Multidisciplinary oceanographic studies of a small island in the Southern California Bight

Small islands play a strategic role in the fisheries, tourism and military activities of the Southern California Bight (SCB). They are also ideal systems to study coastal processes such as the formation of eddies, fronts, wakes and upwelling systems. A literature review on the subject reveals that research on this topic is abundant but still uneven and single disciplined. Biologists first described increases in productivity near islands but they explained this as an ill defined “island mass effect,” whereas when physicists investigated eddies, upwelling regions and fronts around islands they called these “island wakes.” Only a few recent investigations integrate both physics and biology to fully describe the biological consequences of physical forcing phenomena due to the presence of an island. In my work I focused on Santa Catalina Island as the first case study of the island mass effect for the Southern California Bight. I combined the use of in situ surveys (using simultaneous CTD-Conductivity Temperature Depth, and net sampling), satellite remote sensing data (AVHRR-Advance Very High Resolution Radiometer and SAR-Synthetic Aperture Radar) and numerical model simulations from ROMS (Regional Ocean Model System) to study the effect of the island's bathymetry to the incoming ocean currents and its consequent effect on the local productivity. Results have shown the distinct formation of wind versus current wakes on opposite sides of the island. Wind sheltering effects in the wind wake of Santa Catalina Island served as a basis to interpret the decrease in surface mixing due to weaker inshore winds and an increase in SST, frequently observed during spring and summer months inshore for the whole SCB. Island wind wakes tend to function as important retention zones whereas current wakes serve to bring nutrients to the euphotic zone, maximizing productivity. Also apparent was a statistically significant difference between mesozooplankton communities that live within the island's shelf and those offshore from it. Catalina Island sustains a unique pelagic, shelf ecosystem.