Coastal oceanography and resource gradients for oyster reefs in CA
Upwelling along coastlines has the dual effect on increasing nutrients and phytoplankton production, while also decreasing temperature and advecting phytoplankton offshore. For filter-feeding invertebrates along open coastlines (such as oysters), the advection of food and low temperatures associated with high upwelling are thought to lower growth and metabolic rates. I worked with Dr. Lariger and Dr. Grosholz in California to test the effects of upwelling on Olympia oyster growth in a tidal estuary (Tomales Bay), to see if this generalization applies in estuarine environments. We demonstrated that a gradient in tidal-exchange along the length of this estuary interacts with intense upwelling to create inversely related spatial gradients. Water at the mouth of the bay had the lowest residence time and lowest temperature, but the highest concentration of upwelled nutrients. Water at the head of the bay had the highest residence time and highest temperature, but the lowest concentration of upwelled nutrients. As a result, seasonal phytoplankton blooms tended to occur in the middle of the bay, where conditions were optimal for their growth and retention. Furthermore, we found that the growth and size of oysters was highest in the middle of the bay - the location of the phytoplankton maximum. Because of the physical processes occuring within low-inflow estuaries, high phytoplankton levels (and high bivalve growth) may be obtained even under intense upwelling conditions.
Kimbro, D. L., J. Largier, and E. D. Grosholz. 2009. Coastal oceanographic processes influence the growth and size of a key estuarine species, the Olympia oyster. Limnology and Oceanography 54(5): 1425-1437. PDF