Average δ15N Values Research Articles

Mercury biomagnification in the food chain of a piscivorous turtle species (Testudines: Chelidae: Chelus fimbriata) in the Central Amazon, Brazil.

Due to their natural history and ecological attributes, turtles are excellent organisms for studies of heavy metal contamination. Turtles have a large geographical distribution, occupy different aquatic habitats, and occupy various trophic levels. The present study investigated mercury bioaccumulation in the carnivorous chelonian Chelus fimbriata (Matamata turtle) and Hg biomagnification in relation to its aquatic food chain in the middle Rio Negro, AM-Brazil. Tissue samples of muscle, carapace and claws were collected from 26 C. fimbriata individuals, as well as collections of autotrophic energy sources found in the turtle's aquatic habitat area. The samples were collected in February-March/2014 and analyzed for THg concentrations and carbon (δ13C) and nitrogen (δ15N) stable isotopes. The highest THg levels were found in claws (3780 ng.g-1), carapace (3622 ng.g-1) and muscle (403 ng.g-1), which were found to be significantly different [F(2.73) = 49.02 p < 0.01]. However, THg concentrations in muscle tissue were below the consumption threshold indicated by the WHO and Brazilian Health Ministry. The average δ13C and δ15N values in Matamata samples were -31.7‰ and 11.9‰, respectively. The principal energy source sustaining the food chain of C. fimbriata was found to be terrestrial shrubs, with smaller contributions from emergent aquatic herbaceous plants and algae, while δ15N values showed its trophic position to be two levels above the autotrophic energy sources. There was a positive correlation between THg and turtle size, while a significant relationship was found between THg and δ15N, showing strong biomagnification in the food chain of C. fimbriata: y = 0.21x + 0.46; r2 = 0.45; p < 0.001, for which the slope presented a value of 0.21.

A nitrogen isoscape of phytoplankton in the western North Pacific created with a marine nitrogen isotope model

The nitrogen isotopic composition (δ15N) of phytoplankton varies substantially in the ocean reflecting biogeochemical processes such as N2 fixation, denitrification, and nitrate assimilation by phytoplankton. The δ15N values of zooplankton or fish inherit the values of the phytoplankton on which they feed. Combining δ15N values of marine organisms with a map of δ15N values (i.e., a nitrogen isoscape) of phytoplankton can reveal the habitat of marine organisms. Remarkable progress has been made in reconstructing time-series of δ15N values of migratory fish from various tissues, such as otoliths, fish scales, vertebrae, and eye lenses. However, there are no accurate nitrogen isoscapes of phytoplankton due to observational heterogeneity, preventing improvement in the accuracy of estimating migratory routes using the fish δ15N values. Here we present a nitrogen isoscape of phytoplankton in the western North Pacific created with a nitrogen isotope model. The simulated phytoplankton is relatively depleted in 15N at the subtropical site (annual average δ15N value of phytoplankton of 0.6‰), where N2 fixation occurs, and at the subarctic site (2.1‰), where nitrate assimilation by phytoplankton is low due to iron limitation. The simulated phytoplankton is enriched in 15N at the Kuroshio–Oyashio transition site (3.9‰), where nitrate utilization is high, and in the region around the Bering Strait site (6.7‰), where partial nitrification and benthic denitrification occur. The simulated δ15N distributions of nitrate, phytoplankton, and particulate organic nitrogen are consistent with δ15N observations in the western North Pacific. The seamless nitrogen isoscapes created in this study can be used to improve our understanding of the habitat of marine organisms or fish migration in the western North Pacific.

Inter- and intrapopulation resource use variation of marine subsidized western fence lizards

Marine resource subsidies alter consumer dynamics of recipient populations in coastal systems. The response to these subsidies by generalist consumers is often not uniform, creating inter- and intrapopulation diet variation and niche diversification that may be intensified across heterogeneous landscapes. We sampled western fence lizards, Sceloporus occidentalis, from Puget Sound beaches and coastal and inland forest habitats, in addition to the lizards’ marine and terrestrial prey items to quantify marine and terrestrial resource use with stable isotope analysis and mixing models. Beach lizards had higher average δ13C and δ15N values compared to coastal and inland forest lizards, exhibiting a strong mixing line between marine and terrestrial prey items. Across five beach sites, lizard populations received 20–51% of their diet from marine resources, on average, with individual lizards ranging between 7 and 86% marine diet. The hillslope of the transition zone between marine and terrestrial environments at beach sites was positively associated with marine-based diets, as the steepest sloped beach sites had the highest percent marine diets. Within-beach variation in transition zone slope was positively correlated with the isotopic niche space of beach lizard populations. These results demonstrate that physiography of transitional landscapes can mediate resource flow between environments, and variable habitat topography promotes niche diversification within lizard populations. Marine resource subsidization of Puget Sound beach S. occidentalis populations may facilitate occupation of the northwesternmost edge of the species range. Shoreline restoration and driftwood beach habitat conservation are important to support the unique ecology of Puget Sound S. occidentalis.

