Stable oxygen isotopes in chironomid and cladoceran remains as indicators for lake‐water δ 18 O

An understanding of modern relationships between the stable oxygen isotope composition ( δ 18 O) of lake water and aquatic invertebrates is essential for the interpretation of paleoclimate records based on δ 18 O of organic remains of these organisms. We analyzed δ 18 O of lake water and invertebrate remains, including head capsules of chironomid larvae and resting eggs (ephippia) of planktonic Cladocera, in surface sediments from 31 large, deep, and stratified lakes along a latitudinal transect through Europe. The δ 18 O values measured for both lake water and aquatic invertebrate remains were compared to estimated δ 18 O in precipitation. A strong linear relationship between mean annual air temperature and δ 18 O of precipitation was observed along the north–south transect ( r = 0.97), whereas the relationship between precipitation δ 18 O and lake‐water δ 18 O was weaker ( r = 0.80). A strong positive correlation was observed between δ 18 O in lake water and aquatic invertebrates ( r = 0.95 and 0.94 for chironomids and cladocerans, respectively). Although slopes of linear regressions between lake‐water δ 18 O and δ 18 O of both aquatic invertebrate groups are similar, a systematic offset between the absolute δ 18 O values of chironomids and cladocerans was observed; chironomids were on average 2.4‰ heavier than Cladocera. We attribute this offset to differences in ecology, metabolism, and/or behavior between benthic chironomid larvae and planktonic Cladocera. δ 18 O records based on subfossil chironomid and cladoceran remains have the potential to quantitatively characterize past lake‐water δ 18 O and, indirectly, past climatic changes.