The role of recreational marinas in facilitating the impacts of invasive non-native species.

Biodiversity is under threat from a number of drivers of global change with detrimental implications for coastal habitats. Of particular concern is the increase of invasive nonnative species (INNS), which continues to grow and shows no indication of saturation. In coastal and estuary systems, aquatic infrastructure, such as recreational marinas, are important entry points for INNS, acting as 'stepping-stone' habitats for their subsequent spread. As such the presence of INNS in these locations has been widely reported, however, many of their associated damaging ecological impacts are not fully understood and remain unquantified.
There is a growing focus on the presence of INNS in marinas, however limited attention has been made towards the associated ecological impacts. For example, the occurrence of 'spill-over' of invading species into adjacent sites has not been fully explored. Furthermore, little is known regarding the connectivity of INNS between marinas that exist as part of a local network and whether secondary spread from initial introduction sites can lead to isolated populations which develop unique sets of traits that underlie fitness and rapid population expansion. For INNS, however, that have been moved passively, such as between marinas via recreational boating, the occurrence of such 'trait sorting' is unknown.
Crustacea are considered one of the world's worst invading taxa, possessing a range of life history traits that are conducive to successful establishment, including short generation time and broad environmental tolerance. Caprellidae are a particular notable group, exemplifying these traits and supporting high numbers of non-native amphipod species. One such example is the globally invasive Japanese skeleton shrimp Caprella mutica, which originates from north-east Asia and has become one of the most rapidly invading species in Europe. Associated with aquatic infrastructure and colonising habitats such as floating pontoons, mooring ropes and aquaculture cages, there are now numerous reports of the presence of C. mutica across the UK, many which are closely linked to recreational marinas.
Having been first reported in Scotland in 2002, C. mutica was recorded in the Clyde estuary in 2006, however, it was considered to have been present before this time yet it has not been thoroughly studied within this system. Within the Clyde estuary there exists a local network of well-established marinas supporting a high degree of recreational boat use with connections to the broader Scottish West Coast region. Therefore, this provides an opportunity for understanding the invasion of an INNS within a marina network and the potential for overspill into neighbouring habitats/infrastructure and subsequent ecological impact. As is common with INNS, C. mutica has been shown to be highly aggressive with such behaviour linked to reproductive success and offspring survival, however it is not known how this differs between invaded locations on a local (or global) scale.
In this context, understanding metrics related to impact such as differences in life-history traits and behaviour between different populations is vital because of their known links to INNS impact and potential predictive power for future invasions. During the last decade, marine invasive species have received increased attention from both scientists and policy makers, however ecological knowledge to address their impacts lags behind that of other systems. The aim of this project is to therefore investigate the role of recreational marinas in the facilitation of impact of an invasive species. By doing so we will elucidate mechanisms underlying impact, providing vital and lacking information on the interaction of novel habitats and species invasions in coastal systems.