# Site

- Specific Information in Support of Establishing Numeric Nutrient Criteria in Biscayne Bay

Florida Department of Environmental Protection Tallahassee, FL 32399

August 18, 2010Nutrient Criteria Technical Support Document Biscayne Bay

Draft ii August 2010 

### Table of Contents

Executive Summary

............................................................................................................... 1 Geographic and Physical Description

..................................................................................... 3
Sources and Fates of Nutrients

.............................................................................................. 5 Biological Summary

............................................................................................................... 8
Seagrasses

................................................................................................ .................................. 9

Coastal Wetlands

...................................................................................................................... 14 Coral Reefs

............................................................................................................................... 14 Other Biological Resources

........................................................................................................ 14 

### Summary of Existing Water Quality Studies

......................................................................... 15 Waters on the 303(d) List

..................................................................................................... 16
Propos ed Numeric Nutrient Targets

..................................................................................... 28 Regionalization

......................................................................................................................... 28 Proposed Numeric Criteria

........................................................................................................ 30 Magnitude

............................................................................................................................... 30 Frequency and Duration

............................................................................................................ 30 Summary of the Proposed Criteria

............................................................................................. 31


### References

.......................................................................................................................... 34 Appendix A. Impaired Waters in the Biscayne Bay Basin

..................................................... 38 Appendix B: Overview of FDEP Approaches for Nutrient Criteria Development in
Marine Waters

......................................................................................................... 42Nutrient Criteria Technical Support Document Biscayne Bay

Draft iii August 2010 

### List of Tables

Table 1. Checklist of nutrient enrichment symptoms in Biscayne Bay

......................................................... 2 Table 2. Major nutrient sources by region in Biscayne Bay (Caccia and Boyer 2005).

................................ 5

Table 3. Ten

- year (1994 –0 4) annual mean, wet season, and dry season canal inputs in cubic feet per second (cfs) from the canals in the three zones of Biscayne Bay (Caccia and Boyer 2005).

................................................................................................ ............................................ 7 Table 4. Mean canal loads of NO x - , NH 4 + , DIN, TP (all in tons per year), and DIN:TP (molar) to the bay regions and the entire bay, 1994

– 2002 (data from Caccia and Boyer 2007).

........................ 8 Table 5. Comparison of DIN loads to regions of Biscayne Bay (tons per year) from the atmosphere, canals, and ground water (data from Caccia and Boyer 2007).

.............................. 8 Table 6. Comparison of TP loads to regions of Biscayne Bay (tons per year) from the atmosphere, canals, and ground water (data from Caccia and Boyer 2007).

.................................................... 8 Table 7. Summary statistics for water quality in Biscayne Bay, 1994

– 2003, by season (all
concentrations are mg l -1 , except chlorophyll a, which is μg l -1 ) (Caccia and Boyer 2005).

......... 15 Table 8. Waterbodies on the 2010 Verified List for impairments in Biscayne Bay (FDEP).

........................ 23 Table 9. Estuarine waterbodies in Biscayne Bay that are proposed for delisting (FDEP).

......................... 27 Table 10. Proposed regionalization for Biscayne Bay.

............................................................................... 28 Table 11. Proposed numeric nutrient criteria for all segments of the Biscayne Bay, including TP, TN, and chlorophyll a. For compliance purposes, the long term geometric mean shall not exceed the long term limit nor shall the average of all stations in a segment exceed the network average more than twice in a 5 year period. The last column shows the value which single station shall not exceed, by segment, more than twice in a 5 year period.

................................................................................................ ......................................... 32Nutrient Criteria Technical Support Document Biscayne Bay

Draft iv August 2010 

### List of Figures

Figure 1. Map of the southeast Florida coast, showing Biscayne Bay, its protected areas, and BNP boundaries.

............................................................................................................................ 4 Figure 2. Land uses and sources of nutrient inputs to Biscayne Bay (Caccia and Boyer 2005).

................... 6 Figure 3. Map of Biscayne Bay habitats (modified from J. Serafy).

............................................................. 9 Figure 4. Location of SAV monitoring sites (CERP 2010).

........................................................................... 11 Figure 5. Location of fixed benthic and random stations (CERP 2010).

..................................................... 12 Figure 6. Probability of occurrence of seagrasses in relation to mean salinity during the wet season fitted with logistic regression (CERP 2010).

.................................................................... 13 Figure 7. Percent cover of SAV in nearshore habitats of Biscayne Bay, 2003

– 08 (CERP 2010).

................ 14 Figure 8. Zones of similar water quality in Bis cayne Bay (Boyer and Briceño 2008).

................................ 17 Figure 9. Box

- and

- whisker plots of water quality in the Alongshore zone (Boyer and Briceño 2008).

................................................................................................ .......................................... 18 Figure 10. Box

- and

- whisker plots of water quality in the Inshore zone (Boyer and Briceño 2008).

.......... 19 Figure 11. Box

- and

- whisker plots of water quality in the Main Bay zone (Boyer and Briceño 2008).

................................................................................................ .......................................... 20 Figure 12. Box

- and

- whisker plots of water quality in the South Card zone (Boyer and Briceño 2008).

................................................................................................ .......................................... 21 Figure 13. Box

- and

- whisker plots of water quality in the North Bay zone (Boyer and Briceño 2008).

................................................................................................ .......................................... 22 Figure 14. Proposed estuarine and coastal nutrient criteria sub

- basins for south Florida.

....................... 29Nutrient Criteria Technical Support Document Biscayne Bay

Draft 1 August 2010 

### Executive Summary This report was prepared by t he Florida Department of Environmental Protection (FDEP), in cooperation with local scientists, to support the development of numeric nutrient criteria for Biscayne 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.

All waters in Biscayne Bay are designated as Class III , with a designated use of f ish c onsumption and

r ecreation

, p ropagation and m aintenance of a h ealthy

, w ell -b alanced p opulation of f ish and w ildlife

. Biscayne Bay is also a designated Outstanding Florida Water (OFW)

.
Watershed development has led to a variety of intermittently observed adverse effects in portions of Biscayne Bay, including hypersalinity, algal blooms, seagrass mortality , and the loss of some fish species ( Table 1 ; South Florida Water Management District [ SFWMD ] 19 95). Water quality appears to be related to land use in the basin , and water quality in th e bay differ s among the North, Central and South regions

.
Additionally, nutrients exhibit a declining gradient from the land to the open bay (Caccia and Boyer 2005). Sources of nutrients include agricultural activities, landfill leachate, stormwater runoff (both urban and residential), atmospheric deposition, and sewage cont amination (Caccia and Boyer 2005). Despite the proximity of Biscayne Bay to these human activities, chlorophyll a concentrations in the b ay remain very low, with the highest levels observed (in North Bay) still usually less than 3 micrograms per liter (μ g l -1 ).

Table 1 shows a checklist of nutrient enrichment symptoms and descri bes whether they have occurred

, either historical ly or current ly

, in Biscayne Bay. Despite rapid urbanization and hydrologic changes to the s outh Florida system, the 1999 National Estuarine Eutrophication Assessment report found that Biscayne Bay was predo minately an oligotrophic system (N ational Oceanic and Atmospheric Administration [N OAA ] 1999).

