Impact of maintenance dredging on macrobenthic community structure of a tropical estuary

This paper demonstrates the impact of maintenance dredging activities on the macrobenthic community structure of a tropical monsoonal estuary (Cochin estuary), located in the southwest coast of India for three consecutive years. The results of the study indicates apparent differences in benthic fauna and sediment characteristics between dredging and non-dredging sites, while most of the hydrographical parameters (temperature, pH, DO and BOD) exhibited inconspicuous variations. The dredging sites were characterized by significantly lower faunal density, biomass, and diversity and sustained distinct benthic faunal communities. The tubificid Oligochaeta, an opportunistic benthic taxon, was highly abundant in the dredging sites along with less density of Mollusca and Amphipoda. Prominent distinctions were evident in the feeding guilds of macrobenthic fauna between the dredging and non-dredging sites. The Benthic Opportunistic Annelida Amphipods Index (BO2A index), an index of benthic habitat quality showed relatively higher values (>0.24), which indicates the prevalence of poor environmental conditions in the dredging locations. The present study reveals the extent of impacts associated with maintenance dredging activities in a tropical estuary, which can be used to formulate effective management strategies for the protection of ecologically and economically significant benthic communities of estuarine ecosystems.