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Ecological Risks in the Caloosahatchee Estuary: A Conceptual Model Developed through the Southwest Florida Feasibility Study Darren Rumbold, Ph. D Professor of Marine Science Depart. of Marine and Ecological Sciences Coastal Watershed Institute Florida Gulf Coast University
Southwest Florida Feasibility Study (SWFFS) Purpose and Relationship to Comprehensive Everglades Restoration Plan (CERP) and Critical Projects The Restudy recommended a separate Comprehensive watershed study for Southwest Florida with the following purposes • Health of aquatic ecosystems • Water flows • Water quality (including appropriate pollution reduction targets) • Water supply (Lower West Coast Water Supply Plan) • Flood damage reduction • Wildlife and biological diversity • Natural habitat • Recreation (opportunity)
Benefits of Developing Conceptual Models? • The process of creating a conceptual model is a powerful learning tool. • Conceptual models are easily modified as knowledge increases. • Conceptual models highlight what is known and not known and can be used to plan future work. • Conceptual models can be a powerful communication tool. They provide an explicit expression of the assumptions and understanding of a system for others to evaluate. • Conceptual models provide a framework for prediction and are the template for generating more risk hypotheses.
Drivers • • • Sea Level Rise Water Management Land Use & Management • Maintaining Navigation Stressors • Altered Estuarine Salinity • Altered Hydrology • Input & Elevated Levels of Nutrients, Dissolved Organics & Toxins • Boating & Fishing Pressure • Physical Alteration to Estuary
Altered Salinity Regime • While estuarine species are generally well adapted to cope with varying salinity conditions, larger shifts and timing of freshwater discharges can be a problem. – impacts the community structure and function of phytoplankton, submerged aquatic vegetation (SAV), macroalgae, benthos- particularly oysters and fisheries • Secondary, or indirect, effects on manatee demographics and wading bird community structure
Important to Clearly Identify and Communicate Cascading Adverse Effects • Primary, or direct, effects: – occur when a stressor acts directly on the assessment endpoint and causes an adverse response • Secondary, or indirect, effects: – occur when the entity’s response becomes a stressor to another entity – are often a series of effects among a diversity of organisms and processes that cascade through the ecosystem – may have greater ecological significance than primary effect
Increased Nutrients & Contaminants • Biostimulants, e. g. , inorganic and organic nutrients, influence growth and community structure of phytoplankton, macroalgae, and microbes. – Indirect effects on SAV, zooplankton, fish and other aquatic organisms from: 1) light attenuation, 2) altered dissolved oxygen concentrations, and 3) biotoxins • which, in turn, can have cascading effects on manatee, dolphins and wading bird community structure
Cloern 2001, Marine Ecology Progress Series
Table 1. Summary of findings of water quality assessments in the Caloosahatchee Estuary, San Carlos Bay, Pine Island Sound and Matlacha Pass.
Table 1. Continued.
Increased Nutrients & Contaminants • Toxicants, both metals and organics (e. g. , pesticides, pharmaceuticals and personal care products) could be having insidious effects on individuals (e. g. , immunosuppression, behavior, etc. ) populations and community structure. – Loss or contamination of prey can have indirect effects on fish and wildlife predators (e. g. , sharks, dolphins, birds), as well as human consumers
Input parameters might include: water-column BOD, COD; sediment oxygen demand; adsorption coeff. , particle-size distribution, settling coeff. ; rates of nitrification, denitrification, mineralization and fixation; reaeration rate (SA/vol. , temp. , turbulence, stratification, algal growth, photosynthesis, respiration, settling rates; light avail. (note, inter-dependence). Basin e. g. , C 43, Tidal Caloosahatchee, Estero, and BCB Loading model WQ PERFORMANCE MEASURE Parameter Target ; causal, response or both WQS; Component specific Process model, e. g. , ECOlab Inflow v. outflow concentration loads tion ntra once s c load Empirical model, e. g. , regression TSS; Turbidity DOC / DOM; TN (NOx + TKN); TP, SRP Historical-based, e. g. , natural systems, OFW, etc. s Reference site, Process model, e. g. , ECOlab e. g. , 10 K Island, 25 th - 75 th percentile for a given salinity regime Empirical model, e. g. , regression conc entr ation load BMP effectiveness as % reduction Constraint Fraction of Freshwater Method, i. e. , mass balance Input parameters will include: Land use Soils Topography Land use-specific event mean conc. Land use-sp. runoff coefficient Many other simplifying assump. Dissolved Oxygen; Chl-a; Color; Clarity / PAR BP J Coordinate w/ Natural Systems Group HS Im od el; BP J Eco-resource, e. g. , SAV, oysters, redfish; sawgrass Habitat Units, NEED TO CONNECT THE DOTs Output Scale ? ? ? Instantaneous minimum ---Seasonal means Point - River segment - Spatially explicit e. g. , acres, lbs, Catch per unit effort
Cloern 2001, Marine Ecology Progress Series Simultaneous Effects of Multiple Stressors “The presence of multiple stressors may either increase or dampen the temporal and spatial variability seen in aquatic systems, depending on the interactions among stressors and the influence of background environmental conditions and sensitive species on the expression of stressor effects. ” (Breitburg et al. 1999)
Breitburg et al. 1999
Take Home Message • Many people invested an incredible amount of time and energy in the SWFFS developing decision-support products such as the conceptual model • Although those products should serve as a strong foundation, they can be improved upon and expanded, especially the predictive models linking stressors with eco-resources • We are not under the same constraints as SWFFS and so can develop an analysis plan for research to fill data gaps, particularly on simultaneous effects of multiple stressors and indirect effects