Stable isotope analysis of macroinvertebrates and their food sources in a glacier stream

1. Food sources and trophic structure of the macroinvertebrate community along a longitudinal gradient were examined in a glacier stream of the Swiss Alps (Val Roseg). Analysis of multiple stable isotopes (δ¹³C and δ¹⁵N) and measurement of C : N ratios were used to differentiate between allochthonous and autochthonous organic matter.
2. Although isotopic signatures of algae varied widely among sites and dates, it was possible to discriminate between allochthonous and autochthonous food sources using a site-specific approach.
3. Dominant food sources of herbivorous invertebrates in all main channel sites were epilithic diatoms and the filamentous gold alga Hydrurus foetidus . Allochthonous organic matter was of some importance only in a groundwater-fed stream close to the floodplain margin.
4. Seasonal changes in the δ¹³C signature of the macroinvertebrates corresponded with seasonal changes in δ¹³C of the gold alga H. foetidus . This indicated that the energy base remains autochthonous throughout the year.
5. Because of limited food sources, feeding plasticity of the invertebrate community was high. Both grazers and shredders fed predominantly on algae, whereas gatherer-collectors seemed to be omnivorous.
6. The overall enrichment of δ¹⁵N was 2.25‰ ( r ²=0.99) per trophic level. On a gradient from the glacier site to a downstream forested site trophic enrichment was constant but variation in δ¹⁵N within trophic levels decreased.     

玉龙雪山白水1号冰川退缩迹地的植被演替

运用空间代替时间,野外调查和因子分析的方法,研究了自小冰期最盛时以来的玉龙雪山白水1号冰川裸地的植被演替各个阶段的植物群落组成及其数量特征,演替过程中植被类型的变化及其解释,小冰期冰碛垄年龄的估测这3个主要内容.累计调查的55个样方中共出现91种植物,已鉴定出63个种,分属于28个科,46个属,双子叶植物居多,包括乔木、灌木和草本3种生活型的植物.通过统计分析各个演替阶段植物群落的数量特征,揭示出各个阶段植物群落的组成及其替代规律,即:在白水1号冰川末端近250a的退缩迹地上经历了裸地-草本-灌木-乔木的发展阶段.从生态位理论方面来看,这是由于不同物种的生态位及适应性都是不同的,所以构成了不同演替阶段的各自迥异的植物群落,优势种往往是那些生态位比较宽、适应性较强,能在多个演替阶段出现的物种.演替就是朝着生态位不断分化,能够最大限度利用资源的方向发展,其中物种的替代过程实质上就是在生态位不断的分化与接近,激烈的种内与种间竞争的过程中进行着的.基于此通过综合分析海螺沟与玉龙雪山的地理区位特征,气候状况,植被演替过程以及玉龙雪山地区相关的树轮方面的资料,来尝试着估测白水1号冰川小冰期终碛垄的年龄大约在170-250a之间.     

贡嘎山冰川退缩区植物-土壤反馈与植物间相互作用

植物-土壤反馈是揭示陆地生物群落动态变化的关键环节,为理解植物间相互作用及植被群落变化过程奠定基础。本研究以贡嘎山冰川退缩区原生演替早(5~10年)、中(30~40年)和晚期(80~100年)3个阶段典型土壤以及各阶段优势植物为对象,采用盆栽控制试验,比较优势植物在不同土壤条件下的生物量,并量化植物间相互作用以及植物-土壤反馈的方向与强度,为探究贡嘎山冰川退缩区植被群落演替规律提供依据。结果表明:(1)植物-土壤反馈作用显著影响植物在本土中的生物量,早期沙棘(Hippophae rhamnoides)在本土中生长最差,沙棘的植物-土壤反馈系数为负值;演替中期冬瓜杨(Populus purdomii)的反馈系数趋于零;晚期峨眉冷杉(Abies fabri)在本土中生长最好,峨眉冷杉的反馈系数为正值。(2)混种时,早期沙棘与演替中、晚期植物间相互作用指数为负值;中期冬瓜杨、川滇柳(Salix rehderiana)与演替早、晚期植物的相互作用指数接近于零,晚期植物峨眉冷杉、麦吊云杉(Picea brachytyla)与演替早、中期植物相互作用指数为正值。从植物-土壤反馈的方向来看,贡嘎山植被演替从早期负反馈,中期中性反馈,过渡到晚期正反馈。此外,演替早期沙棘促进演替中晚期植物生长,演替中期冬瓜杨、川滇柳对演替早晚期植物无显著影响,晚期峨眉冷杉、麦吊云杉更利于与演替早中期植物相互竞争。结果显示,植物-土壤反馈与植物间相互作用共同驱动了贡嘎山冰川退缩区植被快速演替,直至顶极群落。     

Glaciella,a new genus of freshwater Canthocamptidae (Copepoda,Harpacticoida) from a glacier in Nepal,Himalayas

A new genus and new species of Canthocamptidae: Glaciella yalensis (Copepoda: Harpacticoida) from the surface of Yale Glacier, Nepal is described. This new species was collected from cryconite-pit on the surface of the glacier and is closely related to genus Maraenobiotus, but easily distinguishable from its species in the following: 1) segments and setae on endopodites of legs 2–4 in the male differing shape, 2) exopodites of male legs 3–4 with modified setae, 3) caudal seta in female absent. Body color of this copepod is red in live specimens.Contributions No. 86 Itako Hydrobiological Station, Ibaraki University.     

