Dierking, Jan

Karez, Rolf

Reusch, Thorsten B.H.

Schubert, Philipp

English

OceanRep

prevailing currentConclusionSpatial patterns of stable isotope distribution matched our expectations. Hence, stable isotope δ15N ratios of eelgrass leaves seem to be suited as biomarker for anthropogenic nutrient input from wastewater. The next step will be a coastwide screen of 15N from eelgrass to assess the influence of sewage derived nitrogen on coastal ecosystems of the western Baltic Sea. Isotopic signatures of eelgrass (Zostera marina L.) as bioindicator of anthropogenic nutrient inputSchubert PR1, Karez R2, Reusch TBH1, Dierking J11Helmholtz Center for Ocean Research Kiel, 2State Agency for Agriculture, Environment and Rural Areas Schleswig-HolsteinSampling location and designHeiligenhafen Bay lies in the western Baltic Seaand holds an important sewage outfall. Eelgrass shoots were collected every 500 m along a transect parallel to the shore in 3-4 m depth. Additionally, at 7 vertical transects the deepest and shallowest eelgrass found was sampled. Back in the lab plants were cleaned of epiphytes and eelgrass leaves were used for stable isotope analysis.Recent use of stable isotope content of macroalgae as a proxy for human nutrient input suggests that eelgrass Zostera marina could be used as  biomarker for sewage derived nutrients. Eelgrass is continuously distributed along the German coast of the Baltic Sea. The leaves function as a temporal integrator of nutrient input with a leaf turnover time of about 50-60 days.Sewage derived nitrogen often has a distinctive isotopic signature due to the high prevalence of the heavier 15N isotope caused by nitrification and denitrification processes in wastewater treatment plants. This results in high δ15N values (>12‰) of the outflowing water. Our goal here was to map eelgrass δ15N ratios around a major sewage outfall and then compare the findings with our expectations of nutrient distribution.Can we use the δ15N ratio of eelgrass leaves to assess sewage input in coastal ecosystems of the Baltic Sea?1. δ15N values of eelgrass growing downstream of the outfall were significantly higher than upstream2. Nitrogen isotope ratios were back to normal about     4 km downstream of the outfall3. No differences in stable isotope signature between deep and shallow eelgrassResultsContact:Philipp Schubertpschubert@geomar.deFunded by: AcknowlegdementsFor sampling: Hendrik Schulz, Sören Bolte, David Haase, Olivia RothFor weighing: Regina Klapper, Maike RothweilerFor posterizing and everything: Susanne LandisUpstream vs. DownstreamTwo-sample T-Test, T=-3.97, p<0.001, DF=37δδ δδ 11 1155 55 ΝΝ ΝΝdownstreamupstream14121086420Boxplot of d15N a                                                     b        

Isotopic signatures of eelgrass (Zostera marina L.) as bioindicator of anthropogenic nutrient input

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