Report of the Study Group on Baltic Sea Productivity Issues in Support of the BSRP (SGPROD)

The Study Group on Baltic Sea Productivity Issues in Support of the BSRP (SGRPOD) met in Klaipeda, Lithuania, from 2–4 December 2004. The meeting continued the work on a com-parative analysis of Baltic Sea foodwebs, started during an ECOPATH modelling workshop in November 2004. The ECOPATH models were seen as a useful tool for system comparison, potentially also for the derivation of productivity indicators, however, difficulties arise in fine-tuning models to obtain comparable estimates across different Baltic Sea subsystems. Further, the meeting refined the definition of productivity indicators. As the most important criteria, productivity indicators should have a measurable impact on the next trophic level, i.e.,, changes in indicator value cause significant measurable change of quantitative parameters on the next trophic level. Key species within trophic networks should be used as indicators. The group further reviewed the list of parameters currently monitored in the Baltic Sea with re-spect to their suitability as productivity indicators, and also discussed a few additional vari-ables. Linked to productivity indicators selection was an overview of cost efficient monitoring methods to obtain Baltic Sea productivity data. Towed undulators, with a minimum sensor package of CTD, fluorometer, PAR sensor, autonomous plankton sampler, and dissolved oxy-gen sensor, could supplement measurements at a fixed station network and provide higher spatial coverage at given ship time. Fast repetition rate fluorometry was seen as an efficient way to replace 14C measurements of primary production, which would then only be required for calibration purposes. The meeting also agreed that an efficient monitoring strategy should follow a multi-platform approach, including fixed station measurements, data from undulators, and satellite information. The meeting suggested forming a working group within the BSRP to apply statistical methods for defining a cost-effective sampling strategy for BSRP phase II. SGPROD also reviewed the work of the BSRP productivity module in 2004, especially the planned open sea and coastal survey work programs.