大宁河下游主要鱼类营养结构的时空变化

为了解大宁河下游主要鱼类食物网营养结构的时空变化特征,应用稳定同位素技术分析了大宁河下游巫山和大昌2个采样点在不同水位时期鱼类的碳、氮稳定同位素比值,并计算了δ13C-δ15N同位素生态位中的6个营养结构的量化指标。结果表明,不同水域的颗粒有机物(POM)的δ13C值随与河口距离而减小,δ15N值与河口距离无显著相关性。同种鱼类的δ13C值均无显著性差异;除了5月,巫山站点与大昌站点同种鱼类的δ15N值无显著性差异外,其他不同站点、不同水位时期同种鱼类的δ15N值均存在显著性差异。对同种鱼类组成的鱼类群落同位素量化指标比较发现,巫山站点10月鱼类群落的营养多样性指标及营养位置高于5月群落;大昌站点,不同水位时期的各指标变化趋势与巫山站相反。出现这种变化的原因可能是由于目前大宁河静水水域存在丰富的饵料导致。各鱼类群落营养结构的时空变化并未显示出处明显的规律性,可能与采样时间、鱼类种类的选择和样本量的大小有关。基于各种同位素值量化的生态指标应用于大宁河水域的鱼类食物网结构变化特征的研究,能为大宁河渔业生态调控措施以及渔业生态系统重建与修复提供理论依据。     

应用碳、氮稳定同位素研究鄱阳湖枯水末期水生食物网结构

稳定碳、氮同位素比值分析技术是研究生态系统中物质循环与能量流动的有效技术.δ13C值常用来分析消费者食物来源,δ15N值常用来确定生物在食物网中的营养位置.应用稳定同位素技术分析了鄱阳湖北部湖口县、都昌县、星子县、吴城镇4个采样点95条鱼和其他食物网成分样品的碳、氮稳定同位素比值,构建了鄱阳湖枯水期末期水生食物网.结果表明,不同水域颗粒有机物(POM)的δ13C值不同,范围为-27.5‰～-24.6‰可以区分赣江、修水、鄱阳湖、长江和鄱阳湖湖交汇处水体的颗粒有机物特征.江西鄱阳湖国家级自然保护区受人类活动干扰少,核心区生物δ15N相对较低,而周边人类活动频繁的星子、都昌两县附近水域生物体内的δ15N偏高,反映了人类活动引起的营养输入对系统的影响.在湖区不同位置捕获的相同品种水生生物δ13C值不同,反映了其不同的食物来源,用δ15N值计算发现其所占据的相对营养位置较为一致.     

川东南小型水库营养结构特征的稳定C、N同位素分析

为了解我国水库生态系统营养结构特征, 研究应用稳定同位素技术分析了四川省东南部的典型小型水库松林水库中不同水生生物碳、氮稳定性同位素比值。基于Bayesian混合模型(SIAR)分析了不同消费者基础碳来源, 并计算了δ13C–δ15N同位素生态位中6个营养结构量化指标。结果表明: 调查期间松林水库处于富营养化状态; 初级生产者POM(主要成分为浮游藻类)、固着藻类、喜旱莲子草Alternanthera philoxeroides和水蓼Polygonum hydropiper的δ13C值范围为–29.20‰—18.81‰, δ15N值范围为4.01‰—12.73‰; 其中POM和固着藻类是多数消费者的主要碳源; 松林水库食物网营养级长度为3级, 以杂食性鱼类为优势类群并存在营养冗余现象, 暗示了该生态系统鱼类群落结构的相对稳定性; 入侵物种福寿螺Pomacea lineata、罗非鱼Oreochromis spp.与土著物种铜锈环棱螺Bellamya aeruginosa、鲫Carassius auratus等之间存在明显的同位素生态位重叠现象。建议加强水生生物资源管理, 减少外来物种入侵对当地土著物种的保护具有重要意义。     

