Invasion success and development of benthic assemblages: effect of timing, duration of submersion and substrate type

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Several studies suggested that the communities associated with artificial structures support more non-indigenous species (NIS) than natural habitats, and may function as corridors for their expansion. Our study focused on the role of substrate type, timing and duration of submersion as determinants of fouling community structure. We used plates made of basalt, concrete or fibreglass, to assess early, i.e., 3 months and late, i.e., 12 months, succession in benthic communities. To assess spatial and temporal variability of the results, sampling was performed at 2 locations and the experiment was repeated on two seasons of the year. Our results showed that the timing and duration of submersion affected the number and percent cover of natives and NIS, as well as community structure. Moreover, the present study showed no support for the hypothesis that marine NIS are more abundant than natives on artificial substrata. Overall, fibreglass presented the most different benthic community structure, supporting the fact that the extent and nature of the observed differences varied not only with natural vs artificial substrata, but also according to the type of artificial habitat considered. Both the dominance of NIS on artificial structures and the effect of artificial structures in the marine environment go beyond the differences in substrate type. Thus, our results are in agreement with previous studies that stated that appropriate strategies for environmental management should integrate ecological assessment in order to maintain natural patterns of distribution and abundance of organisms, scales of variability and relevant ecological processes.