ECOLOGICAL CHARACTERISTICS

o Atlantic coast estuaries from Biscayne Bay to Barnes Sound: natural salinities near seawater strength, clear, shallow waters, seagrasses, nursery ground for reef species.

o Florida Bay and associated fringing mangrove-lined embayments from Blackwater Sound to Garfield Bight: bank/basin/island topography, extensive seagrasses, nursery ground for pink shrimp, spotted seatrout, red drum, reef species, and others; lacks tidal influence in inner bay.

o River-dominated Gulf coast estuaries from Whitewater Bay to Lower Charlotte Harbor: extensive mangrove habitat.

o Florida Reef Tract: Clear, natural oligotrophic waters, rich biodiversity.

o The Florida Keys: remnant tropical hardwood hammocks and coastal strand vegetation communities, fringed by mangroves, sandy beach, or rocky shoreline.

o Associated nearcoast waters: relatively oligotrophic and semitropical representing a transition between offshore waters (Loop Current, Florida Current and Gulf Stream) and the coastal estuaries.

o Mainland edge: freshwater wetlands containing fringing, riverine, and basin mangrove communities; in places, a mud embankment that separates freshwater wetlands from brackish to marine wetlands and impedes freshwater runoff.

o All of the above environments have been altered by anthropogenic changes associated with the drainage and development of South Florida. In Florida Bay major dieoffs of seagrasses and mangroves, algal blooms, sponge kills and fisheries declines have been documented and are indicative of acute ecosystem stress.

o Area is affected by long term sealevel rise (Maul and Martin 1993) and similar rates of marine sedimentation. Marine carbonate sediments are derived from the skeletons of organisms that live nearby (Enos and Perkins 1977).

ECOLOGICAL RESTORATION OBJECTIVES

o Reestablish benthic habitats, particularly seagrass beds, to their predrainage spatial coverage, species composition, and biodiversity.

o Reestablish pre-development animal abundances and spatial distributions, restoring the natural community structure and biodiversity.

o Reestablish more natural spatial and temporal patterns of salinities in coastal estuaries and the frequency, intensity, duration, and areal coverage of hypersalinity in Florida Bay and other coastal estuaries, making negative salinity gradients less frequent.

o Reestablish spatial patterns of salinity that will provide optimum salinities in the predrainage locations of seagrass beds of various species. Salinity goals are: Halodule, 3-44 ppt; Syringodium, 24-35 ppt; Thalassia, 24-35 ppt; Halophila d., 35 ppt; Halophila e., 25-35 ppt; and Ruppia, 5-25ppt.

o Reduce or eliminate undesirable micro/macro algal blooms that adversely affect benthic organisms.

o Reduce or eliminate both plant and animal invasive introduced species.

o Increase hard coral community coverage.

o Reduce nutrient and contaminant loading.

o Restore natural volumes and timing o freshwater inflow.

o Restore secondary productivity supporting recreational and commercial fisheries.

o Restore the upland freshwater source to mangroves and other coastal wetland communities to restore their natural productivity and ecologically important detrital export to estuaries.

o Reestablish predrainage upland biological communities, both floral and faunal biodiversity, in the Florida Keys and the extreme southeastern coastal ridge and coastal plain of South Florida.

o Protect and restore endangered species and their habitats (i.e., turtles, crocodiles, manatees).

HYDROLOGIC RESTORATION OBJECTIVES

o Acquire "8 1/2 square mile residential area", "Frog Pond", and "Rocky Glades" in the East Everglades and the "Model Lands" in the C111 area and the "Triangle Area" between U.S. 1, SR 905, and Barnes Sound to restore short hydroperiod wetlands and reduce constraints on meeting many of the hydrologic objectives that follow.

o Reestablish predevelopment estuarine conditions by restoring a more natural quantity, quality, timing, and spatial distribution of freshwater inflow, both as ground and surface flow. To accomplish this, freshwater input must be permitted to be a function of rainfall timing and distribution, as attenuated and delayed by dynamic surface and groundwater storage (see Appendix II for procedure).

