Evaluation of the Effects of Nutrient Removal and the “Storm of the Century” on Submersed Vegetation in Kings Bay – Crystal River, Florida

ABSTRACT

Municipal wastewater effluent was removed in 1992 from a cove (Cedar Cove) of Kings Bay in an attempt to reduce the bay's ambient total phosphorus (TP) and total nitrogen (TN) concentrations. Many citizens and professionals viewed nutrient removal as the solution to reducing the bay's nuisance growths of aquatic macrophytes and filamentous algae. Wastewater removal reduced average TP from 105 μg·L⁻¹ to 27 μg·L⁻¹ and average TN from 620 μg·L⁻¹ to 220 μg·L⁻¹ in Cedar Cove. TP (24 μg·L⁻¹ to 28 μg·L⁻¹) and TN (300 μg·L⁻¹ to 260 μg·L⁻¹), however, were not significantly reduced in southern Kings Bay. There were no significant changes in mean frequency of occurrence of vallisneria in Cedar Cove (0% to 1%) or southern Kings Bay (19% to 22%). Average hydrilla occurrence decreased significantly after wastewater removal in Cedar Cove (54% to 36%) and southern Kings Bay (61% to 35%). Eurasian watermilfoil occurrence significantly increased in Cedar Cove (6% to 24%) and southern Kings Bay (11 % to 32%). Filamentous algal occurrence in Cedar Cove averaged 34% prior to and 40% after wastewater removal. In southern Kings Bay, the frequencies of occurrence averaged 5% and 2%, respectively. If removal of Crystal River's wastewater discharge was responsible for the differences detected in plant abundances, die same reductions/increases in species abundance should not occur in Cedar Cove as in southern Kings Bay. Significant changes in plant occurrence were attributed to the March 13, 1993 “Storm of die Century,” not to die removal of wastewater. Further nutrient control is not recommended as an option for reducing nuisance growths of submersed aquatic vegetation in Kings Bay-Crystal River, Florida.

Key Words:

• eutrophication
• nutrients
• macrophytes
• wastewater
• rivers
• Crystal River
• Florida