GROWTH-PATTERN AND BETA-DIMETHYLSULPHONIOPROPIONATE (DMSP) CONTENT OF GREEN MACROALGAE AT DIFFERENT IRRADIANCES

Growth rates and intracellular beta-dimethylsulphoniopropionate (DMSP) concentrations of five green algal species collected from different geographic regions in 1986 and 1989 were determined under four photon flux rates. In Ulothrix implexa, U. subflaccida and Acrosiphonia arcta from Antarctica, growth was light-saturated at lower irradiances than in temperate Ulva rigida from Southern Chile and Blidingia minima from Germany. The DMSP content of Ulothrix implexa, A. arcta and Ulva rigida was directly correlated with the light factor: with increasing irradiance, algal DMSP level increased. In contrast, in Ulothrix subflaccida and B. minima DMSP concentrations gradually decreased up to a photon flux rate of 30-mu-mol m-2 S-1, then increased markedly under the highest photon flux rate tested. In non-growing, dark-in-cubated A. arcta DMSP content was reduced by 35%, while the DMSP pool of all other species remained unchanged, at the level of pre-culture conditions. Under full darkness all plants exhibited a significantly higher DMSP concentration compared with algae grown at low photon flux rates of 2 to 30-mu-mol m-2 S-1. These data show a correlation between growth pattern and DMSP biosynthesis, and may point to a species-specific minimum amount of light energy necessary for DMSP accumulation.