应用稳定同位素技术构建胶州湾食物网的连续营养谱

根据2011年春季和秋季在胶州湾进行的渔业资源综合调查,应用稳定同位素示踪技术,分析了胶州湾主要渔业生物的碳、氮稳定同位素比值(δ13C,δ15N),并计算其营养级,进而构建胶州湾食物网的连续营养谱。分析的生物种类包括浮游植物、浮游动物、大型无脊椎动物和鱼类,其生物量之和占总渔获量的95%。结果表明,胶州湾食物网的δ13C值范围是-25.63‰—-17.16‰,跨度为8.47‰,平均值为(-19.42±1.80)‰;δ15N值范围是4.15‰—14.11‰,跨度为9.96‰,平均值为(11.98±1.77)‰。胶州湾食物网中的主要生物种类可以划分为4个营养组群,即初级生产者、初级消费者、次级消费者以及顶级捕食者。δ15N值分析显示,胶州湾主要生物种类的营养级范围是1.10—4.03。与文献中基于胃含物分析计算的营养级相比较,37个种类中有29种的营养级分析结果基本一致(在0.5个营养级的误差范围之内)。因此,氮稳定同位素法是一种研究水生生态系统食物网营养位置的有效方法。其中,有8种鱼类的营养级与历史文献相比有所下降,分析方法的不同可能是原因之一,此外,这些鱼种摄食饵料生物营养级的下降也是导致其营养级降低的另一个主要原因。根据营养级计算的结果,构建了胶州湾食物网的连续营养谱,胶州湾食物网中,绝大多数生物种类都属于初级和中级肉食性种类。     

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。     

枸杞岛近岸海域食物网的稳定同位素分析

为了探明岛礁近岸海域食物网主要生物类群之间的营养关系,对2012年11月和2013年2月枸杞岛近岸的消费者及其潜在食物源的稳定碳、氮同位素组成进行了分析,并利用氮稳定同位素数据计算了消费者的营养级。结果表明:枸杞岛近岸海域消费者潜在食源浮游植物、POM、SOM和大型海藻的δ13C值范围为-21.7‰~-14.7‰,浮游动物、大型无脊椎动物和鱼类等消费者的δ13C值范围为-21.1‰~-13.7‰。初级生产者的C/N平均值为8.5,消费者的C/N平均值3.7,差异极显著(P0.001)。根据消费者的δ15N值,可将枸杞岛近岸海域的消费者分为滤食性浮游动物、食藻或碎屑的小型底栖动物、杂食性的大型无脊椎动物和鱼类以及凶猛的肉食性鱼类4大类,消费者共有4个营养等级,黑鲷的营养级最高为4.33。     

山东东营和烟台潮间带海草床食物网结构特征

为了探明海草床内主要生物类群间的营养关系以及食物网结构, 作者于2018年8月分别在东营黄河口潮间带和烟台西海岸潮间带海草床采集大型底栖生物样品, 采用δ ¹³C和δ ¹⁵N稳定同位素方法, 对生物样品的碳、氮同位素组成进行了测定和分析。结果表明: 东营海草床内生物的δ ¹³C、δ ¹⁵N值范围分别为-21.99‰至-12.13‰和5.23‰-11.05‰, 烟台海草床内生物的δ ¹³C、δ ¹⁵N值范围分别为-18.11‰至-14.06‰和6.60‰-10.22‰。东营海草床主要生物的营养级范围为2.00-3.85, 烟台海草床主要生物的营养级范围为2.00-3.15。根据δ ¹⁵N值计算所得的营养级图分析可知两区域海草床内初级消费者主要为滤食性双壳类和多毛类, 次级消费者为植食性或杂食性甲壳类,肉食性鱼类和腹足类。与近海海域大型底栖生物食物网相比, 海草床内底栖生物的营养级均值普遍较低。     

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.     

冶金区节肢动物碳、氮稳定同位素组成及营养级关系

通过测定辽宁省葫芦岛锌厂不同生境植物和主要消费者的碳、氮稳定同位素比值,研究冶金区不同消费者碳、氮稳定同位素组成及不同消费者之间的关系.结果表明:节肢动物δ13C、δ15N值的变化范围分别为-12.61‰～-29.63‰、1.73‰～9.94‰,变化幅度较大.研究区植物以C3植物居多,导致不同群落生境动物δ13C值较低;螳螂、蜘蛛δ15N比值高于其他动物;通过营养级模型计算可知不同消费者之间的关系,蝗虫、蚱蜢等草食性动物形成第二营养级,即初级消费者;第三营养级包括蜘蛛、螳螂,为次级消费者.     

