Aggregation of species with similar ecological properties is one of the effective methods to simplify food web researches.However,species aggregation will affect not only the complexity of modeling process but also th...Aggregation of species with similar ecological properties is one of the effective methods to simplify food web researches.However,species aggregation will affect not only the complexity of modeling process but also the accuracy of models’outputs.Selection of aggregation methods and the number of trophospecies are the keys to study the simplification of food web.In this study,three aggregation methods,including taxonomic aggregation(TA),structural equivalence aggregation(SEA),and self-organizing maps(SOM),were analyzed and compared with the linear inverse model–Markov Chain Monte Carlo(LIM-MCMC)model.Impacts of aggregation methods and trophospecies number on food webs were evaluated based on the robustness and unitless of ecological net-work indices.Results showed that aggregation method of SEA performed better than the other two methods in estimating food web structure and function indices.The effects of aggregation methods were driven by the differences in species aggregation principles,which will alter food web structure and function through the redistribution of energy flow.According to the results of mean absolute percentage error(MAPE)which can be applied to evaluate the accuracy of the model,we found that MAPE in food web indices will increase with the reducing trophospecies number,and MAPE in food web function indices were smaller and more stable than those in food web structure indices.Therefore,trade-off between simplifying food webs and reflecting the status of ecosystem should be con-sidered in food web studies.These findings highlight the importance of aggregation methods and trophospecies number in the analy-sis of food web simplification.This study provided a framework to explore the extent to which food web models are affected by dif-ferent species aggregation,and will provide scientific basis for the construction of food webs.展开更多
Climate change has led to significant fluctuations in marine ecosystems,including alterations in the structure and function of food webs and ecosystem status.Coastal ecosystems are critical to the functioning of the e...Climate change has led to significant fluctuations in marine ecosystems,including alterations in the structure and function of food webs and ecosystem status.Coastal ecosystems are critical to the functioning of the earth’s lifesupporting systems.However,temporal variations in most of these ecosystems have remained unclear so far.In this study,we employed a linear inverse model with Markov Chain Monte Carlo(LIM-MCMC)combined with ecological network analysis to reveal the temporal variations of the food web in Haizhou Bay of China.Food webs were constructed based on diet composition data in this ecosystem during the year of 2011 and 2018.Results indicated that there were obvious temporal variations in the composition of food webs in autumn of 2011 and 2018.The number of prey and predators for most species in food web decreased in 2018 compared with 2011,especially for Trichiurus lepturus,zooplankton,Amblychaeturichthys hexanema,and Loligo sp.Ecological network analysis showed that the complexity of food web structure could be reflected by comprehensive analysis of compartmentalized indicators.Haizhou Bay ecosystem was more mature and stable in 2011,while the ecosystem’s self-sustainability and recovery from disturbances were accelerated from 2011 to 2018.These findings contribute to our understanding of the dynamics of marine ecosystems and highlight the importance of comprehensive analysis of marine food webs.This work provides a framework for assessing and comparing temporal variations in marine ecosystems,which provides essential information and scientific guidance for the Ecosystem-based Fisheries Management.展开更多
The tropical Pacific Ocean supports many productive commercial fisheries.However,few studies of ecosystem structure in the tropical Pacific Ocean have been carried out.In this study,we analyzed the food web structure ...The tropical Pacific Ocean supports many productive commercial fisheries.However,few studies of ecosystem structure in the tropical Pacific Ocean have been carried out.In this study,we analyzed the food web structure in the central and eastern tropical Pacific Ocean based on trophic relationships of 35 pelagic species collected by Chinese tuna longline observers from June to November in 2017.Topology indices(node degree,D;centrality indices,BC and CC;topological importance indices,TI^1,TI^3;keystone indices,K,K_t and K_b)and Key-Player algorithms(KPP-1,KPP-2)were used to select key species and construct a simplified food web combined with body size data.The Kendall rank correlation and hierarchical clustering analysis indicated that different topology indices resulted in consistent rankings of key species.Most key species were the same as those selected in other studies in the Pacific Ocean,such as Shortbill spearfish(Tetrapturus angustirostris),Swordfish(Xiphias gladius),Albacore tuna(Thunnus alalunga),cephalopods and scomber.The food web would be separated into many unconnected parts(F=0.632,FD=0.795,R^D=0.957)after the removal of the five key species,indicating the key roles of these species in the food web structure and stability.Body size was considered an influential indicator in constructing the simplified food web.This study can improve our understanding of the food web structure in the tropical Pacific Ocean and provide scientific basis for further ecosystem dynamics studies.展开更多
Food web structures are well known to vary widely among ecosystems. Moreover, many food web studies of lakes have generally attempted to characterize the overall food web structure and have largely ignored internal sp...Food web structures are well known to vary widely among ecosystems. Moreover, many food web studies of lakes have generally attempted to characterize the overall food web structure and have largely ignored internal spatial and environmental variations. In this study, we hypothesize that there is a high degree of spatial heterogeneity within an ecosystem and such heterogeneity may lead to strong variations in environmental conditions and resource availability, in turn resulting in dif ferent trophic pathways. Stable carbon and nitrogen isotopes were employed for the whole food web to describe the structure of the food web in different sub-basins within Taihu Lake. This lake is a large eutrophic freshwater lake that has been intensively managed and highly influenced by human activities for more than 50 years. The results show significant isotopic dif ferences between basins with dif ferent environmental characteristics. Such differences likely result from isotopic baseline dif ferences combining with a shift in food web structure. Both are related to local spatial heterogeneity in nutrient loading in waters. Such variation should be explicitly considered in future food web studies and ecosystem-based management in this lake ecosystem.展开更多
