Bioturbation effects of the amphipod Corophium volutator on microbial nitrogen transformations in marine sediments |
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Authors: | S P Pelegrí T H Blackburn |
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Institution: | (1) Department of Microbial Ecology, Institute of Biological Sciences, University of Aarhus, Ny Munkegade Bd. 540, DK-8000 Aarhus C, Denmark |
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Abstract: | Microcosms containing different densities of Corophium volutator, ranging from 0 to 6000 ind m-2, were incubated in a flow-through system. Benthic fluxes of CO2, O2, NO3
- and NH4
+ were measured regularly. Thirteen days after setup the microcosms were sacrificed and sediment characteristics, pore water NO3
-, NH4
+ and exchangeable NH4
+ concentrations, and potential nitrification activity were measured. The presence of C. volutator increased overall mineralization processes due to burrow construction and irrigation. The amphipods increased the ratio CO2/O2 fluxes from 0.73 to 0.86 in microcosms inhabited by 0 and 6000 ind m-2, respectively. Burrow ventilation removed NH4
+ from the sediment, which was nitrified in the oxic layer and transported NO3
- to the burrow sediment, where denitrification potential was enhanced. Nitrification and total denitrification rates (denitrification of NO3
- coming from the overlying water and of NO3
- generated within the sediment) were calculated and discussed. Bioturbation by C. volutator increased both nitrification and denitrification, but denitrification was stimulated more than nitrification. Denitrification of NO3
- coming from the overlying water was stimulated 1.2- and 1.7-fold in microcosms containing 3000 and 6000 ind m-2 relative to control microcosms. The presence of C. volutator (6000 ind m-2) stimulated nitrogen removal from the system, as dinitrogen, 1.5-fold relative to non-bioturbated microcosms. C. volutator individuals used in our study were collected from Norsminde Fjord, Denmark, in 1990. |
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