The proposed numeric nutrient criteria are based on a “maintain existing conditions” approach using the water quality monitoring data collected from 1995 to 2009 by Florida International University ’s (FIU) Southeast Environmental Research Center (SERC)

. FDEP recommends regionalizing the bay into sub

bas ins with similar water quality characteristics , and believes that Biscayne Bay is supporting healthy biological communities and meeting its designated use during this period of record. For each sub

- basin

, the proposed criteri a are expressed as a long

- term geometric mean nutrient concentration target derived as the long

- term geometric mean concentration plus 10 %.Nutrient Criteria Technical Support Document Biscayne Bay

Draft 2 August 2010 Table 1. Checklist of nutrient enrichment symptoms in Biscayne Bay

- = Empty cell/no data Response Variable Observed Historically

or Currently? Explanation Source

Low dissolved oxygen ( DO ) (hypoxia/anoxia) Yes Low DO is localized in the North Bay near canal inputs

, where it is chronically low due to stratification

. Caccia and Boyer 2005,
2007

Reduced clarity Yes Turbidity is an issue in parts of North Biscayne Bay near historic al dredge

- and

- fill activities and near industrial complexes, s uch as the Port of Miami. Caccia and Boy er 2005 and references within; Harlem
1979

Increased chlorophyll a concentrations Yes M edian chlorophyll a concentrations have increased in the North Bay, but chlorophyll a concentrations are still generally below 3 μ g l -1

. Boyer and Briceño 2008

Phytoplankton blooms (nuisance or toxic) Yes Historically (1925

– 76)

, the Miami River discharged nutrients into northern Biscayne Bay

, leading to occasional blooms. I n 2005

– 06

, there was a diatom bloom in Blackwater Sound. Markley 2010 ; Harlem 1979

Problematic epiphyte growth No None reported. -

Problematic macroalgal growth No Drift algae is sometimes found near canal discharge sites but does not adversely affect the bay proper

. Biber and Irlandi 2006

Submerged aquatic vegetation ( SAV ) community changes or loss Yes Although SAV is stable in most of Biscayne Bay, the a bundance and community composition of seagrasses have changed near canal outputs

, potentially due to freshwater inputs

. SAV remains healthy throughout the interior of the bay. Comprehensive Everglades
R estoration Plan (CERP)
2010 ; Meeder and Boyer
2001

Emergent or shoreline vegetation community changes or loss Yes Diversion of fresh water and development of shorelines have reduced mangrove habitat. Browder et al. 2005

Coral/hardbottom community changes or loss Yes Coverage and species abundance have declined

, but there is no indication that nutrients were responsible. Robles et al. 2005

Impacts to benthic community No None reported. -

Fish kills Yes Fish kills of generally limited extent and severity have occurred from low DO, cold, red tide , fishing violations

, and other unknown causes. Florida Fish and Wildlife
Conservation Commission (FWCC) Fish and Wildlife Research Institute ( FWRI )
2010Nutrient Criteria Technical Support Document Biscayne Bay

Draft 3 August 2010 

### Geographic and Physical Description

Biscayne Bay is located along the coast of Miami

- Dade and northern Monroe Count ies

. The bay is bordered to the west by the mainland of Florida and to the east by a series of barrier islands and the northern Florida Keys (Comprehensive Everglades Restoration Plan [ CERP ] 2010). It is a shallow carbonate estuary with an area of approximately 700 square kilometers ( km 2 ) and a watershed area of about 2

, 429 km 2 ( Figure 1 ; Caccia and Boyer 2005 )

.
In general, the bay is shallow and well mixed. Depth ranges from about 0.5 to 3.0 meters ( m)

, except for dredged areas

, where depths may exceed 12 m ( Caccia and Boyer 2007 ; Roessler et al. 1975 in Caccia and Boyer 2005 ). The width of the bay ranges from 1.6 to 16 km

, and its length is approximately 88 .5 km, extending in a southwesterly direction from Dumfoundling Bay in the north to Barnes Sound in the south (Caccia and Boyer 2007 ). Tidal exchange with the Atlantic Ocean occurs through the Safety Valve, a wide series of shoals and shallow cuts in cent ral Biscayne Bay, and through narrow cuts and creeks in other parts of the bay (CERP 2010).

Biscayne Bay was designated as an OFW in 1978 and is a state Aquatic Pr eserve. The b ay also includes Biscayne National P ark (BNP)

, which is surrounded by natural areas under some form of protection, including marine waters and lands managed by the state (John Pennekamp Coral Reef State Park, Bill Baggs Cape Florida State Park, and Biscayne Bay Aquatic Reserve) or the federal government (Florida Keys National Marine Sanctuary).

The bay was historically divided into three gene ral areas : North, Central

, and S outh Bays . North Biscayne Bay is the most altered by dredging and bulkheading

, and approximately 40 % of the area is too deep or turbid to suppo rt productive bo ttom habitats. Central Biscayne Bay, which include s much of
BNP , is more marine and heavily influenced by tidal flushing. South Biscayne Bay includes Card Sound, Little Card Sound, Barn es Sound, and Manatee Bay. This area has seen the largest reduction in historical freshwater flows and become s hypersaline during periods of low rainfall.

Biscayne Bay is further subdivided into the following regions by water chemistry characteristics: north central inner (NCI), north central outer (NCO ), south central inner (SCI), south central middle (SCM), south Card Sound (SCS), south Manatee Bay (SMB), and south Barnes Sound (SBS).

The Biscayne Bay Basin currently has intensive urban development in the northern portions and extensive agricultural development in the southern regions (Irlandi et al. 2004). Biscayne Bay, Florida Bay

, and the Everglades were once part of a larger system of hydrologically interconnected wetlands and coastal lagoons

, with Biscayne Bay receiving and draining a significant amount of fresh water from the Everglades to the Atlantic (Robles et al. 2005). T o promote agricultural and urban uses, a series of massive water diversion and drainage projects in south Florida (Lig ht and Dineen 1994) transformed the natural hydrology of the region

, from a process driven by diffuse sheet flow to one now driven by pulsed

r eleases of water

. Within the bay, the system has been further altered as a result of the construction of bridges, artificial islands, and an Intracoastal Highway, and the dredging of the bay bottom (Robles et al. 2005).

The 2009 draft RECOVER SSR (CERP 2010) notes th e importance of the constructed canals on the hydrology of Biscayne Bay. There are 12 major conveyanc e canals that discharge fresh water into the bay. Flood control canals drain the watershed , and the timing and quality of freshwater discharges have been significantly modified from historical natural conditions. A number of adverse effects

— such as lower ed regional and coastal water tables (Parker et al. 1955) , reduced water storage in the watershed,Nutrient Criteria Technical Support Document Biscayne Bay

Draft 4 August 2010 decreased ground water flow, and the elimination of natural tributaries

— have occurred as a result of the construction of major canals and dredging of natural tributaries (CERP 2010). In addition, constructed drainage systems have resulted in pulsed, point source discharge s that degraded estuarine habitat near canal mouths by creat ing biologically damaging zones of bottom scouring and rapid salinity fluctuation ( CERP 2010). Drain ing the watershed and opening inlets have greatly affected natural salinity gradients and reduced or eliminated critical estuarine habitat for bay species requiring l ow - to moderate

- salinity waters (CERP 2010).

Figure 1

. Map of the s outheast Florida coast
, showing Biscayne Bay, its protected areas
, and BNP boundaries.Nutrient Criteria Technical Support Document Biscayne Bay

Draft 5 August 2010 

### S ources and Fates of Nutrients

Historically, coastal wetlands and sloughs connected the Everglades to Biscayne Bay. P oint and nonpoint sources of nutrients now reach the bay

, either directly as discharge from canals, which drain much of the watershed, o r indirectly as ground water. Fl ood control canals have hydrologically isolated tidal creeks and changed the timing and delivery of fresh water to the coastal system from what was slow seepage to larger pulsed inputs. The timing of freshwater delivery is also altered for agricultural

purposes and in anticipation of storm events.

