First insights into the biodiversity and biogeography of the Southern Ocean deep sea

Abstract

Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa. The deeper parts of the Southern Ocean exhibit some unique environmental features, including a very deep continental shelf and a weakly stratified water column, and are the source for much of the deep water in the world ocean. These features suggest that deep-sea faunas around the Antarctic may be related both to adjacent shelf communities and to those in other oceans. Unlike shallow-water Antarctic benthic communities, however, little is known about life in this vast deep-sea region. Here, we report new data from recent sampling expeditions in the deep Weddell Sea and adjacent areas (748-6,348 m water depth) that reveal high levels of new biodiversity; for example, 674 isopods species, of which 585 were new to science. Bathymetric and biogeographic trends varied between taxa. In groups such as the isopods and polychaetes, slope assemblages included species that have invaded from the shelf. In other taxa, the shelf and slope assemblages were more distinct. Abyssal faunas tended to have stronger links to other oceans, particularly the Atlantic, but mainly in taxa with good dispersal capabilities, such as the Foraminifera. The isopods, ostracods and nematodes, which are poor dispersers, include many species currently known only from the Southern Ocean. Our findings challenge suggestions that deep-sea diversity is depressed in the Southern Ocean and provide a basis for exploring the evolutionary significance of the varied biogeographic patterns observed in this remote environment.

Multiple origins of deep-sea Asellota (Crustacea: Isopoda) from shallow waters revealed by molecular data

“…In most abyssal benthic samples, asellote isopods represent the dominating crustacean taxon and often account for a large fraction of all species present in an area (Sanders et al 1963;Sanders & Hessler 1969;Brandt et al 2007). These isopods are mostly very small benthic or epibenthic blind animals with a body size of a few millimetres, which are difficult to identify at the species level.…”

“…Gage & Tyler 1991;Herring 2002). In particular, the deep-sea soft-sediment environment hosts a diverse but highly endemic benthic fauna of, in most cases, unknown origin and age (Hessler & Sanders 1967;Menzies et al 1973;Brandt et al 2007).…”

Temporal latitudinal-gradient dynamics and tropical instability of deep-sea species diversity

“…Surprisingly little attention has been given to understanding low-latitude deepsea diversity and the temporal dynamics of the LSDGs. Although pollen records suggest a persistent latitudinal diversity gradient existed in terrestrial ecosystems over the last 13,000 years (17, 18), we know of no studies of species-level temporal dynamics of LSDGs based on fossil assemblages from marine environments, despite the sensitivity of marine ecosystems to climatic change (12,13,(19)(20)(21)(22)(23)(24).The Ostracoda (Crustacea) are an important component of the deep-sea benthos (25)(26)(27), and the only commonly fossilized metazoan group in deep-sea sediments (12,13,28). Their various habitats and ecological preferences represent a wide range of deep-sea benthic niches, and their fossil record is considered representative of the benthic community (12,13,28).…”

Estructurada de las comunidades bontónicas en tres sitios de las islas Shetland del sur (Antártida): Patrones de diversidad, composición y tamaños corporales

“…Dado su aislamiento, estas comunidades son sumamente particulares, caracterizándose por presentar altos niveles de endemismo, crecimiento lento, longevidad, madurez tardía y gigantismo, así como radiaciones adaptativas que han generado considerable biodiversidad en algunos grupos y taxones (Brandt et al 2007).…”