuarine systems of Clearwater 

Harbor and Saint Joseph Sound, including a brief physical characterization of the system and a 

summary of work completed to assess the state of the estuarine natural resources and develop 

management targets and thresholds that can be used to evaluate changes in the estuary over time 

compared to an identified reference period that represents full support of aquatic life uses in 

accordance with FDEP and EPA standards. The information provided in this document is the result 

of an agreement by a consortium of municipal governments, Pinellas County and the Southwest 

Florida Water Management District to develop a Comprehensive Conservation and Management 

Plan (CCMP) for Clearwater Harbor and Saint Joseph Sound (CHSJS). This effort is ongoing with 

completion scheduled for December, 2011. As part of this CCMP, management goals have been 

developed to serve as guidance for evaluating the condition of the estuarine systems of the CHSJS. 

These goals as they relate to the establishment of numeric nutrient criteria for these waterbodies are 

explained in further detail below. 

The CHSJS Study Area 

The CHSJS study area encompasses much of western Pinellas County, includes both estuarine 

segments and their associated watersheds, and borders the management boundary of the Tampa 

Bay Estuary Program. The segments are Saint Joseph Sound (SJS); Clearwater Harbor North (CHN), 

and Clearwater Harbor South (CHS) (Figure 1-1). The jurisdictions within the CCMP are provided 

in Figure 1-2. 
3 

Figure 1-1. The CHSJS CCMP area in relation to the Tampa Bay Estuary Program boundaries. 
4 

Figure 1-2. Jurisdictions within the CHSJS and its watershed. 
5 

The Saint Joseph Sound estuary occupies approximately 18,000 acres within Pinellas County and is 

bounded to the north by the Anclote Anchorage at the mouth of the Anclote River and to the south 

by Dunedin Causeway. Several barrier islands including Anclote Key, Three Rooker Bar, and 

Honeymoon Island mark the western boundary of SJS. Large passes between these barrier islands 

provide significant tidal interaction with the Gulf of Mexico. Much of the eastern shoreline of the 

estuary has been hardened by seawall and rip-rap, such as can be seen along Klosterman Bayou. In 

contrast, the western shorelines along the barrier islands have remained largely in a natural state. 

The natural areas on the barrier islands provide major public recreation features including 

Honeymoon Island State Recreation Area and Anclote Key Preserve State Park, with the latter 

accessible only by boat. 

Clearwater Harbor North occupies approximately 5,876 acres and is substantially narrower and 

somewhat less connected to the Gulf of Mexico than Saint Joseph Sound. Hurricane Pass, in the 

northern region of Clearwater Harbor North provides the only direct tidal interaction with the Gulf 

of Mexico within the segment; however much of the water in CHN also exchanges with the Gulf 

via Clearwater Pass to the south. Clearwater Harbor North is bounded to the west by Caladesi 

Island and Clearwater Beach Island and to the east by mainland Florida and the cities of Dunedin 

and Clearwater. The great majority of the estuary’s shoreline is hardened by seawall and rip-rap to 

accommodate coastal development and to prevent erosion of the shoreline, including much of the 

barrier islands. Large areas of the bay bottom have been dredged and filled to create residential 

canal developments that extend into the estuary. Major public recreation features in Clearwater 

Harbor North include Caladesi Island State Park and Clearwater Beach.

Clearwater Harbor South is the smallest estuarine segment (3,831 acres) and least tidally connected 

of the three bay segments with tidal exchange occurring principally through Clearwater Pass in the 

northern portion. The construction of the Clearwater Memorial Causeway, much of which 

involved filling the bay bottom to allow road construction, has restricted the connection between 

Clearwater Harbor North and Clearwater Harbor South with north/south tidal exchange limited on 

the eastern and western sides of the causeway. From Clearwater Pass at the north end of this 

segment, the segment quickly narrows from approximately 2 km across to less than 0.2 km in width 

at The Narrows where it adjoins to Boca Ciega Bay via a dredged channel that serves as the 

Intracoastal Waterway. Much of the southern extent of Clearwater Harbor South from Belleair to 

Indian Rocks Beach has been filled to create residential canal developments that form its western 

boundary along Sand Key. 

Pinellas County, in cooperation with local scientists and FDEP, has developed a list of symptoms of 

nutrient enrichment in the CHSJS, along with potential explanations of these expressions, to aid in 

development of numeric nutrient criteria for this area. This listing is provided in Tables 1-1 and 1-2 

below and the entire summary is provided as Appendix A. The tables below provide a summary of 

potential responses to nutrients, and whether these responses are currently or historically observed. 
6 

Table 1-1. Checklist of nutrient enrichment symptoms. 

‐ = Empty cell/no data

Response Variable   Observed

Historically?

Observed

Currently?

Explanation Source

Low dissolved

oxygen (DO)

(hypoxia/anoxia)

Yes Yes Some tidal creeks are on the 303(d) list for

DO.  In open waters, some areas have

bottom DO below 4 (mg/L) during summer.

303(d) list;

Levy 2010

Reduced clarity   Yes No SAV loss from 1950 to 1982 likely due to

reduced clarity, but acreage has been

increasing for past 20 years.

SWFWMD

Increased chla

concentrations

Yes   No Historical loss of SAV likely related to chla;

however, concentrations have decreased

or remained constant since 1992.

Levy 2010

Phytoplankton

blooms (nuisance

or toxic)

Yes No Red tide (Karenia brevis blooms) is

common in this part of the coast

‐ 

Problematic

epiphyte growth  

No No Epiphyte loads vary throughout the region,

but have not been related to nutrient levels

or considered problematic

Meyer and Levy

2008

Problematic

macroalgal growth

No No Macroalgae are a major component of the

submersed aquatic community, but not

considered problematic.

Meyer and Levy

2008

SAV community

changes or loss

Yes No Over 50% of SAV was lost in Boca Ciega Bay

from 1950 to 1982, and some loss likely

occurred in Clearwater Harbor.  SAV

coverage in Boca Ciega Bay rebounded to

80% former coverage in 2008.  SAV

coverage increased 16% between 1999 and

2008.  Losses occurred in all areas due to

dredging and filling, and that loss is

considered permanent and not related to

nutrients or water clarity.   

K. Levy, PCDEM,

personal

communication;

SWFWMD SAV

data

Emergent/

shoreline

vegetation changes  

Yes  ‐  Much of the mainland shoreline has been

developed, so there are many seawalls and

little intact shoreline vegetation.

‐ 

Coral/hard‐bottom

community

changes or loss  

Unknown ‐  There is some hard‐bottom community in

this area, but it has not been studied.  

‐ 

Impacts to benthic

community

Unknown  ‐  ‐ ‐ 

Fish kills   Yes, limited

in space and

time

‐  Fish kills have periodically occurred as a

result of red tide blooms and cold‐water

induced shock; however, no significant kills

have been reported as a direct result of

nutrient inputs into the estuary.

‐ 
7 

Table 1-2. Checklist of additional factors. 

‐ = Empty cell/no data

Nutrient Factors Observed? Explanation Source

Increased nutrient loading or

concentrations

No Historical increases, but nutrient loading from

humans has decreased in the past 10 years.  

Levy 2010

Difference between nearshore

and offshore levels  

Unknown No data available for coastal area outside

barrier islands.

‐ 

Mitigating factors that could

prevent nutrient expression

No ‐ ‐ 

Other significant stressors to

biological communities

No  ‐ 

Natural high‐nutrient episodes

(e.g., seasonal or  event driven)

No ‐ ‐ 

The CHSJS watershed receives approximately 50 inches of rainfall annually with nearly half of the 

total occurring over four months between June and September (Figure 1-3). The largest source of 

freshwater inflow into the CHSJS estuary is the Anclote River. The remaining freshwater sources 

are smaller creeks and small magnitude coastal springs including Klosterman Creek, Curlew Creek, 

Cedar Creek, Spring Branch, Stevenson Creek, Smith Creek, McKay Creek and Wall Spring. While 

these tributaries deliver a much lower volume of freshwater than the Anclote River, they remain 

ecologically import and contribute significant amounts of freshwater, nutrients and sediments to the 

estuary. Direct runoff from coastal lands, direct precipitation to the estuary as well as direct 

discharge from stormwater outfalls also contribute freshwater and nutrients to the estuarine waters. 

Figure 1-3. Distribution of monthly rainfall at City of Tarpon Springs rain gage over a 75 year period of 

record. 
8 

2.0 Objective 

The objective of this document is to propose estuarine numeric nutrient criteria specific to the three 

open estuarine segments of the CHSJS: Saint Joseph Sound, Clearwater Harbor North, and 

Clearwater Harbor South. These concentration-based criteria were developed using a “Reference 

Period” approach. 

3.0 Development of Seagrass and Chlorophyll a Targets 

This section describes the data and analytical approaches to establishing seagrass and chlorophyll a

targets for the CHSJS. 

3.1 Background and Rationale 

The CCMP for Clearwater Harbor and Saint Joseph Sound is modeled on similar work conducted 

by the EPA’s three National Estuary Programs of southwest Florida. The identification of water 

quality response endpoints is a critical step in identifying management level criteria for these 

waterbodies and substantial efforts have been made to identify response indicators that can be used 

to evaluate the health of the estuaries. An outcome of this work has been the realization that each 

estuary has unique attributes that govern specific cause and effect relationships between 

anthropogenic stressors and water quality responses. Further, in some cases scientifically 

defensible cause and effect relationships between nutrients and water quality responses have not 

been apparent. Factors including estuarine residence times and nutrient loadings play an important 

role in the assimilation of nutrients within the estuary and their expression. In this way, each 

estuary is different and therefore site-specific criteria are beneficial to ensure the appropriate 

management actions are taken. In the CHSJS, seagrasses are a critical indicator of estuarine health 

and provide a critical endpoint in the development of numeric nutrient criteria. 

3.2 Development of Seagrass Targets 

Seagrasses are keystone communities in the CHSJS, as well as the majority of the estuaries in 

southwest Florida. Seagrass health and success depends on good water quality and water clarity, 

making seagrasses useful indicators of ecosystem health. As part of the CHSJS State of the Resource 

Report (Janicki Environmental, 2011), historical photography was used to estimate seagrass acreage 

in the estuary. National Archive’s ca. 1942 were used and supplemented by photographs taken in 

1957 in the western portion of Saint Joseph Sound. These estimates were then compared to recent 

surveys conducted by the SWFWMD after adjusting for non-restorable areas, such as dredging of 

the Intracoastal Waterway and other dredge and fill projects. 

Current seagrass areal extents are 81%, 73% and 67% of historic estimates for Saint Joseph Sound, 

Clearwater Harbor North and Clearwater Harbor South, respectively (Figure 3-1). While Clearwater 

Harbor South has lost the largest proportion of seagrasses relative to its historic estimate, St Joseph 

Sound lost more acreage than the other segments. 
9 

Figure 3-1. Comparison of historic seagrass estimates circa 1940’s (adjusted for non-restorable areas) and 

most recent estimates from the SWFWMD (2010). 

Despite these historical losses, seagrass acreage has been trending upward since 1999 throughout 

Clearwater Harbor and there have been substantial recent gains in Saint Joseph Sound. The most 

recent seagrass mapping efforts, completed in 2010, indicate that in Saint Joseph Sound, seagrass 

cover in 2010 was 15% higher than in 1999, an increase of 1,680 acres (Figure 3-2). In Clearwater 

Harbor North, seagrass acreage increased 56%, from 2,416 acres in 1999 to 3,758 acres in 2010. 

Seagrass cover in Clearwater Harbor South increased 66%, from 545 acres to 902 acres between 

1999 and 2010 indicating that limiting factors for seagrass have improved over recent history 

Historical seagrass estimates were used to develop seagrass areal extent targets in CHN and CHS. 

