Institutional Repository of Key Laboratory of Marine Ecology & Environmental Sciences, CAS
|Place of Conferral||中国科学院海洋研究所|
|Keyword||水母暴发 水螅体 碟状体 底栖动物 生物因子|
以中国近海十分常见的三种大型水母沙海蜇（Nemopilema nomurai）、海月水母（Aurelia coerulea）和海蜇（Rhopilema esculentum）的水螅体为研究对象，对这几种水母水螅体的种间捕食与被捕食关系进行了研究。海月水母的水螅体群落在沿岸地区被广泛发现，而沙海蜇和海蜇的水螅体栖息地却仍未可知，这个问题也是国际水母研究中普遍存在的问题，或者说是世界难题——很多大型水母的水螅体在自然环境中很难找到,个体小、受到扰动就会剧烈收缩应该是造成这种状况的主要因素。从生态位的角度来看，三种水母在中国近海存在空间和时间上的重叠，为评估三种常见大型水母水螅体的空间分布模式，通过人工繁殖的方式，按照水螅体附着先后顺序的不同和身体大小的差别对三者的捕食与被捕食关系进行了研究。结果发现，海月水母的水螅体能够捕食沙海蛰的水螅体和比自己身体小的海蜇水螅体；先前已经附着的海蜇水螅体能够捕食后来附着的、比自身个体小的沙海蜇水螅体。依据上述实验结果，我们可以推测在海月水母水螅体的栖息地，沙海蜇水螅体很难得到大的发展，这使我们对于在近海海月水母分布区难以发现沙海蛰水螅体的现象获得了生物控制方面的证据。由于海月水母水螅体分布在20 m水深以浅的自然海域，因此我们推测沙海蜇水螅体群落可能存在于水深大于20 m的海域，今后搜寻沙海蜇水螅体时应该对20 m以深的海域进行侦查，也有待研发更为先进的水螅体探测设备和方法。沙海蜇水母体分布在水深20米以深的海域，这可能与其水螅体分布深度是一致的。海月水母水螅体对其他种水母水螅体侵略性的捕食作用，对其他种类的水母的暴发能够产生控制作用。
水螅体的数量受到其他生物捕食作用的影响，而且前人的原位模拟实验结果表明，不同种水母水螅体暴露在相同的底栖动物群落时，存活率呈现不同的变化趋势。为查明对底栖水螅体有捕食作用的关键捕食者，并评估捕食者对不同种水母水螅体捕食率的差异，利用不同的采样方法，收集到中国近海39种不同的底栖动物，开展了对沙海蜇、海蜇和海月水母水螅体的捕食测试实验，并测定了捕食者对这三种水母水螅体的捕食率。结果表明，有7种底栖动物能够直接捕食或者摄食水螅体，包括3种软体动物海牛类扁脊突海牛（Okenia plana）、蓝无壳侧鳃（Pleurbranchaea novaezealandiae Cheeseman）和网纹多彩海牛（Chromodoris tinctoria），以及四种海葵，中华近丽海葵（Paracalliactis sinica）、多孔美丽海葵（Calliactis japonica）、不定侧花海葵（Anthopleura incerta）和绿侧花海葵（Authopleura midori）。这些生物对三种水母水螅体都有捕食作用，但是捕食效率不同，捕食率与捕食者的体长正相关。水母水螅体在以海牛类和海葵类为优势种的海区存在的可能性很小，在以甲壳类、棘皮动物和腹足纲螺类等其他种类为优势种的海区存在的可能性较大，这为了解底栖生物种类和数量变动与水母暴发之间的关系提供了有力证据，也为水母防控策略的制定提供了科学依据。水母水螅体的种群数量受到底栖动物群落的下行生物控制作用，这种控制作用强度与不同海域底栖动物的群落结构特征关系密切。
水母碟状体是无性世代与有性世代进行交替的转换环节，是水母幼体的一个非常重要的阶段。前人的研究表明新释放的碟状体会沉入海洋底层优先与底栖动物群落接触，室内观察实验也表明新释放的碟状体生命体征较弱并会沉入底层；另一方面，前人的野外实验表明水螅体横裂释放的碟状体的死亡率极其高，而碟状体高死亡率的原因尚不明确。本研究以海月水母碟状体为材料，初步探究了底栖动物对其的捕食作用。实验结果发现，双斑蟳（Charybdis bimaculata）、显著琼娜蟹（Jonas distincta）、虻鲉（Erisphex pottii）和中华近丽海葵（Paracalliactis sinica）能够大量捕食海月水母的碟状体，其捕食率与捕食者的体长呈显著线性正相关。这表明生活在近海底的动物对水母碟状体的下行生物控制作用可能是导致碟状体高死亡率的重要生物因子。近年来中国近海底栖动物群落呈现衰退的趋势，这可能降低了底栖动物群落对水母碟状体的下行生物控制作用，为水母的暴发提供了有利条件。逐步恢复底栖动物群落，可对控制水母暴发起到积极作用。
Jellyfish blooms have aroused public attention worldwide and have caused serious problems to tourism, fisheries, coastal industries, and the marine ecosystem. Jellyfish bloom is affected both by physical and chemical factors and biological factors. Comprehensive researches have been conducted on physical and chemical factors in many previous studies. However, there are still some deficiencies in study of biological factors. It is well known that the life cycle of scyphozoan jellyfish is composed of a sexual pelagic medusa stage and a asexual benthic polyp stage, and the ephyrae stage is the transition stage of asexual reproduction and sexual reproduction. The polyp stage and ephyrae stage are collectively referred to as larval stage. Asexual reproduction and strobilation of the polyps determines directly the number of pelagic medusae; thus, the larval stage is the key to understand the population dynamics of medusae. In order to comprehensively evaluate the biological control factors of jellyfish