Coastal oceanographic processes influence the growth and size of a key estuarine species, the Olympia oyster

Here we empirically demonstrate that a tidal exchange gradient in a central California estuary leads to inversely related spatial gradients in upwelled nutrients and water residence times. As a result, seasonal phytoplankton blooms (summer-fall) occur in the middle of the bay, where nutrient levels and water residence times are intermediate, while seasonal temperature maximums occur in the inner bay, where water residence times are highest and nutrient levels are lowest. By experimentally out-planting juvenile Olympia oysters (Ostrea lurida) throughout the estuary, we found that the growth and size of juvenile oysters are better explained by the spatial pattern of phytoplankton concentrations than by that of water temperature. Furthermore, this benthic-pelagic link helps explain the distribution of adult oyster sizes throughout the estuary. Because a phytoplankton maximum can be maintained by a physical interaction between intensive upwelling and a seasonal low-inflow estuary, benthic invertebrates within protected embayments of upwelling regions may not conform to the regional generalization that their growth and size are negatively correlated with upwelling intensity.