Sediment and algae pollution near a reef in Maui. Photo by CORAL staff

Improve Water Quality

Coral reefs need clean, clear water to thrive, but graywater from wastewater treatment plants and stormwater runoff carrying sediment and other pollutants from the watershed are harming reefs. Finding solutions to local water pollution issues is a top priority for CORAL.

In Maui, treated wastewater (“graywater”) has traditionally been routed into coastal injection wells, from which it leaches into the ocean. Even though the wastewater has been treated, it still sometimes contains lots of nutrients like phosphorus and nitrogen. Those nutrients fuel the growth of macroalgae (seaweed), which can overgrow coral reefs and keep sunlight from reaching them: tiny algae “tenants” inside the corals need sunlight to photosynthesize–and in turn feed the corals. In Maui, we are working with hotels to help them switch from potable water to graywater for irrigating landscaping and golf courses. (You can read our guide for hotels here.) This switch will prevent hundreds of thousands of gallons of graywater from entering the ocean each day, reducing ocean pollution. We are also partnering with other nonprofits, hotels, and citizens to install rain gardens that will intercept and filter polluted stormwater runoff before it reaches the reef.

On Hawai’i Island and in Roatan, Honduras, wastewater from residential sewage is leaching into the marine environment. When sewage leeks into the marine environment without being properly treated, it brings with it high levels of nutrients and bacteria. These nutrients lead to an increase in seaweed and marine algae, which compete with coral reefs and often win, while the bacteria can contribute to human health issues. We are working with the local communities through our Clean Water for Reefs initiative to install wastewater treatment systems that will help protect the marine environment (you can learn more about our Clean Water for Reefs project in Puako, Hawai’i here).

Our projects in Hawai’i and Honduras may become a blueprint for other areas around the world, as we implement solutions to water pollution that threatens coral reefs.