Settlement of non-native Watersipora subtorquata (d'Orbigny, 1852) in artificial collectors deployed in Colombo Port, Sri Lanka

Abstract

Sri Lanka has been a key node in the historical maritime "silk route" since the 14th century. Colombo Port, with its strategic location in the Indian Ocean, handles most of the country’s foreign cargo. With increased foreign trade and ship traffic, Colombo Port environs are highly susceptible to invasions by non-indigenous species (NIS), which may threaten native biota. There is a dearth of information in Sri Lanka on the present status of the biofouling community and the nature and level of threats posed to native biota. The present study was conducted to investigate the biofouling assemblage within the Colombo Port. Artificial settlement collectors were deployed in order to study the colonization of fouling organisms. The encrusting foliaceous colonial bryozoan, Watersipora subtorquata was recorded for the first time in Sri Lanka. It was found on settlement collectors in two of the eight sampling locations one in New Pilot Station (12.50% cover) at 2 m depth and the other in Bandaranayake Quay (2.19% cover) at 1 m depth. Random and patchy distribution within the port environment and the absence of W. subtorquata on permanently located collectors indicate that their arrival is relatively recent. However, invasive behavior of W. subtorquata is significant since they can facilitate the settlement of other biofoulers providing a nontoxic substrate for them to attach. Furthermore, they pose deleterious impacts on ecology through interspecific competition with native organisms modifying community structure and dynamics. Therefore, continuous monitoring is vital for early detection and management of a possible invasion by globally known invasive species.