The deep soft sediment Black Sea benthic community is dominated by cold seep habitats formed by the microbial breakdown of phytoplankton. The deep Black Sea benthic ecosystem is chemosynthetic with methanogenesis and the sulfate-driven anaerobic oxidation of methane acting as the primary metabolic pathways. Due to the depth and lack of metazoan life the deep Black Sea benthic ecosystem is generally regarded to be at low risk from anthropogenic impact and has little legislation pertaining directly to the preservation of the chemosynthetic habitats. The principal ecosystem services provided by the Black Sea include carbon sequestration and preservation of historical artefacts. Compared to other ecosystems, information on microbial biodiversity and ecosystem services in the deep Black Sea is lacking, and we highlight a need to plan and implement research programmes to address significant gaps and to enhance scientific understanding of this environment.
Deep-sea ecosystems and hydrothermal vents
With anthropogenic impacts rapidly advancing into deeper waters, there is growing interest in establishing deep-sea marine protected areas (MPAs) or reserves. Reserve design depends on estimates of connectivity and scales of dispersal for the taxa of interest. Deep-sea taxa are hypothesized to disperse greater distances than shallow-water taxa, which implies that reserves would need to be larger in size and networks could be more widely spaced; however, this paradigm has not been tested. We compiled population genetic studies of deep-sea fauna and estimated dispersal distances for 51 studies using a method based on isolation-by-distance slopes. Estimates of dispersal distance ranged from 0.24 km to 2028 km with a geometric mean of 33.2 km and differed in relation to taxonomic and life-history factors as well as several study parameters. Dispersal distances were generally greater for fishes than invertebrates with the Mollusca being the least dispersive sampled phylum. Species that are pelagic as adults were more dispersive than those with sessile or sedentary lifestyles. Benthic species from soft-substrate habitats were generally less dispersive than species from hard substrate, demersal or pelagic habitats. As expected, species with pelagic and/or feeding (planktotrophic) larvae were more dispersive than other larval types. Many of these comparisons were confounded by taxonomic or other life-history differences (e.g. fishes being more dispersive than invertebrates) making any simple interpretation difficult. Our results provide the first rough estimate of the range of dispersal distances in the deep sea and allow comparisons to shallow-water assemblages. Overall, dispersal distances were greater for deeper taxa, although the differences were not large (0.3–0.6 orders of magnitude between means), and imbalanced sampling of shallow and deep taxa complicates any simple interpretation. Our analyses suggest the scales of dispersal and connectivity for reserve design in the deep sea might be comparable to or slightly larger than those in shallow water. Deep-sea reserve design will need to consider the enormous variety of taxa, life histories, hydrodynamics, spatial configuration of habitats and patterns of species distributions. The many caveats of our analyses provide a strong impetus for substantial future efforts to assess connectivity of deep-sea species from a variety of habitats, taxonomic groups and depth zones.
Deep-sea coral and sponge habitats support the richest and most complex biological communities in the deep sea. NOAA’s Deep Sea Coral Research and Technology Program is providing the first systematic effort to discover and understand these ecosystems, combining science and information-sharing to help ocean managers conserve valuable habitats. The Program proudly announces its 2016 Report to Congress, highlighting exciting scientific research conducted over the past two-year period and historic conservation measures that have been proposed and enacted based on our Program’s results. The report spans the globe, from the remote Johnston Atoll in the middle of the Pacific Ocean to previously unknown coral gardens teeming with redfish only 25 miles off the coast of Maine. The Deep Sea Coral Research and Technology Program’s website also provides fieldwork reports and a searchable map in the nation’s most comprehensive online database of deep-sea corals and sponges. Armed with such information, the Mid-Atlantic Fishery Management Council is the most recent council to propose measures to protect deep-sea coral habitat from impacts of fishing. The Gulf of Maine also earns a spotlight because its deep-sea coral gardens are a major discovery – in addition to reading the report, take a virtual dive into this offshore habitat!
Deep-sea fisheries operate globally throughout the world's oceans, chiefly targeting stocks on the upper and mid-continental slope and offshore seamounts. Major commercial fisheries occur, or have occurred, for species such as orange roughy, oreos, cardinalfish, grenadiers and alfonsino. Few deep fisheries have, however, been sustainable, with most deep-sea stocks having undergone rapid and substantial declines. Fishing in the deep sea not only harvests target species but can also cause unintended environmental harm, mostly from operating heavy bottom trawls and, to a lesser extent, bottom longlines. Bottom trawling over hard seabed (common on seamounts) routinely removes most of the benthic fauna, resulting in declines in faunal biodiversity, cover and abundance. Functionally, these impacts translate into loss of biogenic habitat from potentially large areas. Recent studies on longline fisheries show that their impact is much less than from trawl gear, but can still be significant. Benthic taxa, especially the dominant mega-faunal components of deep-sea systems such as corals and sponges, can be highly vulnerable to fishing impacts. Some taxa have natural resilience due to their size, shape, and structure, and some can survive in natural refuges inaccessible to trawls. However, many deep-sea invertebrates are exceptionally long-lived and grow extremely slowly: these biological attributes mean that the recovery capacity of the benthos is highly limited and prolonged, predicted to take decades to centuries after fishing has ceased. The low tolerance and protracted recovery of many deep-sea benthic communities has implications for managing environmental performance of deep-sea fisheries, including that (i) expectations for recovery and restoration of impacted areas may be unrealistic in acceptable time frames, (ii) the high vulnerability of deep-sea fauna makes spatial management—that includes strong and consistent conservation closures—an important priority, and (iii) biodiversity conservation should be > balanced with options for open areas that support sustainable fisheries.
This report features an overview of the Program’s continuing regional three-year field studies. Accompanying the details of the fieldwork are stunning video footage and still photos of this unique marine life in all regions of the U.S.
Throughout the country, the Councils are increasingly engaged in developing methods to manage potential impacts of fisheries to deep-sea coral areas, recognizing these habitats’ role in the ecosystem. And yet, the geographic distribution of deep-sea corals and the full extent of their function as fish habitats have not been adequately studied, thus limiting some Councils’ ability to design management measures. In 2012 and 2013, the Program made considerable progress in filling these knowledge gaps by locating and characterizing deep-sea coral sites and submitting the findings to the Councils.
At $2.46 million in fiscal year 2012 and $2.37 million in fiscal year 2013, NOAA’s Deep Sea Coral Research and Technology Program is cost-effective in generating information of immediate use to Regional Fishery Management Councils and other resource managers in conserving structurally complex habitats formed by deep-sea corals.