USGS collaborates with National Park Service to study threatened coral reefs in American Samoa

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USGS scientists from the Pacific Coastal and Marine Science Center and the St. Petersburg Coastal and Marine Science Center are cooperating with the National Park Service to better understand links between coastal groundwater and coral reef health on the island of Ofu in the National Park of American Samoa (NPSA).

Underwater photo of divers wearing oxygen tanks, placing instruments on coral reef.

Dive operations installing tide, wave, temperature, and salinity sensors on the fore reef in the National Park of American Samoa off the south shore of Ofu, Manuʻa, January 30th, 2020.

These corals are exceptionally tolerant to high ocean temperatures—a problem associated with global climate change—and could be a valuable source of thermally tolerant coral types. But an outbreak of Valonia fastigiata algae is outcompeting the corals, threatening to change coral-dominated reefs into algae barrens. Excess nutrients from fertilizer, wastewater, and other human sources might be fueling the algae growth. USGS scientists are conducting fieldwork on Ofu in late January and early February to study the chemistry of the corals and coastal groundwater and to measure physical factors such as waves, currents, and seepage of groundwater into nearshore seawater and onto the reef.

Learn more about the USGS Coral Reef Project.

A man pushes a pole upright into its stabilization frame, surrounded by other equipment and palm trees.

USGS scientists install a thermal imaging system in the National Park of American Samoa.

Two people pointing at a laptop computer screen which is displaying an image with varying colors.

The first image produced from a thermal imaging system shows an image of a submarine (cold and fresh) groundwater discharge plume emanation from the shoreline and propagating over the reef flat. USGS scientists installed the system in the National Park of American Samoa off the south shore of Ofu in the Manu‛a Islands Group of American Samoa. The groundwater could potentially be responsible for carrying the nutrients that caused an algal outbreak that is overwhelming and killing the thermally-tolerant, federally-protected corals in the Park. USGS will test water samples taken from the area to measure nutrient levels.

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