Citation:

Darling, J., J. Martinson, Y. Gong, S. Okum, E. Pilgrim, K. Pagenkopp Lohan, J. Carney, AND G. Ruiz. Ballast Water Exchange and Invasion Risk Posed by Intracoastal Vessel Traffic: An Evaluation Using High Throughput Sequencing. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 52(17):9926-9936, (2018). https://doi.org/10.1021/acs.est.8b02108

Impact/Purpose:

For over three decades the transport of ballast water has been acknowledged as an important vector of species introductions to coastal ecosystems, and has been implicated in establishment of invasive species with significant ecological and socio-economic impacts1-3. This recognition has driven development of various legal instruments for mitigating invasion risks posed by global vessel traffic. Here we explore biodiversity of ballast water being transported to Valdez, Alaska from multiple ports on the Pacific coast of the US. Given the prevalence of known invasive coastal species in west coast donor ports, voyages from the mainland US to AK potentially present substantial invasion risk17, 18, risk that may be heightened in the future by increasing vessel traffic and warming trends at higher latitudes19, 20. We explore the role of BWE in moderating this risk by comparing diversity present on ships conducting BWE with that present in unmanaged ballast.

Description:

Ballast water remains a potent vector of non-native aquatic species introductions, despite increased global efforts to reduce risk of ballast water mediated invasions. This is particularly true of intracoastal vessel traffic, whose characteristics may limit the feasibility and efficacy of management through ballast water exchange (BWE). Here we utilize high throughput sequencing (HTS) to assess biological communities associated with ballast water being delivered to Valdez, Alaska from multiple source ports along the Pacific Coast of the United States. Our analyses indicate that BWE has a significant but modest effect on ballast water assemblages. Although overall richness was not reduced with exchange, we detected losses of some common benthic coastal taxa (e.g., decapods, mollusks, bryozoans, cnidaria) and gains of open ocean taxa (e.g., certain copepods, diatoms, and dinoflagellates), including some potentially toxic species. HTS-based metabarcoding identified significantly differentiated biodiversity signatures from individual source ports; this signal persisted, though weakened, in vessels undergoing BWE, indicating incomplete faunal turnover associated with management. Our analysis also enabled identification of taxa that may be of particular concern if established in Alaskan waters. While these results reveal a clear effect of BWE on diversity in intracoastal transit, they also indicate continued introduction risk of non-native and harmful taxa.

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