ChEssBase: a central source of online information for species from deep-water chemosynthetic ecosystems. Eva Ramirez-Llodra, Maria Blanco National Oceanography Centre Southampton, European Way, SO14 3ZH Southampton, UK email@example.com ChEssBase is a dynamic relational database available online since early 2005 (http://www.soc.soton.ac.uk/chess/database/database.html). The aim of ChEssBase is to provide taxonomical, biological, ecological and distributional data for all species described from deep-water chemosynthetic ecosystems, as well as information on available samples, images, bibliography and information on the habitats. These habitats include hydrothermal vents, cold seeps, whale falls, sunken wood and areas of minimum oxygen that intersect with the continental margin or seamounts. Since the discovery of hydrothermal vents in 1977 and of cold seep communities in 1984, over 590 species from vents and over 230 species from seeps have been described (Van Dover et al., 2002. Science 295: 1253-1257). Chemosynthetically fuelled communities have now also been found on large organic falls to the deep-sea floor such as whale falls and sunken wood, as well as on benthic zones of oxygen minimum. The data gathered in the last 30 years has shown that some species are shared amongst these ecosystems and our knowledge of their phylogeography improves with every new discovery. New species are continuously being discovered and described from research programmes around the globe and therefore ChEssBase is in active development and new data are being entered regularly. At present, ChEssBase includes data on 806 species and 432 genera from 76 chemosynthetic sites around the globe. These data contain information (when available) on the taxonomy, morphology, trophic level, reproduction, endemicity, habitat type and distribution. There are now 954 papers in our reference database. The first version of ChEssBase was available online in early 2005. In summer 2005, ChEssBase and the InterRidge biological database (www.interridge.org) were fused into a single source of information for biological data from chemosynthetic ecosystems (Ramirez-Llodra et al., 2005 IR News, 14). This second version of ChEssBase is available online since August 2005, with new records as well as new search and download options. Since December 2005, ChEssBase is integrated in the Ocean Biogeographic Information System (OBIS, www.iobis.org).