杭州湾北岸大型围隔海域人工生态系统的能量流动和网络分析

根据2006年在杭州湾北岸大型围隔海域进行的生态调查数据,利用EwE软件构建围隔海域人工生态系统的能量流动模型.模型由13个功能组构成,分别是肉食性鱼类、底栖捕食鱼类、浮游动物性鱼类、草食性鱼类、蟹类、虾类、软体动物、底栖动物、肉食性浮游动物、植食性浮游动物、大型藻类、浮游植物和有机碎屑,每一组都代表在生态系统中具有相似地位的有机体,基本覆盖了该人工生态系统能量流动的主要过程.能量流动分析表明,围隔海域人工生态系统中能量流动主要以碎屑食物链途径为主,其中植食性浮游动物在能量从低级向高层次转换中起关键作用.人工生态系统的营养级范围为1.00～3.90级,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9.4%,来自碎屑的转换效率为9.8%,平均能量转换效率为9.6%.经生态网络分析,直接来源于碎屑的比例占总流量的57%,而直接来源于初级生产者的比例为43%,生态系统特征参数:总初级生产计算量/总呼吸量(TPP/TR)、系统物质和能量循环率(FCI)和系统聚合度(A)值分别为2.672、0.25、0.315,表明围隔海域人工生态系统目前正处于发育时期.该研究为首次利用Ecopath模型分析大型围隔海域人工生态系统的结构和能量流动,旨在为富营养化近岸海域的生态修复提供理论依据.     

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%。     

Using an Ecosystem Modeling Approach to Explore Possible Ecosystem Impacts of Fishing in the Beibu Gulf,Northern South China Sea

Using the Ecopath with Ecosim software, a trophic structure model of the Beibu Gulf was constructed to explore the energy flows and provide a snapshot of the ecosystem operations. Input data were mainly from the trawl survey data collected from October 1998 to September 1999 and related literatures. The impacts of various fishing pressure on the biomass were examined by simulation at different fishing mortality rates. The model consists of 20 functional groups (boxes), each representing organisms with a similar role in the food web, and only covers the major trophic flows in the Beibu Gulf ecosystem. It was found that the food web of the Beibu Gulf was dominated by the primary producers path, and phytoplankton was the primary producer mostly used as a food source. The fractional trophic levels ranged from 1.0 to 4.02, and the marine mammals occupied the highest trophic level. Using network analysis, the ecosystem network was mapped into a linear food chain, and six discrete trophic levels were found with a mean transfer efficiency of 11.2%. The Finn cycling index was 9.73%. The path length was 1.821. The omnivory index was 0.197. The ecosystem had some degree of instability due to exploitation and other human activities, according to Odum’s theory of ecosystem development. A 10-year simulation was performed for each fishery scenario. The fishing mortality rate was found to have a strong impact on the biomass. By keeping the fishing mortality rate at the current level for all fishing sectors, scenario 1 had a drastic decrease in the large fish groups. The biomass of the small and medium pelagic fish would increase to some extent. The biomass of the small and low trophic level species, jellyfish, prawns and benthic crustaceans would be stable. The total biomass of the fishery resources would have a 10% decrease from the current biomass after 10 years. In contrast, the reduced fishing mortality rate induced the recovery of biomass (scenarios 2–4). In scenario 2, the biomass of the large demersal fish and the large pelagic fish would increase to over 16 times and 10 times, respectively, of their current level. In scenario 4, the biomass of the large pelagic fish would increase to over 3 times of its current level. The total biomass of the fish groups, especially the high trophic level groups, would become significantly higher after 10 years, which illustrates the contribution on biomass recovery by relaxing the fishing pressure. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Author contributions: Xiaoping Jia designed research; Zuozhi Chen and Yongsong Qiu performed research; Zuozhi Chen, Yongsong Qiu, and Shannan Xu analyzed data; and Zuozhi Chen and Shannan Xu wrote the article.     

Evaluating ecosystem structure and functioning of the East China Sea Shelf ecosystem,China

As China’s second-largest large marine ecosystem, the East China Sea Shelf has suffered from overfishing, eutrophication, and physical disturbance over the last several decades. A trophic mass-balance model of this ecosystem was developed in order to characterize the structure and functioning of its food web, to identify its keystone species, and to quantify the ecological impacts of fishing that it sustained during the early 2000s. Using a multivariate statistical analysis, we identified 38 functional groups for the trophic model, including fish and invertebrate groups targeted and not targeted by fisheries. Pelagic sharks and rays were identified as the keystone species in the ecosystem. Strong benthic–pelagic coupling was indicated in this ecosystem. In particular, this study highlighted the interdependent relationships that exist among plankton, benthic invertebrates, and detritus. Recent fishing activities were characterized by high exploitation rates for various commercially targeted and non-targeted species, leading to the removal of much of the ecosystem’s fishable production. Overall, our findings give a preliminary explanation of the current problems of eutrophication and fishery depletion and other changes in the East China Sea Shelf, and highlight the need for developing ecosystem-based fisheries management.     

