TAMPA BAY 

Numeric Nutrient Criteria: 

Tidal Creeks 

Letter Memorandum 

Prepared for: 

Tampa Bay Estuary Program 

Prepared by: 

Janicki Environmental, Inc. 

16 February 2011
16 February 2011 1 

Foreword 

This letter memo was produced in partial fulfillment of Purchase Order #6584, TBEP Contract T-07-

01 - Development of Numeric Nutrient Criteria for Tampa Bay. 
16 February 2011 2 

Acknowledgements 

We wish to thank the Partners of the Tampa Bay Estuary Program and members of the Tampa Bay 

Nitrogen Management Consortium for the numerous conversations providing direction and insight 

into concerns regarding numeric nutrient criteria establishment and appropriate methodology for 

developing the proposed criteria. Ms. Holly Greening and Mr. Ed Sherwood were particularly 

helpful in their insights to this issue. 
16 February 2011 3 

EXECUTIVE SUMMARY 

Tidal creeks are relatively small coastal tributaries (<1-20 km in length) that lie at the transition 

zone between terrestrial uplands, freshwater streams, and the open estuary, and serve as a link 

between terrestrial and estuarine systems. Despite their close connection to these systems, tidal 

creeks play a unique and integral role in the ecological function of coastal estuaries as: 

• a source of high primary and secondary production, 

• a site of nutrient cycling, and 

• a source of food for small-bodied fishes and crustaceans, as well as a foraging area for larger 

piscivorous fishes, wading birds, snakes, and alligators, and nursery habitat for juvenile 

fishes and crustaceans of economic value, including the common snook (Centropomus 

undecimalis). 

Tidal creeks possess water quality characteristics that differ from freshwater systems and from the 

open estuary. As a result of their direct connection and close proximity to watershed sources of 

nutrient inputs and their smaller volumes and shallower depths relative to the open estuary, tidal 

creeks have relatively high nutrient and chlorophyll concentrations and low dissolved oxygen (DO) 

levels compared to downstream waterbodies. DO levels from 2-4 mg/L are commonly observed in 

tidal creeks in the southeastern United States, including creeks from undeveloped watersheds. 

Higher nutrient concentrations and lower DO levels in tidal creeks relative to the greater estuary 

may be required to support the higher levels of primary and secondary production in these systems. 

Nutrient inputs from the surrounding watershed supply much of the fuel that drives primary 

production in tidal creeks, in the form of benthic microalgal communities and phytoplankton. The 

algal stocks, in turn, support upper trophic levels and drive secondary production by benthic 

macroinvertebrates, fishes, and decapod crustaceans. Despite possessing water quality conditions 

that would otherwise be considered impaired in freshwater and estuarine systems, tidal creeks have 

been shown to support higher densities of many species of small-bodied fishes compared to the 

adjacent estuary and tidal rivers. Many of these species have acquired physiological and 

behavioral adaptations, including aquatic surface respiration (ASR) and air-gulping, which allow 

them to persist under the low-DO conditions that often occur in tidal creeks and to take advantage 

of the forage and refuge value of these systems. 

In the Tampa Bay estuary, there are approximately sixty tidal creeks that are terminal tributaries to 

the bay or to smaller embayments within the bay. Most tidal creeks in Tampa Bay are relatively 

small (<10 km in length) and narrow (spanning only 25-50 m from bank to bank) in contrast to the 

tidal rivers which range from 40-100 km in length and 100-300 m wide on average. Many of 

Tampa Bay’s tidal creeks have been developed for urban, industrial, or agricultural land uses, 

though some tidal creeks remain relatively undeveloped and are predominantly found in mangrove 

wetlands. Unlike the open estuary of Tampa Bay which possesses expansive seagrass beds, tidal 

creeks are typically devoid of seagrass. For this reason, the development of nutrient criteria based 

on water clarity and seagrass persistence is not appropriate. 

Given the current state of knowledge for tidal creeks, four approaches to develop numeric nutrient 

criteria in tidal creeks are available. Each of these approaches has previously been considered for 
16 February 2011 4 

development of nutrient criteria for the Tampa Bay estuary. These include: 1) stressor-response 

models which examine quantitative relationships between nutrient concentrations and either 

chlorophyll a or DO concentrations within a specific waterbody of concern (i.e., tidal creek); 

2) reference condition methods which use available data for selected reference periods in creeks to 

derive numeric nutrient criteria for the creeks; and 3) downstream protective values which are 

based on the relationship between water quality in the creek and that of the downstream receiving 

estuary such that the water quality in the tidal creek does not result in water-quality exceedances in 

the downstream estuary. 

The most desirable approach to establish numeric nutrient criteria would be to develop stressorresponse models. Stressor-response models require the identification of an indicator variable that 

can be used to evaluate the condition of the tidal creek. Moreover, stressor-response models 

require identification of a threshold value above (or below) which the system would no longer fully 

support its designated use. Due to a current lack of data with which to develop stressor-response 

models for Tampa Bay’s tidal creeks, numeric nutrient criteria for these systems are currently not 

recommended. 

Numeric nutrient criteria established for tidal creeks must consider the different ecological 

processes and functions that distinguish them from both the freshwater systems upstream and the 

open estuary downstream. It is important that the established criteria for tidal creeks also account 

for the fact that these systems by nature are more variable than their upstream or downstream 

counterparts. This variability is in part what makes these systems so productive and also so difficult 

to generalize. Implementation of criteria for tidal creeks should also rely heavily on quantifying the 

uncertainties in both the derivation of criteria and in the evaluation of potential remediation efforts 

associated with failure of the criteria. Only with careful consideration of these factors can criteria 

be developed that will maintain the function of tidal creeks in support of the greater estuarine 

ecosystem.

Based on the recognized need to define distinct biological endpoints for tidal tributaries and water 

quality criteria to support them, TBEP staff recommends the following: 

• Recognize tidal tributaries as a separate waterbody class; and 

• Consider setting a schedule (i.e., within 3 years) by which time endpoints and 

criteria will be proposed, but do not attempt to set interim or final criteria with 

insufficient data. 

TBEP has dedicated funds to continue work in tidal tributaries in Tampa Bay and will commit to 

work with EPA to develop recommendations by September 2014. 
16 February 2011 5 

1.0 Background 

The Florida Department of Environmental Protection (FDEP) began development of numeric 

nutrient standards in December 2001. The FDEP formed a technical advisory committee and an 

agency work group to assist in identifying appropriate nutrient standards. FDEP conducted a 

number of workshops and meetings as well as several studies that were conducted since 2002. 

