USF researchers study oil spill's impact on the gulf

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It's been six years since an explosion on the Deepwater Horizon oil rig killed 11 workers and dumped more than 200 million of gallons of oil into the Gulf of Mexico.

Wednesday, a one-hour documentary, "Dispatches from the Gulf" will explore the clean up and research effort by a consortium international scientists. Narrated by Matt Damon, the documentary features a USF research team tracking the spill's affects on aquatic life.

From the decks of the Weatherbird II, USF Marine Science Professor Steven Murawski provides a first-hand look at the gulf's recovery.

"Early on we saw relatively high levels of contamination of a number of the species," said Murawski. "What we're finding is that the level of contamination has gone back, but it's very uneven."

For the last six years, Murawski and his team have collected blood and tissue samples from an array of fish throughout the gulf. One of the biggest challenges facing researchers is a complete lack of a baseline for contamination, making it impossible to tell what "normal" levels should be. Still, Murawski says his team has found a decline in contamination levels across many species.

Oil contamination in red snapper have dropped dramatically, but with an estimated 10-percent of sea floor in the spill area covered in oil, other sea creatures haven't been so lucky.

"Other species like tile fish that live in the bottom that is potentially contaminated, the level has not gone down and so trying to understand the reaction of some species to the lack of that large oil spill is fascinating to us and important to the long-term outcome of these species"

Murawski says contamination levels aren't high enough to jeopardize food safety, but could have a lasting effect on the gulf's fish population.

"Oil and other pollutants can create a lot of DNA damage, which reduces the fitness of animals and the next generation," explained Murawski.

DNA changes can disrupt reproduction, something that may explain the drop in red snapper population Murawski's team has observed. Murawski says many more years of research are needed in order to truly understand the long-term affects of the BP Deepwater Horizon spill. 

So far, researchers from USF's College of Marine Science say their six years of research has provided four important lessons:

1. The need for baseline data throughout the oceans to determine a disaster's effects
Under the Oil Pollution Act of 1990 (OPA), established after the 1989 Alaska Exxon Valdez spill, the responsible party is required to pay for damage. OPA90's Natural Resource Damage Assessment regulation requires quantifying damage and ecosystem restoration to pre-spill or "baseline" condition. With the Gulf vastly understudied before 2010, having a complete picture of the Gulf's "before" condition was impossible. Strong baseline could have provided an invaluable assessment and also could have even influenced how responders did risk assessments.

2. Oil sinks to the bottom
Marine "snow" is a term used to describe the particulate matter (dead and dying plankton) falling to the seafloor and is a pathway through which oil can be deposited on the seafloor. Crude oil is made of thousands of different arrangements of carbon that become more toxic after burning.  These toxic compounds can be trapped in marine snow and cover the seabed, harming marine life.

3. Dispersants may not as useful as once believed, particularly in the deep-sea
Over two million gallons of dispersants were released during relief efforts at the surface and at the well-head.  Dispersants break larger droplets into smaller ones for increased bacterial degradation. Studies have shown that dispersants did not stimulate bacterial growth and may have inhibited bacterial growth (full study here).

"Up to 10 percent of the sea floor in the area is covered with oil," said Dr. David Hollander of USF's College of Marine Science and chief scientist of C-IMAGE. "We want to relate what we see on the cores to the condition of the fish.  We will also distribute the cores to various scientific groups for research."

4: Prolonged oil toxicity in fish continues

Fish communities exposed to high levels of polycyclic aromatic hydrocarbons (PAHs) can severely impact fish health, behavior, and reproduction. Since 2010, USF researchers have studied the extent of exposure over time and evaluated fish muscle and liver tissue for PAH. Tissue samples from both shallow and deep water fish communities show that PAH concentrations in deep water fish increased 10-fold from 2010 to 2011, while the increase in PAH content in shallow water fish increased 20-fold.

Since 2011, the Gulf of Mexico Research Initiative (GoMRI) has provided $353 million in research dollars funding consortia - like C-IMAGE - and grants to study spill impacts on coastal, surface, and deep-sea environments, impacts on human health, and properties of oil droplets and dispersants in the ocean. In 2015, USF was awarded $20.2 million to continue C-IMAGE research.

To coincide with the sixth anniversary of the spill, a screening of the film "Dispatches From the Gulf," the story of the recovery efforts, will be broadcast via live stream on April 20:

It will also air on WEDU PBS locally at 8 p.m.