Activities associated with CERP will change terrestrial flows within the upstream watershed, potentially increasing freshwater and nutrient inputs to Biscayne Bay. CERP aims to restore some of the historical flo w and the natural timing and distribution of water to enhance the Everglades’ wetlands and associated lakes, rivers, and bays in south Florida (CERP 2010). Historical volumes of water to Biscayne Bay were undoubtedly higher than present, but the degree to which external nitrogen ( N) and phosphorus ( P) inputs affected the system is unknown because no predevelopment water quality data exist (CERP 2010). The 2009 D raft RECOVER SSR noted the importance of freshwater inputs to the system and the need to balanc e the positive effects of freshwater inputs with the negative impacts of their concomitant nutrient loads (CERP 2010): “

... it follows that a balance exists whereby the benefits afforded by increased flow and improved salinity regime for faunal utilization are not undone by potential adverse effects from increased nutrient loading

. ”

The water quality of Biscayne Bay is highly dependent on land use and influence from the surrounding watershed ( Caccia and Boyer 2005)

. Water quality at stations sampled near er to the coast, with greater canal inputs, are more affected by nutrient loading sources than stations farther from shore (Caccia and Boyer 2005). Nutrient sources to Biscayne Bay include urban stormwater runoff, sewage contamination, landfill leachate, sewage plant discharge, agricultural runoff, groundwater inputs, and atmospheric deposition. Figure 2 shows land use s in the basin and the locations of major sources of nutrient inputs ; these sources differ by region

. Table 2 summarizes the major source s of nutrients to each of the regions of Biscayne Bay.

Table 2. Major nutrient sources by region in Biscayne Bay (Caccia and Boyer 2005).

Region Nutrient Sources

North Bay **•** Urban stormwater

**•** Sewage contamination

**•** Shoreline erosion from the action of waves against unstabilized shorelines

**•** Dredging

**•** Munisport landfill Central Bay **•** Residential stormwater South Bay **•** Runoff from the s outh Dade County agricultural basins

**•** Black Point landfill leaching

**•** Black Point Sewage Treatment Plant disch arge

**•** Homestead Air Force BaseNutrient Criteria Technical Support Document Biscayne Bay

Draft 6 August 2010 Figure 2. Land use s and sources of nutrient input s to Biscayne Bay (Caccia and Boyer 2005).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 7 August 2010 Most nutrients derived from watershed sources are delivered to Biscayne Bay via the canal system. North Bay receives the most freshwater canal input

, followed by South Bay and Central Bay, which receive minimal canal inputs (Table 3). The Miami River, Snake Creek, and Little River deliver approximately half of the entire freshwater contribution to Biscayne Bay in the North Bay region (Caccia and Boyer 2005, 2007). Table 3 shows the annual mean, wet season, and dry season discharge from the canals in each region of the bay.

Table 3

. Ten

- year (1994

– 04) annual mean, wet season, and dry season canal inputs in cub ic feet per second ( cfs ) from the canals in the three zones of Biscayne Bay (Caccia and Boyer 2005).

Caccia and Boyer (2007) calculated nutrient loads from canals, ground water
, and the atmosphere to Biscayne Bay. For the canals, they observed that nit rogen oxide ( NO x - ) loading was triple that of ammonia (NH 4 + ) and was the most abundant form of dissolved inorganic nitrogen (DIN) (T able 4 ; Caccia and Boyer 2007). NO
x - loading from Mowry and Princeton c anals into South Bay accounted for 74% of total NO x - to the bay (T able 5) , reflecting the contribution of more agricultural land use in that region. North Bay, however, received the largest NH 4 + load from the Miami River, Little River, and Snake Creek, which together accounted for 74% of the total NH 4 + l oad. Overall, DIN and freshwater flow were correlated.

Like NH 4 + , the highest total phosphorus ( TP ) loads were also from the Miami River, Little River, and Snake Creek to North Bay. These 3 inputs accounted for 60% of the entire canal TP load to the bay

. However, unlike DIN, TP load was not significantly related to flow.Nutrient Criteria Technical Support Document Biscayne Bay

Draft 8 August 2010 Caccia and Boyer (2007) also compared DIN and TP loads from canals to Biscayne Bay with loads from atmospheric wet deposition and ground water (Tables 5 and 6 , respectively ). In the North and South regions of Biscayne Bay, the DIN contributions from canals were significantly higher than from the atmosphere. For TP, however, contributions from canals were higher than the atmosphere only in North Bay. Although ground water loading est imates are only given for South Bay, they show that the relative load contribution is comparable to atmospheric or canal inputs for DIN and TP

, respectively.

Table 4

. Mean canal loads of NO x - , NH 4 +

, DIN, TP (all in ton s per year)
, and DIN:TP (molar) to the bay regions and the entire b ay , 1994

– 2002 ( data from Caccia and Boyer 2007).

Region NO x - NH 4 + DIN TP DIN:TP North Bay 235 312 547 18.6 65.1 Central Bay 39 28 67 3.4 43.6 South Bay 1, 021 52 1, 073 5.4 440.0
Biscayne Bay 1,294.5 392.6 1,687.2 27.5 143.5

Table 5

. Comparison of DIN loads to regions of Biscayne Bay (ton s per year) from the atmosphere, canals, and ground water (data from Caccia and Boyer 2007)

.

- = Empty cell/no data North Central South Atmosphere 46 51 134

Canal 547 67 1, 073

Ground water - - 141

Table 6

. Comparison of TP loads to regions of Biscayne Bay (ton s per year) from the atmosphere, canals, and ground water (data from Caccia and Boyer 2007)

.

- = Empty cell/no data North Central South
Atmosphere 2.8 3.1 8.1

Canal 18.6 3.4 5.9

Ground water - - 5.4



### B iological Summary

The principal habitat types in Biscayne Bay are seagrass meadows, coastal wetlands (including

mangrov es), and the coral reef community (Robles et al. 2005). Figure 3 shows the distribution of habitat types in Biscayne Bay. The bay’s habitats support a variety of wildlife

, including fish, invertebrates, dolphins, manatees, sea turtles, American crocodiles, bald eagles

, and many species of wading birds (Caccia and Boyer 2005 ).

Prior to the development of Miami

- Dade County, mangroves and herbaceous wetlands bordered much of Biscayne Bay (CERP 2010). Productivity is largely benthic based because of the bay’s shallow depths and naturally clear waters (Roessler and Beardsley 197 4). There is heavy development along North Bay, although benthic communities do exist and are dominated by seagrasses intermixed with calcareousNutrient Criteria Technical Support Document Biscayne Bay

Draft 9 August 2010 green algae (CERP 2010). There is less development along Central and South Bay, and natural mangrove wetlands are intact along the western shore and eastern barrier islands (CERP 2010). The benthic
communities in C entral and S outh B ay comprise several seagrass species, including Thalassia testudinum ( turtle grass), Halodule wrightii (shoal grass), Syringodium filiforme (manatee grass), and algae. There are also hardbottom communities of hard and soft corals, sponges, and other organisms found in distinct patches along the north

- south axis of the middle of the bay (CERP 2010).

Figure 3

. Map of Biscayne Bay habitats (modified from J. Serafy).

Seagrass es
The predominant seagrass in Biscayne Bay is T. testudinum (Irlandi et al. 2002). Other seagrasses include S. filiforme and H. wrightii . Combined, these seagrasses cover approximately 65% of the bay (Miam i- Dade Department of Environmental Resources Management [ DERM ] 1985). The seagrass cover is most extensive in Central Bay, covering 75% of the bottom, and least extensive in North Bay, covering only 25% of the bottom . The lower percent age coverage in the Northern Bay is predominately due to the influence of dredge

- and

- fill activities and canal discharge. The bottom of South Bay is over 50% seagrass and approximately 35% hardbottom. S eagrass specie s generally shift from H . wrightii inNutrient Criteria Technical Support Document Biscayne Bay

Draft 10 August 2010 nearshore waters to T. testudinum interspersed with H . wrightii and S . filiforme in deeper waters (Lirman and Cropper 2003).

