北部湾生态通道模型的构建

根据1997年～1999年在北部湾进行的渔业资源和生态环境调查数据,利用EwE软件构建北部湾生态系统的营养通道模型,模型由16个功能组构成,包括了哺乳动物和海鸟,每一组都代表在生态系统中具有相似地位的有机体,基本覆盖了北部湾生态系统能量流动的主要过程.模型分析表明,北部湾生态系统的能量流动主要以捕食食物链途径为主,其中无脊椎动物在能量从低级向高层次转换中起关键作用.各功能组的营养级范围为1.00～4.04,哺乳动物占据了最高营养层.生态网络分析表明,系统的能量流动主要有6级,来自初级生产者的能流效率为12.2%,来自碎屑的转换效率为12.3%,平均能量转换效率为12.2%.模型估算的可利用的生物量密度为8.7 t·km^-2,生态系统的生物生产量只占系统净初级生产力的1.81%.当前北部湾海洋生态系统处于不稳定状态.     

基于Ecopath模型的崂山湾人工鱼礁区生态系统结构和功能研究

基于2014—2016年青岛崂山湾人工鱼礁区的生物资源调查数据,利用Ecopath with Ecosim(EwE)软件构建崂山湾人工鱼礁区生态系统生态通道模型(Ecopath),系统分析了崂山湾人工鱼礁区生态系统的能量流动规律和结构特征,估算了栉孔扇贝的养殖容量。该模型由17个功能组组成,基本涵盖了崂山湾人工鱼礁区生态系统能量流动的主要过程。生态网络分析表明,生态系统各功能组的营养级范围为1.0—4.255,星康吉鳗占据了营养级的最高层。能量流动主要有5级,各营养级平均能量传递效率为10.8%,其中来自初级生产者的能量效率为9.8%,来自碎屑的传递效率为10.9%;系统总流量为14256.510 t km~(-2) a~(-1),其中68%的能量来自碎屑供给;系统的总初级生产量/总呼吸量为1.127,系统联结指数为0.293,杂食指数为0.333,表明崂山湾人工鱼礁区生态系统成熟度较高,食物网结构较复杂,系统内部稳定性较高。关键种指数分析结果显示,许氏平鲉具有较高的关键指数和相对总影响,表明其可能在当前生态系统中扮演重要的生态角色。吊笼养殖栉孔扇贝生态容纳量为189.679 t/km~2,在维持生态系统平衡和稳定的前提下,当前现存量最大可增加18.55%。     

基于生态通道模型的长江口水域生态系统结构与能量流动分析

利用Ecopath with Ecosim在前期研究的基础上构建了3个时期(2000年秋、2006年秋、2012年秋)长江口水域生态系统的生态通道模型,分析对比了三峡工程蓄水前中后期,长江口水域生态系统结构与能量流动特征。模型将长江口水域生态系统划分为鱼类、虾类、蟹类、头足类、底栖动物、浮游动物、浮游植物、碎屑等17个功能组,基本覆盖了长江口生态系统能量流动的主要途径。模型结果分析表明:蓄水前中后期,长江口水域生态系统各功能组营养级组成和分布相近,但由于长江口渔业过度捕捞,蓄水中后期多数功能组的生态营养转换率被动提高。长江口渔获物的组成未发生明显变化,但渔获物的平均营养级降低,渔获量减少。蓄水中后期,生态系统中牧食食物链的重要性增加,碎屑食物链的重要性降低,这与蓄水之后长江入海径流改变、泥沙量减少、陆源污染增加关系密切。结果表明,蓄水前中后期,生态系统均处于不成熟阶段,蓄水后生态系统总生物量、初级生产量及流向碎屑的能量呈降低趋势,但系统的净效率和再循环率升高。     

基于Ecopath模型的三门湾生态系统结构与功能

生态系统的结构决定生态系统的物质循环、能量流动和系统功能。本研究采用Ecopath模型,根据2017—2018年中国东海三门湾海洋生态实地调查数据,构建了三门湾生态系统的生态通道模型,描述了三门湾生态系统的能流结构,分析了其功能特征。结果显示: 三门湾生态系统营养级范围在1~3.80,能流渠道主要表现为牧食食物链,系统能流结构主要集中在前5个等级,系统平均能量传递效率为13.0%,系统初级生产者的能量传递效率为12.8%,系统碎屑的能量转换效率为14.5%。系统连接指数与系统杂食性指数分别为0.40和0.24,Finn循环指数为0.40,系统的Finn平均路径长度为2.06,总初级生产量与总呼吸量之比为13.59,表明当前三门湾生态系统处于不成熟阶段。本研究有助于理解中国近海港湾生态系统的结构特征和功能特点。     