Food web structure and ecosystem properties of the largest impounded lake along the eastern route of China's South-to-North Water Diversion Project

Hongze Lake (HZL) is the largest impounded lake along the eastern route of China's South-to-North Water Diversion Project. However, there is surprisingly little ecological understanding on this important ecosystem, especially under the potential water diversion threats. Here, a mass-balance model was constructed to characterize trophic structure and ecosystem properties of HZL. The model outputs indicated that small sized fishes have dominated the food web, and fishery resources were suffered from high pressures of overfishing. Mandarin fish, Northern snakehead, Other piscivores and Large culters occupied the top trophic niche, while macrophytes, phytoplankton and detritus consisted of the main energy sources. HZL food web was fairly based on two main food chains: primary production (49.9%) and detritus pool (50.1%), but transfer efficiencies in both chains were relatively low as 6.37% and 6.49%, respectively. Predator-prey interactions, trophic cascading effects and competition of different components were also exhibited in the mixed trophic impacts map. Results from the network analysis suggested that the HZL ecosystem was a relatively mature ecosystem since the total primary production to respiration (TPP/TR) and to biomass (TPP/TB) were 1.138 and 6.922, and the Finn Cycling Index was 6.77%. Nevertheless, the relatively low values of Connectance Index (0.195) and System Omnivory Index (0.089), together with Finn's Mean path Length (2.849) also indicated that the food web structure was vulnerable, characterized by linear, rather than web-like features. Our results suggested that the HZL ecosystem would be potentially affected by the future inter-basin water diversion, and thus ecosystem-based strategies were also presented accordingly.     

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.     

捕捞对北部湾海洋生态系统的影响

利用Ecopath with Ecosim (EwE) 5.1软件构建了北部湾海洋生态系统1959—1960年的Ecosim模型,包含渔业、海洋哺乳动物、海鸟、中上层鱼类、底层鱼类、底栖无脊椎动物等20个功能组,通过与1997—1999年调查数据对比,分析了捕捞活动对北部湾生态系统的结构和功能的影响.结果表明：近40年来在捕捞强度不断增加的压力下,生态系统的结构和功能发生显著变化,长寿命、高营养级的肉食性鱼类生物量下降明显,系统以短寿命、小型鱼类和无脊椎动物占优势.1999年的大中型鱼类的生物量仅为1960年的6%,而小型鱼类和无脊椎动物则明显上升,尤其是头足类生物量上升了2.7倍,渔获物的营养级则从1960年的3.2降低到1999年的298,体现了“捕捞降低海洋食物网”的特点,目前的开发模式是不可持续的.利用20世纪90年代数据预测了降低捕捞压力后生态系统的变化.本研究证实了可以使用Ecosim模型预测捕捞压力对生态系统的影响.     

基于Ecopath模型的太湖生态系统结构与功能分析

根据2008—2009年太湖湖区水生生物调查的结果及主要水生动物摄食生态学已发表资料,应用Ecopath with Ecosim 6.1软件构建了太湖生态系统的食物网模型,初步分析了太湖生态系统功能与结构特征.模型由初级生产者、主要鱼类及无脊椎动物和有机碎屑等20个功能组组成.结果表明： 太湖生态系统的能流主要分布在4个营养级上,顶级捕食者鲌鱼营养级最高.食物网存在两条主要的营养传递途径,即碎屑食物链和牧食食物链,且碎屑食物链占比较大;营养级I的利用效率低下,大量初级生产力未能流入更高的营养层次,造成生态系统下层的营养流动“阻塞”.对系统总体特征分析发现,反映系统成熟度的指标,包括较高的净初级生产力(NPP)和净初级生产力/呼吸(NPP/R),以及较低的连接指数(CI)、系统杂食指数(SOI)和Finn循环指数(FCI)等,都揭示了太湖“幼态化”的生态系统现状;混合营养分析和关键种筛选结果显示,高强度的渔业捕捞活动对系统负影响显著,而顶级捕食者的下行效应显著下降.
     

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.     

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.     

