The effects of wave exposure and host cover on coral-associated fauna of a centuries-old artificial reef in the Caribbean

An increasing number of artificial reefs (ARs) are constructed to compensate for the loss of natural reefs (NRs), but little is known about their benthic community composition. Here, we compared the densities of coral-associated fauna (CAF) between a centuries-old manmade structure and the nearest NR at St. Eustatius, eastern Caribbean. Overall, no significant difference in the density of CAF (coral-dwelling barnacles, crabs, worms) was found between the NR and the AR, nor between the exposed and sheltered sides of each. Significantly different densities of CAF related to host cover were observed among corals on both the AR and the NR. Per host species, the AR did not show such differences in density between exposed and sheltered sides, although these differences were observed on the NR. Thus, turbulence and host cover regulate the density of CAF, while differences also depend on host species composition. Furthermore, from an ecological engineering perspective, the present AR resembles the NR in overall design, but not in relief rugosity and surface structure, which are also considered important contributors to the difference in species assemblages of the host corals and their CAF, even after many decades of community development

A centuries-old manmade reef in the Caribbean does not substitute natural reefs in terms of species assemblages and interspecific competition

With increasing maritime activities in the proximity of coral reefs, a growing number of manmade structures are becoming available for coral colonisation. Yet, little is known about the sessile community composition of such artificial reefs in comparison with that of natural coral reefs. Here, we compared the diversity of corals and their competitors for substrate space between a centuries-old manmade structure and the nearest natural reef at St. Eustatius, eastern Caribbean. The artificial reef had a significantly lower species richness and fewer competitive interactions than the natural reef. The artificial reef was dominated by a cover of crustose coralline algae and zoantharians, instead of turf algae and fire corals on the natural reef. Significant differences in species composition were also found between exposed and sheltered sites on both reefs. Our study indicates that even a centuries-old manmade reef cannot serve as a surrogate for natural reefs