The food sources of aquacultured Apostichopus japonicus and the trophic levels of organisms in a sea cucumber（A. japonicus） and prawn（Penaeus japonica） polyculture system in a saltwater pond in Zhuanghe, Liaoning ...The food sources of aquacultured Apostichopus japonicus and the trophic levels of organisms in a sea cucumber（A. japonicus） and prawn（Penaeus japonica） polyculture system in a saltwater pond in Zhuanghe, Liaoning Province were examined using carbon and nitrogen stable isotopes. Across organisms, δ13C ranged from（–25.47±0.20）‰ to（–16.48±0.17）‰（mean±SD）, and δ15N ranged from（4.23±0.49）‰ to（12.44±0.09）‰. The δ13C and δ15N contents of A. japonicus, P. japonica and Fenneropenaeus chinensis were comparatively higher than those of other organisms. Values of δ13C and δ15N revealed that P. japonica, Hemigrapsus sanguineus and Neomysis japonica comprised the largest component of the diet of A. japonicus. The mean trophic level of the organisms in this saltwater pond polyculture system was（2.75±0.08）. P. japonica, A. japonicus, F. chinensis,Synechogobius hasta and Neomysis japonica were in the 3rd trophic level（2–3）; jellyfish, H. sanguineus and zooplankton were in the 2nd trophic level（1–2）; and Enteromorpha prolifera, benthic microalgae, periphyton and suspended matter primarily consisting of phytoplankton, bacteria and humus were in the primary trophic level（0–1）.展开更多
By anayses of carbon isotopic composition (δ13C values) of the benthos collected in the Laoshan Bay in August 1993 and February and May 1994, it is found that the main food sources of the benthos can be divided into ...By anayses of carbon isotopic composition (δ13C values) of the benthos collected in the Laoshan Bay in August 1993 and February and May 1994, it is found that the main food sources of the benthos can be divided into four groups in terms of carbon isotope composition: Particulate Organic Matter (POM), benthic diatoms, benthic macroalgae and the organic matter in sediments. The results show that the carbon isotopic composition of the benthic animals has a close relation with that of the food they take in. The Carbon isotopic compositions of benthos may be useful in elucidating their food sources. The carbon isotopic data have confirmed that POM is the main food source of the benthic filter feeders such as bivalves; crustaceans have a wide range of δ13C values, showing their food source has diversity; benthic diatoms are an important fraction of the food for most of gastropods. A preliminary investigation of the benthic-pelagic coupling in that region using the stable carban isotopic tracers has confirmed the importance of POM as a food source for benthos in this region, but the organic matter in sediments and benthic diatoms are also relatively important for a lot of benthic animals. The benthic-pelagic coupling in the Laoshan Bay temperate ecosystem is not so tight as that in ecosystems at higher latitudes such as northeastern water polynya.展开更多
The worldwide increase in commercial fisheries and its impact on ecosystems as well as inefficient fishery management have led to overfishing and frequent breakdown of traditional fish stocks. In this context, an anal...The worldwide increase in commercial fisheries and its impact on ecosystems as well as inefficient fishery management have led to overfishing and frequent breakdown of traditional fish stocks. In this context, an analysis of Khuzestan inshore fisheries data covering the years 2002-2011, was conducted in reliance on testing for occurrence of the fishing down marine food webs （FDMFW） phenomenon in the North of Persian Gulf Large Marine Ecosystem （LME）. In this study, the mean trophic level （mTL） and the fishing-in-balance （FIB）-index of Khuzestan landings during this period of time were estimated using the trophic level of 47 fishery resources. Increase in total landings （I1） was observed, which explained the high fishing yield in major fishery resources （especially demersal）. Moreover, the moderates decreasing trend in mTL per decade, and the increasing trend in FIB-index were observed. The status of fishery resources in Khuzestan inshore waters （under exploited but not overexploited）, the rise in Y, FIB and slightly drop in mTL can be considered as indirect indicators of the fishing impacts on the trophic structure of marine communities. Based on this result, probability occurrence of FDMFW process in Khuzestan inshore waters is low to some extent. However, we suggest that the goal of management programs in Khuzestan inshore waters should prevent the continuance of this trend in the long-term using an ecosystem-based approach.展开更多
Stable isotope values, δ13C and δ15N, were determined for four primary producers and 19 dominant consumers in a small artificial lagoon located in Hangzhou Bay. Based on these results the major pathways for energy f...Stable isotope values, δ13C and δ15N, were determined for four primary producers and 19 dominant consumers in a small artificial lagoon located in Hangzhou Bay. Based on these results the major pathways for energy flow and trophic structure of the artificial lagoon ecosystem were characterized. The mean δ13C values for the 19 consumers ranged from -22.99‰ to -14.24‰. Apart from so-iny mullet Liza haematocheila, the other 18 consumers had intermediate δ13C values between those of epibenthic microalgae and particulate organic matter (POM). The results of a multiple source linear mixing model (IsoSource model) indicated that 50% or more of the organic carbon in the tissues of most consumers was derived from epibenthic microalgae. This indicated that these primary producers were the main food source fueling the lagoon food web. The mean δ15N values for the 19 consumers varied between 4.93‰ and 12.97‰ and indicated four trophic levels in the lagoon. Four macroinvertebrates and zooplankton represented the primary consumers, whilst the other 14 consumers occupied the secondary and tertiary consumer levels. The 19 consumers were divided into three trophic guilds (detritivores/suspension feeders, omnivores and carnivores).展开更多