A food web analysis of the Río de la Plata estuary and adjacent shelf ecosystem: trophic structure,biomass flows,and the role of fisheries

This article performed a comprehensive assessment of the structure and functioning of the Río de la Plata estuary and adjacent shelf ecosystem, including the effect of fishing. A formerly implemented 37 trophic groups’ mass-balance model (Ecopath) was used to (1) evaluate the particular role of individual biotic components on the ecosystem; (2) characterize the ecosystem in terms of aquatic food web theory; and (3) assess the role of diverse fishing fleets on the ecosystem. Our results indicate a trophic structure and functioning common to other estuaries, where outstanding primary production exceeds consumption, and detritus accumulates in the system. Moreover, our analysis revealed an elevated total system throughput, herbivory outweighing detritivory, and an intermediate state in terms of ecosystem growth and development. Fisheries analyses showed widespread impacts produced by industrial bottom trawl fleets, and specific impacts produced by artisanal fisheries over several groups. Unexpectedly, the evaluation of the effects of fishing showed minor ecosystem consequences by the loss of secondary production and suggests exploitation rates at sustainable levels. This study sets up the basis for temporal ecosystem-level monitoring of the state of the Río de la Plata estuary and adjacent shelf ecosystem.     

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。     

Trophic functioning of the Tiahura reef sector, Moorea Island, French Polynesia

 Energy-balanced steady-state models of the fringing and barrier reefs of Tiahura, Moorea Island, French Polynesia, are presented. A total of 43 and 46 trophic groups were identified on the two reef habitats respectively. The models’ outputs indicate that most of the substantial primary productivity is processed and recycled (59–69% of NPP) in the web through detritus based, microbially mediated food webs, with a substantial but secondary flux through grazer-based webs. This mechanism produces long pathways with low trophic efficiencies at the higher trophic levels. The trophic structure of both reef habitats efficiently conserves energy and materials within the reef ecosystem through two forms of internal recycling: a relatively large cycle produced through detritus and a microbial food web, and a relatively short one directly produced through predation. The models outputs suggest that bottom-up and top-down control are each ecologically important in both reef habitats. Accepted: 14 April 1997     

Functioning of the Sea of Azov ecosystem

The structure and functioning of the Sea of Azov ecosystem have been studied. Based on the results of an analysis of the principal community components (phytoplankton, bacterioplankton, zooplankton, macrozoobenthos, and fish), the elements of balance equality and food utilization by the ecosystem components were calculated and schemes of their energy flow were constructed. The intensity and trends of production-destruction processes were characterized. It was revealed that the main energy flow in the Sea of Azov ecosystem passes through the detritus food web (81%). Along with eutrophication and sulfide pollution of bottom sediments, the impact of predatory ctenophore Mnemiopsis leidyi (A. Agassiz) determines to a considerable extent the pattern of the ecosystem’s transformation.     

Energy flow and network analysis of Terminos Lagoon, SW Gulf of Mexico

The food web in Terminos Lagoon, south-western Gulf of Mexico was dominated by the detrital pathway, with benthic invertebrates playing a significant role in transferring energy from detritus to higher trophic levels. The fish yield per unit of net primary production was only 0.04%. Fractional trophic levels ranged from 1.0 to 3.31, with fish occupying the highest trophic levels. Using network analysis, the system network was mapped into a linear food chain and five discrete trophic levels were found with a mean trophic transfer efficiency of 7%. Analysis of mixed trophic impacts showed that fish had very little impact on the other compartments, due to their relatively low biomass and consumption, with exception of the Engraulidae. Detritus and lower trophic levels had significant positive impacts on other groups in the system, suggesting 'bottom-up' control of the food web. A high detritivory: herbivory ratio (4.6: 1) indicated that most of the primary production was recycled through the detritus-based food web. A Finn cycling index of 7% and average path length of 10 were obtained.     

Food web complexity and higher-level ecosystem services

Studies mostly focused on communities of primary producers have shown that species richness provides and promotes fundamental ecosystem services. However, we know very little about the factors influencing ecosystem services provided by higher trophic levels in natural food webs. Here we present evidence that differences in food web structure and the richness of herbivores in 19 plant‐herbivore‐parasitoid food webs influence the service supplied by natural enemies, namely, the parasitism rates on hosts. Specifically, we find that parasitoids function better in simple food webs than in complex ones, a result relevant to biological control practice. More generally, we show that species richness per se only contributes partially to the understanding of higher‐level ecosystem services in multitrophic communities, and that changes in food web complexity should also be taken into account when predicting the effects of human‐driven disturbances in natural communities.     