夏季若尔盖高寒湿地水生生物群落食物网结构特征

为了解若尔盖高寒湿地夏季水生生物群落食物网结构及营养关系特征,应用稳定同位素技术分析了若尔盖湿地 3个不同区域(ZS1、ZS2和ZS3)水生生物群落碳、氮稳定同位素比值,并计算了13C-15N同位素生态位中的6个营养结构量化指标。结果显示:外源性营养源陆生植物13C、15N值分别为-28.23- -26.07,-1.20-5.98; 内源性营养源颗粒有机物 (POM:主要成分为藻类)和水生植物13C、15N值分别为-26.39- -21.17、-25.37- -24.15,3.68-6.61、3.50-4.01; 其中POM样品13C、15N组成存在明显的区域性差异(P0.05,P0.001)。食物网营养结构分析显示若尔盖湿地外源性碳源输入(优势陆生植物)对于维持该水域生态系统结构稳定有着十分重要的作用。若尔盖湿地水域食物网营养级介于2-3,暗示了其生态系统结构的相对脆弱性。同位素量化指标标记发现若尔盖湿地水生动物群落生态结构存在明显的空间异质性,可能与若尔盖湿地发达的畜牧产业相关。     

应用稳定同位素研究广西东方洞食物网结构和营养级关系

稳定性同位素技术已经成为研究生态系统食物网结构和营养级关系及其动态变化的重要手段。应用稳定同位素技术(δ13C和δ15N)研究了东风洞的食物网结构和营养级关系。研究结果表明,东风洞主要为腐食食物链,由于在洞穴内黑暗带中无光照也无植物生长,所以碳源主要为东风洞中的土壤有机质,作为第一营养级;主要摄食关系为马陆与土壤有机物质,螺类与土壤有机物质等;在该洞生态系统中,将3种马陆直接作为初级消费者,以隅蛛和其它马陆平均值之间的差值(2.04‰)作为东风洞食物网稳定氮同位素的富集因子。根据营养级模型可知,马陆类群、细长钻螺等土壤动物,裸灶螽和涂闪夜蛾形成第二营养级,即初级消费者;第三营养级包括蜘蛛类、盲蛛、地蜈蚣以及黑眶蟾蜍,为次级消费者。     

克氏原螯虾两种养殖模式的食物网结构及其食性比较

为比较克氏原螯虾(Procambarus clarkii)精养模式和稻虾共作模式下的食物网结构及其食性差异, 对两种养殖模式的基础食源与消费者的δ13C和δ15N进行了分析, 并借助SIBER考察了各自的食物网结构, 定量计算不同饵料对克氏原螯虾食物的贡献率。结果显示: 在采集的19种样品中, 消费者的δ13C值介于–34.22‰—–25.34‰, δ15N值介于2.33‰—8.05‰, 营养级介于1.46—3.64; 在精养模式下克氏原螯虾的营养级(2.34)高于共作模式(1.79)。食物网结构参数对比表明, 两种模式下克氏原螯虾的生态空间利用率接近, 但共作模式的食物网营养结构多样性较高, 群落的营养生态位范围较宽, 食物网的营养冗余程度较低, 不同物种竞争激烈程度较低; 食性分析显示, 在两种模式下克氏原螯虾的δ15N值与其体长、体重具有线性正相关关系, 说明克氏原螯虾营养级随着其体型增大而提高, 另外克氏原螯虾在两种养殖模式中均偏向于摄食动物性饵料, 共作模式中克氏原螯虾饵料来源分布较精养模式更均匀, 其植物性饵料贡献率较精养模式更高。研究表明: 精养模式的物质能量从基础食源传至克氏原螯虾的传递损耗较共作模式要高; 与精养模式相比, 稻虾共作模式中克氏原螯虾更偏向植食性。     

