Feeding ecology of granivorous carabid larvae: a stable isotope analysis

Although most carabids are primarily carnivorous, some carabid species are omnivorous, with mainly granivorous feeding habits during the larval and/or adult stages (granivorous carabids). This feeding habit has been established based on laboratory and field experiments; however, our knowledge of the feeding ecology of these beetles in the field is limited owing to the lack of an appropriate methodology. In this study, we tested the utility of stable isotope analysis in investigations of the feeding ecology of granivorous carabids in the field, using two closely related syntopic species, Amara chalcites and Amara congrua. We addressed two issues concerning the feeding ecology of granivorous carabids: food niche differentiation between related syntopic species during the larval stage and the effect on adult body size of supplementing seeds with an animal diet during the larval stage. To investigate larval feeding habits, we analysed newly emerged adults, most somatic tissues of which are considered of larval origin. In the two populations examined, both δ¹⁵N and δ¹³C were significantly higher in A. chalcites than A. congrua, suggesting that the two species differentiate food niches, with A. chalcites larvae being more carnivorous than A. congrua larvae. The two isotope ratios of A. chalcites samples from one locality were positively correlated with body size, suggesting that more carnivorous larvae become larger adults. However, this relationship was not detected in other species/locality groups. Thus, our results were inconclusive on the issue of diet supplementation. Nevertheless, overall, these results are comparable with those of previous laboratory‐rearing experiments and demonstrate the potential utility of stable isotope analysis in field studies on the feeding ecology of granivorous carabids.     

Diet diversity among five co-existing fish species in a tropical river: integration of dietary and stable isotope data

Diets were estimated from stomach contents and the MixSIR model using stable isotope values for five co-existing and abundant benthic fishes in relation to potential prey from a riffle habitat in a tropical river in eastern Thailand. Collectively, aquatic insects were of greatest dietary importance based on stomach contents and, except for one fish species, predicted from the MixSIR. The most prominent functional feeding insect groups in fish diets were collector-filterers and scrapers and, to a lesser extent, predators. MixSIR predicted shrimp to be the most important single dietary constituent for all fishes in contrast to stomach contents, which indicated they are a major item for only one species. MixSIR predicted plant material to be more important in fish diets than stomach contents where the composition of detritus was a concern. Differences in temporal feeding schedules, prey availability, species adaptations and others are important in understanding diet and in the construction of food webs. Stable isotope and dietary analysis provides a more accurate assessment of the food web structure and dynamics of tropical river ecosystems than either method alone.     

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.     

Trophic redundancy among fishes in an East African nearshore seagrass community inferred from stable‐isotope analysis

Stable‐isotope analysis supplemented with stomach contents data from published sources was used to quantify the trophic niches, trophic niche overlaps and potential trophic redundancy for the most commonly caught fish species from an East African nearshore seagrass community. This assessment is an important first step in quantifying food‐web structure in a region subject to intense fishing activities. Nearshore food webs were driven by at least two isotopically distinct trophic pathways, algal and seagrass, with a greater proportion of the sampled species feeding within the seagrass food web (57%) compared with the algal food web (33%). There was considerable isotopic niche overlap among species (92% of species overlapped with at least one other species). Narrow isotopic niche widths of most (83%) species sampled, low isotopic similarity (only 23% of species exhibited no differences in δ¹³C and δ¹⁵N) and low predicted trophic redundancy among fishes most commonly caught by fishermen (15%), however, suggest that adjustments to resource management concerning harvesting and gear selectivity may be needed for the persistence of artisanal fishing in northern Tanzania. More detailed trophic studies paired with information on spatio‐temporal variation in fish abundance, especially for heavily targeted species, will assist in the development and implementation of management strategies to maintain coastal food‐web integrity.     

Trophic interactions among invertebrates in termitaria in the African savanna: a stable isotope approach

Abstract 1. Termites (Isoptera) in tropical savannas are known as ecosystem engineers, affecting the spatial and temporal distribution of water, carbon, cations, and nutrients through their mound structures. Their mounds, however, also offer habitation to diverse taxa and feeding guilds of other invertebrates; a keystone role that has not been properly quantified. 2. The aim of this study was to explore the ecosystem role of termitaria in determining invertebrate diversity and their potential trophic interactions. We used stable isotopes to distinguish termite‐feeding invertebrates from invertebrates merely living in termite mounds under field conditions. 3. The results suggest that inquiline spiders (Arachnida) do not feed on termites directly, but on other invertebrates within the termitaria that are termitophagous, elevating the spiders three trophic levels higher than the termites. 4. This study is the first to demonstrate food web interactions among inquiline invertebrates with a stable isotope approach. It provides evidence that termites play a keystone role in the system by providing habitat for various, trophically interacting invertebrates. These results illustrate a rather unexplored ecosystem property of savanna termites.     