bloom, it is necessary to study the interaction of different species of jellyfish at different life cycle stages and the influence of other organisms on jellyfish at different life cycle stages, including the following aspects: the interspecific predator-prey relationship of different species of jellyfish at different life cycle stages, competition and predation relationship between other benthos and benthic polyps, competition and predation relationship between other organisms and ephyrae, and competition and predation relationship between other organisms and planktonic jellyfish. In this study, the interspecific predator-prey relationship was explored, main predators of polyps of giant jellyfish in Chinese coastal waters were identified and their predation rates were determined, the predation of other organisms on the ephyrae was preliminarily discovered. The details were as follows:
Nemopilema nomurai, Aurelia coerulea, and Rhopilema esculentum are three scyphozoan jellyfish commonly appeared in Chinese coastal waters. Polyps of Aurelia coerulea had been found along coastal waters wildly, while the natural habitats of polyps of N. nomurai and R. esculentum had not been confirmed. This problem is also a common problem in international jellyfish research, or a worldwide problem. Polyps of many jellyfish species are difficult to find in natural environment. The small size of the polyps and severe contraction when disturbed should be the main reason. The distribution characteristic of the medusa indicated that the polyps of all three species may occur together. To explore intraguild predation by the polyps of these three species and further evaluate the distribution pattern of polyps of the three species, a laboratory experiment considering the attachment sequence and size relationship of calyx diameter of the polyps by artificial breeding was conducted. The results showed that the polyps of Aurelia coerulea could prey on polyps of N. nomurai in all treatments, polyps of A. coerulea could prey on polyps of R. esculentum which were smaller than polyps of A. coerulea. Polyps of R. esculentum could prey on the polyps of N. nomurai only when polyps of R. esculentum attached first and were bigger than those of N. nomurai. Consequently, we conjectured that colonies of N. nomurai polyps were hard to form and expand the population size in places inhabited by A. coerulea polyps. In addition, it was well known that polyps of A. coerulea inhabited at depths of less than 20 m in coastal sea, thus, we speculate that colonies of N. nomurai polyps might occur at depths of more than 20 m. Future studies should search for the polyps of N. nomurai at greater depths and more advanced underwater detection equipment needs to be introduced. Our finding that polyps of Aurelia coerulea aggressively preyed on polyps of other species may help understand other such systems of jellyfish bloom in the world, which might biological control bloom of other jellyfish species.
