Productivity Studies on Baltic Macroalgae

Abstract

Productivity studies were performed in situ and in a laboratory incubator with the 14C-method on dominant macroalgae such as species of the green algae Monostroma, Acrosiphonia and Cladophora [M. grevillei, A. centralis and C. glomerata], the brown algae Pilayella, Scytosiphon and Dictyosiphon [P. littoralis, S. lomentaria and D. foeniculaceus] and the red algae Furcellaria, Phyllophora, Ceramium and Rhodomela [F. fastigiata, P. truncata, C. tenuicorne and R. confervoides] of the northern Baltic proper. Results are given from different seasons. Intra-specific variation can be almost 10-fold in situ (e.g., 1.5-11.4 mg C g dry wt-1 h-1 for C. glomerata, 0.8-8.5 for C. tenuicorne, and 0.6-6.1 for P. littoralis) and can thus greatly exceed the inter-specific variation for different species grown under similar conditions. Expressing the results as mg C assimilated per mg chlorophyll a (= photosynthetic index) often reduced the differences considerably, both within the between the species. Influence of sample size and length of exposure on the results is also discussed; 24 h experiments were used to calculate approximative turnover times for Cladophora, Pilayella, Phyllophora and Furcellaria. Productivity values ought to be given together with some characteristics of the algae, preferably with pigment content, to facilitate the evaluation of the influence of environmental variables.