For the past sixteen years, the Seattle Aquarium has been conducting a groundbreaking study of Puako Reef, along with two other west-facing reefs off Mahukona and Old Kona on Hawai’i Island. This unique study method allows scientists to collect consistent, long-term data from the exact same locations year after year. Their goal is to monitor and analyze changes in coral composition, coral coverage, and fish populations. This research not only contributes to the broader scientific understanding of ocean ecosystems but also provides critical insights that help communities and governments address the environmental and human-induced pressures on coral reefs.

Every year, a team of scientists, equipped with scuba gear and overseen by a dive safety officer, descend to the same locations, swimming along the same transect lines as in previous years. They capture videos and photographs of the reefs and fish populations. Upon returning to Seattle, they spend the year meticulously reviewing their images, counting every fish, and carefully measuring the coral coverage.

One of the key indicators of the health of a reef and the strength of the surrounding waters is its ability to recover from traumatic events, such as coral bleaching, which can occur when water temperatures rise too high for a brief period. Hawai’i Island experienced such an event in 2014. Thanks to the Seattle Aquarium’s ongoing studies, we now have valuable data showing how three distinct reefs—Puako, Mahukona, and Old Kona—recovered from this bleaching event. While all three reefs face similar stressors; climate change, storm surges, runoff, and fishing practices, only Puako is burdened with the added stress of wastewater pollution, which leaks directly onto the reef from nearby homes.

The difference in recovery is stark. As shown in the before-and-after photographs extracted from the team’s videos in 2012 and just two weeks ago in 2025, Puako Reef is struggling to recover, while Mahukona and Old Kona are bouncing back at an expected rate. Worse, the fish populations on Puako Reef, which feed on the algae fueled by wastewater, are growing at an alarming rate.

The evidence is clear and urgent: We must remove all wastewater from Puako Reef. Installing a sewer system in the areas surrounding the reef is no longer optional—it is critical. The coral coverage on Puako Reef used to be 70%, but it has now plummeted to just 7%. If it falls below 5%, scientists are doubtful that recovery will be possible.

The photographs below were taken by Seattle aquarium scientists to capture the differences in coral coverage on the reef in the exact same locations year over year.  As you look at them, notice how the coral coverage in Mahukona and Old Kona are very similar in the before and after photos while the coral has not recovered as well in Puako.