The Finnish Institute of Marine Research (FIMR)
In summer 2001 the Finnish Institute of Marine Research (FIMR) and SAHFOS conducted an intercalibration study between a standard CPR and U-tow towed body onboard r/v Aranda. The aim of the study was to find out if samples taken by the U-tow and CPR reflect similar plankton densities. Both samplers were towed simultaneously at the same depth (8 m). The simultaneous towing presented no problems, and altogether 3 tows were completed, resulting in ca. 25 hours of tow time. The CPR filter mechanism was loaded with standard 280 m m silk gauze, whereas the U-tow PSM was loaded with 200 m m nylon gauze.
Results showed that there was an almost tenfold difference in plankton densities. The U-tow clearly sampled more organisms, but whether that can be explained by only slightly smaller mesh size (200m m/280m m), remains unclear. The analyses were performed differently, CPR samples traditionally on-silk at SAHFOS, and U-tow samples off-silk at FIMR. Based on these results, and the fact that Baltic zooplankters indeed are considerably smaller in size than their oceanic relatives, FIMR is now considering a mechanism capable of utilising finer gauze than the standard CPR 280 m m for their CPR. The CPR is intended to become an operational zooplankton monitoring tool in the Baltic Sea by 2003. The operations will be carried out by FIMR in co-operation with SAHFOS.
FIMR continued trials and testing with the U-tow onboard r/v Aranda. Most of the initial problems have now been solved, and we expect to use the unit fully operationally in summer 2002. (Juha Flinkman: juha.flinkman@fimr.fi).
