Florida Lake Management Society Annual Conference, Naples, Florida, June 4 – 7, 2007
LOOKING FOR CORRELATIONS IN A LAKE WITHOUT LIMITING NUTRIENTS
Sherry Brandt-Williams, Ph.D. St. Johns River Water Management District Palatka, FL
When strong correlations exist between nutrient concentrations and biological responses
or other physical parameters in aquatic ecosystems, the curve defining the relationship can be used to identify critical causative thresholds. Examples of these thresholds are the nitrogen to phosphorus ratio that triggers growth of nitrogen-fixing phytoplankton or the phosphorus concentration that corresponds with light intensity insufficient to sustain submerged aquatic vegetation. These correlations can then be used to define target concentrations for nutrients that would theoretically create conditions conducive to the water quality goals in lake restoration and management plans: e.g., water quality that allows optimum coverage of submerged aquatic vegetation, improving overall habitat. Ambient water quality data for many lakes exhibit significant relationships between key analytes and several biological responses. However, Lake Jesup, with nutrient concentrations typically well in excess of phytoplankton demand and a large seasonally inundated floodplain wetlands does not exhibit strong and persistent relationships to nutrients alone. The results of analyzing ten years of water quality and hydrology data demonstrate the need to consider both when setting nutrient criteria for meeting water quality
restoration goals on Lake Jesup.
Session 5A – Page 8