Abstract

Rapid urbanization has induced stress on water bodies, its ecological components resulting in the disappearance of native biodiversity. Water bodies are being restored due to public pressure and implemented by the government agencies focuses only on increasing storage capacity of water bodies than retaining the biological components of the ecosystem. In the current study, wetlands of Bangalore’s urban region were selected to assess the effectiveness of restoration using diatoms as bioindicators. Five wetlands viz., prior-restoration, post-restoration, polluted, reference and previously restored wetlands were chosen. The water quality revealed no major changes in conductivity values among prior-restoration and post-restoration period. Influence of chemical factors was evident from the varying diatom assemblages within water bodies. The well-known tolerant taxa like Nitzschia umbonata, Cyclotella meneghiniana, Halamphora veneta and Gomphonema parvulum were predominant in samples prior to restoration reflecting nutrient rich-pollution status. Compared to this, Achnanthidium sp. and Gomphonema sp were dominant in reference wetlands. One-way ANOVA revealed a significant (p<0.05) change in the percentage of eutrophic taxa (%ET) from a reference to polluted wetlands but no significant % ET change was noticed among prior-restoration, post-restoration and previously restored wetland types. Severe fish kill was recorded in ulsoor wetland (restored ~8 years back) because of improper restoration management. Proper restoration and management, requires regular cost effective monitoring and the current study focuses on diatom based biomonitoring in routine water quality assessments. This would reveal the ecological integrity and would also be cost effective supplement to chemical analysis and easily implementable for monitoring urban wetlands.

Keywords: Diatom ecology, De-silting, Water quality, Tank ecosystems, Urban pollution, Sewage management.