An overview of thirty years of research on ballast water as a vector for aquatic invasive species to freshwater and marine environments

Ballast water has been widely used by commercial vessels to control trim, draft and stability since the late 1870s. While the global transport of ballast water (and associated sediments) was first recognized as a potential dispersal mechanism for plankton in the late 1890s, quantitative research on the issue does not appear in the primary scientific literature until the mid-1980s. Following James T. Carlton's comprehensive review of the biology of ballast water in 1985, there was an explosion in research effort, with nearly 400 papers published in the last thirty years. This article provides a brief overview of the role that ballast water has played as a global vector for aquatic invasive species, summarizing the current state of ballast water research and emerging topics for future study, based on a review of articles in the primary scientific literature. Initially, the main research focus was to document the community composition of ballast water in ships arriving to ports around the world. In the late 1990s, risk ssessments examining shipping traffic patterns and environmental tolerances of species likely transported in ballast water dominated. By 2000, ballast water studies examining efficacy of various treatment strategies dominated, and papers exploring new tools and methods for more accurate/representative sampling and analysis of ballast water emerged as an important research topic. There is currently insufficient data to confidently quantify the probability of invasion associated with any particular inoculum density (or discharge standard), as a result, laboratory, field and modeling studies examining the relationship between invasion risk and the size of the initially released population (the 'risk-release relationship') are an emerging, high priority field of study.