경남 거제만 해역의 Aurelia coerulea 개체군 특성과 대량발생 원인 규명

Abstract

The southern waters of Gyeongsangnam-do have been under a jellyfish warning for more than 10 years due to the mass outbreak of Aurelia coerulea. Monthly surveys from November 2022 to October 2024 in Geoje, Southern Gyeongsangnam-do, were conducted to identify the cause of the massive outbreak of jellyfish based on the study of population characteristics of A. coerulea. The Geoje water is characterized by typical temperate region with a wide range of seasonal water temperatures. The salinity is temporarily reduced during the rainy season in summer. The water is nutritious due to the influx of nutrients from rainfall in summer. The main habitat of A. coerulea polyps was identified as artificial structures including suspended oyster farms. Polyps were attached mainly to the lower part of artificial structures because they are safe from predators, and oyster shells provide the shade they prefer. The large surface area of ​oyster shells makes an optimal habitat for polyps. The population of A. coerulea in Geoje water was characterized by large spring and overwintering populations. A. coerulea appear all year round, with the main population starting in spring, additional ones joining during summer and fall. Overwintering population survives at the low-temperature period. A. coerulea spawned monthly. The planula were significantly larger during low water temperatures, suggesting that they store energy to increase their size at low water temperatures. Planula formed polyps in water temperatures ranging from 5 to 25°C. When the foods were abundant during the ephyra stage, the initial mortality rate was low and the growth rate was high. Also, when the biomass of zooplankton was low, the growth rate of A. coerulea decreased. Zooplankton biomass was regulated by jellyfish, as predation pressure lowered zooplankton biomass during the periods of high jellyfish density. In years when foods were abundant, jellyfish grew up to 300 mm in umbrella diameter, but in years when foods were scarce, jellyfish did not grow beyond 180 mm, except for one individual that grew to 240 mm, indicating that jellyfish growth was mainly controlled by food availability.