Given the recent trajectory in seagrass acreage in these segments, the historical acres (adjusted for 

non-restorable areas) were thought to be reasonable estimates of the potential gains. However, in 

Saint Joseph Sound large areas of historic seagrass loss appear to be due to physical disturbances 

such as barrier island migration, the dredging of the ICW and its associated impacts on current 

velocities, and depth and wave energy, as well as the potential effects of episodic biological 

perturbations and grazing events as described in the State of the Resource Report (Janicki 

Environmental, 2011). Given these considerations, it was deemed unrealistic to develop a target 

for Saint Joseph sound that is based on historical conditions. Consequently, the seagrass areal target 

acreage for Saint Joseph Sound is an average of the two most recent surveys. Therefore, the 

segment-specific seagrass targets proposed for the CHSJS are: 

 St, Joseph Sound 12,539 acres 

 Clearwater Harbor North 5,142 acres 

 Clearwater Harbor South 1,595 acres 
10 

Figure 3-2. Change in seagrass areal extent between 1999 and 2010 for each CHSJS estuarine segment. 

3.3 Development of Chlorophyll a Targets and Thresholds 

Pinellas County’s ambient water quality monitoring program uses both a fixed station and 

probabilistic sampling routine. The estuarine, open bay water quality sampling program was 

historically based on fixed stations until 2003 when a probabilistic sampling design was initiated 

(Janicki Environmental, 2003). The probabilistic routine was designed to generalize water quality 

information collected at particular locations to the entire study area with statistical confidence 

specifically to fulfill the Pinellas County needs while also being applicable to the FDEP for use in 

their Impaired Waters assessments. The historic fixed stations locations and a the distribution of 

samples collected under the probabilistic design between 2003 and 2009 in Saint Joseph Sound, 

Clearwater Harbor North, and Clearwater Harbor South is provided in Figures 3-3 through 3-5, 

respectively. The historic fixed stations in the estuary are highlighted with a purple triangle. 
11 

Figure 3-3. Location of water quality sampling stations in Saint Joseph Sound. Historical fixed stations 

(purple triangles); probabilistic samples collected between 2003 and 2009 (green circles). 
12 

Figure 3-4. Location of water quality sampling stations in Clearwater Harbor North. Historical fixed 

stations (purple triangles); probabilistic samples collected between 2003 and 2009 (green circles). 
13 

Figure3-5. Location of water quality sampling stations in Clearwater Harbor South. Historical fixed 

stations (purple triangles); probabilistic samples collected between 2003 and 2009 (green circles). 
14 

In the past, a single fixed station within each estuarine segment was sampled monthly as a primary 

site. The other fixed stations were sampled bi-monthly as secondary sites. The location of these 

sites was based on professional judgment and sometimes located to monitor known or suspected 

pollutant sources. When the probabilistic design was implemented in 2003, the sampling 

frequency was divided into nine equivalently distributed “sampling periods” and the exact 

sampling date within each sampling period was also assigned randomly from a list frame of 

potential sampling dates (Janicki Environmental, 2003). From 2003-2007, nine sampling periods 

were used within a year and a total of 36 samples were collected from each of three sampling strata 

in a year. In 2008, due to budget constraints, the County reduced the number of sampling periods 

from 9 to 8. Each annual sampling allocation was divided into eight periods and a total of 32 

samples were collected in each stratum. 

The average chlorophyll a concentration from data collected between 2003 and 2009 was 2.7 μg/L, 

4.0 μg/L, and 5.7 μg/L for Saint Joseph Sound, Clearwater Harbor North, and Clearwater Harbor 

South, respectively. A brief comparison of recent data collected using the probabilistic design 

(2003-2009) and historical fixed station data collected from 1992-2002 is provided below to give 

descriptive context to changes in water quality over time. For the purposes of understanding past 

and present conditions of these segments it was important to understand if and how these disparate 

datasets may be used in the target-setting process. 

A descriptive assessment comparing recent and historical water quality suggests that water quality 

conditions with respect to chlorophyll a concentrations have improved over time. Average 

chlorophyll a concentrations based on the historical fixed station data were 6.2 μg/L, 7.2 μg/L, and 

8.3 μg/L for Saint Joseph Sound, Clearwater Harbor North, and Clearwater Harbor South, 

respectively. The distribution of chlorophyll a concentrations in historical and recent datasets is 

provided in Figure 3-6. Note that the distribution of chlorophyll a concentrations is higher in the 

historical fixed station data than in the recent data and that the same latitudinal (north-south) 

gradient exists in both datasets suggesting a persistent latitudinal gradient in chlorophyll a

concentrations throughout the study area. All within-segment differences were statistically 

significant using the Wilcoxon Rank Sum test (Sokal and Rohlf, 1984). 

Further supporting evidence of improving chlorophyll a concentrations comes from an examination 

of timeseries trends in chlorophyll a. Annual averages for chlorophyll a, TN and TP were calculated 

for each historical station within a segment. The probabilistic data were assigned a station name 

corresponding to the strata name for the segment (i.e., W1 for Saint Joseph Sound, W2 for 

Clearwater Harbor North, and W3 for Clearwater Harbor South) (Figure 3-7). Annual averages 

were calculated for all of the “random” samples within the segment for each year. The annual 

averages for each timeseries were then plotted with each trend depicted as a single line (Figures 3-8 

– 3-10). There are several elements of note in these figures. 

 First, there is substantial correlation in the timeseries trend among fixed stations over time in 

each segment. 

 Second, the fixed station trend appears to continue with the timeseries of probabilistic data. 

 Lastly, all annual average chlorophyll a values were well below the FDEP state threshold of 

11 μg/L other than two stations in Clearwater Harbor South in 1997 and 1998 (even in 

these years the overall segment average was below the threshold value). 
15 

Figure 3-6. Distribution of chlorophyll a concentrations in historical fixed station “Fixed” and recent 

probabilistic “Random” data in all three CHSJS segments. 

Figure 3-7. The geographic extent of the CHSJS segments for which numeric nutrient criteria are proposed. 
16 

Figure 3-8. Annual average chlorophyll a concentrations in Saint Joseph Sound. Individual fixed stations 

sampled between 1992 and 2002 and the probabilistic data sampled since 2003 (designated as “Station 

W1”). The broken vertical line indicates the beginning of the probabilistic data collection. 

Figure 3-9. Annual average chlorophyll a concentrations in Clearwater Harbor North. Individual fixed 

stations sampled between 1992 and 2002 and the probabilistic data sampled since 2003 (designated as 

“Station W2”). The broken vertical line indicates the beginning of the probabilistic data collection. 
17 

Figure 3-10. Annual average chlorophyll a concentrations in Clearwater Harbor South. Individual fixed 

stations sampled between 1992 and 2002 and the probabilistic data sampled since 2003 (designated as 

“Station W3”). The broken vertical line indicates the beginning of the probabilistic data collection. 

This information suggests that, while there is a difference in the average water quality among 

stations within a segment, water quality at these stations appears to respond similarly to common 

drivers of water quality within the segment on an annual time scale. Further, individual station 

averages tended to co-vary over time during the historic fixed station sampling period despite the 

different sampling frequencies between stations within a segment. This information is supporting 

evidence that the fixed station information may be generally representative of trends in water 

quality over time on an annual time scale and that variability within a segment is a significant 

attribute lending credence to the implementation of the probabilistic design which is more likely to 

represent the true average condition of the segment. 

The evidence provided by these descriptive plots suggests that all segments are currently meeting 

their designated use with respect to maintaining healthy chlorophyll a concentrations and thereby 

seagrass extent. Chlorophyll a concentrations have been declining in both Saint Joseph Sound and 

Clearwater Harbor North over time at the fixed station sites suggesting conditions have improved in 

these segments since the early 1990s while remaining stable in Clearwater Harbor South. 

For the purposes of the CHSJS CCMP, the estuary water quality goal was established to ensure that 

water quality conditions in the estuary are protective of seagrasses. Given that seagrasses are 

currently improving throughout the CHSJS estuary, it was concluded that recent water quality 

conditions are sufficient to maintain full aquatic life uses in the estuary. Therefore, a reference 

period approach was used to establish management targets and thresholds used to monitor water 

quality in the estuarine open bay waters of the CCMP. The reference period was defined as the 

2003-2009 time period. The Reference Period approach was used to establish the chlorophyll a 

targets and thresholds for the CHSJS segments. The Reference Period was defined as the population 

of data collected between 2003 and 2009 in Pinellas County’s monitoring strata “W1”, 

“W2”,”W3”, representing Saint Joseph Sound, Clearwater Harbor North, and Clearwater Harbor 
18 

South, respectively (Figure 3-7). The chlorophyll a targets for each segment (i.e., the annual 

geometric means for the reference period) as reported in Janicki Environmental (2011) are: 

 St, Joseph Sound 1.9 μg/L, 

 Clearwater Harbor North 3.5 μg/L, and 

 Clearwater Harbor South 4.8 μg/L. 

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 threshold value for these constituents was defined as a value that would indicate that water 

quality was significantly higher than that observed over the reference period. The threshold value 

was calculated based on statistical theory that if chlorophyll a concentrations in any year were not 

different from reference period conditions, its geometric average value would be lower than the 

reference period mean +1.96 times the standard deviation of the annual geometric averages with 

known confidence. The proposed chlorophyll a thresholds, expressed as annual geometric means, 

for each segment 

 St, Joseph Sound 3.1 μg/L, 

 Clearwater Harbor North 5.4 μg/L, and 

 Clearwater Harbor South 7.6 μg/L. 

4.0 Proposed Numeric Nutrient Criteria 

Quantitative statistical analyses suggested that neither nutrient concentrations nor nutrient loadings 

alone were confident predictors of the chlorophyll a concentrations used as an indicator of 

estuarine health (Janicki Environmental, 2011). While within-segment analysis did not reveal a 

direct link between nutrients and phytoplankton concentrations, descriptive plots suggested a 

north/south gradient in chlorophyll a concentrations that appeared to be principally a function of 

residence times. The direct influence of tidal exchange with the Gulf of Mexico is most pronounced 

in Saint Joseph Sound and least pronounced in Clearwater Harbor South. The increased residence 

time of water in the Clearwater Harbor South segment seemingly allows for a higher concentration 

of phytoplankton as shown in Figure 4-1. In this plot the chlorophyll a and TN concentrations are 

standardized so that they are on the same scale (i.e., units of standard deviation from their longterm average). Therefore, blue dots represent lower than average concentrations and red dots 

indicate higher than average concentrations. This suggests that other factors are likely influencing 

the theoretical stressor-response relationship between TN and chlorophyll a responses. 

A comparison of TN concentrations (Figure 4-2) suggests that TN concentrations were more similar 

between historical and recent data than observed in the chlorophyll a concentrations (Figure 3-6), 

especially in Clearwater Harbor North and Clearwater Harbor South. A Wilcoxon Rank Sum test 

suggests that statistically different distributions between the fixed and probabilistic data were only 

found in Saint Joseph Sound. This difference was likely due to the biased location of the fixed 

stations towards the southern end of the segment. 

Therefore, for the purposes of the CHSJS CCMP, the estuary water quality goal was established to 

ensure that water quality conditions in the estuary are protective of seagrasses. Given the results of 
19 

analysis described above, and the fact that seagrasses are currently improving throughout the CHSJS 

estuary, it was concluded that recent TN concentrations are sufficient to maintain full aquatic life 

uses in the estuary. Therefore, a reference period approach was used to establish management 

targets and thresholds used to monitor water quality in the estuarine open bay waters of the CCMP. 

The reference period was defined as the 2003-2009 time period. 

Figure 4-1. Spatial distribution of chlorophyll a (left) and TN (right). Red dots indicate significant clustering 

of higher than average values and blue dots indicate statistically lower than average values. 

Figure 4-2. Distribution of TN concentrations (mg/L) in historical fixed station “Fixed” and recent 

probabilistic “Random” data in all three CHSJS segments. 
20 

Both DEP and EPA have expressed a preference for criteria proposed as annual geometric averages. 

The geometric average is calculated by first using the natural log transformation of the raw data, 

calculating an average and then exponentiating that average to derive the geometric average. 

Target TN concentrations (mg/L) for each CHSJS estuarine segment were defined by the overall 

average of the annual geometric averages during the reference period. 

As discussed above, a distinction is made between a target, i.e., a desired TN concentration and a 

threshold, i.e., a TN concentration above which undesirable TN concentrations exist A threshold 

value for these constituents was defined as a value that would indicate that water quality was 

significantly higher than that observed over the reference period. The threshold value was 

calculated based on statistical theory that if TN concentrations in any year were not different from 

reference period conditions, its geometric average value would be lower than the reference period 

mean +1.96 times the standard deviation of the annual geometric averages with known 

confidence. The proposed segment-specific TN thresholds for each segment are: 

 St, Joseph Sound 0.66 mg/L, 

 Clearwater Harbor North 0.61 mg/L, and 

 Clearwater Harbor South 0.58 mg/L. 

