Comparing nitrogen isotopic signals between bulk sediments and invertebrate remains in High Arctic seabird-influenced ponds |
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| Authors: | Katherine Griffiths Neal Michelutti Jules M Blais Lynda E Kimpe John P Smol |
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| Institution: | (1) Paleoecological Assessment and Research Laboratory (PEARL), Department of Biology, Queen’s University, Kingston, ON, K7L 3N6, Canada;(2) Program for Chemical and Environmental Toxicology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada; |
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| Abstract: | The mass transport of nutrients by migratory animals can markedly alter the biogeochemistry and ecology of recipient ecosystems,
particularly in nutrient-poor regions such as the Arctic. However, the role of biovectors in the global cycling of nutrients
is often overlooked. Here we investigate nitrogen dynamics in two seabird-affected ponds in the Canadian High Arctic. The
ponds lie at the base of a large seabird colony and have been greatly enriched in nutrients due to the input of guano and
other wastes. Using sediment cores that span the last ~200 years, we measured stable isotopes of nitrogen (δ15N) in bulk sediments as well from the subfossil remains of chironomid (Diptera) head capsules and Daphnia ephippia. The bulk-sediment samples from our seabird-affected ponds had elevated δ15N values relative to seabird-free sites elsewhere in the Arctic. In general, the chironomid δ15N profiles roughly paralleled those of bulk sediments in both study ponds, while the Daphnia profile remained relatively stable in contrast to the considerable variation recorded in the bulk sediments and chironomids.
Interestingly, no apparent pattern emerged among δ15N values recorded in the bulk sediments, chironomids, and Daphnia between the two study ponds. The stability recorded in the δ15N profiles from bulk sediments relative to the more variable invertebrate profiles point towards the complexity of nitrogen
uptake by chironomids and Daphnia at these sites. These data suggest that the bulk sediments are integrating the different fractions of the overall δ15N pool and thus may be most appropriate for reconstructing overall trends in lake trophic status. |
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