Colonization and successional patterns of the mobile epifaunal community along an environmental gradient in a marine cave

In spite of the high importance of mobile epifauna in all marine habitats, their patterns of colonization and succession in marine caves have not been studied until now. In the present study, we used artificial substrates deployed at 4 positions along an environmental gradient of a similar to 100 m long cave system, and retrieved at different times (1.5, 3 and 6 mo), to explore the changes in abundance, species richness, and community structure of the epifauna. All inner cave stations showed significantly lower species richness and abundance. Despite different dispersal modes, the dominant species detected were able to quickly (< 1.5 mo) colonize the inner parts of the cave, yet their abundances were significantly higher outside the cave throughout the whole study. This suggests that environmental factors such as trophic supply or light intensity, rather than isolation, are probably the main factors responsible for the observed differences among cave positions. We also detected a gradient in the rate of community development, with communities outside the cave developing much earlier than those situated in the innermost parts. Finally, high temporal stability of communities was observed within the cave, which is likely related to more stable environmental conditions-a hypothesis supported by our detection of a dampening of the thermal oscillations within the cave. The low rates of community development and turnover observed inside marine caves supports the consideration of these habitats being very sensitive to natural and human-induced environmental disturbances, and hence a top priority for conservation.