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Stable isotope analysis provides fresh insights into dietary separation between Chironomus anthracinus and C. plumosus

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<mark>Journal publication date</mark>2004
<mark>Journal</mark>Journal of the North American Benthological Society
Issue number2
Volume23
Number of pages10
Pages (from-to)287-296
Publication StatusPublished
<mark>Original language</mark>English

Abstract

We used stable isotope analysis to investigate dietary differences between 2 sympatric species of tubicolous chironomid larvae, Chironomus plumosus and C. anthracinus, from the profundal sediments of 6 eutrophic lakes in the UK and Germany. We found striking variation between lakes in both δ13C (−29.8 to −56.3‰) and δ15N (−7.8 to 14.7‰) in the 2 chironomid species. Moreover, C. plumosus was consistently depleted in both 13C and 15N relative to C. anthracinus. Our data support previous reports of interspecific dietary variations between the 2 species, which suggest niche separation partly on the basis of diet. However, reported differences in the feeding modes of the 2 species could not explain the extreme 13C- and 15N-depletion observed in chironomid larvae from several of the lakes. We suggest that the low δ13C signatures result from the ingestion of methanotrophic bacteria and subsequent incorporation of biogenic methane-derived C. Further, the chironomid larvae enhance methanotrophic activity via bioturbation of the surrounding sediment. Significant isotope differences between the 2 species may result from their variable tube morphologies or physiology.