As part of CERP restoration activities, t here will likely be a diversion of fresh water from canals that flow into Biscayne Bay west to the Everglades. Much of the research described below focuse s on the role of freshwater influx es on the structure and function of the seagrass community.

Biber and Irlandi (2006) characterized the species composition, biomass

, and percent cover of drift alga e and rhizophytes at T

. testudinum

- dominated sites with different salinity conditions from 1996 to 1999. Sites were canal influenced (low salinity), had natural sheet flow conditions (intermediate salinity), or had oceanic conditions (normal 35 practical salinity units [ psu ] salinity). The authors suggest that canal discharge poses an unnatural stress to the seagrass habitats of western Biscayne Bay. While stress effects were not particularly obvious in the standing stock biomass of T. testudinum , the influence of the canal discharge was evident in the composition of the macroalgal community found within seagrass beds at the three salinity regimes

— in particular

, changes in abundance and dominance from drift algae at the canal sites to rhizophytic algae at the oceanic sites.

It is important to note that m acroalgae are an important component of the benthic community of Biscayne Bay. The many species of algae in the bay ar e roughly grouped into drift algae (e.g.

, Chondria

spp., Laurencia spp.) and rhizoph ytic algae (e.g. Caulerpa spp., Halimeda spp., and Penicillus spp.) (Biber and Irlandi 2006). Clumps of detached drift algae may alter seagrass productivity through shading ; however

, benthic rhizophytic algae can facilitate seagrass succession by stabiliz ing sediments and adding organic matter. Irlandi et al. ( 2004 ) investigated drift algae

- epiphyte

- seagrass interactions in a T. testudinum meadow and found no negative response on the short

- term growth of T. testudinum by drift algae.

Meeder and Boyer (200 1) found that high NH 4 + concentrations associated with the Black Point landfill in South Bay were correlated with the decreased abundance of T. testudinum and increased abundance of filamentous red algae cover. Szmant (1987) found nutrient

- related canal impacts at the discharge points of the Mowry and Princeton C anals . These included increased periphyton growth on artificial seagrass blades and the replacement of T. testudinum with H. wrightii

.

Irlandi et al. (2002) determined the biomass, morphometrics, and production of T. testudinum at sites exposed to varying degrees of freshwater runoff to evaluate the possible effects of changes in freshwater inputs to Biscayne Bay. Their results indicate that freshwater runoff only affected the biomass and morphometry of T. testudinum during years with particularly high rainfall

, where the seagrasses were exposed to prolonged conditions of low salinity. They concluded that as long as reductions in freshwater inputs to Biscayne Bay do not re sult in hypersaline conditions, the diversion of fresh water to the Everglades should have a positive effect on T. testudinum

.
In addition to the research described above, there are several ongoing long

- term monitoring programs collecting data on SAV and water quality in Biscayne Bay

, specifically to establish baseline conditions against which changes associated with the implementation of CERP can be assessed (CERP 2010).

Figure 4 shows the locations of moni toring sites in the south Florida estuaries. For Biscayne Bay, monitoring programs include nearshore and benthic monitoring of SAV (CERP 2010 and references within).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 11 August 2010 Figure 4 . Location of SAV monitoring sites ( CERP 2010).

Miami

- Dade DERM, in partnership with SFWMD, has conducted a benthic habitat monitoring program in Biscayne Bay since 1985. The monitoring program was initiated with 13 fixed locations throughout theNutrient Criteria Technical Support Document Biscayne Bay

Draft 12 August 2010 bay, 10 of which remain active. Figure 5 shows t he study area. Sampling was cond ucted quarterly at fixed strategic locations from 1985 to 1996, when it was decreased to once annually. In addition, stratified random sampling has been conducted annually since 1999 (Fourqurean et al. 2002).

Figure 5

. Location of fixed benthic and random stations (CERP 2010).

The nearshore (less than 500 m from shore) benthic habitats of Biscayne Bay have been monitored since 2003 to evaluate the spatial patterns of SAV abundance in relation to distance from shore and the inflow of fresh water fro m canals, ground water, and overland sources (Lirman et al . 2008; CERP 2010). The monitoring project provides baseline data for seasonal species composition and distribution and SAV abundance in the nearshore habitat

, which is sensitive to changes in freshwater input.

The main r esults from the DERM and Lirman et al. (2008) monitoring programs are as follows :

**•** Patterns of T. testudinum cover in S outh Bay follow relationships with salinity regimes, water depth

, and sediment depth. All three seagrass species showed significant relationships with mean salinity; H. wrightii had a higher probability of occurrence at low mean salinity, while T. testudinum and S. filiforme had a higher probability of occurrence at high mean salinity ( Figu re 6 ).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 13 August 2010 **•** The abundance of T. testudinum increased linearly with increasing distance from shore and depth

, while the abundance of H. wrightii had the opposite pattern.

**•** H. wrightii and S. filiforme have had stable benthic cover since 2002

, while T. testudinum showed a steady decline from greater than 40 % in 2003 to less than 20 %
in 2008

, and macroalgal cover remained stable between 2003 and 2008 (Figure 7 ).

**•** The proportion of the densest patches, which had greater than 70 % cover, declined greatly from 2003 to 2 008, suggesting that the decline in cover was especially pronounced within the densest T. testudinum beds.

**•** H. wrightii is second to T. testudinum in overall presence. Reviews of 3- year groupings of data show H. wrightii was consistently found in the northern and southern regions, with low (less than 5% ) to moderate cover (25 % ). It also occurs sporadically along the western shore, and in the hardbottom areas at low cover (less than 5% ). S. filiforme is primarily located in the northern and southern sectio ns, with infrequent records in western nearshore and eastern polygons.

**•** Low percent cover (less than 5% ) is common in the hardbottom habitats of the southern mid

- bay. Additional areas of lower cover also occur in habitats with greater depth (northern and southern) and/or lower salinity

.

Figure 6. Probability of occurrence of seagrasses in relation to mean salinity during the wet

s eason fitted with logistic regression (CERP 2010).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 14 August 2010 Figure 7. Percent cover of SAV in nearshore habitats of Biscayne Bay
, 2003

– 08 ( CERP 2010).

Coastal Wetlands

Biscayne Bay has a narrow strip of coastal wetlands consisting primarily of mangroves and sawgrass. Development has reduced the extent and composition of the wetlands by reducing freshwater inputs (via diversion for agriculture or residential uses) (CERP 2010). According to the 2009 D raft RECOVER SSR (CERP 2010) , t he coastal wetlands are an important influence on the inshore areas of the bay and numerous important sport and commercial fish that have been monitored in the mangrove shoreline zone since 1998 as a gauge of Everglades restoration impacts (CERP 2010)

. Although littl e is known about predevelopment communities, c ommunity composition is likely to change further as restoration efforts increase natural freshwater flow s to the area.

