LAUSR

Previous study has found that microscopic epiphytic algae might be the main factor causing giant kelp mortality in an aquarium setting, but little is known about how environmental factors influence the interaction between these taxa. In this study, we examined the epiphyte density and diversity on the giant kelp Macrocystis pyrifera over a 6-month period in an aquarium setting and compared them to those of epiphytes grown on glass slides. Physico-chemical parameters such as temperature, irradiance, and nutrient levels were also measured. The results indicated that epiphyte densities were low on kelp blades 2 months after their introduction into the tank (Wk8, 14 × 103 cells cm−2) but significantly higher thereafter, as compared to high epiphyte densities on the glass slides since Wk2 (509 × 103 cells cm−2). The diversity of the epiphyte community fluctuated on the kelp blades, but increased steadily on the glass slides. Spearman’s correlation analysis between epiphyte density and physico-chemical variables revealed that increased temperature was the most important factor in influencing epiphyte density on kelp blades, possibly contributing to the deterioration of the giant kelp.