Evaluation of Nearshore Coral Reef Condition and Identification of Indicators in the Main Hawaiian Islands

Abstract

The primary objective of this research is to identify indicators that can accurately predict decline in the condition of Hawaiian coral reef communities and aid in the assessment of identification of the forcing functions involved. This large-scale assessment, including all eight islands, covers the greatest spatial scale in the Main Hawaiian Islands to date. The major results of this research include the development of an extensive baseline database for future research and comparisons, the description of Hawaiian coral reef communities on a large scale, and the identification of key factors influential in explaining spatial patterns of biotic populations and their linkages to impaired conditions. Although it was determined that no single factor had a correlation strong enough to substitute as a direct measure of coral cover, a combination of both natural (topographic relief, depth and wave energy) and anthropogenic (human population and stream distance) factors are most influential in explaining the variability in coral community structure. A similar pattern exists for fishes, where both natural (topographic relief, coral diversity, coralline algae, precipitation, and latitude) and anthropogenic (human population and organics) variables heavily influence fish communities. With substrate rugosity most highly correlated with fish population parameters, identifying areas of high spatial complexity can provide a simple measure to assist managers in designing and implementing marine reserves and proposing fishing regulations. Sediment composition and grain-size can be indicators of environmental stress. Although wave energy is the most important factor in structuring Hawaiian coral reef communities, when fine sediment overwhelms the system it becomes the dominant forcing function on community structure. A statistical model was developed and tested to rank reef condition.