High density aggregations of the Aurelia sp 1 ephyrae in a Chinese coastal aquaculture pond

Abstract

Blooms of the Moon Jellyfish Aurelia sp.1 medusae have occurred in the harbors and coastal waters of the Bohai and Yellow Seas. However, the occurrence and distribution of Aurelia sp.1 ephyrae is relatively unknown. Mass occurrence of scyphozoan ephyrae in a coastal aquaculture pond (Shidao) in northern China was first recorded in April 2015. Based on morphological characteristics, the ephyrae collected in the aquaculture pond were mostly similar to the ephyrae collected in Atlantic French waters, which were identified as Aurelia sp.1. This was further confirmed by phylogenetic analyses of the mtDNA 16S regions of the sampled ephyrae. Surprisingly, the blooms of Aurelia sp.1 ephyrae formed an obvious reddish color similar to red tides in the surface water of the aquaculture pond. The mean density of ephyrae in the reddish color zone of the aquaculture pond was estimated to be 7.38 x 10(6) individuals m(-3). Seawater temperature and wind are the key factors for the formation of Aurelia sp.1 ephyra bloom in the aquaculture pond. Finally, we speculate that artificial structures may provide more substrates for the polyps and enhance the Jellyfish blooms in Chinese aquaculture ponds.