Coral Reef s
The reef tract of BNP is a complex assortment of approximately 4,000 patch reefs located on a shallow Holocen e platform on the eastern edge of Hawk Channel (Jaap 1984 in Robles 2005). Coral reefs in Florida face a number of different stressors. T he Florida Reef Tract and adjoining Biscayne Bay are sites of extensive recr eational and commercial fishing, an activity that has a large impact on coral reefs (Robles 2005). Additional stressors include coral bleaching, diseases, water pollution, physical impacts (such as groundings, dredging activities, and beach renourishment) , tropical storms, and winter cold fronts (Banks et al. 2005). The areal coverage and species abundance on coral reefs within BNP and the south Florida Reef Tract have declined over the past several decades , although the cause of the decline is not unders tood (Dustin and Halas 1987; Porter and Meier 1992)

.
Other Biological Resources

The seagrass habitat supports many other organisms

, including pink shrimp ( Penaeus duorarum ), spiny lobs t er ( Panulirus argus ), and many recreationally and commercially import ant fish such as spotted sea trout ( Cynoscion nebulosus ), red drum ( Sciaenops ocellata ), snook ( Centropomus undecimalis ), andNutrient Criteria Technical Support Document Biscayne Bay

Draft 15 August 2010 mangrove snapper ( Lutjanus griseus ) (Robles et al. 2005). Biscayne Bay is also a refuge for juvenile spiny lobster

, and a large portion of the bay is a designated lobster sanctuary (Robles et al. 2005).



### Summary of Existing Water Quality Studies

Water quality in Biscayne Bay is generally good, with diminished quality limited to the North Bay and the western margin of the bay. Water quality has been monitored in Biscayne Bay for over 30 years through state, local, federal, and university partnerships. Sources of water quality data include FIU, University of Miami (UM), N OAA, BNP , and DERM.

N utrient loads and concentrations in Biscayne Bay are strongly driven by canal inputs (Caccia and Boyer
2007 ; Browder et al. 2005 ). Concentrations of several w ater quality parameters in a number of the canals and rivers that discharge to the bay are high compared with the open waters of the bay (Browder et al. 2005). P recipitation patterns have a great impact on the bay

, both directly as rainfall and indirectly by influencing runoff and canal discharge

.
Caccia and Boyer (2005) report water quality results for sampling conducted f rom 1994 to 2003 by season (Table 7). TP values ranged from 0.00 to 0.049 milligrams per liter ( mg l -1 ) with a median of 0.006 mg l -1 . All N species concentrations were highest in the wet season

, when canal inputs are greater. There was also a strong gradient f rom inshore out to the open bay . Contrary to total nitrogen ( TN)

, concentrations of TP and soluble reactive phosphorus ( SRP ) did not show a gradient with distance from land; however, TP was similarly higher during the wet season in areas receiving inputs from canals. TP in North Bay was significantly higher than the other regions at all times of the year.

The highest median chlorophyll a concentrations were also found in the North Bay zone and lowest in South Bay. An earlier water quality study found s imilarly high chlorophyll a in North Bay (8.6 μg l -1 ) and low chlorophyll a in South Bay (0.2 μg l -1 ) (Brand 1998). Brand et al. (1991) also noted that the highest chlorophyll a concentrations were always associated with lower salinities, suggesting that the source of nutrients generating phytoplankton blooms is freshwater runoff.

Table 7 . Summary statistics for water quality in Biscayne Bay
, 1994

– 2003 , by season (all concentrations are mg l -1

, except chlorophyll a

, which is μg l -1 ) (Caccia and Boyer 2005).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 16 August 2010 The FIU Coastal Water Quality Monitoring Network has collected water quality data monthly at 25 stations in Biscayne Bay since fall 199 3 (Boyer and Briceño 2008). Boyer and Briceño ( 2008) found 6 groups of stations with similar water quality (Figure 8 ): the Alongshore group (AS), Inshore group (IS), main Bay group (MAIN), ocean channel group (not shown in Figure 8 ), Card Sound group (SCARD), and Turkey Point station, which comprised its own group (not shown in Figure 8 ).

The 2008 Cumul ative Annual Report for the Coastal Water Quality Monitoring Network provides summary figures for each parameter by station group (Boyer and Briceño 2008) . Figures 9 through 13 also show the long

- term data for each of the parameters by group. In general, c hlorophyll a , DIN, and TP concentrations were highest nearshore and decreased w ith di stance away from shore

, and N orth Bay had the highest DIN and TP concentrations. In most areas chlorophyll a was low and followed the same gradie nt as TP.



### Waters on the 303(d) List

Table 8 provides the complete list of waters that are verified impaired in the Southeast Coast –Biscayne Bay Basin, and Table 9 identifies the waters that are proposed for delisting. See Appendix A for the Cycle 2 draft list of all verified impairments for both estuary and stream waters (FDEP 2010a, b).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 17 August 2010 Figure 8

. Zones of similar water quality in Biscayne Bay (Boyer and Briceño 2008)

.Nutrient Criteria Technical Support Document Biscayne Bay

Draft 18 August 2010 Figure 9

. Box

- and

- whisker plots of water quality in the Alongshore zone (Boyer and Briceño 2008).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 19 August 2010 Figure 10

. Box

- and

- whisker plots of water quality in the Inshore zone (Boyer and Briceño 2008).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 20 August 2010 Figure 1 1. Box

- and

- whisker plots of water quality in the Main Bay zone (Boyer and Briceño 2008).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 21 August 2010 Figure 12. Box

- and

- whisker plots of water quality in the South Card zone (Boyer and Briceño 2008).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 22 August 2010 Figure 1 3. Box

- and

- whisker plots of water quality in the North Bay zone (Boyer and Briceño 2008).Nutrient Criteria Technical Support Document Biscayne Bay

Draft 23 August 2010 Table 8. Waterbodies on the 2010 Verified L ist for impairments in Biscayne Bay (FDEP ).

IIIM = Class III Marine IIIF = Class III Freshwater Chl a = Chlorophyll a Basin Group
Name Planning
Unit Waterbody
ID (WBID) Waterbody Segment Waterbody Type Waterbody Class 1 Parameters Assessed Using 2001
IWR Concentration Causing Impairment 2 Priority for
TMDL Development 3 Comments (# Exceedances/# Samples) PP = Planning Period VP = Verified Period 4

Southeast
Coast

– Biscayne Bay Biscayne Bay Intracoastal 3226H ICWW ( Miami

- Dade County) Estuary IIIM Fecal Coliform >400 colonies/
100mL Medium PP = 311/2525; VP = 218/1397

Southeast
Coast

– Biscayne Bay Broward County 3274 C- 13 East (Middle River Canal) Estuary IIIM Fecal Coliform >400 colonies/
100mL Medium PP = 19/168; VP = 39/205 Data based on updated Run 22 from 10 -26-05.
Southeast
Coast

– Biscayne Bay Broward County 3274 C- 13 East (Middle River Canal) Estuary IIIM Nutrients (Historic

c hl a ) TN = 1.34 mg/L TP = 0.08 mg/L Medium VP: A nnual average c hl a values in verified period exceeded historical minimum (of 2.5 **μ** g/L for
1992– 96) by more than 50% in 2001 (5.0825 **μ** g/L), 2002 (9.5931 **μ** g/ L ), 2003 (8.0321 **μ** g/L) and 2004 (8.1306 **μ** g/L). Data
indicate that WBID is co

limited (TN/TP median = 18.674, standard deviation 15.003, range 4.96 to 81.07, 71 observations). Data based on updated Run 22 from 10 -26-05.
Southeast
Coast

– Biscayne Bay Broward County 3226G4 Las Olas Isles Finger Canal System Estuary IIIM Fecal Coliform >400 colonies/
100mL Medium PP = 199/563; VP = 20/74 Data based on updated Run 22 from 10 -26-05.
Southeast
Coast

– Biscayne Bay Broward County 3276A New River (North Fork) Estuary IIIM DO < 4.0 mg/L Medium PP = 28 / 86; VP = 28 / 83 Verified impaired and nutrients were found to be causativeNutrient Criteria Technical Support Document Biscayne Bay

