Effects of green tide formed by free-floating Ulva species on ecological functions in tidal flats

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In order to evaluate the quantitative effects of the green tide formed by Ulva species on an ecosystem function in the tidal flat, Yatsu tidal lagoon where the green tide developed throughout the year was selected. By applying a newly developed molecular identification method, we found Ulva ohnoi, which is considered as invasive species, is the dominant species in the tidal. Large accumulation of U. ohnoi was observed from spring to early summer, but was sharply declined in midsummer. The biomass was recovered in fall, and reached its maximum in winter. Indoor culture assays showed that relative growth rate at a higher temperature in U. ohnoi was higher than that in native species U. pertusa. Both species did not grow at the water temperature correspond to that in winter. Analyses of surface water reveal that green tide has important ecological functions in nutrients and carbon cycle.