海洋生态与环境科学重点实验室知识库

近几十年以来，受到全球气候变化以及人类活动的共同影响，全球许多高生产力海区出现大型水母数量增加、甚至暴发事件，严重威胁海洋生态系统的安全和可持续发展。大型水母生活史复杂，种群增长率高，能够快速响应生态环境的变化。作为海洋食物链的重要一环，大型水母在生态系统物质循环和能量流动的过程中扮演着重要角色。大型水母的数量变化及其在生态系统中的生态作用研究是海洋生态灾害与生态安全、海洋渔业资源变动的重要内容，也是全球关注的热点问题。我国北方近海海域是大型水母暴发的热点区域之一，本研究基于渔业底拖网获取的大型水母和渔业生物数据以及中型浮游动物网获取的浮游动物数据，构建了2021年8月和9月中国北方近海大型水母的空间分布格局及其实际生态位，分析了长江口外海海域大型水母沙海蜇数量的年际变化规律与气候因子及其潜在源地水文条件的关系，评估了沙海蜇暴发对浮游动物的摄食压力和对浮游动物丰度和群落结构组成的潜在影响，并通过生态系统Ecopath with Ecosim（EwE）模型揭示了沙海蜇在长江口外海海域生态系统食物网能量传递过程中的作用，旨在为我国乃至世界范围内大型水母种群的预测、预报及其生态作用研究提供有价值的参考。主要研究发现如下：

（1）2021年夏季中国北方近海大型水母的空间分布特征

通过渔业底拖网调查，对2021年8月和9月（夏季）中国北方近海大型水母的丰度和生物量等特征进行评估，并结合同步获取的环境数据，利用最大熵模型（MaxEnt）估算了主要大型水母种类的实际生态位。调查期间，共采集到沙海蜇（Nemopilema nomurai）、霞水母（Cyanea spp.）、海月水母（Aurelia coerulea）、多管水母（Aequorea spp.）和羊须水母（Ulmaridae，未定种）等5种大型水母。其中，沙海蜇是调查期间大型水母丰度和生物量上的优势种类，其次是霞水母和海月水母，多管水母和羊须水母仅在黄海海域部分站位零星分布。结合南黄海沙海蜇历史调查资料，2021年夏季调查海域沙海蜇种群处于中等暴发的水平。2021年夏季，我国北方近海三种主要大型水母（沙海蜇、霞水母和海月水母）在温度和盐度上的实际生态位具有很大差异，在叶绿素浓度上没有明显差异。通过对2021年8月和9月我国北方近海大型水母的空间分布格局和实际生态位的研究，为大型水母的长期变化机制研究提供数据基础，有助于了解大型水母的生物地理分布格局。

（2）影响长江口外海海域沙海蜇种群数量年际变化的环境因子

在课题组前期总结的沙海蜇生活史规律及其影响因素的基础上，基于2009年至2022年间8月长江口外海海域沙海蜇的丰度数据，结合沙海蜇潜在源地的温度、盐度、长江径流量、叶绿素浓度等因子，以及影响西北太平洋海域气候的太平洋年代际涛动（Pacific Decadal Oscillation，PDO），分析了沙海蜇种群数量波动与气候因子及潜在源地水文条件的关系。结果显示，沙海蜇潜在源地前一年适宜无性生殖过程的特定温度持续时长是影响沙海蜇种群数量波动的关键指标，温度、盐度的绝对值、长江径流量以及叶绿素浓度等与沙海蜇丰度之间没有显著的关系。具体表现为，前一年冬季低温（< 10 ℃）持续时间长，来年8月沙海蜇种群丰度水平高；春季10 – 18 ℃持续时间短，8月沙海蜇种群丰度水平高。其中，沙海蜇潜在源地前一年冬季低温持续时长能够解释沙海蜇种群丰度约66.83%的波动，可将其作为预测沙海蜇种群数量的影响因子之一。调查期间，PDO负异常阶段沙海蜇丰度水平更高，PDO通过影响沙海蜇潜在源地的水文条件，进而影响沙海蜇种群的规模。

