A comparison of megafaunal communities in five submarine canyons off Southern California, USA

Remotely operated vehicle surveys were conducted in five submarine canyons off Southern California during research expeditions in 2005 and 2010. Video transects from a range of depths were analysed to produce presence/absence data of megafauna for each site. A comparison of benthic communities at various depths, locales, and canyons was performed. No significant difference was found between canyon communities based on the level of sediment transport activity, however this may be due to the unbalanced sampling of this opportunistic study. There was significant variation in biological community composition and abundance amongst water depths. These depth-related trends are in agreement with the findings of the previous studies and are likely tied to depth-correlated variables such as hydrostatic pressure, temperature, salinity, and oxygen concentration. Species richness was found to initially increase with depth before declining rapidly at the mouths of the studied canyons. Low oxygen levels in the Santa Monica Basin, into which four of the surveyed canyons empty, may explain this.