Characteristics of Jellyfish Community and their Relationships to Environmental Factors in the Yangtze Estuary and the Adjacent Areas after the Third Stage Impoundment of the Three Gorges Dam

Abstract Over the last decade, a significant increase in jellyfish blooms has been observed worldwide in marine ecosystems and is becoming seen as an indicator of a state shift in pelagic ecosystems. As large jellyfish blooms may have detrimental effects on fishery resources and ecosystem functioning. It is scenically valuable to understand the factors leading to jellyfish assemblage. Based on the survey of hydro-environmental parameters and jellyfish information in the Yangtze River Estuary in 2010-2011, spatial distribution of jellyfish was characterized, and then its relationships with environmental factors were analysed by employing Biota-Environment matching (BIOENV). There were totally 17 species, including 10 species of Hydrozoa, 4 species of Siphonophora and 3 species of Ctenophore, respectively. Muggiaea atlantica in spring, Diphyes chamissonis in summer and autumn were absolutely dominant species. Seasonal change of averaged abundance of jellyfish was in following order: summer (24 ind. •·m -3 ) > spring (20.8 ind. •·m -3 ) > autumn (7.6 ind. •·m -3 ); and it is summer (0.86) > spring (0.8) > autumn (0.52) for their diversity. The primarily important environmental factor impacting on jellyfish assemblage was temperature, silicate and dissolved inorganic nitrogen for the whole year.