1. Introduction Coral reefs are a vital marine resource for Cook Islanders, yielding a variety of foods, supporting sustainable tourism and providing coastal protection. The low-lying almost-atoll of Aitutaki is surrounded by a barrier reef and numerous sand islands (motus). Aitutaki’s reefs are subject to a number of threats, including fishing pressure, marine debris and poor water quality from land runoff. Small nations struggle with maintaining economic stability as well as environmental protection. However, the economy is reliant on eco- tourism. Vibrant coral reef ecosystems at Aitutaki are imperative for the nation to thrive. H o : The coral reefs at Aitutaki’s lagoon are degraded due to anthropogenic stressors from residents of the island and their interaction with the marine environments. The reef team surveyed fish species, corals, algae, and invertebrates. At each site the team conducted four, ten meter transects. Laid 10m transect along the reef, while identifying and counting all the fish in a four meter width along the transect. Identified and counted invertebrates along the transect, recording and identifying invertebrates within a two-meter wide band. Measured the sizes of invertebrates that lay within the transect Measured the height of the coral at each meter mark along the transect to characterize reef topography. Identified the substrate, using a point intercept method, noting which corals, algae, rocks or other substrate lay beneath the transect tape. Assessing the health of coral reef ecosystems in an era of anthropogenic stressors at Aitutaki, Cook Islands Vanessa van Heerden Environmental Science and Resource Management Program, California State University Channel Islands e-mail: vanessa.vanheerden832@myci.csuci.edu Methods Reef Health Index (RHI) Coral reefs are among the highest diverse ecosystems in the world. If these environments continue with the rate of degradation, there will be a fundamental loos of commercial fisheries, tourist industries, and economic stability for many island nations. In a world overrun by humans, small nations like Aitutaki are challenged to balance ecological preservation and economic gain. Understanding these anthropogenic influences is an important step in protecting and managing these habitats. Conclusion ESRM Program The global RHI is based on 4 indicators, which are combined and equally weighted. Live coral cover is the proportion of reef that is covered by live coral pieces or live bommies. Fleshy macroalgae cover is the proportion of reef that has fleshy algae. For this project, species richness of fish is the biodiversity indicator of reef health instead of key herbivorous and commercial fish. Acknowledgements: A sincere thank you goes to Dr. Kiki Patsch, Dr. Clare Steele, and Dr. Sean Anderson for all of the guidance throughout this process as well as Aimee Newell and Laura Powell for being the best Reef Team in the Cook Islands. Thank you to IRA funding for allowing students from CSUCI to conduct research in the Cook Islands. Results Human proximity significantly decreases (p<0.01) in the species richness of fish between mainland and motu sites. The outer and less frequently visited reefs were denoted as higher quality than those closer to inhabitance. Harvesting commercial fish ( Lutjanidae, Serranidae ) has increased fishing pressure. This furthers the notion that anthropogenic stressors could be a primary influence over the reefs in Aitutaki’s lagoon. The average score for RHI in Aitutaki’s reef ecosystems is: 2.8. Discussion: Sea Cucumbers as Indicators of Lagoon Health Sea cucumbers are known indicators of excess nutrients in water. This is exemplified with a significant difference of sea cucumbers (p=0.008) around the main island than the surrounding motus. Tropical waters are oligotrophic and a conversion to eutrophic waters shows the impacts that land runoff from residents.