Chironomid assemblages from seabird-affected High Arctic ponds |
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Authors: | Neal Michelutti Mark L Mallory Jules M Blais Marianne S V Douglas John P Smol |
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Institution: | (1) Paleoecological Environmental Assessment and Research Laboratory (PEARL), Department of Biology, Queen’s University, Kingston, ON, K7L 3N6, Canada;(2) Environment Canada, Iqaluit, NU, Canada;(3) Program for Chemical and Environmental Toxicology, Department of Biology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada;(4) Canadian Circumpolar Institute, University of Alberta, Edmonton, AB, T6G 2E3, Canada |
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Abstract: | Seabirds can shunt nutrients and contaminants from marine to terrestrial ecosystems by forming dense breeding colonies and
releasing wastes to these sites. A large colony of seabirds at Cape Vera (Devon Island, High Arctic Canada) has resulted in
eutrophic conditions and potentially toxic concentrations of sedimentary metals in several freshwater ponds that drain their
nesting sites. Here, we investigated the effects of elevated nutrient and sedimentary metal concentrations on the distribution
of subfossil chironomids in surface sediments from 21 ponds that span a gradient of seabird influence. Although many ponds
registered high nutrient concentrations (e.g., mean TP = 45 μg l −1), eutrophic taxa typical of temperate waters were not common, with most assemblages being dominated by morphotypes of Psectrocladius and Tanytarsina, as well as Corynoneura arctica-type, and Metriocnemus hygropetricus-type. Although the ponds within and outside the area influenced by seabirds contained largely similar taxa, variations did
exist in the relative abundances of the different species. Lakewater pH was the only measured environmental variable that
explained statistically significant amounts of variation in the chironomid assemblages. Although direct effects of pH on chironomids
cannot be ruled out, pH is likely tracking production-related changes driven by limnetic dissolved inorganic carbon dynamics.
Sediment cores collected from seabird-affected and seabird-free ponds showed a greater number of chironomid taxa and higher
head capsule abundances in the pond receiving seabird inputs. Chironomid assemblages in both cores recorded increased abundances
in recent decades, likely in response to warmer conditions and lengthened growing seasons. |
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