CHANS: The Spatial-Temporal Distribution of Karenia brevis on the West Florida Coast and its Relationship to Precipitation and River Discharge.

A project sponsored through the Coupled Natural and Human Systems program has examined relationships between harmful algal blooms, environmental factors, and the associated human health and economic impacts in coastal communities. Linkages between bloom dynamics and river discharge have been previously studied over intervals of a few years or less. Here a record of Karenia brevis data spanning 20 years along the West Florida Coast was utilized to examine spatial and temporal patterns during five major bloom events. Approximately 63,000 cell count measurements from 1994-2013 were analyzed to define the time series of a ‘center of mass’ location for each bloom event. This approach provides a complementary perspective to the work of Moanga et al (2015) which included an ArcGIS hotspot analysis to define areas of high cell counts. The center of mass analysis corroborated patterns of bloom movement and development in the hotspot analysis, and revealed previously unrecorded patterns. Cell counts were evaluated with rainfall and river discharge data to define possible monthly and seasonal linkages at the mouths of five West Florida estuaries. Correlations between discharge and K. brevis abundance within 10 km of the estuary mouths indicated a very weak, yet positive, relationship with lags of 1 to 4 months. Maximum discharge lagged seasonal precipitation in individual watersheds by one to several months. An analysis of aggregated monthly cell counts and discharge rates indicated patterns of seasonal maxima with differences in median cell counts varying by as much as an order of magnitude. These relationships suggest a possible riverine effect on cell counts that is minor relative to peak abundances, but a potential important influence on bloom dynamics and worthy of further investigation.