Temporal variability in epifaunal assemblages associated with temperate gorgonian gardens

• Time was a primary driver of the ecological patterns, with higher diversity and abundance in spring and summer periods.
• Temporal variability was linked to changes in environmental parameters (temperature and chlorophyll a).
• Resident taxa consistently dominated the assemblages associated with Eunicella gazella and Leptogorgia lusitanica colonies.
• Rare species increased from spring to summer following the rise in seawater temperature.
• Turnover rate was higher from June to August and in small size gorgonian colonies, which were also less diverse.

The present study is one of the few that investigate the temporal variability of epifaunal assemblages associated with coral species, particularly the octocorals Eunicella gazella and Leptogorgia lusitanica in south Portugal. The results suggest time rather than colony size as a primary driver of the ecological patterns of these assemblages, which were dominated by amphipods, molluscs and polychaetes. Temporal variability was linked to changes in environmental parameters, namely temperature, chlorophyll a and particulate organic carbon. Hence, temporal variability must be taken into account for the design of future biodiversity assessment studies, as different patterns may be observed depending on the sampling time. Associated epifaunal assemblages were consistently dominated by resident species (i.e. species present in all sampling periods) and a peak of rare species was observed in the transition from spring to summer following the increase in seawater temperature. Turnover was particularly high in the transition between the spring and summer periods. In both hosts, turnover was higher in the small sized colonies, which harboured less diverse and less abundant assemblages that also differed from those inhabiting larger size colonies. The high levels of diversity associated with gorgonian colonies highlight the need for the conservation of this priority habitat.