Metabolic responses of the deep-water sponge Geodia barretti to suspended bottom sediment, simulated mine tailings and drill cuttings

Abstract

Northeast Atlantic sponge beds are recognized as local hotspots for biodiversity and nutrient cycling. Despite their important functional role little is known about their sensitivity to effluents from the expanding hydrocarbon-, mining- and bottom trawling industry. Here, data on physiological and biological responses of the common demosponge Geodia barretti to short (4h) and long-term (50day) cyclic exposure of suspended particles are presented. The laboratory study showed that 4hour pulse exposures with crushed rock particles at 500mgl−1 caused a 50% drop in oxygen consumption but with a quick recovery to pre-exposure oxygen consumption once suspended sediment loads returned to background levels. Long-term cyclic exposure (12h each 24h) for 29days caused a permanent drop in oxygen consumption with 60% in sponges exposed to 50mgl−1 of crushed rock but with no apparent effect on the energy content of the sponge. Oxygen consumption and energy content of sponges exposed to natural bottom sediments at the same concentration remained unchanged. In conclusion, G. barretti appears to have well developed mechanisms to resist sediment stress, however, the study demonstrated that operations releasing large amounts of suspended crushed rock such as exploration drilling and submarine tailings disposal near sponge beds should be carefully planned to avoid long-term losses of benthic ecosystem functions, such as organic matter re-mineralization.