Havens, K. E. South Florida Water Management District, khavens@sfwmd.gov
Steinman, A. D. South Florida Water Management District, astein@sfwmd.gov
Hwang, S. South Florida Water Management District, soonjinh@chollian.net

Phosphorus (P) uptake and release by periphyton and plankton were studied in shallow (mean depth = 2.7 m) Lake Okeechobee, Florida, USA. Studies were conducted using 32P-labelled inorganic (DIP) and organic (DOP) phosphorus and laboratory conditions simulating ambient temperature and irradiance. At near-shore sites with high bioavailable (BAP) concentrations (4 ug/L) and low irradiance (Iz = 0.3% of Io), uptake of DIP (normalized annual mean) primarily was by phytoplankton (14 mg/hr) and bacteria-plankton (4 mg/hr). Phytoplankton dominated DOP uptake (4 mg/hr). Uptake of P by epiphyton and epipelon was <1 mg/hr. At a littoral site with low BAP (<1 ug/L) and high irradiance (Iz = 36% of Io), bacteria-plankton dominated DIP uptake (11 mg/hr), and uptake by epiphyton was similar to phytoplankton (2 mg/hr). DOP uptake also was dominated by bacteria-plankton (10 mg/hr), and there was substantial uptake by phytoplankton (3 mg/hr), epiphyton (>1 mg/hr), and epipelon (4 mg/hr). At all three sites, DIP and DOP release rates were <10% of uptake. There may be competition between periphyton and plankton for P in this lake, with relative rates of uptake influenced by irradiance and water column P. Bacteria-plankton played an unexpectedly important role in P cycling under both eutrophic and oligotrophic conditions.
Day: Monday, Feb. 1
Time: 03:30 - 03:45pm
Location: Sweeney Center
Code: SS45MO0330S