Purification and Properties of Cold-active Metalloprotease from Curtobacterium luteum and Effect of Culture Conditions on Production

Curtobacterium luteum, a gram-positive psychrotrophic bacterium, secreting an extracellular protease was isolated from the soil of Gangotri glacier, Western Himalaya. The maximum enzyme production was achieved when isolate was grown in a pH-neutral medium containing skim milk at 15oC over 120 hour. The metal ions such as Zn2+ and Cr2+ enhanced enzyme production. The specific activity of purified enzyme was 8090 u/mg after 34.1 fold purification. The 115 kD enzyme was a metalloprotease (activity inhibited by EDTA and EGTA) and showed maximum activity at 20oC and pH 7. The enzyme was active over a broad pH range and retained 84% of its original activity between pH 6–8. There was no loss in enzyme activity when exposed for 3 hours at 4oC-20oC. However, lost 65% of activity at 30oC, and was almost inactivated at 50oC, but was resistant to repeated freezing and thawing. The enzyme activity was stimulated by manganese ions; however, it was inactivated by copper ions.     

Potential feedback mediated by soil microbiome response to warming in a glacier forefield

Mountain glaciers are retreating at an unprecedented rate due to global warming. Glacier retreat is widely believed to be driven by the physiochemical characteristics of glacier surfaces; however, the current knowledge of such biological drivers remains limited. An estimated 130 Tg of organic carbon (OC) is stored in mountain glaciers globally. As a result of global warming, the accelerated microbial decomposition of OC may further accelerate the melting process of mountain glaciers by heat production with the release of greenhouse gases, such as carbon dioxide (CO₂) and methane. Here, using short‐term aerobic incubation data from the forefield of Urumqi Glacier No. 1, we assessed the potential climate feedback mediated by soil microbiomes at temperatures of 5°C (control), 6.2°C (RCP 2.6), 11°C (RCP 8.5), and 15°C (extreme temperature). We observed enhanced CO₂‐C release and heat production under warming conditions, which led to an increase in near‐surface (2 m) atmospheric temperatures, ranging from 0.9°C to 3.4°C. Warming significantly changed the structures of the RNA‐derived (active) and DNA‐derived (total) soil microbiomes, and active microbes were more sensitive to increased temperatures than total microbes. Considering the positive effects of temperature and deglaciation age on the CO₂‐C release rate, the alterations in the active microbial community structure had a negative impact on the increased CO₂‐C release rate. Our results revealed that glacial melting could potentially be significantly accelerated by heat production from increased microbial decomposition of OC. This risk might be true for other high‐altitude glaciers under emerging warming, thus improving the predictions of the effects of potential feedback on global warming.     

Tracing biogeochemical subsidies from glacier runoff into Alaska's coastal marine food webs

Nearly half of the freshwater discharge into the Gulf of Alaska originates from landscapes draining glacier runoff, but the influence of the influx of riverine organic matter on the trophodynamics of coastal marine food webs is not well understood. We quantified the ecological impact of riverine organic matter subsidies to glacier‐marine habitats by developing a multi‐trophic level Bayesian three‐isotope mixing model. We utilized large gradients in stable (δ¹³C, δ¹⁵N, δ²H) and radiogenic (Δ¹⁴C) isotopes that trace riverine and marine organic matter sources as they are passed from lower to higher trophic levels in glacial‐marine habitats. We also compared isotope ratios between glacial‐marine and more oceanic habitats. Based on isotopic measurements of potential baseline sources, ambient water and tissues of marine consumers, estimates of the riverine organic matter source contribution to upper trophic‐level species including fish and seabirds ranged from 12% to 44%. Variability in resource use among similar taxa corresponded to variation in species distribution and life histories. For example, riverine organic matter assimilation by the glacier‐nesting seabirds Kittlitz's murrelet (Brachyramphus brevirostris) was greater than that of the forest‐nesting marbled murrelet (B. marmoratus). The particulate and dissolved organic carbon in glacial runoff and near surface coastal waters was aged (12100–1500 years BP ¹⁴C‐age) but dissolved inorganic carbon and biota in coastal waters were young (530 years BP ¹⁴C‐age to modern). Thus terrestrial‐derived subsidies in marine food webs were primarily composed of young organic matter sources released from glacier ecosystems and their surrounding watersheds. Stable isotope compositions also revealed a divergence in food web structure between glacial‐marine and oceanic sites. This work demonstrates linkages between terrestrial and marine ecosystems, and facilitates a greater understanding of how climate‐driven changes in freshwater runoff have the potential to alter food web dynamics within coastal marine ecosystems in Alaska.     