Single-species management ignores the interactions between species,and ecosystem-based fisheries management(EBFM)has become a main method to fisheries management.Understanding food web structures and species interacti...Single-species management ignores the interactions between species,and ecosystem-based fisheries management(EBFM)has become a main method to fisheries management.Understanding food web structures and species interactions is essential for the implementation of EBFM and maintenance of ecosystem functions.Overfishing is one of the main reasons behind the depletion,which could even lead to the depletion of some target species in local areas.So understanding the impacts of species depletion on food web structures is important for the implementation of EBFM.The impacts of species depletion can be transmitted through the food web and cause the local extinction of both target and non-target species.In this study,topological network analysis was applied to examine the impacts of species depletion on the food web structure of Haizhou Bay.Results showed that fine crayfish Leptochela gracilis,squid Loligo sp.,and Japanese snapping shrimp Alpheus japonicus have the highest numbers of outgoing links(48,32 and 31 respectively);thus,these species may be considered key prey species.Whitespotted conger Conger myriaster,fat greenling Hexagrammos otakii,and bluefin gurnard Chelidonichthys kumu were key predators with the highest number of incoming links(37,36 and 35 respectively).The competition graphs derived from the Haizhou Bay food web were highly connected(more than 40%predators sharing over 10 common prey species),and showed close trophic interaction between high trophic level fishes.Simulation analysis showed that the food web structure has small changes to the depletion of species in a highly complex food web.The most-connected target species did not necessarily indicate high structural importance;however,some species with low connectivity may demonstrate stronger trophic interactions and play important ecological roles in the food web.But most species were more sensitive to the depletion of the most-connected target species than other target species(for instance,for zooplankton,closeness centrality 13.876 in D6,but closeness centrality 82.143 in original food web).Therefore,EBFM should focus on the most-connected target species,but also on those species with few but strong links and feeding relationships in the food web.展开更多
Mean trophic level of fishery landings（MTL） is one of the most widely used biodiversity indicators to assess the impacts of fishing. Based on the landing data compiled by Food and Agriculture Organization combined w...Mean trophic level of fishery landings（MTL） is one of the most widely used biodiversity indicators to assess the impacts of fishing. Based on the landing data compiled by Food and Agriculture Organization combined with trophic information of relevant species in Fish Base, we evaluated the status of marine fisheries from 1950 to 2010 for different coastal states in Pacific, Atlantic and Indian Oceans. We found that the phenomenon of ＂fishing down marine food webs＂ occurred in 43 states. Specifically, 27 states belonged to ＂fishing-through＂ pattern, and 16 states resulted from ＂fishing-down＂ scenario. The sign of recovery in MTL was common in the Pacific, Atlantic and Indian Oceans（occurred in 20 states）, but was generally accompanied by significantly decreased catches of traditional low trophic level species. In particular, 11 states showed significant declining catches of lower trophic levels. The MTL-based assessment of ＂fishing down marine food webs＂ needs to be interpreted cautiously.展开更多
To investigate the food web structure of Liusha Bay,the δ13C and δ15N values of various organisms collected in Liusha Bay were measured via stable isotope technique.Based on the calculated δ15N value,the correlatio...To investigate the food web structure of Liusha Bay,the δ13C and δ15N values of various organisms collected in Liusha Bay were measured via stable isotope technique.Based on the calculated δ15N value,the correlation between stable isotope ratio and trophic level were established to predict the trophic levels of shrimps,crabs,cephalopods and fishes.By comparing the analysis results of stomach contents of 24 organisms,two methods gave a similar consistence in approximately 71% of organisms within a 0.5 trophic level.It is concluded that stable isotope technique could be an effective method for studying ocean food web trophic level.展开更多
An artificial aquatic food web (AAFW) system was designed to remove the non-point source pollutants in eutrophic Jiyu river. A certain amount of Scenedesmus obliquus and Daphnia pulex was cultured in the system for th...An artificial aquatic food web (AAFW) system was designed to remove the non-point source pollutants in eutrophic Jiyu river. A certain amount of Scenedesmus obliquus and Daphnia pulex was cultured in the system for the control of serious cyanobacterial bloom. The AAFW system was a continuous-flow system including one storage basin of 3 m<sup>3</sup> capacity with polluted river water (the total nitrogen-TN: 4.49 mg⋅l<sup>-1</sup><sup></sup>;the total phosphorus-TP: 0.192 mg⋅l-1</sup></sup><sup></sup>), one phytoplankton tank of 3 m<sup>3</sup> capacity with an initial concentrations of S. obliquus about 5.8 × 10<sup>3</sup> ind⋅l-1</sup><sup></sup>, and one zooplankton growth chamber of 1.5 m<sup>3</sup> capacity with an initial abundance of D. pulex about 22.5 ind⋅l-1</sup></sup>. The system was optimized by setting hydraulic retention time of phytoplankton tank as 5 days and the experiments were operated for 45 days. Compared with the polluted river, TN and TP were removed about 28% and 47% by the AAFW system, respectively. The biomass of phytoplankton decrease from 6.33 mg⋅l-1<sup></sup> to 1.48 mg⋅l-1</sup><sup></sup> and the percentage of cyanobacteria decrease from 43.93% to 2.36%, the biomass of Crustacean zooplankton increase from 0.34 mg⋅l-1</sup></sup><sup></sup> to 1.53 mg⋅l-1</sup></sup><sup></sup> and the percentage of D. pulex increase from 19.19% to 57.62%. Our results indicated that the AAFW system not only is an efficient, flexible system for reducing nutrient levels in tributary rivers, but also has an ability to control the cyanobacteria bloom and rebuilding the aquatic ecosystem from the polluted river water.展开更多
Exploring how food web complexity emerges and evolves in island ecosystems remains a major challenge in ecology.Food webs assembled from multiple islands are commonly recognized as highly complex trophic networks that...Exploring how food web complexity emerges and evolves in island ecosystems remains a major challenge in ecology.Food webs assembled from multiple islands are commonly recognized as highly complex trophic networks that are dynamic in both space and time.In the context of global climate change,it remains unclear whether food web complexity will decrease in a monotonic fashion when undergoing habitat destruction(e.g.,the inundation of islands due to sea-level rise).Here,we develop a simple yet comprehensive patch-dynamic framework for complex food web metacommunities subject to the competition-colonization tradeof between basal species.We found that oscillations in food web topological complexity(characterized by species diversity,mean food chain length and the degree of omnivory)emerge along the habitat destruction gradient.This outcome is robust to changing parameters or relaxing the assumption of a strict competitive hierarchy.Having oscillations in food web complexity indicates that small habitat changes could have disproportionate negative efects on species diversity,thus the success of conservation actions should be evaluated not only on changes in biodiversity,but also on system robustness to habitat alteration.Overall,this study provides a parsimonious mechanistic explanation for the emergence of food web complexity in island ecosystems,further enriching our understanding of metacommunity assembly.展开更多
