The human-mediated introduction of marine non-indigenous species is a centuries- if not millennia-old phenomenon, but was only recently acknowledged as a potent driver of change in the sea. We provide a synopsis of key historical milestones for marine bioinvasions, including timelines of (a) discovery and understanding of the invasion process, focusing on transfer mechanisms and outcomes, (b) methodologies used for detection and monitoring, (c) approaches to ecological impacts research, and (d) management and policy responses. Early (until the mid-1900s) marine bioinvasions were given little attention, and in a number of cases actively and routinely facilitated. Beginning in the second half of the 20th century, several conspicuous non-indigenous species outbreaks with strong environmental, economic, and public health impacts raised widespread concerns and initiated shifts in public and scientific perceptions. These high-profile invasions led to policy documents and strategies to reduce the introduction and spread of non-indigenous species, although with significant time lags and limited success and focused on only a subset of transfer mechanisms. Integrated, multi-vector management within an ecosystem-based marine management context is urgently needed to address the complex interactions of natural and human pressures that drive invasions in marine ecosystems.

Aim The Panama Canal expansion, scheduled for completion in 2015, is expected to have major effects on commercial shipping and port operations throughout the world, with potential consequences for the transfer and establishment of non-indigenous species that remain largely unexplored. We developed a series of scenario-based models to examine how shipping traffic patterns may change after expansion and consider possible implications for species transfers and invasion dynamics in the USA. Location Coastal USA, excluding Alaska and HawaiiMethods Using a Monte Carlo simulation approach, we predicted changes in discharged ballast water, wetted surface area of ship hulls and frequency of ship arrivals modelled under scenarios that are based on (1) current shipping patterns from the western Pacific Rim to the USA, (2) estimates of fleet expansion and (3) diversion of traffic away from the US West Coast through the Panama Canal.Results During the 5-year period following canal expansion (2015-2019), our models estimated that the Gulf and East coasts would receive 78% and 99% median increases in total ballast discharge and 172% and 182% increases in total wetted surface area, respectively. For the West Coast, our models estimated 9.6% median decreases in both total ballast discharge and wetted surface area. We further predict that many ports in the Gulf and East coasts will receive up to three times the current number of arrivals and increased ballast water discharge, from this region after expansion.Main conclusions Our scenario-based analysis provides a first estimate for increases in frequency, magnitude and spatial distribution of exposure that the Gulf and East coasts will experience due to ships and ballast arriving from the western Pacific, following the canal expansion. If organisms transported via ballast water or ship hulls are able to survive transit of the canal, the predictions suggest increased likelihood of introduction along these coasts by species originating in the western Pacific.

An accepted solution to the environmental problems related to a ship's ballast water has been the adoption and proper utilization of approved onboard ballast water plans and management systems (BWMS). On 8 September 2017, the International Maritime Organization Ballast Water Management Convention comes into force, and under this Convention, ships engaged in international trade must have an approved BWMS aboard to discharge ballast water, reducing species transfer. In response to enormous global concern about this problem, the overwhelming majority of the BWMS, approved currently for use by International Maritime Organization (IMO) and United States Coast Guard, utilize two main technologies (electro-chlorination or ultraviolet irradiation) as their principle mode of disinfection, often used in combination with filtration. However, both technologies have been questioned regarding their practically, efficiency, and possible environmental impacts upon discharge. This review article aims to explore some questions about these two technologies, drawing attention to some current uncertainties associated with their use. Also, it draws attention to some technical obstacles and regulatory impediments related to the new development of green biocide technology, which largely has been ignored, despite its potential as a simpler, cleaner and effective technology.

Commercial shipping is the primary pathway of introduction for aquatic nonindigenous species (NIS), mainly through the mechanisms of ballast water and biofouling. In response to this threat, regulatory programs have been established across the globe to regulate and monitor commercial merchant and passenger vessels to assess compliance with local requirements to reduce the likelihood of NIS introductions. Resource limitations often determine the inspection efforts applied by these regulatory agencies to reduce NIS introductions. We present a simple and adaptable model that prioritizes vessel arrivals for inspection using proxies for potential propagule pressure (PPP), namely a ships’ wetted surface area as a proxy for the likelihood of biofouling-mediated PPP and ballast water discharge volume as a proxy for ballast water-mediated PPP. We used a California-specific dataset of vessels that arrived at California ports between 2015 and 2018 to test the proposed model and demonstrate how a finite set of inspection resources can be applied to target vessels with the greatest PPP. The proposed tool is adaptable by jurisdiction, scalable to different segments of the vessel population, adjustable based on the vector of interest, and versatile because it allows combined or separate analyses of the PPP components. The approach can be adopted in any jurisdiction across the globe, especially jurisdictions without access to, or authority to collect, risk profiling data or direct measurements for all incoming vessel arrivals.