三峡库区小江库湾鱼类食物网的稳定C、N同位素分析

应用稳定碳(δ₁₃C)、氮(δ₁₅N)同位素探讨了三峡库区一级支流小江库湾枯水期(2010.7)和丰水期间(2010.12)鱼类食物网结构。研究结果显示：初级生产者颗粒有机物(POM)和固着藻类δ₁₃C、δ₁₅N值范围分别为-23.33‰～-21.05‰、-25.13‰～-24.54‰,3.99‰～6.25‰、4.64‰～4.79‰。POM和固着藻类构成了小江库湾食物网能量的主要来源,其中丰水期间陆生营养物质输入是其食物网能量来源的一种重要补充途径。小江库湾常见鱼类食性可分为杂食偏植物食性、杂食偏动物食性及动物食性3种营养类群。在不同时期(枯水期和丰水期)小江库湾鱼类食物网营养级长度均有三级并且存在4种主要营养路径,表明了在三峡工程运行初期小江库湾已经形成了相对稳定的食物网结构。研究为小江库湾鱼类资源管理及生态系统恢复提供了一定的指导意义。     

太湖贡湖湾食物网特征研究

应用稳定性同位素技术(13C和15N)研究了太湖贡湖湾食物网特征, 结果显示由于食物来源变化多样性影响, 导致贡湖的食物网结构和营养级关系变化较为复杂, 贡湖主要生物类群13C、15N值表现出较大的种间差异。消费者13C值从摇蚊幼虫的-32.3到锯齿米虾的-22.1, 其值大小与营养级的关系没有规律性。消费者平均15N值从褶纹冠蚌的10.3到位于顶端间下鳙的19.0, 随营养级位置而升高。群落中所有种类的15N、13C值之间没有相关性(r=0.1835, P0.05), 表明该食物网是非线性食物网。研究结果验证了杂食性生物有机体普遍存在于富营养化的贡湖水域生态系统中, 且13C结果表明, 浮游植物、固着藻类以及沉水植物为贡湖食物网中大多数生物有机体的主要碳源。贡湖食物链长度为4.44营养级。     

应用碳、氮稳定同位素研究稻田多个物种共存的食物网结构和营养级关系

稳定碳、氮同位素比值分析技术是研究生态系统中物质循环与能量流动的有效技术。δ13C值常用来分析消费者食物来源,δ15N值常用来确定生物在食物网中的营养位置。应用稳定同位素技术分析了稻-鱼(R-F)和稻-鱼-鸭(R-F-D)两种稻作方式下,稻田多个物种共存的食物网结构和营养级关系。结果表明,R-F中SOM的δ13C值为(-27.7±0.3)‰,与R-F-D(-27.4±0.4)‰,相差不大;R-F中POM的1δ3C值为(-27.4±0.8)‰,低于稻鱼鸭共生田(-26.7±0.5)‰;δ15N值计算发现R-F内浮游动物的营养级位置在2.24±0.16,鱼的营养级位置在3.07±0.26,均高于其在R-F-D内的营养级。在R-F-D内,由于鸭的引入,和R-F相比,鱼的营养级降低为2.63±0.13。     

应用碳氮稳定同位素技术研究江豚(Neophocaena asiaeorientalis ssp. sunameri)食性

稳定同位素技术已广泛地用于分析生态系统中食物网的食物来源和营养级关系,但在海洋哺乳动物食性方面应用较少。通过分析2012年4—6月在辽东湾沿岸海域搁浅而死亡的江豚样本和同时期(6月)取自辽东湾海域主要渔获物的碳氮稳定同位素比值,研究了江豚(Neophocaena asiaeorientalis ssp.sunameri)及其可能摄食饵料的碳氮稳定同位素组成。结果表明:江豚δ13C值为(-18.4±0.3)‰,δ15N值为(13.8±0.4)‰。28种可能生物饵料的δ13C值的范围为-19.5‰—-17.0‰,δ~(15)N值的范围为11.4‰—14.0‰。江豚的营养级为4.5,高于传统胃含物分析法的研究结果。28种测试生物的营养级位于3.8—4.6之间。江豚的食物来源主要以鱼类为主,对食物种类的喜食顺序为中上层鱼类中下层鱼类底层鱼类头足类虾类蟹类,其平均贡献率分别为43.9%、18.2%、13.1%、10.0%、8.8%、6.0%。江豚碳氮稳定同位素比值与体长无明显的线性关系,碳营养源较为稳定,氮营养源复杂多变。     

