Through murky waters: conservation implications from evaluating the drivers of diversity and abundance on coral reef communities in Cambodia

Abstract Cambodia’s coral reefs are vital for supporting marine biodiversity and coastal livelihoods, but they remain understudied and are increasingly threatened by overfishing, habitat degradation, and climate change. Using Reef Check citizen science data from 91 reef sites (2021–2023), we examined how turbidity and productivity, sea surface temperature (SST), hard coral cover and marine protected area (MPA) designation shape coral reef communities across nearshore and offshore reefs. Our analyses revealed distinct benthic, fish, and invertebrate communities nearshore and offshore. Offshore reefs, characterized by lower turbidity and dominated by branching corals, hosted more fusiliers (Caesionidae) and wrasses (Labridae), and had higher abundances of fish and invertebrates. Nearshore turbid reefs dominated by massive and encrusting corals exhibited higher invertebrate diversity despite lower fish and invertebrate abundance. Hard coral cover increased fish abundance and biomass. Warmer SSTs were associated with reduced fish diversity. Reefs within the Koh Rong Marine National Park did not have higher fish or invertebrate diversity, abundance or targeted fish biomass than outside the MPA, which may reflect mixed zoning, site selection history and enforcement limitation. Our findings showcase the contemporary status of Cambodian reefs, and the potential of citizen science to support baseline monitoring. We recommend expanding MPAs to connect offshore and nearshore reefs while accounting for fishing pressure and enforcement capacity. We also show that integrating satellite data with citizen monitoring can aid adaptive marine conservation planning.