The catastrophic explosion that spewed some five million barrels of oil deep into the Gulf of Mexico in April 2010 will take a heavy toll in the ocean’s lowest layers for years to come. That’s the stark conclusion of seafloor research conducted six months after the Deepwater Horizon oil spill.
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The study, published on August 7 in PLoS ONE, examined life in the Gulf’s deepest waters near the blowout, about 1.6 kilometers below the surface. Here, the researchers found that the damages will take decades to reverse. The work is part of the Natural Resource Damage Assessment, created by the U.S. National Oceanic and Atmospheric Administration. The assessment will help set the damages charged to British Petroleum (BP), which operated the well.
At those depths in the Gulf of Mexico, three types of creatures thrive: worms, shellfish, and mollusks. The scientists studied sediment samples collected at different distances from the destroyed oil wellhead to determine how the oil and dispersant chemicals affected the ecosystems. The sediments yielded a census of the animals that live in the mud, as well as a measure of the contaminants that lingered.
“The sediments are like little canaries in the coal mine. We used them to find out what’s going on,” said lead author Paul Montagna, a deep-sea environmental scientist from Texas AM University, in an interview with mongabay.com.
The closer the team surveyed to the well, the less diversity of marine life they found. Nearest the disaster site, crustaceans and shellfish suffered greatly; these creatures are particularly sensitive to pollutants in the deep sea. Worms were still numerous, although their numbers declined closer to the well.
The scientists used the data to designate healthy and unhealthy areas in the deep sea depending on each location’s “footprint” of oil impacts. High-impact areas were unhealthy, with heavy contaminants and low levels of animal life. Low-impact locations were low in contaminants and high in animal diversity. The researchers then mapped the impact zones across an area covering 148 sq km, about the size of a small city. They colored the “severely impacted” zones red, the “moderately impacted zones” orange, the “low zones” yellow, and the “normal zones” green.
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Map image via Shutterstock.