Mesophotic and Deep Benthic Communities Restoration

Vital seafloor habitats were damaged by the 2010 Deepwater Horizon oil spill. NOAA and partners are building a network of experts and resources to restore this underexplored area in the Gulf of Mexico.

Southeast

Mesophotic and Deep Benthic Communities: Where the Light Fades

The sun is powerful, but its intensity dwindles as it passes through the depths of the sea. Yet even the ocean’s dim middle reaches—the “mesophotic zone”—and its deepest, sunlight-free areas—the deep sea—host an abundance of life.

A colorful array of corals and crinoids on an underwater bank — Mesophotic corals and crinoids on Bright Bank, near the Flower Garden Banks National Marine Sanctuary. Credit: Marine Applied Research and Exploration, NOAA

In the dim mesophotic zone, seafloor communities include deep-sea corals and animals such as fish, sea anemones, sponges, and sea cucumbers. Sunlight-free deep benthic communities also host corals and other forms of life such as sea stars, sea urchins, fish, and crabs. These organisms colonize rocky outcroppings on the seafloor. Some deep-sea corals, the corals found in both mesophotic and deep benthic areas, are slow growing and can live for more than 1,000 years.

In the Gulf of Mexico, mesophotic and deep benthic communities are scattered across vast areas of the ocean floor. These communities are found at depths from 100 feet to some of the Gulf’s deepest points, around 13,000 feet. While seemingly isolated, they are composed of foundational species that contribute to an interconnected food web throughout the region. For example, mesophotic and deep benthic communities harbor fish and invertebrate eggs and larvae. As they mature, some of these organisms travel to other parts of the ocean to feed and reproduce.

How Are We Restoring Deep-Sea Habitats?

NOAA is working with a multidisciplinary group of partners to plan and implement the mesophotic and deep benthic communities restoration projects. NOAA collaborates with scientists and resource managers in the Department of the Interior, including the U.S. Geological Survey. The growing network of partners includes academic and research institutions, aquariums and educational institutions, and governmental and non-governmental organizations.

The robotic arm of a remotely operated vehicle collecting a small white branching coral fragment from the larger coral colony on the seafloor next to it — Sample collection of the sea fan Muricea pendula using a remotely operated vehicle in the Gulf of Mexico aboard the vessel R/V Point Sur, October 2022. Credit: NOAA

Restoring deep-sea habitats is a challenging task. In addition to a lack of information about the species that make up the communities that form these habitats, there is limited restoration practice and technical experience in the United States and internationally. To meet these challenges, the Open Ocean Trustee Implementation Group selected four long-term projects in their second restoration plan (PDF, 493 pages).

Through these projects, teams of experts and resource managers are advancing our understanding of deep-sea habitats. They are also enhancing the information available to inform restoration in areas impacted by the spill. These efforts are also providing information to support management, protection, and restoration of resources across the entire Gulf of Mexico.

The projects began in 2020 and were cumulatively funded at about $126 million. They included:

1- to 2-year planning and design stage
5-year field- and lab-based implementation stage
1 year for final evaluation and reporting

Explore the Projects

Mapping, Ground-Truthing, and Predictive Habitat Modeling

Restoring, managing, and protecting these communities across the Gulf of Mexico is challenging. The full geographic area where the habitats are found and the total number of those communities, is unknown, particularly in deeper water. To fill these data gaps, this project will deliver high-resolution seafloor bathymetry maps, and images and video from visual surveys of mesophotic and deep benthic habitats. The project team will use this information to refine predictive models, which are used to generate maps of where species are likely to occur.

Learn more about the project

Four people wearing hard hats and life jackets standing on the edge of a research vessel. They are pulling a cylinder-shaped autonomous underwater vehicle out of the ocean with a winch and lines. — Recovery of an autonomous underwater vehicle (AUV) aboard the NOAA Ship Pisces in July 2022. The AUV was used to conduct high-resolution seafloor mapping in the Gulf of Mexico. Credit: NOAA

Habitat Assessment and Evaluation

The life histories, diversity, and population structures of the species that make up mesophotic and deep benthic communities in the Gulf of Mexico are not well understood. The goal of this project is to fill those knowledge gaps, determine baseline conditions, and identify defining characteristics of deep-sea communities. These include the types of species, biodiversity, and surrounding environmental conditions at both impacted and unimpacted sites. The team will collect multidisciplinary data and conduct assessment surveys to examine the deep-sea environment and organisms that live in these habitats. This data includes the ways these environments and organisms change, naturally or through restoration actions, in space and over time.

