Marine invasive alien species (IAS) of Sri Lanka: are we looking at the tip of the iceberg?

Ports have long been considered as the main entry points of marine bio-invasions as they facilitate the introduction of non-indigenous species (NIS) via shipping activities. Once established such NIS could act as invasive alien species (IAS), competing with native biota for food and space. Financial and ecosystem damages caused by such marine IAS are well evident from available literature and seemingly increasing with the ever-escalating marine traffic. Even though studies on biofouling communities are limited in Sri Lanka, various globally invasive macro-fouling organisms have been recorded. These include the American cupped oyster (Crassostrea virginica), the Pacific oyster (Magallana gigas), the European flat oyster (Ostrea edulis), the Hooded oyster (Saccostrea cuccullata), the Asian date mussel (Arcuatula senhousia), the Mediterranean mussel (Mytilus edulis galloprovincialis), the Common periwinkle (Littorina littorea), the Australian acorn barnacle (Austrominius modestus), the Striped barnacle (Amphibalanus amphitrite), the Goose neck barnacle (Lepas anatifera), Killer algae (Caulerpa taxifolia), and the European shore crab (Carcinus maenas). Lack of baseline data, genetic confirmations and periodic monitoring has limited possibilities of determining the invasiveness of these aliens however. Moreover, cryptic fouling organisms may have been overlooked, as was evident in a recent study recording the invasive bryozoans Watersipora subtorquata (red-rust bryozoan) and Schizoporella errata (branching bryozoan) for the first time in the Port of Colombo. To get a better understanding of the impact of marine NIS in Sri Lanka, a fouling community study is organized during which settlement plates will be deployed in the waters adjacent to the Port of Colombo. Identifications of the organisms on the fouling plates will be based on their morphology in combination with DNA-analyses. This study will focus specifically on colonial ascidians, as these species have not been studied yet in the region and may therefore include cryptic alien species that were overlooked in the past.