In 2008, several environmental groups filed suit against the U. S. Environmental Protection Agency 

(EPA) in Federal Court alleging that EPA had determined in 1998 that Florida’s current narrative 

nutrient standard did not comply with the Clean Water Act and that EPA had not established 

numeric nutrient standards pursuant to Section 303(c)(4)(B) of the Clean Water Act. As a 

consequence of this lawsuit, EPA sent FDEP a letter on January 14, 2009 finding that FDEP’s 

narrative nutrient standard did not comply with the Clean Water Act and directing the State of 

Florida to develop its own numeric nutrient standards for rivers and lakes by January 2010 and 

estuarine and coastal waters by January 2011 or EPA would adopt its own nutrient standards. In 

August 2009, these groups and EPA agreed to a Consent Decree formally establishing these 

deadlines and EPA will be responsible for establishing these criteria. 

Currently, EPA is developing numeric nutrient criteria for four water body types in Florida (EPA, 

2010): 

• Estuaries, 

• South Florida flowing waters, 

• South Florida coastal waters, and 

• Other coastal waters. 

The definition used by EPA for estuaries is similar to that of Pritchard (1967) and incorporates the 

State of Florida definition of a “predominantly marine water” and is as presented by Hagy (2010): 

“An estuary is a semi-enclosed body of water, connected to the open sea, defined at the 

upstream limit by average salinity equal to 2.7 and at the seaward margin by the natural 

limits of the semi-enclosed basin.” 

Questions have been raised as to whether the criteria to be proposed for the estuary proper should 

apply to tidal creeks that drain to the estuary. The objective of this document is to provide support 

for the recommendation that unique numeric nutrient criteria be developed for tidal creeks. 

Tidal creeks play an integral role in the ecological function of coastal estuaries. The treatment of 

tidal creeks in the implementation of the estuarine numeric nutrient criteria is, therefore, a 

significant issue. A thorough understanding of the ecological elements (e.g., faunal and floral 

species and communities), processes (e.g., primary productivity, nutrient cycling, secondary 

production), dynamics of tidal creeks (e.g., temporal fluctuations in dissolved oxygen) and function 

in exporting energy to estuarine and coastal ecotones is paramount to the establishment of 

ecologically appropriate nutrient criteria. Numeric nutrient criteria established for tidal creeks must 

consider the different ecological processes and functions that distinguish them from both the 

freshwater systems upstream and the open estuary downstream. Only with careful consideration of 

these attributes can criteria be developed that will maintain the function of tidal creeks in support 

of the greater estuarine ecosystem. The objective of this task is to:
16 February 2011 6 

• Provide a definition of tidal creeks, 

• Provide a generalized overview of the ecological function of tidal creeks in relation to the 

estuary, 

• Identify factors to be considered when establishing criteria for tidal creeks, and 

• Discuss potential methods for data evaluation directed at establishing nutrient criteria for 

these systems. 

1.1 Definition of a Tidal Creek

Located at the transition zone between terrestrial uplands and the open estuary, tidal tributaries 

deliver freshwater and nutrients from the surrounding watershed to the estuary. Tidal tributaries 

can be classified based on size, with larger tidal rivers often a prominent feature in the estuarine 

landscape. Smaller tidal tributaries (herein referred to as “tidal creeks”) include natural and 

manmade creeks, canals, navigational channels, and ditches created for stormwater drainage or 

mosquito control. The geomorphological and physicochemical features of the tidal creeks 

distinguish them from the non-tidal, freshwater tributaries, springs, and lacustrine systems that are 

found elsewhere in the watershed and determine zonation patterns for the flora and fauna that 

inhabit these systems. Tidal creeks in peninsular Florida may reach well upstream of the mouth 

and may be distinguished on the basis of elevation; tidal creeks extending above sea-level are often 

greater in length and drain larger watershed areas than creeks restricted to elevations below sealevel. Those tidal creeks draining only intertidal areas are likely dominated by tidal fluctuations 

and are less influenced by stormwater runoff than creeks originating above sea-level which often 

have well-developed freshwater reaches and are more sensitive to stormwater inputs. 

The differences in physiographic and water quality attributes observed along the gradient from 

headwater streams to larger rivers are the result of processes related to the flow of water and have 

been termed the “River Continuum Concept” by Vannote et al. (1980). This concept is based on 

the idea that first-order tributaries are more strongly linked to terrestrial processes and inputs and, as 

a result, are inherently different from downstream reaches. Flow-related changes to the 

geomorphology of the tributary (e.g., stream width, bank slope, channel depth) along the river 

continuum translate to differences in the composition of floral and faunal communities, trophic 

structure and ecological processes. There is evidence that this concept can be applied to coastal 

systems, as well, from freshwater tributaries to tidal tributaries to the estuary (Greathouse and 

Pringle, 2006). 

1.2 Hydrological and Water Quality Processes in Tidal Creeks

Tidal creeks are expected to possess water quality characteristics that differ from freshwater systems 

and from the open estuary; this should be a key consideration when developing numeric nutrient 

criteria for transitional systems like tidal creeks. As a result of their direct connection and close 

proximity to watershed sources of nutrient inputs and their smaller volumes relative to the open 

estuary, tidal creeks have relatively high nutrient and chlorophyll a concentrations and low 

dissolved oxygen (DO) levels (Holland et al., 2004; Sherwood, 2008) in comparison to 

downstream waterbodies where nutrient loads are rapidly diluted by the greater water volumes. 

Flushing time in unmodified tidal creeks is relatively rapid (Buzzelli et al., 2007), but retention time 

and concentration of nutrient inputs from the watershed increases in developed watersheds as the 

hydrology is impaired by sediment deposition, water-control structures, etc. Tidal creeks with 
16 February 2011 7 

extended flushing times or high nutrient inputs, in particular, have the potential to become hypoxic 

as nutrients are metabolized by the system and oxygen is consumed. For this reason, it is necessary 

that land use considerations be included when developing water-quality criteria for these systems. 

Even then, the complexity of the landscape, extent of directly connected impervious areas and the 

spatial arrangement of land use types within the watershed may limit the ability to use the same 

criteria for different tidal creeks. 

