Testing the Influence of Previous-Year Temperature and Food Supply on Development of Nemopilema Nomurai Blooms

Blooms of Nemopilema nomurai medusae have plagued East Asian coastal waters during the last decade. Recent studies indicate that the benthic polyp phase is important for reproductive potential and survival in scyphozoans. We investigated the effects of temperature and food on the development of N. nomurai polyps in the laboratory in Dalian, China. First, polyps were exposed to temperatures of 2.5–27.5°C in 2.5°C intervals. Next, we assessed the long-term cold tolerance by subjecting polyps to 0°C for 90 days. Third, we tested polyps in 16 combinations of temperature (8, 12, 16, and 20°C) and food supply (0.42, 1.25, 2.08, and 2.91 μg C polyp−1 day−1). Our results showed that N. nomurai polyps can survive from 0 to 27.5°C and overwinter without feeding. Production and excystment of podocysts did not occur at temperatures below 10°C. Somatic growth, podocyst-formation, and excystment increased with increasing temperature and were dramatically affected by food supply at warmer temperatures. Thus, warm temperatures (15–27.5°C) and abundant plankton biomass during the previous season should result in high productivity of polyps and significantly contribute to blooms of N. nomurai the following year.