Role of deep-sea sponges on carbon and nitrogen flows in deep-sea food webs

This project addresses the role of deep-sea sponges on carbon and nitrogen flows in deep-sea food webs. More specifically researchers want to know (a) how much bacterioplankton and DOM (dead organic matter) is taken up from the water column, and (b) whther sponges take up specific parts of the FDOM (fluorescent dead organic matter) pool. 

During RV Sonne cruise SO254 offshore New Zealand, I measure the in-situ oxygen consumption of sponges by placing benthic incubation chambers (CUBE) over individual soft-sediment sponges with the remotely operated underwater vehicle ROV Kiel 6000. Then oxygen consumption is measured continuously and six water samples will be taken automatically within a time period of 5 h. At the end of the incubation, the CUBE will be placed aside, the sponge will be collected with the ROV manipulator arm and both, sponge and CUBE, will be brought back on board. There, the water will be processed and preserved for the analysis of nutrient concentrations, the isotopic composition of silicic acid and cell numbers of bacterioplankton. Additional sub-samples of water will be taken at each time step for bulk DOC (dissolved organic carbon) concentration and emission-excitation matrix scans of FDOM. The contribution of sediment to the release or uptake of all parameter will be corrected by sediment core incubations on board.