History of anthropogenic nitrogen input to the German Bight/SE North Sea as reflected by nitrogen isotopes in surface sediments, sediment cores and hindcast models

The German Bight/SE North Sea is considered a hot-spot of river-induced eutrophication, but the scarce observational data of river nitrate loads prior to the 1970s complicate the assessment of target conditions for environmental management and legislation. Stable nitrogen isotope ratios (δ 15N) in s...

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Published in:Continental shelf research 2010-09, Vol.30 (15), p.1626-1638
Main Authors: Serna, Alexandra, Pätsch, Johannes, Dähnke, Kirstin, Wiesner, Martin G., Christian Hass, H., Zeiler, Manfred, Hebbeln, Dierk, Emeis, Kay-Christian
Format: Article
Language:English
Subjects:
Abundance
Eutrophication
Freshwater
German Bight
Mouth
Nitrates
nitrogen
Nitrogen isotopes
North Sea
Rivers
Sediments
Spatial distribution
Stable isotopes
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Summary:The German Bight/SE North Sea is considered a hot-spot of river-induced eutrophication, but the scarce observational data of river nitrate loads prior to the 1970s complicate the assessment of target conditions for environmental management and legislation. Stable nitrogen isotope ratios (δ 15N) in sediment records can be used to decipher historical river nitrate contributions. To better constrain pre-1970s conditions, we determined δ 15N in archive sediment samples (1950–1969) and dated cores from the Helgoland depositional area. We also modeled the δ 15N in past situations (1960 and 1860) using an N-isotope-tracking ecosystem model. The modeled spatial distribution of δ 15N in sediments for 1960 conditions and the observed spatial pattern of δ 15N in archive sediment samples (1950–1969) represent a period of moderate eutrophication. The modeled spatial distribution of δ 15N in sediments for 1860 conditions (pre-industrial) showed a moderate δ 15N gradient from the Elbe river mouth (δ 15N9‰) to the open sea (δ 15N
ISSN:0278-4343
1873-6955
DOI:10.1016/j.csr.2010.06.010