The use of benthic macroinvertebrate metrics in the assessment of ecological status of floodplain lakes

Abstract

Five oxbow lakes of the Łyna River, located in an agricultural area, were studied seasonally in 2005 and 2008. The EPT index (abundance of Ephemeroptera, Plecoptera and Trichoptera larvae), as well as their proportion to Chironomidae indicated that groups sensitive to environmental conditions occurred at low abundance in relation to the different hydrological types of oxbow lakes. The Family Biotic Index, the Biological Monitoring Working Part index adapted to Polish conditions and the Average Score Per Taxon (ASPT) revealed low water quality regardless of the level of hydrological connectivity. In turn, the indices of biodiversity Margalef (d) and probability of interspecific encounters indicated good or satisfactory water quality. The pH correlated positively with the total abundance of aquatic invertebrates, while lower macroinvertebrate abundance was observed in turbid waters of lentic oxbows with a high content of total dissolved solids. Canonical correspondence analysis showed that hydrological connectivity was the main factor responsible for the value of monitoring indices, followed by the physical and chemical parameters of the local environment. Among the indices used, it was ASPT-PL that grouped the studied oxbow lakes according to their hydrological types and seems to be the best index. This study shows that the structure of invertebrate communities inhabiting oxbow lakes reflects physico-chemical conditions of water and can be a valuable source of monitoring data, indispensable to the management and protection of these important aquatic ecosystems.