and drawbacks of each method (i.e. costs, training requirements, processing time, and 
interpretability of output). To our knowledge, this is the largest study to date to assess the 
comparability and reliability of analytic tools for ballast water compliance management under 
field conditions. Results offer insight into the benefits and limitations of each method, and 
support ongoing efforts to establish reliable uniform analytic methods for compliance 
monitoring under the International Ballast Water Management Convention. 
2.0 Methods 
2.1 Sample collection 
Samples were collected during ballast water uptake of sea water while in transit (sea 
chest intake positioned at 2.5 m depth), except one trial where samples were collected during 
discharge of Mindelo harbour water that had been held in a ballast tank for three days. The 
main ballast line of the RV Meteor is equipped with multiple sampling points to allow 
simultaneous collection of paired samples of untreated sea water in the engine room. During 
the voyage, we used three different sample collection devices (plankton net, SGS Ballast Water 
Sampler 1 (BWS1), and Triton skid NP 6007 TG 18) to run 20 paired trials, collecting a total of 40 
samples. The plankton net (50 pm diameter mesh) is the traditional method of concentrating 
ballast samples, whereas sampling skids are compact devices that have been developed to 
enable filtration and concentration of large volumes of water in a small space. During each trial, 
~1000 L of water was concentrated for analysis of organisms > 50 pm, using the 'cod' end (50 
pm mesh, plankton net) or inbuilt filter (50 pm mesh, sampling skids) of each sample collection 
device, to a final volume of 1 L (some exceptions; see Table A2). The volume of water filtered