RELATIONSHIPS BETWEEN WIND VELOCITY AND UNDERWATER IRRADIANCE IN A SHALLOW LAKE (LAKE-OKEECHOBEE, FLORIDA, USA)

Relationships between wind velocity and the vertical light attenuation coefficient (K-0) were determined at two locations in a large, shallo w lake (Lake Okeechobee, Florida, USA). K-0 was significantly correlat ed with antecedent wind conditions, which explained as much as 90 perc ent of the daily variation in K-0. Sub-surface irradiance began to cha nge within 60 to 90 minutes of the time when wind velocity exceeded or dropped below a threshold value. Maximum one hour changes in K-0 were > 50 percent, however, 20 to 30 percent changes were more common. The magnitude of change in K-0 varied spatially based on differences in s ediment type. K-0 never exceeded 2.8 at a location where bottom sedime nts were dominated by a mixture of coarse sand and shells. In comparis on, K-0 exceeded 9 during episodic wind events where the bottom sedime nt was comprised of fine grain mud. Underwater irradiance data can be used to determine threshold wind velocity and account for the influenc e sediment type has on K-0. Once a threshold velocity has been establi shed, the frequency, rate, and duration of expected change in underwat er irradiance can be evaluated. This is critical information for scien tists who are studying algal productivity or other light-related pheno mena.