Tucker Jane

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Tucker
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  • Preprint
    Western Maine Coastal Current reduces primary production rates, zooplankton abundance and benthic nutrient fluxes in Massachusetts Bay
    ( 2013-08) McManus, M. Conor ; Oviatt, Candace A. ; Giblin, Anne E. ; Tucker, Jane ; Turner, Jefferson T.
    Primary production was measured from 1992-2010 in Massachusetts Bay and just outside Boston Harbor for the Massachusetts Water Resources Authority’s outfall monitoring program. In 2003, annual primary production decreased by 221-278 g C m-2 year-1, with decreased rates continuing through 2010. Based on a conceptual model, oceanographic and meteorological variables were analyzed with production rates to determine if concurrent environmental changes were responsible for the reduced primary production in Massachusetts Bay. Results indicated that stronger influx of low salinity water from the western Maine Coastal Current (WMCC) in recent years might be responsible for the decreases. The WMCC appeared to have become fresher from increased river discharge in the western Gulf of Maine. Northeasterly winds in recent years promoted WMCC intrusion into Massachusetts Bay. Correlation between primary production and surface salinities suggested the impact of the WMCC on production rates. We hypothesized that increased stratification resulted in reduced vertical mixing and nutrient concentrations in surface waters for phytoplankton growth. However, no significant correlations were observed between the annual primary production and nutrient concentrations in Massachusetts Bay. Reduced production rates in Massachusetts Bay have been associated with reduced zooplankton abundances, benthic ammonium fluxes and sediment oxygen demand in summer months.
  • Article
    Response of benthic metabolism and nutrient cycling to reductions in wastewater loading to Boston Harbor, USA
    (Elsevier, 2014-10-02) Tucker, Jane ; Giblin, Anne E. ; Hopkinson, Charles S. ; Kelsey, Samuel W. ; Howes, Brian L.
    We describe the long-term response of benthic metabolism in depositional sediments of Boston Harbor, MA, to large reductions in organic matter and nutrient loading. Although Boston Harbor received very high loadings of nutrients and solids it differs from many eutrophic estuaries in that severe hypoxia was prevented by strong tidal flushing. Our study was conducted for 9 years during which a series of improvements to sewage treatment were implemented, followed by 10 years after the culminating step in the clean-up, which was to divert all wastewater effluent offshore. Counter to expectations, sediment oxygen demand and nutrient effluxes initially increased at some stations, reaching some of the highest rates recorded in the literature, and were spatially and temporally quite variable. Early increases were attributed to macrofaunal effects, as sediments at some sites were rapidly colonized by tube-building amphipods, Ampelisca spp., which dominated a dense macrofaunal mat community. As reductions in loading progressed, however, mean rates in oxygen uptake and release of ammonium, nitrate, and phosphate all decreased. At the point of outfall diversion, rates and variability had already decreased substantially. By the end of the study, average oxygen uptake had decreased from 74 to 41 mmol m−2 d−1 and spatial and temporal variability had decreased. Similarly, nutrient fluxes were less than half the rates measured at the start of the project and also less variable. Other evidence of improved conditions included a decrease in the carbon content of sediments at most stations and higher Eh values at all stations, illustrating less reducing conditions. Denitrification also showed an overall decrease from the beginning to the end of the 19-year study, but was highest during the intermediate phases of the cleanup, reaching 9 mmol N m−2 d−1. At the end of the study denitrification averaged for all sites was 2.2 mmol N m−2 d−1, but when compared to current loadings, had become a more important overall sink for N within the harbor. Few long-term examinations of the responses of sediment biogeochemistry to reductions in nutrient and organic matter loading have been reported. Our findings demonstrate that benthic fluxes may respond to reductions in loading in complex ways, and sediments need not represent a long-term legacy that would impede ecosystems recovery.