DO levels and biochemical oxygen demand in tidal creeks are tightly coupled to nutrient inputs via 

algal biomass which responds quickly to increased nutrients, often consuming oxygen in the 

process (Mallin et al., 2004). A graphical interpretation of the linkages among factors influencing 

dissolved oxygen levels is provided in Figure 1. Linkages among these factors are consistent across 

aquatic systems, though the nature of the relationships varies as a result of multiple factors. The 

relative importance of allochthonous carbon (i.e., detritus from vascular plants, such as mangrove 

leaf litter, saltmarsh grasses, terrestrial vegetation) versus autochthonous carbon (i.e., phytoplankton 

and benthic algae produced within the system) has a large influence on the rate of nutrient cycling 

and fluctuations in DO in tidal creeks. In the open estuary, autochthonous carbon is more 

important to nutrient, chlorophyll a. and DO dynamics, but in the transitional waters of the tidal 

creeks, the contribution of allochthonous inputs may be more important. For any system, including 

tidal creeks, it is necessary to have sufficient knowledge to relate these factors to the DO response 

prior to establishing appropriate carbon-supply rates commensurate with desired DO conditions. 

Typically, information on freshwater inflows, nutrient supplies, the associated autochthonous 

carbon response (i.e., via phytoplankton), and the biotic integrity of the system are more readily 

available than the supply rate of allocthonous organic carbon, re-aeration rates, and sediment 

oxygen demand that influence DO concentrations. Uncertainties related to the effects of these lessdefined impacts act as confounding factors in the development of relationships between nutrients, 

phytoplankton responses, and DO. 

Nutrients

Flow

Re-aeration

Dissolved

Oxygen

Allochthonous

carbon

Autochthonous

Carbon

- Phytoplankton

- Benthic Algae

Biotic

Integrity

Groundwater

Production

&

Respiration

Figure 1. Conceptual diagram depicting the relationships among water-quality parameters and 

physical factors that influence the biotic integrity of aquatic systems. Large arrows identify the key 

relationships that can be used to develop numeric nutrient criteria for estuaries and tidal creeks. 
16 February 2011 8 

Low DO is not uncommon in tidal creeks in the southeastern US, particularly during the warmer 

spring and summer months and at night when primary producers switch from oxygen production to 

oxygen consumption (MacPherson et al., 2007). Several tidal creeks from watersheds with varying 

land use characteristics in North Carolina all experienced low DO (2.0-4.0 mg/L) during the 

warmer, wetter months between May and September, in contrast to cooler, drier months when 

considerably higher (4.0-8.0 mg/L) DO levels were observed (MacPherson, et al., 2007). 

Groundwater inflows, common in coastal areas where the surficial aquifer is in close contact with 

surface waters, can also be a significant driver of DO conditions in tidal creeks and may need to be 

accounted for when developing water-quality relationships. As anoxic groundwater infiltrates the 

tidal creek, greater oxygen demand results (MacPherson, et al., 2007). 

1.3 Value of Tidal Creeks as Habitat for Estuarine Benthos and Nekton

Though the ecological role of tidal creeks in the coastal ecosystem is not yet fully understood, their 

value as a source of primary and secondary production and their contribution as habitat for 

juveniles of many species of marine, estuarine and freshwater fishes and crustaceans is becoming 

clear (Mallin and Lewitus, 2004; Holland et al., 2004; Krebs et al., 2007; Greenwood et al., 2008a; 

Sherwood et al., 2008). Nutrient inputs from the surrounding watershed supply much of the fuel 

that drives primary production in tidal creeks, in the form of benthic microalgal communities and 

phytoplankton. The algal stocks, in turn, support small-bodied fishes such as killifishes, sailfin 

mollies, and mosquitofish that reside permanently in the shallow waters of the tidal creeks (Nordlie, 

2000) as well as schooling species like silversides and anchovies that feed on planktonic blooms. 

The gently sloping banks of unmodified tidal creeks allow large expanses of intertidal habitat to be 

inundated by rising tides and provide access to resident fishes which use the intertidal areas 

adjacent to tidal creeks for spawning, feeding, and refuge from predators. These conditions allow 

many of the populations of resident fishes and crustaceans to reach densities that exceed those 

observed in the open estuary (Tukey and DeHaven, 2006; Sherwood, 2008; Stevens et al., 2010a) 

and provide an abundant food source which is consumed by upper trophic levels including largebodied fishes, wading birds, mangrove-saltmarsh snakes, alligators, and raccoons that forage in tidal 

creeks. In addition to resident taxa, relatively high abundances of juvenile transient fishes and blue 

crabs are found in tidal creeks (Krebs et al., 2007; Yeager et al., 2007; Greenwood et al., 2008a,b; 

Brame, 2010) compared to adjacent habitats, suggesting that tidal creeks serve as nursery habitat for 

some estuarine and coastal marine species during their early life history. 

Tidal creeks along the mid-Atlantic coast of the U.S. support a large number of nekton species. At 

least 100 taxa have been identified in tidal creeks from New Jersey to Georgia many of which also 

occur in Florida’s tidal creeks. Schooling species, including Atlantic silversides (Menidia menidia), 

bay anchovy (Anchoa mitchilli) and several species of herring and shad, mullet (Mugil spp.), 

Fundulus killifishes and palaemonid grass shrimp are the numerically dominant taxa in many of 

these systems. Penaeid and crangonid (sand) shrimp, spot (Leiostomus xanthurus), summer 

flounder (Paralichthys dentatus) and blue crab (Callinectes sapidus) are among the dominant 

economically important taxa found in tidal creeks(Cain and Dean. 1976; Hackney et al., 1976; 

Rozas and Hackney, 1984; Rountree and Able, 1992; Holland et al., 2004). 

In temperate New Jersey estuaries, greater nekton densities have been documented for saltmarsh 

tidal creeks compared to adjacent seagrass and macroalgae habitats demonstrating the importance 

of tidal creeks as habitat for fish and crustaceans and suggesting relatively high secondary 

production of small-bodied forage fishes in tidal creeks compared to adjacent habitats (Sogard and 
16 February 2011 9 

Able, 1991). The value of tidal creeks in terms of their aquatic-life support function is exemplified 

by higher growth rates and lower mortality of some juvenile fishes relative to downstream habitats 

in North Carolina (Ross, 2001). 

Macrobenthic invertebrates serve as an important component of the faunal community in tidal 

creeks, particularly as a food source for higher trophic levels. In South Carolina, 97 

macroinvertebrate taxa were collected from tidal creeks, though nearly half of these were rarely 

collected (Lerberg et al., 2000). Annelid worms, specifically oligochaetes and polychaetes were the 

dominant taxa with nine species representing 90% of the community in terms of abundance, 

though nemertean worms were also more abundant than most taxa. In Tampa Bay tidal creeks, at 

least 44 taxa have been documented (Sherwood et al., 2007) with annelid worms, amphipods and 

mysid crustaceans among the dominant macrobenthos. The latter two taxa may be particularly 

important as trophic intermediates between primary production and upper-level consumers 

(Sherwood, 2008). 

