Aquatic Sciences Meeting, Albuquerque 2001

PC09 River and Margin Biogeochemistry

Date: Wednesday, February 14, 2001

Location: Southwest Hall

Ren , L, , Ocean University of Qingdao, Qingdao, China, fg9z001@public.uni-hamburg.de

Raabe, T, , University of Hamburg, Hamburg, Germany, fg4a115@nw01.rrz.uni-hamburg.de

Schuett, M, , University of Hamburg, Hamburg, Germany, mon@uni-hamburg.de

Zhang, M, , Ocean University of Qingdao, Qingdao, China, mpzhang@public.qd.sd.cn

Brockmann, U, H, University of Hamburg, Hamburg, Germany, brockmann@uni-hamburg.de

TURNOVER OF NITROGEN IN ENCLOSED COASTAL ECOSYSTEMS DURING SPRING AND SUMMER IN THE GERMAN BIGHT, NORTH SEA

The coastal water of the German Bight is characterized by the nitrogen rich discharge of the Elbe river. Three series of enclosure experiments have been conducted with coastal water including the natural plankton assemblages in the German Bight during spring and summer 1999. In spring, phosphate was added after its depletion. In summer, all nutrients were exhausted within 2 to 3 days. Nitrate, phosphate and silicate were then added daily. Overall, uptake of inorganic nitrogen by phytoplankton showed following features: (1) ammonium was firstly taken up, inhibiting at concentration >1 µM to nitrate uptake, (2) uptake of nitrate as the main N-source was light dependent, (3) nitrite was observed to be released during nitrate uptake, (4) when nitrate dropped to 6~7 µM, nitrite was taken up as well and decreased to 0.05 µM, (5) in tanks with daily nutrients addition, nitrite was also released at high nitrate uptakel and subsequently utilized, (6) in all experiments, dissolved organic nitrogen (DON) varied between 20~25 µM with short-term fluctuations indicating a steady-state between utilization and regeneration processes. These features were reproduced by a zero-dimensional process model considering intracellular nitrogen pool. Nitrogen transfer, turnover and fluxes within different phases were accordingly quantified and discussed.

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Aquatic Sciences Meeting, Albuquerque 2001

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