运用稳定同位素技术分析三峡坝前水域的食物网结构

选择茅坪水域和香溪河水域作为坝前干支流的代表性水域, 采样分析了碳、氮稳定同位素(δ13C、δ15N), 并据此了解食物网结构。结果显示, 坝前干流水域鱼类δ13C范围是-33.5‰--19.4‰, 支流水域鱼类δ13C为-28.3‰--13.9‰, 两水域同种鱼类δ13C值差异在1‰-8.9‰之间,说明两地同种鱼类食源存在一定差异; 干流鱼类δ15N范围是6.72‰-15.29‰, 支流水域鱼类δ15N范围是4.8‰-14.4‰, 干流鱼类δ15N的平均值(11.1‰)大于支流(10.1‰), 且干流每种鱼类δ15N均大于支流的同种鱼类。对颗粒有机物(POM)的δ15N分析发现, 其范围在3.61‰-5.76‰, 将其作为初级生产者进行相对营养级分析, 干流鱼类的平均相对营养位置为3.00, 食物链长度为4.35; 支流鱼类的平均相对营养位置为2.64, 食物链长度为3.9。在计算得到的反映鱼类群落的营养结构得的碳氮同位素指标中, 香溪河水域食物网的总面积(TA)、平均最邻近距离(NND)和最邻近距离标准差(SDNND)均大于坝前干流水域, 说明坝前干流水域的鱼类营养结构更为冗余。研究表明坝前干流水域食物链长度比香溪河支流水域食物链长度更长; 坝前干流水域食物网结构较香溪河更稳定, 坝前干流不同鱼类的种间竞争较支流水域更激烈, 坝前干支流均存在中间生态位较拥挤的情况。     

基于碳、氮稳定同位素技术的东太湖水生食物网结构

稳定同位素技术是研究生态系统食物网中物质循环与能量流动的有效技术之一。碳稳定同位素比值(δ13C)常用来分析消费者食物来源,而氮稳定同位素比值(δ15N)常用来确定生物在食物网中的营养位置。本研究应用碳、氮稳定同位素技术构建了东太湖食物网结构。结果表明:东太湖食物网主要由两条营养传递途径组成,即浮游植物为初级生产者的浮游营养传递途径和苦草等大型水生植物为初级生产者的近岸底层营养传递途径,湖中9种主要鱼虾类能量主要来自近岸底层传递;翘嘴鲌(Erythroculter ilishaeformis)、鳜(Siniperca chuatsi)和鲶(Silurus sp.)作为湖泊中的顶极捕食者,具有相对最高的营养级,并占据食物网的顶层。     

基于稳定同位素的湿地食物源判定和食物网构建研究进展

湿地生物营养动力学是湿地生态系统结构和功能评价研究的基础.碳、氮稳定同位素作为识别营养关系的方法,已在湿地生态系统食物来源、组成和食物链传递研究中得到广泛运用.本文系统综述了稳定同位素食物贡献度计算模型和营养级确定的基本方法和理论;讨论了动物营养分馏值和基线的选择依据;概括了湿地生态系统典型食物源及其稳定同位素变化特征;总结了草食、杂食和肉食等不同营养级动物的食物来源.指出了稳定同位素在湿地食物源溯源和食物网研究中的不足;基于国内外研究现状和发展趋势及需求,展望了未来同位素技术在湿地食物网生态学研究中的运用前景和研究重点,提出需要加强稳定同位素营养分馏和基线的影响因素、样品处理和保存方式研究以及胃含物、分子标记物和多元素同位素结合分析.     

Trophic interactions in the Zoige Alpine wetland on the eastern edge of the Qinghai–Tibetan Plateau inferred by stable isotopes

The Zoige wetland ecosystem of the eastern edge of the Qinghai–Tibetan Plateau is the largest plateau peat bog worldwide and an important biodiversity conservation centre in China. Nevertheless, limited information is available about this Alpine wetland aquatic ecosystem, including its food-web structure and complexity. In this study, we analysed the trophic interactions among dominant organisms in the food web of this Alpine wetland aquatic ecosystem and assessed the importance of allochthonous and autochthonous carbon sources during the wet season using δ¹³C and δ¹⁵N analysis. The results supported the hypothesis that the food web of the Zoige Alpine wetland is largely maintained by allochthonous carbon sources rather than autochthonous food sources during the wet season when the allochthonous resource availability is relatively high. The food web contains approximately three trophic levels, and Schizopygopsis pylzovi (a genus of cyprinid fish) is the top predator. Intermediate trophic positions, including zooplankton and macroinvertebrates, represent the primary animal community in the food web. The allochthonous carbon sources are transferred to the food web via these macroinvertebrates (e.g., Ecdyonurus sp. and Sigara substriata). Although our findings show a low biodiversity in the Zoige wetland during the wet season, the trophic redundancy in the food-web structure could support the stability of the Zoige Alpine wetland aquatic ecosystem.     

