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Marine Science

DEEPWATER HORIZON STUDY REVEALS FISH IMPACTS

DEEPWATER HORIZON STUDY

Deepwater Horizon study reveals fish impacts. On April 20, 2010, the offshore oil drilling ship Deepwater Horizon exploded, killing 11 crewmen and resulting in over $60 billion in clean-up costs, penalties, fines and restitution to affected businesses. The drill ship sank two days after and leaked about five million barrels of oil into the Gulf of Mexico, just 50 miles south of Louisiana’s coastline. This eventually became the largest accidental marine oil spill in global history.

Researchers from the University of South Florida (USF) were on scene shortly after the sinking, pressing the newly acquired research vessel Weatherbird II into service as the first scheduled research expedition to collect water samples and other critical information, thanks to rapid funding granted by the USF Foundation and the National Oceanic and Atmospheric Administration (NOAA).

Weeks after the disaster, BP announced a $500 million fund, distributed over 10 years by the independent Gulf of Mexico Research Initiative (GoMRI) to help scientists and communities understand the immediate and long-term impacts on marine life and coastal environments. Over the ensuing decade, USF received a significant portion of the funds, totalling over $37 million, to establish the Centre for Integrated Modelling and Analysis of Gulf Ecosystems (C-IMAGE), an international consortium of professors, post-doctoral scholars and students from 19 collaborating institutions. C-IMAGE’s goal has been to conduct research and make critical scientific conclusions that impact policy-driven recommendations for the future of deep-water oil drilling. C-IMAGE is one of dozens of consortia, research teams and individuals that received GoMRI funding.

One of the most significant contributions by C-IMAGE researchers has been to compile the first comprehensive baseline of oil contamination across the entirety of the Gulf of Mexico. Researchers sampled over 15,000 fish and took over 2,500 sediment cores (see map), initially finding high incidences of skin lesions and other abnormalities in fish near the Deepwater Horizon site, which abated over time. In addition, high levels of oil contamination were detected in fish that also declined with time.

“We’ve been pulling together all of these critical pieces of research and incorporating them into larger ecosystem-wide modelling studies. This is the basis for making predictions of how the Gulf will respond to future spills and deep blowouts,” said Steven Murawski, director of C-IMAGE and endowed chair of biological oceanography in the USF College of Marine Science.

Since 2010, studies show a 50 to 80 percent population decrease in deep water (mesopelagic) fish populations near the blowout site. This could have lasting impacts in other areas of the Gulf due to their movement patterns and the fact that these species are important prey for many other Gulf animals including predatory fish, squids and marine mammals. Among the species, oyster, blue crab, bottlenose dolphins, red snapper and southern hake show population declines.

One of the important observations from the Gulf-wide survey of fish is that all species subjected to detailed chemical analyses revealed some degree of oil pollution. A recent study published in “Nature Scientific Reports” looked at 2,500 individual fish representing 91 species from 359 locations across the Gulf. USF marine scientists found the highest levels of oil exposure were detected in yellowfin tuna, golden tilefish and red drum.

“Literally all the fish that we’ve tested have some level of hydrocarbon; there are no pristine fish in this system,” Murawski said.

Scientists also found traces of oil compounds in the lipid storage reserves in fish that can be passed onto future generations through their eggs. In efforts to better understand the spill’s long-term impact, researchers have been studying spawning activity sites for various species and recently launched a 15-year study to track fish eggs using a DNA identification system called barcoding. This study, funded by the Florida Restore Act Centres of Excellence programme, will help locate precisely where fish spawning hot spots occur and potentially lead to greater protections for these areas.

While the Deepwater Horizon spill was catastrophic, its footprint remained limited to the Gulf due to an anomaly in the offshore “loop current” that prevented oil-tainted Gulf waters from moving up the U.S. east coast.

USF researchers were the first to discover that oil was widely distributed on bottom sediments along the northern Gulf, thus providing evidence that not all oil floats. Ernst Peebles, associate professor of biological oceanography, and David Hollander, professor of chemical oceanography, worked together to identify specific chemical compounds in sub-surface oil plumes northeast of the wreck site by using a filtration process to isolate the oil droplets. This conclusively linked the subsurface plumes northeast of the site to the oil from the blowout. The blowout occurred at about 1,500 meters deep and under extreme pressures 150 times that at sea level. As the oil escaped the 21-inch wellhead pipe and into this highly pressurized system, it was atomized into micro droplets and rose through the water column until it was neutrally buoyant, creating the sub-surface plumes. This was of major concern for scientists since marine life moves throughout the deep Gulf, traversing the sub-surface plumes and transporting the oil with them.

“There was an enormous amount of chemistry that was going on, physical interactions at the molecular and intra molecular level, that lent itself to really unique circumstances,” Hollander said.

Sediments, or mud samples, taken from the seafloor at different sites around the wellhead revealed traces of oil there as well. The oil attached to suspended planktonic particles, settled through the water column and was ultimately deposited on the seafloor, a mechanism known as “Marine Oil Snow Sediment and Flocculent Accumulation” (MOSSFA). This accumulation accounted for upwards of 10 percent of the total oil released. Biological systems living near or on the seafloor interact with MOSSFA and are continuously re-exposed to the oil compounds. Researchers examined biota from this region and showed that these “indicator species” and other invertebrate communities had varied impact and recovery rates.

