SBEP study contributes to regional understanding of tidal creeks

The Sarasota Bay Estuary Program (SBEP) recently completed its second regional study on tidal creek nutrient dynamics. Both studies were funded through the Environmental Protection Agency (EPA) Region 4 Wetlands Program Development Grant program. The first study resulted in the development of a nutrient management framework for southwest Florida tidal creeks. This follow-up study focused on:

• validating outcomes of the initial study,
• refining the nutrient management framework and
• identifying additional indicators of tidal creek condition to refine nutrient targets and thresholds that protect the biological integrity of these critical natural resources.

The current study also produced additional indicators to help managers pinpoint potential causes of nutrient imbalance. These indicators include:

• A chlorophyll to nitrogen threshold ratio no greater than 15, above which indicates creeks that may be physically altered or have their hydrologic connection to the estuary cut off.
• A trophic state index score less than 60, which places a creek in the “fair” category for estuarine waters. A macrophye index (similar to Florida Department of Environmental Protection’s rapid periphyton index) based a frequency of occurrence of less than 50% of samples with macrophytes present.
• A total nitrogen annual geometric average concentration of 1.1 mg/l, based on a weight-of-evidence that higher concentrations are associated with an increased frequency of creeks in the “caution” category.
• A nitrate ratio less than one between source (fresh) and estuarine water. This indicates that dissolved inorganic nitrogen should be assimilated quickly within the tidal p