Flight capabilities and feeding habits of silphine beetles: are flightless species really “carrion beetles”?

We determined the flight capabilities and feeding habits of adults of nine silphine beetle species and illustrated their relationship. We examined the silphine beetles for the presence or absence of flight muscles and estimated their feeding habits by comparing the carbon and nitrogen stable isotope ratios for them with those of necrophagous nicrophorine species and carnivorous carabine species. Three species (Silpha longicornis, S. perforata and Phosphuga atrata) completely lacked individuals with flight muscles, and one species (Eusilpha japonica) showed flight muscle dimorphism. Stable isotope analysis suggested that these species were carnivores, mainly feeding on soil invertebrates. Most flight species showed higher isotopic ratios than the flightless species. Some of them have isotopic ratios close to those of the nicrophorine species, suggesting that these species mainly feed on vertebrate carcasses. Flightless silphine species would have limited ability to search for patchy and unpredictable carcass resources. Further studies are necessary to understand the adaptive evolution of flight capability and the feeding habits in this group.     

Effects of diet on female fecundity and larval development in the carrion beetle Necrophila japonica

The carrion beetle subfamily Silphinae (Coleoptera: Silphidae) contains dominant macroinvertebrates of soil ecosystems in temperate zones. However, their feeding habits, which determine the role of each species in the ecosystem, have not been sufficiently studied. Moreover, although a diet shift from necrophagy on vertebrate carcasses to predatory feeding on invertebrates is known to occur in this subfamily, the processes and mechanisms of this shift have also been inadequately addressed. We examined female fecundity and larval development on various diets in a Silphinae species, Necrophila (Eusilpha) japonica (Motschulsky). The experimental diets included a meat diet and various invertebrate diets, which reflect the ‘ancestral’ feeding habit in Silphinae, necrophagy, and the ‘derivative’ feeding habit, predatory feeding. Female fecundity was significantly higher on the meat diet (minced beef) than on an insect larvae diet (mealworms and dipteran larvae) but did not significantly differ from that on an earthworm diet. Larval developmental performance was significantly higher on the earthworm diet than on the meat and insect larvae diets. Our results for larval development were consistent with those of previous stable isotope analyses of the same species, in which isotopic values of larval samples agree with those of hypothetical consumers that utilize earthworms. The consistency of results among different methods indicates that N. japonica larvae are most likely earthworm feeders. In contrast, our results for the female fecundity experiment differed from those of previous stable isotope analyses, in which vertebrate carcasses unlikely serve as the staple diet of adults in the field; thus, the feeding habits of N. japonica adults remain unresolved. Our observations that females and larvae performed best on the meat and earthworm diets, respectively, may indicate that, in Silphinae, the diet shift from necrophagy to predatory habits occurs earlier in larvae than in adults.     

Long-term trends in food habits of Asiatic black bears in the Misaka Mountains on the Pacific coast of central Japan

I did the food habits of the Asiatic black bear Ursus thibetanus from 1013 fecal samples collected between 1999 and 2005 in the Misaka Mountains on the Pacific coast of central Japan. The food habits of the bears showed clear seasonal changes, and I classified the food resources of the bears into three types. Staple foods were green vegetation in spring, soft mast (Prunus spp.) and insects in summer, and hard mast (Quercus spp.) in autumn. Alternative foods were green vegetation and other soft mast (Rubus spp.) in summer and Japanese chestnuts Castanea crenata and vine fruits in autumn. Foods of opportunity were hard mast (Quercus spp.) that had been shed in the previous autumn and were found in spring and other fruits in autumn. Seasonal food habits showed yearly variations: bears used alternative foods and foods of opportunity in response to the yearly variation in staple food amount, but the magnitude of variability of food habits differed among seasons, with large variability in autumn and small variability in summer and spring. The primary influence on the yearly variation in food habit is presumably the fluctuation in fruit production among years. Summer is probably the most difficult season in terms of the bear's food supply, because the number of fruiting species is limited and staple foods such as new green vegetation and fruits are less available. Long-term studies of the availability of the main food items and food habits of bears will be critical for further understanding these animals’ feeding ecology and for determining the factors that influence their behavior.     

