Coastal Oceanic Zone
Upwelling is the primary source of nutrients derived from the ocean near the coast. The extent of upwelling varies considerably along the west coasts of North and South America. If nutrient inputs from land play a significant role in coastal production anywhere, their influence should be greatest in regions with limited ocean sources of nutrients. Although a strong upwelling area is located in the vicinity of Point Conception at the west end of the Santa Barbara Channel, major upwelling does not occur off most of southern and Baja California, including the Santa Barbara Channel. As a result, surface waters in the SBC region are commonly warm, saline, and relatively nutrient poor compared with waters north of Pt Conception or in the California Current.
The coastal oceanic zone receives runoff from land containing: sediments, various naturally occurring organic and inorganic substances of terrigenous origin, and organic and inorganic substances of anthropogenic origin. The spatial extent of the coastal ocean influenced by runoff is determined by several factors including the magnitude, rate and timing of runoff, particulate concentration in runoff waters, wind, ocean currents, ocean water column structure, and waves.
Seasonal flow patterns and water mass distributions suggest that the timing and strength of winter runoff events may be very important in determining how terrestrial inputs disperse through coastal reef habitats of the Santa Barbara Channel. Cyclonic circulation, as illustrated by the high frequency (HF) radar data for surface currents shown to the left, is seasonal in the channel. When runoff occasionally occurs between May and October during cyclonic circulation in the western channel, westward advection of terrestrial materials along the mainland is expected. In contrast, during more normal periods of runoff in winter and early spring when cyclonic circulation is absent, eastward advection of inputs from land is expected over most of the Santa Barbara Channel.