THE INFLUENCE OF ICE-RAFTED DEBRIS ON MEGABENTHIC DIVERSITY AND COMMUNITY STRUCTURE IN WEST ANTARCTIC PENINSULA (WAP) FJORDS

The west Antarctic Peninsula (WAP) is a glacially active margin composed of a network of deep fjords and has been subjected to extreme climate warming over the past few decades. Glacial retreat over much of the peninsula delivers ice-rafted debris (e.g. drop stones) which can act as a suitable habitat for many organisms, but a substantial amount of this material appears to be captured within coastal fjords. Because the majority of the deep seafloor consists of fine-grained sediments, delivery of drop stones to this habitat has the potential to increase local diversity by providing new substrate for colonization by both obligate and facultative hard-substrate fauna. To further understand the distribution and community structure of benthic hard-substrate megafauna, seafloor images from three WAP fjords were analyzed using Image J. Preliminary results from Andvord Bay suggest that the drop stones are small (average area of 130.81 cm²) and concentrated in the fjords, especially within the middle of the basin. Cluster analysis also revealed that community compositions differed between middle regions and the mouth of the fjord. Approximately 70% of species encountered are likely obligate hard-substrate fauna and would not be found in the deep fjord basins without the delivery of ice-rafted drop stones. These findings emphasize the interconnected nature of geologic and ecological processes in this region as well as the importance of recognizing this substrate in determining total benthic biodiversity of the WAP.