Hanging paradise: the role of benthic predators in colonization success of exotic ascidians

CASTRO, KAREN LIDIA; GIACHETTI, CLARA BELÉN; TATIÁN, MARCOS; BATTINI, NICOLÁS; SCHWINDT, EVANGELINA

Puerto Madryn

Congreso; Xth International Conference on Marine Bioinvasions; 2018

Colonization success of marine exotic species in artificial structures depends on physical characteristics of these structures, and on environmental factors and/or ecological interactions among species. Predation plays a key role in tropical and subtropical areas with an apparent decrease at higher latitudes, establishing the hypothesis that tropical communities present a stronger biotic resistance to new exotic species. Among marine exotic species, ascidians appear to be the most successful sessile filter feeder in colonize new habitats as fouling communities on artificial structures. In this work, we (1) evaluate the effect of predation over colonization success of solitary ascidian community on different artificial structures, and (2) test the vulnerability of juveniles and adults of solitary exotic ascidian species in presence of different potential predators. We performed a field experiment in a cold-temperate port to evaluate the ascidian recruitment in fixed and hanging structures, in presence and absence of benthic and nektonic predators, and aquarium experiments under controlled conditions. We observed that benthic predators play a key role in the recruitment of exotic ascidians, which presented the highest cover in absence of these predators in both structures. Aquarium experiments showed that predation is higher over juveniles, while the effect on adults depends on the ascidian species. Sea urchins are the most successful predators, consuming both adults and juveniles. The results suggest that predation have a strong effect during the juvenile period with benthic species as the main predators. In this way, hanging structures might act as refuges from benthic predators for exotic ascidians in cold temperate regions.