Comprehensive monitoring of long-term changes in chironomid communities as a reflection of the dynamics of heavy metal pollution in the Kaliningrad region

Abstract

Chironomids (Chironomidae) are valuable bioindicators of anthropogenic impact on freshwater ecosystems due to their high sensitivity to pollution, especially heavy metals. The present study documents the results of 10 years of monitoring of chironomid communities in 14 water bodies of the Kaliningrad region, characterized by varying degrees of anthropogenic stress. An integrated approach, including hydrochemical analysis, quantitative assessment of the community structure, and morphological analysis of deformations of the larval oral apparatus, revealed specific patterns of changes in species composition and abundance depending on the concentration and combination of heavy metals. A significant correlation (r=0.78, p<0.001) has been established between the accumulation of cadmium in sediments and the frequency of mental deformities in Chironomus plumosus. The analysis of long-term dynamics demonstrated a progressive decrease in the Shannon-Wiener species diversity index (by 32.4% during the study period) in reservoirs with increased concentrations of lead and zinc. For the first time, a detailed map of the distribution of metal-resistant species has been compiled for the region, highlighting four functional zones of different environmental vulnerability. The results of the study substantiate the need to integrate chironomide-based bioindication into the environmental rationing and monitoring system, as well as provide a fundamental basis for the development of new biotesting methods specific to the aquatic ecosystems of the Baltic region.