Reef degradation on Maui linked to quality of coastal groundwater Land-based pollutants, such as fertilizers and chemicals in wastewater, infiltrate into the groundwaters beneath land and eventually exit into nearshore ecosystems as submarine groundwater discharge (SGD)--seeping into the coastal zone beneath the ocean's surface. A new study used a combination of field experiments and chemical analysis of water and algae to show that the quality of coastal groundwater plays a major role in determining the health of nearshore ecosystems in Hawai'i. https://www.sciencedaily.com/releases/2016/11/161116101435.htm