Early Succession Patterns of Benthic Assemblages on Artificial Reefs in the Oligotrophic Eastern Mediterranean Basin

Abstract

The colonization of artificial structures by benthic organisms in the marine realm is known to be affected by the general trophic patterns of the biogeographical zone and the prevailing environmental traits at the local scale. The present work aims to present quantitative data on the early settlement progress of macrofaunal benthic assemblages developing on artificial reefs (ARs) deployed at the Underwater Biotechnological Park of Crete (UBPC) in the oligotrophic Eastern Mediterranean. Visual census and subsequent image analysis combined with scraped quadrats were used to describe the establishment of the communities and their development over three consecutive campaigns, spanning 5 years post-deployment. Macroalgae consistently dominated in terms of coverage, while sessile invertebrates displayed different patterns over the years. Polychaeta and Bryozoa were gradually replaced by Cnidaria, while Porifera and Mollusca displayed an increasing trend over the years. Motile benthos was mainly represented by Mollusca, while the abundance of Polychaeta increased in contrast to that of Crustacea. For both sessile and motile assemblages, significant differences were observed among the years. The results of this study indicate that ecological succession is still ongoing, and further improvement in the monitoring methodology can assist towards a more accurate assessment of the community composition in complex AR structures.

A Report on the Artificial Reef Use in Grenada, West Indies

“…While statistically significant, others have reported increases in erect sponges in a depth-dependent way, suggesting a selection in growth and colonization due to tidal wave action [66]. The lack of erect sponges is supported by reports of other young (>3 years) concrete artificial reefs, where only encrusting sponges were detected [67]. Sponges previously were considered a 'fouling' species, which many times prepare the area for coral colonization [68], but some recent data suggest they may reduce coral recruitment through space competition [69,70].…”

Habitat Fragmentation Enhances the Difference between Natural and Artificial Reefs in an Urban Marine Coastal Tract

“…Early studies on the colonization of artificial structures in the NW Mediterranean indicated that it takes approximately 3 years for the community to reach a mature stage in terms of both biomass [72] and species composition [73,74]. Similar experiences in other seas, however, have shown that climax communities were reached in 5 to 20 years [75][76][77], but the differences between natural and artificial reefs have been observed to persist even for much longer times [71,78,79]. At St. Eustatius (eastern Caribbean), no significant difference in the density of coral-associated fauna was found between a centuries-old manmade structure and the nearest natural reef [49], notwithstanding differences in relief rugosity and surface structure, which are also known to exert an important influence on the entire epibenthic community [52,80].…”

Surface Integrity Could Limit the Potential of Concrete as a Bio-Enhanced Material in the Marine Environment

“…However, approximately two years after deployment most species have settled into the habitat and, thereafter, begin to establish themselves, reaching climax communities in 5 to 20 years (Hawkins et al, 1983;Pinn et al, 2005;Gacia et al, 2007;Coombes, 2011). Nevertheless, and despite these being dynamic communities, the differences between natural and artificial coastlines can persist even in centuries-old artificial structures, regardless of the substrate they are made of, indicating that, in general, artificial shorelines are poor surrogates of natural habitats (Firth et al, 2016;Hill et al, 2021;Rallis et al, 2022). Artificial structures such as seawalls have low structural complexity at various spatial scales and a low presence of tide pools, pits, grooves, bumps, ledges, and crevices, which reduce microhabitats' heterogeneity when compared to natural areas (Moreira et al, 2006;Loke and Todd, 2016;Cacabelos et al, 2018;MacArthur et al, 2020;Strain et al, 2020).…”