Effects of water temperature and pH on growth and metabolite biosynthesis of coral reef sponges

Warmer, more acidic water resulting from increased emissions of greenhouse gases will impact coral reef organisms, but the effects remain unknown for many dominant groups such as sponges. To test for possible effects, adult sponges of 6 common Caribbean coral reef species—Aiolochroia crassa,Aplysina cauliformis,Aplysina fistularis,Ectyoplasia ferox,Iotrochota birotulataandSmenospongia conulosa—were grown for 24 d in seawater ranging from values experienced at present-day summer-maxima (temperature = 28°C; pH = 8.1) to those predicted for the year 2100 (temperature = 31°C; pH = 7.8). For each species, growth and survival were similar among temperature and pH levels. Sponge attachment rates, which are important for reef consolidation, were similar between pH values for all species, and highest at 31°C forE. ferox,I. birotulataandA. cauliformis. Secondary metabolites, responsible for deterring predation and fouling, were examined forA. crassa,A. cauliformis,E. feroxandI. birotulata, with 1 to 3 major metabolites quantified from each species. Final metabolite concentrations varied significantly among treatments only for zooanemonin fromE. feroxandN-tele-methylhistamine fromI. birotulata, but these concentrations were similar to those found in wild conspecifics. Considering adult sponges only, these findings suggest that the ecological roles and physiological processes of the 6 coral reef species will be little affected by the mean values of water temperature and pH predicted for the end of the century.