Synergic effect of global thermal anomalies and local dredging activities on coral reefs of the Maldives

Abstract

We investigated possible synergic effects on coral reefs of the local land reclamation activities in the Himmafushi Island (North Malè atoll, Maldives) and the global bleaching event that affected the Maldives in 2016. A BACI (Before-After Control-Impact) sampling design was adopted to contrast effects of dredging activities before and after the occurrence of both dredging and bleaching. The Reef Check protocol, a standardised and worldwide survey method, was applied to collect data through underwater visual surveys on corals, macro-zoobenthos, and fish communities.The bleaching in 2016 hit all the reefs investigated, but only in the reefs around Himmafushi (i.e., the impact sites) the live hard coral reduced significantly its cover and the sand deposited on reefs showed a fourfold increase. Substrate indicators (i.e., coral community and abiotic components) turned out to be more effective than macro-zoobenthos and fish in this short-term environmental impact study.