The effect of salinity on a marine and a freshwater Ascomycete

Abstract

Lulworthia medusa, the marine isolate, grew significantly better in seawater than in freshwater medium. The growth of Ophiobolus graminis, the freshwater isolate, was reduced by one-half when grown in seawater. The growth of both species was similar in natural and artificial seawater. Neither species grew under anaerobic conditions.Warburg reactions indicate that the respiration of the freshwater species is reduced in seawater. The percentage reduction is about equal to the reduced growth in seawater, as compared to freshwater. The respirational rates of L. medusa in sea and freshwater were similar. Yet growth in seawater was much greater than in freshwater. Consequently, it is proposed that the respiratory energy produced in a freshwater environment is utilized for cellular functions other than biomass increase. In contrast to the marine isolate, the metabolic processes of O. graminis are severely affected by seawater. Ecological implications of the findings are discussed.