Long Term Monitoring of Coral Reef Fish Populations Under Increasing Ocean Temperature and Acidification Stress

Abstract

Coral reefs are especially sensitive to ocean warming and acidification caused by climate change and can have a major impact on reef-associated fish species and reef stability. This study analyzes the diversity of coral reef fishes over time using data from the National Coral Reef Monitoring Program (NCRMP) of NOAA from the year 2014 to 2024 from the Hawaiian Archipelago. The impacts of environmental factors such as sea surface temperature, ocean pH, and coral cover were evaluated on fish population structure. Shannon Diversity Index as the main statistical method to quantify the changes in biodiversity between monitoring years. The mean sea surface temperature (MST) ranged from 26.8°C in 2014 to 29.1°C in 2024, with a steady increase over the years, whereas the mean pH decreased from 8.12 to 7.95 over the years. During the same time frame, there was significant loss of coral cover, from 62% to 36%. The Shannon Diversity Index was then found to have decreased from 3.45 to 2.51, representing a loss of some 27.2% of biodiversity. The results indicate that the diversity of coral reef fishes is negatively correlated with environmental stress. Fish functional groups were further simplified, with habitat specialist fishes being more affected than generalist fishes under climate stress. The rising temperature and acidification of the oceans are important factors in the decline of coral reef fish. The continued monitoring and adaptive conservation strategies will be critical to ensure that reef biodiversity will persist into the future under different climate change scenarios.