Ecological studies of economic red algae. I. Photosynthesis and respiration of Chondrus crispus Stackhouse and Gigartina stellata (Stackhouse) Batters

The photosynthesis and respiration of Chondrus crispus Stackhouse and Gigartina stellata (Stackhouse) Batters are recorded under a variety of light intensities, temperatures, salinities, and degrees of desiccation. The apparent photosynthesis (uncorrected for plant respiration) of C. crispus is light-saturated at ~ 1000 ft-c, that of G. stellata at ~2100 ft-c. The optimal temperature for photosynthesis in both species is ~20 °C, but they have a high photosynthetic capacity over a wide range of temperatures. The respiration of C. crispus and G. stellata is relatively uniform from 8–20 °C. Both species have maximum photosynthesis/respiration ratios at 20 °C. C. crispus showed its maximum photosynthesis and minimum respiration at a salinity of 24‰; G. stellata exhibited maximum photosynthetic and reduced respiration rates at 40%.. The apparent photosynthesis and respiration of C. crispus are adversely affected by a high degree of dehydration, while G. stellata is more flexible. The local abundance and distribution of C. crispus and G. stellata are correlated with their photosynthetic responses