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Gitte Jacobsen

Release of metals from anoxic sediment

Publikation: KonferencebidragPosterForskning

The Bornholm Deep is anoxic every summer, and samples were collected in the fall 2012 and stored dark and cold (4°C in climate room), degassing regularly with Ar(g) to keep the overlying water column anoxic. Nine sediments columns were selected and divided into three groups, (1) where the water was kept anoxic, (2) where the water column was re-oxygenated and (3) was re-oxygenated and one Harris mud crabs (Rhithropanopeus harrisii (Gould, 1841)) was added to the sediment. The overlying water was exchanged with water from the site where the Harris mudcrabs were caught immediately before the experiment started, with the water for the first group de-gassed by Ar(g) bubbling. Due to inactivity of the crabs in the first week, the temperature was raised from 4°C to 10°C on day 5 to 6, and kept at 10°C during the last week of the experiment.

Analysis of the crab body softparts indicated, that Al, Cr, and V increased in the three crabs exposed to sediment, compared to 6 non-exposed crabs collected at the same time, whereas Cd decreased (T-test, 0.05 level). Test of the meat in the crab claws also indicated increasing Al and V, but not Cr and Cd.

The overlying water was analysed from just above the sediment surface and the top of the water column on day 1, 4, 8 and 12, and the results for V, Mn, Co, Ni, Cu, Zn, Cd, Pb and Fe will be presented, together with indication of statistically significant increase in concentration between the different groups of treatment. The water was clear over both groups without crabs, but cloudy, indicating
re-suspension in the group with crabs.

The metal release from sediments will be discussed in the context of re-oxygenation of anoxic or low-oxic sediments and the effect of organism that digs into the sediment in recently re-oxidised bottom waters.
StatusUdgivet - 2015
Begivenhed18. Danske Havforskermøde - GEUS, Copenhagen, Danmark
Varighed: 28 jan. 201530 jan. 2015


Konference18. Danske Havforskermøde

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