High biodiversity on a deep-water reef in the eastern Fram Strait.

We report on the distribution and abundance of megafauna on a deep-water rocky reef (1796-2373 m) in the Fram Strait, west of Svalbard. Biodiversity and population density are high, with a maximum average of 26.7±0.9 species m(-2) and 418.1±49.6 individuals m(-2) on the east side of the reef summit. These figures contrast with the surrounding abyssal plain fauna, with an average of only 18.1±1.4 species and 29.4±4.3 individuals m(-2) (mean ± standard error). The east side of the reef summit, where the highest richness and density of fauna are found, faces into the predominant bottom current, which likely increases in speed to the summit and serves as a source of particulate food for the numerous suspension feeders present there. We conclude that the observed faunal distribution patterns could be the result of hydrodynamic patterns and food availability above and around the reef. To our knowledge, this study is the first to describe the distribution and diversity of benthic fauna on a rocky reef in deep water.