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 toassess in shallow, productive aquatic systems due to frequentalgal blooms, high turbidity and sediment-resuspension events.We conducted a study to assess the distribution of suspendedparticles in Lake Okeechobee, Florida, utilizing both Landsat(1974–75) or Advanced Very High Resolution Radiometer(AVHRR) (1987) satellite remote sensing. Surface water sampleswere collected by helicopter to determine in situ chlorophyll-aand turbidity levels at 20 stations on four dates in 1974–75and six dates in 1987. Remotely sensed reflectance values agreedwell with in situ particle densities at the 20 in-lake stations(average R²: Landsat = 0.81, AVHRR = 0.53) and independent,synoptic boat mapping of algal blooms (r² = 0.79, P < 0.01).Basin-wide maps of chlorophyll and turbidity, as well as additionalspatial sampling, both indicated that these parameters are notnecessarily coupled in Lake. Our data concur with the hypothesisthat the spatial distributions of chlorophyll and turbidityare shaped by different forces. The highest concentrations ofchlorophyll occurred in the vicinity of tributary nutrient inputsat the lake's perimeter, while turbidity increased towards thecenter of the lake, reflecting predominant water circulationpatterns. ²Present address: Department of Biology & Romberg TiburonEnvironmental Center, San Francisco State University, San Francisco,CA 94132, USA ³Present address: Idaho Division of Environmental Quality, 1420North Hilton, Boise, ID 83706-1260, USA ⁴Present address: 5642 Santiago Circle, Boca Raton, FL 33433,USA