accuracy at low concentrations near Regulation D-2 standards while accuracy at high 
concentrations often observed in nature is less important. 
All analytic tools in this study aim to estimate abundance of organisms in ballast water 
samples, but the methods differ in terms of the taxa being measured and the units of their 
output. Both detailed analysis methods (i.e. microscopy and flow cytometry) are able to provide 
estimates in individuals/ml, but microscopy estimates account for both zooplankton and 
phytoplankton, whereas flow cytometry measurements only count phytoplankton (as used in 
this study, see Appendix B for methodology)(Veldhuis & Kraay, 2000). Further, since all flow 
cytometry samples were preserved before analysis in this experiment, measured 
concentrations are based on the cumulative number of organisms in samples (whether alive or 
dead before preservation). In comparison, microscopy (using motility and/or FDA 'staining') 
estimates are based only on living organisms. Likewise, FDA and ATP methods, which target 
metabolic activity and cellular adenylate content, respectively, quantify the biomass of both 
autotrophs and heterotrophs present in samples, albeit each measuring different properties of 
life. However, of these methods, only the Satake Pulse Counter (FDA method) provides 
estimates as individuals/ml, though other analytic methods (e.g. SGS ATP (aqua-tools)) may be 
able to estimate organism concentration for this size class in the future. In contrast, the CFA 
devices target only photosynthetic protists, but most can provide results in individuals/ml for 
the 10-50 pm size class through an empirical, instrument-specific conversion constant (i.e. bbe 
lOcells, TD BallastCheck-2™, Hach BW680). 
Generally, analytic methods were quite sensitive to the detection of organisms in 
samples over a broad range of cell concentrations. Results indicated, however, that the various