Meeting Abstract

54.5  Saturday, Jan. 5  Glass sponge reefs significantly impact water properties in a marginal sea, the Strait of Georgia KAHN, A.S.*; YAHEL, G.; TUNNICLIFFE, V.; LEYS, S.P.; Univ. of Alberta, Edmonton; Ruppin Academic Center, Michmoret, Israel; Univ. of Victoria, British Columbia; Univ. of Alberta, Edmonton kahn@ualberta.ca

Glass sponges form unique reef habitats similar to coral reefs in the Strait of Georgia (SOG), a marginal sea surrounded by major cities such as Seattle and Vancouver. Individual sponges can affect localized water properties; since reefs are so vast, they may alter water properties on a regional scale. Reef sponges in the SOG (some 11 million oscula) filter over 6 billion liters of water per hour, removing bacteria and other particulates while adding ammonium to the water. We used SIP samplers to compare ambient water near reef sponges with water exhaled from oscula of Aphrocallistes vastus, the dominant reef-forming species in the SOG. Whether living in reefs or solitarily, each osculum adds ~ 200 nmol/l of NH4+ to expelled water, independent of differences in ambient NH4+ concentrations. Similarly, bacteria were removed at about the same efficiency whether sponges were in a reef or solitary. Each reef sponge drew down 0.5609 ┬ÁM oxygen, or used 241 mJ per liter pumped to filter feed. Our calculations show that the 12 known reefs in the SOG remove hundreds of kilograms of carbon per year in the form of bacteria, and lesser amounts of Synechococcus-like and large eukaryotic cells. Though they are live habitats and their effects are not nearly as great as Fraser River inputs, the sponge reefs alter water properties by removing bacterioplankton and oxygen, and adding ammonium. Our findings suggest that the water properties of the SOG may depend heavily on sponge reefs being present just as the reefs rely on SOG water properties.