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Ramirez-Llodra E.,CSIC - Institute of Marine Sciences | Brandt A.,Biocentrum Grindel and Zoological Museum | Danovaro R.,Marche Polytechnic University | De Mol B.,University of Barcelona | And 12 more authors.
Biogeosciences | Year: 2010

The deep sea, the largest biome on Earth, has a series of characteristics that make this environment both distinct from other marine and land ecosystems and unique for the entire planet. This review describes these patterns and processes, from geological settings to biological processes, biodiversity and biogeographical patterns. It concludes with a brief discussion of current threats from anthropogenic activities to deep-sea habitats and their fauna. Investigations of deep-sea habitats and their fauna began in the late 19th century. In the intervening years, technological developments and stimulating discoveries have promoted deep-sea research and changed our way of understanding life on the planet. Nevertheless, the deep sea is still mostly unknown and current discovery rates of both habitats and species remain high. The geological, physical and geochemical settings of the deep-sea floor and the water column form a series of different habitats with unique characteristics that support specific faunal communities. Since 1840, 28 new habitats/ecosystems have been discovered from the shelf break to the deep trenches and discoveries of new habitats are still happening in the early 21st century. However, for most of these habitats the global area covered is unknown or has been only very roughly estimated; an even smaller - indeed, minimal - proportion has actually been sampled and investigated. We currently perceive most of the deep-sea ecosystems as heterotrophic, depending ultimately on the flux on organic matter produced in the overlying surface ocean through photosynthesis. The resulting strong food limitation thus shapes deep-sea biota and communities, with exceptions only in reducing ecosystems such as inter alia hydrothermal vents or cold seeps. Here, chemoautolithotrophic bacteria play the role of primary producers fuelled by chemical energy sources rather than sunlight. Other ecosystems, such as seamounts, canyons or cold-water corals have an increased productivity through specific physical processes, such as topographic modification of currents and enhanced transport of particles and detrital matter. Because of its unique abiotic attributes, the deep sea hosts a specialized fauna. Although there are no phyla unique to deep waters, at lower taxonomic levels the composition of the fauna is distinct from that found in the upper ocean. Amongst other characteristic patterns, deep-sea species may exhibit either gigantism or dwarfism, related to the decrease in food availability with depth. Food limitation on the seafloor and water column is also reflected in the trophic structure of heterotrophic deep-sea communities, which are adapted to low energy availability. In most of these heterotrophic habitats, the dominant megafauna is composed of detritivores, while filter feeders are abundant in habitats with hard substrata (e.g. mid-ocean ridges, seamounts, canyon walls and coral reefs). Chemoautotrophy through symbiotic relationships is dominant in reducing habitats. Deep-sea biodiversity is among of the highest on the planet, mainly composed of macro and meiofauna, with high evenness. This is true for most of the continental margins and abyssal plains with hot spots of diversity such as seamounts or cold-water corals. However, in some ecosystems with particularly "extreme" physicochemical processes (e.g. hydrothermal vents), biodiversity is low but abundance and biomass are high and the communities are dominated by a few species. Two large-scale diversity patterns have been discussed for deep-sea benthic communities. First, a unimodal relationship between diversity and depth is observed, with a peak at intermediate depths (2000-3000 m), although this is not universal and particular abiotic processes can modify the trend. Secondly, a poleward trend of decreasing diversity has been discussed, but this remains controversial and studies with larger and more robust data sets are needed. Because of the paucity in our knowledge of habitat coverage and species composition, biogeographic studies are mostly based on regional data or on specific taxonomic groups. Recently, global biogeographic provinces for the pelagic and benthic deep ocean have been described, using environmental and, where data were available, taxonomic information. This classification described 30 pelagic provinces and 38 benthic provinces divided into 4 depth ranges, as well as 10 hydrothermal vent provinces. One of the major issues faced by deep-sea biodiversity and biogeographical studies is related to the high number of species new to science that are collected regularly, together with the slow description rates for these new species. Taxonomic coordination at the global scale is particularly difficult, but is essential if we are to analyse large diversity and biogeographic trends. Because of their remoteness, anthropogenic impacts on deep-sea ecosystems have not been addressed very thoroughly until recently. The depletion of biological and mineral resources on land and in shallow waters, coupled with technological developments, are promoting the increased interest in services provided by deep-water resources. Although often largely unknown, evidence for the effects of human activities in deep-water ecosystems - such as deep-sea mining, hydrocarbon exploration and exploitation, fishing, dumping and littering - is already accumulating. Because of our limited knowledge of deep-sea biodiversity and ecosystem functioning and because of the specific life-history adaptations of many deep-sea species (e.g. slow growth and delayed maturity), it is essential that the scientific community works closely with industry, conservation organisations and policy makers to develop robust and efficient conservation and management options. © Author(s) 2010.

