25th International Meeting on Organic Geochemistry IMOG 2011

P-416
Developing analytical protocols for the measurement of 13C and
15N of crucial organisms within the food web of the Dutch
Wadden Sea
Elisabeth Svensson 1 , Tjisse van der Heide 2 , Sander Holthuijsen 1 , Stefan Schouten 1 ,
Henk W. van der Veer 1 , Jack J. Middelburg 3 , Jaap Sinninghe Damste 1
1 NIOZ Royal Netherlands Institute for Sea Research, 't Horntje, Netherlands, 2 University of Groningen,
Groningen, Netherlands, 3 Utrecht University, Utrecht, Netherlands (corresponding
author:elisabeth.svensson@nioz.nl)
Over the last decade, stable isotopes of carbon and
nitrogen have become widely used tools in ecological
studies. The source of organic carbon can be traced
using the ratio of 13 C to 12 C, (� 13 C), while trophic
levels can be distinguished using the ratio of 15 N to
14 N (� 15 N) (e.g. Fry, 1999). Although the analytical
techniques are the same for both biological and
abiotic samples, the wide range of sample matrixes of
different organisms and sediments requires that
different sample preparation procedures are required
for each sample type (e.g. Logan et al., 2008;
Schielke and Post, 2010; Smyntek et al., 2007). In
addition care needs to be taken during sample
preparation to minimize loss of carbon and nitrogen,
e.g. due to acidic treatment for removal of inorganic
carbon, as that will most likely have an effect on the
stable isotope data (e.g. Brodie et al., in press).
The Wadden Sea is the world‘s largest soft-bottom
intertidal ecosystem as it stretches from the
Netherlands to Denmark. It hosts unique species and
also serves as a fueling station for migratory birds and
in 2009 UNESCO named the Dutch-German Wadden
Sea as a World Heritage site because of its
―outstanding universal value‖. Due to the ecological
importance of the Wadden Sea, understanding the
structure of the food web of the Wadden Sea is
essential and also to determine if the source of the
organic carbon that makes up the base of that food
web is produced within the sea itself or transported
there from external sources such as the North Sea or
land.
To this end we are determining the bulk isotopic
carbon and nitrogen composition of a variety of
organisms from a large number of stations along a
grid over the Dutch Wadden Sea. Samples were
taken for sedimentary organic matter, phyto- and
zooplankton, sea weeds, worms, fish and shellfish.
We have elaborated a sample preparation scheme
that simplifies, while ensuring analytical accuracy, the
analysis of a large and diverse number of biological
and sediment samples from that area. Initial results
show that acidification within a tin cup can result in
small but significant shifts in 13 C as well as sometimes
15 N for tissue or biomass of a number of organisms.
References
Brodie, C.R. et al., in press. Evidence for bias in C
and N concentrations and δ 13 C composition of
terrestrial and aquatic organic materials due to
pre-analysis acid preparation methods. Chemical
Geology.
Fry, B., 1999. Using stable isotopes to monitor
watershed influences on aquatic trophodynamics.
Canadian Journal of Fisheries and Aquatic
Sciences, 56(11): 2167-2171.
Logan, J.M. et al., 2008. Lipid corrections in carbon
and nitrogen stable isotope analyses: comparison
of chemical extraction and modelling methods.
Journal of Animal Ecology, 77(4): 838-846.
Schielke, E.G. and Post, D.M., 2010. Size matters:
comparing stable isotope ratios of tissue plugs
and whole organisms. Limnology and
Oceanography: Methods, 8: 348-351.
Smyntek, P.M., Teece, M.A., Schulz, K.L. and
Thackeray, S.J., 2007. A standard protocol for
stable isotope analysis of zooplankton in aquatic
food web research using mass balance correction
models. Limnology and Oceanography, 52(5):
2135-2146.
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