Places We Protect


Island of Hawai’i

A diver entering the water from a rocky shore.
Puakō Monitoring Conducting coral reef surveys off the coast of Big Island, Hawai’i. © John De Mello

Investigating causes of coral and fish declines and promoting actions to minimize pollutants.

Underground freshwater streams flowing beneath Puakō and entering the ocean through springs and seeps once nourished an abundant fishery and vibrant coral reefs. But residents started noticing a decline in these resources in recent decades and, in 2007, the Puakō Community Association asked TNC to investigate.

After reviewing historic research reports and conducting coral reef and fish abundance surveys to assess current conditions at Puakō, our scientists confirmed that half the coral has died and fish populations have suffered similar declines in the last 40 years.

Using Science as Our Guide

Many residents and fishermen believed roi, a non-native grouper, was partly to blame for the decline of native Hawaiian fish populations. So, with the help of fishers and divers and in partnership with the University of Hawaiʻi and the State’s Division of Aquatic Resources, we conducted a 5-year study to assess the feasibility, cost, and impact of roi removal. The study confirmed that, although it is feasible and affordable, the absence of roi had no significant impact on native fish.

With the assistance of community volunteers who monitored fishing activity for a year, we also examined the impacts of harvesting at Puakō. The analysis revealed that up to 1/3 of the catch was under the legal size limits, which are designed to ensure fish grow large enough to reproduce before they are harvested, and that fewer than 1 in 5 fishers were from the Puakō community.

Untreated wastewater leaching from outdated systems called cesspools was also suspected as a factor in the decline of Puakō’s reefs and fish. So in 2011, we teamed up with scientists from Cornell University, the University of Hawai‘i at Hilo Marine Science Department, and the Hawai‘i Institute of Marine Biology to investigate. Using dye to trace untreated wastewater from cesspools, scientists confirmed that subterranean groundwater flows carry untreated wastewater through permeable rock to beaches, tide pools, and the reef in as little as three hours. We also found that bacteria levels associated with sewage exceeded Hawai‘i Department of Health standards in some areas, including popular beaches. Read a summary of what our investigations found.

Two researchers stand on a beach with clipboards and a water monitoring instrument.
Water-quality testing at Puakō TNC staff and trained volunteers conduct monthly water quality monitoring at Puakō in Hawaiʻi. © TNC

Impacts on Human Health and Marine Life

Exposure to domestic wastewater can cause skin, urinary, blood, and abdominal infections like gastroenteritis, Hepatitis A, conjunctivitis, leptospirosis, salmonellosis, and cholera. Children and the elderly are particularly susceptible to these infections. Domestic wastewater also increases disease risk in reef animals and promotes the growth of invasive algae that smothers corals and reduces oxygen levels necessary for other animals to survive.

Moving Forward

Results of the wastewater studies prompted residents to begin a process to upgrade their wastewater systems. Continuing research—aided by trained volunteers who conduct monthly water quality monitoring—is improving our understanding of untreated wastewater’s impacts on reefs and fish. It also helps the community as they assess alternative wastewater treatment options to eliminate these pollutants and the risks they pose to coral reefs, to fish, and to people.

Read a survey summary to learn more about what’s in the water and how it affects marine life and human health.

Learn more about our science, restoration, and how we help strengthen conservation management and leadership so Hawaiʻi’s reefs can support healthy fisheries and prosperous communities long into the future.