The annual geometric means for chlorophyll a and TN should be derived strictly from water quality 

sampling according to Pinellas County’s probabilistic water quality sampling design for estuaries in 

their designated strata “W1”, “W2” , and “W3” corresponding to Saint Joseph Sound, Clearwater 

Harbor North and Clearwater Harbor South, respectively. These thresholds are not to be considered 

as end of pipe criteria for regulatory purposes. 

The proposed TN criteria will be used to evaluate water quality with respect to not allowing for 

degradation of water quality from that observed over recent time period (i.e., 2003-2009) when the 

open bay estuarine segments were fully meeting their designated uses. Within this context, an 

excursion is defined as when an annual geometric average for a particular constituent has exceeded 

the threshold value. However, a single excursion of the threshold value does not necessarily mean 

that there has been significant degradation of water quality as described in the next section on 

implementation. 

5.0 Implementation 

As described in the State of the Resource Report (Janicki Environmental, 2011), there have been 

times when estuarine water quality values for chlorophyll a and TN have historically exceeded the 

proposed threshold values while the estuarine waters were meeting full aquatic life uses. While it 

is known that there is a limit for nutrient inputs above which any estuary would become 

compromised in meeting its full aquatic support, without a defensible quantitative stressor-response 

relationship, this limit cannot be predicted. The reference period approach was used to provide 

potential numeric criteria for TN in keeping with EPA’s policies on anti-degradation given that these 

areas are of special significance with regard to their designation as aquatic preserves. 

The proposed compliance assessment strategy involves two steps. The initial step is the 

comparison of the annual geometric average chlorophyll a concentrations of each segment to the 

established chlorophyll a thresholds. Compliance is achieved if the geometric average is less than 

or equal to the chlorophyll a threshold value. The threshold TN concentrations can be used to test 
21 

a sample geometric mean for any given year for compliance with the established targets and 

thresholds. Any sample geometric mean higher than these values would then be considered an 

excursion. If the chlorophyll a threshold and TN threshold have been exceeded in more than two 

years during any five-year period, an assessment of the seagrass areal extent in that segment should 

be conducted. The justification for this “2-in-5 year” compliance assessment is summarized in 

Appendix B. 

Lastly, it is critical that the data collected to assess compliance with both chlorophyll a thresholds 

and TN criteria must be defensibly comparable, i.e., collected in a similar temporal and spatial 

manner to the data used to establish the thresholds and criteria. The annual geometric means for 

chlorophyll a and TN should be derived strictly from water quality sampling according to Pinellas 

County’s probabilistic water quality sampling design for estuaries in their designated strata “W1”, 

“W2” , and “W3” corresponding to Saint Joseph Sound, Clearwater Harbor North and Clearwater 

Harbor South, respectively. Again, these thresholds are not to be considered as end of pipe criteria 

for regulatory purposes. 

 
22 

6.0 References 

Florida Department of Environmental Protection (FDEP) website. 2011. 

http://www.dep.state.fl.us/water/wqssp/nutrients/index.htm

Janicki Environmental, Inc. 2003. A design of a surface water quality monitoring program for 

Pinellas County. Prepared for Pinellas County Environmental Resource Management division. 

Clearwater, FL. 

Janicki Environmental, Inc. 2011. State of the Resource Report for Clearwater Harbor and Saint 

Joseph Sound. Prepared for Pinellas County Department of Environment and Infrastructure. 

Clearwater, Florida.. 

Sokal, R. R. and F. J. Rohlf. 1981. Biometry. W.H Freeman and Company. New York. 
Appendix A. 

Site-Specific Information 

in Support of Establishing 

Numeric Nutrient Criteria in 

St. Joseph Sound, 

Clearwater Harbor, and 

Boca Ciega Bay 
Site-Specific Information 

in Support of Establishing 

Numeric Nutrient Criteria in 

St. Joseph Sound, 

Clearwater Harbor, and 

Boca Ciega Bay 

Division of Environmental Assessment and Restoration

Standards and Assessment Section

Florida Department of Environmental Protection

Tallahassee, FL 32399

October 6, 2010
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft ii October 2010

Table of Contents

Executive Summary ................................................................................................................. 1

Geographic and Physical Description....................................................................................... 3

Sources of Nutrients................................................................................................................ 7

Biological Summary............................................................................................................... 10

Submersed Aquatic Vegetation................................................................................................... 10

Epiphyte Loads on Seagrass........................................................................................................ 16

Phytoplankton Species Composition and Chlorophyll a ............................................................... 16

Macroalgal Species Composition and Biomass............................................................................ 17

Depth to Seagrass Targets.......................................................................................................... 18

Presence and Frequency of Harmful Algal Blooms....................................................................... 18

Coral or Hard‐Bottom Community Structure and Areal Extent..................................................... 18

Shellfish Production and Frequency/Duration of Bed Closures .................................................... 18

Quantification of Landings from Commercial/Recreational Fisheries .......................................... 19

Existing Local Biological Indices.................................................................................................. 19

Harmful Algal Blooms and Fish Kills............................................................................................ 19

Hypoxia...................................................................................................................................... 19

Other Biological Resources ......................................................................................................... 19

Water Quality Studies ........................................................................................................... 24

Existing Regional Nutrient Loading Models................................................................................. 30

Estuary Segments on the 303(d) Impaired Waters List ................................................................ 30

Numeric Nutrient Criteria Recommendations........................................................................ 39

References............................................................................................................................. 40

   
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft iii October 2010

List of Tables

Table 1a. Checklist of nutrient enrichment symptoms.................................................................................. 2

Table 1b.  Checklist of additional factors...................................................................................................... 3

Table 2a.  Geographic and land use information for St. Joseph Sound, Clearwater Harbor, and

Boca Ciega Bay. ............................................................................................................................. 5

Table 2b.  Detailed land use breakdown for St. Joseph Sound...................................................................... 6

Table 2c.  Detailed land use breakdown for Clearwater Harbor................................................................... 6

Table 3.  Median/mean values for sampling strata in western Pinellas County, 2004–08. Strata as

in Figure 1 (from Levy et al. 2009, Appendix A)........................................................................... 24

Table 4.  Maximum/minimum values for sampling strata in western Pinellas County, 2004–08.  

Strata as in Figure 1 (from Levy et al. 2009, Appendix A). .......................................................... 25

Table 5.  Verified impaired waterbodies that empty into St. Joseph Sound, Clearwater Harbor, or

Northern Boca Ciega Bay. ........................................................................................................... 35

List of Figures

Figure 1.  Open water assessment segments within Pinellas County.  This report discusses Strata

W1–W8 (Figure 5 from Levy et al. 2009)....................................................................................... 4

Figure 2.  Location of major watersheds contributing to Clearwater Harbor North and South and

St. Joseph Sound within Pinellas County (from Levy 2010). .......................................................... 8

Figure 3.  Annual freshwater flow (millions of gallons per year) from tributaries into Clearwater

Harbor and St. Joseph Sound, 2003–08 (from Levy 2010)............................................................. 9

Figure 4.  Annual loading of TP (tons per year) from tributaries to Clearwater Harbor and St.

Joseph Sound, 2003–08 (from Levy 2010)..................................................................................... 9

Figure 5.  Annual loading of TN (tons per year) from tributaries to Clearwater Harbor and St.

Joseph Sound, 2003–08 (from Levy 2010)................................................................................... 10

Figure 6.  Mapped SAV coverage in St. Joseph Sound, 2008 (data provided by SWFMWD).......................11

Figure 7.  Mapped SAV coverage in Clearwater Harbor, 2008 (data provided by SWFMWD). ..................12

Figure 8.  Mapped SAV coverage in Boca Ciega Bay, 2008 (data provided by SWFMWD).........................13

Figure 9.  Spatial representation of SAV species mean abundance per transect from two years of

stratified random sampling in St. Joseph Sound and Clearwater Harbor (Figure 10 from

Meyer and Levy 2008). ................................................................................................................ 15

Figure 10.  Spatial representation of SAV health, epibiont density, sediment type, and depth for

seagrass transects from two years of stratified random sampling in St. Joseph Sound

and Clearwater Harbor (Figure 14 from Meyer and Levy 2008). ................................................ 16

Figure 11.  Mean abundance of marine algae and the presence of scallops per transect from two

years of stratified random sampling in St. Joseph Sound and Clearwater Harbor (Figure

11 from Meyer and Levy 2008). .................................................................................................. 17

Figure 12.  Average charter angler pressure per day for St. Joseph Sound and Clearwater Harbor

(data from angler survey by FWC; maps by Janicki Environmental)........................................... 20

Figure 13.  Average private boat angler pressure per day for St. Joseph Sound and Clearwater

Harbor  (data from angler survey by FWC; maps by Janicki Environmental)..............................21
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft iv October 2010

Figure 14.  Average shore angler pressure per day for St. Joseph Sound and Clearwater Harbor

(data from angler survey by FWC; maps by Janicki Environmental)........................................... 22

Figure 15.  Pinellas County bottom DO (mg/L) interpolation map applying kriging using 2004–08

data (Figure 10c in Levy et al. 2009). .......................................................................................... 26

Figure 16.  Pinellas County chla (μg/L) interpolation map applying inverse distance weighting

using 2004–08 data (Figure 9c in Levy et al. 2009)..................................................................... 27

Figure 17.  Pinellas County transmissivity percent (at 660 nanometers [nm]) interpolation map

applying kriging using 2004–08 data (Figure 8c in Levy et al. 2009). ......................................... 28

Figure 18.  Mean chla and TN/TP ratios for St. Joseph Sound, 2003–08 (from Levy 2010). .......................29

Figure 19.  Mean chla and TN/TP ratios for Clearwater Harbor North, 1992–2008 (from Levy

2010). ..........................................................................................................................................29

Figure 20.  Mean chla and TN/TP ratios for Clearwater Harbor South, 1992–2008 (from Levy

2010). ..........................................................................................................................................30

Figure 21.  Pinellas County waters impaired for chla and Trophic State Index (TSI) (lakes) based

on FDEP 2009 Verified Lists and the 1998 303(d) list for the Group 1 and Group 5 basins

(Figure 3 in Levy et al. 2009). ...................................................................................................... 32

Figure 22.  Pinellas County waters impaired for DO based on FDEP 2009 Verified Lists and the

1998 303(d) list for the Group 1 and Group 5 basins (Figure 2 in Levy et al. 2009)....................33

Figure 23.  Pinellas County waters impaired for bacteria based on FDEP 2009 Verified Lists and

the 1998 303(d) list for the Group 1 and Group 5 basins (Figure 4 in Levy et al. 2009)..............34
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 1   October 2010

Executive Summary

This report was prepared by the Florida Department of Environmental Protection (FDEP), in cooperation

with the Pinellas County Department of Environmental Management (PCDEM),1 to support the

development of site‐specific numeric nutrient criteria for St. Joseph Sound, Clearwater Harbor, and Boca

Ciega Bay.  The primary purpose of the proposed numeric nutrient criteria is to protect healthy, well‐

balanced natural populations of flora and fauna from the effects of excess nutrient enrichment.   

Submersed aquatic vegetation (SAV), including seagrass and macroalgae, is the most nutrient‐sensitive

biological endpoint in St. Joseph Sound, Clearwater Harbor, and Boca Ciega Bay, and extensive water

quality and seagrass data have been collected for the system since 1992 (since 1950 for seagrass in Boca

Ciega Bay).  The portion of Pinellas County that borders these estuaries is heavily urbanized, and there

were historical impacts on water quality and SAV.   

Impacts from urbanization have been mitigated in recent decades; water clarity is generally good, and

SAV coverage is extensive in these areas.  St. Joseph Sound has lower chlorophyll a (chla) and a greater

percentage of SAV coverage than Clearwater Harbor or Boca Ciega Bay, portions of which are on the

303(d) list for chla.  The impaired segments of Clearwater Harbor and Boca Ciega Bay have longer

residence times and less contact with the Gulf of Mexico than the other estuaries in the area,

contributing to higher chla in those areas, even in the absence of urban influence.  Chla concentrations

have declined in the past two decades in the entire region, and SAV coverage has increased during that

time, likely due to nutrient control measures employed by county and city governments in the region.  

