Texas scientists restore Gulf coral years after BP oil spill

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In the early morning, at a lab not too far from the Galveston coast, Shannon Ainsworth is collecting hundreds of tiny, floating brown eggs from a tank of deep-sea coral. She sticks a little plastic dropper into the water, sucks up an egg or two, and deposits them into a beaker on top of the tank. Then she repeats.

The process goes on for several hours until all the eggs in the tank are gone. But that’s just the beginning. The hope is that the eggs will fertilize and then grow—albeit incredibly slowly—into new coral.

Already, some of the tanks in the lab have baby corals, which are growing on tiny rock tiles next to the older, adult coral. The new coral is two years old and the size of a half-fingernail.

“That girl over there,” Ainsworth said, gesturing to a big coral in the back of the tank. “It released over 2,000 eggs yesterday. Then we collect them all by hand.”

Ainsworth has been a coral aquarist for almost a year at the Southeast Fisheries Science Center Wet Lab in Galveston with the National Oceanic and Atmospheric Administration — a scientific and regulatory agency focused on monitoring weather and oceanic activities. There, she works on the Mesophotic and Deep Benthic Communities — Coral Propagation Technique Development project — which is the long, scientific name for restoring ocean habitats below 164 feet by studying deep-sea coral reproduction.

The work is only one piece of a much larger restoration project, stemming from the 2010 Deepwater Horizon oil spill off the coast of Louisiana, which resulted in the discharge of 134 million gallons of oil into the Gulf and the environmental destruction of miles of habitat. About two-fifths of the oil sank to the bottom of the Gulf, contaminating an estimated 770 square miles — an area a bit bigger than the City of Houston — including deep-sea coral communities.

Since 2022, the scientists with the deep-sea coral project in Galveston are studying ways to restore the 12 different coral species from the spill’s damage. For Ainsworth, most days this means collecting eggs, feeding coral, and examining how different species are growing and adapting. Depending on the success of any given technique in the lab, the team could then apply the same technique to the oil spill site.

The work has another benefit too, according to Sasha Francis, Gulf restoration education and outreach manager for the project. Unlike the more commonly-known shallow water coral, deep-sea coral is a big mystery in the oceanic world.

“The really impressive part of this is it really hasn’t been done before for these species of corals,” Francis said. “How often do they like to eat? Will they propagate or reproduce in these environments? So the coral labs, along with partner labs, are working together to really have a better understanding of the life cycle.”

Deepwater Damage

When the BP oil rig exploded in the Gulf of Mexico, it killed 11 people, injured 17 and spewed oil from its wellhead on the ocean floor for four months before being capped. In that time, the surface contamination totaled 43,300 square miles — or about the size of the State of Virginia — damaging the entire ecosystem for the northern portion of the Gulf.

For deep-sea coral, oil contamination can have a variety of impacts, including poisoning the species or completely covering it, causing it to starve or suffocate, including completely smothering the corals or from the toxic impacts from the oil.

“If the oil is in a heavy enough volume, then yes, it will just suffocate the coral, but the oil can also produce toxic responses, physiological responses, just from chemical exposure,” said Kristopher Benson, marine habitat resource specialist for the NOAA Fisheries Restoration Center. “Deep-sea coral have tentacles that can manually bring in particles to eat, but if those particles are covered in oil, they can’t access their food.”

Deep-sea coral feeds differently than their shallow-water cousins. Coral in the shallow parts of the ocean use a process called zooxanthellae, in which algae living on the coral’s tissue will absorb sunlight to make sugar that passes through to the coral. Deep-sea coral does not get enough sunlight for this process and must feed entirely using its tentacles.

In many cases, the contamination from the spill caused the tissue to slowly slough off the skeleton of the coral colonies, sometimes killing a few individual coral polyps or branches, and in some cases killing whole colonies.

“Our teams are continuing to document if there is recovery over time. These things tend to work on a much slower time scale than the surface and so a lot of the effects we might expect to see are going to take potentially decades to document,” Benson said. “Do we see total die-off and loss? We’ve seen some of that. Or do we see some recovery? We’ve also seen that.”

The team uses deep-sea divers and machines to track down species of coral in the northern part of the Gulf — in areas both impacted and not impacted by the spill. Firstly, the divers will cut a section of healthy coral to bring to the lab for study. The coral can keep growing even after being severed from its base. Then depending on which techniques are working in the lab, the divers will head back into the ocean to incorporate those techniques in the wild.

However, because deep-sea coral has been so understudied, the process takes longer. Typically, during restoration, scientists will analyze healthy habitats to better understand the baseline. In this case, the project scientists don’t really know what they are working toward, said Kelly Martin, one of the NOAA restoration project managers.

Only Flower Garden Banks National Marine Sanctuary — a 160-mile protected habitat for coral and other marine life — has some long-term data on healthy habitats.

“We are working and monitoring simultaneously in both impacted and non-impacted areas,” Martin said. “But we won’t know what success looks like with restoration until we know what a healthy habitat is supposed to look like. It’s not useful to just focus on the impacted area.”

Still, the team has to take precautions in contaminated areas as well.

“We don’t want to put healthy coral in if the contamination is still present,” Benson said. “It’ll just be exposed to more contamination and then suffer and die. That doesn’t help.”

Restoration in progress

Six years after BP capped the oil rig, the company agreed to pay more than $20 billion in civil and criminal penalties with a large amount guaranteed for Gulf restorations. The deep-sea coral restoration project is funded by $126 million of that settlement.

The project is split into four smaller projects, including the coral lab. There are only two other federally-run labs in the United States that do this kind of work. One in Gainesville, Florida and one in Charleston, South Carolina.

So far, the team has tested eight different techniques to propagate — or breed — the coral population. In one case, the team sets up tiny rock tiles for the baby coral to grow on, as research has shown that they like a stable surface. Depending on how the rock tile babies do in the lab, the team will put rock tiles out in the ocean for the babies to grow there, too.

It’s exciting for the team anytime a baby coral starts to grow. After spawning, Ben Higgins, research fishery biologist at NOAA, will put the coral eggs in small containers and wait several days before adding a little tile. The coral eggs will turn into a pear-shaped larva, spin around the container, and then grow longer and more rod-like before looking for a place to settle down.

“I have to go through these containers every two days, I do water changes, I count larvae, I count eggs, I do a little prayer,” Higgins said. “You got to get that little (settling) tile in there and just the right way so they don’t just stick the plastic container instead. If you wait too long to put in the tile, the coral dies. If you put the tile in too soon, that could be a problem.”

It’s a lot of work, Higgins said, but the team had a major success recently. For the first time in a lab or in the wild, the team documented a tan deep-sea coral species spawning. It had never been seen before. They had called the other labs, excited by the development.

“It felt like we were actually making strides,” Ainsworth said. “Like we wouldn’t have seen this if we hadn’t gotten the funding and we hadn’t started this project.”

This project is scheduled to go until 2028, but as the settlement money continues annually, the team expects to develop a follow-up to the original restoration plan — meaning the team’s work won’t end until the late 2030s or into 2040. There could be a lot to learn in that time, not just about deep-sea coral restoration, but the deep-sea coral in general.

“Right now, this is almost a beta phase where we try a bunch of different things, see what’s most effective,” Martin said. “Then in the next phase, we’ll pick one or two that are most effective and scale that up. It takes a while, but we’re excited to see how it turns out.”