Algal Productivity in Salt Marshes of Georgia1

Gross primary production of algae in the intertidal marshes on the coast of Georgia was measured at various seasons. Measurements were also made of light, temperature, pH, depth of flooding at high tide, and sedimentary chlorophyll. Migration of the algae in the sediments was observed along creek borders. Production during low tide is 150 mg C/m 2 /hr in winter and 20–30 mg C/m 2 /hr in summer. Production under water, during high tide is 200 mg C/m 2 /hr in August and drops to 50 mg in winter. A relation between the changes in production and the regime of light, temperature, and tides is postulated. Changes in production during high and low tide alternate so as to result in a nearly constant daily production throughout the year. The annual gross algal production is estimated to be 200 g C/m 2 . Net production is not less than 90 per cent of gross production. Photosynthetic efficiency varied from 3 per cent to less than 0.1 per cent.