Variation in Microbial Community Composition and Culturability in the Rhizosphere of Leucanthemopsis alpina (L.) Heywood and Adjacent Bare Soil Along an Alpine Chronosequence

We compared the size, culturability, diversity, and dominant species similarity of the bacterial communities of Leucanthemopsis alpina (L.) Heywood rhizosphere and adjacent bare soil (interspace) along a chronosequence of soil development time (5, 50, and 70 years) in the forefield of the Dammaglacier (Switzerland). We found no evidence that the size of the bacterial community was significantly affected by either soil age or the presence of L. alpina. In contrast, the proportion of the bacterial community that could be cultured on nonselective agars, and which was taken as an indication of the proportion of r-selected populations, was significantly higher in the 50- and 70-year-old soils than in the 5-year-old soil, and was also significantly higher in the rhizosphere of L. alpina at all time points. RDA indicated significant correlations between the increased culturability of the bacterial community over time and increasing concentrations of labile N, and between the increased culturability in the rhizosphere and increased concentrations of labile C and N. HaeIII-amplified ribosomal DNA (rDNA) restriction analysis of a library of 120 clones of 16S rDNA revealed 85 distinct phylotypes. Hurlbert's probability of interspecific encounter (PIE) values derived from this library ranged from 0.95 to 1.0, indicating a very high genetic diversity. There was no significant difference in the PIE values of rhizosphere and interspace communities. Detrended correspondence analysis (DCA) of 16S ribosomal RNA (rRNA) denaturing gradient gel electrophoresis (DGGE) community profiles clearly distinguished the rhizosphere from the interspace community in the 5-year-old soils and also clearly distinguished between these communities and the rhizosphere and interspace communities of the 50- and 70-year-old soils. However, 16S rRNA DGGE revealed little difference between rhizosphere and interspace communities in the 50- and 70-year-old soils. The relative similarity of the 16S rRNA profiles strongly reflected labile carbon and nitrogen availability. Overall, our results suggest that improved C and N availability in the rhizosphere of L. alpina increases the size of r-selected bacterial species populations, but that the influence of L. alpina depends on soil age, being maximal in the youngest soils and minimal in the oldest. The reduced influence of L. alpina in the older soils may reflect a feedback between improved nutrient availability and reduced rhizodeposition.     

1967-2014年科西河流域冰湖时空变化

冰湖是高山寒区气候变化的灵敏指示器和诱发山地溃决洪水或泥石流的灾害源。基于1960s-2010s多源遥感影像数据（Corona、Landsat MSS/TM/ETM+OLI）、地形图、冰川编目和气象数据,利用RS和GIS技术综合分析科西河流域近50年冰湖（≥ 0.05 km²）时空变化特征及其对冰川变化影响。研究结果表明：（1）近50年来科西河流域冰湖整体经历了"先平稳后扩张"的过程,其中1960s至1980s初期,科西河流域有37个冰湖消失,但总面积趋于平稳状态;1980s中期至2010s初期,流域内冰湖规模迅速扩张,且2000s之后冰湖扩张速率明显加快,至2010s初期增加为321个冰湖（88.43 km²）。（2）科西河流域冰湖集中分布于海拔5000-5500 m,面积小于0.25 km²的小规模冰湖占总数量的74.45%,而面积大于1 km²和介于0.05-0.25 km²的冰湖占总面积的64.18%。（3）除利库科拉（Likhu Khola）流域外,科西河流域其他5个子流域冰湖均呈扩张趋势,其中尤以阿润（Arun）流域冰湖扩张最为显著。（4）气候变暖及其引发的冰川退缩是科西河流域冰湖扩张的根本原因,当冰川末端伸入冰湖时,冰水物质与能量交换在一定程度上加速了冰川消融与退缩。     

冰川消退带微生物群落演替及生物地球化学循环

冰川是生物圈重要组分之一。由于全球气候变化世界多地冰川加速消融,暴露原本被冰盖覆盖的区域,这些区域被称为冰川消退区域(glacier retreat area)或冰川前部区域(glacier foreland)。自暴露开始消退区随即发生初生演替,随着演替进行,物质循环逐步建立,生物量和土壤C、N总量逐步增加。生态系统C、N输入最初以矿化外来物为主,逐渐转变为以生物固C、固N为主。演替早期生态系统的发育主要受土壤C、N含量的限制,而演替后期的限制性营养物转变为P。演替区域土壤逐渐发育并促进生态位的分化,细菌、真菌、古菌,病毒及其他微生物群落的生物量和多样性不断增加直至达到该地区可承受的极值。随着生存条件的改善,不同生态策略物种的更替导致每个演替阶段微生物群落结构的差异。整体上,伴随演替进行微生物群落丰度、结构和活性呈现梯度性变化。气候变化对冰川消退带生态演替结果产生多方面的影响,而这些影响结果又综合反馈气候变化,因此目前难以准确估计气候变化对消退带生态演替的净效应。综述了近年冰川消退带微生物群落演替方面相关的研究结果,同时分别对该区域物质循环的建立、微生物群落演替和气候变化造成的影响这三个方面进行详细描述,并指出当前研究的不足。