Ecological Studies of Floridian Eucheuma (Rhodophyta, Gigartinales). II. Photosynthesis and Respiration

The photosynthetic response of Eucheuma gelidium, E. acanthocladum, E. isiforme, E. nudum, and a species designated as the Bahia Honda form, because of its unclear taxonomic status, were recorded under a variety of light intensities, temperatures, and salinities. Light saturation occurs between 300-900 foot-candles. Differential light requirements were found at 20° and 30°C. The optimal temperature for apparent photosynthesis in most forms is approximately 21°C. Variable photosynthesis-to-respiration ratios are recorded for the four plants at different temperatures. Eucheuma gelidium appears to be the most euryhaline of the four plants studied. The seasonal growth, occurrence, and taxonomy of the plants are correlated with their photosynthetic response.