Abstract: Global climate change and human activities affect nitrogen nutrient and salinity in coastal waters. Ulva pertusa, a dominant species in the coastal waters of temperate zones, will grow faster under eutrophication conditions, with negative impacts on marine ecosystems. In this study, the coupling effects of nitrogen content and salinity of seawater on U. pertusa were examined in laboratory experiments. The results showed that nitrogen and salinity had significant synergistic effects on the biomass of U. pertusa. Under high salinity (40) condition, U. pertusa showed high biomass, whereas nitrogen enhancement led to lower biomass. C, N concentrations and C/N ratio in U. pertusa tissues did not correlate with seawater N concentration, but correlated with seawater salinity. Our results provide a basis for the mechanism and scientific management of macroalgae blooms in eutrophication water under the background of global climate change.

Key words: Ulva pertusa, nutrient, salinity, synergistic effect.