Deciphering the role of glass SPONGEs in the carbon and Silicate cycle of a Changing ANtarctic (SpongeScan)
Large Antarctic glass sponges create structurally complex habitats that promote benthic biodiversity. We are using low-disruptive, diver-based research techniques to understand their role in the carbon and silicate cycle.
Large glass sponges (hexactinellids) are formative structural elements of the benthic communities of the Antarctic shelf, helping to create habitat for a rich associated fauna. Glass sponge communities mostly colonise zones of high primary productivity, such as the ice shelves in the Ross and Weddell Seas and coastal polynyas. However, the mechanisms linking primary production to sponge growth are still unknown. Carbon and silicate probably limit the distribution and growth rate of these unique glass sponge communities on the Antarctic shelf, most of which occur in water hundreds if meters deep. McMurdo Sound in the Ross Sea, however, includes locations where large hexatinellids can be found at depths of less than 30 metres, allowing research divers access. In collaboration with New Zealand scientists, the feeding relationships are being analysed by AWI scientific divers using largely non-destructive, underwater measurements. These measurements exploit the way that these vase-like sponges filter water from outside their bodies into a central cavity, which finally exits the sponge via an apical aperture (the osculum). Water samples are taken from immediately next to the sponge (before filtration) and from the central cavity of the sponge (after passage through the sponge tissue) using thin tubes and analysed for food and nutrients including silicate to better understand the role of these sponges in the carbon and silicate cycle. The rate of pumping is estimated by observing the flux of water out of the osculum using natural tracer particles and a fluorescent dye. All data can be accessed via the Data Publisher for Earth & Environmental Science PANGAEA in the SpongeScan project.