The status of the invasive sea squirts and barnacles found in the marinas and ports of Algarve, Southern Portugal

Dissertação de mestrado, Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

Exotic species have been considered by several authors as the worst threat that can occur to native biodiversity. Due to the lack of information on sea squirts and barnacle invaders in southern Portugal, the first step of this study aims to detect and identify their presence in the ports of the region. A comparison reporting differences between these ports was performed: i) fishing and recreational; ii) port location; iii) sheltered versus unsheltered facilities. The localities of Lagos, Quarteira-Vilamoura, Faro and Olhão were the study areas where seasonal sampling was done. A case study to obtain the total recruitment for the invasive species was also carried out, comparing surfaces and removal of invaders. Higher percentages of invasive species were found (60% for barnacles and 58.3% for sea squirts). The appearance of one invasive gastropod, originating in the West African coast, was reported in European waters the first time. Besides, for barnacle and sea squirt counting, there were significant differences in all comparisons except between seasons for barnacles and type of port for sea squirts. The main differences in the abundance, frequency of occurrence and communities seems to be related with the transit of international vessels, the settlement period and the conditions presented between ports in terms of exposure to the sea. Differences between surfaces during the case study were found, showing wallets as the best surface for sea squirts and cement plates for barnacles in general. Cement can be considered as the best surface for recruitment for the invasive Amphibalanus amphitrite in relation with the huge abundance found. The other two invasive Amphibalanus cf. eburneus and Styela plicata found during the experiment, did not present any preference between surfaces. So in general for the three invasive species of this area the use of cement plate guarantees a high rate of recruitment.