Planktivores dominate rich benthic communities such as coral reefs and sponge beds. They thrive, on the one hand, on organic particles sinking from the sunlit surface layers or advected to them by currents, and possibly also organic substances dissolved in the water. But they also change the physico-chemical environment in the bottom boundary layer, through their filtering activities and metabolic processes, as well as the baffling action of their skeletons. Important changes occur in the bottom boundary layer and interstitial spaces within the coral reef framework, where the removal of organic materials and release of inorganic nutrients create strong spatial gradients which are maintained in balance with advection and mixing replenishing the boundary waters with organic molecules, pico- nano- and microphyoplankton, zooplankton and detrital particulate matter. We are interested in (1) a comparative quantification of the organic and inorganic material fluxes between benthic hotspots and bottom boundary layer waters, (2) the role heterotrophy of corals and sponges on the wide range of dissolved-colloidal-particular materials as a source of energy for building their skeletons, (3) the roles of minerals in the building the aragonite skeletons of corals and the glass skeletons and the variations of these processes in a changing environment.