Evaluation of Compliance Tools Using Variable Fluorescence Fluorometry to Detect Living Organisms in Ballast Water: A Test Protocol for Collecting Measurements

Abstract

In an effort to mitigate the risk of transporting aquatic nuisance species, the United States Coast Guard (USCG) has finalized a rule limiting the concentrations of organisms in ships’ ballast water discharged into US Ports (US Coast Guard 2012). The specified concentrations reflect those in the International Maritime Organization’s (IMO) convention (IMO, 2004). Further, the limits are incorporated into the Vessel General Permit (VGP)—a set of guidelines on a suite of vessel operations (including the discharge of ballast water) regulated under the authority of the US Environmental Protection Agency (US EPA, 2013). In order to meet these limits, most ships will use a ballast water management system (BWMS). These systems incorporate a variety of technologies (including UV radiation, electrolytic chlorination, deoxygenation) to ensure that the discharge water meets the specifications. Determining concentrations of sparsely populated living organisms requires extensive effort and sensitive equipment. For example, organisms ≥10 and <50 µm may be quantified using a set of vital stains to label living organisms and tally the organisms via epifluorescence microscopy (Steinberg et al. 2011). Direct counts of living organisms yield concentrations comparable to the numerical standard. While this rigorous, complex, and time-consuming analysis is appropriate for verification testing of BWMS (US EPA, 2010), it is not feasible to perform this analysis during routine shipboard inspections. Rather simple, hand-held, field instruments (“compliance tools”) to rapidly assess the likelihood that the ballast water clearly exceeds the discharge limits will be of much greater value to the compliance officer. The tools for this approach must immediately produce measurements that are reliable indicators of the concentrations of living organisms within a regulated size class