effect of feeding on repopulation of the sea anemone Aiptasia pallida by symbiotic dinoflagellates (zooxanthellae)

Many marine organisms possess endosymbiotic dinoflagellates called zooxanthellae. Bleaching is the loss of zooxanthellae, but bleached hosts can be repopulated. Little is known about how repopulation is controlled. The sea anemone Aiptasia pallida was used to study the effects of feeding on repopulation. Two groups of aposymbiotic anemones were reinfected with algae from symbiotic clones. One group was fed and the other starved, and counts of algae within each anemone were made at 3 day intervals for 6 weeks. The experiment was repeated, and results showed that the rate of algal growth did not differ between fed and starved groups. However, starved anemones reached plateau more quickly and lost algal cells after plateau was reached, whereas fed anemones contained more algae and protein. This suggests that starved anemones can support an algal population initially, but cannot maintain it. Space and nutrients are implicated in having a limiting effect on maintenance of symbionts.