Effect of Epiphytic Algae on Photosynthetic Function of Potamogeton crispus

The effect of blooming epiphytic algae on the leaf traits and photosynthetic function of the submersed macrophyte Potamogeton crispus was investigated under different epiphytic conditions and nutrition levels. Epiphytic algae growth was promoted at a rate of 0.16 chl a μg.cm −2 .d −1 on leaf surface area under eutrophic conditions (N: 1 mg.L −1 ; P: 0.1 mg-L −1 ) and at a rate of 0.004 chl a μg-cm −2 .d −1 under mesotrophic conditions (N: 0.1 mg-L −1 ; P: 0.01 mg-L −1 ). In the presence of the algae eaters Macrobrachiurn nipponense and Radix auricularia, the growth of epiphytic algae was markedly suppressed. In the absence of algae eaters, the growth of epiphytic algae for 42 days under the eutrophic and hypereutrophic conditions resulted in 25.2% of decrease of chl a, more than 50% decrease of the electron transport rate, harmful change in content of leaf nitrogen, photosystem II activity and photochemical quenching, and a lower production in the plant.