Differences in food assimilation between two coot species assessed with stable isotopes and particle size in faeces: linking physiology and conservation

The red-knobbed coot Fulica cristata experienced a dramatic population decline in Spain, where the common coot F. atra does not face conservation problems. This is puzzling because both species have similar ecologies. It has been suggested that habitat alterations affected the quality of food plants, and this impacted differentially both coots. To verify this, we conducted experiments to determine the assimilation efficiency of both species in relation to food quality. Two types of diets differing in fibre content (commercial food and Potamogeton pectinatus) were offered to captive red-knobbed and common coots, during both spring and autumn. We examined variations in faecal particle size among coot species and diets, indicative of the facility with which food can be assimilated, and used the stable isotope technique to study differences between coot species in stable isotope fractionations from consumption to excretion. Faecal particle size was larger in red-knobbed than in common coots when fibre content was high, but was similar when it was low. Faecal particle sizes were larger in autumn, when fibre content was higher, than in spring. In general, delta(15)N in faeces of red-knobbed coots was greater than in faeces of common coots. These results suggest that the digestive efficiency of the red-knobbed coot was lower than that of the common coot, and that the differences increased when the fibre content in food plants increased. Managers should try to make available to coots wetland habitat with high quality food, which may be facilitated by prolonging the hydroperiods.     

基于稳定氧同位素确定植物水分来源不同方法的比较

利用稳定同位素技术确定植物水分来源,对提高生态水文过程的认识和对干旱半干旱区的生态管理至关重要。目前基于稳定同位素技术确定植物水分来源的方法众多,但不同方法之间对比的研究较少。本研究基于原位样品采集,室内实验测试,利用直接对比法、多元线性混合模型(IsoSource)、贝叶斯混合模型(MixSIR、MixSIAR)和吸水深度模型分析植物水分来源,并对比各方法的优缺点。结果表明:相对于多元线性混合模型(IsoSource)而言,贝叶斯混合模型(MixSIR、MixSIAR)具有更好的水源区分性能,但对数据要求较高,且植物木质部水和潜在水源同位素组成的标准差越小,模型运行结果的可信度更高。本研究中贝叶斯混合模型(MixSIR)为最优解。在利用稳定氢氧同位素技术确定植物水分来源时,可先通过直接对比法定性判断植物可能利用的潜在水源,然后再用多元线性混合模型(IsoSource)、贝叶斯混合模型(MixSIR、MixSIAR)计算出各潜在水源对植物的贡献率和贡献范围,必要时可评估模型性能,选择出最优模型,定量分析植物的水分来源。若植物主要吸收利用不同土层深度的土壤水,可结合吸水深度模型计算出植物吸收土壤水的平均深度。本研究为干旱半干旱地区利用同位素技术确定植物水分来源方法的选择提供了理论依据。     

洞庭湖区东方田鼠的食物组成调查

采用胃内容物显微组织学鉴定法,定量调查了洞庭湖区东方田鼠（Ｍｉｃｒｏｔｕｓｆｏｒｔｉｓｃａｌａｍｏ－ｒｕｍ）的食物组成。该鼠的主要食物,在苔草地是苔草和水田碎米荠,在芦荻场是碎米荠、苦草、荻和镜子苔,在稻田区是水稻和双穗雀稗,在岗地是三毛草、一年蓬、千金子和水稻。植物叶片是其主要利用对象,在绿色食物资源不足的情况下,也取食植物种子。其食物组成的变化表明,该鼠能依不同栖息地的植被结构调整摄食对象,因而能适应湖区生活环境的灾变性变化。     

BIODIVERSITY RESEARCH: Diversity and distribution of macroinvertebrates in lentic habitats in massively altered landscapes in south‐eastern Australia

Aim We investigated whether faunas of lentic macroinvertebrates differed among two landscape types: (1) those that are largely covered in forests (presumed to be in a more pre‐human‐impact condition) and (2) those that are completely cleared for agricultural exploitation (massively altered). Location Five pairs of landscapes (each pair referred to as a region) – one of each landscape type – across a 30,000 km² region of north‐central Victoria, Australia. Methods Each individual waterbody was surveyed three times (austral spring 2006, autumn 2007, and spring 2007) for invertebrates. Waterbodies were characterized by measurements of static (e.g. abutting vegetation cover) and labile (e.g. pH) variables. Data were analysed using hierarchical Bayesian models of species richness, α‐ and β‐diversities and functional feeding groups. Assemblage composition was related to landscape and in‐waterbody characteristics. Results Neither measured, nor asymptotic estimates of, species richness differed among landscape types, notwithstanding consistent differences in in‐waterbody habitat characteristics among waterbodies in the two landscape types. There were no discernible differences in patterns of α‐ and β‐diversities at landscape scales relating to landscape type. Habitat diversity of waterbodies at the landscape scale did not affect β‐diversity, although distinct waterbodies within landscapes tended to have more distinct faunas. Main conclusions The lentic macroinvertebrate faunas are relatively homogeneous over the entire region, with little differentiation between wooded and cleared landscapes. The regional fauna may be a homogenized subset of native species, possibly arising from the huge numerical predominance of lentic habitats in agricultural landscapes producing ‘spill‐over’ effects into forested landscapes. Of taxa more frequently found in one or other landscape type, trophic group diversity was greater in forested landscapes.     

