Picoplankton removal by the coral reef community of La PrÈvoyante, Mayotte Island

We examined the trophic contribution of pico-and nanoplankton to a patch reef dominated by scleractinian corals and located at Mayotte Island (Comoro Archipelago). Pico-and nanoplankton concentrations, as well as total particulate organic matter, were measured on a sandybottom and a patch reef transect. Results showed that particles <10 m accounted for 74% of the chlorophyll a concentration and for 47% of the total living carbon. Synechococcus sp. represented 65% of the chlorophyll < 3 m and 53 and 67% of the autotrophic carbon and nitrogen, respectively, followed by picoeukaryotes, nanoeukaryotes and Prochlorococcus sp. Concentrations of total chlorophyll a, as well as picoplankton groups, were depleted 30 to 45% above the reef compared to in the adjacent waters and in sandy-bottom samples. Concentrations of nanoflagellates and total particulate organic matter, by contrast, remained unchanged during their passage across the reef. These results suggest selective grazing of picoplankton by the benthic community and compound the importance of picoplankton for the benthic-pelagic coupling and trophic dynamics on coral reefs.