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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 are nearly identical (with the exception of not including limits for Vibrio cholerae in zooplankton samples) to those in the International Maritime Organization’s (IMO) convention (IMO 2004). Further, the limits are consistent with those in the US Environmental Protection Agency’s Vessel General Permit (VGP)—regulations on a suite of vessel operations, including the discharge of ballast water (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 filtration, UV radiation, electrolytic chlorination, and deoxygenation) to ensure that the discharge water meets the specifications. Determining concentrations of living organisms can require extensive effort and sensitive equipment, especially for sparse populations. For example, direct counts of living organisms ≥10 and

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 are nearly identical (with the exception of not including limits for Vibrio cholerae in zooplankton samples) to those in the International Maritime Organization’s (IMO) convention (IMO 2004). Further, the limits are consistent with those in the US Environmental Protection Agency’s Vessel General Permit (VGP)—regulations on a suite of vessel operations, including the discharge of ballast water (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 filtration, UV radiation, electrolytic chlorination, and deoxygenation) to ensure that the discharge water meets the specifications. Determining concentrations of living organisms can require extensive effort and sensitive equipment, especially for sparse populations. For example, direct counts of living organisms ≥10 and