THE EFFECT OF SALINITY CHANGES UPON THE PHYSIOLOGY OF EULITTORAL GREEN MACROALGAE FROM ANTARCTICA AND SOUTHERN CHILE .2. INTRACELLULAR INORGANIC-IONS AND ORGANIC-COMPOUNDS

The effects of hypo- and hypersaline treatments ranging from 7-68 parts per thousand on the intracellular inorganic ion and organic solute concentrations were determined in the eulittoral green macroalgae Ulothrix implexa, Ulothrix subflaccida, Enteromorpha bulbosa, Acrosiphonia arcta, and Ulva rigida from Antarctica and Southern Chile. The main inorganic cations were K+, Na+, and Mg2+ in all species. The major osmolyte in E. bulbosa, A. arcta, and U. rigida was K+ at increasing salinities. In both Ulothrix species, however, K+ levels declined during hypersaline stress and Na+ concentrations rose significantly. The main inorganic anions were Cl-, SO42-, and PO43 in all algae, while E. bulbosa and U. rigida also contained NO3-. A. arcta showed an extremely high SO42- content. The organic solutes proline, sucrose, and beta-dimethylsulphoniopropionate (DMSP) played an important role in osmotic acclimation. The occurrence of three organic osmolytes suggests an additional function of these solutes as cryoprotectants in the cold-water macroalgae investigated.