Assessing chironomid head capsule concentrations in sediment using exotic markers |
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Authors: | Gaute Velle Isabelle Larocque |
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Institution: | (1) Bergen Museum, University of Bergen, Muséplass 3, 5007 Bergen, Norway;(2) Department of Biology, University of Bergen, Allegaten 41, Bergen, 5007, Norway;(3) Centre d’études nordiques, Université Laval, Quebec, Canada, G1K 7P4;(4) Institut National de Recherche Scientifique (INRS), Centre Eau, Terre et Environment (ETE), Québec, 490 De La Couronne, Canada, G1K 9A9;(5) NCCR Climate, Erlachstrasse 9A, Bern, 3012, Switzerland |
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Abstract: | All the chironomid head capsules in a sediment sample are normally extracted to determine the concentration of chironomids.
This method may be tedious since a sample may contain hundreds of head capsules. We have tested a method to estimate the concentration
of chironomids in sub-samples and assessed the potential taxonomic bias generated when only a part of each sediment sample
is sorted. To allow calculation of concentrations, a known quantity of exotic markers (microspheres with diameter 149–350 μm)
was added to the sample. The number of head capsules in the total sample was estimated according to the ratio between the
retrieved numbers of microspheres to head capsules in the sub-sample. According to our results, the chironomid concentrations
estimated from sub-samples were statistically similar to the concentrations obtained by processing the full sample. Also,
a sub-sample containing at least 75 head capsules was likely to have similar taxa abundances and taxa richness as the full
sediment sample. These results indicate that exotic markers may be added to chironomid samples for representative concentration
estimation. The method may potentially be used for other biological groups than chironomids. |
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Keywords: | Absolute abundance Chironomids Microspheres Paleolimnology Sediments Sub-sampling |
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