Spatial scales of benthic and pelagic producer biomass in a coastal upwelling ecosystem

We studied the spatial structure of benthic and pelagic primary producer biomass over a large region on the west coast of North America, between Baja California del Sur, Mexico (27° N), and Oregon, USA (42° N). The distribution of benthic primary producer biomass was determined from repeated aerial surveys of shallow subtidal kelp stands, and pelagic primary producer biomass, from the long-term average of nearshore chlorophyll a concentrations from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). Spatial analyses showed a striking match between the patch scales of kelp stands and chlorophyll a concentrations, with a characteristic length scale of ∼180 km. Cross-correlation analysis revealed that kelp and phytoplankton biomass were negatively correlated from 0 to 150 km lag distances in the equatorward direction and 0 to 30 km in the poleward direction. Positive correlations at distances longer than the patch scale detected in the spatial analysis indicated that patches of benthic and pelagic biomass were offset in space. A spatial analysis of coastline features and long-term average coastal sea surface temperature anomalies from AVHRR (Advanced Very High Resolution Radiometer) suggested that the spatial structure of benthic and pelagic primary producer biomass was associated with topographic forcing of coastal upwelling. Our results suggest that shoreline geomorphology has strong effects on coastal ecosystems, by altering the spatial distribution of primary producer biomass over characteristic spatial scales.