温度、盐度对海月水母碟状体生长及存活的影响

Effects of temperature and salinity on the growth and survival of moon jellyfish(Aurelia coerulea)ephyrae

海月水母为我国近海主要大型灾害水母种类之一,当自然环境适宜其生长与繁殖时,易出现暴发性的增殖现象,严重破坏了我国近岸海洋生态系统的稳点与平衡。采用实验生态学方法,研究了温度(2.5、5、7.5、10、15、20、25、27.5、30℃)和盐度(15、20、25、30、35、40)对海月水母碟状体存活与生长的影响,实验共进行30d。结果显示,在实验设置的温盐范围内,温度、盐度均显著影响碟状体的存活与生长。在盐度15—35条件下,海月水母碟状体可以在温度2.5—25℃存活,在15—25℃范围内可正常生长;在温度20—25℃和盐度20—30条件下适宜海月水母碟状体生长,其中温度20℃和盐度25条件下海月水母碟状体特定生长率达到最大。与盐度相比,温度对碟状体的影响较大,在盐度15—35条件下,随着温度的升高,碟状体的伞径逐渐增大,其碟状体形态向水母体形态的转变速度加快。在达到临界点25℃时,若继续升高温度,碟状体的生存率与生长率显著下降。温度与盐度对海月水母碟状体的生存与生长具有明显的交互效应,碟状体在实验过程中表现出在较低温度条件下提高了对较高盐度的适应性。研究表明,温度、盐度的变化显著影响碟状体的生长与存活,直接导致碟状体种群数量变动,进而影响成熟水母体种群数量。结论为进一步探索大型水母暴发的生态环境机理提供重要科学依据。

Gelatinous zooplankton are recognized as key components of aquatic ecosystems,and their outbreaks have been examined in recent years.The moon jellyfish Aurelia coerulea is one of the most common gelatinous zooplankton inhabiting many parts of the world′s coastal waters,and outbreaks of this species have been reported from various regions.A key step toward better knowledge of the causes and mechanisms of mass occurrences in scyphozoan jellyfish is to assess the extent of environmentally-induced effects on the phenotype of different phases in their complex life cycle.Moon jellyfish Aurelia coerulea has been reported to have high mortality during the ephyra stage,which potentially affects the population size of the later medusa stage.The effects of the physical environment,especially temperature and salinity,are even more unclear.Laboratory experiments were carried out to quantify the extent of environmentally induced changes in Aurelia coerulea ephyrae morphology,and subsequent effects on ephyrae growth and survival,in response to temperature and salinity.We tested the effects of temperature(2.5,5,7.5,10,15,20,25,27.5 and 30℃)and salinity(15,20,25,30,35 and 40)on the survival and growth under control conditions.The experiment lasted for 30 days.Results showed that both temperature and salinity significantly affected the ephyrae development,growth and survival.In the salinity 15—35,the ephyrae could survival under 2.5—25℃,and grow in 15—25℃.The suitable temperature and salinity for the survival and growth of the jellyfish ephyrae was 20—25℃and 20—30.The bell diameter of ephyrae at 20℃and 25 was the highest.Compared with the salinity,the effect of temperature on the survival and growth of ephyrae was more significantly.In the salinity of 15—35,the bell diameter of ephyrae increased with the temperature increased and the duration of development shortened and mortality decreased as the temperature increased in 2.5℃to 25℃.There were significant interactions between temperature and salinity on the ephyrae,which manifested as with the temperature decreasing,the adaptability of ephyrae to higher salinity was enhanced.The results showed that in salinity of 40,the survival of ephyrae in lower temperature groups(2.5—15℃)were higher than those in higher temperature groups(20—30℃).In temperature 5—15℃,the specific growth rate of ephyrae was higher in salinity of 35 than those in other salinity groups,whereas the highest special growth rate was in salinity of 20 under the temperature groups 20 and 25℃.The suitable temperature and salinity in the field would therefore elevate ephyrae survival rate,accelerate individual development,and thus ensure the population size of medusae.The results will play a very important role in making clear the seasonal dynamic changes of ephyrae population and revealing the outbreak mechanism.