CAUSES OF HIGH TURBIDITY EVENTS IN SALEM HARBOR, MA, CONSTRAINED BY CONTINUOUS WATER QUALTIY MONITORING

Salem Harbor is a mesotidal coastal embayment located north of Boston, MA. Within the Harbor there are two minor fresh water river inflows, Forest and South River. Qualitative observations of water clarity suggest that high turbidity events have affected the harbor in recent years, however the cause of such events has remained elusive. Increased turbidity has been shown to be a significant stressor on other coastal systems by reducing the photic depth as well as stressing filter feeders and fish. In Salem Harbor, surveys conducted by the MA Department of Environmental Protection have shown declines in eelgrass over past decades, which may be at least partially connected to increased turbidity. In April 2012 a series of five monitoring buoys were deployed in Salem Harbor, with two at the river inflows, two within mooring fields, and one at the mouth of the harbor. Geochemical probes housed within the buoys have logged surface water temperature, salinity and turbidity continuously for the period. A meteorological station that is located within the watershed, as well as sediment trap and filtered particulate matter samples from the water column have provided constraints on the environmental conditions during the course of the logging record. Our results demonstrate that during certain periods of increased turbidity, surface salinity values decrease. This observation suggests that freshwater runoff from the watershed may play a significant role in introducing particulate matter to the harbor. Further data analysis is ongoing and will assist in constraining additional forcing factors.