A global biogeographic classification of the mesopelagic zone
Sutton, Tracey T.; Clark, Malcolm R.; Dunn, Daniel C.; Halpin, Patrick N.; Rogers, Alex D.; Guinotte, John; Bograd, Steven J.; Angel, Martin V.; Perez, Jose Angel A.; Wishner, Karen; Haedrich, Richard L.; Lindsay, Dhugal J.; Drazen, Jeffrey C.; Vereshchaka, Alexander; Piatkowski, Uwe; Morato, Telmo; Błachowiak-Samołyk, Katarzyna; Robison, Bruce H.; Gjerde, Kristina M.; Pierrot-Bults, Annelies; Bernal, Patricio; Reygondeau, Gabriel; Heino, Mikko. (2017). A global biogeographic classification of the mesopelagic zone. Deep Sea Research Part I: Oceanographic Research Papers, 126, 85-102. 10.1016/j.dsr.2017.05.006.
- Bottom line: This paper is a critical first step toward a better understanding of the mesopelagic zone— the understudied but teeming region of the ocean between 200 and 1,000 meters deep. This zone may contain a quantity of fish equal to 100 times the annual catch of all fisheries, and according to The Economist, is proposed as a potentially massive source of aquaculture feed. This paper classifies the zone into 33 ecoregions as a starting point for efforts to manage any new human activity.
The new classification provides an important knowledge base for international conservation efforts, such as the Convention on Biological Diversity (CBD), which has set a goal of protecting 10 percent of the ocean by 2020. It can also support several related efforts to describe important ocean areas, including: 1) the description of “Ecologically or Biologically Significant Areas” under the CBD, 2) the identification of “Vulnerable Marine Ecosystems” by the intergovernmental organizations that manage deep-sea fishing on the High Seas, and, 3) the classification of “Particularly Sensitive Areas” by the International Maritime Organization, to restrict impacts from shipping.
- Background: The mesopelagic zone is one of the least understood environments on the planet. But it is also a biologically rich area that acts as a global “carbon pump” that transports organic material to the deep sea. Many experts agree that this process plays an important role in the global carbon cycle. Climate change, ocean acidification, and commercial fishing might disrupt that role, but the lack of information about the zone limits scientists’ ability to forecast impacts or to include the zone in conservation planning.
- Methods: Because relevant data are inconsistent and limited, the authors of the paper held a workshop to pull together their knowledge of the mesopelagic zone. One key tool in this process was an interactive map, which allowed experts from different disciplines to display disparate information in the same place. In addition, facilitators assisted with information exchange and led the diverse panel to consensus around a system for dividing the mesopelagic into “ecoregions”—areas that contain distinct groups of species. Ecoregions have also been used in similar efforts to classify surface waters and deep seabed areas.
- Findings: The panel defined 33 ecoregions in the mesopelagic (see map). It grouped these regions into four “biomes,” defined by the major forces shaping ecosystem structure, such as sea ice, seasonal winds, and the continents. According to the study, this system of classification can be useful to conservation in several ways. It provides context to assess the effects of climate change and other human impacts, improves understanding of ocean boundaries, and could fundamentally shift the international discussion of what to include in protected areas.
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