Florida Bay Research Programs and Their Relation to the Comprehensive Everglades Restoration Plan (2002)

Because the Comprehensive Everglades Restoration Plan (CERP) is an ambitious and comprehensive enterprise, with a long time horizon, it is critical that it be responsive to new information as it becomes available from the extensive ongoing research and monitoring programs throughout south Florida. One important assumption often made by scientists and managers associated with the planned restoration of the Everglades, and by the public, is that the increased flows of water deemed necessary to restore the extensive wetland marsh habitats of the Everglades also will contribute to the restoration of Florida Bay. However, the scientific evidence suggesting that the CERP may change the marine environment in ways that are not fully understood, and may be perceived as undesirable, is sufficiently persuasive that the issue should be the subject of a focused technical review and evaluation. This review should be carried out as an early activity within the FBFKFS so that the conclusions can have an influence on early stages of Everglades restoration planning. The results of this analysis need to be evaluated by resource managers and planners of CERP so that appropriate consideration and management actions can be taken.

Major considerations leading to this position are as follows: (1) While it remains debatable how much new freshwater flow will enter the Bay proper because of the CERP, recent physical observations demonstrate that there is commonly a hydraulic connection, albeit with seawater mixing and a time lag, between Shark River Slough discharge and the interior of Florida Bay. (2) Some fraction of the DON (dissolved organic nitrogen) that would accompany increased freshwater flows from the Everglades will likely be available, either directly or indirectly, to support undesirable algal blooms within Florida Bay. (3) Finally, enhanced blooms of phytoplankton and/or macroalgae may reduce seagrass cover and expose sediments to resuspension. Such resuspension will increase turbidity within the Bay and contribute to additional seagrass loss.

Thus, the consequences of the CERP may be a Florida Bay that differs markedly from the “gin clear” bay of the 1960s and 1970s. The CERP goals, if achieved, may instead result in conditions in Florida Bay that are not viewed in a positive light by the public. These conditions may include increased frequency, extent, and duration of phytoplankton blooms, as well as macroalgal blooms, both of which may threaten seagrass distribution.

The importance of this issue has been recognized by some partners in the Florida Bay and CERP research communities, and several projects are underway or will soon begin that will be helpful in addressing it. Research in the following areas is particularly important:

• Some components of the water budget for the Bay are poorly known, but understanding these fluxes is critical for evaluating the water quality in the Bay. In particular, estimates of groundwater discharge to the Bay differ by many orders of magnitude. Although this discharge is saline it may be a significant source of nutrients. Moreover, the higher water levels produced by the CERP may affect the magnitude of these fluxes and, in extreme cases, may result in direct discharge of fresh groundwater to the Bay. Also of importance to both salinity and nutrient fluxes is a full characterization and quantification of

surface runoff in Taylor Slough, the Craighead Basin, the C-111 canal (Eastern Panhandle), and Shark River Slough, including the seasonality of flow. Diffuse seepage through the Buttonwood Embankment should also be investigated.

• On the basis of modeling, annual freshwater flows through the Taylor Slough/Craighead Basin region to Florida Bay in 2050 will be about the same (127,000 acre-ft per year; 15.7x10⁷ m³/year) under the expanded CERP scenario D13R4 as in the simulated current condition of 126,000 acre-ft per year (15.5x10⁷ m³/year). Thus, this particular hydrologic component of the CERP is unlikely to affect salinity levels in the northeastern Bay. At the same time, annual freshwater flow through Shark River Slough, some of which migrates to the Bay indirectly and with a time lag, is projected to increase by almost 80% under the CERP scenario D13R4. The effects on nitrogen and phosphorus fluxes of increasing this freshwater flux to the Bay’s diffuse northwestern boundary need to be quantified.

• Total loads of nitrogen from freshwater sources should be estimated as accurately as possible. A better understanding of the transport, bioavailability, and rates of transformation of DON and DOP (dissolved organic phosphorus) into forms that can be used by algae and macroscopic aquatic plants) of dissolved organic nitrogen is needed to provide insight into the effects of increases in nutrient-bearing freshwater flows to the Bay. Quantifying the magnitude of nutrient loadings by source (e.g., organic soils oxidation, urban and agricultural runoff, and regional atmospheric deposition) also will become relevant if steps to reduce nutrient loading to the Bay become necessary.

• A historical characterization of the Bay’s water quality would be very useful for a perspective on restoration goals. Such a characterization would be based on anecdotal as well as any scientific information available.

• There currently is no Florida Bay circulation model suitable for research and management purposes, although there are several candidates; such a model is essential to support a Bay water quality model and thus facilitate analysis of CERP effects on the Bay. The difficult and time-consuming tasks of selection, development, and application of a circulation model and water-quality model for the Bay should be key components of the Florida Bay & Florida Keys Feasibility Study.

• To evaluate the effects of the CERP on Florida Bay, there must be a linkage of the output of the South Florida Water Management Model (SFWMM), which has a southern boundary of the mangrove zone, and input to the Bay models. One possibility for bridging this gap is the USGS TIME model, but its readiness for this purpose probably will not occur until well into 2003. The USGS SICS model (an early version of TIME) already is being used for this purpose in the Taylor Slough/C-111 canal area, although not formally interfaced to any Bay models. Additional questions of temporal and spatial resolution must also be resolved. Another option is the similarly structured SFWMD South Florida Regional Simulation Model (SFRSM), also currently under development. An interagency agreement on which model will most usefully serve as an interface between landside hydrologic and Bay hydrodynamic modeling is needed.

• Estimates of the influence of the CERP on Florida Bay inferred from statistical and time series analysis of existing data and/or use of simpler “box models” such as FATHOM (Flux Accounting Tidal Hydrology Ocean Model) may be usefully employed while awaiting development of full-scale simulation models.

• Human factors such as population growth and economic activity; and environmental events whose drivers are distant from Florida Bay and unrelated to CERP activities, such as hurricanes, flooding of the Mississippi River, atmospheric deposition of nutrients from emission sources remote to Florida Bay or its watershed, and sea-level rise; also may influence local conditions in Florida Bay. Research is needed to better define these potential effects and to integrate the results into predictive ecosystem-response models.

There is much to commend in the overall research effort in Florida Bay, and in the goals of the FBFKFS. But the evidence of potential changes in Florida Bay that will be caused by the CERP is sufficiently persuasive that the process of evaluation should begin as an early part of the FBFKFS. The

effort required for all these tasks is daunting. Sufficient time and resources should be made available as part of the FBFKFS for essential research to ensure its success and usefulness for management decisions.