Chitosan has the potential to improve water quality without negative effects on the coral, Porites lobata

Coral reefs off the coast of West Maui in Hawai'i are frequently subjected to highly turbid water, caused in part by terrigenous sediment inputs from stream gulches after rain events. Sediment has numerous deleterious consequences on scleractinian corals, including impacts on growth and survival. The finalized West Maui Watershed Management Plan includes recommendations to reduce sources and conveyance of land-based pollution to increase resiliency of coral reefs. This study investigated the use of the flocculant, chitosan, for potential use near sensitive coral reef ecosystems. In a laboratory-based experiment, chitosan did not impact growth of Porites lobata during a 30-day exposure. Additionally, chitosan significantly reduced turbidity within 1 h of addition in both seawater and freshwater. These data suggest that chitosan does not negatively impact one of Hawai'i's common coral species. This study provides the foundation for further research investigating the ecosystem effects of chitosan application when used as a potential mitigation action to reduce sedimentation in West Maui's coral reefs.