基于Ecopath模型的荣成俚岛人工鱼礁区生态系统结构和功能评价

基于2009年在荣成俚岛人工鱼礁区进行的周年生物资源调查数据,构建了俚岛人工鱼礁区生态系统生态通道模型(Ecopath),系统分析了俚岛人工鱼礁区生态系统的能量流动规律和系统结构特征.该模型由19个功能组构成,基本涵盖了俚岛人工鱼礁区生态系统能量流动的主要过程,根据礁区调查出现的鱼类与鱼礁的对应位置关系划分功能组,并引入浮游异养细菌功能组.结果表明:礁区调查出现的鱼类可划分成7个功能组,系统中各功能组的营养级在1.00 ～ 3.72级,其中,礁区I型鱼类处于最高营养级;系统总流量为10786.68t·km-2·a-1,其中,27％流向碎屑,17％以捕捞和沉积的形式流出系统;系统的总初级生产力为4131.97 t· km-2·a-1;系统的总能量转换效率为10.5％,流量中来自碎屑的比例为39％,61％直接来源于初级生产者,能流通道以牧食食物链为主导;系统的总初级生产量/总呼吸量为1.84,系统连接指数为0.20,Finn循环指数为4.5％,能流平均路径为2.62.俚岛人工鱼礁区生态系统当前的成熟度和稳定性较低,是一个正处于发育阶段的生态系统,系统抵抗外界干扰的能力较弱,鱼礁区的生态环境和渔业产出在年际间会出现一定波动,人工鱼礁对生态环境的修复作用需要继续养护才能得以实现.     

南海北部生态系统食物网结构、能量流动及系统特征

根据20072008年在南海北部(107°00'120°00'E、17°00'23°30'N)进行的海洋生态综合调查数据,应用Ecopath with Ecosim软件构建了南海北部生态系统的生态通道模型,并通过模型分析了南海北部海洋生态系统的食物网结构、能量流动和系统的总体特征,并简要总结过度捕捞生态系统的基本特征。结果表明,南海北部海洋生态系统以捕食食物链为主要能流通道,初级生产者是系统能量的主要来源。各功能群的营养级范围为13.99,哺乳动物占据了最高的营养层,平均渔获物营养级为2.93。利用生态网络分析,系统的能量流动主要有6级,来自初级生产者的能流效率为12.6%,来自碎屑的转换效率为10.4%,平均能量转换效率为11.5%。系统连接指数(Connectance Index,CI)和系统杂食指数(System Omnivory Index,SOI)分别为0.290和0.239;Finn’s循环指数(Finn’scy cling index,FCI)和系统平均路径长度(Finn’s mean path length,MPL)分别为4.380和2.476;总初级生产力/总呼吸为2.596,综合研究表明当前南海北部海洋生态系统处于不成熟阶段。     

基于Ecopath模型的胶州湾生态系统结构和能量流动分析

根据2015—2016年在胶州湾进行的渔业资源与生态环境调查数据,利用Ecopath with Ecosim 6.5(Ew E)软件构建了胶州湾生态通道模型,分析了现阶段该海湾生态系统营养结构、能量流动过程和生态系统总特征。结果表明:胶州湾生态通道模型共由21个功能组组成,各功能组营养级范围为1~4.383,渔获物平均营养级为2.023,以菲律宾蛤仔(Ruditapes philippinarum)为主;胶州湾生态系统的能量流动主要以牧食食物链为主,占系统能量来源的59%。生态网络分析表明:系统能量主要分布在6个营养级,来源于初级生产者的能量转化效率为16.22%,来自碎屑的转化效率为15.76%,系统平均转化效率16.35%。胶州湾生态系统总初级生产力与总呼吸量的比值为2.518,系统处于不成熟状态。     

基于营养通道模型的渤海生态系统结构十年变化比较

根据1982年和1992年渤海渔业资源和生态环境调查数据,应用EwE建模软件,构建了两个时期的营养通道模型,并比较分析了10a间渤海生态系统结构以及渔业资源的变化.模型包含鳀、黄鲫、蓝点马鲛、其它中上层鱼类、小黄鱼、花鲈、其它底层鱼类、底栖鱼类、浮游动物、浮游植物、碎屑等17个功能群, 基本覆盖了渤海生态系统能量流动的途径.分析结果表明,1992年渤海生态系统的总生物量比1982年有所下降;小型中上层鱼类成为渔业资源的主要成分,其生物量较1982年明显增加;由于低营养级层次渔获物数量的增加,渔获物平均营养级有所下降.从系统规模看1982年大于1992年.1982年到1992年的十年间, 引起渤海生态系统结构变化的主要原因是初级生产力的变化以及捕捞因素.1982年与1992年渤海生态系统均处于不成熟的发育期,仍有较高的剩余生产量有待利用,因此渔业资源恢复的物质基础是有保证的.     

