United States Environmental Protection Agency and American Samoa EPA Conducts Ofu Reef Nutrient Reduction Project

November 19, 2025

Pictured in green is the macroalgae valonia fastigiata clothing a coral around the Ofu Reef

An outbreak of a macroalgae called valonia fastigiata, caused by elevated nutrient concentrations, is threatening the reef located near Ofu airport in Manu’a, adjacent to the Vaoto Lodge. In conditions with high nutrient inputs, this macroalgae can undergo a rapid population explosion, enveloping living coral and eventually bleaching and killing the coral. This macroalgae outbreak has been reported in several areas of the Ofu Reef.

The United States Environmental Protection Agency (US EPA) in coordination with the American Samoa Environmental Protection Agency (AS-EPA) recently carried out an assessment of the Ofu Reef. The Ofu Reef Nutrient Reduction Project is an effort between the US EPA, AS-EPA, and the American Samoa Power Authority (ASPA). US EPA Region IX On-Scene Coordinators Chris Reiner and Kazami Brockman led a team to assess and retrieve field and analytical data. Previous surveys conducted in the same area by NOAA, the Coral Reef Advisory Group (CRAG), and the United States Geological Survey (USGS), looked at nutrient concentrations and other indicators along the coast where the macroalgae outbreaks were observed, to identify major sources of nutrients to the reef that may be contributing to the outbreak.

A set of 9 cesspits located at Vaoto Lodge were identified in the study, along with a freshwater spring at the shoreline where the water carrying nutrients from the cesspits discharges into the reef area. The US EPA team and contractor sampled materials in the cesspits, installed and sampled water from three groundwater monitoring wells between the cesspits and the reef, and sampled the freshwater spring at the shoreline for nutrient content. Field testing methods indicated the presence of nutrients in the samples, and the samples will be sent to a laboratory to confirm and provide more detailed results.

The US EPA plans to remove the cesspits, install a replacement system that minimizes nutrient discharges, and arrange for future upkeep, such as pumping out solids, to maintain the effectiveness of the replacement system. Based on the information gathered on this visit, the next steps are to design the system and put together a plan for the work to move forward in 2026. US EPA’s Chris Reiner emphasized the distinctive nature of the Ofu reef, he said “The corals in Ofu Reef are exceptionally tolerant to temperature stress and have been observed to survive and thrive in water temperatures significantly higher than most corals can tolerate. This resilience makes the coral of Ofu Reef an ideal research population and extremely valuable for coral preservation and restoration efforts in American Samoa and throughout the Pacific.”

AS-EPA’s Director Edna Noga highlighted the importance of this project, “Manu’a is abundant in both marine and terrestrial natural resources. We express our gratitude to our counterparts at the US EPA for their unwavering commitment to carrying this project forward, aimed at protecting and preserving the health and safety of the reefs, upon which our community relies significantly. We anticipate working in close collaboration with the local community to ensure project success.”

For more information, please contact AS-EPA at info@epa.as.gov or call (684) 633-2304.