Establishment of trophic continuum in the food web of the Yellow Sea and East China Sea ecosystem: Insight from carbon and nitrogen stable isotopes

The determination of trophic level for the biology in a marine ecosystem is very important as alteration of its structure and function may be reflected in the tro-phic level of component species. A change in trophic level indicates variation in an organism’s feeding bi-ology or in the pathway of energy flow from primary producers to the consumer. The gut content analysis is a traditional method for studying trophodynamics of food web in marine ecosystems. Species composition and amounts in al…     

Establishment of trophic continuum in the food web of the Yellow Sea and East China Sea ecosystem: Insight from carbon and nitrogen stable isotopes

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 continuum 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.     

互花米草入侵对黄河三角洲秋季底栖食物网的影响

为了保滩护岸,互花米草于1990年被引种至黄河三角洲,随后迅速蔓延,给滨海湿地生态系统带来了严重威胁。为了明晰互花米草入侵对黄河三角洲湿地底栖食物网结构的影响,本研究基于稳定同位素技术,于2020年11月对互花米草入侵区域大型底栖动物的潜在食源、营养级和食物网结构进行了采样分析。结果表明: 调查区域潜在食源δ¹³C平均值的变化规律为沉积物(SOM)>互花米草>底栖微藻>悬浮颗粒物(POM)>盐地碱蓬,潜在食源δ¹⁵N值的变化范围为1.24‰～9.03‰,且不同食源间的δ¹⁵N值存在差异。调查区域大型底栖动物的营养级范围为1.73～4.19,其中双壳类的营养级最低;互花米草及其腐败后的碎屑是大型底栖动物的重要食源之一,但对大型底栖动物的营养级结构没有显著影响。互花米草入侵通过上行效应改变了底栖生物的食源组成,进而可能影响黄河三角洲湿地食物网的结构。     

人为营养物质输入对汉丰湖不同营养级生物的影响--稳定C、N同位素分析

以长江一级支流小江上游的汉丰湖为研究对象,设置了4个采样点(影响组:A, B;对照组:C, D),应用碳、氮稳定性同位素探讨人类生活污水和农业面源污染对汉丰湖水生生态系统中不同营养级水平生物类群的影响。结果表明:影响组POM(颗粒有机物)和螺类碳、氮稳定性同位素比值范围分别为-25.93‰--24.63‰、4.12‰-9.86‰,-14.28‰--21.60‰、7.97‰-19.99‰;对照组POM(颗粒有机物)和螺类碳、氮稳定性同位素比值范围分别为-25.62‰--22.51‰、0.01‰-6.56‰,-22.96‰--19.21‰、6.75‰-8.89‰;不同组间POM和初级消费者螺类碳同位素比值无明显空间变化(P>0.05), 而氮稳定性同位素比值空间变化显著(P<0.05)。因此,在汉丰湖食物网中,氮稳定性同位素特征更好地反应了营养物质(人为输入)吸收和富集的信息。与固着藻类、鱼类等相比,POM和软体动物螺类更适合作为环境评价的指示物。影响组A、B样点的部分生物类群已经受到了人为营养物质输入的影响,影响强度B样点区域>A样点区域。结果建议加强汉丰湖水环境保护,控制污水排放量及提高污水处理水平,对于保护小江和三峡库区水质具有十分重要的意义。     

Uncovering trophic positions and food resources of soil animals using bulk natural stable isotope composition

