Biological invasions are considered a top threat to marine ecosystems worldwide. Many marine invaders are macrofouling species that are born out of constant global transport on ship hulls. These hulls are not only coated with a variety of paint types, but are also encrusted with microscopic biofilm communities that grow ubiquitously on submerged surfaces. Biofilm organisms, including diatoms, are known to alter the subsequent recruitment of macrofoulers. However, a link between biofilms and macrofoulers has never been established within the context of invasive species transport. In this study, we investigated (1) how shipping transport can alter underlying biofilms, and (2) how altered biofilms affect macrofouling recruitment and community composition. We cultivated biofilms on the Gulf of Mexico and Atlantic coasts of Florida before reciprocally transplanting them using five different transport methods. We measured post-transport diatom survivorship and changes to community composition, and then assessed macrofouling recruitment and growth on the transplanted biofilms for 14 weeks.
Results/Conclusions
Regardless of method, diatoms within the biofilms survived transport to act as seed populations for new biofilm growth at their destination. Transport method also modified community composition, resulting in new biofilms that altered subsequent macrofouling recruitment and growth. Approximately one quarter of all recruited macrofoulers exhibited selectivity for a particular biofilm. These selective macrofoulers included two globally invasive species: the macroalga, Aglaothamnion halliae and the encrusting bryozoan, Watersipora subtorquata. This study provides the first evidence of shipping transport as an engineer of biofilm communities that can drive invasive species recruitment. Such results may help explain the variation in invasion success among the thousands of macrofouling species transported daily.