201. Coastal current effects on primary production rates and implications for ecosystem dynamics in Massachusetts Bay
- Author
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McManus, M. Conor and McManus, M. Conor
- Abstract
Primary production was measured from 1992-2010 in western Massachusetts Bay and Boston Harbor as part of the Massachusetts Water Resource Authority’s outfall monitoring program. In 2003, annual primary production rates decreased by 221-279 g C m-2 year-1 in both systems, with decreased rates continuing through 2010. Oceanographic and meteorological variables were analyzed with production rates to determine if concurrent changes in the environment were responsible for the reduced primary production rates in Massachusetts Bay. Zooplankton abundances and benthic flux rates were compared with production rates as well to determine if the decreased production rates had cascading effects on the ecosystem. Based on a constructed conceptual model, results indicated that larger influxes of low saline water derived from the western Maine Coastal Current (WMCC) from 2003-2010 may have been responsible for the reduced production rates. Increased river discharge (particularly the Merrimack River) and intrusion of Labrador Subarctic Slope Water into the Gulf of Maine appear to have freshened the WMCC in recent years. More northeasterly winds over the last several years were favorable in penetrating WMCC waters into Massachusetts Bay. The correlations between primary production and stratification and surface salinities suggested an impact of the WMCC on production rates. I hypothesized in a conceptual model that increased stratification resulted in decreased vertical mixing and nutrient concentrations in the surface waters for phytoplankton growth, but there were no significant correlations between nutrient availability and stratification in available data. While the Massachusetts Bay primary production rates were influenced by changes in oceanography, rates in Boston Harbor were a result of nutrient removal from the Boston Harbor outfall diffuser relocation. Significant relationships between surface salinity and wind stress and river runoff in the Harbor suggests the system is mor
- Published
- 2012