CATION REGULATION AND SURVIVAL OF THE RED ALGA, PORPHYRA PERFORATA, IN DILUTED AND CONCENTRATED SEA WATER

Abstract
P. perforata cells accumulate K and exclude Na over a wide range of salinity. A partial cytoplasmic volume control is noted between 50 and 100% sea water which is probably due to differential swelling of structural polysaccharides. Ca is especially important in maintaining K and Na concentration gradients in diluted sea water. Rain is potentially a more serious threat to survival of the alga in the intertidal zone, due in part to breakdown of ion transport, than is concentration of sea water.