（3）2021年和2022年夏季东海北部及黄海海域沙海蜇的摄食压力及其对浮游动物群落的影响

大型水母主要以浮游动物为食，大型水母暴发会对浮游动物产生较大的摄食压力，通过下行控制作用影响浮游动物的丰度和群落结构组成，进而影响渔业资源的可持续发展。为评估沙海蜇暴发对浮游动物的影响，本研究基于2021年和2022年8月东海北部及黄海海域的调查数据，估算了大型水母沙海蜇的摄食率、对浮游动物的摄食压力及其与浮游动物丰度和群落结构的关系。结果显示，2021年8月调查海域沙海蜇平均丰度为963.23 ± 1084.99 ind.·km^-2，显著高于2022年的94.09 ± 137.78 ind.·km^-2；浮游动物总丰度为3364.22 ± 2190.53 ind.·m^-3 ，显著低于2022年的4435.52 ± 2520.06 ind.·m^-3。2021年8月，沙海蜇对浮游动物产生较大的摄食压力，在部分沙海蜇聚集站位，其对浮游动物的摄食压力超过浮游动物生产力的100%；与沙海蜇非暴发站位相比，沙海蜇弱暴发站位和暴发站位，浮游动物的总丰度和小型桡足类的丰度出现明显的下降。结合2021年和2022年8月调查海域的沙海蜇和浮游动物数据，推测沙海蜇暴发应该是造成2021年8月浮游动物丰度更低的原因之一。

（4）通过Ecopath模型分析沙海蜇在长江口外海海域生态系统食物网能量传递过程中的作用

根据2012年至2014年间6月（春季）和8月（夏季）对长江口外海海域大型水母、渔业生物和浮游动物的调查数据，本研究通过构建生态系统Ecopath with Ecosim（EwE）模型评估了沙海蜇在该海域生态系统食物网能量传递过程中的作用。考虑到沙海蜇和其他大型水母之间的相互营养作用，本研究将沙海蜇作为单独的功能群，并且根据其摄食特征和浮游动物的生态作用，将浮游动物划分为不同的功能群。结合沙海蜇的生长发育过程，我们将春季定义为沙海蜇发展阶段，夏季定义为沙海蜇暴发阶段。结果显示，无论是发展阶段，还是暴发阶段，沙海蜇能量消耗率均高于渔业生物，占渔业生物和沙海蜇总能量消耗率的85%以上。相比饵料鱼鳀鱼和磷虾，沙海蜇消耗大量的浮游动物生产量，而通过沙海蜇传递到更高营养级的能量很少，分别占其发展阶段和暴发阶段消耗能量的0.05%和0.02%，是长江口外海海域生态系统能量的流失环节。情景分析结果表明，沙海蜇通过直接或间接的竞争，对生态系统内的其他功能群产生影响。沙海蜇暴发时，对大型浮游动物、多数浮游生活鱼类、以及其他的浮游动物食性和鱼食性鱼类产生消极影响；而沙海蜇暴发有利于鲳类生物量的增加。本研究对沙海蜇在生态系统食物网能量传递过程中作用的探索有助于了解水母在全球海洋生态系统中的生态作用。