Ecological effects of longline fishing and climate change on the pelagic ecosystem off eastern Australia

Pelagic longline fisheries target (or catch incidently) large apex predators in the open ocean (e.g. tunas, billfish and sharks) and have the potential to disrupt the ecosystem functionality if these predators exert strong top–down control. In contrast, warming of oceans from climate change may increase bottom–up effects from increases in primary productivity. An ecosystem model of a large pelagic ecosystem off eastern Australia was constructed to explore the potential ecological effects of climate change and longlining by Australia’s Eastern Tuna and Billfish Fishery. The model reproduced historic biomass and fishery catch trends from 1952 to 2006 for seven functional groups. Simulated changes in fishing effort and fishing mortality rate on individual target species from 2008 to 2018 resulted in only modest (<20%) changes in the biomass of target species and their direct predators or competitors. A simulated increase in phytoplankton biomass due to climate change resulted in only small increases (<11%) in the biomass of all groups. However, climate-related changes to the biomass of micronekton fish (−20%) and cephalopods (+50%) resulted in trophic cascades. Our results suggest there may be ecological redundancy among high trophic level predators since they share a diverse suite of prey and collectively only represent <1% of the total system biomass. In contrast, micronekton fishes and cephalopods have high biomasses and high production and consumption rates and are important as both prey and predators. They appear to exert ‘wasp–waist’ control of the ecosystem rather than top–down or bottom–up processes reported to drive other pelagic systems.     

Trophic interactions and community structure in the upwelling system off Central Chile (33-39°S)

Trophic interactions and community structure in the upwelling system off Central Chile (USCCh) (33-39°S) are analyzed using biological and ecological data concerning the main trophic groups and the Ecopath with Ecosim software version 5.0 (EwE). The model encompasses the fisheries, cetaceans, sea lion, marine birds, cephalopods, large-sized pelagic fish (sword fish), medium-sized pelagic fish (horse mackerel, hoki), small-sized pelagic fish (anchovy, common sardine), demersal fish (e.g. Chilean hake, black conger-eel), benthic invertebrates (red squat lobster, yellow squat lobster) and other groups such as zooplankton, phytoplankton and detritus. Input data was gathered from published and unpublished reports and our own estimates. Trophic interactions, system indicators and food web attributes are calculated using network analysis routines included in EwE. Results indicate that trophic groups are aligned around four trophic levels (TL) with phytoplankton and detritus at the TL=1, while large-sized pelagic fish and cetaceans are top predators (TL>4.0). The fishery is located at an intermediate to low trophic level (TL=2.97), removing about 15% of the calculated system primary production. The pelagic realm dominates the system, with medium-sized pelagic fish as the main fish component in biomass, while small-sized pelagic fish dominate total landings. Chilean hake is by far the main demersal fish component in both, biomass and yield. Predators consume the greater part of the production of the most important fishery resources, particularly juvenile stages of Chilean hake. Consequently, mortality by predation is an important component of total mortality. However, fishery also removes a large fraction of common sardine, anchovy, horse mackerel, and Chilean hake. The analysis of direct and indirect trophic impacts reveals that Chilean hake is a highly cannibalistic species. Chilean hake is also an important predator on anchovy, common sardine, benthic invertebrates, and demersal fish. The fisheries heavily impact on Chilean hake, common sardine, anchovy, and horse mackerel. Total system biomass (B=476 t km⁻² year⁻¹) and throughput (T=89454 t km⁻² year⁻¹) estimated in the USCCh model are in accordance with models of comparable systems. Considering system attributes derived from network analysis, the USCCh can be characterized as an immature system, with short trophic chains and low trophic transfer efficiency. Finally, we suggest that trophic interactions should be considered in stock assessment and management programs in USCCh. In addition, future research programs should be carried out in order to understand the ecosystem effects of fishing and trophic control in this highly productive food web.     

Coupling of green and brown food webs and ecosystem stability

Ecosystems comprise living organisms and organic matter or detritus. In earlier community ecology theories, ecosystem dynamics were normally understood in terms of aboveground, green‐world trophic interaction networks, or food webs. Recently, there has been growing interest in the role played in ecosystem dynamics by detritus in underground, brown‐world interactions. However, the role of decomposers in the consumption of detritus to produce nutrients in ecosystem dynamics remains unclear. Here, an ecosystem model of trophic food chains, detritus, decomposers, and decomposer predators demonstrated that decomposers play a totally different role than that previously predicted, with regard to their relationship between nutrient cycling and ecosystem stability. The high flux of nutrients due to efficient decomposition by decomposers increases ecosystem stability. However, moderate levels of ecosystem openness (with movement of materials) can either greatly increase or decrease ecosystem stability. Furthermore, the stability of an ecosystem peaks at intermediate openness because open systems are less stable than closed systems. These findings suggest that decomposers and the food‐web dynamics of brown‐world interactions are crucial for ecosystem stability, and that the properties of decomposition rate and openness are important in predicting changes in ecosystem stability in response to changes in decomposition efficiency driven by climate change.