APICAL GROWTH-MEASUREMENTS OF FUCUS-VESICULOSUS L - LIMITED VALUE IN MONITORING

In monitoring the marine ecosystem, the search to find simple and univ ersal methods has led to selected species being commonly used as indic ator organisms. In the Baltic Sea, the bladder wrack (Fucus vesiculosu s L., Phaeophyceae), the only broadly distributed perennial macroalga, is commonly used in monitoring the state of the coastal ecosystem. On e parameter used is growth measured as apical tip length. The possible utility of apical growth of F. vesiculosus as an indicator of environ mental stress in relation to within- and between-plant variation, with in- and between-site variation, and between habitat (wave exposed vs. sheltered) variation was tested in the northern Baltic Sea. The analys is showed that variation within plants, among plants within a single s ite, and among sites of similar wave exposure was significant. Althoug h the difference between exposures also was important, the apical grow th of F. vesiculosus should not, without great caution, be used as a m easure of environmental condition.