Ecophysiological adaptation strategies of some intertidal marine macroalgae of the Israeli Mediterranean coast

The dominant macroalgae growing at a rocky site on the Israeli coast were examined. While all algae apparently grew under light-saturating conditions, Enteromorpha compressa and Ulva lactuca, which occupy the uppermost level of the zone, were very tolerant to high and low temperatures as well as desiccation and varying salinity levels. They were also saturated both by HCO₃- (while submerged) and atmospheric CO₂ (during emergence). In contrast, four of the species dominating the middle and lower parts of the intertidal showed a narrower temperature response, could not tolerate exposure to high temperatures for prolonged time periods and were more sensitive to desiccation and salinity changes. In Acanthophora najadiformis and Hypnea musciformis, the sensitivity to desiccation in combination with the much higher rates of photosynthesis in air than in water might explain their growth in the mid intertidal. -from Authors