Draft 24 August 2010 Basin Group
Name Planning
Unit Waterbody
ID (WBID) Waterbody Segment Waterbody Type Waterbody Class 1 Parameters Assessed Using 2001
IWR Concentration Causing Impairment 2 Priority for
TMDL Development 3 Comments (# Exceedances/# Samples) PP = Planning Period VP = Verified Period 4
pollutant. Data based on updated Run 22 from 10

- 26-05.
Southeast
Coast

– Biscayne Bay Broward County 3276A New River (North Fork) Estuary IIIM Fecal Coliform >400 colonies/
100mL Medium PP = 147/265; VP = 45/104. Data based on updated Run 22 from 10 -26-05.
Southeast
Coast

– Biscayne Bay Broward County 3276A New River (North Fork) Estuary IIIM Nutrients (Chl a ) TN = 1.62 mg/L TP = 0.11 mg/L Medium VP: C hl a values exceeded IWR threshold in 1998 (28.18 **μ** g/L), 1999 (29.42

**μ** g/L), 2000 (16.3 **μ** g/L), 2001 (14.04 **μ** g/L) and 2004 (26.27 **μ** g/L). Data
indicate that WBID is co

limited (TN/TP median = 13.818, standard deviation 8.7913, range 5.609 to 62.0 , 88 observations). Data based on updated Run 22 from 10 -26-05.
Southeast
Coast

– Biscayne Bay Broward County 3276A New River (North Fork) Estuary IIIM Total Coliform >2,400 colonies/
100mL Medium PP = 56/151; VP = 13/53 Data based on updated
Run 22 from 10 -26-05.
Southeast
Coast

– Biscayne Bay Broward County 3277A New River Canal (South) Estuary IIIM Fecal Coliform >400 colonies/
100mL Low PP = 23/184; VP = 22/144 Data based on updated Run 22 from 10 -26-05.
Southeast
Coast

– Biscayne Bay Broward County 3277A New River Canal (South) Estuary IIIM Nutrients (Historic Chl

a ) TN = 1.84 mg/L TP = 0.07 mg/L Low VP: A nnual average c hl a values in verified period exceeded historical minimum value (of 4.8

**μ** g/L for 1995

– 99) by more than 50% in 2003 (7.9892

**μ** g/L) and 2004 (7.2405

**μ** g/ L ). Data indicate thatNutrient Criteria Technical Support Document Biscayne Bay

Draft 25 August 2010 Basin Group
Name Planning
Unit Waterbody
ID (WBID) Waterbody Segment Waterbody Type Waterbody Class 1 Parameters Assessed Using 2001
IWR Concentration Causing Impairment 2 Priority for
TMDL Development 3 Comments (# Exceedances/# Samples) PP = Planning Period VP = Verified Period 4

WBID is co

- limited (TN/TP median = 29.521, standard deviation 50.263, range 7.337 247.9, 94 observations). Data based on updated Run 22 from
10-26-05.
Southeast
Coast

– Biscayne Bay North Dade County 3288 C- 6/Miami River Estuary IIIM Copper > 3.7 μg/L Medium PP = 18/69; VP = 14/46

Southeast
Coast

– Biscayne Bay North Dade County 3288 C- 6/Miami River Estuary IIIM Fecal Coliform >400 colonies/
100mL Low PP = 253/631;
VP = 202/434

Southeast
Coast

– Biscayne Bay North Dade County 3288 C- 6/Miami River Estuary IIIM Total Coliform >2,400 colonies/
100mL Low PP = 191/629; VP = 152/432

Southeast
Coast

– Biscayne Bay North Dade County 3290 C- 6/Miami River Estuary IIIF Fecal Coliform >400 colonies/
100 mL Medium PP = 27/167; VP = 33/149

Southeast
Coast

– Biscayne Bay North Dade County 3288A Wagner Creek Estuary IIIM Dioxin >7 ppt Medium Verified impaired based on fish advisory for checkered puffer, striped majarra, and yellow fin mojarra.
Southeast
Coast

– Biscayne Bay North Dade County 3288A Wagner Creek Estuary IIIM Fecal Coliform >400 colonies/
100mL High PP = 198/223; VP = 139/157

Southeast
Coast

– Biscayne Bay North Dade County 3288A Wagner Creek Estuary IIIM Total Coliform > 2,400 colonies/
100mL High PP = 193/223; VP = 137/157Nutrient Criteria Technical Support Document Biscayne Bay

Draft 26 August 2010 Basin Group
Name Planning
Unit Waterbody
ID (WBID) Waterbody Segment Waterbody Type Waterbody Class 1 Parameters Assessed Using 2001
IWR Concentration Causing Impairment 2 Priority for
TMDL Development 3 Comments (# Exceedances/# Samples) PP = Planning Period VP = Verified Period 4

Southeast
Coast

– Biscayne Bay North Dade County 3288B C- 6/Miami River (Lower Segment) Estuary IIIM Fecal Coliform >400 colonies/
100mL Medium PP = 38/74; VP = 16/26

Southeast
Coast

– Biscayne Bay North Dade County 3288B C- 6/Miami River (Lower Segment) Estuary IIIM Total Coliform >2,400 colonies/
100mL Medium PP = 31/73; VP = 15/26Nutrient Criteria Technical Support Document Biscayne Bay

Draft 27 August 2010 Tabl e 9

. Estuarine w aterbodies in Biscayne Bay that a re proposed for delisting (FDEP ).

Chl a = Chlorophyll a IIIM = Class III Marine
Basin Group
Name Planning
Unit WBID Waterbody Segment Waterbody Type Waterbody Class 1998 303(D) Parameters of Concern Parameters Evaluated Using
IWR Comments (with # of Exceedances/ # of Samples
Southeast
Coast

– Biscayne Bay Broward County 3282 Hollywood Canal Estuary IIIM Nutrients Nutrients (Chl a) Chl a values exceeded IWR threshold in 1998 (22.74 **μ** g/L), but annual

average c hl a values did not exceed
IWR threshold of 11.0 **μ** g/L in 1999 (10.4 **μ** g/L), 2000 (4.123 **μ** g/L), 2001 (7.063 **μ** g/L), 2002 (5.623 **μ** g/L) and 2004 (4.51 **μ** g/L). TN (1.0295 mg/L) exceeds threshold of 1.0 mg/L. TP (0.0625 mg/L) does not exceed screening threshold of 0.19 mg/L. Data based on updated Run 22 from
10-26- 05.
Southeast
Coast

– Biscayne Bay Broward County 3277A South New River Canal Estuary IIIM Nutrients Nutrients (Chl a) Annual average c hl a values do not
exceed IWR threshold of 11.0 **μ** g/L in 1998 (4.177 **μ** g/L), 1999 (4.597 **μ** g/L), 2000 (5.326 **μ** g/L), 2001 (7.486 **μ** g/L), 2002 (3.28 **μ** g/L), 2003 (7.989 **μ** g/L)
and 2004 (7.241 **μ** g/L). TN (1.5835 mg/L) exceed s screening threshold of 1.0 mg/L. TP (0.051 mg/L) does not exceed screening threshold of 0.19 mg/L. Data based on updated Run 22 from 10 -26- 05.
Southeast
Coast

– Biscayne Bay Broward County 3277A South New River Canal Estuary IIIM Coliforms Total Coliform PP = 6/146; VP = 8/93 Data based on updated Run 22 from
10-26- 05. Not i mpaired

.Nutrient Criteria Technical Support Document Biscayne Bay

Draft 28 August 2010 

### Proposed Numeric Nutrient Targets

FDEP recommends regionalizing the bay into sub

- basins with similar water quality characteristics and applying the “maintain existing conditions” approach to setting nutrient criteria. FDEP proposes preliminary criteria calculated using long

- term water qua lity data collected from 1995 to 2009 by FIU.

