Deep-Sea Invertebrate Biodiversity

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Why study the Deep Sea? The deep-sea floor is the largest ecosystem on this planet: the average depth of the oceans is around 4.2 kilometres, comprising approximately 65% of the planet's surface. Nevertheless, we know much less about the deep-sea fauna than (for example) the rocky intertidal zone, which makes up a minuscule proportion of the global environment. Of more immediate importance, most of Australia's marine Exclusive Economic Zone is the deep sea (depths exceeding 200 metres) and yet this area is largely unexplored. Although the EEZ sea claim made by Australia is larger than any other country, this nation's basic biological research on the deep-sea floor is limited. My planned research will explore this region to discover how the deep sea can be of broader importance to Australia. This effort is just beginning, and substantial political and funding hurdles must be surmounted before detailed work in Australian waters can begin.

Australia SAR map

Why are there so many species in the deep sea? In the last 30 years, deep sea floor faunas have been discovered to have incredibly high species diversities, despite consisting of small numbers of individuals. Low population densities owe to the food-poor setting of the deep sea. I evaluate deep-sea faunas on a historical basis, where the processes of speciation, extinction and migration may control the observed levels of animal diversity, a regional pattern. My published work has concerned diversity and biogeography (Hessler, Wilson & Thistle, 1979; Hessler & Wilson, 1983), the processes of speciation (Wilson & Hessler, 1987), the impact of the disturbance on diversity (Thistle & Wilson, 1987, 1996), and studies of the distribution of species diversity (Poore &Wilson, 1993; Rex et al., 1993). Reports on NOAA (US National Oceanographic and Atmospheric Administration) funded research has been devoted to the quantitative description of community structure of crustaceans and polychaete worms from the Central Pacific (depths 4500-5100 meters). This research provides baseline data for understanding the impacts of deep-sea mining for manganese nodules.

Hessler Sandia Box Corer

Current research on deep-sea faunas. A 1992 paper by US colleagues J.F. Grassle and N. Maciolek estimates global diversity of the deep-sea benthos to be at least 10 million species based on extrapolations from work in the Atlantic Ocean; this result was amplified and defended by a letter to Nature (Poore & Wilson, 1993). A different extrapolation, using the rate of species change with distance, had surprising consequences: globally isopods are more diverse than polychaete worms, despite local diversities showing the opposite relationship. Isopoda could exceed 400,000 species on a global scale, given the high rates of change observed in the North Pacific. In 1996, a workshop at the NCEAS in Santa Barbara: "Deep-Sea Biodiversity: Pattern and Scale" considered the how processes affecting biodiversity varied at different geographic scales. Research with David Thistle, Florida State University, evaluated the impact of hydrodynamic stress on isopod faunas (Thistle & Wilson, 1996). Other collaborations with colleagues at the University of Hawaii and The Natural History Museum have evaluated polychaete diversity and its relationship to productivity in the deep sea. Historical influences on isopod diversity in the Atlantic ocean (Wilson, 1998) is a continuing interest. More recently, research has evaluated the diversity of isopods in the Gulf of Mexico at local and regional scales. An unusual fauna of deep-sea isopods on the outer shelf of the Arafura Sea has been discovered in 2005.

Manganese nodules in the central Pacific Ocean