Stable isotopes reveal that chironomids occupy several trophic levels within West Greenland lakes: Implications for food web studies

Abstract

Stable isotope analyses of nitrogen (d 15 N) and carbon (d 13 C) were conducted on individual chironomid taxa from low arctic lakes to investigate the range in trophic levels covered by this diverse insect group. Five lakes were sampled, including two freshwater, two oligosaline, and one glacier influenced lake, representing the major lake types in southwest Greenland. There was a large difference in the offset of isotopic values among the different lake types. In the oligosaline lakes, we ascribe low d 13 C values to the use of recycled CO 2 , while the high d 15 N signal is possibly controlled by microbial processes. In order to compare among lakes, the d 15 N signal of the chironomid taxa was normalized to common primary consumers (Psectrocladius sordidellus group and Psectrocladius limbatellus groups) that show consistently low d 15 N values and belong to the subfamily Orthocladiinae. Normalized d 15 N values spanned more than 5%, indicating that the chironomid community covered at least two trophic levels in these low arctic lakes. The d 15 N values of different chironomid taxa within a single habitat differed by 1% to 5%. The results suggest that chironomids should not be considered as one group in food web studies. Even interpretation of trophic position on subfamily level can be problematic as a result of the large differences observed in their d 15 N values. The level of detailed trophic information on individual chironomid taxa presented here has not previously been reported. Chironomids are an abundant and important group of organisms in arctic lakes, and the observed variation in their trophic level indicates a high complexity of the food web structure of arctic lakes.

Glacier dynamics influenced carbon flows through lake food webs: evidence from a chironomid δ13C-based reconstruction in the Nepalese Himalayas

“…13 C values of pelagic primary production usually range from -36 to -25% (Vuorio et al, 2006;Wang et al, 2013), the range of d 13 C HC values could match well with that of the d 13 C values of phytoplankton frequently observed in CO 2 -limiting environment (Street-Perrott et al, 1997;Reuss et al, 2013). Lake Pyramid Inferior is located at 5,067 m a.s.l., and atmospheric pressure is consequently about the half of the value reported at the sea level.…”

Chironomidae larvae associated with Eichhornia azurea leaf detritus: decomposition community structure and colonization dynamics

“…Analysis of the Chironomid trophic structure with stable isotopes showed a broad variety of feeding behaviors between taxa, suggesting that Chironomids do not belong to specific groups in the aquatic trophic web (Henriques-Oliveira et al 2003;Reuss et al 2013;Silveira et al 2013;Saito and Fonseca-Gessner 2014). Reuss et al (2013) also found that the stomach contents of Tanypodinae (e.g., Djalmabatista sp., Labrundinia sp. and Larsia sp.)…”

“…(2). Fitting was performed with non-linear regressions using the iterative Levenberg-Marquardt algorithm (Press et al 2007).…”

Ecological determinants of methylmercury bioaccumulation in benthic invertebrates of polar desert lakes

“…Trichoptera larvae had a similar trophic position but lower MMHg concentrations than Chironominae chironomids. These primary consumers may specialize on distinct types of benthic algae or detritus (Grey et al 2004;Ings et al 2010;Reuss et al 2013) that result in differential uptake of MMHg or variation in growth rate could play a role in bioaccumulation (Karimi et al 2007).…”

“…Carbon and nitrogen stable isotopes are powerful ecological tracers that provide information on dietary sources or the trophic position of organisms, respectively (Fry 2006). A recent investigation (using carbon and nitrogen stable isotopes) showed striking interspecies variation in the diet of Arctic chironomids from Greenland lakes (Reuss et al 2013). At lower latitudes, delta values of carbon stable isotopes in larval chironomids are often more negative in offshore, deeper waters relative to the shoreline (Vander Zanden and Rasmussen 1999;Hershey et al 2006;Syväranta et al 2006;Jones et al 2008).…”