o Maximize the reestablishment sheetflow throughout the Everglades, Big Cypress, and other watersheds (i.e., move more water through wetlands and less through canals) and into the coastal estuaries including Florida Bay.

o Minimize or eliminate catastrophic flood control releases of fresh water into estuaries following storm events.

o Raise the water table and reduce water table recession rates so that base flow extends further into the dry season (at least through April).

o Reestablish predevelopment natural flow and circulation patterns by removing or modifying anthropo-genic barriers. Such barriers include the levees around the Water Conservation Areas, salt barriers at the coast, and fill associated with the Overseas Highway that retards water exchange between Florida Bay and the Atlantic. For instance, vertical slits to allow fish movements might be installed in salt barriers (Rogers et al. 1992).

o Redirect at least 90% of the total flow from canals into sheet flow across the mangrove zone fringing the inland shore of the estuary or covering the river tidal basin.

 

All percentage reductions or increases specified below should be calculated relative to the 5-yr average.

1. Canals emptying into western Biscayne Bay, Card Sound, and Barnes Sound (Manatee Bay)

a) No direct flows greater than 200 cfs into Manatee Bay through C-111 canal.

b) Redirect sheet flow through upper C-111 to Triangle Area and Manatee Bay and Barnes Sound re-establishing sheetflow.

c) Manage water levels in the east-west arm of the C-111 Canal to provide sheet flow to northeastern Florida Bay.

d) Redistribute 90% of the flow through Florida City Canal and North Canal as overland flow through the marl prairie and mangroves to enter Card Sound/South Biscayne Bay along a broad front.

e) Reduce by 50% the number of days annually that daily average discharge rates (including overland flow derived from the canal) exceed the upper limit of the fourth quartile in the lower Atlantic coast canals. Reduce by 50% the number of days with no flow.

2. Taylor Slough

a) Use water delivery plan for Taylor Slough prepared by Everglades National Park to obtain quantitative guidelines for restoring the natural quantity and timing of water flow into northern Florida Bay.

b) Raise operational stages in Canals L-31N/C-111 to mimic pre-drainage water levels along the eastern boundary of Everglades National Park in order to (1) restore natural hydroperiods and hydropatterns in Taylor Slough, (2) reduce seepage losses from the Rocky Glades and Taylor Slough, (3) reduce the frequency and magnitude of discharge through S197, and (4) increase the volume and duration of dry season flows into Florida Bay and the lower east coast estuaries. The following average operational stages should be established as guidelines.

    Feet above MSL

                       Wet                   Dry

Structure

S176              6.5                    5.5

S175              5.5                    4.5

S177                4.5                   3.5

S18c                2.5                   2.0

c) Establish oligohaline/mesohaline 0-18 ppt) conditions in the mangrove zone and inner bays from Long Sound west to West Lake) behind the Buttonwood Embankment. This would act to establish mesohaline/marine polyhaline (8-36 ppt) (Cowardin et al. 1979) conditions in northeastern Florida Bay.

d) Limit the number of days annually without freshwater inflow into Little Madeira Bay to roughly no more than that predicted by Natural System Model with the same rainfall.

e) Provide freshwater inflow to Little Madeira Bay and northeast Florida Bay that will result in appropriate salinities (see Appendix II) using Tabb's Florida Bay salinity-groundwater level relationship and groundwater levels estimated by the Natural System Model with the same rainfall.

f) Improve circulation in northeastern Florida Bay Place a bridge at Manatee Creek, removing the fill presently there. Restore the original cross-section of Jewfish Creek. Place culverts under US 1 north of the C-111 canal and south of Mile Marker 122.