The dietary habits of the Brown bear (Ursus arctos) in western Greece

Knowledge of the dietary habits of an endangered species is essential to its management and conservation. The brown bear (Ursus arctos) exists in two isolated population in Greece, but only initial management actions have been taken to improve the habitat of this species. To improve our understanding of the ecology and habitat requirements of this species, we examined the dietary habits of the brown bear in the Panagia-Grevena region, of Macedonia, Greece. In total, 360 scats of brown bear were collected between 2002 and 2004 during spring, summer and autumn months. Scats were analyzed by their frequency of occurrence, volumetric and dry weights, and their importance values. Microhistological analysis was applied to estimate the proportion of wild and cultivated plants in the diet. The most important type of food in the spring was green vegetation, while, in the summer, fruits of Pyrus sp., Morus sp., Prunus sp. and Rubus sp. were important food items. In autumn, hard masts, mainly oak (Quercus sp.), were essential foods for the brown bear. The frequency of vertebrates in the diet was higher in the summer and autumn while that of invertebrates was higher in the spring. In summary, the brown bear is an omnivorous species that lives in Greece and adapts its diet according to food availability and human activities in its habitat. For this reason, human activities in the study area must take the needs and requirement of brown bears into consideration.     

A sampling optimization analysis of soil‐bugs diversity (Crustacea,Isopoda, Oniscidea)

Biological diversity analysis is among the most informative approaches to describe communities and regional species compositions. Soil ecosystems include large numbers of invertebrates, among which soil bugs (Crustacea, Isopoda, Oniscidea) play significant ecological roles. The aim of this study was to provide advices to optimize the sampling effort, to efficiently monitor the diversity of this taxon, to analyze its seasonal patterns of species composition, and ultimately to understand better the coexistence of so many species over a relatively small area. Terrestrial isopods were collected at the Natural Reserve “Saline di Trapani e Paceco” (Italy), using pitfall traps monthly monitored over 2 years. We analyzed parameters of α‐ and β‐diversity and calculated a number of indexes and measures to disentangle diversity patterns. We also used various approaches to analyze changes in biodiversity over time, such as distributions of species abundances and accumulation and rarefaction curves. As concerns species richness and total abundance of individuals, spring resulted the best season to monitor Isopoda, to reduce sampling efforts, and to save resources without losing information, while in both years abundances were maximum between summer and autumn. This suggests that evaluations of β‐diversity are maximized if samples are first collected during the spring and then between summer and autumn. Sampling during these coupled seasons allows to collect a number of species close to the γ‐diversity (24 species) of the area. Finally, our results show that seasonal shifts in community composition (i.e., dynamic fluctuations in species abundances during the four seasons) may minimize competitive interactions, contribute to stabilize total abundances, and allow the coexistence of phylogenetically close species within the ecosystem.     

Diet and feeding behavior of Rhinopithecus brelichi at Yangaoping, Guizhou

Expectations of increases in human population growth and accelerated habitat loss, along with the realization that efforts to provide protection for ecosystems that sustain primates have met with limited success, make it critical that conservation plans are grounded firmly in scientific observation. Studies of the diet breadth and feeding behavior of endangered species, therefore, are critical for understanding ecological adaptations and developing a conservation strategy. The diet and feeding ecology of gray snub-nosed monkeys (Rhinopithecus brelichi) were studied in the Fanjingshan National Nature Reserve, Guizhou, China. The monkeys were found to consume 107 different species of trees, shrubs, and ground plants from 58 genera and 28 families. Food items included young leaves, mature leaves, flowers, fruits/seeds, buds, and insects. Among these food items, there were at least 13 evergreen species of tree and liana, 3 species of grasses, and at least 2 kinds of invertebrates collected from decayed wood. Diet varied markedly throughout different seasons. Overall, diet composition (based on feeding records) was 15.3% buds, 25.5% young leaves, 21.8% mature leaves, 9.4% flowers, 21.6% fruits/seeds, and 6.3% other items. The monkeys feed mainly on young leaves and flowers in spring, unripe fruits/seeds and young leaves in summer, ripe fruits/seeds in autumn, and mature leaves and buds in winter. We propose that when inhabiting forests of lower elevation and greater vegetation complexity, R. brelichi is characterized by expanded diet breadth and includes a greater diversity of food types and plant species in its diet. One food type that appears critical to the diet of this species, especially during the winter, are the buds of Magnolia sprengeri. To protect this resource we advocate working with local communities to limit the collection of M. sprengeri, which is used in traditional Chinese medicine and has high economic value for people in the reserve.     

