US scientists say a massive die-off is taking place on a coral reef in a national marine sanctuary in the Gulf of Mexico.
Steve Gittings, chief scientist with the Office of National Marine Sanctuaries, reported this week that federal scientists are studying a large-scale mortality event of unknown cause taking place at the East Flower Garden Bank in the Gulf of Mexico.
The reef is part of the Flower Garden Banks National Marine Sanctuary, about 160 kilometres off the coasts of Louisiana and Texas.
Researchers with the National Oceanic and Atmospheric Administration (NOAA) and the Bureau of Ocean Energy Management are reporting unprecedented numbers of dying corals, sponges, sea urchins, brittle stars, clams and other invertebrates, Gittings said.
He said sport divers discovered dead animals on Monday, along with hazy water and patches of white mats coating corals and sponges. The divers alerted nearby federal scientists who were doing annual monitoring work on the same reef.
Gittings said scientists will examine potential causes of the die-off, including poor water quality, disease pathogens and chemical spills.
G.P. Schmahl, sanctuary superintendent, said there have been no known spills at the sanctuary. He said water temperatures are high and that large plumes of low-salinity coastal water have moved offshore following months of extreme rainfall in the region.
Scientists said that water is rich with plankton, nutrients and chemicals and gets into the Gulf through run-off and river discharges. As the plumes decay, oxygen levels in the water can decrease.
Isolated bleaching events and unconfirmed cases of diseases have been reported at the Flower Garden Banks in the past, NOAA said.
By comparison with other struggling coral reefs around the world, Gittings said the Gulf of Mexico coral reefs are considered healthy and stable.
Gittings said reefs elsewhere in the marine sanctuary remained full of life.
NOAA is asking the public to avoid diving, fishing, and boating on the East Flower Garden Bank until the mortality event is better understood.