In terms of habitat value for macrobenthos, tidal creeks in South Carolina have relatively low 

Shannon diversity (1.6-3.0) compared to adjacent estuarine habitats (1.9-4.0, Chesapeake Bay; 

Lerberg et al., 2000). The range of macrobenthic diversity in Tampa Bay tidal creeks (1.5-3.0) was 

very similar to that observed for creeks in South Carolina for many of the tidal creeks, but very low 

diversity (0.5-1.0) was observed for several Tampa Bay creeks (Sherwood et al., 2007). Compared 

to the adjacent estuary, median diversity in Tampa Bay tidal creeks was generally lower (<2.0 vs. 

approximately 2.5; Karlen et al., 2008). 

1.4 Southwest Florida Tidal Creeks

Tidal creeks in Florida are known to support a diverse fish community by providing habitat for 

numerous species and by maintaining high abundances of forage fish. Approximately 150 taxa of 

fishes and decapods crustaceans have been collected from almost 80 tidal creeks from Cedar Key to 

Naples (Adams, 2005; Krebs et al., 2007; Greenwood et al., 2008a,b; Stevens et al., 2008; Stevens 

et al., 2010a,b). Among these taxa are at least twenty-four species of economic value including 

spot, mullet, red drum, penaeid shrimp, blue crabs (Yeager et al., 2006) and common snook, many 

of which use tidal creeks as a nursery during their juvenile stage. In comparison, approximately 

200 taxa were collected from the Tampa Bay estuary (including the tidal rivers) during 2008 

fisheries-monitoring efforts (FWC, 2008). Similar species numbers were recorded for the Charlotte 

Harbor and Cedar Key estuaries (FWC, 2008). 

Relative to adjacent bay and tidal river habitats, equivalent or higher fish densities have been 

documented in tidal creeks from Cedar Key to Charlotte Harbor (Tukey and DeHaven, 2006; Krebs 

et al., 2007; Greenwood et al., 2008a; Stevens et al., 2010a,b). One species in particular, common 

snook, were observed as juveniles in tidal creeks at densities 2-36 times greater than shoreline 

habitat just outside the mouth of the creeks in Tampa Bay (Greenwood et al., 2008a) and 6.5 times 

greater in tidal tributaries of the Caloosahatchee River compared to the mainstem river (Stevens et 

al., 2010a). Fish densities in Gulf coast tidal creeks typically range from several hundred to several 

thousand fish/100 m2

 (Adams, 2005; Tuckey and DeHaven, 2006; Krebs et al., 2007; Greenwood 

et al., 2008a, b; Dixon and Adams, 2010) though fish densities in some of these study creeks were 

<100 fish/100 m2

. Some of the most diverse fish assemblages in Tampa Bay tidal creeks were 

observed to have densities of 1,000-2,000 fish/100 m2

 and >30 taxa (Krebs, unpubl. ms). In 

comparison, average nekton densities from adjacent estuarine habitats, including tidal rivers, 

seagrass and mangrove shorelines, are typically <1,000 fish/100 m2

 (Tuckey and DeHaven, 2006), 
16 February 2011 10 

but have been shown to reach 2,500 fish/100 m2 just outside the mouth of Tampa Bay tidal creeks 

(Greenwood et al., 2008a). 

1.5 Dissolved Oxygen and Tidal Creek Fishes

Dissolved oxygen levels in tidal creeks are often lower than those observed in the receiving waters. 

For example, a study by Stevens et al. (2010a) reported average DO levels for the Caloosahatchee 

River to range from 7.0-7.9 mg/L in contrast to smaller tidal creeks which ranged from 6.4-6.8 mg/L 

and were 1.3 mg/L less than DO levels in the first 30 km of the mainstem river. Despite lower DO 

levels in the tidal creeks, total fish densities did not differ between the tidal creeks and mainstem 

Caloosahatchee River and were, in fact, slightly greater in the tidal creeks (mean 502 vs. 554 

fish/100 m2). Species-level differences in abundance between river and creeks were observed, with 

higher densities of many resident taxa in the tidal creeks. As has been documented in several 

previous studies (Greenwood et al., 2008; Sherwood et al., 2008; Brame, 2010), higher densities of 

juvenile common snook were observed in tidal creeks, reinforcing the idea that tidal creeks serve as 

a nursery for this economically important species. The species composition of the fish assemblage 

was distinctly different between tidal creeks and adjacent areas, as well. Of the 33 taxa collected 

during the Stevens et al. (2010a) study, nearly half (n=14 taxa) were collected in greater abundance 

in the tidal creeks, while only 9 taxa were collected in greater abundance in the mainstem river. 

The remaining taxa were equally abundant in both habitats. 

Seasonally, fish abundances in Tampa Bay tidal creeks are highest near the end of the summer 

months when water temperatures are highest and dissolved oxygen levels are lowest. The trend is 

reversed during the cooler winter months when DO levels are highest and fish densities are lowest 

(Adams, 2005; Greenwood et al., 2008b). Although no relationship was found between land use 

and the community structure of macrobenthos in Tampa Bay tidal creeks (Sherwood et al., 2007), 

there was a clear pattern for tidal creek benthos in coastal South Carolina where pollution-tolerant 

taxa dominated the assemblage in urban watersheds (Lerberg et al., 2000). Lack of a relationship in 

Tampa Bay tidal creeks may have been related to very low rainfalls (i.e., low connectivity) during 

the study year and less runoff from the watershed. 

Nekton species that commonly occur in tidal creeks have adapted to the physiologically stressful 

conditions of these systems. The often low DO conditions in tidal creeks have been suggested to 

provide a physiological refuge from predation for small fishes and crustaceans. For example, 

juvenile snook have been shown to have a much greater tolerance to low DO levels than adult 

snook, which has been proposed as a way to segregate smaller from larger individuals and reduce 

cannibalism (Peterson and Gilmore, 1991). Atlantic tarpon and Mayan cichlids are also able to 

persist at low DO levels by gulping air and storing it until oxygen is absorbed into the bloodstream 

(Geiger et al., 2000; Schofield et al., 2009). Similar physiological and behavioral adaptations have 

been observed for highly abundant prey species such as the poeciliid, cyprinodontid and fundulid 

fishes which include sailfin mollies, gulf killifish, and sheepshead minnows, all of which are 

capable of aquatic surface respiration (Nordlie, 2006), an adaptation that allows these species to 

utilize dissolved oxygen at the air-water interface when DO levels are otherwise low in the tidal 

creek. Abundances of palaemonid grass shrimp and juvenile striped mullet, also very common 

prey for many species including juvenile snook and tarpon, were negatively correlated with DO, 

with the highest abundances observed between 3-6 mg/L and very low abundances at DO >6 

mg/L (Greenwood et al. 2008a). 
16 February 2011 11 

2.0 Establishing a Foundation for the Development of Numeric Nutrient Criteria in 

Tampa Bay Tidal Creeks

The following sections provide a summary of information that should serve as the foundation for 

developing meaningful and relevant numeric nutrient criteria that will preserve the ecological 

function and habitat value of Tampa Bay tidal creeks. Further summary of recent and historical 

studies on the ecology of tidal creeks in the Tampa Bay area is provided by Krebs et al. (2010), 

MacDonald et al. (2010), and Sherwood (2010). 