Stable carbon and nitrogen isotope ratios (δ13C and δ15N) are used to study the trophic structure of food web in the Yellow Sea and East China Sea ecosystem. The trophic con-tinuum of pelagic food web from phytoplan...Stable carbon and nitrogen isotope ratios (δ13C and δ15N) are used to study the trophic structure of food web in the Yellow Sea and East China Sea ecosystem. The trophic con-tinuum of pelagic food web from phytoplankton to top preyer was elementarily established, and a trophic structure diagram in the Yellow Sea and East China Sea was outlined in combination with carbon isotopic data of benthic organisms, which is basically consistent with and makes some improvements on the simplified Yellow Sea food web and the trophic structure diagram drawn based on the biomass of main resource population during 1985―1986. This result indicates that the stable isotope method is a potential useful means for further studying the complete marine food web trophic continuum from viruses to top predators and food web stability.展开更多
This study measured stable carbon and nitro- gen isotope ratios in phytoplankton, zooplankton, five inver- tebrates species, eight fishes species and three seabirds spe- cies collected in Bohai Bay. δ 13C ranged from...This study measured stable carbon and nitro- gen isotope ratios in phytoplankton, zooplankton, five inver- tebrates species, eight fishes species and three seabirds spe- cies collected in Bohai Bay. δ 13C ranged from ?25.38‰ to ?11.08‰ showing a relative low enrichment in the food web from Bohai Bay. The mean δ 13C of mullet is higher than that of other organisms, and this might be due to that mullet is migration fish and feeds mainly on inshore sources. δ 15N ranged from 4.08‰ to 13.98‰, and showed a step-wise en- richment with trophic level of 3.8‰. The δ 15N enrichment factor was used to construct an isotopic food web model to establish trophic relationships within this marine food web. According to this model, exact trophic levels of all organisms were estimated as 1.46?2.10, 1.91?3.32, 2.55?4.23 and 2.98?4.28 for plankton, invertebrates, fishes, and seabirds.展开更多
Sea ice in the western Antarctic Peninsula （WAP） region is both highly variable and rapidly changing. In the Palmer Station region, the ice season duration has decreased by 92 d since 1978. The sea-ice changes affec...Sea ice in the western Antarctic Peninsula （WAP） region is both highly variable and rapidly changing. In the Palmer Station region, the ice season duration has decreased by 92 d since 1978. The sea-ice changes affect ocean stratification and freshwater balance and in turn impact every component of the polar marine ecosystem. Long-term observations from the WAP nearshore and offshore regions show a pattern of chlorophyll （Chl） variability with three to five years of negative Chl anomalies interrupted by one or two years of positive anomalies （high and low Chl regimes）. Both field observations and results from an inverse food-web model show that these high and low Chl regimes differed significantly from each other, with high primary productivity and net community production （NCP） and other rates associated with the high Chl years and low rates with low Chl years. Gross primary production rates （GPP） averaged 30 mmolC.m^-2.d^-1 in the low Chl years and 100 mmolC.m-2.d1 in the high Chl years. Both large and small phytoplankton were more abundant and more productive in high Chl years than in low Chl years. Similarly, krill were more important as grazers in high Chl years, but did not differ from microzooplankton in high or low Chl years. Microzooplankton did not differ between high and low Chl years. Net community production differed significantly between high and low Chl years, but mobilized a similar proportion of GPP in both high and low Chl years. The composition of the NCP was uniform in high and low Chl years. These results emphasize the importance of microbial components in the WAP plankton system and suggest that food webs dominated by small phytoplankton can have pathways that funnel production into NCP, and likely, export.展开更多
作为海洋生态系统的关键组成部分,鱼类在食物网中的相对重要性直接影响着整个生态系统的稳定性。目前已使用了多个复杂网络中心性指标如Katz指数、PPR指数等来评估鱼类的重要性,但这些指标侧重点各不相同,为确保不同中心性指标对鱼类重...作为海洋生态系统的关键组成部分,鱼类在食物网中的相对重要性直接影响着整个生态系统的稳定性。目前已使用了多个复杂网络中心性指标如Katz指数、PPR指数等来评估鱼类的重要性,但这些指标侧重点各不相同,为确保不同中心性指标对鱼类重要性刻画的适用性,并能够综合评价鱼类对食物网稳定性的影响,本研究系统性定义了包括鱼类度中心性、鱼类信息中心性等的鱼类中心性指标,并提出一种多中心性指标相似度融合(Multi-centrality Index Similarity Fusion,MISF)方法。该方法构建包含多种网络中心性指标的鱼类特征矩阵,提出基于余弦相似度、欧氏距离和相对熵融合的鱼类相似度计算并使用熵权法确定各指标权重,最终实现鱼类综合重要性排序。本研究以2016—2018年珠江口海域鱼类捕食关系网数据为研究对象,开展了鱼类重要性评估,实验结果表明,与Katz指数、PPR指数等方法相比,该方法可以有效评估鱼类在食物网中的相对重要性。在2016和2018年数据集中,MISF方法的精确率和召回率分别达到1.0和0.5,显著优于其他方法,而在2017年数据集中,尽管网络规模增大导致精确率略低于Katz和PPR指数,但召回率表现更佳。此外,根据鱼类在食物网中的不同重要性级别,讨论了它们由于数量变动对网络稳定性产生的影响差异。本研究为鱼类资源管理提供了新的视角。展开更多
Trophic interactions,the fundamental links in food webs,are an important modulator of biodiversity structuring and ecosystem functioning.However,interactions between scorpions and insects remain poorly understood desp...Trophic interactions,the fundamental links in food webs,are an important modulator of biodiversity structuring and ecosystem functioning.However,interactions between scorpions and insects remain poorly understood despite their high biomass and diversity in natural ecosystems and more than 410 million years of evolutionary history.Here we summarize three trophic interaction types from 95 scorpion-insect species pairs in which both scorpions and insects were identified at least to the genus level.Predator-prey relationships were the most documented trophic interactions between scorpions and insects,involving 45 scorpion species from 9 families and 79 insect species from 11 orders.Prey-predator interactions were recorded between 11 species pairs of insects from four orders and scorpions from five families.Parasitiodism was documented between four dipterans(3 families)and five scorpions(3 families).The mega-diversity of insects and the high biomass of scorpion species in natural ecosystems imply that their complex trophic interactions await to be characterized.展开更多
基金supported by the National Key R&D Program of China(Nos.2019YFD0901204,2019YFD 0901205).
