Land-based sources of pollution impacts on coral reefs in American Samoa

Land-based sources of pollution (LBSP) pose a significant threat to coral reefs and can induce coastal acidification through nutrient enrichment. In this study, we aim to identify the major source of coastal LBSP in Aua, American Samoa, elucidate the ecological consequences of LBSP, and determine if coastal acidification is impacting the reefs of Aua. Sediment input was the main land-based source of pollution near the stream mouth. Total suspended sediments rather than dissolved inorganic nutrients was the primary predictor of benthic communities with lower adult and juvenile coral densities and higher turf algae in reefs with high sedimentation. Coastal acidification was not observed. Instead, seawater pH was elevated at high LBSP sites where benthic composition was associated with higher turf algae cover, suggesting turf algae may act as a buffer against coastal acidification. Limiting sediment loading into Aua coral reefs would reduce reef degradation.