Temporal patterns of recruitment and substrate use by the nonindigenous octoral Stragulum bicolor van Ofwegen and Haddad, 2011 (Alcyonacea) in Southern Brazilian Coast

Abstract

The nonindigenous octocoral Stragulum bicolor was first registered in Brazil in the year 2000, in the estuarine regions of Paranaguá and Cananéia (South/Southeast Brazil). Since then, this species has expanded its distribution along the Brazilian Coast, occurring mainly in estuarine and port areas with high vessel traffic, on several types of artificial and natural substrates. In the present study, the recruitment of S. bicolor was monitored for two years (May 2011 to March 2013), in two sites of the Paranaguá Bay (48°W; 25°S). To assess S. bicolor recruitment, polyethylene plates were kept submersed for two months. After this period, the plates were collected for laboratory analyses and replaced by new ones. The number of colonies, percentage cover, and type of substrate col onized were analyzed. On both sites, recruitment peaks were registered during the warmer months. However, the number of recruits and percentage cover was higher in one of the sites, probably due to minor influence of freshwater input from rivers and organic pollution from Paranaguá City. Moreover, although recru itment occurred on a greater number of substrates at the island, in both locations the most colonized substrates were the polyethylene plate, the bryozoan Hippoporina indica, and barnacle shells. Our data indicate that the population of S. bicolor is well established in the Paranaguá Bay and that it is a pioneer in habitat colonization but is also able to recruit on occupied substrates. The ability of S. bicolor to overgrow other organisms may result in harmful effects for native species.