2.1 Tampa Bay Tidal Creeks 

There are approximately sixty tidal creeks that are terminal tributaries to Tampa Bay or to smaller 

embayments within the bay (Figure 2). Tampa Bay tidal creeks differ substantially in scale from the 

larger tidal rivers and these differences in relative channel geomorphology result in disparate 

hydrological and physicochemical characteristics from Tampa Bay’s tidal rivers. Some of the larger 

tidal creeks extend far enough into the watershed that they have lower order, freshwater tributaries 

that feed into them (e.g., Bullfrog Creek, Double Branch Creek, Frog Creek). Tidal creeks also differ 

from freshwater tributaries of the same size primarily due to their connection to the estuary. Small 

freshwater tributaries do not experience the semidiurnal tides which cause the daily and even 

hourly fluctuations in water level, flow direction, salinity, water temperature and dissolved oxygen 

(DO) often recorded in tidal creeks (Buzzelli et al., 2007). Delineation of estuarine and freshwater 

tributaries to Tampa Bay is provided in Figure 3. 

 

Unmodified tidal creeks are characterized by sinuous, meandering channels with average water 

depths <1.0 m, while those creeks modified for drainage, mosquito control, or navigation often 

have straightened channels with steeper, more uniform banks than unmodified creeks. Tidal creeks 

altered for navigation are typically deeper than other creeks (>2.0 m in depth) and often have 

hardened shorelines that have been cleared of vegetation. Most tidal creeks in Tampa Bay are 

relatively narrow, spanning only 25-50 m from bank to bank, in contrast to the tidal rivers which 

are 100-300 m wide on average, although some of the larger tidal creeks reach 100 m or more in 

width near the mouth. The bathymetry of tidal creeks consists of alternating areas of deep, 

erosional and shallow, depositional bottom, unless the creek has been channelized, in which case, 

it is often uniformly deep. 

2.1.1 Riparian vegetation 

Shoreline vegetation in many of Tampa Bay’s tidal creeks consists largely of red mangrove 

(Rhizophora mangle) or white mangrove (Laguncularia racemosa), especially in the more 

mesohaline to polyhaline reaches and transitions. Black needlerush (Juncus roemerianus) and 

cordgrass (Spartina spp.) are also found along the banks in the higher salinity reaches, but are not 

nearly as common as mangroves. In the larger tidal tributaries with large watersheds, freshwatertolerant and upland vegetation such as cattails (Typha spp.), leather fern (Acrostichum

danaeifolium), buttonwood (Conocarpus erectus) and oak (Quercus spp.) occur as the tributary 

moves further into the upland areas. 

2.1.2 Submerged aquatic vegetation 

Unlike shallow embayments and open estuarine areas, submerged aquatic vegetation is typically 

absent from tidal creeks, perhaps due to the proximity to freshwater pulses and the resulting lower 
16 February 2011 12 

salinities found in tidal creeks. Occasionally, ephemeral beds of widgeon grass (Ruppia maritima) 

have been observed in Tampa Bay’s tidal creeks but seagrass beds consisting of turtle grass 

(Thalassia testudinum), manatee grass (Syringodium filiforme) and shoal grass (Halodule wrightii) 

are not typically found in Tampa Bay tidal creeks. 

Figure 2. Named tidal creeks within the Tampa Bay watershed. 
16 February 2011 13 

Figure 3. Approximate location of the upstream limit of tidal creeks and rivers as defined by 

empirical salinity data analysis of data from tributaries within the Tampa Bay watershed. 

 

2.1.3 Dissolved oxygen and fishes 

The relationship between fish abundance and species richness with DO has been examined from a 

number of Tampa Bay tidal creeks (Figures 4 and 5; Krebs et al., 2007; Greenwood et al., 2008a, 

2008b). Both fish abundance and species richness in a number of tidal creeks have been shown to 

be similar at DO levels between 2-10 mg/L. Below 1 mg/L, however, abundance and richness 

were much lower than observed at levels >2 mg/L. Fish abundance alone may not be a clear 

indicator of the DO in tidal creeks, as many taxa from these systems are eurytolerant to DO 

conditions and have adapted to persist at lower DO levels. This is exemplified by the high 

abundance and low richness between 1-2 mg/L (Figures 4 and 5). Species richness of the fish and 
16 February 2011 14 

decapods crustaceans is probably a more sensitive indicator of the aquatic-life support function of 

tidal creeks as less tolerant taxa are more likely to occur at higher dissolved oxygen levels, thus 

increasing species richness. As DO levels decline, less tolerant taxa are less likely to be found and 

species richness declines. These results emphasize the unique nature of tidal creeks and deserve 

consideration when the eventual nutrient criteria are proposed.

2.1.4 Phytoplankton as measured by chlorophyll a 

There is currently a paucity of data on in-stream chlorophyll a concentrations for Tampa Bay tidal 

creeks. The majority of creeks in Tampa Bay are not routinely monitored and therefore there is 

little information from which to build stressor-response models. Yet, the available information does 

suggest that these creeks are highly productive systems and that benthic algae are an extremely 

important indicator of overall productivity in tidal creeks (Sherwood et. al., 2007). While benthic 

algae are not unique to tidal creeks, their relative contribution to system productivity is greater in 

tidal creeks than in most other estuarine environments. Further research is needed to understand 

characteristics of in-stream chlorophyll a concentrations and to establish benthic algae as an 

indicator for developing nutrient criteria for tidal creeks. 

2.1.5 Nutrients 

Tidal creeks are ecologically distinct in many ways: both from the freshwater streams that drain into 

them and from the downstream estuarine waters to which they drain. Of particular note, the 

expectations for water quality in tidal creeks differ from both upstream and downstream waters. 

