Meeting Abstract

P2-19  Sunday, Jan. 5  Underwater Islands: The Influence of Surrounding Sediment on Dropstone Ecology CANADAY, EJ*; BROTHERS, CJ; SMITH, KE; AMSLER, MO; ARONSON, RB; SINGH, H; MCCLINTOCK, JB; Southern Adventist University; Walla Walla University; University of Exeter; University of Alabama at Birmingham; Florida Institute of Technology; Northeastern University; University of Alabama at Birmingham ecanaday@southern.edu

Dropstones deposited on the ocean floor by melting icebergs can act as islands of hard substrate in the surrounding sediment. While dropstones are deposited across the ocean, their effects on benthic macrofaunal biodiversity are best understood on muddy substrates. During a photographic survey of the seafloor on the continental shelf and slope off the western Antarctic Peninsula in 2013, we imaged nine benthic transects in depths between 400 and 2100 m. We recorded the diversity of macrofauna inhabiting areas with and without dropstones, as well as the percentage of hard substrate making up the surrounding area. The abundance of many macrofauna including bryozoans, glass sponges, and sea stars varied according to the percentage of hard substrate making up the seafloor. Across all substrate categories, the presence of dropstones significantly increased the abundance of macrofauna, with the effect most pronounced in areas primarily comprised of hard substrate (>70%). These results suggest that settling on or near dropstones is advantageous to many macrofauna, regardless of the composition of the surrounding sediment.