Over the past few decades, large jellyfish blooms have been reported in many highly productive marine ecosystems, which can be attributed to the combined effects of climate change and anthropogenic activities, posing a threat to the safety and sustainable development of the marine ecosystems. Large jellyfish exhibit a complex life cycle and possess a high growth rate, enabling them to rapidly respond to changes in ecological environment within the ecosystem. As a crucial component of the marine food web, large jellyfish plays an important role in both material cycling and energy flow within the ecosystem. It is imperative to investigate the inter-annual variations in large jellyfish and their ecological role in marine ecosystem for a comprehensive understanding of marine ecological disasters, ecological safety, and sustainable utilization of marine fishery resources. The northern Chinese coastal seas have been observed to serve as one of prominent hotspots for large jellyfish blooms. Based on the data obtained from bottom trawls on large jellyfish and fishery, as well as zooplankton data obtained using zooplankton nets during the period from 2009 to 2022, this study constructed the spatial distribution patterns of large jellyfish in the northern Chinese coastal seas and estimated their realized niches during August and September 2021. Additionally, this study examined the relationship between fluctuations in the population size of large jellyfish with climate change and regional hydrological conditions. Furthermore, this study evaluated the feeding pressure exerted by large jellyfish Nemopilema nomurai on zooplankton and their relationship with zooplankton community composition. Lastly, this study explored the ecological role of N. nomurai as an energy transfer pathway within the food web in the ecosystem through Ecopath with Ecosim (EwE) models. Our research aims to provide valuable insights for predicting and forecasting the population size of large jellyfish, as well as understanding their ecological roles worldwide. The main findings were as follows.

1.  Distribution patterns of large jellyfish in the northern Chinese coastal seas during the summer of 2021

The spatial distribution patterns of the abundance and biomass of large jellyfish in the northern Chinses coastal seas were investigated during August and September (summer) of 2021 through a comprehensive fishery bottom trawl survey. By combining large jellyfish data and synchronously environmental data, the realized niches of three most abundant large jellyfish, N. nomurai, Cyanea spp., and Aurelia coerulea, were estimated through maximum entropy (MaxEnt) models. During the investigation, N. nomurai, Cyanea spp., A. coerulea, Aequorea spp., and Ulmaridae (undefined sp.) were taxonomically identified. Among them, N. nomurai was the dominant species in terms of abundance and biomass, followed by Cyanea spp. and A. coerulea. Aequorea spp. and Ulmaridae were only distributed sporadically in the Yellow Sea. Based on long-term historical data from the southern Yellow Sea, the population size of N. nomurai during the summer of 2021 was at a mid-bloom level. During the summer of 2021, the realized niches of large jellyfish exhibited substantially variations in terms of temperature and salinity, whereas for chlorophyll concentration, the realized niches were narrow and predominantly centered around intermediate environmental conditions. The investigation conducted in this study on the distribution patterns and realized niches of large jellyfish during the summer of 2021 would provide a database for studying the mechanism of long-term variations and would be helpful to understand the biogeographic distribution of large jellyfish.

2.  Inter-annual variations in the population size of Nemopilema nomurai in the offshore adjacent to the Changjiang River estuary and links to climate and regional hydrological conditions

Through controlled laboratory experiments, our research group has comprehensively summarized the life cycle of N. nomurai and identified key environmental factors that influence this process. This study examined the associations between fluctuations in the population size of N. nomurai and climate factors, as well as hydrological conditions in potential breeding place for N. nomurai, based on the abundance of N. nomurai in the offshore adjacent to the Changjiang River estuary (CE) during August from 2009 to 2022, along with temperature, salinity, runoff of the Changjiang River, and chlorophyll concentration. The results demonstrated that the duration of specific temperature suitable for the asexual reproduction process in the previous year in the potential breeding place was the crucial environmental factor influencing the fluctuations in population size of N. nomurai, while no significant relationship was observed between salinity, runoff of the Changjiang River, chlorophyll concentration and abundance of N. nomurai. Specially, a longer duration of low temperature (< 10 ℃) in the previous winter was associated with a higher abundance of N. nomurai, while a shorter duration of 10 – 18 ℃ in spring was associated with a higher abundance of N. nomurai in the following summer. Among them, the duration of low temperature in the previous winter in the potential breeding place accounted for approximately 66.83% of the fluctuation in abundance of N. nomurai, thus serving as one of the significant factors for predicting and forecasting the population size of N. nomurai. In addition, the abundance of N. nomurai was higher during the negative anomaly phase of the Pacific Decadal Oscillation (PDO) compared to that during the positive anomaly phase, and it is hypothesized that the PDO may exert an influence on the population size of N. nomurai through influencing the hydrological conditions in their potential breeding place.

