Abstract
The ChEss project of the Census of Marine Life (2002–2010) helped foster internationally-coordinated studies worldwide focusing on exploration for, and characterization of new deep-sea chemosynthetic ecosystem sites. This work has advanced our understanding of the nature and factors controlling the biogeography and biodiversity of these ecosystems in four geographic locations: the Atlantic Equatorial Belt (AEB), the New Zealand region, the Arctic and Antarctic and the SE Pacific off Chile. In the AEB, major discoveries include hydrothermal seeps on the Costa Rica margin, deepest vents found on the Mid-Cayman Rise and the hottest vents found on the Southern Mid-Atlantic Ridge. It was also shown that the major fracture zones on the MAR do not create barriers for the dispersal but may act as trans-Atlantic conduits for larvae. In New Zealand, investigations of a newly found large cold-seep area suggest that this region may be a new biogeographic province. In the Arctic, the newly discovered sites on the Mohns Ridge (71°N) showed extensive mats of sulfur-oxidisng bacteria, but only one gastropod potentially bears chemosynthetic symbionts, while cold seeps on the Haakon Mossby Mud Volcano (72°N) are dominated by siboglinid worms. In the Antarctic region, the first hydrothermal vents south of the Polar Front were located and biological results indicate that they may represent a new biogeographic province. The recent exploration of the South Pacific region has provided evidence for a sediment hosted hydrothermal source near a methane-rich cold-seep area. Based on our 8 years of investigations of deep-water chemosynthetic ecosystems worldwide, we suggest highest priorities for future research: (i) continued exploration of the deep-ocean ridge-crest; (ii) increased focus on anthropogenic impacts; (iii) concerted effort to coordinate a major investigation of the deep South Pacific Ocean – the largest contiguous habitat for life within Earth's biosphere, but also the world's least investigated deep-ocean basin.
Highlights
The recognition that lush communities of endemic fauna were associated with seafloor venting systems when the latter were first discovered in the late 1970s [1] represents one of the major highlights of the past Century across all fields of scientific research
Following the discoveries at the Galapagos vents in 1977, it was recognized that chemosynthetic ecosystems could be sustained in other chemically reducing seafloor environments, such as at cold seeps along passive and active margins [4] and in association with large organic falls such as wood falls [5], whale skeletons [6,7] and, following pioneering work by Gallardo et al [8], even in oxygen minimum zones
The span of the ChEss project (2002–2010) represents,25% of the entire history of chemosynthetic ecosystem research and a further 180 species previously unknown to science have been described during this time – i.e. the rapid rates of discovery established during the last quarter of the 20th Century have continued with no drop in rate throughout the first decade of the 21st Century – the Census of Marine Life decade
Summary
The recognition that lush communities of endemic fauna were associated with seafloor venting systems when the latter were first discovered in the late 1970s [1] represents one of the major highlights of the past Century across all fields of scientific research. Wherever there are chemically reduced compounds present (typically one or both of CH4 and H2S are most important) so, too, microbial activity is enhanced These microbiota may be present in freeliving form, in the deep water column or at the seafloor as microbial mats, within sediments or even within the fractures of crustal rocks, sub-seabed, or in symbiosis with larger multi-cellular organisms [10]. In all instances, these microbes mediate the transformation of chemical energy, to facilitate the development of densely populated ecosystems in which both faunal abundances and biomass are very much greater than is typical at the deep seafloor
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