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From a river to the ocean

Research Associate Paul Henderson collects a water sample from the Talofofo River, Guam. Samples like this help researchers better understand the effects, both locally and globally, of coastal contaminants in groundwater. As groundwater travels to the ocean, it passes through “subterranean estuaries,” a mixing zone between fresh and salty water analogous to the region where a river meets the ocean. During this transition, transformations both inland and near the coast can influence the amount of chemicals in the water. It is not unusual for groundwater to contain dissolved nitrogen in concentrations 100 to 1,000 times greater than in seawater.
(Photo by Matt Charette, Woods Hole Oceanographic Institution)