文摘Aggregation of species with similar ecological properties is one of the effective methods to simplify food web researches.However,species aggregation will affect not only the complexity of modeling process but also the accuracy of models’outputs.Selection of aggregation methods and the number of trophospecies are the keys to study the simplification of food web.In this study,three aggregation methods,including taxonomic aggregation(TA),structural equivalence aggregation(SEA),and self-organizing maps(SOM),were analyzed and compared with the linear inverse model–Markov Chain Monte Carlo(LIM-MCMC)model.Impacts of aggregation methods and trophospecies number on food webs were evaluated based on the robustness and unitless of ecological net-work indices.Results showed that aggregation method of SEA performed better than the other two methods in estimating food web structure and function indices.The effects of aggregation methods were driven by the differences in species aggregation principles,which will alter food web structure and function through the redistribution of energy flow.According to the results of mean absolute percentage error(MAPE)which can be applied to evaluate the accuracy of the model,we found that MAPE in food web indices will increase with the reducing trophospecies number,and MAPE in food web function indices were smaller and more stable than those in food web structure indices.Therefore,trade-off between simplifying food webs and reflecting the status of ecosystem should be con-sidered in food web studies.These findings highlight the importance of aggregation methods and trophospecies number in the analy-sis of food web simplification.This study provided a framework to explore the extent to which food web models are affected by dif-ferent species aggregation,and will provide scientific basis for the construction of food webs.
基金The Shandong Provincial Natural Science Foundation under contract No.ZR2023MD096the National Key R&D Program of China under contract Nos 2018YFD0900904 and 2018YFD0900906.
文摘Climate change has led to significant fluctuations in marine ecosystems,including alterations in the structure and function of food webs and ecosystem status.Coastal ecosystems are critical to the functioning of the earth’s lifesupporting systems.However,temporal variations in most of these ecosystems have remained unclear so far.In this study,we employed a linear inverse model with Markov Chain Monte Carlo(LIM-MCMC)combined with ecological network analysis to reveal the temporal variations of the food web in Haizhou Bay of China.Food webs were constructed based on diet composition data in this ecosystem during the year of 2011 and 2018.Results indicated that there were obvious temporal variations in the composition of food webs in autumn of 2011 and 2018.The number of prey and predators for most species in food web decreased in 2018 compared with 2011,especially for Trichiurus lepturus,zooplankton,Amblychaeturichthys hexanema,and Loligo sp.Ecological network analysis showed that the complexity of food web structure could be reflected by comprehensive analysis of compartmentalized indicators.Haizhou Bay ecosystem was more mature and stable in 2011,while the ecosystem’s self-sustainability and recovery from disturbances were accelerated from 2011 to 2018.These findings contribute to our understanding of the dynamics of marine ecosystems and highlight the importance of comprehensive analysis of marine food webs.This work provides a framework for assessing and comparing temporal variations in marine ecosystems,which provides essential information and scientific guidance for the Ecosystem-based Fisheries Management.
基金The National Natural Science Foundation of China under contract No.41676120。
文摘The tropical Pacific Ocean supports many productive commercial fisheries.However,few studies of ecosystem structure in the tropical Pacific Ocean have been carried out.In this study,we analyzed the food web structure in the central and eastern tropical Pacific Ocean based on trophic relationships of 35 pelagic species collected by Chinese tuna longline observers from June to November in 2017.Topology indices(node degree,D;centrality indices,BC and CC;topological importance indices,TI^1,TI^3;keystone indices,K,K_t and K_b)and Key-Player algorithms(KPP-1,KPP-2)were used to select key species and construct a simplified food web combined with body size data.The Kendall rank correlation and hierarchical clustering analysis indicated that different topology indices resulted in consistent rankings of key species.Most key species were the same as those selected in other studies in the Pacific Ocean,such as Shortbill spearfish(Tetrapturus angustirostris),Swordfish(Xiphias gladius),Albacore tuna(Thunnus alalunga),cephalopods and scomber.The food web would be separated into many unconnected parts(F=0.632,FD=0.795,R^D=0.957)after the removal of the five key species,indicating the key roles of these species in the food web structure and stability.Body size was considered an influential indicator in constructing the simplified food web.This study can improve our understanding of the food web structure in the tropical Pacific Ocean and provide scientific basis for further ecosystem dynamics studies.
基金Supported by the"Chen Guang"Project of Shanghai Municipal Education Commission(No.10CG52)the Shanghai Education Development Foundation(No.11YZ155)the National Natural Science Foundation of China(Nos.41206124,41541024)
文摘Food web structures are well known to vary widely among ecosystems. Moreover, many food web studies of lakes have generally attempted to characterize the overall food web structure and have largely ignored internal spatial and environmental variations. In this study, we hypothesize that there is a high degree of spatial heterogeneity within an ecosystem and such heterogeneity may lead to strong variations in environmental conditions and resource availability, in turn resulting in dif ferent trophic pathways. Stable carbon and nitrogen isotopes were employed for the whole food web to describe the structure of the food web in different sub-basins within Taihu Lake. This lake is a large eutrophic freshwater lake that has been intensively managed and highly influenced by human activities for more than 50 years. The results show significant isotopic dif ferences between basins with dif ferent environmental characteristics. Such differences likely result from isotopic baseline dif ferences combining with a shift in food web structure. Both are related to local spatial heterogeneity in nutrient loading in waters. Such variation should be explicitly considered in future food web studies and ecosystem-based management in this lake ecosystem.
