Shipwrecks fouling community: Similarities with natural rocky reefs at different distances and wave exposure regimes

Abstract Artificial reefs, such as shipwrecks, have been considered as an alternative to mitigate impacts on natural hard bottoms. On the other hand, unplanned artificial reefs can lead to several negative effects such as the introduction of toxic substances, further propagation of exotic and pathogen species, and impacts on the surrounding soft bottom habitat through alteration of bottom topography and dynamics. Artificial reefs are colonized by different organisms, exchanging larvae and spores with the nearest natural reefs, however, few studies have focused on the understanding of the benthic communities’ structures found on these coupling natural and artificial reefs. The aim of this study was to investigate whether benthic communities of centenary shipwrecks can be similar to natural rocky reef communities established at a short scale distance. The benthic cover of shipwrecks sunken more than 100 years ago and that of natural reefs located at a gradient distance of 0, 1 and 2 km, and differently exposed to wave action, were compared. Using multivariate analyses, we found that similarities were influenced by both wave exposure and distance. In exposed area, the benthic fouling community in shipwreck was similar to the benthic communities of the nearest reefs, with decreasing values of richness with distance. Sheltered area communities presented high dissimilarity. Once the presence of an artificial reef influences benthic communities of natural ones, we recommend the evaluation of the cost/benefits of introducing artificial reefs, considering local hydrodynamics and proximity to natural environments, to minimize undesirable changes in natural environment.