Havens, K. South Florida Water Management District, khavens@sfwmd.gov
Sharfstein, B. South Florida Water Management District, bsharfs@sfwmd.gov
East, T. South Florida Water Management District, teast@sfwmd. gov
Rodusky, A. South Florida Water Management District, arodusk@sfwmd.gov

 
LITTORAL PERIPHYTON RESPONSES TO NITROGEN AND PHOSPHORUS: AN EXPERIMENTAL STUDY IN A SUBTROPICAL LAKE
 
Portions of the natural littoral community in a subtropical lake were enclosed in 1.2 m. diameter mesocosms and subjected to high rates of nitrogen and/or phosphorus loading for 28 days. Changes in periphyton structure and function were compared with untreated controls to evaluate limiting resource effects. Mesocosms that received phosphorus additions displayed minor increases in whole-community metabolism measured by in-situ oxygen evolution during mid-day, and small increases in the chlorophyll a (CHLA) content of surface algal mats. Mesocosms that received nitrogen doses displayed significant increases in the CHLA content of epiphyton growing on submerged stems of Eleocharis. Striking treatment effects were observed when phosphorus and nitrogen were added together. In that case, there were highly significant increases in phytoplankton productivity, whole-community metabolism, CHLA content of surface mats, and CHLA content of epiphyton growing on artificial substrata and on submerged Utricularia. These results suggest that the community may have been co-limited by Phosphorus and Nitrogen, in contrast to previous findings of strong P limitation in more pristine regions of this marsh, and in the nearby Florida Everglades. The observed community responses may reflect early eutrophication effects, because the study site was located in close proximity to the lake's eutrophic pelagic region.
 
Day: Monday, Feb. 1
Time: 03:45 - 04:00pm
Location: Sweeney Center
 
Code: SS45MO0345S