3. C-111 area

a) Limit the number of days annually without freshwater inflow across the southern bank of the C-111 (into northeast Florida Bay) to roughly no more than predicted by the Natural System Model under same rainfall.

b) The peak daily average flows from canal mouth and canal-fed sheet flow should be no greater than that predicted by Natural System Model under same rainfall. Alternatively, no daily average flows should be greater than upper limit of the fourth quartile.

4. Shark Slough

a) Replace the present rainfall driven formula for water releases to Everglades National Park at the Tamiami Trail with a new formula that more nearly approximates the natural quantity and timing of water flow to Shark Slough from upstream, as suggested by the Natural Systems Model (ENP report in prep.).

b) Raise operational stages to mimic pre-drainage water levels along the eastern boundary of Everglades National Park (i.e., in Canal L-31N) in order to (1) restore natural hydroperiods and hydropatterns in Shark Slough; (2) reduce seepage losses from Northeast Shark Slough Fennema et al. 1994); and (3) increase the volume and duration of dry season flow into the mangrove estuaries downstream. The following average operational stages should be established as guidelines (M. Robblee, memo):

                            Feet above MSL

                                 Wet         Dry

Structure

S334                  8.0            7.0

G211                 7.5            6.5

S331/S173        7.0            6.0

Models such as the SFWM Model and the USGS Modbranch Model (Swain, in prep.) should be used to evaluate regional hydraulics associated with operational changes of the structures.

c) Restore sheet flow to the headwaters of Lostman's and other coastal rivers west of Shark Slough. Provide sufficient water to create salinities of 0-18 ppt through the mangrove zone during the wet season and 0-35 ppt through the mangrove zone during the dry season.

5. Golden Gate Canal System and Faka Union Canal emptying into Faka Union Bay

Reduce by 50% the number of days that the daily average discharge rate from the Faka Union Canal is greater than 200 cfs. Eliminate daily average discharge rates greater than 500 cfs. Reduce by 75% the number of days of zero flow (Browder et al. 1989).

 

CRITICAL LINKAGES

o Currents in Hawk Channel, which lies between the Florida Keys and the reef tract, move southwesterly through much of the year - counter to the flow of the Florida Current/Gulf Stream distributing Bay waters down the reef tract.

o Net flow across Florida Bay is from the Gulf to the Atlantic and the Florida Reef Tract.

o Ephemeral gyres form between the island chains and the Florida Current (Pourtales and Tortugas gyres). These gyres can markedly affect recruitment of reef species and possibly some Bay species.

o Florida Bay is strongly influenced by the waters of the West Florida shelf, which receive freshwater inflow from watersheds from the Everglades to at least the Peace River and carry it southeasterly into northwestern Florida Bay.

o Many reef fish species use the seagrass and mangrove habitats in the coastal estuaries including Florida Bay as nursery grounds. Some species make daily movements between Reef Tract refuges and seagrass and mangrove feeding grounds.

o The biota and water chemistry of the South Florida coastal systems are connected to the Greater Gulf of Mexico and Caribbean Area by a major western oceanic boundary current (Loop Current/Florida Current/Gulf Stream).

o Inland areas are the source of fresh water to these coastal systems. These include the Atlantic eastcoast ridge and its associated waterways, the southeast Everglades (C-111 area), the Taylor and Shark Slough watersheds and their headwaters; the Big Cypress; Immokalee Rise; including the Okaloacoochee Slough; Fakahatchee Strand; and western Collier County.

o Surface and soil water spatial distributions, through evapotranspiration, affect convective rainfall patterns, which help to drive the overall hydrologic cycle across of South Florida.

o Migratory marine species, including the protected sea turtles and manatees, move seasonally to waters along both Florida coasts and use South Florida estuaries, including Florida Bay, as seasonal and/or developmental habitat.

