THE EFFECT OF LIGHT-INTENSITY AND DAYLENGTH ON THE BETA-DIMETHYLSULPHONIOPROPIONATE (DMSP) CONTENT OF MARINE GREEN MACROALGAE FROM ANTARCTICA

The beta-dimethylsulphoniopropionate (DMSP) concentrations of 5 Antarctic green algae grown at 2, 30 and 55-mu-mol photons m-2 s-1 were determined during a period of one year, cultivated under fluctuating daylengths mimicking the conditions of the natural habitat at King George Island, Antarctica. The intracellular DMSP content of all species decreased simultaneously with decreasing daylengths and vice versa. Additionally, the DMSP level was affected by the light intensity: the higher the photon fluence rate the greater the algal DMSP concentration. Under conditions of darkness, there was a degradation of the DMSP pool in members of the Acrosiphoniales, while the DMSP content in members of the Ulvales did not change. The results indicate a light-dependent DMSP accumulation in algae. Therefore, they may help to explain the seasonal variability of DMSP and its cleavage product dimethylsulphide (DMS) in coastal waters.