TY - JOUR

T1 - Linking larval chironomids to methane

T2 - seasonal variation of the microbial methane cycle and chironomid δ13C

AU - Deines, Peter

AU - Grey, Jonathan

AU - Richnow, Hans-Hermann

AU - Eller, Gundula

PY - 2007

Y1 - 2007

N2 - Methane-derived carbon has been shown to be an important carbon source for macroinvertebrates in several studies of lake ecosystems using stable isotopes. Furthermore, season and lake morphology appear to influence the importance of methane as a carbon source. However, rarely have the dynamics of the methane cycle been measured concurrently with the isotope signatures of chironomid larvae. We examined the methane dynamics in 2 lakes with contrasting mixing regimes (polymictic and dimictic), while monitoring corresponding changes in chironomid larval δ13C throughout an annual cycle. Both methane turnover rates and abundance of methane-oxidising bacteria were higher in the dimictic lake, where correspondingly lower mean larval δ13C values of –44.2 to –61.7‰ were recorded. In contrast, potential methane production and oxidation rates, as well as cell numbers of methane-oxidising bacteria were always lower in the polymictic lake; corresponding larval δ13C values ranged from –32.3 to –29.6‰. Furthermore, seasonal variation in larval δ13C was more pronounced in the dimictic lake (–50.1 ± 5.9‰) compared to the polymictic lake (–31.1 ± 1.2‰), reflecting the amplitude of turnover rates. This suggests strongly that lake characteristics have an influence on methane turnover rates and, in conjunction with season, affect the subsequent incorporation of methane-derived carbon into freshwater food webs via macroinvertebrates.

AB - Methane-derived carbon has been shown to be an important carbon source for macroinvertebrates in several studies of lake ecosystems using stable isotopes. Furthermore, season and lake morphology appear to influence the importance of methane as a carbon source. However, rarely have the dynamics of the methane cycle been measured concurrently with the isotope signatures of chironomid larvae. We examined the methane dynamics in 2 lakes with contrasting mixing regimes (polymictic and dimictic), while monitoring corresponding changes in chironomid larval δ13C throughout an annual cycle. Both methane turnover rates and abundance of methane-oxidising bacteria were higher in the dimictic lake, where correspondingly lower mean larval δ13C values of –44.2 to –61.7‰ were recorded. In contrast, potential methane production and oxidation rates, as well as cell numbers of methane-oxidising bacteria were always lower in the polymictic lake; corresponding larval δ13C values ranged from –32.3 to –29.6‰. Furthermore, seasonal variation in larval δ13C was more pronounced in the dimictic lake (–50.1 ± 5.9‰) compared to the polymictic lake (–31.1 ± 1.2‰), reflecting the amplitude of turnover rates. This suggests strongly that lake characteristics have an influence on methane turnover rates and, in conjunction with season, affect the subsequent incorporation of methane-derived carbon into freshwater food webs via macroinvertebrates.

KW - Methane cycle

KW - Stable isotopes

KW - Chironomid larvae

KW - Seasonality

U2 - 10.3354/ame046273

DO - 10.3354/ame046273

M3 - Journal article

VL - 46

SP - 273

EP - 282

JO - Aquatic Microbial Ecology

JF - Aquatic Microbial Ecology

SN - 0948-3055

ER -