Artificial Reefs

Old oil and gas platforms as skeletons for abundant coral reefs

There are more than 12,000 offshore oil and gas platforms worldwide. The big question is what to do with these enormous structures when the fossil fuels stop flowing. With curbing climate change rising up the international agenda, and with some questioning whether we have already passed peak oil, hastened by the coronavirus pandemic, the number of defunct rigs in the ocean is set to get bigger. Removing them from the water is incredibly expensive and labor-intensive. Allowing them to rust and fall into disrepair is an environmental risk that could seriously damage marine ecosystems. But there is one way in which these old rigs can be remarkably useful: the subsurface rig provides the ideal skeleton for coral reefs. Teeming with fish and other wildlife, offshore rigs can be turned into bountiful human-made marine habitats.

The practice of transforming rigs into reefs in the United States dates back almost 40 years. In 1984, the US Congress signed the National Fishing Enhancement Act which recognized the benefits artificial reefs provided and encouraged states to draw up plans to turn defunct rigs into reefs. The five coastal states on the Gulf of Mexico, Alabama, Florida, Louisiana, Mississippi and Texas, all have rigs-to-reefs programs and have converted more than 500 oil and gas platforms into artificial reefs. Reefing a platform is also an attractive proposition for oil and gas companies as it is significantly less expensive than total removal and is estimated to save the industry millions of dollars each year. Campaigners say it is a win-win situation as companies spend half of their decommissioning savings on the state’s artificial reef program. This money goes towards maintaining the platforms, marine conservation and education. Due to the abundant marine species living there, the platforms in the Gulf of Mexico have become hotspots for diving, snorkeling and recreational fishing. Offshore rigs are among the most productive fish habitats in the world, according to marine biologist Milton Love who has spent 20 years studying fish populations around oil and gas platforms in California. They provide marine wildlife with food, shelter from predators and a safe breeding ground.

Marine scientists Emily Hazelwood and Amber Sparks are on a mission to replicate this conservation success in other parts of the world. They founded the California-based organization Blue Latitudes in 2014 to raise awareness about the benefits of rigs and persuade oil companies and governments to designate them as permanent reefs. “We’re trying to help the general public understand that conservation isn’t always just about saving the whales,” says Sparks. “There are other ways we can look at complex ideas in our oceans, such as repurposing manmade structures like artificial reefs.” Hazelwood and Sparks have reefed rigs from Thailand to West Africa, preventing more than a dozen large marine ecosystems from being wiped out.

Chris Lowe, a marine biologist at California State University who has been tracking fish populations in southern California since 2008, says there is clear evidence that fish are drawn to the platforms. For one study, Lowe attached sensors to fish living by three oil platforms, before moving them to a natural reef located up to 18km (11 miles) away and monitoring their movements over two years. A quarter of the fish, across all species, quickly returned to their home oil platform, while others would migrate back during non-breeding seasons. “They had a higher likelihood of going back to their original platform than somewhere else. They really like their home platform. This showed us a lot about how the fish treat the platform as a habitat,” says Lowe.

However, precautions should be taken in advance of deploying artificial reefs due to the potential of attracting invasive species. Nonnative coral species have previously been shown to use human-made structures, including docks, pontoons, oil platforms, and shipwrecks, as stepping stones to expand their range, potentially upsetting surrounding ecosystems. But, considering the rapid decline in natural coral reefs, artificial reefs are usually still better than no reefs at all.

How one woman reconstructed a whole marine habitat

Lisa Carne managed to reconstruct a new natural coral reef, but it wasn’t easy. Her incredible effort shows how one woman can already make a huge positive impact on our environment. In 1995, she moved from California to Belize, and volunteered as a research assistant at Carrie Bow Cay, a Smithsonian field station. Belize is home to the second longest barrier reef in the world. At that time there were so many large, bright reddish-orange interlocking elkhorn corals that she could hardly swim through or around them. The reef was abundant in fish, corals, lobsters, crabs, sponges and sea turtles.
However, soon she witnessed the effects of the first coral bleaching event in Belize. Bleaching events leave the structure of corals intact, but strip it of the algae that live in an endosymbiotic relationship with the coral polyps. Some coral recover from such events as the algae returns, although many die. Unfortunately these bleaching events were not even the worst disaster to hit Laughing Bird Caye National Park off the coast of Belize. In 2001 Hurricane Iris swept across the coral reefs, smashed the corals into rubble and split the cay in two parts. The hurricane left the water murky and muddy, while rotting dead creatures washed ashore. With only a few surviving corals, the scene looked more like a graveyard. The hurricane was so powerful that it not only killed corals but uprooted their structure as well, making recovery even harder.