3.  The feeding pressure of Nemopilema nomurai and their impacts on zooplankton community in the northern East China Sea and Yellow Sea during the summer of 2021 and 2022

Large jellyfish mainly feeds on zooplankton and plays an important role in n both material cycling and energy flow within the ecosystem. During the blooms, large jellyfish may exert greater feeding pressure on zooplankton, thereby influencing both abundance and community composition of zooplankton, subsequently affecting the sustainability of fishery resources. This study aimed to estimate the feeding rate of N. nomurai, evaluate their feeding pressure on zooplankton, and examine their relationship with zooplankton community composition to assess the impacts of N. nomurai blooms on zooplankton, based on the comprehensive survey conducted in the northern East China Sea and Yellow Sea during August 2021 and 2022. The results revealed that the mean abundance of N. nomurai was 963.23 ± 1084.99 ind.·km^-2 in August 2021, which was significantly higher than that of 94.09 ± 137.78 ind.·km^-2 in 2022. Furthermore, the total abundance of zooplankton in August 2021 was 3364.22 ± 2190.53 ind.·m^-3, which was significantly lower compared to the value of 4435.52 ± 2520.06 ind.·m^-3 observed in 2022. During August 2021, the potential consumption of zooplankton by N. nomurai was enormous and even exceeded the zooplankton production rate in regions where N. nomurai aggregated. Compared to non-bloom stations, significant reductions in both absolute and relative abundance were observed for total zooplankton and small copepods at mid-bloom and bloom stations in August 2021. The higher feeding pressure exerted by N. nomurai may be related to the lower abundance of zooplankton during August 2021 in comparison to that observed in 2022.

4.  Examining the ecological role of Nemopilema nomurai as an energy transfer pathway through Ecopath with Ecosim: a case study in the offshore adjacent to the Changjiang River estuary

Based on the surveys of fishery, zooplankton, and large jellyfish in June (Spring) and August (Summer) from 2012 to 2014 in the offshore adjacent to the Changjiang River estuary (CE), the ecological role of N. nomurai as an energy transfer pathway within the food web was evaluated through Ecopath with Ecosim (EwE) models. To consider the trophic interactions between N. nomurai and other gelatinous organisms, N. nomurai was served as a separate functional group, while zooplankton was categorized into various functional groups based on the feeding preference of N. nomurai and the ecological role of zooplankton within the ecosystem. The period was divided into two stages in accordance with the bloom-developing process of N. nomurai: the development stage (spring) and the bloom stage (summer). Nemopilema nomurai was dominant in terms of combined fish - N. nomurai energy consumption rate during both the development and bloom stage, accounting for more than 85% of total energy consumed by combined fish - N. nomurai. In comparison to forage fish anchovy and euphausiids, N. nomurai consumed a larger proportion of the zooplankton production while transferring minimal production to higher trophic levels, accounting for only 0.05% and 0.02% of the energy consumed during the development stage and bloom stage, respectively, thereby serving as a loss-pathway in the offshore adjacent to the CE. The scenario analysis revealed that fluctuations in the population size of N. nomurai exerted a significant impact on other functional groups due to the direct or indirect competition for food resources. During the blooms, N. nomurai had a negatively impact on macrozooplankton, majority pelagic fishes, and other zooplanktivorous and piscivorous fishes, whereas it exhibited a positive influence on pomfrets. This investigation into the role of N. nomurai as an energy transfer pathway in the offshore adjacent to the CE would provide valuable insights for understanding the ecological role of jellyfish across various marine ecosystem worldwide.