Despite the major importance of soil biota in nutrient and energy fluxes, interactions in soil food webs are poorly understood. Here we provide an overview of recent advances in uncovering the trophic structure of soil food webs using natural variations in stable isotope ratios. We discuss approaches of application, normalization and interpretation of stable isotope ratios along with methodological pitfalls. Analysis of published data from temperate forest ecosystems is used to outline emerging concepts and perspectives in soil food web research. In contrast to aboveground and aquatic food webs, trophic fractionation at the basal level of detrital food webs is large for carbon and small for nitrogen stable isotopes. Virtually all soil animals are enriched in ¹³C as compared to plant litter. This ‘detrital shift’ likely reflects preferential uptake of ¹³C‐enriched microbial biomass and underlines the importance of microorganisms, in contrast to dead plant material, as a major food resource for the soil animal community. Soil organic matter is enriched in ¹⁵N and ¹³C relative to leaf litter. Decomposers inhabiting mineral soil layers therefore might be enriched in ¹⁵N resulting in overlap in isotope ratios between soil‐dwelling detritivores and litter‐dwelling predators. By contrast, ¹³C content varies little between detritivores in upper litter and in mineral soil, suggesting that they rely on similar basal resources, i.e. little decomposed organic matter. Comparing vertical isotope gradients in animals and in basal resources can be a valuable tool to assess trophic interactions and dynamics of organic matter in soil. As indicated by stable isotope composition, direct feeding on living plant material as well as on mycorrhizal fungi is likely rare among soil invertebrates. Plant carbon is taken up predominantly by saprotrophic microorganisms and channelled to higher trophic levels of the soil food web. However, feeding on photoautotrophic microorganisms and non‐vascular plants may play an important role in fuelling soil food webs. The trophic niche of most high‐rank animal taxa spans at least two trophic levels, implying the use of a wide range of resources. Therefore, to identify trophic species and links in food webs, low‐rank taxonomic identification is required. Despite overlap in feeding strategies, stable isotope composition of the high‐rank taxonomic groups reflects differences in trophic level and in the use of basal resources. Different taxonomic groups of predators and decomposers are likely linked to different pools of organic matter in soil, suggesting different functional roles and indicating that trophic niches in soil animal communities are phylogenetically structured. During last two decades studies using stable isotope analysis have elucidated the trophic structure of soil communities, clarified basal food resources of the soil food web and revealed links between above‐ and belowground ecosystem compartments. Extending the use of stable isotope analysis to a wider range of soil‐dwelling organisms, including microfauna, and a larger array of ecosystems provides the perspective of a comprehensive understanding of the structure and functioning of soil food webs.     

δ13C and δ15N indicators of fish and shrimp community diet and trophic structure in a mangrove ecosystem in Thailand

Stable carbon and nitrogen isotope ratios were used to elucidate primary carbon sources and trophic relationships of the fish and shrimp community in the Klong Ngao mangrove ecosystem, southern Thailand. There were no significant differences in isotopic compositions of biota between mangrove and offshore sites (Welch–Aspin test). The δ¹⁵N values of eight fish species and two shrimp species at both sites were also not significantly different by the test, meaning that at both sites they feed on the same diets due to the discharge of large quantities of mangrove sediments. The δ¹⁵N isotopic enrichment of consumers suggested that there are four trophic levels in the Klong Ngao food web, with at least two fish species capable of switching feeding strategies and thus altering their apparent trophic positions. Phytoplankton culture experiments indicated that mangrove-derived sediments could play an important role in stimulating phytoplankton growth for low turbidity offshore areas, thus providing an alternate food source. The isotopic associations among sources and consumers indicated that mangroves were the major carbon source supporting aquatic food webs in the Klong Ngao ecosystem.     

An assessment,using stable isotopes,of the importance of allochthonous organic carbon sources to the pelagic food web in Loch Ness

The natural abundance of stable isotopes (δ¹³C and δ¹³15N) was determined for components of the pelagic food web in Loch Ness, a deep oligotrophic lake in northern Scotland, and compared with values from the inflow rivers and the catchment vegetation. Phytoplankton δ¹³C was low compared to values reported from other lakes, possibly reflecting a high use of ¹³C-depleted carbon dioxide from respired organic matter before further isotopic fractionation during photosynthesis. Phytoplankton δ¹³C was appreciably lower than that of dissolved and particulate organic matter (DOM and POM) in the loch. The DOM and POM were evidently overwhelmingly of allochthonous origin and ultimately derived from terrestrial plant detritus. The distinctive δ¹³C values for phytoplankton and detritus in the loch allowed the use of food sources by grazing crustacean zooplankton to be assessed, and the contributions of phytoplankton carbon and detrital carbon to zooplankton total body carbon appeared to be about equal. Comparison of δ¹³C and δ¹⁵N values for zooplankton and fish allowed assessment of trophic structure in the loch. The very high dependence of the pelagic food web in Loch Ness on allochthonous organic matter inputs from the catchment may be exceptional in a large lake, but has important implications for our understanding of lake ecosystem processes as well as for lake management.