Date

Summer 2019

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)

Department

Moss Landing Marine Laboratories

Abstract

Phytoplankton form the base of the marine food web and provide important subsidies to the nearshore and intertidal communities. In the California Current Ecosystem (CCE), high phytoplankton abundance is largely attributed to seasonal equatorward alongshore winds which drive coastal upwelling. At shorter temporal and spatial scales, nearshore phytoplankton abundance is highly variable and sensitive to local oceanographic conditions and the influence of wave-induced interactions. Between 2008 to 2012, periods of rapid onset high phytoplankton abundance (n=41) were identified during the upwelling season (March to October) in the intertidal environment of Bodega Head, in Northern California. The rapid accumulation of phytoplankton occurred at short latencies (~20 hours) and was correlated with increases in offshore alongshore wind stress and significant wave height. Wave-induced transport, known as Stokes drift, was calculated from a nearshore wave model, providing a physical mechanism to advect and trap phytoplankton in the nearshore. A surface particle tracking model forced by High-Frequency Radar-derived surface currents revealed that the majority of water masses during the high phytoplankton events originated from offshore to the north, suggesting that waters originated from the Point Arena upwelling center. Stokes drift, which is reinforced by alongshore winds, provides a transport mechanism for linking large scale offshore processes with the nearshore environment. This study underscores the importance of considering Stokes drift when examining biophysical interactions in the nearshore environment.

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