Based on the information in this report, aquatic life use is being fully supported in St. Joseph Sound,

northern Clearwater Harbor, and southern Boca Ciega Bay, and efforts are under way to attain fully

supported aquatic life use in southern Clearwater Harbor and northern Boca Ciega Bay.  Tables 1a and

1b provide a checklist of nutrient enrichment symptoms and additional factors, respectively.

Pinellas County has hired Janicki Environmental Inc., a consulting firm, to develop nutrient and

transparency targets for St. Joseph Sound and Clearwater Harbor.  That work is being overseen by the

Clearwater Harbor/St. Joseph Sound Comprehensive Conservation Management Plan (CCMP) Working

Group.  The anticipated completion date for the nutrient and transparency targets is late 2010.  FDEP

does not plan to propose numeric nutrient criteria for these regions until the Working Group completes

its work.  Nutrient loading targets have been set for southern Boca Ciega Bay as part of the Tampa Bay

Nitrogen Management Consortium, and FDEP supports those recommendations.  FDEP proposes that

the chla target for Lower Tampa Bay (5.1 micrograms per liter [μg/L]) be adopted for southern Boca

Ciega Bay.  Once Janicki Environmental has completed work on southern Clearwater Harbor, FDEP will

consider if the proposed criteria for that segment would also be appropriate for northern Boca Ciega

Bay.  FDEP will continue to work with PCDEM and the Tampa Bay Estuary Program (TBEP) to develop

numeric nutrient criteria for this region.     

   

                                                            

1 Contributors to this report include Kelli Levy (PCDEM) and Kris Kaufman (Southwest Florida Water Management District [SWFWMD]).
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 2   October 2010

Table 1a. Checklist of nutrient enrichment symptoms. ‐ = Empty cell/no data

Response Variable Observed

Historically?

Observed

Currently?

Explanation Source

Low dissolved

oxygen (DO)

(hypoxia/anoxia)

Yes Yes Some tidal creeks are on the 303(d) list for

DO.  In open waters, some areas have

bottom DO below 4 milligrams per liter

(mg/L) during warm months.

303(d) list;

Levy 2010

Reduced clarity   Yes No SAV loss from 1950 to 1982 likely due to

reduced clarity, but acreage has been

increasing for past 20 years.

SWFWMD

Increased chla

concentrations

Yes   No Historical loss of SAV likely related to chla;

however, concentrations have decreased

or remained constant since 1992.

Levy 2010

Phytoplankton

blooms (nuisance

or toxic)

Yes Yes Red tide (Karenia brevis blooms) is

common in this part of the coast.

‐ 

Problematic

epiphyte growth  

No No Epiphyte loads vary throughout the region,

but have not been related to nutrient levels

or considered problematic

Meyer and Levy

2008

Problematic

macroalgal growth

No No Macroalgae are a major component of the

submersed aquatic community, but not

considered problematic.

Meyer and Levy

2008

SAV community

changes or loss

Yes No Over 50% of SAV was lost in Boca Ciega Bay

from 1950 to 1982, and some loss likely

occurred in Clearwater Harbor.  SAV

coverage in Boca Ciega Bay rebounded to

80% former coverage in 2008.  SAV

coverage increased 16% between 1999 and

2008 in St. Joseph Sound and Clearwater

Harbor.  Losses occurred in all areas due to

dredging and filling as part of the

development of Pinellas County, and that

loss is considered permanent and not

related to nutrients or water clarity.   

K. Levy, PCDEM,

personal

communication;

SWFWMD SAV

data

Emergent or

shoreline

vegetation

community

changes or loss  

Yes  ‐  Much of the mainland shoreline has been

developed, so there are many seawalls and

little intact shoreline vegetation.  Analysis

by Janicki Environmental is ongoing.

‐ 

Coral/hard‐bottom

community

changes or loss  

Unknown ‐  There is some hard‐bottom community in

this area, but it has not been studied.  

‐ 

Impacts to benthic

community

Unknown  ‐  ‐ ‐ 

Fish kills   Yes, limited

in space and

time

‐  Fish kills have periodically occurred as a

result of red tide blooms and cold‐water

induced shock; however, no significant kills

have been reported as a direct result of

nutrient inputs into the estuary.

‐ 
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 3   October 2010

Table 1b.  Checklist of additional factors. ‐ = Empty cell/no dat

Nutrient Factors Observed? Explanation Source

Increased nutrient loading

or concentrations

No Historical increases, but nutrient loading

from humans has decreased in the past

10 years.  

Levy 2010

Difference between

nearshore and offshore

levels  

Unknown No data available for coastal area outside

barrier islands.

‐ 

Mitigating factors that

could prevent nutrient

expression

No ‐ ‐ 

Other significant stressors

to biological communities

No  ‐ ‐ 

Natural high‐nutrient

episodes (e.g., seasonal or  

event driven)

No ‐ ‐ 

  

Geographic and Physical Description

St. Joseph Sound, Clearwater Harbor, and Boca Ciega Bay are in western Pinellas County along the Gulf

side of the cities of St. Petersburg, Largo, Clearwater, Dunedin, and Tarpon Springs.  All three areas are

constricted to varying degrees by barrier islands (Figure 1).  St. Joseph Sound is well mixed with the Gulf

of Mexico; Clearwater Harbor is fairly well flushed in the northern end, but less so in the southern

portion; and Boca Ciega Bay has limited contact with the Gulf.  In Clearwater Harbor, water exchanges

with the Gulf of Mexico through Clearwater Pass (north end of southern half) and Hurricane Pass (north

end of northern half); Dunedin Pass (middle of northern half) has been closed.  Boca Ciega Bay

exchanges with the Gulf of Mexico through several limited passes.  These estuarine areas are part of the

Pinellas County Aquatic Preserve, and much of the barrier island area bordering St. Joseph Sound is

preserved as state parks (Anclote Key Preserve State Park, Honeymoon Island State Park, and Caladesi

Island State Park).  Table 2a provides physical information about these estuarine areas.

Pinellas County is 96% developed, with more natural areas in the northern portion of the county than

the southern (Tables 2b and 2c).  Barrier islands along the western boundary of Clearwater Harbor and

Boca Ciega Bay have been physically modified for development by dredging and filling to create finger

canals and extend the land for development.  PCDEM conducted a forum in March 2007 in which various

stakeholders presented information about the region’s history and resources, and a wealth of

information from that meeting is posted on the PCDEM website (available:  http://www.

pinellascounty.org/Environment/pagesHTML/watershedMngmt/wm8000.html).

Janicki Environmental submitted a proposal to Pinellas County for the development of a CCMP for

Clearwater Harbor and St. Joseph Sound (Janicki 2009).  That proposal was funded, contains a rich

description of the area, and is available on the Pinellas County Water Atlas website.  That project is

ongoing and will produce nutrient and chla targets for this region (available:  http://www.

pinellas.wateratlas.usf.edu/news/committees.asp?GROUPID=10050&ACTIVE=1).
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Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 5   October 2010

Table 2a.  Geographic and land use information for St. Joseph Sound, Clearwater Harbor, and Boca

Ciega Bay.   Note:  Most information is not yet complete for Boca Ciega Bay.

SJS = St. Joseph Sound; CWH = Clearwater Harbor

‐ = Empty cell/no data

Information Category Available Data Values Source

Estuarine surface area

(square kilometers

[km2])

‐  SJS–18,000 acres

CWH–10,000 acres Janicki 2009

Watershed area  

(km2

)

Pinellas County

Basin Shapefile

SJS–19,000 acres

CWH–27,000 acres

Janicki 2009

Land use SWFWMD

Land Use

Shapefile

SJS–(see Table 2b for a detailed breakdown of land

uses)

CWH–(see Table 2c for a detailed breakdown of land

uses)

SWFWMD

Mean depth  

(meters [m])

National

Geophysical

Data Center

(NGDC) Coastal

Relief Model

Clip Shapefile  

SJS–1.49 m

CWH–1.20 m

Florida Shelf

Habitat (FLASH)

Map Project, U.S.

Geological Survey

[USGS] 2007)

Volume  

(cubic meters [m3])

NGDC Coastal

Relief Model

Mean high water volume:

SJS–79,803,504 m3

CWH–44,389,219 m3

Mean low water volume:

SJS–43,388,254 m3

CWH–23,103,029 m3

FLASH Map Project,

USGS 2007)

Tidal range  

(m)

Pinellas County

tidal ranges

SJS–0.369 m above sea level (ASL) to 0.210 m below sea

level (BSL)

CWH–0.357 ASL to 0.192 BSL

Tidal freshwater inflow  

(1,000 cubic meters

per day [m3d‐1])

2004–08 flow

data  

SJS–2,090.765 (in 1,000 m3d‐1) (includes Smith Bayou

and Klosterman Bayou)

CWH–22,963.81 (in 1,000 m3d‐1) (includes Cedar Creek,

Curlew Creek, Spring Branch, Coastal Zones 1 and 4,

and McKay Creek)

Levy et al. 2008

Mean water residence

time  

(days)

No information currently exists.  This should be

developed in the CCMP for St. Joseph Sound and

Clearwater Harbor.

‐ 

Salinity and salinity

zones  

(parts per thousand

[ppt])

Salinity 2004–

08

SJS–Mean: 32.37 ppt; Range: 22.9‐38.4 ppt

CWH–Mean: 33.73 ppt; Range 25.1‐38.4 ppt

Levy et al. 2008

Transparency/

optical data

Total

suspended

solids (TSS),

turbidity,

transmissivity,

2004–08

Data in STORET and Water Atlas, summarized in Levy et

al. 2009, Appendix A.

Levy et al. 2009

Nutrient data Chla, 2004–08 Data in STORET and Water Atlas, summarized in Levy et

al. 2009, Appendix A.

Levy et al. 2009

Meter data   Surface and Data in STORET and Water Atlas, summarized in Levy et Levy et al. 2009
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 6   October 2010

Information Category Available Data Values Source

(DO, temperature,

salinity, pH)

bottom

readings for all

sampling

stations, 2004–

08

al. 2009, Appendix A.

Annual and seasonal

loading of total

nitrogen (TN) and total

phosphorus (TP)

Load estimates

for 2004–08

for each

subwatershed

SJS–Annual loads: TN: 5.43 tons/year; TP: 1.59

tons/year (includes Smith Bayou and Klosterman

Bayou)

CWH–Annual loads: TN: 39.62 tons/year; TP: 5.88

tons/year  (includes Cedar Creek, Curlew Creek, Spring

Branch, Coastal Zones 1 and 4, and McKay Creek)

Levy et al. 2009

Geographic

Information System

(GIS) interpolation

maps

Salinity,

bottom DO,

chla,

transmissivity,

2004–08

Data in STORET and Water Atlas, summarized in Levy et

al. 2009, Appendix A.

Levy et al. 2009

Drainage system   GIS files Asset management databases of contributing drainage

systems.

Pinellas County,

Tarpon Springs,

Clearwater,

Dunedin, Largo

Table 2b.  Detailed land use breakdown for St. Joseph Sound.  

Land Use Type Acreage %

Agriculture 11,645,481 11.82%

Commercial 6,234,270 6.33%

Natural 19,875,244 20.18%

Open/Disturbed Lands 4,290,692 4.36%

Recreational 5,175,804 5.25%

Reservoirs 1,435,166 1.46%

Residential 44,794,485 45.47%

Transportation 4,301,079 4.37%

Utilities 757,463 0.77%

Table 2c.  Detailed land use breakdown for Clearwater Harbor.

Land Use Type Acreage %

Agriculture 436,497 0.28%

Commercial 16,532,290 10.70%

Natural 4,785,361 3.10%

Open Land 1,200,600 0.78%

Recreational 7,875,260 5.10%

Reservoirs 2,177,998 1.41%

Residential 103,587,061 67.02%

Transportation 16,845,320 10.90%

Utilities 1,121,041 0.73%
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 7   October 2010

Sources of Nutrients  

Pinellas County forms the landward border of these estuarine areas.  It is a densely populated urban

area in which environmental resource managers have made efforts to reduce loading of nutrients to the

estuaries, as well as to Tampa Bay to the east.  Eight watersheds contribute fresh water to St. Joseph

Sound and Clearwater Harbor (Figure 2), and freshwater flow varies by year and by watershed (Figure 3).  

