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Recolonisation by Macrobenthos Mobilises Organic Phosphorus from Reoxidised Baltic Sea Sediments |
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| Authors: | Nils Ekeroth Magnus Lindstr?m Sven Blomqvist Per O J Hall |
| Institution: | 1. Department of Systems Ecology, Stockholm University, 106 91, Stockholm, Sweden 2. Tv?rminne Zoological Station, University of Helsinki, J.A. Palm??ns v?g 260, 109 00, Hang?, Finland 3. Department of Chemistry and Molecular Biology, Marine Chemistry, University of Gothenburg, 412 96, Gothenburg, Sweden |
| Abstract: | In recent decades, eutrophication has increased the extent of hypoxic and anoxic conditions in many coastal marine environments. In such conditions, the nutrient flux across the sediment?Cwater interface is a key process controlling the biogeochemical dynamics, and thereby the level and character of biological production. In some areas, management attempts to drive the ecosystem towards phosphorus (P) limitation, which calls for reliable knowledge on the mechanisms controlling P-cycling. We report a well-controlled laboratory experiment on benthic fluxes of P, when shifting from a state of hypoxic and azoic sediments to oxic and zoic bottom conditions. Adding any of three types of macrobenthic fauna (mysid shrimp, pontoporeid amphipod and tellinid clam) to oxygenated aquarium sections resulted in benthic P fluxes that differed consistently from the azoic control sections. All species caused liberation of dissolved organically bound P (DOP) from the sediment, in contrast to the azoic systems. The shrimp and the amphipod also resuspended the sediment, which resulted in a release of P bound to particles (>0.45???m). Dissolved inorganic phosphate (DIP) was released during hypoxic conditions, but was taken up after oxygenation, irrespective of the presence or absence of bottom fauna. In the presence of fauna, the uptake of DIP roughly equalled the release of DOP, suggesting that the benthic efflux of DOP following oxygenation and bottom fauna (re)colonisation might be considerable. This is an hitherto overlooked animal-controlled nutrient flux, which is missing from coastal marine P budgets. |
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