Assessing the effects of NPS pollution on American Samoa’s coral reef communities

Houk, Peter

Both biotic and abiotic factors influence coral reef development. Understanding coral reef community development can benefit long-term coral reef monitoring programs and short-term environmental impact type studies alike. This underlying characterization can allow for better experimental isolation, and subsequent analysis of anthropogenic variables such as pollutant loads. Surveys were completed on Tutuila Island, American Samoa, to characterize reef development and assess the effects of non-point source pollution on adjacent coral reefs. Multivariate analysis of benthic and coral community data suggest that similar development exists at three locations; Aoa, Alofau, and Leone. Among these sites Aoa reefs show the highest estimates of healthy substrate and greatest species richness. Of the remaining sites, Masefau and Fagaalu seem to be related in terms of their geomorphology, but not in terms of their present health. Analysis of benthic data suggests that the Fagaalu site is heavily impacted when compared with all others. The Fagaitua site differs from all other reef community development based upon partial exposure to prevailing trade winds and ocean swells. This site shows high abundances of crustose coralline algae, relatively high coral community evenness measures, and high diversity suggesting good health. The exposure may explain the absence of large coral colonies despite good reef health. Absolute measures of the present reef community at all sites were made to establish EPA Aquatic Life Use Support designations. The Aoa site resulted in a fully supportive ranking, the Fagaalu site resulted in a non-supporting ranking, and all others were partially supportive of EPA’s aquatic life criteria. Future monitoring should include sites from each type of reef development but varying in levels of non-point source pollution to best evaluate degradation from increased pollution or success from good management.