All wastewater treatment plants use advanced treatment (AWT) in Pinellas County, and much of the

wastewater is converted into reuse water for land application.  The whole county is hooked up to

sanitary sewer systems, so there are minimal inputs from septic tanks.  The conversion to AWT has

reduced nutrient loading in the past 10 years.   

A new county fertilizer ordinance should reduce nutrient inputs from urban stormwater sources.  Pet

waste is considered a large source of fecal coliform bacteria in some watersheds (Albright 2008; Kurisko

2008), so that may be a source of nutrients as well.  Pinellas County and municipalities within the county

have conducted numerous stormwater retrofit projects within the county.  Loadings of TN and TP to St.

Joseph Sound and Clearwater Harbor declined from 2003 to 2008 in most contributing basins (Figures 4

and 5; Levy 2010).  

   
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Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 10   October 2010

Figure 5.  Annual loading of TN (tons per year) from tributaries to Clearwater Harbor and St. Joseph

Sound, 2003–08 (from Levy 2010).

Biological Summary

Submersed Aquatic Vegetation

SAV, which consists of seagrass and macroalgae, is abundant in these bays and is the most sensitive

ecological endpoint.  Halodule wrightii is abundant and distributed throughout the region.  Thalassia

testudinum is abundant in St. Joseph Sound and Clearwater Harbor, but not as abundant in Boca Ciega

Bay.  Syringodium filiforme is abundant in St. Joseph Sound, but present in lower numbers in Clearwater

Harbor and Boca Ciega Bay.  St. Joseph Sound contains the greatest coverage of SAV, followed by

Clearwater Harbor and Boca Ciega Bay.  Clearwater Harbor and Boca Ciega Bay contain significant areas

that can no longer be colonized by SAV due to dredge‐and‐fill operations (K. Levy, PCDEM, personal

communication).   

SWFWMD performed aerial mapping of Clearwater Harbor and St. Joseph Sound in 1999, 2002, 2004,

2006, and 2008 (resolution of 0.5 acres and 80% ground‐truthing accuracy; map is of SAV, which

includes macroalgae).  Surveys were first conducted for Boca Ciega Bay in 1988 and nearly every 2 years

since.  The first SAV estimate (1999) was 13,994 acres, and 17,422 acres of seagrass were estimated for

2008, for a 16% increase (PCDEM).  In 2008, there were 12,639 acres of SAV in St. Joseph Sound (Figure

6), 3,784 acres in Clearwater Harbor North (Figure 7), and 1,000 acres in Clearwater Harbor South

(Figure 7; data from SWFWMD).   

Estimates of SAV acreage are available for Boca Ciega Bay in 1950, 1982, and then nearly every 2 years

from 1988 to 2008.  There were 10,800 acres of SAV in Boca Ciega Bay in 1950.  The area of SAV then

declined to 5,770 acres in 1982, but has been steadily increasing ever since, and totaled 8,457 acres in

2008 (Figure 8; data from SWFWMD).  That expansion was evident in data collected along fixed

transects by TBEP in Boca Ciega Bay from 1998 to 2009 (Avery et al. 2010; Appendix B).
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 11   October 2010

Figure 6.  Mapped SAV coverage in St. Joseph Sound, 2008 (data provided by SWFMWD).   
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 12   October 2010

Figure 7.  Mapped SAV coverage in Clearwater Harbor, 2008 (data provided by SWFMWD).   
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 13   October 2010

Figure 8.  Mapped SAV coverage in Boca Ciega Bay, 2008 (data provided by SWFMWD).   
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 14   October 2010

Meyer and Levy (2008) summarized results from PCDEM seagrass monitoring from 1998 to 2007, and

reported that seagrasses are stable.  PCDEM sampled fixed transects in St. Joseph Sound, Clearwater

Harbor, and Boca Ciega Bay from 1998 to 2005, and has employed a stratified random sampling design

in St. Joseph Sound and Clearwater Harbor from 2006 to the present.  During fixed transect sampling,

the following information was collected:  Braun‐Blanquet seagrass percent cover, water depth, sediment

composition, seagrass condition, and algae occurrence.  Sediment composition was qualitatively

categorized as sand, sandy mud, mud, shelly mud, shelly sand, or hard‐bottom. Seagrass condition was

qualitatively categorized as very good, good, fair, poor, or necrotic.  Epibiont density on the seagrass

blade was assessed using a numerical rating scale:  1= clean, 2= light coverage, 3= moderate, 4= heavy.

At the transect’s midbed and edge of bed, staff recorded shoot density and canopy height.  Three

density counts were made using either a 10x10 centimeter (cm) or 25x25 cm square frame.  Also, 5

shoot lengths were recorded to the nearest centimeter.  Samplers assessed each species independently.

Chla, turbidity, Hydrolab®, and LICOR® readings were taken at midbed, edge of bed, and the 2 m depth

contour.   

In their report of fixed transect SAV monitoring from 1998 to 2005, Meyer and Levy (2008) reported that

seagrass abundance and density remained relatively stable in all areas during the study period, although

there were some localized changes in bed length or shoot density.  Most changes were increases in bed

length or seagrass abundance, but there were some decreases in 2004 to 2005 that they attributed to

hurricanes (Meyer and Levy 2008).  

SAV data from the first 2 years of stratified random sampling were compared among strata for

Clearwater Harbor North and South and St. Joseph Sound) and depth categories (A = 0–0.6 m,  

B = 0.6–1.2 m, and C = >1.2 m) in Meyer and Levy (2008).  SAV covered most of the study area, but mean

abundance was greatest in St. Joseph Sound and least in Clearwater Harbor South.  Mean abundance in

Depth Zone A was 77%, significantly higher than the mean for Zone C, 37% (Meyer and Levy 2008).  The

3 main species of seagrass were distributed throughout the study area, but Syringodium was

significantly less abundant in Clearwater Harbor North and South than in St. Joseph Sound (Figure 9).  

Syringodium also had significantly greater abundance in Depth Zone B (19%) than in Zone A (7%), which

probably explains its greater abundance in deeper St. Joseph Sound.  Thalassia abundance was

significantly greater in Zone A (35%) than in B (14%) or C (6%).  Halodule was distributed throughout the

region, mainly in Zones A and B, with highest abundance in Clearwater Harbor North and the lowest in

St. Joseph Sound (Figure 9; Meyer and Levy 2008).  Seagrass health was typically good or fair throughout

the study area, with no clear pattern between strata (Figure 10).  Epibiont density was greatest in St.

Joseph Sound and in Zone B (Meyer and Levy 2008).  Upon visual inspection of the data, Clearwater

Harbor South had more transects with mud substrate (Figure 10).  
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Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 18   October 2010

Depth to Seagrass Targets

No depth targets have yet been established, but random sampling data shows that Halodule and

Syringodium colonize depths greater than 2 m in St. Joseph Sound and Clearwater Harbor (Figures 9 and

10; Meyer and Levy 2008).

Presence and Frequency of Harmful Algal Blooms

Red tide (K. brevis) occurs frequently in this area.  Since 2004 it has been found in January–February

2004, February–March 2005, June–October 2005, September–October 2006, and October 2008.  

Densities have varied from 1,000 to greater than 1,000,000 cells per liter during these blooms (PCDEM).  

Anecdotal accounts of red tide in this area date back to 1844  (Fish and Wildlife Research Institute

[FWRI] historical data, available:  http://research.myfwc.com/features/category_main.asp?id=2037).

The causes of red tide bloom and proliferation are still somewhat unknown, but the prevailing thought is

that the blooms begin offshore and can be supported closer to shore under certain conditions.  Controls

of bloom dynamics include physical parameters such as temperature and salinity, and nutrient form and

availability.  Evaluating the significance of a single factor is difficult (Vargo et al. 2008).  Vargo (2009)

reviewed the historical and current theories for K. brevis initiation and maintenance, and identified 24

hypotheses, falling into several main categories:  (1) rainfall and/or riverine flux; (2) benthos or benthic

flux; (3) water column hydrodynamics; and (4) chemical/allelopathy related.   

Vargo et al. (2004, 2008) evaluated many nutrient sources for their contributions to bloom initiation and

maintenance:  atmospheric deposition, estuarine flux, N‐fixation by the cyanobacteria Trichodesmium,

zooplankton excretion, benthic flux, and the decay of dead fish.  Atmospheric deposition and benthic

flux were found to be minor sources to N and P fluxes, while zooplankton and dead fish were possibly

significant contributors. The combined estuarine flux from Tampa Bay, Charlotte Harbor, and the

Caloosahatchee River was found to supply varying, but sometimes adequate, levels of N and P to

support K. brevis populations at moderate, but not high, biomass levels.   

Hu et al. (2006) studied riverine nutrient inputs for major estuaries on the west‐central Florida coast

(Peace, Caloosahatchee, Alafia, and Suwannee Rivers) and determined that estuarine nutrient flux, even

in a high‐discharge period following hurricanes (when nutrient concentrations also were elevated),

could not support significant blooms.  They suggested that submarine ground water discharge accounts

for the necessary missing nutrients and can initiate and sustain major bloom events off the coast of

west‐central Florida.  In the recent studies examining the role of various nutrient sources in supporting

K. brevis blooms, a combination of sources is required to maintain a high biomass blooms (>106 cells/L).  

Coral or Hard‐Bottom Community Structure and Areal Extent

This information has yet to be quantified to date, although the habitat is found in the region.  Some

information may be available based on observations taken during water quality sampling, and analysis

will be performed to the degree allowable based on empirical data as part of the CCMP (Janicki

Environmental 2009).  

Shellfish Production and Frequency/Duration of Bed Closures

St. Joseph Sound and Clearwater Harbor are not regulated shellfishing areas.  Oyster bars are present,

and scallop occurrence has been monitored for the past several years.  Scallops occur predominately in

St. Joseph Sound (85%) (36 out of 42 occurrences from 2007 to 2009), but were also found in the
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 19   October 2010

northern part of Clearwater Harbor (6 out of 42 occurrences; PCDEM unpublished data).  Scallops were

not surveyed in Boca Ciega Bay.

Quantification of Landings from Commercial/Recreational Fisheries

The Florida Fish and Wildlife Conservation Commission (FWC) measured angler pressure at 20 sites in St.

Joseph Sound and Clearwater Harbor.  Their angler survey distinguished between charter vessels,

recreational vessels, and shore fishing.  The results show that fishing is very much a part of the use of

these estuaries (Figures 12 through 14).

Existing Local Biological Indices

The Tampa Bay Benthic Index of macroinvertebrates has been applied in Boca Ciega Bay and perhaps

elsewhere in the area, but available data and studies were not mined before the publication of this

report.  No other biological indices have been developed for this area.

Harmful Algal Blooms and Fish Kills

Fish kills have been consistently reported for this region.  Most are related to red tide and extreme cold

events (available:  http://research.myfwc.com/gallery/view_category.asp?catid=1357&subcatid=3227).

Hypoxia

Preliminary information suggests that hypoxia does not appear to be a significant issue in this area.

Other Biological Resources

Mangrove islands, oyster bars, and mudflats comprise important habitat for more than 7,000 breeding

pairs of birds in Clearwater Harbor (Audubon of Florida 2009), supported by the resident fishery.

   
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 20   October 2010

Figure 12.  Average charter angler pressure per day for St. Joseph Sound and Clearwater Harbor (data

from angler survey by FWC; maps by Janicki Environmental).

   
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 21   October 2010

Figure 13.  Average private boat angler pressure per day for St. Joseph Sound and Clearwater Harbor  

(data from angler survey by FWC; maps by Janicki Environmental).

