Translocation of photosynthetic carbon from two algal symbionts to the seaanemone Anthopleura elegantissima

The intertidal sea anemone Anthopleura egantissima contains two symbiotic a lgae, zoochlorellae and zooxanthellae, in the Northern Puget Sound region. Possible nutritional advantages to hosting one algal symbiont over the othe r were explored by comparing the photosynthetic and carbon translocation ra tes of both symbionts under different environmental conditions. Each alga t ranslocated 30% of photosynthetically fixed carbon in freshly collected ane mones, although zoochlorellae fixed and translocated less carbon than zooxa nthellae. The total amount of carbon translocated to the host was equivalen t because densities of zoochlorellae were two to three times greater than w ere densities of zooxanthellae. In A. elegantissima maintained under high a nd low irradiance (100 and 10 mu mol photons/m(2)/s) at 20 degrees C and 13 degrees C for 21 days, bath algae fixed and translocated carbon at greater rates at 20 degrees C (translocation rates: 0,38 pg C /zoochlorella/h; 1.1 2 pg C /zooxanthella/h) than at 13 degrees C (translocation rates: 0.06 pg C /zoochlorella/h; 0.37 pg C /zooxanthella/h), However, zoochlorellate anem ones received 3.5 times less carbon at 20 degrees C than at 13 degrees C be cause the higher temperature caused a significant reduction in the density of zoochlorellae. Environmental variables, Like temperature, that influence the densities of the two symbionts will affect their relative nutritional contribution to the host. Whether these differences in carbon translocation rates of the two algal symbionts affect the ecology of their anemone host awaits further investigation.