海洋生态与环境科学重点实验室知识库

本研究基于2014年2月、5月、8月、11月长江口及其邻近海域生态系统调查数据构建该海域生态通道模型（Ecopath），解析生态系统结构与功能，运用多种模型参数评估方法，综合评估模型的精确度和敏感性，探讨了2014年长江口及其邻近海域生态系统营养结构、能流特点、生态系统整体状况，对比分析了1985-1986年、2004年和2014年三个时期该海域功能群结构及其动态，讨论了该海域不同时期功能群间相互作用和生态系统总体特征变化，具体如下：

（1）功能组划分基于不同物种的生态位特征进行，并参考了渔业资源经济价值和科学研究侧重点。本研究共划分了23个功能组，具体为9个鱼类功能组、3个底栖生物功能组、海鸟、鲨鱼、海龟、头足类、虾类、蟹类、水母、浮游动物、浮游植物、底栖生产者和碎屑。通过食物组成矩阵的分层聚类分析探讨不同功能组之间的营养关系；运用Link提出的一系列生态通道模型先前检验的步骤进行模型输入参数的整体检验；运用敏感性分析研究不同模型评估参数对输入参数的敏感性；运用基于生态学原理、质量守恒和热力学定律的6个模型参数平衡模型。

（2）2014年长江口及其邻近海域生态系统功能组营养级在1-4.361之间，其中9个鱼类功能组营养级为3.046-4.361，平均营养级为3.515。渔业资源功能组平均生态营养效率为0.845。生态系统总能流为12217.660 t∙km^-2∙a^-1，系统净生产量为1332.859 t∙km^-2∙a^-1。除去碎屑，其他功能组总生物量为94.336 t∙km^-2∙a^-1。渔业捕捞对底层混合食性鱼类和中下层鱼类有明显的消极影响，水母和浮游动物存在明显的捕食、竞争关系，水母对初级生产量有一定的截留作用。来源于碎屑的初级生产量对于中下层和底层鱼类具有明显的支撑作用。EcoTroph模型结果显示，渔业压力对营养级大于3.1的功能组具有明显的消极影响。

（3）对比分析1985-1986年、2004年和2014年三个时期的长江口及其邻近海域能流网络，解析生态系统内部不同功能组之间各参数的对应关系。生物量先上升、再下降或者生物量一直处于下降状态的功能组通常面临崩溃，功能组生物量一直增加往往预示着生态系统结构的异常。2004年各个功能组渔获物在三个时期中是最高的，各个功能组的渔获量总体上都高出1985-1986年数倍，2014年各个功能组渔获物均大幅度减少，除了底层混合食性鱼类的渔获量仍然大于1985-1986年水平，其他功能组的渔获量均低于1985-1986年水平。2014年整体杂食性有所升高，中下层和底栖鱼类的食物组成营养级有所下降—由第四营养级向第三营养级转变。

（4）在1985-1986年、2004年和2014年三个时期，长江口及其邻近海域中起关键作用的功能组前五位均包括浮游动物。2004年蟹类和底层鱼类的关键性指数降低，中上层浮游生物食性鱼类的关键性指数升高。2014年虾类和蟹类的关键性指数降低，中上层浮游生物食性鱼类依旧有着很高的关键性指数，底栖生物在能流转换中的作用也突显出来。该海域各时期系统总流量中，消费量占比2014年最高，2004年最低。2004年该海域生态系统面临巨大的渔业压力，导致生态系统群落结构发生较大变化，生态系统趋于不成熟，抗击外界干扰的能力下降。2014年该状况相较于2004年有所缓解，生态系统成熟度有所恢复，能流网络结构冗余较多，渔业产出能力远低于以往水平。

An Ecopath model is constructed with comprehensive assessments of accuracy and sensitivity, based on the quarterly survey of the Yangtze estuary and its adjacent waters in February, May, August and November 2014. Noteworthy aspects are analyzed, including trophic structure, energy flow characteristics and overall ecosystem status of the estuarine ecosystems in 2014; The dynamic evolution of taxa groups’ structure and their energy flow networks in the three periods (1985-1986, 2004 and 2014) are compared and analyzed. The interactions between taxa groups and overall ecosystem status in the three historical periods of the sea area are discussed, as follows.

(1) Taxa groups is divided based on the niche characteristics of different species, meanwhile referring to the economic value and research focus of fishery resources. The entire community are divided into a total of 23 taxa groups. More specifically, there are 9 fish groups, 3 benthic groups, seabirds, sharks, turtles, cephalopods, shrimps, crabs, jellyfish, zooplankton, phytoplankton, benthic producers and detritus. Exploring the nutritional relationship between different taxa groups through the hierarchical cluster of the diet composition matrix to; Using the “rules of thumb” to run the overall test of the model input parameters; Analyzing the sensitivity of estimate parameters to input parameters; based on six parameters of ecological principles, mass conservation, and thermodynamic laws to balance the model.

(2) In 2014, the trophic level of each taxa group of the Yangtze estuary and its adjacent waters ecosystem was between 1-4.361; the trophic level of the nine fish functional groups was 3.046-4.361, and the average trophic level was 3.515. The average ecotrophic efficiency of the fishery functional group was 0.845. The total energy flow of the ecosystem was 12217.660 t∙km^-2∙a^-1, and the net production of the ecosystem was 1332.859 t∙km^-2∙a^-1. Total biomass without detritus was 94.336 t∙km^-2∙a^-1. Fishing had a significant negative impact on demersal mix-feeding fish and benthopelagic fish. Jellyfish and zooplankton had obvious predation and competition with each other, and Jellyfish had a certain retention effect on energy flow. Primary production from detritus had a significant supporting effect on benthopelagic and demersal fish. The EcoTroph model illustrated the strong negative impact of fishing on functional groups with a trophic level greater than 3.1.

(3) The study compared the energy flow networks and the correspondence between various parameters among different functional groups of the Yangtze estuary and its adjacent waters in the three periods of 1985-1986, 2004 and 2014. The results shows that the taxa groups, whose biomass rose first then fell or biomass declined consistently, were usually facing a collapse. The ever-increasing biomass of the functional group often indicates the occurrence of ecological disasters. The catch in 2004 was the highest in the three periods, which was several times higher than that in 1985-1986. In 2014, the catch was significantly reduced, except that the catch of demersal mix-feeding fish was still higher than the level of 1985-1986. In 2014, the overall Omnivory increased, and the prey trophic level of benthopelagic and demersal fish decreased, shifting from the fourth trophic level to the third trophic level in general.

(4) Zooplankton was included in the taxa groups with high keystone index in 1985, 2004, and 2014. In 2004, the criticalities of crabs and demersal fish were reduced, and that of pelagic planktonic fish was increased. In 2014, pelagic planktonic fish were still highly critical, however shrimps and crabs were reduced, and the role of benthos in energy flow conversion was also highlighted. Among the total system flows in each period of the estuarine area, consumption accounted for the highest in 2014 and lowest in 2004. In 2004, the huge fishing pressure faced by the marine ecosystem caused great changes in the ecosystem structure, the ecosystem became immature, and the ability to resist external disturbances declined. In 2014, the situation was relieved compared with 2004. The ecosystem maturity had recovered, the energy flow network was more redundant, nevertheless the fishery output capacity was far lower than the previous level.