Regionalizatio n

FIU has u s ed the data collected as part of its Coastal Water Quality Monitoring Network initiated in 1992 to spatially aggregate monitoring sites located in south Florida based on similar water quality characteristics (Boyer and Briceño 2008). Based on the unique water quality and geologic characteristics observed in south Florida, Everglades National Park (ENP) and FIU have proposed that the estuarine and coastal waters of south Florida be divi ded into sub

- basins for the purpose of deriving nutrient criteria.

On behalf of ENP, FIU recently completed an extensive statistical characterization of coastal waters from Biscayne Bay to Dry Tortugas to Pine Island Sound. The recent analysis was simil ar to the earlier spatial regionalization method used by FIU, but u s ed a longer period of record and a modified set of parameters. The analysis , which used a combination of Principal Component Analysis and Hierarchical Clustering of multiple (from 8 to 13 ) parameters, produced a division of the bays as shown in Table 10 and Figure 14

. Appendix A provides m ore detail on the analysis conducted by Henry Briceño, Joe Boyer, and Peter Harlem from FIU.

This regionalization scheme will be the basis for proposing numeric criteria for each sub

- basin. A final step in the process will be to evaluate the similarity of the derived criteria with the purpose of combining sub

- basins with similar criteria (i.e., criteria that are not statistically different) for TP, TN , and chlorophyll a

.
On the basis of the statistical analysis performed, the south Florida bays and coastal waters, in cluding those of Biscayne Bay , were divided as detailed in Table 10 and illustrated in Figure 14

. Table 10 list s the sub

- basins for Biscayne Bay

.
Table 10. Proposed reg ionalization for Biscayne Bay

. Sub

- Basin Map Code Sub

- Basin Name

MBS Manatee Bay

- Barnes Sound

SCO South Central Outer

- Bay

SCI South Central Inshore

SCM South Central Mid

- Bay

CS Card Sound

SNB Southern North Bay

NCI North Central Inshore

NCO North Central Outer

- BayNutrient Criteria Technical Support Document Biscayne Bay

Draft 29 August 2010 Figure 14. Proposed estuarine and coastal nutrient criteria sub

- basins for s outh Florida.Nutrient Criteria Technical Support Document Biscayne Bay

Draft 30 August 2010 Proposed Numeric C riteria

T o be applied consistently and to provide an appropriate level of protection, water quality criteria need

to include magnitude, frequency, and duration components. The magnitude is a measure of how much of a pollutant may be present in the water without an unacceptable adverse effect. Duration is a measure of how long a pollutant may be above the magnitude, and frequency relates to how often the magnitude may be exceeded without adverse effects. I t is prefer able to derive the magnitude component of a crit erion through a cause

- effect relationship (such as th at measured through toxicity testing). The magnitude would then be set at a level that would protect a majority of the sensitive aquatic organisms inhabiting the system. Absent sufficient data to demonstrate a cause

- effect relationship, the magnitude may be set at a level designed to maintain the current data distribution, accounting for natural temporal variability, assuming the current conditions are protective of the designated uses of the water body

. Since a criterion derived based on the existing data distribution has no direct link to any observed cause

- and effect relationship , i t is assumed that maintaining the current data distribution will preserve the uses associated with that distribution

.
The frequency and duration components of the criteria are best established as additional descriptors of the reference condition data distribution. Specifically, these components should be part of a statistical test designed to determine whether the lo ng

- term distribution of data has shifted upward from the reference distribution. This test would then be used to determine whether future monitoring data are consistent with the magnitude (long

- term average) defined by the reference dataset. It is critical to account for the natural variability surrounding the magnitude expression and to control for statistical errors. The magnitude component can be set at the long

- term central tendency (geometric mean) of the distribution, while the frequency and duration components describe how often and by how much nutrient concentrations can be above the central tendency while still being consistent with the reference distribution. The derivation of the magnitude, frequency and duration components of
numeric nutrient criteria for the Southwest Coastal area is described briefly below. More details concerning the statistical approaches used can be found in the document, Overview of FDEP Approaches for Nutrient Criteria Development in Marine Waters ( Appendix B).

Magnitude

The magnitude component represents a level of nutrients demonstrated to be protective of the designated use. For the “healthy existing conditions” approach, the magnitude can be interpreted as the central tendency of the baseline distribution and may b e set at a level that represents a long

- term average condition of that distribution. The long

- term average condition may also be adjusted to a level that represents an insignificant increase from the baseline. Allowing for an insignificant increase

accou nts for uncertainty in the estimate of the mean and partially addresses the fact that the reference

based approach fails to identify a threshold of imbalance, and thus is highly prone to excessive Type I error. For the purpose of antidegradation evaluatio ns, the U.S. Environmental Protection Agency ( EPA ) has historically considered a 10% change in a water quality parameter to represent an insignificant departure from the existing condition. Therefore, the magnitude component of the criteria was derived ba sed on a 10% increase in the long

- term geometric mean calculated as the geometric mean of the annual geometric means from the long

- term existing dataset for each sub

- basin area identified above.

Frequency and Duration

To provide a consistent and appropriate level of protection, the duration and frequency components of the criteria must be consistent with the derivation of the magnitude component. While the magnitudeNutrient Criteria Technical Support Document Biscayne Bay

Draft 31 August 2010 component of the criteria is being expressed as a lon g- term geometric mean concentration, in most cases based on 9 or more years of data, it is not practical to assess compliance with the criteria on the same long

- term basis. Instead, a statistical test can be developed to allow the application of the crite ria on a shorter

- term basis. For the criteria to be protective, the duration component of the criteria (e.g., single sample maximum, annual geometric mean) must be linked to the response time frame of the sensitive endpoint

. Short

- term averaging periods (e.g., 1 to 30 days) might be appropriate for nutrient criteria where a sufficiently robust cause

- effect relationship has demonstrated that a eutrophic response occurs over such time frames. If

, however, such a short

- term response cannot be demonstrated, or there is no indication of use impairment, then longer averaging periods should be considered.

For example, since the relationship between nutrient and chlorophyll a response in Florida lakes was extremely weak

, with a much more robust relationship found when data were evaluated based on annual ly averaged log

- transformed data, FDEP and EPA used an averaging period of a year to assess the enrichment in Florida lakes with the criteria being expressed as an annual geometric mean. Likewise, the nutrient c riteria for estuaries will be assessed annual ly . Since the duration and frequency components of the criteria must be consistent with the derivation of the magnitude component to provide a consistent and appropriate level of protection, the long

- term geome tric mean target cannot simply be applied as an annual mean. Doing so would result in unacceptab ly high Type I failure rate (identifying a healthy system as being impaired)

, since approximately 50 % of the individual years can be expected to be above the l ong

- term mean. Therefore, the long

- term target must be adjusted to allow for the application to a shorter duration with an acceptable Type I error rate of no more than 10 %.

An annual target concentration with an approximate 10 % Type I error rate for a giv en frequency can be derived by appropriately accounting for the annual variability above the mean. This annual target concentration can be derived as an upper percentile of the distribution of the annual geometric mean
concentrations

. Previous proposals by EPA have u s ed 3- year assessment periods to express the magnitude and duration nutrient criteria components. Although it is possible to construct a test that achieves the 10 % Type I error rate target, a slightly longer period ( e.g ., 5 years) will provid e better control for Type II error and will more fully capture climatic cycles ( e.g ., El Niño

, La Niña ), which tend to be longer than 3 years in Florida (and may actually be on a multidecadal scale). Furthermore, a 5- year period is more consistent with both the state’s 5

- year 303(d) assessment and permit renewal cycles.