Specifically, chlorophyll a concentrations (including planktonic and benthic forms) needed to 

provide full aquatic-life support in tidal creeks are higher than in the upstream or downstream 

waters. Similarly, the DO concentrations needed to provide full aquatic-life support in tidal creeks 

are lower than those required in the upstream or downstream waters. As such, the endpoints used 

to establish numeric nutrient criteria should be unique to these tidal creeks. Therefore, it is 

recommended that the eventual numeric nutrient criteria for tidal creeks be based on: 

• stressor-response relationships between TN and TP and either chlorophyll a or DO 

concentrations, and 

• chlorophyll a thresholds and DO standards that reflect the unique nature of these systems. 

The potential options for developing numeric nutrient criteria, including the stressor-response 

approach are detailed below. 
16 February 2011 15 

Figure 4. Relationship between mean nekton abundance and DO in Tampa Bay tidal creeks. The 

numbers above each bar is the number of samples. 

Figure 5. Relationship between mean species richness and DO for nekton in Tampa Bay tidal 

creeks. The numbers above each bar is the number of samples. 
16 February 2011 16 

3.0 Potential Approaches for the Development of Nutrient Criteria for Tidal Creeks 

Given the current state of knowledge on tidal creeks, three approaches to develop numeric nutrient 

criteria in tidal creeks are available. Each of these approaches has previously been considered for 

development of nutrient criteria for the Tampa Bay estuary (Janicki Environmental, Inc. 2011a,b). 

• Stressor-response models – Examining quantitative relationships between nutrient 

concentrations and either chlorophyll a or DO concentrations within a specific waterbody 

of concern (i.e., tidal creek); 

• Reference condition methods - Using available data from selected reference periods in 

creeks to derive numeric nutrient criteria for the creeks; 

• Downstream protective values - Based on the relationship between the water quality in the 

creek and that of the downstream receiving estuary such that the water quality in the tidal 

creek does not result in water-quality exceedances in the downstream estuary. 

3.1 Stressor-Response Method 

The stressor-response modeling approach to establish numeric nutrient criteria in tidal creeks relies 

on the development of a quantitative relationship between known indicators of system health (e.g. 

chlorophyll a concentrations and DO) and anthropogenic stressor variables (e.g., TN or TP). Using 

these relationships, the goal is to first identify the threshold response beyond which adverse 

conditions are observed. Once this threshold value is determined, the relationship between 

stressors and response can be used to set limits on the magnitude of the stressor variable that is 

expected to maintain adequate water quality and avoid adverse conditions. 

3.2 Reference Condition Method 

The reference condition method uses available data for the system of interest to establish numeric 

nutrient criteria. The process involves the identification of ambient water-quality conditions during 

periods when the system was meeting full aquatic-life support and establishing the criterion values 

for stressors and response indicators based on these conditions. Often it is advantageous to 

establish both target values and threshold values using this approach. Target values are those that 

represent a desired management endpoint for the system while threshold values are those beyond 

which the system is likely to exhibit adverse effects. 

3.3 Downstream Protective Value Method 

The goal of the downstream protection method would be to use the estuarine nutrient criteria as a 

target to establish criteria for the tidal creek that is protective of downstream water quality. For 

example, relationships between total nitrogen concentration in the tidal creek compared to that in 

the adjacent bay segment could be used to determine how increases or decreases in nitrogen in the 

tidal creek might be related to nitrogen concentrations in the bay segment, and to identify the 

nitrogen concentration in the tidal creek that would be commensurate with the downstream 

estuarine nitrogen criterion. Using this approach is less desirable, however, as it is not based on 

maintaining the ecological function within the tidal creek and may result in nutrient criteria for the 

tidal creek that are insufficient to protect the biological integrity of the waterbody, including the 

high levels of primary production that are characteristic of these systems.
16 February 2011 17 

4.0 Recommendations

Studies of Tampa Bay tidal creeks have revealed compelling evidence that these systems represent 

unique ecotones within the greater Tampa Bay estuary. Tidal creeks play an integral role in the 

ecological function of coastal estuaries as sites of high primary and secondary production, nursery 

and refuge habitat for several species of economically important fish and decapods crustaceans, 

and foraging areas for large-bodied fishes, wading birds, and other piscivorous species. Higher 

nutrient concentrations in tidal creeks relative to the greater estuary may be required to support the 

higher levels of primary and secondary production in these systems. 

Analysis of fish collections in tidal creeks suggests that fishes inhabiting tidal creeks appear to be 

very tolerant to the typical DO conditions found in these systems. Both fish abundance and species 

richness data indicate that fish communities are relatively invariant to DO levels between 2-10 

mg/L. There are indications that at DO concentrations below 2 mg/L, both fish abundance and 

species richness decline. Species richness of fish and decapods crustaceans may be a more 

sensitive indicator of the aquatic-life support function of tidal creeks; however, these need further 

quantification to eliminate the possibility that seasonal recruitment patterns of estuarine-dependent 

fishes are not correlated with seasonal variation in dissolved oxygen concentrations due to 

temperature. 

This report has provided a foundation from which further research can be conducted to establish 

scientifically sound and ecologically meaningful numeric nutrient criteria for Tampa Bay tidal 

creeks. Future research into developing criteria for these systems should recognize that: 

• Tidal creeks represent a unique habitat in Tampa Bay, one that serves a different ecological 

function than both freshwater tributaries, tidal rivers and downstream estuarine 

environments 

• Tidal creeks are generally highly colored systems with reduced water clarity and generally 

are devoid of seagrass 

• Tidal creek productivity (measured as chlorophyll a concentration) is linked to both benthic 

algal production and water-column phytoplankton 

• Dissolved oxygen concentrations are routinely below the current state standard of 4 mg/L 

for marine waters and evidence from analysis of fish collections suggests that DO does not 

appear to limit fish abundance or richness until DO concentrations reach levels <2 mg/L 

• There is currently a paucity of empirical data from which to establish stressor-response 

relationships or reference condition approaches for Tampa Bay tidal creeks 

The most desirable approach to establish numeric nutrient criteria would be to develop stressorresponse models. Stressor-response models require the identification of an indicator variable that 

can be used to evaluate the condition of the tidal creek. Moreover, stressor-response models 

require identification of a threshold value above (or below) which the system would no longer fully 

support its designated use. 

Based on current available data it will be difficult to select a reference condition for many of Tampa 

Bay’s tidal creeks due to the paucity of empirical data in these systems. Much of the available data 

were generated from short duration studies that were intended as investigational and to serve as 
16 February 2011 18 

baseline information. More effort is needed to identify a representative period of time when the 

systems were fully supporting aquatic uses to confidently establish reference condition criteria. 

Because of these constraints, numeric nutrient criteria for these systems are currently not 

recommended. However, the following recommendations can be made for future efforts to define 

criteria for these systems. 