   
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 22   October 2010

Figure 14.  Average shore angler pressure per day for St. Joseph Sound and Clearwater Harbor (data

from angler survey by FWC; maps by Janicki Environmental).
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 23   October 2010

   
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 24   October 2010

Water Quality Studies

PCDEM monitors water quality throughout Pinellas County.  The PCDEM report of water quality results

from 2004 to 2008 (Levy et al. 2009) describes the monitoring program and summary results from that

period, and those results are reported in this section.  The PCDEM sampling program during this period

was a probabilistic design in which 32 to 36 sites in each unit (as shown in Figure 1) were sampled.  Four

samples were collected during each of the 8 to 9 sampling events.  Water samples were collected and

analyzed per FDEP Standard Operating Procedures (SOPs), with analysis done at a National

Environmental Laboratory Accreditation Conference (NELAC)‐certified lab.  Data were loaded into

Florida STORET.  The county maintains 14 stream flow gauges through the USGS and HDI, Inc.  The

sampling also included flow measurements at the remaining tributary sites that are not equipped with in

situ gauges.  The data from this effort are used to develop systemwide loading estimates.  PCDEM has

water quality data for Pinellas County waters from 1999 to 2003 from a fixed station monitoring

program (available:  http://www.pinellas.wateratlas.usf.edu/).  

Spatial interpolation analysis of PCDEM data from 2004 to 2008 shows the spatial distribution of DO,

chla, and transmissivity in open waters of Pinellas County (Figures 15 through 17).  Southern Clearwater

Harbor, the Narrows, and North and Central Boca Ciega Bay (W3 through W7) do not have as much

direct contact with the Gulf of Mexico as the far northern and southern areas, resulting in higher

salinities, lower DO, and higher chla during either the wet or dry season (Levy et al. 2009).  Chla

concentrations are low (< 8 μg/L) in all areas during the dry/cool season (October–May; Figure 16).  

During the wet/hot season (June–September), chla concentrations are low (< 4 μg/L) in St. Joseph Sound

and moderate in Clearwater Harbor (4 to  11 μg/L) and Boca Ciega Bay (6 to 15 μg/L) (Figure 16).  Mean

chla concentrations have declined over the period of record for St. Joseph Sound, Clearwater Harbor

North, and Clearwater Harbor South, concomitant with changes in the ratio of TN to TP (Figures 18

through 20).  Long‐term chla data are still being evaluated for Boca Ciega Bay, and for TN and TP in all

areas.  Tables 3 and 4 list the median/mean and maximum/minimum values, respectively, for sampling

strata in western Pinellas County from 2004 to 2008.

The lower DO and higher chla in the middle part of western Pinellas County (W3, W4, W5, W6) are likely

due to larger watersheds feeding into those estuarine areas and the greater restriction of flow between

those areas and the Gulf of Mexico (Levy et al. 2009).  These areas correspond to the lowest SAV

coverage and the highest density of development and dredge‐and‐fill operations.

Table 3.  Median/mean values for sampling strata in western Pinellas County, 2004–08. Strata as in

Figure 1 (from Levy et al. 2009, Appendix A).

NTU = Nephelometric turbidity unit

Site Bottom DO

(mg/L)

Chla

(μg/L)

TSS

(mg/L)

Turbidity

(NTU)

Transmittance

(%)

W1 6.65 / 6.70 2.3 / 1.4 14 / 12 1.6 / 1.2 88.36 / 91.53

W2 6.24 / 6.35 3.9 / 3.0 13 / 13 2.7 / 2.3 81.48 / 82.30

W3 5.96 / 5.98 5.0 / 4.1 15 / 14 3.6 / 2.6 75.67 / 78.78

W4 5.80 / 5.74 7.5 / 6.4 18 / 17 5.4 / 4.4 63.88 / 62.61

W5 4.88 / 4.54 13.1 / 7.5 13 / 12 4.3 / 3.6 64.91 / 69.25

W6 6.31 / 6.16 6.2 / 5.6 15 / 14 3.8 / 3.1 73.17 / 73.65

W7 6.04 / 6.27 6.5 / 6.0 16 / 15 3.6 / 2.6 73.19 / 74.58

W8 6.64 / 6.45 4.7 / 4.0 14 / 14 2.4 / 1.8 81.43 / 83.18
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 25   October 2010

Table 4.  Maximum/minimum values for sampling strata in western Pinellas County, 2004–08.  Strata

as in Figure 1 (from Levy et al. 2009, Appendix A).

Site Bottom DO

(mg/L)

Chla

(μg/L)

TSS

(mg/L)

Turbidity

(NTU)

Transmittance

(%)

W1 13.28 / 2.67 18.9 / 0.3 106 / 1 5.9 / 0.3 99.46 / 47.72

W2 13.03 / 1.54 13.3 / 0.3 41 / 2 15.0 / 0.7 97.02 / 55.98

W3 8.79 / 0.81 17.2 / 0.3 66 / 3 54.0 / 0.6 97.19 / 14.31

W4 11.97 / 0.19 31.8 / 0.5 43 / 1 23.0 / 1.0 91.52 / 20.70

W5 12.10 / 1.01 105.0 / 0.8 58 / 2 26.0 / 0.1 93.07 / 3.21

W6 12.76 / 0.29 31.9 / 0.3 40 / 3 19.0 / 0.2 94.77 / 33.00

W7 12.40 / 0.12 36.9 / 0.3 39 / 2 15.0 / 0.4 97.16 / 32.37

W8 13.87 / 1.58 35.5 / 0.3 34 / 1 18.0 / 0.4 97.47 / 43.48
Nutrient C

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DO (mg/L) in

St. Josep

26

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data (Figure

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St. Josep

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Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 29   October 2010

Figure 18.  Mean chla and TN/TP ratios for St. Joseph Sound, 2003–08 (from Levy 2010).

Figure 19.  Mean chla and TN/TP ratios for Clearwater Harbor North, 1992–2008 (from Levy 2010).
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 30   October 2010

Figure 20.  Mean chla and TN/TP ratios for Clearwater Harbor South, 1992–2008 (from Levy 2010).

Existing Regional Nutrient Loading Models  

Janicki Environmental (2008) developed loading models for the Tampa Bay Estuary and is developing

loading models for this region under the CCMP (Janicki 2009).

Estuary Segments on the 303(d) Impaired Waters List

Several estuarine waterbodies are on the 303(d) list for chla, DO, or fecal coliform bacteria (Figures 21

through 23).  Table 5 lists the segments with waterbody identification (WBID) numbers classified as

“estuary” that are impaired for some analyte on the 303(d) list.  All of the listed impairments are for

stream WBIDs that are within urban areas; none of the open estuary areas are impaired.  Three WBIDs

are listed for fecal coliform exceedances, and five are listed for DO and nutrients (chla) (Table 5).   

Total Maximum Daily Loads (TMDLs) have been established for fecal coliforms in tidal portions of

Klosterman Bayou, which empties to St. Joseph Sound (Albright 2008), and in St. Joe Creek, which

empties into Boca Ciega Bay (Kurisko 2008).  Potential coliform sources include reclaimed water and

municipal stormwater.  The watershed is almost exclusively urban residential, so domestic animals likely

contribute to high fecal coliform values.  All residents in the watershed are on the sanitary sewer

system.

The use of fecal coliforms as indicators of the presence of human pathogens has been under scrutiny in

Florida for the past decade.  One of the priorities of the Gulf of Mexico Alliance (GOMA) is the need to

improve microbial source tracking (MST) and pathogen‐detection methods for use under Gulf of Mexico

conditions (GOMA 2009).  The GOMA Pathogens Workgroup recently submitted comments regarding

the status of U.S. Environmental Protection Agency (EPA) recreational water quality criteria (GOMA

2009).  The workgroup expressed concern that the EPA recreational criteria were derived in places that

do not represent Gulf of Mexico conditions, and that the use of fecal indicators was not appropriate for

waters primarily influenced by animal sources.  Areas in the Gulf of Mexico for which they thought the
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 31   October 2010

EPA criteria may not be appropriate included low‐population‐density coastal areas, areas of heavy

rainfall, subtropical latitudes, and areas where waters contain a large amount of organic detritus

material and/or colored dissolved organic matter (CDOM) (GOMA 2009).  Boehm et al. (2009) express

similar concern about the current and proposed recreational criteria, and specifically call attention to

the need for further research and revision in tropical waters and waters adversely impacted by urban

runoff and animal feces.  This is not to say that fecal coliform and Enterococci bacteria cannot indicate

human sources or cannot co‐occur with nutrient inputs; this suggests that there is ample evidence to

caution against assuming that the presence of these bacteria automatically indicates the presence of

anthropogenic nutrients.
Nutrient C

Draft

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St. Josep

32

chla and Tro

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St. Josep

34

bacteria bas

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Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater 

Draft 35 

Table 5. Verified impaired waterbodies that empty into St. Joseph Sound, Clearwater Harbor, or Northern Boca Ciega B

WaterbodyID(WBID)

WaterbodySegment

ParametersAssessed Usingthe 2001ImpairedSurface WatersRule (IWR)

ConcentrationCausingImpairment

Priority for TMDLDevelopment

Comments(# Exceedances/# Samples)PP = Planning Period VP = Verified Pe

1508 KLOSTERMAN

BAYOU

Coliform(Fecal Coliform)

> 400 coloniesper 100milliliters(colonies/100mL)

High PP = 6/57; VP = 7/37

1508 KLOSTERMAN

BAYOU

DO < 4.0 mg/L High PP = 71/350; VP = 49/231 Verified imp

identified as causative pollutant based 

impairment verification.

1508 KLOSTERMAN

BAYOU

Nutrients(chla andHistoric chla[histchla])

Median TN =1.665 mg/L

High PP = Potentially impaired; VP = Verifie

average chla values exceeded 11 g/L values were 27.9, 32.44, 30.02, 22.67, g/L, respectively. For historical listinvalues in verified period exceeded minaverage value of 21.12 g/L for 1990–2004 (38.14 g/L) and 2005 (45.28 gbased on median TN/TP ratio of 3.16 period TN median = 1.665 (134 values(150 values), and biochemical oxygen 3.25 mg/L (106 values).

1538 CURLEW

CREEK TIDAL

DO < 4.0 mg/L High PP = 56/350; VP = 28/71 Verified impa

identified as causative pollutant based 

impairment verification.

1538 CURLEW

CREEK TIDAL

Nutrients(chla)

Median TN =1.65 mg/L

High PP = No data; VP = 33 / 62 Verified im

Chla values exceeded 11 g/L in all yevalues were 27.29, 32.09, 35.35, 15.15respectively. N is limiting nutrient basratio of 7.9 (67 values). Verified perio(68 values), TP median = 0.22 mg/L (6median = 2.6 mg/L (47 values).

1556 CEDAR CREEK DO < 4.0 mg/L High PP = 64/221; VP = 42/82 Verified impa
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater 

Draft 36 

WaterbodyID(WBID)

WaterbodySegment

ParametersAssessed Usingthe 2001ImpairedSurface WatersRule (IWR)

ConcentrationCausingImpairment

Priority for TMDLDevelopment

Comments(# Exceedances/# Samples)PP = Planning Period VP = Verified Pe

(TIDAL) identified as causative pollutant based 

impairment verification.

1556 CEDAR CREEK

(TIDAL)

Nutrients(chla)

Median TN =1.05 mg/L

High PP = Potentially impaired; VP = Verifie

average chla values exceeded 11 g/L values were 13.91, 31.74, 12.85, 23.44g/L, respectively. N is limiting nutrieTN/TP ratio of 6.89 (69 values). Verifi1.05 mg/L (69 values), TP median = 0.BOD median = 3 mg/L (47 values).

1567 STEVENSON

CREEK (TIDAL

SEGMENT)

DO < 4.0 mg/L High PP = 141/408; VP = 77/212 Verified im

identified as causative pollutant based 

impairment verification.

1567 STEVENSON

CREEK (TIDALSEGMENT)

Nutrients(chla)

Median TN =1.29 mg/L

High PP = Potentially impaired; VP = Verifie

average chla values exceeded 11 g/L and values were 16.08, 32.74, 59.37, 2respectively. N is limiting nutrient basratio of 5.79 (116 values). Verified pemg/L (117 values), TP median = 0.22 mBOD median = 2 mg/L (92 values).

1633 MCKAY CREEK

(TIDAL)

Coliform(Fecal Coliform)

> 400

colonies/100mL

High PP = 34/36; VP = 1/11; Sufficient PP/V

most recent 20 samples (9/20) trigger 

based on period of record data.

1633 MCKAY CREEK

(TIDAL)

DO < 4.0 mg/L High PP = 119/572; VP = 39/60 Verified imp

identified as causative pollutant based impairment verification.