基金The National Marine Public Welfare Project of China under contract No.201305005
文摘The food sources of aquacultured Apostichopus japonicus and the trophic levels of organisms in a sea cucumber（A. japonicus） and prawn（Penaeus japonica） polyculture system in a saltwater pond in Zhuanghe, Liaoning Province were examined using carbon and nitrogen stable isotopes. Across organisms, δ13C ranged from（–25.47±0.20）‰ to（–16.48±0.17）‰（mean±SD）, and δ15N ranged from（4.23±0.49）‰ to（12.44±0.09）‰. The δ13C and δ15N contents of A. japonicus, P. japonica and Fenneropenaeus chinensis were comparatively higher than those of other organisms. Values of δ13C and δ15N revealed that P. japonica, Hemigrapsus sanguineus and Neomysis japonica comprised the largest component of the diet of A. japonicus. The mean trophic level of the organisms in this saltwater pond polyculture system was（2.75±0.08）. P. japonica, A. japonicus, F. chinensis,Synechogobius hasta and Neomysis japonica were in the 3rd trophic level（2–3）; jellyfish, H. sanguineus and zooplankton were in the 2nd trophic level（1–2）; and Enteromorpha prolifera, benthic microalgae, periphyton and suspended matter primarily consisting of phytoplankton, bacteria and humus were in the primary trophic level（0–1）.
基金National Natual Science Foundation of China under contract No.39170172.
文摘By anayses of carbon isotopic composition (δ13C values) of the benthos collected in the Laoshan Bay in August 1993 and February and May 1994, it is found that the main food sources of the benthos can be divided into four groups in terms of carbon isotope composition: Particulate Organic Matter (POM), benthic diatoms, benthic macroalgae and the organic matter in sediments. The results show that the carbon isotopic composition of the benthic animals has a close relation with that of the food they take in. The Carbon isotopic compositions of benthos may be useful in elucidating their food sources. The carbon isotopic data have confirmed that POM is the main food source of the benthic filter feeders such as bivalves; crustaceans have a wide range of δ13C values, showing their food source has diversity; benthic diatoms are an important fraction of the food for most of gastropods. A preliminary investigation of the benthic-pelagic coupling in that region using the stable carban isotopic tracers has confirmed the importance of POM as a food source for benthos in this region, but the organic matter in sediments and benthic diatoms are also relatively important for a lot of benthic animals. The benthic-pelagic coupling in the Laoshan Bay temperate ecosystem is not so tight as that in ecosystems at higher latitudes such as northeastern water polynya.
文摘The worldwide increase in commercial fisheries and its impact on ecosystems as well as inefficient fishery management have led to overfishing and frequent breakdown of traditional fish stocks. In this context, an analysis of Khuzestan inshore fisheries data covering the years 2002-2011, was conducted in reliance on testing for occurrence of the fishing down marine food webs （FDMFW） phenomenon in the North of Persian Gulf Large Marine Ecosystem （LME）. In this study, the mean trophic level （mTL） and the fishing-in-balance （FIB）-index of Khuzestan landings during this period of time were estimated using the trophic level of 47 fishery resources. Increase in total landings （I1） was observed, which explained the high fishing yield in major fishery resources （especially demersal）. Moreover, the moderates decreasing trend in mTL per decade, and the increasing trend in FIB-index were observed. The status of fishery resources in Khuzestan inshore waters （under exploited but not overexploited）, the rise in Y, FIB and slightly drop in mTL can be considered as indirect indicators of the fishing impacts on the trophic structure of marine communities. Based on this result, probability occurrence of FDMFW process in Khuzestan inshore waters is low to some extent. However, we suggest that the goal of management programs in Khuzestan inshore waters should prevent the continuance of this trend in the long-term using an ecosystem-based approach.
基金Supported by the Special Research Fund for the National Non-profit Institutes (East China Sea Fishery Research Institute) (No. 2007M03)Shanghai Jingshan City Beach Management Co. Ltd, and the National Basic Research Program of China (973 Program) (No.2010CB429005)
文摘Stable isotope values, δ13C and δ15N, were determined for four primary producers and 19 dominant consumers in a small artificial lagoon located in Hangzhou Bay. Based on these results the major pathways for energy flow and trophic structure of the artificial lagoon ecosystem were characterized. The mean δ13C values for the 19 consumers ranged from -22.99‰ to -14.24‰. Apart from so-iny mullet Liza haematocheila, the other 18 consumers had intermediate δ13C values between those of epibenthic microalgae and particulate organic matter (POM). The results of a multiple source linear mixing model (IsoSource model) indicated that 50% or more of the organic carbon in the tissues of most consumers was derived from epibenthic microalgae. This indicated that these primary producers were the main food source fueling the lagoon food web. The mean δ15N values for the 19 consumers varied between 4.93‰ and 12.97‰ and indicated four trophic levels in the lagoon. Four macroinvertebrates and zooplankton represented the primary consumers, whilst the other 14 consumers occupied the secondary and tertiary consumer levels. The 19 consumers were divided into three trophic guilds (detritivores/suspension feeders, omnivores and carnivores).
