Epibenthic faunal community dynamics and seasonal species turnover in a deep-sea coral ecosystem

Deep-sea coral ecosystems represent oases of life in the deep ocean, often hosting abundant and diverse faunal communities. Although mounting evidence indicates that deep-sea benthic communities are highly dynamic and can change over scales of a few hours to seasons or years, such dynamics have never been characterized in deep-sea coral ecosystems. We used a time-lapse camera deployed for a year at a depth of 1230 m on Sur Ridge (Monterey Bay National Marine Sanctuary) to characterize hourly changes in megafaunal abundance and diversity in a deep-sea coral assemblage. The response of community dynamics to variation in environmental factors, including surface net primary production as well as current speed/direction, temperature and acoustic backscatter (a proxy for particle and zooplankton density) at depth, was also evaluated. Overall, 33 taxa from 6 phyla, including multiple commercially valuable species, were observed throughout the study period. The strong seasonal pattern and periodicities in the occurrence of the most abundant taxa likely drove the observed temporal trends in overall abundance and diversity. Fluctuations in food availability may have, at least partially, driven these trends, as indicated by the significant relationship between community dynamics, surface net primary production and acoustic backscatter at depth. However, the low explanatory power of environmental parameters tested here suggest that biotic factors such as individual behaviors and species interactions had a strong influence on community dynamics. This study emphasizes the role of deep-sea coral as habitat and the need for monitoring to better understand how environmental and biological processes interact to shape associated faunal communities.