SUCCESS CRITERIA

o Tortugas shrimp harvests restored to recent historic levels. For example, the long term trend prior to the 1980s centered around a maximum sustainable yield (MSY) of about 10 million pounds annually.

o Restoration of fisheries resources requires a measurement of habitat carrying capacity. One indicator of carrying capacity is recruitment of age 0 or 1 fish because the number of recruits at this age is dependent upon how much resource is available. Spotted seatrout in the Bay is considered a unit stock (Iverson and Moffett 1962). Seatrout have been historically the second most harvested recreational species in the Bay. Recruitment has been increasing since 1974. However, laboratory studies have shown that increased salinities will decrease egg survivorship (Gray et al. 1991). Recovery is achieved when long term mean abundance levels are at carrying capacity.

o The population of common snook in Florida Bay is considered a unit stock. Snook was given special protection because of dramatic declines in catch rates. Recovery is achieved when long term mean abundance equals carrying capacity levels of abundance.

o Gray snapper are estuarine dependent and recruited from adjacent water into the Bay (Rutherford 1983). Recruitment decreased from 1974 through 1985. Restoration of gray snapper has been defined by mean annual abundance equal to carrying capacity.

o Annual commercial landings for spiny lobster have fluctuated since 1975 from 4.3 to 7.9 million pounds. Estimated landings for 1992 are 5.9 million pounds, which is 1.7 million pounds less than in 1991 (Harper 1993). The management objective is to maintain average annual landings of about 7.0 million pounds. This requires restoration of the larval and juvenile habitat (loggerhead sponges). Sponge dieoffs in the Bay have been coupled to a marked decline in juvenile lobster (Anon. 1992). In this case, the best success measure is a restoration of sponge populations over their historic range.

o Jewfish are most abundant in waters off the Florida Keys and southwest Florida in waters less than 150 feet. Fishing for this species has been prohibited since 1990 because of significant declines in landings since the 1960's. Increased sightings of jewfish would suggest population numbers are increasing.

o Historic coastal wading bird colonies repopulated; frequency of successful nesting seasons increasing; increasing longterm trend in total fledgling production.

o Recovery of osprey and brown pelican populations to predrainage population levels.

o The South Florida estuarine and Bay waters historically had enough turtles to support an active fishery. Absolute abundance of turtles is not available for any time period. However, degradation of seagrasses will prevent utilization of this area as a developmental habitat. Increased sightings as an index of recruitment will indicate recovery.

o Manatees are year-round residents of South Florida' coastal estuaries. Their presence is dependent upon adequate freshwater flow. Recovery of manatees in this system will be indicated by increased sightings of manatees in the bay system

o Percent living coral varies from reef to reef through the Keys. An increase in coral cover by 15-20% over present levels at any individual reef will result from improved water quality and indicates recovery.

o Coverage and species composition of seagrasses restored to historical distributions. The mid-1980's level is the only benchmark available for indexing restoration. The coverage and composition has been defined according to regions within the Bay (Zieman et al. 1989, Thayer and Chester 1989).

o The distribution and growth of crocodiles is related to seasonal fluctuations in salinities. Habitat availability for this species has been identified as the critical factor in the recovery of this species. In the 1970's it was estimated that only 20 nests were laid. Restoration of this species is entirely dependent upon Florida Bay and Southern Biscayne Bay (Card and Barnes Sounds). Restoration is indicated when crocodile nesting success increases to recovery plan levels of 60 nests per year in this area.

o Blue-green algal blooms virtually eliminated from Florida Bay.

o Frequency, intensity, and areal coverage of other algal blooms in Florida Bay and nearshore shelf waters reduced to levels that will permit the recovery of benthic communities.

o Contaminant and nutrient concentrations reduced to historic levels for the various environments.

o Maintenance in Florida Bay of more natural salinity patterns, as suggested by Tabb's (1967) well level-salinity relationship, linked to well levels simulated by the natural system model (McIvor et al. 1994).

o Salinities rarely exceeding 35 ppt at any time in any part of Florida Bay.

o Maintenance of a breeding population of 6000 pairs of White Crowned Pigeons in Florida Bay (Paul 1977, Strong et al. 1994).