黄河口邻近海域生态系统能量流动与三疣梭子蟹增殖容量估算

增殖放流是渔业资源养护的重要手段, 生态系统与放流种类能流格局的变化研究,是进行增殖容量评估的研究基础.根据2012和2013年黄河口邻近海域的资源调查数据,构建了黄河口邻近海域6、8、10月的Ecopath模型,比较分析了3个月份该海域生态系统能量流动的变化,初步评估了三疣梭子蟹的增殖容量.结果表明： 黄河口邻近海域生态系统的能量流动主要在营养级I～III之间进行,营养级IV以及以上的能量流动较小.6月第I营养级整合系统流动的比例最高,8月最低.第II营养级整合系统流动的比例8月最高,6月最低.三疣梭子蟹相对能量流动和绝对能量流动均是第III营养级最高,三疣梭子蟹的营养级3月平均为3.28.黄河口邻近海域生态系统有较高的剩余生产量,6月最高、8月最低,系统的总初级生产量/总呼吸(TPP/TR) 3个月份分别为5.49、2.47、3.01,总初级生产量/总生物量(TPP/B)分别为47.61、33.30、29.78,同时具有较低的循环指数(FCI：0.03～0.06),黄河口邻近海域生态系统处于脆弱的不稳定期.系统的能量转换效率为7.3%～11.5%;渔获物的平均营养级8月和10月有所下降,3个月份分别为3.23、2.97和2.82;总捕捞效率8月最高,6月最低.在黄河口邻近海域8月Ecopath模型基础上,初步评估三疣梭子蟹的增殖容量为1.5115 t·km^-2.     

竺山湾湖泊缓冲带湿地生态系统EWE模型构建与分析

湖泊缓冲带在湖泊流域空间布局中具有特殊地位,缓冲带内的湿地对于保障流域生态健康和湖泊水环境质量具有十分重要的意义.本研究以太湖竺山湾湖泊缓冲带内的竺山湖湿地生态系统为研究对象,将生物组分划分为16个功能组,构建了生态通道(EWE)模型,并分析了生态系统的特征、状态以及功能组之间的相互关系.结果表明: 竺山湖湿地生态系统的有效营养级范围在1~3.72,营养流动主要发生在前4个营养级,开始于沉水植物和有机碎屑的食物链较多.湿地生态系统的总的能量转换效率为5.1%,并未达到“1/10定律”,说明当前的能量转换效率较低.物质流量在生态系统中的平均传输效率为4.3%.系统的总生产量为2496.66 t·km^-2·a^-1,总流量为10145.2 t·km^-2·a^-1.生态系统的多种特征参数表明当前生态系统处于幼态化阶段.     

An ecological model of the artificial ecosystem (northern Hangzhou Bay,China): analysis of ecosystem structure and fishing impacts

The artificial ecosystem is a large-scale enclosure in northern Hangzhou Bay, China. Using the Ecopath with Ecosim software, a trophic structure model is constructed for 2006–2007 to characterize the food web structure, functioning, and describing the ecosystem impacts of fishing. Input information for the model were gathered from published and unpublished reports and from our own estimates during the period 2006–2007. Pedigree work and simple sensitivity analysis were carried out to evaluate the quality and the uncertainty of the model. Results show that the food web in the enclosed sea area was dominated by a detritus pathway. The trophic levels of the groups varied from 1.00 for primary producers and detritus to 3.90 for piscivorous fish in the artificial system. Using network analysis, the system network was mapped into a linear food chain, and five discrete trophic levels were found with a mean transfer efficiency of 9.8% from detritus, 9.4% from primary producer within the ecosystem. The geometric mean of the trophic transfer efficiencies was 9.5%. Detritus contributed 57% of the total energy flux, and the other 43% came from primary producers. The ecosystem maturity indices-TPP/TR (total primary production/total respiration), FCI (Finn cycling index), A (ascendancy) and TB/TDET were 2.672, 25%, 31.5%, and 0.013, respectively, showing that the artificial system is at developmental stage according to Odum’s theory of ecosystem development. The ‘Keystoneness’ result indicates that herbivorous zooplankton was identified as keystone species in this system. Furthermore, a simple dynamical simulation was preformed for varying fishing mortality over 10 years. The biomass of most fish groups has a small increase when the fishing mortality at current level. Increasing fishing mortality by twofold resulted in a marked decrease in biomass of piscivorous fish accompanied by an increase in that of other fish groups, notable zooplanktivorous fish. Generally, this study represents the first attempt to evaluate the food web structure and the potential effects of fisheries in the artificial coastal ecosystem. It is concluded that this model is a potential tool for use in the management of the artificial ecosystem in northern Hangzhou Bay.     

