Coral reefs face a host of local and global anthropogenic threats that compromise the economic and environmental services reefs provide. Global ocean warming and acidification interact with local coastal acidification and eutrophication on the coral reef at Kahekili Beach Park on the west coast of Maui, Hawai’i. The nearby Lahaina Wastewater Reclamation Facility (LWRF) injects millions of gallons daily of treated wastewater into Maui’s groundwater system. This wastewater-groundwater mixture enters the ocean as submarine groundwater discharge (SGD) that is characterized as low pH, high-nutrient, and low salinity. Since the 1980s, negative effects of the polluted SGD have been recorded along the Kahekili coral reef where SGD seeps are located, including increased algal cover, harmful algal blooms, decreased grazer populations, decreased coral coverage, and increased bioerosion. In addition, the low pH of SGD has been shown to enhance acidification and lead to net dissolution of calcium carbonate. In 2020, during the COVID-19 pandemic, a mandatory visitor quarantine in Hawai’i resulted in a severe reduction in tourism, decreasing the state’s population by about half. The volume of wastewater injected by LWRF also decreased by roughly half and we observed a significant decrease in nitrate concentration and acidification (i.e., increased pH) at and near the Kahekili SGD seeps. We will discuss both the long-term impacts of anthropogenic disturbances and the potential impacts that short-term improvements in water quality had on Kahekili reef seawater and ecosystem health. 

Primary Presenter: Samantha McClain, Texas A&M University (samanthajane12298@tamu.edu)

Authors:

Samantha McClain, Texas A&M University  (samanthajane12298@tamu.edu)

Kathryn Shamberger, Texas A&M University  (katie.shamberger@tamu.edu)

Andrea Kealoha, University of Hawaii  (andreake@hawaii.edu)

Christopher Shuler, University of Hawaii  (cshuler@hawaii.edu)

Tova Callender, West Maui Watershed & Coastal Management  (tova@westmauir2r.com)