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。     

Tracing energy flow in stream food webs using stable isotopes of hydrogen

1. Use of the natural ratios of carbon and nitrogen stable isotopes as tracers of trophic interactions has some clear advantages over alternative methods for food web analyses, yet is limited to situations where organic materials of interest have adequate isotopic separation between potential sources. This constrains the use of natural abundance stable isotope approaches to a subset of ecosystems with biogeochemical conditions favourable to source separation. 2. Recent studies suggest that stable hydrogen isotopes (δD) could provide a robust tracer to distinguish contributions of aquatic and terrestrial production in food webs, but variation in δD of consumers and their organic food sources are poorly known. To explore the utility of the stable hydrogen isotope approach, we examined variation in δD in stream food webs in a forested catchment where variation in δ¹³C has been described previously. 3. Although algal δD varied by taxa and, to a small degree, between sites, we found consistent and clear separation (by an average of 67‰) from terrestrial carbon sources. Environmental conditions known to affect algal δ¹³C, such as water velocity and stream productivity did not greatly influence algal δD, and there was no evidence of seasonal variation. In contrast, algal δ¹³C was strongly affected by environmental factors both within and across sites, was seasonally variable at all sites, and partially overlapped with terrestrial δ¹³C in all streams with catchment areas larger than 10 km². 4. While knowledge of isotopic exchange with water and trophic fractionation of δD for aquatic consumers is limited, consistent source separation in streams suggests that δD may provide a complementary food web tracer to δ¹³C in aquatic food webs. Lack of significant seasonal or spatial variation in δD is a distinct advantage over δ¹³C for applications in many aquatic ecosystems.     

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.     

Macroinvertebrate food web structure in a floodplain lake of the Bolivian Amazon

Two stable isotopes δ¹³C and δ¹⁵N were used to identify the energy sources and trophic relationships of the main freshwater macroinvertebrates in a floodplain lake of the Beni River (Bolivian Amazonia). Four energy sources (seston, bottom sediment, periphyton, and aquatic macrophytes) and macroinvertebrate communities were collected during three periods of the river hydrological cycle. Macroinvertebrates showed greater temporal variation in isotope values than their food sources. Six trophic chains were identified: four were based on seston, periphyton, C₃ macrophytes, and bottom sediments, and the last two chains on a combination of two carbon sources. One mixed seston and periphyton sources during the wet season while the other mixed periphyton and macrophytes sources during the wet and dry seasons. Periphyton was the most important energy source supporting the highest number of trophic levels and consumers. The macrophytic contribution was only significant during the dry season. Bottom sediments constituted a marginal energy source. As each season is associated with different physical and chemical conditions, processes organizing macroinvertebrate food web structure in the Beni floodplain seem strongly linked to hydrological seasonality.     

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.     

The loss of aquatic and riparian plant communities: Implications for their consumers in a riverine food web

Abstract Human induced alterations to rivers and steams have resulted in significant changes to the structure and diversity of riparian and aquatic plant communities. These changes will impact on the dynamics of riverine carbon cycles and food web structure and function. Here we investigate the principal sources of organic carbon supporting local shredder communities across a gradient in different levels of anthropogenic development along riverine reaches, in South Australia. In forested/wooded reaches with minimum to limited development, semi‐emergent macrophytes were the principal sources of organic carbon supporting the local shredder communities. However, in developed reaches, course particulate organic matter and filamentous algae were the principal food sources. The C:N ratios of the food sources in developed reaches were higher than those of their consumers indicating a stoichiometric mismatch. This imbalanced consumer‐resource nutrient ratio in those developed reaches is likely to impose constraints on the growth and reproduction of their aquatic shredder communities with probable knock‐on effects to higher trophic levels.     

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。     

Research article: small-scale spatial variation of δ13C and δ15N isotopes in Antarctic carbon sources and consumers

Regional food web studies that fail to account for small-scale isotopic variability can lead to a mismatch between an organism’s inferred and true trophic position. Misinterpretation of trophic status may result, substantially limiting spatial and temporal comparability of food web studies. We sampled several carbon sources and consumers in a nested design to assess the variability of food web members across small spatial scales (100 s of m to several km) in regions around the Windmill Islands and Vestfold Hills in East Antarctica. For carbon sources, δ¹³C in sea ice POM was particularly variable between locations (km apart) and between sites (100 s of m apart) with replicate samples varying by up to 16‰. Macroalgae δ¹³C was less variable (replicate samples ranging up to 6.9‰ for the red alga Iridaea cordata), yet still differed between locations. Sediment POM and pelagic POM were the least variable, displaying minimal differences between locations or sites for δ¹³C and δ¹⁵N. Three out of eight consumers were significantly different between locations for δ¹³C, and five out of eight for δ¹⁵N, with the fish Trematomus bernacchii the most variable for both δ¹³C and δ¹⁵N. At smaller scales, the amphipod Paramorea walkeri showed significant variation between sites in δ¹³C but not in δ¹⁵N. We attribute small-scale variability to the dynamic physical environment for carbon sources in coastal systems and a close coupling of diet to habitat for consumers. We highlight the need to account for small-scale spatial variation in sampling designs for regional food web studies.