Water Quality at Elkhorn Slough and its Impacts on Olympia Oysters (Ostrea lurida) and Staghorn Sculpin (Leptocottus Armatus)

Elkhorn Slough is an estuary in central California located in a productive agricultural watershed.  The estuary hosts rich plant and animal communities, but monitoring was revealed that water quality at some sites is very impaired. Water quality sondes reveal strong diurnal fluctuations in water quality parameters, including dissolved oxygen.  However, no previous studies have directly linked these water quality dynamics to biological indicators.  The goal of our study was to correlate water quality to two indicators of estuarine biodiversity, native Olympia oysters (Ostrea lurida) and Pacific Staghorn sculpin (Leptocottus armatus). The fish and sculpins were each collected at one central location at Elkhorn Slough and distributed to seven sites located across the estuary. At each site a multiparameter water quality sonde was continuously deployed to measure: temperature, conductivity, pH, dissolved oxygen, and turbidity.  We tracked survival of the fish and oysters over time, and growth rate of the oysters.  We linked survival and growth of these two indicators to the water quality they experienced, in particular testing the hypothesis that hypoxia events would be linked to fish mortality.  The analysis was used to characterize the habitat value of different wetlands in the estuary for these representative biological indicators. A better understanding of water quality and its impacts on aquatic life will help managers prioritize restoration strategies.