MOLLUSCAN ASSEMBLAGES OF COLD-WATER CORAL MOUNDS: A NEW PERSPECTIVE ON QUATERNARY DEEP-SEA ECOSYSTEM AND ENVIRONMENTAL DYNAMICS IN THE WESTERN MEDITERRANEAN

Cold-water corals (CWC) contribute to biodiversity and serve as ecosystem engineers on continental margins worldwide. CWC mounds – built over geologic time by the interplay of biological, sedimentological, and oceanographic processes – provide habitats for a variety of macrobenthic taxa (e.g. molluscs, sponges, bryozoans). When compared with off-mound palaeoceanographic records, coral mound records offer ecological insights about the temporal and spatial drivers and dynamics of these deep-sea ecosystems. While surficial distribution patterns of living and recently-dead mound macrobenthic communities have been described, their temporal ecological relationship with mound formation is largely unexplored. Therefore, focusing on a single taxonomic group with high preservation potential, this study aims to 1) assess quantitatively temporal ecological trends of coral mound molluscan assemblages (bivalves and gastropods), and 2) correlate those data with coral growth and palaeoceanographic records. Our goal is to determine if and how a fossil molluscan assemblage time series can act as a proxy to the biological, sedimentological, and oceanographic factors influencing CWC mound development. Preliminary results from a coral mound gravity core through Brittlestar Ridge I in the Alboran Sea, western Mediterranean (~13.2 – 2.9 ka) indicate that throughout the core bivalves are more abundant and diverse than gastropods. However, these taxonomic groups yield generally similar downcore trends in abundance and diversity. Peak molluscan assemblages (defined by high abundance and or diversity) are significantly similar in composition and primarily alternate, rather than coincide, with periods of pronounced coral growth, which are associated with high productivity during the Bølling-Allerød interstadial (13.5-12.8 ka) and Early Holocene (11.3-9.8 ka). Further ecological and statistical assessments, including a comparative study with an adjacent coral mound gravity core, will refine our understanding of the ecological relevance of molluscan assemblages to the development, demise, and cyclicity of CWC mound ecosystems.