Using microphones 3,000 feet below the surface of the Gulf of Mexico, scientists learned: Whale and dolphin groups 10 years after the Deepwater Horizon oil spill, numbers are still falling.
Some of these species were initially expected to fully recover within a decade.
The researchers analyzed deep-sea recordings collected at five locations in the Gulf of Mexico between 2010 and 2020. They used an algorithm to help identify toothed whale vocalizations, their echolocation “clicks,” that can be attributed to a specific whale species. The researchers estimated the number of whales based on the number of clicks captured in the recordings.
in a Papers published last month Sperm whale numbers may have declined by 31 percent, a team of scientists led by researchers at the Scripps Institution of Oceanography at the University of California, San Diego, reports in the scientific journal Nature Communications Earth & Environment. Some dolphin populations may have declined by as much as 43%.
Beaked whales, a reclusive deep-sea animal with a snout that looks like a dolphin, have seen their numbers drop by 83%. they are expected to have full recovery Within 10 years after the spill.
“Sperm whales, dolphins, beaked whales are in decline across the board,” said Scripps oceanographer Kaitlin Frasier, the study’s lead author.
Sperm whale flukes found in the Gulf of Mexico. (Photo courtesy of NOAA Photo Library.)
“There’s a lot of evidence that this is a significant phenomenon that could be related to the impact of the oil spill,” Fraser said.
lingering influence
The 2010 Deepwater Horizon oil spill was the largest oil spill in history, spewing approximately 134 million gallons of oil into the Gulf and forming an oil slick Over 43,300 square milesroughly the size of Virginia. The drilling platform explosion killed 11 people.
Post-spill scientific assessment Estimating the impact of the disaster Marine mammals, used to determine BP responsibility. In the 10 years since the oil spill, oil companies have spent Approximately US$69 billion About cleanup. Some whale species are not expected to fully recover for 10 years, but most whale populations are expected to at least begin to rebound by then.
Fraser said her team’s research showed “no evidence” that the original assessment was correct.
An explosion on the Deepwater Horizon oil rig south of Venice on Wednesday, April 21, 2010, injuring at least 15 workers and leaving 11 missing, caused an oil slick to drift away from the scene as fire boats tried to put it out. Photo), Times-Picayune)
Andrew Read, a professor of marine biology at Duke University who was not involved in the study, said her team provided “direct measurements showing that these animals have experienced significant and widespread declines since the oil spill.” .
Tina Yack, a research scientist at Duke University’s Marine Geospatial Ecology Laboratory who also was not involved in the study, noted that the study will only count whales that vocalize.
“The authors are careful to point out that relying on echolocation clicks means silent or non-foraging animals are not taken into account and may underestimate local population sizes,” she said.
“massive quiet”
Fraser said funding for the program was at times difficult to maintain during the 10-year study. She said they traveled to research sites on shrimp boats and raised money through various research grants.
Reed said placing expensive microphones on the ocean floor would require a “huge leap of faith.” Each device costs about $20,000 to build and $1,500 a year to maintain, Frasier said, and her team maintained five microphones on the bottom of the bay for 10 years.
The High Frequency Acoustic Recording Package (HARP), an undersea microphone used to record whale vocalizations, can be seen on the deck of a research vessel. (Photo courtesy of Caitlin Fraser)
When it came time to recover the recording device, the researchers used an underwater speaker to play a sound in the water (Fraser described it as a code for a series of beeps), telling the underwater recording device to drop its iron weight and float to the surface.
A High Frequency Acoustic Recording Package (HARP), one of the deep-sea microphones used by researchers to estimate whale populations in the Gulf of Mexico, can be seen on the deck of a research vessel. (Photo courtesy of Caitlin Fraser)
“Imagine walking through a forest filled with the sounds of birdsong that are familiar to you,” Reed said. “Then something happens. There’s a big storm, or a fire, and when you walk through the woods again, it’s quiet.”
“That’s it [Frasier’s] The research team found,” he added. “Parts of the Gulf of Mexico affected by the Deepwater Horizon oil spill have seen massive lulls, either because the animals have left or because they have died.