Environmental Characterization of Two Ecologically Distinct Gangetic Oxbow Lakes using Zooplankton Taxonomic Indices Through Comparative Approach for Wetland Monitoring

Abstract

The present investigation is an attempt for environmental characterization of two ecologically distinct oxbow lakes using zooplankton taxonomic indices following a comparative approach. These closed and seasonally open oxbow lakes are subjected to eutrophication, impacting their nutrient concentration and eco-hydrological characteristics. The zooplankton are closely linked with environment throughout their life cycle, hence are a potential indicator of eutrophication. The study examined the assemblage pattern of zooplankton community and trophic state of two ecologically distinct oxbow lakes based on eco-hydrological factors and community structure of rotifers and planktonic crustaceans. Comprehensive trophic state index (mTSI), rotifer trophic state indices (mTSIROT) and crustacean based indices (TSICR) were used to assess the degree of eutrophication. The Kruskal–Wallis test confirmed the heterogeneity in eco-hydrological factors between the oxbow lakes. The studied lakes were in transition from high meso-eutrophic to moderately eutrophic state. The mTSI, mTSIROT and mTSICR for Khalsi (seasonally open) and Akaipur (closed) were 54.90 ± 11.71, 56.95 ± 15.64, 59.55 ± 4.54 and 60.26 ± 4.48, 55.79 ± 4.76, 60.00 ± 4.03 respectively. The Canonical Correspondence Analysis (CCA) revealed NO3−N, water temperature and pH positively impacted abundance of eutrophication indicator species Brachionus and Keratella. An overview of worldwide use of rotifer and crustacean based indices in assessment of TSI has also been discussed. The use of these zooplankton indices to evaluate the trophic status of the ecologically distinct lakes is highly recommended for water quality assessment and management.