Response of benthic metabolism and nutrient cycling to reductions in wastewater loading to Boston Harbor, USA
Giblin, Anne E.
Hopkinson, Charles S.
Kelsey, Samuel W.
Howes, Brian L.
MetadataShow full item record
KeywordSediment metabolism; Coastal marine sediments; Nutrient reductions; Denitrification; Sewage treatment; Bioirrigation
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.
© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Estuarine, Coastal and Shelf Science 151 (2014): 54-68, doi:10.1016/j.ecss.2014.09.018.
The following license files are associated with this item:
Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivs 3.0 Unported
Showing items related by title, author, creator and subject.
Sulfate reduction and possible aerobic metabolism of the sulfate-reducing bacterium Desulfovibrio oxyclinae in a chemostat coculture with Marinobacter sp. strain MB under exposure to increasing oxygen concentrations Sigalevich, Pavel; Baev, Mark V.; Teske, Andreas; Cohen, Yehuda (American Society for Microbiology, 2000-11)A chemostat coculture of the sulfate-reducing bacterium Desulfovibrio oxyclinae together with a facultative aerobe heterotroph tentatively identified as Marinobacter sp. strain MB was grown under anaerobic conditions and ...
Effects of experimental warming and carbon addition on nitrate reduction and respiration in coastal sediments Brin, Lindsay; Giblin, Anne E.; Rich, Jeremy J. (2015-04)Climate change may have differing effects on microbial processes that control coastal N availability. We conducted a microcosm experiment to explore effects of warming and carbon availability on nitrate reduction pathways ...
Algar, Christopher K.; Vallino, Joseph J. (Inter-Research, 2014-01-23)We present an ecosystem model that describes the biogeochemistry of a sediment nitrate reducing microbial community. In the model, the microbial community is represented as a distributed metabolic network. Biogeochemical ...