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Snapshot of macroalgae and fish assemblages in temperate reefs in the Southern European Atlantic ecoregion

Publication . Franco, Joao N.; Arenas, Francisco; Sousa-Pinto, Isabel; Santos, Carmen B. de los

Most of the biodiversity studies in the South European Atlantic Shelf ecoregion are limited to shallow subtidal or intertidal habitats, while deeper reef habitats, also of relevant ecological importance, are particularly understudied. Macroalgal communities, associated fauna, and sea surface temperature were studied in deep reefs (25–30 m) at two locations in this ecoregion: Parcel, North of Portugal (41º N), and Tarifa, Southern Spain (35º N). Specifically, algal assemblages were assessed using biomass collection and associated ichthyofauna was assessed using visual census techniques using scuba. Seawater surface temperature was higher (>3º C) in the southern region—Tarifa, compared to the northern region—Parcel. Our survey revealed 18 fish species and 23 algae species. The highest abundance of cold-water species (both macroalgae and fish species) was recorded in Parcel and warm-water species were dominant in Tarifa. In light of climate global trends, both regions might experience biodiversity shifts towards tropicalization. Current knowledge on their biodiversity is imperative to further evaluate potential shifts.

2020Journal article

Open access

Sea urchin grazing preferences on native and non-native macroalgae

Publication . Cardoso, André C.; Arenas, Francisco; Sousa-Pinto, Isabel; Barreiro, Aldo; Franco, Joao N

Herbivory plays a major role in shaping community dynamics across freshwater, marine and terrestrial habitats, by controlling patterns of abundance and distribution of primary producers, including seaweeds. In the context of biological invasions, the proliferation of non-native seaweeds has been often attributed to limited grazing by native herbivores on introduced species (“Enemy Release Hypothesis”, ERH). In our study, we aimed to explore the potential of an abundant generalist herbivore (the sea urchin Paracentrotus lividus) to graze on non-native in comparison to native macroalgae species. For this purpose, we used manipulative experiments to assess sea urchin preference on native and non-native seaweed species present in the northwest coast of Portugal. Specifically, we determined the preferences of P. lividus on brown seaweeds i.e. Laminaria ochroleuca, Saccorhiza polyschides and the non-native Undaria pinnatifida, and red seaweeds i.e. Chondrus crispus, Mastocarpus stellatus and the non-native Grateloupia turuturu. For each group of seaweed species, sea urchin preference and biomass consumption were examined. The nutritional (organic carbon and nitrogen) and chemical (phenolic content) features were also analysed, in order to assess their effect on sea urchin feeding. According to the results, P. lividus did not show a specific preference for any of the different seaweeds of each phylum. These results suggest that P. lividus is a generalist herbivore, not exerting a differential grazing pressure on non-native seaweeds when compared to native ones.

2020Journal article

Restricted access