Assuming a 5- year assessment period, it can be statistically determined that using the 75 th percentile of the annual geometric means from the long

- term dataset with a frequency and duration of no more than twice during the 5- year period will achieve the target ed 10 % error rate

. Therefore the proposed criteria will be applied such that the 75 th percentile of the annual geometric mean concentrations canno t be exceeded in more than 2 out of 5 years.

Summary of the Proposed Criteria

FDEP proposes that the magnitude component of protective nutrient criteria be expressed as a long

term geometric mean concentration target, derived as the geometric mean of the a nnual geometric mean concentrations from the long

- term baseline dataset plus a 10 % increase, which the EPA considers to be insignificant. The duration component of the criteria would be a 1- year assessment period

, with the annual target being expressed as the 75 th percentile for the geometric mean target based on a log

normal distribution. Finally, the frequency component of the criteria would be expressed as the annual target cannot be exceeded in more than 2 out of 5 years. The frequency and duration c omponents were designed to assess whether the interannual variability is consistent with the maintenance of the long

-Nutrient Criteria Technical Support Document Biscayne Bay

Draft 32 August 2010 term mean, considering natural variability around that mean. If the frequency and duration components of the criteria are satisfied, it can be concluded, with a known level of statistical certainty, that the long

- term target is also being achieved.

In simpler terms, the criterion would be expressed as a long

- term geometric mean nutrient concentration target derived as the long

- term geometri c mean nutrient concentration plus 10 % . The criteria would be applied such that the observed annual geometric mean nutrient concentration cannot exceed the annual target more than 2 out of 5 years , with the annual target being derived as the 75 th percenti le of the long

- term geometric mean target concentration.

Tables 11 through 13 provide t he proposed long

- term targets as well the annual limits for ea ch sub

basin in Biscayne Bay. The next step in finalizing the proposed criteria is to evaluate the similarities among the different sub

- basins to determine if any of the sub

- basins could be combined in respect to criteria development. The process of evaluating the similarities among sub

- basins is currently under

way , and the results will be provided on ce the analysis has been completed.

Table 1 1

. Proposed numeric nutrient criteria for all segments of the Biscayne Bay , including TP, TN, and chlorophyll a. For compliance purposes, the long term geometric mean shall not exceed the long term limit nor sha ll the average of all stations in a segment exceed the network average more than twice in a 5 year period. The last column shows the value which single station shall not exceed, by segment, more than twice in a 5 year period.

Total Phosphorus (μ g l -1 ) Existing Long Term Geometric
Mean Maximum Allowed Long
Term Geometric
Mean Annual Geometric Mean for a Network of Stations (2 of 5 year exceedence rate) Annual Geometric Mean for a Single Site (2 of 5 year exceedance rate) Manatee Bay

- Barnes Sound 6.90 7.59 10.13 10.28

South Central Outer

- Bay 5.20 5.72 6.69 6.88

South Central Inshore 5.88 6.47 7.70 7.90

South Central Mid

- Bay 5.31 5.84 7.06 7.31

Card Sound 5.90 6.49 7.87 8.04 Southern North Bay 7.86 8.65 9.98 10.19

North Central Inshore 5.59 6.15 7.49 7.62

North Central Outer

- Bay 6.35 6.98 8.13 8.30 Northern North Bay 9.86 10.84 12.22 12.45

Total Nitrogen (μ g l -1 ) Existing Long Term Geometric
Mean Maximum Allowed Long
Term Geometric
Mean Annual Geometric Mean for a Network of Stations (2 of 5 year exceedence rate) Annual Geometric Mean for a Single Site (2 of 5 year exceedance rate) Manatee Bay

- Barnes Sound 459 505 588 602

South Central Outer

- Bay 190 209 250 259Nutrient Criteria Technical Support Document Biscayne Bay

Draft 33 August 2010 South Central Inshore 391 430 504 518

South Central Mid

- Bay 282 310 365 371

Card Sound 257 283 350 370 Southern North Bay 231 254 299 304

North Central Inshore 247 272 325 329

North Central Outer

- Bay 221 243 286 289 Northern North Bay 235 259 310 315

Chlorophyll a (μg l -1 ) Existing Long Term Geometric
Mean Maximum Allowed Long
Term Geometric
Mean Annual Geometric Mean for a Network of Stations (2 of 5 year exceedence rate) Annual Geometric Mean for a Single Site (2 of 5 year exceedance rate) Manatee Bay

- Barnes Sound 0.50 0.55 0.89 0.91

South Central Outer

- Bay 0.21 0.23 0.27 0.31

South Central Inshore 0.28 0.31 0.38 0.39

South Central Mid

- Bay 0.25 0.28 0.34 0.36

Card Sound 0.34 0.37 0.52 0.55 Southern North Bay 0.85 0.93 1.10 1.15

North Central Inshore 0.32 0.36 0.46 0.50

North Central Outer

- Bay 0.49 0.54 0.72 0.79 Northern North Bay 1.41 1.55 1.81 1.86Nutrient Criteria Technical Support Document Biscayne Bay

Draft 34 August 2010 

### References

Banks, K., C. Beaver, J. Bohnsack, R.E. Dodge, D. Gilliam, and W. Jaap et al. 2005. The state of coral reef ecosystems of Florida. In: J. Waddell ( E d.), The state of coral reef ecosystems of the United States and Pacific freely associated states: 2005 (Silver Spring, MD: NOAA Technical Memorandum NOS NCCOS 11

, NOAA/NCCOS Center for Coastal Monitoring and Assessment’s Biogeography Team , p p. 150

– 200.

Biber, P.D.

, and E.A. Irlandi. 2006. Temporal and spatial dynamics of macroalgal communities along an anthropogenic salinity gradient in Biscayne Bay (Florida, USA). Aquat

. Bot

. 85: 65

– 77.

Bo yer, J.N.

, and H.O. Briceño. 2008

. 2007 cumulative annual report for the Coastal Water Quality Monitoring Network. Florida International University (FIU)

, Southeast Environmental Research
Center (SERC)

. Boyer, J.N., J.W. Fourqurean, and R.D. Jones

. 1999. Seasonal and long

- term trends in the water quality of Florida Bay (1989

– 1997). Estuaries 22:2B, 417

–

430.

Boyer, J.N., C.R. Kelble, P.B. Ortner, and D.T. Rudnick. 2009. Phytoplankton bloom status : Chlorophyll a biomass as an indicator of water quality condition in the southern estuaries of Florida, USA. Ecological Indicators 9s: s56

– s57.

Brand, L.E. 1998. Assessment of plankton resources and their environmental interactions in Biscayne Bay, Florida. Final report to Dade County Department of Environmental Resources Management. Miami, FL: University of Miami, Rosenstiel School of Marine and Atmospheric
Science.

———
. 2002. The transport of terrestrial nutrients to south Florida coastal waters. In: J.W. Porter and K.G. Porter ( E ds

. ), The Ev erglades, Florida Bay, and coral reefs of the Florida Keys (Boca Raton,
FL: CRC Press, pp. 361

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### Appendix A. Impaired Waters in the Biscayne Bay BasinNutrient Criteria Technical Support Document Biscayne Bay

Draft 39 August 2010Nutrient Criteria Technical Support Document Biscayne Bay

Draft 40 August 2010Nutrient Criteria Technical Support Document Biscayne Bay

Draft 41 August 2010Nutrient Criteria Technical Support Document Biscayne Bay

Draft 42 August 2010 

### Appendix B: Overview of FDEP Approaches for Nutrient Criteria Development in Marine
Waters

To be inserted.