Enhanced pelagic biomass around coral atolls

Understanding processes driving the distribution of mid-water prey such as euphausiids and lanternfish is important for effective management and conservation of their predators. In the vicinity of abrupt topographic features such as banks, seamounts, and shelf-breaks mid-water faunal biomass is often elevated, making these sites candidates for special protection. We investigated the spatial distribution of water column acoustic backscatter – a proxy for macrozooplankton and fish biomass in the 9 km transition zone between the pelagos and coral atolls in the Chagos Archipelago (6° N, 72° E). The purpose was to determine the magnitude and distance over which bathymetry may enhance biomass in the mid-water, and thereby identify the scale over which static topographic features could influence the open ocean. Two distinct sound scattering layers were identified, from the surface to 180 m and from 300 to 600 m, during daytime. Both layers exhibited significant increases in backscatter near features. Close