A rapid assay of phytoplankton viability

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Uptake and release of ballast water by ships can transport microorganisms from one part of the global ocean to another, with potentially negative consequences for natural ecosystems. To lessen the threat posed by the introduction of alien microorganisms, the International Convention for the Control and Management of Ships' Ballast Water and Sediments imposes global regulations for treatment of ships' ballast water, effective September 2019. The Convention imposes limits on the concentrations of viable cells in discharged waters. Existing regulations in the USA differ from the internationally standards in regulating the discharge of living cells. By definition, a viable living cell is able to reproduce, but a nonviable living cell is not. Because the goal of ballast water treatment is prevention of reproduction of microorganisms, cell viability offers a reasonable standard for treatment.Ballast water could be disinfected by application of ultraviolet C (UVC) radiation, which is widely used in treatment of drinking and waste water. UVC treatment renders cells nonviable by damaging nucleotides but does not necessarily kill them outright. Consequently, nonviable (so non-invasive) cells register as living if tested with the US-mandated live/dead assay in water treated with UVC. Acceptance of UVC for ballast water treatment depends on development of accurate alternative tests of viability.The most direct means of demonstrating viability is with a growth assay. However, growth assays can take weeks to complete, so are inappropriate for shipboard testing to ensure that a ballast water treatment system complies with regulatory standards. With the support of NSERC and Trojan UV, an hours-long fluorescence-based Rapid Assay of Phytoplankton Viability (RAPV) has been developed and tested in the laboratory. The goals of the proposed research partnership are to test the efficacy of the RAPV; to establish the theoretical foundations underlying the rapid assay; and to refine techniques for determining viability of single cells rather than bulk assemblages. Within 5 years, this research will develop tests for assessing phytoplankton viability that have immediate application to the ballast water treatment market but will also allow development of new industrial markets in assessment and treatment of impaired waters, in studies of natural populations and in mass culture of algae for food, biofuels and other high-value products.