. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 240 REPORTS FROM THE MBL GENERAL SCIENTIFIC MEETINGS Reference: Biol. Bull. 195: 240-241. (October, 1998) Dissolved Inorganic Nitrogen Flux and Mineralization in Waquoit Bay Sediments as Measured by Core Incubations John Kirk/nit rick and Ken Foreman (Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts, 02543), and Ivan Valiela2 Globally, human activities have doubled the rate at which atmospheric dinitrogen is fixed into bioavailable forms such as ammonium and nitrate (1). Locally, this increase in N
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 240 REPORTS FROM THE MBL GENERAL SCIENTIFIC MEETINGS Reference: Biol. Bull. 195: 240-241. (October, 1998) Dissolved Inorganic Nitrogen Flux and Mineralization in Waquoit Bay Sediments as Measured by Core Incubations John Kirk/nit rick and Ken Foreman (Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts, 02543), and Ivan Valiela2 Globally, human activities have doubled the rate at which atmospheric dinitrogen is fixed into bioavailable forms such as ammonium and nitrate (1). Locally, this increase in N fixation is manifested as greater nitrogen loading to coastal ecosystems, systems in which nitrogen is often the principal limiting nutrient for primary producers (2). In these systems, mineralization is the primary process by which organic nitrogen deposited to sediments is regenerated. This mineralized N can flux out of the sediments or be denitrified (3). N that fluxes out of the sediments and enters the water column can be taken up by producers. As a result, N may be recycled several times before being transported out of the ecosystem. One important control on the proportion of N input that is recycled within an ecosystem is the rate of denitrification. Here we report on N cycling in sediments at two sites in Waquoit Bay, the Childs River estuary, which receives high inputs of N ( kg N ha"' y~'), and Sage Lot Pond, which receives much lower N inputs ( kg N ha"' y~') due to its relatively pristine watershed (unpubl. data). To assess the effects of nitrogen loading on these processes, we measured rates of mineralization and dissolved inorganic nitrogen (DIN) flux from the sediment in two cores collected from each site. We were also able to estimate the maximum rate of denitrification. which can be calculated as the difference between mineralization and flux (4). We measured N flux as the change in concentration of NH4 and NO3 over 24 hours in the water-fille
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