基金The National Key R&D Program of China under contract No.2018YFD0900904the National Natural Science Foundation of China under contract Nos 31772852 and 31802301。
文摘Single-species management ignores the interactions between species,and ecosystem-based fisheries management(EBFM)has become a main method to fisheries management.Understanding food web structures and species interactions is essential for the implementation of EBFM and maintenance of ecosystem functions.Overfishing is one of the main reasons behind the depletion,which could even lead to the depletion of some target species in local areas.So understanding the impacts of species depletion on food web structures is important for the implementation of EBFM.The impacts of species depletion can be transmitted through the food web and cause the local extinction of both target and non-target species.In this study,topological network analysis was applied to examine the impacts of species depletion on the food web structure of Haizhou Bay.Results showed that fine crayfish Leptochela gracilis,squid Loligo sp.,and Japanese snapping shrimp Alpheus japonicus have the highest numbers of outgoing links(48,32 and 31 respectively);thus,these species may be considered key prey species.Whitespotted conger Conger myriaster,fat greenling Hexagrammos otakii,and bluefin gurnard Chelidonichthys kumu were key predators with the highest number of incoming links(37,36 and 35 respectively).The competition graphs derived from the Haizhou Bay food web were highly connected(more than 40%predators sharing over 10 common prey species),and showed close trophic interaction between high trophic level fishes.Simulation analysis showed that the food web structure has small changes to the depletion of species in a highly complex food web.The most-connected target species did not necessarily indicate high structural importance;however,some species with low connectivity may demonstrate stronger trophic interactions and play important ecological roles in the food web.But most species were more sensitive to the depletion of the most-connected target species than other target species(for instance,for zooplankton,closeness centrality 13.876 in D6,but closeness centrality 82.143 in original food web).Therefore,EBFM should focus on the most-connected target species,but also on those species with few but strong links and feeding relationships in the food web.
基金The National Natural Science Foundation of China under contract Nos NSFC41306127 and NSFC41276156the Funding Program for Outstanding Dissertations in Shanghai Ocean University+1 种基金Shanghai Leading Academic Discipline Project(Fisheries Discipline)the involvement of Y.Chen was supported by SHOU International Center for Marine Studies and Shanghai 1000Talent Program
文摘Mean trophic level of fishery landings（MTL） is one of the most widely used biodiversity indicators to assess the impacts of fishing. Based on the landing data compiled by Food and Agriculture Organization combined with trophic information of relevant species in Fish Base, we evaluated the status of marine fisheries from 1950 to 2010 for different coastal states in Pacific, Atlantic and Indian Oceans. We found that the phenomenon of ＂fishing down marine food webs＂ occurred in 43 states. Specifically, 27 states belonged to ＂fishing-through＂ pattern, and 16 states resulted from ＂fishing-down＂ scenario. The sign of recovery in MTL was common in the Pacific, Atlantic and Indian Oceans（occurred in 20 states）, but was generally accompanied by significantly decreased catches of traditional low trophic level species. In particular, 11 states showed significant declining catches of lower trophic levels. The MTL-based assessment of ＂fishing down marine food webs＂ needs to be interpreted cautiously.
基金Supported by Public Science and Technology Research Funds Projects of Ocean(200905005-05)Special S&T Program for Key Independent Innovation in Guangdong Province(2007A032600004)
文摘To investigate the food web structure of Liusha Bay,the δ13C and δ15N values of various organisms collected in Liusha Bay were measured via stable isotope technique.Based on the calculated δ15N value,the correlation between stable isotope ratio and trophic level were established to predict the trophic levels of shrimps,crabs,cephalopods and fishes.By comparing the analysis results of stomach contents of 24 organisms,two methods gave a similar consistence in approximately 71% of organisms within a 0.5 trophic level.It is concluded that stable isotope technique could be an effective method for studying ocean food web trophic level.
文摘An artificial aquatic food web (AAFW) system was designed to remove the non-point source pollutants in eutrophic Jiyu river. A certain amount of Scenedesmus obliquus and Daphnia pulex was cultured in the system for the control of serious cyanobacterial bloom. The AAFW system was a continuous-flow system including one storage basin of 3 m<sup>3</sup> capacity with polluted river water (the total nitrogen-TN: 4.49 mg⋅l<sup>-1</sup><sup></sup>;the total phosphorus-TP: 0.192 mg⋅l-1</sup></sup><sup></sup>), one phytoplankton tank of 3 m<sup>3</sup> capacity with an initial concentrations of S. obliquus about 5.8 × 10<sup>3</sup> ind⋅l-1</sup><sup></sup>, and one zooplankton growth chamber of 1.5 m<sup>3</sup> capacity with an initial abundance of D. pulex about 22.5 ind⋅l-1</sup></sup>. The system was optimized by setting hydraulic retention time of phytoplankton tank as 5 days and the experiments were operated for 45 days. Compared with the polluted river, TN and TP were removed about 28% and 47% by the AAFW system, respectively. The biomass of phytoplankton decrease from 6.33 mg⋅l-1<sup></sup> to 1.48 mg⋅l-1</sup><sup></sup> and the percentage of cyanobacteria decrease from 43.93% to 2.36%, the biomass of Crustacean zooplankton increase from 0.34 mg⋅l-1</sup></sup><sup></sup> to 1.53 mg⋅l-1</sup></sup><sup></sup> and the percentage of D. pulex increase from 19.19% to 57.62%. Our results indicated that the AAFW system not only is an efficient, flexible system for reducing nutrient levels in tributary rivers, but also has an ability to control the cyanobacteria bloom and rebuilding the aquatic ecosystem from the polluted river water.
基金J.L.is supported by the Natural Science Foundation of China(No.32271548&31901175).
文摘Exploring how food web complexity emerges and evolves in island ecosystems remains a major challenge in ecology.Food webs assembled from multiple islands are commonly recognized as highly complex trophic networks that are dynamic in both space and time.In the context of global climate change,it remains unclear whether food web complexity will decrease in a monotonic fashion when undergoing habitat destruction(e.g.,the inundation of islands due to sea-level rise).Here,we develop a simple yet comprehensive patch-dynamic framework for complex food web metacommunities subject to the competition-colonization tradeof between basal species.We found that oscillations in food web topological complexity(characterized by species diversity,mean food chain length and the degree of omnivory)emerge along the habitat destruction gradient.This outcome is robust to changing parameters or relaxing the assumption of a strict competitive hierarchy.Having oscillations in food web complexity indicates that small habitat changes could have disproportionate negative efects on species diversity,thus the success of conservation actions should be evaluated not only on changes in biodiversity,but also on system robustness to habitat alteration.Overall,this study provides a parsimonious mechanistic explanation for the emergence of food web complexity in island ecosystems,further enriching our understanding of metacommunity assembly.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.40276046&40146027)the Major State Basic Research Development Program(Grant No.G1999043710).
