PARENT SESSION
Oral Session # 15: Wetland Ecology I: The Everglades and Southern Wetlands.
Presiding: J Chick
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 101.
A bayesian estimaton of phosphorus thresholds in the Everglades.
Richardson , Curtis *,1, King, Ryan 2, Qian , Song 3, 1 Duke University, Durham, NC2 Smithsonian, Edgewater, MD3 Cadmus, Chape Hill, NC
ABSTRACT- The Florida Everglades, an internationally designated wetlands of importance, is currently undergoing a significant shift in its native flora and fauna due to excessive loadings of total phosphorus (TP) from agricultural runoff and Lake Okeechobee outflow. However, the surface-water TP threshold for sustaining the Everglades is unknown. Here, we present long-term experimental research and show that a surface water geometric mean TP concentration of 15 ug/L maintains an ecological balance in algal, macrophyte, and macroinvertebrate populations as well as slough community structure. Our results from a 6 year phosphorus (P) dosing experiment in the Everglades suggest that the 10 ug/L P threshold often given for average annual concentrations in oligotrophic waters (natural pristine lakes) is not appropriate for defining oligotrophic wetland status in the Everglades due to differences in ecosystem structure (periphyton versus phytoplankton) seasonal water depth affects on P concentrations, and natural nutrient gradients (i.e., higher exterior nutrient concentrations in wetlands gradate to lower interior nutrient levels) that exist in wetlands versus lakes. Importantly, the ecological responses to TP in the Everglades are highly predictable, but estimates of uncertainty must be utilized to accurately define threshold responses, which change with seasons and water depths. Our Bayesian change point methodology used to address ecological imbalance along nutrient gradients is applicable to other aquatic ecosystems.
Key words: Phosphorus , oligotrophic , Everglades , trophic level