Habitat characteristics shaping zoantharians’ distribution at intertidal habitats of the Canary Islands

Le résumé fourni par la source

Ocean warming is facilitating the proliferation of zoantharians worldwide due to their thermophilic affinities. However, other anthropogenic factors, such as declining water quality, have been appointed to favour the occurrence of zoantharians dominated areas and barrens. Subtropical and tropical intertidal habitats are especially vulnerable to zoantharians outbreaks due to the progressive increase in ocean temperature and because it is where most human pressure is concentrated. The aim of this study was to evaluate the abundance of intertidal zoantharians populations, related to habitat characteristics (rugosity and submerged substrate) and the presence of other benthic organisms, such as sessile invertebrates and macroalgae. Number and coverage of zoantharian colonies were recorded in transects (20 × 4 m) along 25 intertidal rocky platforms of the Canarian Archipelago, and photographic techniques in quadrats were used to examine the relationships between the percentage of substrate cover of zoantharians, macroalgae and sessile invertebrates by means of correlations analyses. Results indicated that high levels of rugosity favour the abundance and coverage of Palythoa aff. clavata and Zoanthus pulchellus , and the proportion of submerged substrate was also important in determining Zoanthus coverages. The presence of extensive macroalgae communities was seen to reduce zoantharian coverages, being the only sessile organisms that were able to outcompete them for space in the Canary Islands. Thus, this study provided valuable information about patterns of abundances and coverages of intertidal zoantharians useful for future monitoring of intertidal populations of zoantharians in Canary Islands and their interaction with surrounding marine organisms.

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