Acanella arbuscula (Johnson, 1862) is a cosmopolitan deep-water octocoral that can form dense fields in soft bottom areas. Here we investigated its role as habitat for other species through examination of 623 colonies collected from bottom trawling in the Northwest Atlantic between 2003 and 2018, from mean depths of 79–1439 m. In addition, in 2021 we used a remotely operated vehicle at 1317 m to collect three paired sediment push-cores (with and without A. arbuscula) to investigate the potential influence of A. arbuscula’s on infauna diversity. We show that 43% of the analyzed colonies had one or more associates, and a maximum of 18 individuals per colony. The sea anemone Stephanauge acanellae (Verrill, 1883) had the highest occurrence (28.6%), followed by the polychaete (scale worm) Neopolynoe acanellae (9.5%), nematodes (8.2%), sponges (4.8%), ophiuroids (4.2%), scalpellid barnacles (2.1%), and scallops (0.8%). Number of associates is likely underestimated due to possible specimen loss during sampling. Number of associates significantly increased with colony height, but not with depth or latitude. Analysis of δ15N from A. arbuscula and hosts indicate that while the coral likely feeds on particulate organic matter, anemones, polychaetes and ophiuroids feed on higher trophic levels. Anemones, nematodes, and ophiuroids were more frequently found on samples collected in May, while scalpellid barnacles and polychaetes in October. From the limited number of samples available for the study, no significant differences in infauna diversity were found between samples with vs. without corals. Our study shows that A. arbuscula in the Northwest Atlantic consistently hosts several invertebrate species, but diversity likely varies in other locations hosting the coral.
Neves et al. (Tue,) studied this question.