The nutritional significance of a winter‐flowering succulent for opportunistic avian nectarivores

The winter‐flowering succulent Aloe marlothii provides nectar for many opportunistic avian nectarivores in southern African savannas. We assessed the importance of A. marlothii nectar sugar for opportunistic nectarivores by analysing temporal changes in stable carbon isotope ratios (δ¹³C) in the tissues of birds in Suikerbosrand Nature Reserve, South Africa. The blood of the 11 most common non‐granivorous opportunistic nectarivores at our site was enriched in ¹³C by 3.4 ± 1.5‰ during the flowering period of A. marlothii, reflecting the enriched crassulacean acid metabolism (CAM) isotopic signature of nectar (?12.6 ± 0.5‰). This relatively small contribution of A. marlothii nectar to assimilated carbon in whole blood contrasted with that of exhaled CO₂ in African Red‐eyed Bulbuls Pycnonotus nigricans and Cape White‐eyes Zosterops capensis. In both these species, the δ¹³C of breath samples was significantly enriched compared with blood and feathers, and closely resembled that of the nectar, revealing combustion of ingested nectar rather than assimilation. Although our analysis was complicated by the presence of C₄ grasses, whose δ¹³C values are similar to those of CAM photosynthesizers, when considered with previously published feeding observations our data reveal that opportunistic nectarivores feeding on A. marlothii nectar obtain a relatively small fraction of their assimilated carbon, but most of their metabolized carbon, from this seasonally available carbohydrate food resource. Because the δ¹³C values of insects associated with C₃ plants also became enriched during the flowering season, some insect‐eating opportunistic nectarivores may have assimilated A. marlothii carbon indirectly from insects. This study highlights the importance of understanding isotopic routing when assessing the nutritional significance of specific dietary items to consumer communities.     

Large herbivore grazing and invertebrates in an alpine ecosystem

The literature on how plants respond to grazing and other disturbance factors have advanced greatly in recent decades, but studies of invertebrates are comparably few. We here quantify the effects of 3 levels of sheep grazing on selected invertebrates in an alpine ecosystem in Norway. We tested the hypothesis that invertebrates are more sensitive to grazing than plants (responding mainly at high density), and that primary consumers (herbivorous beetles) are more sensitive than predatory species (beetles and spiders). We captured 1218 specimens belonging to 44 beetle species and 6672 specimens belonging to 66 species of spiders. The community was dominated by few species: 5 beetle and 3 spider species made up 53.0% and 37.4% of the catch, respectively. At the local (plot) scale, most negative responses were only recorded at high sheep density, and invertebrates were thus not more responsive than the plant community. Two dominant herbivorous beetles responded to grazing while 3 dominant species of predatory beetles did not (one marginally). Spider species richness and frequency of occurrence of 2 dominant species were negatively affected by sheep grazing, suggesting variation between different taxonomic groups of predators. Further functional details than simple classification like herbivorous, predatory and litter-dwelling invertebrates seem to be required before a framework to predict responses to disturbance are robust.     

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.     

Activity patterns, diets and interspecific interactions of coexisting spring and autumn breeding carabids: Carabusyaconinus and Leptocarabus kumagaii (Coleoptera, Carabidae)

Abstract. 1. Activity patterns, diets and interspecific interactions of two coexisting carabid beetles, Carabus yaconinus B. and Leptocarabus kumagaii K. et K., were studied in a lowland habitat in Japan.
2. Larvae of C. yaconinus appeared from May to October and fed on earthworms. Those of L. kumagaii appeared from October to the next May and fed on dipteran and lepidopteran larvae.
3. In the adult stages, feeding habits and daily activities of the two species were similar. The beetles fed mainly on earthworms and other animal materials, but various plant materials were also utilized.
4. Direct competition for food items was observed both intra- and interspecifically. Interspecific interactions occurred only in early summer, however, because of the difference in breeding seasons (i.e. spring for C. yaconinus and autumn for L. kumagaii).
5. The difference in seasonal life history patterns between these carabids is a possible mechanism of coexistence.