Muhlenhardt-Siegel U.,Deutsches Zentrum fur marine Biodiversitatsforschung
Zootaxa | Year: 2011

The leuconid cumaceans of the Antarctic deep-sea basins are listed. Ten new leuconid species are described: eight species in the genus Leucon: L. (Crymoleucon) parantarcticus, L. (C.) weddellensis, L. (C.) longirhinus, L. (C.) grandidentatus, L. (Leucon) quattuormulierum, L. (L.) andeep, L. (Macrauloleucon) weigmanni and L. (M.) complexus. One new species is described for the genus Eudorella: E. flokkeri. The genus Bytholeucon was discovered for the first time in Antarctic waters with a new species, B. hartmannorum. © 2011 Magnolia Press .

Muhlenhardt-Siegel U.,Deutsches Zentrum fur marine Biodiversitatsforschung
Marine Biodiversity | Year: 2011

The Leuconidae of the deep eastern Atlantic obtained during the German expedition Diva II and the French expeditions Zaiango and Biozaire 1 to 3 were analysed. Thirteen more or less frequently occuring leuconid species were found, including ten new deep-sea species from the Cape, Angola and Guinea Basin. The most speciose (ten species) genus is Leucon with three species in the subgenus Crymoleucon, four species in the subgenus Epileucon, one species in the subgenus Leucon and two species in the subgenus Makrauloleucon. A new genus-Afroleucon-is described, having penial lobes and only one pair of pleopods in males. One species each belongs to the genera Bytholeucon and Eudorella. Only three species, Leucon (Makrauloleucon) brigittehilbigae Mühlenhardt-Siegel 2005b, Leucon (Leucon) homorhynchus Bishop 1981a and Leucon (Epileucon) cf tenuirostris form A Bishop 1981b, were already known. The new species are: Afroleucon enigmatica n. g., Leucon (Crymoleucon) lufupa, L. (Crymoleucon) kafunta, L. (Crymoleucon) galeronae, L. (Epileucon) kapinga, Leucon (Epileucon) paraspiniventris, L. (Epileucon) paralongirostris, Leucon (Makrauloleucon) moritzi, Eudorella angolensis, and Bytholeucon kaingo. © 2010 Senckenberg, Gesellschaft für Naturforschung and Springer.

Muhlenhardt-Siegel U.,Deutsches Zentrum fur Marine Biodiversitatsforschung
Marine Biodiversity | Year: 2012

The Nannastacidae of the deep south-eastern Atlantic obtained during the German expedition DIVA II and the French expeditions ZAIANGO and BIOZAIRE 1 to 3 were analysed. Thirteen more frequently occurring nannastacid species were found, including seven new deep-sea species and a new genus from the Cape, Angola and Guinea Basins: Campylaspides armatus sp. n., Bathypicrocuma ifrmer gen. and sp. n., Styloptocuma dentatum sp. n., S. cuspidatum sp. n., S. paucidentatum sp. n., Styloptocuma enigma sp. n., and Thalycrocuma barbatulum sp. n. The species Procampylaspis lucida and Campylaspis serratocarinata had already been described for the Angola Basin but remained in open nomenclature. After their rediscovery, they were now named. The species Styloptocuma minimum, S. pleonserratum and Platycuma lineata were already known from the Angola Basin and were now rediscovered in the Cape and Guinea Basins. The species Atlantocuma tenuis was already known as widespread in the Atlantic. The most speciose genus in the family Nannastacidae described here is Styloptocuma with six species, four of which are new. © 2011 Senckenberg, Gesellschaft für Naturforschung and Springer.

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