1633 MCKAY CREEK

(TIDAL)

Nutrients(chla)

Median TN =

1.04 mg/L

High PP = No data; VP = 23 / 58 Verified im

chla values exceeded 11 g/L in 1999–

and values were 12.22, 13.85, 11.48 a

respectively. N is limiting nutrient bas

(56 values). Verified period TN media

TP median = 0.2 (61 values), and BOD 
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater 

Draft 37 

WaterbodyID(WBID)

WaterbodySegment

ParametersAssessed Usingthe 2001ImpairedSurface WatersRule (IWR)

ConcentrationCausingImpairment

Priority for TMDLDevelopment

Comments(# Exceedances/# Samples)PP = Planning Period VP = Verified Pe

1641 CROSS CANAL

(SOUTH)

Coliform(Fecal Coliform)

> 400colonies/100mL

Low PP = 16/36; VP = 16/40.

1641 CROSS CANAL

(SOUTH)

DO < 4.0 mg/L Medium PP = 75/398; VP = 73/315 Verified Imp

identified as causative pollutant based 

impairment verification.

1641 CROSS CANAL

(SOUTH)

Nutrients(chla)

Median TN =1.11 mg/L

Medium PP = Potentially impaired; VP = Verifie

average chla values exceeded 11 g/L and values were 17.75, 14.84, 12.34, 1g/L, respectively. N is limiting nutrieTN/TP ratio of 6.98 (150 values). Veri1.11 mg/L (152 values), TP median = 0and BOD median = 2 mg/L (123 values

1662 PINELLAS

PARK DITCH

NO 1 (TIDAL

SEGMENT)

Coliform

(Fecal Coliform)

> 400colonies/100mL

High PP = 8/12; VP = 2/10; Sufficient PP/VP 

"PP+VP" sample exceedance rates trig

10/22), and period of record data sho

exceedances in 2006. Area is highly de

based on period of record data.

1662 PINELLAS

PARK DITCHNO 1 (TIDALSEGMENT)

DO < 4.0 mg/L High PP = 6 / 23; VP = 3 / 11; PP+VP provid

Combined PP+VP dataset yields 9/22, recent 20 samples = 8/20. Both exceeverification. Area is highly developedperiod of record data.

1701 BEAR CREEK Coliform

(Fecal Coliform)

> 400colonies/100mL

Low PP = 31/37; VP = No data; Sufficient P

assess. Area has been largely built ou

Assessment based on period of record 

1701 BEAR CREEK DO < 5.0 mg/L Medium PP = 102/346; VP = 58/171 Verified im

sufficient number of DO violations to List for DO. However, unable to link lopollutant (BOD or nutrients).

1716 CLAM BAYOU DO < 4.0 mg/L High PP = 2/4; VP = 5/8 Verified impaired. 
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater 

Draft 38 

WaterbodyID(WBID)

WaterbodySegment

ParametersAssessed Usingthe 2001ImpairedSurface WatersRule (IWR)

ConcentrationCausingImpairment

Priority for TMDLDevelopment

Comments(# Exceedances/# Samples)PP = Planning Period VP = Verified Pe

DRAIN (TIDAL) as causative pollutant. Verified period 

(5 values), TP median = 0.14 (5 values

mg/L (7 values).

1618C LONG

BAYOU/CROSSBAYOU

DO < 4.0 mg/L Medium PP = 17/67; VP = 43/210 Verified impa

identified as causative pollutant based impairment verification.

1618C LONG

BAYOU/CROSSBAYOU

Nutrients(chla)

Median TN =

0.96 mg/L

Medium PP = Potentially impaired; VP = Verifie

average chla values exceeded 11 g/L 

were 19.92, 11.25, and 16.73 g/L, re

nutrient based on median TN/TP ratio 

Verified period TN median = 0.96 mg/= 0.17 mg/L (114 values), BOD median 

1668E ST JOE CREEK

(TIDALSEGMENT)

DO < 4.0 mg/L Medium PP = 45/197; VP = 33/122 Verified Im

BOD were identified as causative polludata/nutrient impairment verification

1668E ST JOE CREEK

(TIDALSEGMENT)

Nutrients(chla and

histchla)

Median TN =

1.14 mg/L

Medium PP = Potentially impaired; VP = Verifie

average chla values exceeded 11 g/L 

and values were 40.48, 26.65, 21.1, 23

respectively. For historical listing, ann

verified period exceeded minimum hi

value of 16.31 g/L for 1990–94 by m

consecutive years in 1999 (40.48 g/L

N is limiting nutrient based on median 

values). Verified period TN median = 

median = 0.18 mg/L (66 values), and 

(52 BOD values).
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 39   October 2010

Numeric Nutrient Criteria Recommendations

Water quality targets for SAV protection are being established for St. Joseph Sound and Clearwater

Harbor by Janicki Environmental.  Their work is incorporating water quality data, loading estimates, and

the protection of SAV, fish, birds, and other uses.  FDEP does not plan to propose numeric nutrient

criteria for these regions until their work is complete.   

Nutrient loading targets have been set for southern Boca Ciega Bay as part of the Tampa Bay Nitrogen

Management Consortium (TBNMC), and FDEP supports those recommendations.  Northern Boca Ciega

Bay is similar to southern Clearwater Harbor in physical and chemical characteristics, and it may be

appropriate to adopt the same criteria for both areas.  TBNMC has proposed a chla target of  

5.1 μg/L for Lower Tampa Bay, which is adjacent to southern Boca Ciega Bay.  FDEP will evaluate

whether that target would be an appropriate criterion for southern Boca Ciega Bay.  FDEP welcomes

comments from stakeholders on these ideas, and will continue to work with PCDEM and TBEP to

develop numeric nutrient criteria for this region.
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 40   October 2010

References

Albright, J. 2008.  Fecal coliform TMDL for the Klosterman Bayou tidal segment, WBID 1508. Tallahassee,

FL:  Florida Department of Environmental Protection.  Available:  http://www.dep.state.fl.us/

water/tmdl/docs/tmdls/final/gp5/klosterman‐bayou‐tidal‐fc_tmdl.pdf.

Audubon of Florida.  2009. Birds and Birding:  Florida’s imperiled birds.  Available:  

http://fl.audubon.org/birds_imperiled_colonial.html.

Avery, W.M, K.B. Hennenfent, J.O.R. Johansson, and J.J. Pacowta.  2010.  Draft Tampa Bay Interagency

Seagrass Monitoring Program training and field manual.  Submitted to the Tampa Bay Estuary

Program, July 1, 2010.  Bay Study Group, City of Tampa.  Available:  http://www.tbeptech.org/

DATA/GIS/Seagrass/COT_Draft_Seagrass_Transect_Training_Document.pdf.

Boehm, A.B., N.J. Ashbold, J.M. Colford, Jr., L.E. Dunbar, L.E. Fleming, and M.A. Gold et al. 2009. A sea

change ahead for recreational water quality criteria.  Journal of Water and Health 07.1: 9‐20.

Gulf of Mexico Alliance (GOMA).  2009.  Comments regarding pending EPA Clean Water Act,

Recreational Water Quality Criteria.  Prepared for the U.S. Environmental Protection Agency

Stakeholders Workshop, October 6‐7, 2009, Chicago, IL.   

Hamm, D.C.  1975.  Benthic algae of the Anclote River Estuary.  Masters thesis, University of South

Florida.  

Hu, C., F. Muller‐Karger, and P.W. Swarzenski.  2006.  Hurricanes, submarine groundwater discharge and

west Florida's red tides.  Geophys. Res. Lett. 33.  

Janicki Environmental, Inc.  2008.  Estimates of total nitrogen, total phosphorus, total suspended solids,

and biochemical oxygen demand Loadings to Tampa Bay, Florida: 2004–2007. Prepared for the

Florida Department of Environmental Protection, Tallahassee, FL.

———.  2009.  Development of a Comprehensive Conservation Management Plan for Clearwater Harbor

and St. Joseph Sound.  Submitted to Pinellas County, March 31, 2009.  Available:  http://www.

pinellas.wateratlas.usf.edu/news/committees.asp?GROUPID=10050&ACTIVE=1.  

Johansson, J.O.R.  1975.  Phytoplankton standing crop in the Anclote River estuary.  Masters thesis,

University of South Florida.  

Kurisko, P.C. 2008.  Fecal coliform TMDL for Saint Joes Creek, WBID 1668A.  Tallahassee, FL:  Florida

Department of Environmental Protection.  Available:  http://www.dep.state.fl.us/water/tmdl/

docs/tmdls/final/gp5/st‐joes‐crk‐fc_tmdl.pdf.

Levy, K.H.  2010.  Presentation at numeric nutrient criteria development public meeting in St. Petersburg,

February 4, 2010.  Pinellas County Department of Environmental Management.  

Levy, K.H., M. Flock, and R. Burnes.  2009.  Ambient Monitoring Program annual report 2004–2008.  

Pinellas County Environmental Management Water Resources, Watershed Management

Division.  Available:  http://www.pinellascounty.org/Environment/pagesHTML/

waterResources/wr1000.html.

Meyer, C.A. and K.H. Levy.  2008.  Pinellas County Seagrass Resource Assessment and Monitoring

Program status report 1998‐2007.  Pinellas County Environmental Management Water

Resources.  Available:  http://www.pinellascounty.org/Environment/pagesHTML/

waterResources/wr6000.html.
Nutrient Criteria Technical Support Document St. Joseph Sound, Clearwater Harbor, Boca Ciega Bay

Draft 41   October 2010

Vargo, G.A.  2009.  A brief summary of the physiology and ecology of Karenia brevis Davis (G. Hansen

and Moestrup comb. nov.) red tides on the West Florida Shelf and of hypotheses posed for their

initiation, growth, maintenance, and termination.  Harmful Algae 8, 573‐584.   

Vargo G.A., C.A. Heil, D.N. Ault, and M.B. Neely.  2004.  Four Karenia brevis blooms: A comparative

analysis.  In:  K.A. Steidinger, J.H. Landsberg, C.R. Tomas, and G.A. Vargo (Eds.), Harmful algae

2002 (St. Petersburg, FL:  Florida Fish and Wildlife Conservation Commission, Florida Institute of

Oceanography and Intergovernmental Oceanographic Commission of the United Nations

Educational, Scientific and Cultural Organization [UNESCO], pp. 14–16).    

Vargo, G.A., C.A. Heil, K.A. Fanning, L.K. Dixon, M.B. Neely, and K.A. Lester et al.  2008.  Nutrient

availability in support of Karenia brevis blooms on the central West Florida Shelf: What keeps

Karenia blooming?  Cont. Shelf Res. 28, 73–98.
APPENDIX B. 

Implementation Issues: 

Targets, Thresholds, Type I Error and 

Compliance Assessment for Numeric Nutrient Criteria 

Using the Reference Period Approach 

Background 

Site specific numeric nutrient criteria for individual estuarine water bodies in southwest Florida 

from Saint Joseph Sound in Clearwater, Florida through Estero Bay, Florida are being proposed as 

alternatives to the application of regional or state wide model based standards. These site specific 

criteria rely on the identification of a response endpoint and the endpoint defined for these 

estuaries has been defined as a threshold chlorophyll a concentration in all cases. The temporal 

scale has been defined as yearly; therefore, the assessment statistic is an annual average chlorophyll 

a concentration. Generally, the geometric annual average is used; however, in cases where the data 

are first averaged monthly, a simple arithmetic average is used. These threshold chlorophyll a

concentrations for all estuaries have been identified using a reference period approach. Subsequent 

numeric nutrient criteria have been developed either by applying a stressor response relationship 

between nutrients and chlorophyll a concentrations, or by simply calculating an average of the 

annual averages of the reference period. 

The reference period approach relies on the identification of a period in time when these estuarine 

water bodies were sufficient to support full aquatic life uses. The overarching logic is that, provided 

a reliable stressor response model cannot be developed to accurately predict that point at which a 

system would no longer meet its full aquatic life use, water quality conditions during of a period in 

time when that waterbody was meeting its designated use would be protective of full aquatic life 

uses. For example, the estuarine open water segment of Saint Joseph Sound has been meeting full 

aquatic life uses according to FDEP water quality standards and the Impaired Waters Rule since 

2003. This means that chlorophyll a concentrations (Chla) have been below an annual average of 

11 μg/L and dissolved oxygen concentrations (DO) have been above 4 mg/L in at least 90% of the 

samples. These “endpoints” (i.e., Chla and DO) are typical indicators used to assess the health of 

estuarine waters. The period of time between 2003 and 2009 was therefore chosen as the reference 

period for Saint Joseph Sound. 

