CO2-fixierung und stofftransport in benthischen marinen algen. IV. Zur 14C-assimilation einiger litoraler braunalgen im submersen und emersen zustand

Abstract

The ability of CO 2 -fixation of three species of Fucus and of Laminaria saccharina , collected near Helgoland, both, submerged in seawater and suspended in air (emerged) was tested. Rates of photosynthesis and dark fixation as well as the distribution of 14 C among various labelled photosynthates and the kinetics of labelling were determined. When submerged, the species of Fucus show rather uniform photosynthetic rates (140 µmol CO 2 /mg chlorophyll a/h). Under atmospheric conditions (emerged) however, they show considerable differences according to their vertical distribution in the eulittoral zone near Helgoland. The photosynthetic rate of Fucus spiralis , the uppermost species of the eulittoral zone, is the same when submerged and emerged, whereas Fucus vesiculosus fixes about 75%, and Fucus serratus , occupying the lower part of the eulittoral zone, only 50% of the rates under submerged conditions. When not submerged, the sublittoral Laminaria saccharina is unable in performing CO 2 -fixation. Conclusively the species of Fucus unlike Laminaria are productive in a considerable amount even during low tide.