The number of polyps of jellyfish was affected by predation of other organisms, and in situ simulation experiments showed that the number of polyps of different species had shown different trends when exposed to the same benthic community. A total of 39 species of benthos were collected by different sampling methods from the coastal waters in China and predation experiments were carried out on the polyps of Nemopilema nomurai, Aurelia coerulea, and Rhopilema esculentum. The results showed that 7 species of macrobenthos could directly prey on or feed on polyps, including 3 species of sea slug Okenia plana, Pleurbranchaea novaezealandiae Cheeseman, Chromodoris tinctoria and 4 species of anemones Paracalliactis sinica, Calliactis japonica, Anthopleura incerta, Authopleura midori. These species of macrobenthos could prey on polyps of Nemopilema nomurai, Aurelia coerulea, and Rhopilema esculentum. However, the predation rate on the polyps differred among polyps of different species, the predation rate was positively correlated with the body length of the predators. The polyps might be rarely found in the sea areas dominated by sea slug and anemones, it was more likely to exist in the sea areas dominated by other species, such as crustaceans, echinoderms and gastropods. This might provide theoretical basis for understanding the relationship between the jellyfish bloom and the species and quantity changes of benthos, and for the formulation of prevention and control strategies for jellyfish bloom. The population size of polyps was affected by the biology control of the benthos community, and also depended on the specific community structure characteristics of benthos in different sea areas.
The stage of ephyrae is the transition stage of asexual reproduction and sexual reproduction. The newly released ephyrae always sinked to the bottom of the ocean and contact with the benthic community preferentially, and this phenomenon was confirmed by indoor observation experiments. On the other hand, previous studies showed that the mortality of newly released ephyrae was extremely high, and the reason was not clear. In this paper, a preliminary study was conducted to explore the predation of macrobenthos on the ephyrea. The results showed that Charybdis bimaculata, Jonas distincta, Erisphex pottii and Paracalliactis sinica were able to prey on the ephyrae of Aurelia coerulea, and the predation rate was positively correlated with the body length of the predators. The downward biological control of benthos on jellyfish ephyrae might be an important biological factor leading to high mortality of jellyfish ephyrae. In recent years, the zoobenthos community in the coastal waters of China has been declining, which might reduce the downward biological control of the jellyfish ephyrae, and therefor provide favorable conditions for the outbreak of jellyfish. The gradual restoration of zoobenthos community structure may be very important in controlling the outbreak of jellyfish.
The number of jellyfish was affected by the competition and predation of fishery organisms. To evaluate the relationship between jellyfish numbers and fishery organisms, it was necessary to analyze the variation characteristics of jellyfish population and the community structure characteristics of fishery organisms. Take the Yangtze Estuary as an example, The data of fishery resources species collected from bottom trawl surveys from the Yangtze River estuary and its adjacent waters in June, 2015 was used to analyze the composition, dominant species, community diversity characteristics and community structure. Previous researchs found that silvery pomfret, Navodon septentrionalis, Stephanolepis cirrhifer, pagrus sp., and salmon were important predators of jellyfish. Further research should focus on exploring the relationship between the changes of species, population size, temporal and spatial distribution of these key fish and the population dynamics of jellyfish.
|Funding Project||National Basic Research Program (973 program) of China[2011CB403604] ; National Key Research and Development Program of China[2017YFC1404405] ; Strategic Priority Research Program of the Chinese Academy of Sciences[XDA11020305] ; Qingdao National Laboratory for Marine Science and Technology[2016ASKJ02] ; Qingdao National Laboratory for Marine Science and Technology[2016ASKJ02] ; Strategic Priority Research Program of the Chinese Academy of Sciences[XDA11020305] ; National Key Research and Development Program of China[2017YFC1404405] ; National Basic Research Program (973 program) of China[2011CB403604]|
|Table of Contents|
|汤昌盛. 大型水母幼体阶段的生物控制研究[D]. 中国科学院海洋研究所. 中国科学院大学,2020.|
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