Learn more about the project

Coral Propagation Technique Development

The most direct way to restore mesophotic and deep benthic habitat is to facilitate new growth of coral species that were impacted by the oil spill. In this pilot project, a team will develop and test restoration techniques in the lab and the field. These techniques can be scaled up to expand and improve the health of these habitats across the Gulf of Mexico. The team will test substrates (materials corals can grow on) and coral transplantation techniques in the field, in areas where mesophotic and deep-sea coral habitats naturally occur. The team will also develop coral cultivation techniques in the lab.

Learn more about the project

Pieces of branching red corals affixed to plates in a laboratory tank — Fragments of the sea fan Swiftia exserta collected in the Gulf of Mexico in June 2022. The fragments are arranged in photogrammetry carousels for growth monitoring at the NOAA Hollings Marine Laboratory. Credit: NOAA

Active Management and Protection

This project will support the protection and management of mesophotic and deep benthic communities through education, outreach, engagement, and direct threat reduction. Project activities include engagement with natural resource managers, education and outreach programs targeting resource users and the public to increase awareness of these habitats, and reducing threats to MDBC habitat through activities such as mooring buoy installations, removal of invasive species such as lionfish, documentation and removal of marine debris and derelict fishing gear, and assessing and remediating risks associated with leaking and abandoned oil and gas infrastructure.

Learn more about the project.

Why We are Restoring Habitat: The Deepwater Horizon Oil Spill

On April 20, 2010, an explosion occurred on BP’s Deepwater Horizon offshore drilling platform in the Gulf of Mexico. This event killed 11 workers and injured another 17 people. When the rig sank, it started a catastrophic oil spill from the well at the seafloor. Before a crew finally capped the well 3 months later, roughly 134 million gallons of oil had spilled into the Gulf—enough to fill roughly 200 Olympic-sized swimming pools.

The largest offshore oil spill in U.S. history, the Deepwater Horizon incident dealt a heavy blow to the Gulf of Mexico’s natural resources and economy. It also required an unprecedented response effort. Teams worked to collect, disperse, and remove the oil to reduce harm to people and the ecosystem, which provides many services for the region.

The Deepwater Horizon oil spill harmed more than 770 square miles of deep-sea habitat (an area about half the size of Rhode Island). This includes areas surrounding the wellhead and parts of the Pinnacles mesophotic reef complex, located at the edge of the continental shelf in the northern Gulf of Mexico. Among other impacts, seafloor-dwelling organisms suffered from oil toxicity and were smothered with drilling sediments. The oil contaminated seafloor habitat and the marine food web.

Planning for Restoration

State and federal natural resource agencies conducted a Natural Resource Damage Assessment of the impacts of the Deepwater Horizon oil spill. They assessed injuries, quantifying the unprecedented harm to natural resources and lost public services. They used the assessment to develop a comprehensive, science-based, restoration plan for the Gulf of Mexico. In 2016, BP agreed to pay a total of $8.1 billion in natural resource damages, and up to an additional $700 million for adaptive management. This strategy addresses impacts to natural resources that are presently unknown but which may come to light in the future.

NOAA, other federal agencies, and other partners have made much progress restoring the Gulf of Mexico since the spill.

Two people putting red coral samples into a plastic tub filled with water aboard a research vessel — Aquarists retrieve coral samples collected from a mesophotic reef by a remotely operated vehicle. This work took place in July 2022 during a cruise to study coral spawning in and around Flower Garden Banks National Marine Sanctuary. Credit: Kelly Martin/NOAA

To conduct restoration work effectively, the agencies formed subgroups, known as implementation groups. The Open Ocean Trustee Implementation Group is composed of the federal trustees—NOAA, the U.S. Department of Agriculture, the U.S. Department of the Interior, and the U.S. Environmental Protection Agency. This group works together to restore key species impacted by the oil spill, including: