Lisa A. Levin, Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, USA, is an invited speaker at S8: Climate change impacts on marine biodiversity and resilience.
One of the greatest challenges of the twenty first century is managing our deep ocean sustainably. The deep ocean covers over two thirds the surface of our planet and most of the habitable volume. It is vast, remote, difficult and expensive to access, and highly vulnerable to disturbance. The deep ocean provides key ecosystem services, sequestering carbon, cycling nutrients, buffering the ocean, and hosting a wealth of habitats, life forms, and genetic diversity needed for the planet to survive.
A growing human population and accompanying industrialization has caused rise of carbon dioxide in the atmosphere. The resulting atmospheric warming, plus significant carbon dioxide uptake by the ocean are changing conditions in the deep sea. Warming, acidification, and deoxygenation are all now documented in the deep ocean. Changes in food supply to the deep sea are also expected. In some places these stressors are interacting, with consequences for commercial living resources, biodiversity, trophic structure, and many ecosystem functions. Similar changes have occurred over geologic time, but modern changes are happening much faster. Highly vulnerable systems include the North Atlantic, where declines in aragonite saturation threaten deep-water coral reefs, upwelling margins where declining oxygen and pH are compressing habitat for demersal fishes, and polar regions where warming has altered crab distributions. By examining attributes of modern ecosystems along natural gradients we can learn about how different climate variables interact to affect communities. Analysis of macrofaunal diversity across margins reveals that different ocean basins exhibit different sensitivities to specific climate variables, with key roles for oxygen, temperature, and carbon dioxide.
At the same time that environmental conditions are changing in the deep ocean, rising human demand is creating an inexorable push to extract fish and shellfish, energy, raw materials and minerals from deep water. Advanced technology is both creating the demand for resources and driving our abilities to extract them from increasingly greater depths. This growing industrialization of our deep ocean creates multiple forms of disturbance, through physical disruption associated with bottom trawling of deep-sea fishes or minerals mining of resources such as manganese nodules, massive seafloor sulfides, cobalt crusts, and phosphorites. Accidental oil spills, as occurred with the Deepwater Horizon, introduce another form of disturbance. The capacity and time for ecosystems to recover from such disturbance (i.e. resilience) may be significantly affected by climate stressors such as warming, pH declines, oxygen loss, and reduced organic matter fluxes.
There is now a growing need to incorporate climate change considerations into comprehensive ecosystem-based management of the deep seafloor. Some areas of greatest projected environmental change coincide with those targeted for resource extraction. Creation of an appropriate deep-water monitoring network with engagement of multiple industrial sectors, in both international and national jurisdictions can be an important step. Maintaining the integrity of deep-ocean ecosystems, their diversity, functions and services will require a cross-disciplinary effort at the intersection of climate science, biodiversity, law, policy, and resource economics.