摘 要......................................................... I

Abstract...................................................... V

第1章 绪论.......................................... 1

1.1 研究背景................................................ 1

1.1.1 水母类研究进展............................. 1

1.1.2 中国北方近海常见大型致灾水母种类 3

1.2 研究现状................................................ 5

1.2.1 水母的年际变化特征..................... 5

1.2.2 水母在海洋生态系统中的作用..... 8

1.3 海洋生态系统食物网研究.................. 13

1.3.1 生态系统Ecopath with Ecopath模型 13

1.3.2 Ecopath with Ecopath模型在海洋生态系统中的应用........................................ 14

1.4 科学问题和研究内容.......................... 17

第2章 2021年夏季中国北方近海大型水母的空间分布特征......................... 19

2.1 材料与方法.......................................... 20

2.1.1 调查海域....................................... 20

2.1.2 大型水母的丰度和生物量........... 20

2.1.3 大型水母实际生态位................... 21

2.1.4 统计分析....................................... 22

2.2 结果...................................................... 23

2.2.1 环境变量的空间差异................... 23

2.2.2 大型水母丰度和生物量的分布... 24

2.2.3 大型水母的实际生态位............... 26

2.3 讨论...................................................... 29

2.4 小结...................................................... 32

第3章 影响长江口外海海域沙海蜇种群数量年际变化的环境因子 ................................................ 33

3.1 材料与方法.......................................... 34

3.1.1 调查海域及采样方式................... 34

3.1.2 气候指标和潜在源地环境数据... 35

3.1.3 数据分析....................................... 36

3.2 结果...................................................... 37

3.2.1 气候指标和沙海蜇丰度的年际变化 37

3.2.2 沙海蜇与潜在源地环境因子的关系 38

3.2.3 气候指标PDO与沙海蜇潜在源地温度持续时间的关系................................ 39

3.3 讨论...................................................... 40

3.3.1 沙海蜇丰度的年际变化............... 40

3.3.2 沙海蜇种群数量波动与局部海域环境因子的关系............................................ 41

3.3.3 野外沙海蜇种群数量的潜在变化机制 43

3.4 小结...................................................... 44

第4章 2021年和2022年夏季东海北部及黄海海域沙海蜇的摄食压力及其对浮游动物群落的影响............................. 47

4.1 材料与方法.......................................... 47

4.1.1 调查海域和采样方法................... 47

4.1.2 浮游动物的丰度、体积生物量和标准化体积生物量粒径谱............................ 48

4.1.3 大型水母对浮游动物的摄食压力 50

4.1.4 统计分析....................................... 51

4.2 结果...................................................... 51

4.2.1 2021年和2022年8月浮游动物空间分布和群落组成.................................... 51

4.2.2 大型水母的摄食压力及与浮游动物群落的关系................................................ 55

4.3 讨论...................................................... 59

4.3.1 2021年和2022年8月浮游动物的空间分布及群落组成................................ 59

4.3.2 大型水母的摄食压力及其与浮游动物群落组成的关系.................................... 60

4.4 小结...................................................... 62

第5章 通过Ecopath模型分析沙海蜇在长江口外海海域生态系统食物网能量传递过程中的作用...................................... 63

5.1 材料和方法.......................................... 64

5.1.1 调查海域及数据来源................... 64

5.1.2 构建不同时期食物网模型........... 65

5.1.3 数据来源....................................... 66

5.1.4 模型调试与参数检验................... 68

5.1.5 情景分析....................................... 68

5.2 结果...................................................... 73

5.2.1 沙海蜇发展阶段和暴发阶段食物网结构的差异................................................ 73

5.2.2 沙海蜇在生态系统食物网中的能量传递效率.................................................... 76

5.2.3 沙海蜇暴发阶段食物网结构的年际变化 77

5.2.4 情景分析....................................... 79

5.3 讨论...................................................... 80

5.3.1 沙海蜇暴发过程食物网结构的变化 81

5.3.2 沙海蜇在食物网能量传递过程中的作用 81

5.3.3 情景分析....................................... 82

5.3.4 缺点和不足................................... 84

5.4 小结...................................................... 84

第6章 结论与展望........................... 85

6.1 结论...................................................... 85

6.2 特色与创新.......................................... 86

6.3 不足与展望.......................................... 87

参考文献.................................................. 89

致 谢.................................................... 107

作者简介及攻读学位期间发表的学术论文与研究成果....... 109