CONTRASTING PHYTOPLANKTON BLOOM PATTERNS ALONG A RIVER-TO-OCEAN CONTINUUM IN THE NORTHERN CALIFORNIA CURRENT SYSTEM

The coastal margin environment is highly physically dynamic, which strongly influences phytoplankton distributional patterns. Phytoplankton blooms develop through a combination of retention, high rates of growth, or slow rates of loss, and it is often difficult to discern which factors contribute to patterns in time series data, particularly when supporting data are not available or complete. We used a time series of observations from a network of in situ biogeochemical sensors located along a river-to-ocean continuum to formulate hypotheses about the primary factors driving changes in phytoplankton standing stocks in river, estuarine, and coastal waters and to relate temporal variability in standing stocks to these drivers. Fluctuations in phytoplankton standing stocks in the three environments were related to hydrologic forcing, seasonal changes in estuarine circulation, and upwelling/downwelling events, respectively, which produced different patterns of variability in standing stocks. We discuss bloom characteristics in each of these contrasting environments in an effort to distinguish factors that modulate phytoplankton populations within time series data.