Comparision of ship sampling techniques

During a European Union Concerted Action study on species introductions with ships, an intercalibration workshop on ship ballast water sampling techniques considered various phytoplankton and zooplankton sampling methods. For the first time, all the techniques in use world-wide prior 1998 were compared using a plankton tower as a model ballast tank spiked with the brine shrimp while phytoplankton samples were taken simultaneously in the field (Helgoland Harbour, Germany). Three cone shaped and eleven non-cone shaped plankton nets of different sizes and designs were employed. Net lengths varied from 50 to 300 cm, diameters 9.7– 50 cm, and mesh sizes 10– 100 µ ; ; ; m. Three pumps, a Ruttner sampler, and a bucket were also compared. Each method showed different results in efficiency and it is unlikely that any of the methods will sample all taxa. Although several methods proved to be valid elements of a hypothetical `tool box' of effective ship sampling techniques. The Ruttner water sampler and the pump P30 provide suitable means for the quantitative phytoplankton sampling, whereas other pumps prevailed during the qualitative trial. Pump P15 and cone-shaped nets were the best methods used for quantitative zooplankton sampling. It is recommended that a further exercise involving a wider range of taxa be examined in a larger series of mesocosms.