Carne immediately wanted to start replenishing the reefs by planting corals, but it took many years to convince any funders that her idea was viable. People argued, and still do, that without solving the problems that cause corals to die, putting them back on the reef made no sense. For five years after Hurricane Iris, the reef lay bare. There were few live corals, schools of fish or lobsters, and the seabed was covered in reef rubble and encrusting sponges. Then in 2006, the US listed Caribbean acroporid corals (the fastest growing type of branching coral in the Caribbean, and the main reef-building one) as endangered, and a local funder finally approved Carne’s proposal to try to restore the reef. She began with transplanting 19 elkhorn coral fragments from the main barrier reef around 19 miles (31km) away in a trial. “People were asking me why I’m going so far away for the corals,” says Carne. “They thought that these corals were common, like sand. But after two weeks of mapping, I found that they were not everywhere anymore.” In fact, she found that coral structure and cover had fallen to less than 6% of the national park area, from between 15 and 28% before the storm. Restoring a reef involves trial and error, often learning as you go. But Carne did a great job. The survival of her initial transplants in 2006 was high (more than 80% still alive today) so she continued to identify surviving corals and started reseeding the reefs with them.

Carne worked with other researchers on coral genetics, diseases, bleaching and spawning to seek out the best way to restore the reef. In 2009, Illiana Baums, professor of molecular ecology at Penn State University, advised on the appropriate distance to plant different individuals of each coral species apart to encourage spawning (sexual reproduction – which boost’s the reefs genetic diversity and resilience). Successful spawning events were later documented between 2014 and 2016. A breakthrough discovery in 2015 helped significant with restoring the reefs. When scientists first began to explore the idea of reef restoration, they thought that the larger the transplant, the higher the chance of survival. But marine biologist David Vaughan discovered that the opposite can also be true, the smaller the piece, the faster it grows. This so-called “micro-fragmentation” helped accelerating the restoration work. In the past, Carne’s team would trim corals into roughly 10cm pieces, grow them up in a coral nursery until they reached around 30cm and then plant them out in the reef. This new discovery allowed her team to accelerate growth rates in the nursery for certain coral species, and bypass nursery time for others completely.

Getting inspired and learn from good examples

Despite these steps forward, the task of replanting corals in over a hectare of shallow reef was too much for a research team of between two and four people. Once Carne’s mapping had revealed the extent of damage to the corals, the local people realized how scarce they had become. Fishermen and tour guides from nearby Placencia village were the first to notice the success of the transplanting efforts and they offered to help Carne with the planting.

In 2013, Carne registered a non-profit community-based organization in Belize called Fragments of Hope and two years later added a US branch. Fragments of Hope developed a coral restoration training course, endorsed by the Belize Fisheries Department, which has certified over 70 Belizeans to date, says Maya Trotz, a professor of civil and environmental engineering at the University of South Florida and a US board member of Fragments of Hope. The reef restoration work in Belize is unique because it focuses on shallow reefs, the kind that helps protect coasts, in a sparsely populated area. The restoration also supplements local people’s incomes from tourism and fishing with restoration jobs. “Fragments of Hope engages young people, and has created coloring books and puzzles about the reef, featuring artwork of a local artist,” says Trotz. “Over 2,500 have been distributed to date to schools across Belize.”

So far over 85,000 corals have been planted in the Laughing Bird Caye National Park. Long-term monitoring shows 89% survived after 14 years – much higher than typical survivorship after restoration. Overall, coral cover of the seafloor in the park increased from 6% to 50% between 2010 till 2017. Reports also suggest an upward trend in corals around Belize as a whole, rising from 11% of the seafloor surveyed in 2006 to 17% in 2018 through natural recovery. An amazing result for a project that started with the dedication of only one woman!

Techniques developed by Fragments of Hope have been successfully applied in Colombia, Jamaica and the Caribbean island of St Barts, as well as seven Marine Protected Areas and 10 other sites in Belize. Prior to Covid-19, Fragments of Hope organized exchanges, study visits and workshops to share experience across the Caribbean. People came to learn how to select an appropriate restoration site based on a long set of criteria, set up nurseries, trim corals and use cement for planting. The organization also shares its methods and experiences online.

The future of Carnes Reef

Though the project has seen substantial success, maintaining the reef is likely to be an uphill struggle. There are plans to build new cruise ports and coral bleaching events and heavy storms are becoming more extreme each year due to climate. If greenhouse gas emissions are not curbed globally, then few corals are predicted to survive in the “business as usual” scenario. The bleaching events in Belize have been getting progressively worse, Carne says. But if Carne had waited for zero emissions to begin her work, the reef today may not look much more alive than after Hurricane Iris hit. So while many scholars still criticize the idea of reef restoration in a world of warming oceans, the constant decline of reefs globally has led to projects in over 50 countries, though none yet approach the scale or longevity of the work in Belize. It is clear that the world needs more people like Lisa Carne and Mohammed Chowdhury, people really dedicated to protect and help our environment.

Another  interesting project that is still in its infancy uses Lego blocks to grow small bits of coral on. Singapore is home to a third of the world’s diversity of coral species, however issues like land reclamation and coastal development have caused these reefs to deplete over the decades. A group of scientists from the National University of Singapore are now trying to change this with the help of Lego blocks. According to the scientists they choose Lego blocks, because by connecting them it is easy to adjust the size of their surface according to the size needed for the coral to be stuck on to.