To establish numeric nutrient criteria using the reference period approach, a period of time would 

be identified when the waterbody was meeting its designated use, parameters would be defined to 

characterize the population of water quality values for chlorophyll a, total nitrogen (TN) and total 

phosphorus (TP) during that time, and then threshold values would be defined to represent a 

deviation from the expected condition of the reference period. The following paragraphs provide 

an example of how targets, thresholds and the type I error, and compliance assessment procedures 

have been established using the reference period approach. 

Reference Period Example 

To begin this example, a hypothetical reference period distribution of chlorophyll a concentrations 

was generated. Chlorophyll a concentrations in estuaries typically exhibit “lognormal” distribution 
character

becomes

lognorma

and a sta

in Figure

correspon

Protectio

geometric

chloroph

hypothet

Given th

product o

from the

obtain th

selecting

close to t

know tha

annual av

of annua

expected

ristics. This 

normally d

al distributio

ndard deviat

e 1. Once t

nding to the

n (FDEP) an

c means as

yll a, we no

ical evaluatio

e theoretica

of a typical 

distribution

he geometric

12 samples

the overall a

at variability 

verages from

l averages is

. 

Fi

implies that 

distributed w

n of chlorop

tion of 4.49 

he data are

normal distr

nd the Enviro

 regulatory 

ow consider

on and back

l distribution

monitoring p

of log value

c mean. F

and calcula

average of th

will exist du

m the referenc

s centered o

igure 1. Simu

when a natu

which confor

phyll a conc

μg/L. This d

natural log

ribution (Figu

onmental Pr

statistics fo

the log tran

transform th

n of Figure 

program. Fo

es, and calc

urther, we c

ting the aver

e reference 

ue to samplin

ce period dis

n a value ve

ulated distribu

ural log trans

rms to most

centrations w

istribution co

g transformed

ure 2). Since

rotection Ag

or parameter

nsformed val

he averages to

2, we can g

or example, 

culate an ave

can repeat 

rage of the l

period since

ng. For exam

stribution. A

ery close to

ution of chloro

sformation is

t parametric

was simulate

omposed of

d, the distri

 the Florida 

gency (EPA) 

rs with logn

ues to repre

o obtain the

generate ann

we can rand

erage and ba

this experim

og values. W

e it is a rando

mple, in Figu

s can be see

the overall 

ophyll a conc

s applied to t

statistical te

d using a m

10000 obse

bution beco

Department

have propo

normal distr

esent the dat

geometric m

nual average

domly selec

ack transform

ment many 

We expect ea

om sub-sam

ure 3, we ha

en in Figure 3

average in F

centrations. 

the distributi

ests. Therefo

mean of 6.75

ervations is sh

omes bell sh

of Environm

sed using an

ributions suc

ta underlying

means. 

es to simulat

ct 12 observa

m that avera

times, each

ach average 

ple, howeve

ave generated

3, the distrib

Figure 2 wh

ion, it 

ore, a 

5 μg/L 

hown 

haped 

mental 

nnual 

ch as 

g this 

te the 

ations 

age to 

time 

to be 

er, we 

d 100 

bution 

ich is 
Figu

Figure 3.

re 2. Distribu

 Distribution

tion of the na

 of 100 annua

tural log tran

l averages of

sformed valu

f the log trans

per year. 

ues of the sim

sformed chlor

ulated distrib

ophyll values

ution above.

 using 12 samples 
To derive

3. This di

Targets a

Once the

targets an

 

The refer

geometric

to the re

However

populatio

can be c

averages

value to 

was from

Using the

standard 

deviation

distributio

exceed to

distributio

e the geomet

istribution is

Figure 4. Geo

and Threshol

e geometric m

nd threshold

rence period

c means. Tha

eference peri

r, it can be 

on ranges be

considered a

of the refere

represent an

m the same 

e z table of 

deviation of

n of the popu

on that defin

o reject the

on that thres

tric annual a

shown in Fig

ometric mean

ds 

means have 

ds for this the

d target for 

at is, 5.947 μ

iod conditio

seen from F

etween 3.9 μ

a population

ence period.

n annual ave

population a

standard sta

f the distribu

ulation of geo

nes with 95%

hypothesis 

shold value e

averages, we

gure 4. 

ns taken from 

been calcula

eoretical refe

this distribut

μg/L is our go

on we identi

Figure 4 that

μg/L and 8.3

n of values

 Based on n

erage above 

as the refere

atistical tests,

ution in Figu

ometric mea

% confidence

that it belo

equals 7.59 μ

e simply back

the simulated

ated we have

rence period

tion can be

oal for the w

fied as bein

t the distribu

μg/L. There

that represe

normal distri

which we w

ence period 

, only 5% o

ure 4 would

ns. Therefor

e what value

onged to the

μg/L. 

k transform t

d chlorophyll 

e all the info

d distribution

defined as t

water body to

ng indicative

ution of ann

efore, the dis

ent the exp

bution theor

would reject 

distribution

of a normal d

d lie above t

re, a thresho

e a given ge

e reference 

the annual a

concentration

ormation nec

n. 

the overall a

o ensure that

e of full aqu

ual geometr

stribution of

pected distrib

ry, we can a

the hypothe

of annual g

distribution 

the mean+1

old can be co

eometric mea

period distri

averages of F

ns above. 

cessary to dev

average of a

it remains si

uatic life sup

ric means fo

geometric m

bution of an

assign a thre

esis that the 

geometric m

with a mean

1.65*the stan

onstructed fo

an would ne

ibution. Fo

Figure 

velop 

all the 

imilar 

pport. 

or this 

means 

nnual 

eshold 

value 

means. 

n and 

ndard 

or this 

eed to 

r this 
The threshold value provides a level of certainty that a future single geometric mean value (i.e. a 

sample) is not declared to exceed the reference distribution simply due to sampling. As was 

demonstrated above, we know that some portion of the reference distribution values will be above 

the target value. In fact, nearly 50% of the annual geometric means will be higher than the target. 

However, only 5% of the values will be higher than the threshold value of 7.59 μg/L due to 

chance. This construct defines what is known as the Type I error rate or False Positive rate. That 

is, we are willing to accept that 1 in 20 times we may get a value that is higher than 7.59 μg/L that 

still belongs to the reference period distribution. As was seen in Figure 4, 5% of the values did 

exceed 7.59 μg/L even though we know the entire population of values. 

Therefore, the type I error rate is a value that is selected based on judgment and while 5% is 

typically used, there is no definitive rationale for 5% versus 1% or 10%. If we wish to be more 

conservative, we would select a lower type I error rate by choosing a larger value (e.g., 1.96) to 

multiple against the standard deviation to minimize the potential for falsely declaring that a value 

was different from the reference distribution. If we have reason to believe that the water body may 

not fully meet its designated use at values at the higher end of the reference distribution, one could 

select a higher type I error rate which in turn would equate to a smaller z score to multiply by the 

standard deviation (e.g., 1). For example, selecting 1 standard deviation equates to a type 1 error 

rate of 16%. However, the type 1 error rate does have implications on the compliance assessment. 

Compliance Assessment 

 

Now that the definition of targets, thresholds, and type 1 error has been identified, there is another 

consideration that must be taken into account when evaluating criteria exceedances. The 

exceedance frequency for an exceedance due to chance is defined by the type 1 error rate as 

described above. However, the exceedance frequency and duration component also must be 

established to allow for some anomalous condition unrelated to anthropogenic activity such as an 

El Niño, or La Niña cycles. There is substantial evidence that these meteorological anomalies can 

result in higher chlorophyll a concentrations (e.g., Morrison et al. 2006, Sherwood 2010). 

Therefore, this type of exceedance is different from the type I error described above. Since we have 

previously defined the type I error rate, we have already made the choice as to the false positive 

rate we are willing to accept. The implementation question is now posed to ask “what is the 

frequency of exceedances and assessment cycle that allows for occurrences unrelated to local 

anthropogenic activities but remains sensitive to capturing population deviations from the reference 

period due indicative of human adverse effects?” 

To address this question the Multivariate ENSO Index calculated by Klaus Wolter of the National 

Oceanic and Atmospheric Administration (see Wolter and Timlin 1993) was used as described in 

several implementation documents produced by Janicki Environmental regarding implementation 

of numeric nutrient criteria (Janicki Environmental, Inc. 2011a-c). It is easy to see in Figure 5 that 

when El Niño or La Niña events occur they tend to last more than a single year. In fact, it’s quite 

possible for many of the single events to cross a calendar year. Further information on the 

frequency and duration of ENSO events can be found at: http://www.esrl.noaa.gov/psd/enso/mei/
Figure

Based on

result in 

one year

allowanc

2 exceed

It is poss

such that

exceedan

one migh

to a natu

pursued 

threshold

criteria ar

of the 2 i

e 5. Classifica

n this analys

higher annu

r in a 5 yea

e as an exce

ances in a 5

ible that the

t both the pr

nce occurs d

ht calculate t

ural anomaly

as the impl

d values with

re inextricab

n 5 impleme

ation of El Niñ

is, it makes

al geometric

ar cycle as 

eedance freq

year assessm

type I error 

robability of 

ue to anoma

he union pro

y. This was 

ementation 

h known typ

bly linked and

entation rule

ño and La Niñ

sense to all

c average tha

is currently

uency in a fi

ment cycle. 

rate and the

f an exceeda

alous condit

obability of a

beyond the

process is r

pe 1 error ra

d should not

is provided 

ña events as de

low for the 

an the refere

y proposed b

ve year asse

e probability

ance occurrin

ions could b

an exceedan

scope of th

refined. Beca

ates, the crit

t be separate

in Janicki En

escribed in Ja

potential tha

ence period 

by FDEP.

essment cycle

of an anoma

ng by chanc

be integrated

ce due to ch

his memoran

ause the pro

eria and the

ed. Further in

nvironmental

anicki Environ

at an anoma

threshold va

Therefore th

e is to allow

alous event 

ce and the p

d. That is, ov

hance and an

ndum but o

oposed crite

e 2 in 5 yea

nformation s

 (2011). 

nmental 2011a

alous event c

alue in more

he recomme

for no more

can be calcu

probability th

ver a 5 year

n exceedance

ne that mig

eria are base

ar implement

upporting th

a. 

could 

e than 

ended 

e than 

ulated 

hat an 

cycle 

e due 

ht be 

ed on 

tation 

he use 
References 

Janicki Environmental, Inc. 2011a. Sarasota Bay Numeric Nutrient Criteria: Task 4 - 

Implementation Issues. Letter Memorandum Prepared for Sarasota Bay Estuary Program. Sarasota, 

Florida 

Janicki Environmental, Inc. 2011b. Charlotte Harbor Numeric Nutrient Criteria: Implementation 

Issues. Letter Memorandum Prepared for Charlotte Harbor Estuary Program. Ft. Myers, Florida 

Janicki Environmental, Inc. 2011c. Tampa Bay Numeric Nutrient Criteria: Task 4 – 

Implementation Issues. Letter Memorandum. Prepared for: Tampa Bay Estuary Program. 

Morrison, G., E.T. Sherwood, R. Boler, and J. Barron. 2006. Variations in water clarity and 

chlorophyll a in Tampa Bay, Florida, in response to annual rainfall, 1985-2004. Estuaries and 

Coasts. 29:926-931. 

Sherwood, E.T. 2010. 2009 Tampa Bay Water Quality Assessment. 2010. Technical Report #02-10 

of the Tampa Bay Estuary Program. Prepared by the Tampa Bay Estuary Program. 

Wolter, K., and M.S. Timlin, 1993: Monitoring ENSO in COADS with a seasonally adjusted 

principal component index. Proc. of the 17th Climate Diagnostics Workshop, Norman, OK, 

NOAA/NMC/CAC, NSSL, Oklahoma Clim. Survey, CIMMS and the School of Meteor., Univ. 

of Oklahoma, 52-57. 

Download PDF.http://www.esrl.noaa.gov/psd/people/klaus.wolter/MEI/#ref_wt1