THE INFLUENCE OF WATER CIRCULATION ON CHLOROPHYLL-TURBIDITY RELATIONSHIPS IN LAKE OKEECHOBEE AS DETERMINED BY REMOTE-SENSING

The spatial distribution of phytoplankton can be difficult to assess i n shallow, productive aquatic systems due to frequent algal blooms, hi gh turbidity and sediment-resuspension events. We conducted a study to assess the distribution of suspended particles in Lake Okeechobee, Fl orida, utilizing both Landsat (1974-75) or Advanced Very High Resoluti on Radiometer (AVHRR) (1987) satellite remote sensing. Surface water s amples were collected by helicopter to determine in situ chlorophyll-a and turbidity levels at 20 stations on four dates in 1974-75 and six dates in 1987. Remotely sensed reflectance values agreed well with in situ particle densities at the 20 in-lake stations (average R(2): Land sat = 0.81, AVHRR = 0.53) and independent, synoptic boat mapping of al gal blooms (r(2) = 0.79, P < 0.01). Basin-wide maps of chlorophyll and turbidity, as well as additional spatial sampling, both indicated tha t these parameters are not necessarily coupled in Lake Okeechobee. Our data concur with the hypothesis that the spatial distributions of chl orophyll and turbidity are shaped by different forces. The highest con centrations of chlorophyll occurred in the vicinity of tributary nutri ent inputs at the lake's perimeter, while turbidity increased towards the center of the lake, reflecting predominant water circulation patte rns.