Mass die-off of corals and invertebrates at East Flower Garden Bank

100 miles offshore of Texas and Louisiana, the Flower Garden Banks National Marine Sanctuary, is considered one of the healthiest anywhere in the region. Last week NOAA scientist were stunned to find green hazy water and expansive patches of white mats killing coral, sponges and everything in its path.

On what is usually a healthy colorful reef, divers found unprecedented numbers of dying corals, sponges, sea urchins, brittle stars, clams and other invertebrates on large but separate patches of the reef. Sanctuary Research Coordinator Emma Hickerson reported extensive white mats covering corals and sponges, and estimates the mortality of corals to be nearly 50 percent in some of the affected areas.

Dying sea Urchin — The remains of a sea urchin recently dead from a large-scale mortality event at the East Flower Garden Banks laying atop dying star coral colonies – these are coated with a white mat of unknown material. Image credit: FGBNMS/G.P. Schmahl

The NOAA team was tipped off by the charter dive boat M/V Fling of the mysterious white mat killing corals, as there was no evidence of the mass die-off at the NOAA site used for long-term monitoring of the bank since the late 1980s. Fortunately twelve miles away, the reefs of the West Flower Garden Bank remain vibrant, bathed in clear, blue water and free of the problem for now.

Until the problem is sorted out, NOAA is recommending the public avoid diving, fishing, and boating activities on the East Flower Garden Bank. The team is hoping to prevent transmission of the outbreak to unaffected locations while researchers investigate several potential causes of the outbreak including poor water quality, disease pathogens and chemical spills.

A massive star coral impacted by a large-scale mortality event at the East Flower Garden Bank. These corals are hundreds and hundreds of years old, and can be lost in a matter of days. Image credit: FGBNMS/G.P. Schmahl

“We know of no spills that have recently occurred near the Flower Garden Banks,” said G.P. Schmahl, Sanctuary Superintendent, “but water temperature over the banks is quite high, at 86 degrees.” In addition, large plumes of low-salinity coastal water have moved offshore following months of extreme rainfall in the region. That water is rich with plankton, nutrients and chemicals that arrive to the Gulf through runoff and river discharges. As the plumes decay, oxygen levels in the water can decrease.

Combined, these stressors could make coral reefs animals and plants more prone to disease outbreaks, or simply fuel the growth of bacterial or algae mats that smother the reefs. Scientists from around the world are offering advice and assistance in trying to help discover the cause. [NOAA]

Tissue sloughing off a recently dead brain coral succumbing to a large-scale mortality event at the East Flower Garden Bank. Image credit: FGBNMS/G.P. Schmahl

Nicole Helgason

Nicole Helgason is a professional scuba diver and can often be found photographing corals and sharing her passion about coral reefs around the world. Nicole is Reef Builders Event Manager and is responsible for running ReefStock shows in Denver and Sydney. Nicole is also a manager for Reef Builders social media accounts and a weekly contributor to the Reef Builders site. Nicole has a Bachelors degree in Coastal Geography from the University of Victoria, and is originally from Vancouver Canada.