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Dying reef mystery solved

White bacterial mats smothers beautiful reefs

A white mat of bacteria coats a dying sponge at the East Flower Garden Bank during a large-scale mortality event
A white mat of bacteria coats a dying sponge at the East Flower Garden Bank during a large-scale mortality event (FGBNMS/G.P. Schmahl)

JACKSONVILLE, Fla – Scientists think they know why Gulf of Mexico reefs have been dying on the East Flower Garden Banks and it has to due with heavy rain.

During 2016, in an area equivalent to about five football fields, something killed corals, sponges, crabs and other invertebrates in a Gulf national marine sanctuary.

Flower Garden Banks no longer held the brightly colored sponges, plants, and other marine life that fishermen could see below their boats.
 
Instead divers spotted a dead zone covered in white bacterial mats and the culprit remained a mystery.

Until recently researchers were puzzled by the the mortality event. It was unlike anything ever seen before and didn’t resemble any known coral disease or damage.

The ruled out an oil spill or any direct factor but attributed the event to a combination of several environmental stressors, with low dissolved oxygen playing a key factor.

Oxygen levels dropped after heavy rainfall washed into the Gulf of Mexico and floated above denser salty seawater.

According to Andrea Kealoha at Texas A&M, hazy freshwater at the surface may have blocked sunlight and photosynthesis, reducing the oxygen content in the water which coral animals need for survival.

Organic matter decaying in the water further depleted oxygen in the decomposition process.

Warm sea surface temperatures are causing coral bleaching around the world and in July surface temperatures and bottom temperatures were the highest ever recorded in the Gulf according to Dr. Robert Hetland of Texas A&M University. 

Stressed corals could have been that extra factor triggering their harm. 
 


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