Sub-fossil Chironomidae as indicators of palaeoflow regimes: integration into the PalaeoLIFE flow index

The sub-fossil head capsules of larval Chironomidae have been widely exploited as palaeoecological indicators of lentic ecosystems but their value in the interpretation of the evolution of lotic systems has been underutilised by comparison. Recent research has demonstrated that the remains of Chironomidae are abundant within fluvial sequences and that they offer a valuable record of channel change and floodplain evolution that may complement that derived from existing biological and sedimentological techniques. This paper demonstrates the use of Chironomidae in characterising the palaeoflow regime of a large mid–late Holocene floodplain palaeochannel (5470–4960 to 1530– 1350 cal. a BP) of the River Trent (Derbyshire, UK). Using expert knowledge and published information regarding flow preferences, larval Chironomidae were incorporated into the PalaeoLIFE (Loticinvertebrate Index for Flow Evaluation) methodology. The results clearly demonstrate that the subfossil record provided by Chironomidae can be used to characterise changes in the flow regime within palaeochannel sections. At the scale of the channel section, species- and generic-level ecological associations can provide useful information regarding habitat characteristics, including the presence of instream vegetation, mineral substrates and woody debris. The ability to undertake environmental reconstruction and channel evolution history was significantly enhanced through the application of a multi-proxy approach, by incorporating other aquatic insect groups (Trichoptera and Coleoptera) into the PalaeoLIFE metric, together with sedimentological data.