It is important that any established criteria for tidal creeks also account for the fact that these 

systems by nature are more variable than their upstream or downstream counterparts. This 

variability is in part what makes these systems so productive and also so difficult to generalize. The 

timing and volume of freshwater inflows are physical drivers that exert a great deal of control on 

tidal creeks. Inflows are deterministic of salinity regimes, nutrient delivery, water depths, 

temperatures and the potential for salinity stratification in these systems. Inflows also may control 

access to these systems for both small recruit species looking for refuge and for large-bodied 

predators. Therefore, the quantification of the effects on inflows on these systems will be necessary 

both to determine appropriate criteria and in the evaluation process. 

Implementation of criteria for tidal creeks should rely heavily on quantifying the uncertainties in 

both the derivation of the criteria and in the evaluation of potential remediation effort associated 

with failure of the criteria. Only if the criteria are actually relevant to the ecological function of the 

system will the criteria be meaningful in protecting full aquatic-life support in these systems. As 

such, there are many considerations in the implementation process. These considerations are 

provided in detail in Janicki Environmental (2011c). 

It is recommended that the assessment of compliance with the proposed numeric nutrient criteria 

be performed in a manner similar to that which has been proposed by TBEP for compliance with 

both the Tampa Bay Reasonable Assurance and TMDL (TBEP and Janicki Environmental, 2010). 

The goal of the estuarine numeric nutrient criteria is to provide full aquatic-life support within the 

estuary. The TBEP has determined that seagrasses are important indicators of desirable conditions 

in the bay and has defined the water-quality conditions (i.e., chlorophyll a concentrations) that 

allow for the maintenance and growth of seagrass beds in Tampa Bay. Therefore, TBEP bases its 

compliance assessment on the comparison of both observed chlorophyll a concentrations and 

seagrass extent to the goals that have been established. 

The TBEP and TBNMC have been utilizing an annual assessment strategy to track conditions in 

Tampa Bay with respect to chlorophyll a (Janicki et al., 2000). The strategy utilizes data collected 

by the Environmental Protection Commission of Hillsborough County (EPCHC) at numerous 

stations within the bay on a monthly basis. Conditions are assessed on an annual basis with respect 

to the FDEP-approved chlorophyll a thresholds in the four mainstem segments of the bay. To 

maintain consistency with these assessments, it is recommended that a similar approach be 

undertaken for tidal creeks when criteria are ultimately developed for these systems. 

TBEP has dedicated funds to continue work in tidal tributaries in Tampa Bay and will commit to 

work with EPA to develop recommendations by September 2014. 
16 February 2011 19 

5.0 References 

Adams, A.J. 2005. Evaluating the effects of restoration of subtropical oligohaline marshes on 

abundance and habitat use by juvenile snook, Centropomus undecimalis and associated fish 

communities. Final Report to the Charlotte Harbor National Estuary Program. Mote Marine 

Laboratory, Sarasota, FL. 54 pp. 

Brame, A.B. 2010. A More Comprehensive Approach for Determining Juvenile Snook Nursery 

Habitat in a Tampa Bay Wetland. In: S.T. Cooper (ed.). Proceedings, Tampa Bay Area Scientific 

Information Symposium, BASIS 5: 20-23 October 2009. St. Petersburg, FL. pp. 385. 

Buzzelli, C., A. F. Holland, D. M. Sanger, and P. C. Conrads. 2007. Hydrographic Characterization 

of Two Tidal Creeks with Implications for Watershed Land Use, Flushing Times, and Benthic 

Production. Estuaries and Coasts. 30:321–330. 

Cain, R.L. and J.M. Dean. 1976. Annual occurrence, abundance, and diversity of fish in a South 

Carolina intertidal creek. Marine Biology 36:369–379. 

Dixon, L.K. and A.J. Adams. 2010. Water quality and the fish assemblages of mangrove creeks: A 

snapshot study shows challenges in assessment of coastal zone management strategies: Draft report 

to the Charlotte Harbor National Estuary Program. 80 pp. 

Florida Fish and Wildlife Conservation Commission. 2008. Fisheries-Independent Monitoring 

Program 2008 Annual Data Summary Report. 342 pp. 

Geiger, S. A., J. J. Torres and R. E. Crabtree. 2000. Air breathing and gill ventilation frequencies in 

juvenile tarpon, Megalops atlanticus: responses to changes in dissolved oxygen, temperature, 

hydrogen sulfide, and pH. Environmental Biology of Fishes. 59:181–190. 

Greathouse, E.A. and C.M. Pringle. 2006. Does the river continuum concept apply on a 

tropical island? Longitudinal variation in a Puerto Rican stream. Can. J. Fish. Aquat. Sci. 63: 134–

152. 

Greenwood, M.F.D., D.D. Chagaris, T.C. MacDonald, R.E. Matheson, Jr., R.H. McMichael, Jr., R.F. 

Heagey, F.X. Courtney, G.V. Onorato and S.D. Stahl. 2008a. Tampa Bay tidal tributaries habitat 

initiative: Fish and fish habitat technical report. Report to the Tampa Bay Estuary Program. 290 pp. 

Greenwood, M.F.D., E. Malkin, E.B. Peebles, S.D. Stahl, and F.X. Courtney. 2008b. Assessment of 

the value of small tidal streams, creeks, and backwaters as critical habitats for nekton in the Tampa 

Bay watershed. Report to the Florida State Wildlife Grants Program. 411 pp. 

Hackney, C.T., Burbanck, W.D., and O.P Hackney. 1976. Biological and physical dynamics of a 

Georgia tidal creek. Chesapeake Science 17: 271–280. 
16 February 2011 20 

Holland, A. F., D. M. Sanger, C. P. Gawle, S. B. Lerberg, M. S. Santiago, G. H. M. Riekerk, L. E. 

Zimmerman, and G. I. Scott. 2004. Linkages between tidal creek ecosystems and the landscape and 

demographic attributes of their watersheds. Journal of Experimental Marine Biology and Ecology. 

298:151-178. 

Janicki, A., D. Wade, and J. R. Pribble. 2000. Developing and Establishing a Process to Track the 

Status of Chlorophyll-a Concentrations and Light Attenuation to Support Seagrass Restoration Goals 

in Tampa bay. Technical Report #04-00 of the TBEP. Prepared by Janicki Environmental, Inc. 

Janicki Environmental, Inc. 2011a. Tampa Bay Numeric Nutrient Criteria: Task 1 – TN and TP 

Concentrations. Letter Memorandum. Prepared for Tampa Bay Estuary Program. 