文摘Stable carbon and nitrogen isotope ratios (δ13C and δ15N) are used to study the trophic structure of food web in the Yellow Sea and East China Sea ecosystem. The trophic con-tinuum of pelagic food web from phytoplankton to top preyer was elementarily established, and a trophic structure diagram in the Yellow Sea and East China Sea was outlined in combination with carbon isotopic data of benthic organisms, which is basically consistent with and makes some improvements on the simplified Yellow Sea food web and the trophic structure diagram drawn based on the biomass of main resource population during 1985―1986. This result indicates that the stable isotope method is a potential useful means for further studying the complete marine food web trophic continuum from viruses to top predators and food web stability.
基金This work was supported by the National Basic Research Program of China(Grant No.2003CB415004)the National Natural Science Foundation of China(Grant No.40021101)the Japanese Intermational Cooperation Agency.
文摘This study measured stable carbon and nitro- gen isotope ratios in phytoplankton, zooplankton, five inver- tebrates species, eight fishes species and three seabirds spe- cies collected in Bohai Bay. δ 13C ranged from ?25.38‰ to ?11.08‰ showing a relative low enrichment in the food web from Bohai Bay. The mean δ 13C of mullet is higher than that of other organisms, and this might be due to that mullet is migration fish and feeds mainly on inshore sources. δ 15N ranged from 4.08‰ to 13.98‰, and showed a step-wise en- richment with trophic level of 3.8‰. The δ 15N enrichment factor was used to construct an isotopic food web model to establish trophic relationships within this marine food web. According to this model, exact trophic levels of all organisms were estimated as 1.46?2.10, 1.91?3.32, 2.55?4.23 and 2.98?4.28 for plankton, invertebrates, fishes, and seabirds.
基金supported by NSF Polar Programs awards ANT-1344502 and PLR-1440435 to HWD at Lamont-Doherty Earth ObservatorySFS and SCD were supported partly by Woods Hole Oceanographic Institution
文摘Sea ice in the western Antarctic Peninsula （WAP） region is both highly variable and rapidly changing. In the Palmer Station region, the ice season duration has decreased by 92 d since 1978. The sea-ice changes affect ocean stratification and freshwater balance and in turn impact every component of the polar marine ecosystem. Long-term observations from the WAP nearshore and offshore regions show a pattern of chlorophyll （Chl） variability with three to five years of negative Chl anomalies interrupted by one or two years of positive anomalies （high and low Chl regimes）. Both field observations and results from an inverse food-web model show that these high and low Chl regimes differed significantly from each other, with high primary productivity and net community production （NCP） and other rates associated with the high Chl years and low rates with low Chl years. Gross primary production rates （GPP） averaged 30 mmolC.m^-2.d^-1 in the low Chl years and 100 mmolC.m-2.d1 in the high Chl years. Both large and small phytoplankton were more abundant and more productive in high Chl years than in low Chl years. Similarly, krill were more important as grazers in high Chl years, but did not differ from microzooplankton in high or low Chl years. Microzooplankton did not differ between high and low Chl years. Net community production differed significantly between high and low Chl years, but mobilized a similar proportion of GPP in both high and low Chl years. The composition of the NCP was uniform in high and low Chl years. These results emphasize the importance of microbial components in the WAP plankton system and suggest that food webs dominated by small phytoplankton can have pathways that funnel production into NCP, and likely, export.
文摘作为海洋生态系统的关键组成部分,鱼类在食物网中的相对重要性直接影响着整个生态系统的稳定性。目前已使用了多个复杂网络中心性指标如Katz指数、PPR指数等来评估鱼类的重要性,但这些指标侧重点各不相同,为确保不同中心性指标对鱼类重要性刻画的适用性,并能够综合评价鱼类对食物网稳定性的影响,本研究系统性定义了包括鱼类度中心性、鱼类信息中心性等的鱼类中心性指标,并提出一种多中心性指标相似度融合(Multi-centrality Index Similarity Fusion,MISF)方法。该方法构建包含多种网络中心性指标的鱼类特征矩阵,提出基于余弦相似度、欧氏距离和相对熵融合的鱼类相似度计算并使用熵权法确定各指标权重,最终实现鱼类综合重要性排序。本研究以2016—2018年珠江口海域鱼类捕食关系网数据为研究对象,开展了鱼类重要性评估,实验结果表明,与Katz指数、PPR指数等方法相比,该方法可以有效评估鱼类在食物网中的相对重要性。在2016和2018年数据集中,MISF方法的精确率和召回率分别达到1.0和0.5,显著优于其他方法,而在2017年数据集中,尽管网络规模增大导致精确率略低于Katz和PPR指数,但召回率表现更佳。此外,根据鱼类在食物网中的不同重要性级别,讨论了它们由于数量变动对网络稳定性产生的影响差异。本研究为鱼类资源管理提供了新的视角。
基金supported by the S&T Program of Hebei(the Natural Science Foundation of Hebei,C2024204233)the National Natural Science Foundation of China(32170455)the State Key Laboratory of North China Crop Improvement and Regulation(YJ2020028)。
文摘Trophic interactions,the fundamental links in food webs,are an important modulator of biodiversity structuring and ecosystem functioning.However,interactions between scorpions and insects remain poorly understood despite their high biomass and diversity in natural ecosystems and more than 410 million years of evolutionary history.Here we summarize three trophic interaction types from 95 scorpion-insect species pairs in which both scorpions and insects were identified at least to the genus level.Predator-prey relationships were the most documented trophic interactions between scorpions and insects,involving 45 scorpion species from 9 families and 79 insect species from 11 orders.Prey-predator interactions were recorded between 11 species pairs of insects from four orders and scorpions from five families.Parasitiodism was documented between four dipterans(3 families)and five scorpions(3 families).The mega-diversity of insects and the high biomass of scorpion species in natural ecosystems imply that their complex trophic interactions await to be characterized.
