Threats against Earth’s largest ecosystem are accelerating and several new studies underscore the urgency of protecting this largely unexplored environment.
Lisa Levin, a Scripps Institution of Oceanography at UC San Diego distinguished professor of biological oceanography, contributed her expertise on deep continental margins to the studies. Levin recently assumed leadership of Scripps’ Center for Marine Biodiversity and Conservation (CMBC) and, together with CMBC Associate Director Greg Rouse, hopes to add a deep sea emphasis to the center.
In the new studies, “Man and the last great wilderness: human impact on the deep sea,” and “Understanding Continental Margin Biodiversity: A New Imperative,” Levin and her colleagues expound upon the vast resources of the deep sea, which feature the most biodiversity on the planet. But they also cover a range of challenges facing Earth’s least studied environment. Because it is remote and out of sight, the deep seafloor has suffered as a dumping ground for human trash. It is now being heavily targeted for extraction of living, energy, and mineral resources. The warming of the oceans brought by climate change, along with emerging threats from ocean acidification and oxygen depletion, pose future hazards to marine life in the deep ocean.
The first paper, led by Eva Ramirez‐Llodra of the Institut de Ciències del Mar in Spain, was published in the Public Library of Science (PLoS) ONEjournal and resulted from a Census of Marine Life deep-sea synthesis project (SYNDEEP). A separate paper Levin wrote with Myriam Sibuet, to published in the Annual Reviews of Marine Science was developed from another Census of Marine Life program on continental margins (CoMARGE).
The deep sea covers 73 percent of the oceans across an estimated 326 million square kilometers (202 million square miles) and spans from approximately 200 meters (656 feet) to the extreme depths of trenches at nearly 11,000 meters (36,089 feet). The deep continental margins, Levin’s area of expertise, are only about 15 percent of this area but support the highest biodiversity and experience the greatest human impact on the deep sea.
“The challenges facing the deep sea are large and accelerating, providing a new imperative for the science community, industry and national and international organizations to work together to develop successful exploitation management and conservation of the deep-sea ecosystem,” the authors say in the PLoS ONE report.
Today’s threats from human encroachment on the deep sea include destructive bottom trawling and overfishing in areas once believed inaccessibly deep. There is mounting evidence that garbage from humans, including plastic debris, has accumulated on the deep seabed. Looming threats include exploitation of the deep’s energy and mineral resources, including deep-water drilling for oil and gas and new projects for mining precious metals from massive sulfides at hydrothermal vents, manganese nodules on the abyssal sea floor, and for extracting phosphorites from oxygen minimum zones.
But even while such challenges are on the rise, the authors predict that increases in atmospheric carbon dioxide and other impacts caused by climate change will eventually top all other threats influencing future deep-sea habitats.
“Climate change will affect the temperature, oxygen, and pH of the oceans at a global scale, in some cases amplifying the disturbance caused by other human-related activities such as fishing or mining,” the authors conclude.
The researchers call for new conservation measures to protect the deep ocean and its habitats.
In a third study published in the journal Marine Policy, Levin and several of her colleagues call for the implementation of marine reserves in the deep sea, much like reserves near coastlines protect sensitive habitats. The authors urge the development of conservation strategies that shelter areas of the deep—vents and seeps—that use chemical energy to create organic matter, rather than the more familiar photosynthesis in the upper ocean. Expansion of bottom trawling and oil and gas extraction activities on deep margins threatens methane seeps, while imminent metals mining threatens hydrothermal vents.
These relatively recently discovered ecosystems host a wealth of evolutionary novelty, but have only recently been considered for protection.
“For effective management of chemosynthetic ecosystems… the way forward must involve raised awareness of the value of biodiversity and careful assessment of marine policy options that promote resource sustainability,” the authors write.
Using chemosynthetic ecosystems as a framework, the authors say, “can set an important precedent for conservation priorities in the deep sea, within both national and international waters.”
Levin’s contributions to the studies involved assessment of continental margin diversity, threats, and responses. Her recent experiences in Africa during a Partnership for Observation of the Global Oceans visiting professorship at the National Marine Information and Research Centre in Namibia, Africa, have highlighted her awareness that many of the threats to the integrity of deep-water ecosystems involve countries where there is no deep-sea biological or policy expertise and no resources for deep-water research. Levin believes that “global capacity building” is essential to promote stewardship of deep-ocean biodiversity and resources.
The studies were supported by the A. P. Sloan Foundation, Fondation Total, International Seabed Authority, ChEss, CoMARGE, SYNDEEP, and CeDAMar Projects of the Census of Marine Life, the U.S. Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE), the U.S. National Marine Sanctuaries Program of NOAA, the U.S. National Science Foundation, IFREMER (Institut Français de Recherche pour l' Exploitation de la mer), InterRidge, and FCT/Lisbon (the Portuguese Foundation for Science and Technology).