A widespread contaminant enhances invasion success of a marine invader

Abstract

1. The global transfer of species by human vectors is continuing despite the use of managerial controls such as antifouling biocides and pesticide applications. The process of introduction now exposes species to novel conditions which may select for tolerance to a contaminant. Invader establishment success is influenced by both the supply of invasive propagules and disturbance. Therefore, it is important to understand whether tolerance to an anthropogenic disturbance, such as contamination, can change the parameters of supply in a way that inadvertently augments the invasion process.2. To test whether the invasion process is influenced by a widespread contaminant, we investigated how recruitment of the invasive hull-fouling bryozoan Watersipora subtorquata is affected by exposure to copper-based antifouling paint. We quantified settlement patterns in control and copper environments and then assessed post-settlement survival and fitness components.3. Copper significantly increased total recruitment success despite greater post-settlement mortality. Surviving recruits differed morphologically, with shorter ancestrulae and smaller colonies in high copper treatments. These results show a strong positive affiliation between larval W. subtorquata and high levels of copper although there are associated fitness costs.4. Syntheses and applications. We found a direct positive effect of contamination on recruitment of a common invasive species. This process is likely to be relevant to other non-indigenous species (NIS) that exhibit a positive affiliation with metal contamination. Copper can potentially enhance success at multiple stages of the invasion process, including facilitating transport and establishment, by increasing the supply and retention of individuals into anthropogenically disturbed environments. Identification of tolerance to contamination as a species trait may also aid in predicting a species invasiveness and spread. Management of metal pollution through remediation and alternative copper-free antifouling techniques would help prevent the spread and establishment of many marine NIS.