Morphological drivers of trophic cascades

Worldwide, local anthropogenic extinctions have recently been reported to induce trophic cascades, defined as perturbations of top consumers that propagate along food chains down to primary producers. This focus on the effects of top‐consumer extinction (i.e. of species presence) ignores potential cascading effects of the rapid morphological changes that may precede extinction. Here, we show in an experimental, three‐level food chain including medaka fish, herbivorous zooplankton and unicellular algae that varying body length of a single fish from large (36.3 mm) to small (11.5 mm) induced a stronger trophic cascade than varying an average‐sized (23.8 mm) fish from being present to absent. The strength of fish predation on zooplankton scaled quasi linearly (not with a power exponent) with fish body length and associated gape width, suggesting that the resultant trophic cascade was morphology (not metabolism)‐dependent. The effect of fish body length was stronger on phyto‐ than on zooplankton, because large‐sized fish had the unique ability to suppress large‐sized herbivores, which in turn had high grazing capacities. Hence, our results show that consumer body size, by setting diet breadth, can both drive and magnify the strength of trophic cascades. In contrast, fish body shape had no significant effect on fish predatory performances when its allometric component (the effect of size on shape) was removed. In the wild, human‐induced body downsizing of top consumers is widespread, and mitigating the resultant perturbations to ecosystem function and services will require a paradigm shift from preserving species presence towards preserving species size structure.     

Environmental perturbation and the structure and functioning of a tropical aquatic ecosystem

In Tissawewa, a shallow, eutrophic reservoir in southeastern Sri Lanka, the effect of a major drought on the ecosystem was studied by monitoring the size-structured fish community and its resource base. Primary production was determined as well as the production and diets of ten taxa belonging to four trophic guilds (i.e. herbivorous/detritivorous, benthivorous, zooplanktivorous/insectivorous, piscivorous) that made up more than 98% of the total fish biomass. Two extreme states of the ecosystem were distinguished. Before the drought most primary production was generated byphytoplankton, suspended fine particulate detritus was an important food source and total fish density was high. After the drought the ecosystem was characterised by high macrophyte density, low concentration of suspended detritus and low total fish density. The availability and origin of detritus appeared to be the major factor influencing fish production in Tissawewa. The small pelagic herbivore/detritivore A. melettinus contributed the most biomass and production to the fish community before the drought. After the drought, however, biomass and production dropped considerably. In contrast, the production of the most important species in terms of fisheries yield, the exotic herbivorous/detritivorous tilapias, was hardly affected. Although the composition of their food, benthic detritus, had markedly changed. In Sri Lankan reservoirs a subsidiary fishery for pelagic minor cyprinids was suggested to increase the current yield which is based almost entirely on the exotic tilapia species. The perturbation observed in this study, however, showed that the production of pelagic species was affected particularly by the environmental changes. Exploitation of these species can, therefore, only be considered in combination with hydrological and other management measures that control the environmental conditions of the reservoirs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Trophic analysis and trophodynamic functioning of mangrove fish fauna of New Caledonia]

Fish communities from geomorphologically different mangrove forests showed distinct trophic structures. A mangrove area located near fringing reefs (Bouraké) was dominated by large invertebrate (> 2 mm) feeders (40.7% of total wet weight of the fish fauna) and herbivores (26.7%) whilst an estuarine mangrove (Ouenghi) was characterized by detritus feeders (28.2%), piscivorous (18.2%) and large invertebrate feeders (17.9%). In spite of these differences in trophic structure, similar food webs occurred in both areas, whereas the intensity of fluxes between trophic compartments was different. Resident species were usually at the base of the trophic structure. This component of the fish fauna used available sources of energy, such as microalgae in Bouraké or detritus and phytoplankton in Ouenghi. In contrast, transient species were high level predators, mainly piscivorous and large invertebrate feeders. These species actively contributed to net exports of energy from mangrove areas to nearby coastal habitats. Food webs and energy fluxes associated with trophic migration of fishes were particularly important in non-estuarine mangrove forests because of hydrologic conditions (salinity and turbidity) which were more suitable to the invasion of numerous marine foraging species (carangids, lutjanids, sphyraenids).     

