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WIDESPREAD CONTRIBUTION OF METHANE‐CYCLE BACTERIA TO THE DIETS OF LAKE PROFUNDAL CHIRONOMID LARVAE
Author(s) -
Jones Roger I.,
Carter Clare E.,
Kelly Andrew,
Ward Susan,
Kelly David J.,
Grey Jonathan
Publication year - 2008
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/06-2010.1
Subject(s) - profundal zone , hypolimnion , eutrophication , ecology , chironomidae , chironomus , δ13c , larva , biology , isotopes of carbon , environmental science , environmental chemistry , total organic carbon , stable isotope ratio , nutrient , chemistry , physics , quantum mechanics , littoral zone
Reports of unexpectedly 13 C‐depleted chironomid larvae in lakes have led to an hypothesis that significant transfer of detrital organic matter to chironomid larvae may occur via methane‐cycle bacteria. However, to date little is known of how such transfer might vary across species and lakes. We gathered data from 87 lakes to determine how widespread this phenomenon might be and to define boundaries for its likely magnitude. Carbon stable isotope values of chironomid larvae varied greatly between taxa. Very marked 13 C‐depletion was evident only in certain taxa, especially Chironomus plumosus , C. anthracinus , and C. tenuistylus , all characteristic of eutrophic or dystrophic lakes and known to be tolerant of low oxygen conditions. Furthermore, marked 13 C‐depletion was only found in larvae from lakes in which late‐summer hypolimnetic oxygen depletion near the sediment surface was below an apparent threshold concentration of 2–4 mg O 2 /L. Similarly, application of a two‐source mixing model suggested that methanotrophic bacteria made the greatest contribution to profundal chironomid growth (0–70% of larval carbon) when the late‐summer oxygen concentration dropped below ∼ 2 mg O 2 /L. Our study demonstrates that methane‐derived carbon is an important, but often neglected, contribution to the flux of carbon through the food webs of many productive or dystrophic lakes.

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