A deep-sea project that documented species diversity of abyssal plains to increase understanding of the historical causes and ecological factors regulating biodiversity and global change.
Pedro Martinez Arbizu, Ph.D., Deutsches Zentrum fur Marine, Biodiversitatsforschung Forschungsinstitut Senckenberg, Germany
Craig Smith, Ph.D., Department of Oceanography, University of Hawaii, Honolulu, Hawaii, USA
Census of Diversity of Abyssal Marine Life (CeDAMar) was one of seven initial field projects of the Census of Marine Life (CoML). The goal of this project was to document actual species diversity of abyssal plans as a basis for global change research and to increase understanding of historical causes and actual ecological factors that regulate biodiversity. To achieve this, CeDAMar collected reliable data on the large-scale distribution of animals in one of the largest and most inaccessible environments on our planet.
The Deep Unknown
The deep sea harbors vast numbers of species, most of which are still unknown. Global estimates of marine species vary between 500,000 and 10 million. Since there is no inventory of the fauna of even a single ocean basin, extrapolation of total species numbers of the global abyssal fauna is impossible or at best very speculative. CeDAMar will focused on benthic, epibenthic and hyperbenthic organisms because of their high species-richness.
The study of the deep sea offers a number of advantages. Environmental factors appear to be more homogenous in the deep sea than in many other environments and are easier to measure due to the relative uniformity of large areas. Anthropogenic effects are reduced, and communities are for the most part found in their natural state. Geological information on kinds and age of the sediments in the deep sea is available from past and ongoing projects.
CeDAMar developed standardized protocols for surveying marine organisms in abyssal marine sediments, including reliable collecting devices in order to avoid damage to fragile deep-sea animals. Such standard protocols enabled results from different ocean basins to be comparable today as well as in the future. CeDAMar also contributed to the development and testing of new, more efficient collecting techniques.
Samples were collected along approximately 1000 km long transects. To exclude small-scale variations which could influence biodiversity estimations, larger areas were sampled with an epibenthic sledge and repeated box corer (or new devices with the same function) and multicorer hauls. Underwater cameras were used to document the morphology of the ocean bed, the effects of bioturbation and the abundance of microfauna. The collected material was analyzed with modern systematic methods.
The ventral side of a starfish, Asteroide, collected in the Southern
Ocean with its gut full of sediment that shines through the body
wall, giving it its bluish color. Photo by Brigitte Ebbe.
CeDAMar described in detail the species found during its expeditions and wrote keys in order to ensure reliable identification of specimens collected during subsequent expeditions by other teams. Their intent was to describe the change in species composition along transects and to compare different ocean regions to learn more about the composition of local communities, large-scale distribution of a single species, and the influence of sediment parameters and primary production on the diversity of benthic communities. Species data were also related to the history and age of the basins, present and hypothesized past bottom currents, and paleoclimatic data. Taxonomists studied the distribution of their groups to explain the geographic and phylogenetic origin of deep-sea species. A synthesis of all data increased understanding of the history of deep-sea fauna and its present diversity and dependence on environmental parameters, such as the effects of currents, seamounts, trenches, geographic isolation and other ecological factors. Centers of high biodiversity were identified, which will be useful for planning both commercial and conservation efforts. Finally, CeDAMar's estimation of the number of species living in the deep sea contributed to the estimation of global species diversity.
Climatic change will reach the deep sea considerably later than other marine environments, but the effects of bottom temperature and the productivity of the surface waters on the environmentally sensitive fauna that live there are expected to be dramatic. CeDAMar provided a foundation of knowledge about faunal composition, seasonal variations, and the influence of productivity in the deep sea on which any future study of the effects of global warming or human interference can rely upon. The task of CeDAMar required an enormous scientific effort that was successful because all available specialists joined forces in a single coordinated endeavor.
Visit the Census of Diversity of Abyssal Marine Life  website.