Phytoplankton food quality control of planktonic food web processes

We developed a mechanistic model of nutrient, phytoplankton, zooplankton and fish interactions to test the effects of phytoplankton food quality for herbivorous zooplankton on planktonic food web processes. When phytoplankton food quality is high strong trophic cascades suppress phytoplankton biomass, the zooplankton can withstand intense zooplanktivory, and energy is efficiently transferred through the food web sustaining higher trophic level production. Low food quality results in trophic decoupling at the plant-animal interface, with phytoplankton biomass determined primarily by nutrient availability, zooplankton easily eliminated by fish predation, and poor energy transfer through the food web. At a given nutrient availability, food quality and zooplanktivory interact to determine zooplankton biomass which in turn determines algal biomass. High food quality resulted in intense zooplankton grazing which favored fast-growing phytoplankton taxa, whereas fish predation favored slow-growing phytoplankton. These results suggest algal food quality for herbivorous zooplankton can strongly influence the nature of aquatic food web dynamics, and can have profound effects on water quality and fisheries production. Handling editor: D. Hamilton     

Carbon sources and trophic structure in a macrophyte‐dominated polyculture pond assessed by stable‐isotope analysis

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Food resources sustaining the fish fauna in a section of the upper S?o Francisco River in Três Marias, MG, Brazil.

With the purpose of determining the principal food resources responsible for maintaining the fishery yield in a section of the S?o Francisco River, 6 sampling of the fish fauna were made downstream from the Três Marias Dam, from September 1996 to July 1997. A total of 1,127 individuals of 35 species were captured, using gillnets with mesh sizes varying from 3 to 16 cm. The stomach contents of 33 species were examined in order to determine their diets. Five trophic guilds were established, in the following order of importance: ilyophagous, herbivorous, piscivorous, terrestrial invertebrates feeders, and aquatic invertebrates feeders. The resources sustaining the fish fauna were mainly of allochthonous origin. The ichthyonenosis appears to be mainly dependent on the detritus chain. The ciliary forest and seasonal flooding pulses are the main suppliers of food for the fish fauna.     

Fish diversity as a determinant of ecosystem properties across multiple trophic levels

Biodiversity has been established as a potential determinant of function in many ecosystems; however, previous research has mostly focused on primary producers and effects at a single trophic level. A broader perspective that considers multiple components of food webs is necessary to understand natural systems. In particular, consumer diversity needs to be more thoroughly examined as trophic interactions and indirect effects can alter ecosystem properties. We test the potential for consumer diversity (fish richness and composition) to govern food web dynamics at two levels of environmental complexity (mesocosms and experimental ponds) and explore the consequences of removing individual species of fish on lower trophic levels. In mesocosms, both the richness and density of zooplankton were reduced when more fish species were present. No effects from the fish treatments were found on phytoplankton, but phosphorus levels increased with higher fish richness. Removing either generalist or specialist fish species increased the richness and density of zooplankton and the amount of phytoplankton, whereas all fish species had redundant effects on nutrients. In ponds, a dominant fish species (specialist shiner) determined the richness and density of zooplankton. In contrast, phytoplankton and nutrients were reduced by higher fish richness in the fall and spring. Overall, the specialist shiner had unique effects on the pond food web suggesting the key to understanding function is the presence of a dominant species and their biological interactions. Differences between mesocosms and ponds are likely due to increased heterogeneity of resources in the ponds allowing species to specialize on different prey. Our study links the biodiversity ecosystem function paradigm with food web concepts to improve predictions for conservation and management actions in response to changes in biodiversity.     

Effect of modern changes in the pelagial of the Black Sea on the state of fishery

Environmental changes and trophic relations in the ecosystem of the Black Sea are analyzed. We show that, during the last 30 years, the trophic structure of the ecosystem underwent considerable changes that led to a decrease in the efficiency of transfer of energy along food chains and a decrease in the productivity of populations of consumers. Unfavorable changes occurred in the structure of communities of zooplankton: the role of ??food?? species decreased, and the role of ??nonfood?? invading species increased. All this caused a decrease in the efficiency of transfer of energy from primary producers to fish and a decrease in the production of the latter.