Janicki Environmental, Inc. 2011b. Tampa Bay Numeric Nutrient Criteria: Task 2 – Downstream 

Protective Values. Letter Memorandum. Prepared for Tampa Bay Estuary Program. 

Janicki Environmental, Inc. 2011c. Tampa Bay Numeric Nutrient Criteria: Task 4 – 

Implementation Issues. Letter Memorandum. Prepared for Tampa Bay Estuary Program. 

Krebs, J. M., A. B. Brame, and C. C. McIvor. 2007. Altered mangrove wetlands as habitat for 

estuarine nekton: are dredged channels and tidal creeks equivalent? Bulletin of Marine Science. 

80:839-861. 

Krebs, J. M., M. P. Weinstein, E. B. Peebles, and R. G. McConnell. 2010. Revisiting and Updating 

Our Knowledge of Tampa Bay’s Tidal Tributaries: Session Synthesis. In: S.T. Cooper (ed.). 

Proceedings, Tampa Bay Area Scientific Information Symposium, BASIS 5: 20-23 October 2009. St. 

Petersburg, FL. pp. 387-395. 

 

Lerberg, S. B., A. F. Holland, and D. M. Sanger. 2000. Responses of tidal creek macrobenthic 

communities to the effects of watershed development. Estuaries. 23:838–853. 

MacDonald, T. C., R. E. Matheson, Jr., E. B. Peebles, R. H. McMichael, Jr. and M.F.D. Greenwood. 

2010. Tidal Creeks as Nekton Habitat in the Tampa Bay Estuary. In: S.T. Cooper (ed.). Proceedings, 

Tampa Bay Area Scientific Information Symposium, BASIS 5: 20-23 October 2009. St. Petersburg, 

FL. pp. 319-330. 

MacPherson, T. A., L. B. Cahoon and M. A. Mallin. 2007. Water column oxygen demand and 

sediment oxygen flux: patterns of oxygen depletion in tidal creeks. Hydrobiologia. 586:235–248. 

Mallin, M. E. and A. J. Lewitus. 2004. Preface: The importance of tidal creek ecosystems. Journal of 

Experimental Marine Biology and Ecology. 298:145-149. 

Mallin et al. 2004. Nutrient limitation and algal blooms in urbanizing tidal creeks. Journal of 

Experimental Marine Biology and Ecology. 298:211-231. 

Nordlie, F. G. 2000. Patterns of reproduction and development of selected resident teleosts of 

Florida salt marshes. Hydrobiologia. 434:165–182. 
16 February 2011 21 

Nordlie, F. G. 2006. Physicochemical environments and tolerances of cyprinodontoid fishes found 

in estuaries and salt marshes of eastern North America. Rev. Fish Biol. Fisheries. 16:51–106. 

Peterson, M. S. and R. G. Gilmore, Jr. 1991. Eco-physiology of juvenile snook, Centropomus 

undecimalis (Bloch): Life-history implications. Bulletin of Marine Science 48:46-57. 

Ross, S.W. 2001. The relative value of different estuarine nursery areas in North Carolina for 

transient juvenile marine fishes. Fishery Bulletin. 101:384–404. 

Roundtree, R. A. and K. W. Able. 1992. Fauna of polyhaline sub-tidal marsh creeks in southern 

New Jersey: Composition, abundance and biomass. Estuaries. 15:171-185. 

Schofield, P. J., W. F. Loftus and J. A. Fontaine. 2009. Salinity effects on behavioral response to 

hypoxia in the non-native Mayan cichlid Cichlasoma urophthalmus from Florida Everglades 

wetlands. J. Fish Biol. 74:1245–1258. 

Sherwood, E. T. ed. 2008. Tampa Bay Tidal Tributary Habitat Initiative Project: Final Report and 

Management Recommendations. Tampa Bay Estuary Program Technical Report 02-08. Report to 

the Pinellas County Environmental Fund. Tampa Bay Estuary Program, St. Petersburg, FL. 83 pp. 

Sherwood, E. T. 2010. Results and Management Recommendations from the 2006 Tampa Bay Tidal 

Tributaries Habitat Initiative. In: S.T. Cooper (ed.). Proceedings, Tampa Bay Area Scientific 

Information Symposium, BASIS 5: 20-23 October 2009. St. Petersburg, FL. pp. 355-373. 

Sherwood, E. T., D. J. Karlen, T. L. Dix, B. K. Goetting, S. E. Markham, A. Chacour, M. Miller. 

2007. Tidal Tributary Study Final Report - Water Quality, Sediment Chemistry, Benthic 

Macrofauna, and Watershed Characterization. Report to the Tampa Bay Estuary Program. 250pp. 

Sogard, S. M. and K. W. Able. 1991. A comparison of eelgrass, sea lettuce macroalgae, and marsh 

creeks as habitat for epibenthic fishes and decapod crustaceans. Estuarine and Coastal Shelf 

Science. 33:501-520. 

Stevens, P. W., M. F. D. Greenwood, T. C. MacDonald, C. F. Idelberger and R. H. McMichael Jr. 

2008. Relationships between freshwater inflows and nekton populations in the Estero Bay estuary. 

Report to the South Florida Water Management District. 

Stevens, P. W., M. F. D. Greenwood, C. F. Idelberger and D. A. Blewett. 2010a. Mainstem and 

backwater fish assemblages in the tidal Caloosahatchee River: Implications for freshwater inflow 

studies. Estuaries and Coasts. 33:1216-1224. 

Stevens, P. W., T. C. MacDonald, E. Weather and R. H. McMichael, Jr. 2010b. Nekton of the 

Lemon Bay Estuarine System and a Comparison of Nekton Community Structure in Adjacent 

Southwest Florida Estuaries. Report to the Charlotte Harbor National Estuary Program. 

TBEP and Janicki Environmental, Inc. 2010. 2009 Reasonable Assurance Addendum: Allocation 

and Assessment Report. Technical Report #03-10 of the TBEP. 

Tuckey, T. D. and M. DeHaven. 2006. Fish assemblages found in tidal-creek and seagrass habitats 

in the Suwannee River estuary. Fishery Bulletin. 104:102-117. 
16 February 2011 22 

Vannote, R.L., G.W. Minshall, K.W. Cummins, J.R. Sedell and C.E. Cushing. 1980. The river 

continuum concept. Canadian Journal of Fisheries and Aquatic Sciences. 37:130-137. 

Yeager, L.A., J.M. Krebs, A.B. Brame, and C.C. McIvor. 2007. Comparison of juvenile blue crab 

abundances in three mangrove habitat types in Tampa Bay, Florida USA. Bulletin of Marine 

Science. 80:555-565.