In an effort to predict recovery rates of the deep ecosystem of the Gulf, researchers were compelled to look back in time to examine the benthic system in the southwestern region of the Gulf, where a previous mega-oil spill oil occurred. The Ixtoc 1 spilled for months during 1979-1980 in the Bay of Campeche, Mexico, at 50 meters deep and spilled about two-thirds of the oil compared to the Deepwater Horizon event.

Studies in the Bay of Campeche conducted by C-IMAGE researchers focused on the sediment layers around the Ixtoc 1well to examine whether the seabed still contained any traces of oil from the spill from 40 years prior. Researchers extracted sediment cores from the seabed, a sampling technique that allows the analysis of sediment layers accumulating over time. This allowed scientists to put a “time stamp” on any traces of oil they found.

“Ixtoc 1 provides us with a vision for what we can expect will be left of the Deepwater Horizon spill in 40 years. This type of information is invaluable for assessing long-term impacts in the event of yet another large volume spill,” Hollander said.

Hollander’s geochemical studies show that even after four decades, oil components persist in underwater sediments to this day. As much as two million barrels of Ixtoc 1 oil were estimated to have settled on the seafloor and on coastal marshlands primarily in the Bay of Campache.

They’ve also taken data from dozens of other spills and used the findings from Ixtoc 1 and the Deepwater Horizon as baselines to determine the impact of oil in sediments. These studies help develop and “ground truth” predictive models that explain how microdroplets of oil break down and spread under water. Interaction with bacteria and phytoplankton contribute to the biodegradation of oil, but these transformation processes also alter the Gulf’s natural ecosystem and affect tiny and larger marine life in unknown and unexpected ways.

“These transformation products potentially can be more dangerous than their precursor compounds,” said Isabel Romero, a research associate in the USF College of Marine Science.

Romero joined Hollander’s research team in 2012 as a postdoctoral scholar. She’s been studying the chemical interactions of the oil traces found in the deep pelagic system and their lasting effects on future generations of fish and invertebrates. In 2015, Romero became a research associate at USF and received several grants to continue her work, including her involvement in another GoMRI-funded consortium, the Deep Pelagic Nekton Dynamics of the Gulf of Mexico.

More recently, Romero received funds to continue studying deep-sea environments through the National Academy of Sciences and the NOAA RESTORE Science Program. C-IMAGE has provided early career opportunities for researchers such as Romero and has contributed to the educations of over 200 undergraduate, graduate and post-doctoral scholars who’ve benefited from working across multiple disciplines, institutions and countries.

“Being able to grow in a group of scientists for the last eight years, that’s a once-in-a-lifetime opportunity,” Romero said. “The GoMRI program opened my vision of working in different environments with very different techniques and people to understand basic, but very important questions of the deep pelagic ocean of the Gulf of Mexico.”

One of USF’s greatest achievements over the last 10 years is developing intense and consistent multi-disciplinary research and collaboration between scientists and students in different disciplines of science (biologists, chemists, engineers, geologists, etc.). They created new methods, raised different questions and modified tools to accommodate their interdisciplinary approaches. Students have gone up the academic ranks into graduate, post-doctoral positions, leading their own studies using the techniques and relationships from their experience. Other students have since found jobs as oil experts to help drive policy changes and staff agencies and private businesses dealing with oil spill preparedness.

“From day one, the students were indoctrinated for the big vision. Master’s degrees and PhD dissertations have turned into publications in very well-respected journals,” Murawski said. “They learned how to become professionals and also had to do something very significant in society, and that’s pretty much all you can ask for in an academic experience.”

C-IMAGE disbands at the end of June 2020. GoMRI will continue through the end of the year to synthesize all the studies completed with the BP-funded grant. While there are many lessons learned that will help during the next response to a major oil spill, the end of the 10-year grant brings many questions about what’s next.

USF researchers continue to search for additional funding to build on the C-IMAGE legacy. The expansion of offshore drilling, particularly into the ultra-deep sea, is of major concern to scientists. As the industry moves drilling into deeper waters, predictive models and methods will need adjustments.

“One of the things that we’ve strived to do is to point out that the conditions in this industry are changing dramatically and we need to be nimble enough to respond to new conditions as opposed to old conditions that we understand,” Murawski said.

The Deepwater Horizon explosion created some unusual challenges for researchers. Time was a main factor in the aftermath of the BP oil spill. Coastal communities, fishing industries, policy makers and the public needed to know the impacts of the oil spill at speeds that don’t normally fit into how academic research studies work. Scientists worked real-time to conduct, review and publish results of studies to scientifically ground the severity of the spill.

As contributors to the stewardship of the Gulf’s natural systems, USF researchers will continue to study the complexities of the Gulf ecosystem to provide a clearer understanding of the effects of the large number of anthropogenic stressors like climate change, overfishing, and energy exploration and extraction, but policy changes are the key to moving the needle forward.

While the C-IMAGE program is nearing its end, the relationships and collaborations will extend well beyond the June 30 end date. C-IMAGE will maintain its collaborative and international approaches to studying the Gulf of Mexico and beyond. Its data will live on at the USF Libraries, which received a portion of the funding to coordinate, catalogue, and make the data accessible to the public.

Photo: Courtesy of University of South Florida

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