Elemental (CNS) and isotopic (δ13C and δ15N) characterization of local sources to atmospheric dust at Trombay, Mumbai, using elemental analyzer–isotope ratio mass spectrometry

Particulate matter (PM) in the air has significant implications for human health and the environment, particularly in urban areas with high concentrations. This study focuses on the isotopic (δ13C and δ15N), elemental (CNS) as well as the total carbon to total nitrogen ratio (TC/TN) characterization of PM in Trombay, Mumbai. Monthly atmospheric dust samples were collected from 2016 to 2020 during the premonsoon and postmonsoon seasons. The average elemental concentrations for premonsoon samples were N (1.73% ± 0.25%), C (7.38% ± 0.72%), S (0.84% ± 0.13%), and TC/TN ratio (4.38 ± 0.86). For postmonsoon samples, the average elemental concentrations were N (1.47% ± 0.185%), C (6.95% ± 1.04%), S (0.84% ± 0.13%), and TC/TN ratio (4.80 ± 0.94). The average δ13C values for premonsoon and postmonsoon seasons were −24.31 ± 1.15‰ and −24.56 ± 1.20‰, respectively. The average δ15N values for premonsoon and postmonsoon seasons were 5.22 ± 1.92‰ and 4.57 ± 1.32‰, respectively. The results showed variations in elemental concentrations between the seasons, with higher values observed in premonsoon samples which can be attributed to increased dust generation from land and sea. Overall, this study provides insights into the local sources and characteristics of PM in the Trombay area and highlights the importance of long-term monitoring to understand the seasonal variations in PM composition.

Amino acid‐specific nitrogen stable isotope analysis reveals the trophic behavior of Icelandic fin whales in winter and suggests variable feeding strategies

AbstractFin whales (Balaenoptera physalus) aggregate west of Iceland during summer, where they feed mostly on krill, but their winter distribution is poorly known. This study investigates the winter behavior of fin whales that summer off Iceland by analyzing amino acid‐specific nitrogen isotope ratios in the baleen plates. This technique is increasingly used in large marine vertebrates to discriminate between changes in trophic position and changes in isotopic baseline levels, while ruling out the effect of fasting on these patterns. Analyses were conducted on samples extracted from two baleen plate segments: one corresponding to winter, another to summer. The trophic position was higher and slightly more variable in winter (3.6 ± 0.7) than in summer (3.0 ± 0.4), which indicates that during winter fin whales tend to feed on fish and are more generalist in feeding habits. Interestingly, the δ15NPhe values were not lower in winter than in summer (winter: 5.2‰ ± 2.4‰; summer: 4.0‰ ± 2.1‰). This was unexpected because baseline δ15N values (e.g., zooplankton) tend to be lower at low latitudes, where fin whales are believed to spend the winter. Fin whales may remain in relatively high latitudes during winter or visit low‐latitude areas with locally higher than average δ15N values, such as upwelling areas.

Gender across Generations

Food is a biological imperative as well as a core material that humans use in socializing ourselves, and the things we choose to consume are infused with cultural meanings. Children, especially very young children, have little agency in subsistence decisions, and therefore the foods that caretakers feed to children may hold profound information about cultural value systems and reveal social processes and idealized identities. Here we focus on relationships between food, sex, and gender in early life by studying the childhood diets of 57 Eastern Zhou period individuals from the Central Plains region of China (771–221 BCE). Using stable isotope analysis of incremental dentin samples, we create detailed dietary histories of childhood years. From very early in life, the average δ15N value for boys is notably higher than the average for girls, indicating slightly more protein consumption for most males, and this continues across childhood. Foods such as meat and millet were highly valued in ancient China and, whether intentional or not, become associated with aspects of sex and gender through preferential feeding to male children. These isotopic data reveal a key aspect of the socializing processes of children across generational interactions with caretakers, with food communicating information about social worth and gender, which becomes embodied in the developing child.

Downed deadwood habitat heterogeneity drives trophic niche diversity of soil-dwelling animals

Habitat heterogeneity is one of the important drivers of biodiversity, but the underlying mechanisms are still vague. Increasing habitat heterogeneity often coincides with greater habitat space and/or greater food availability for organisms, but it is unclear whether and how these components are related to habitat selection. Downed dead wood (i.e., dead wood laying on the ground) is an important but understudied component of dead plant matter that creates spatial habitat heterogeneity for soil fauna on the ground. To unravel the role of dead wood for providing niche dimensionality for soil fauna via variance in resource use, we sampled Collembola communities from moss growing on bark and from bark on the logs of two tree species (pedunculate oak and Norway spruce) and from soil next to the logs. We assessed habitat selection of Collembola species combining abundance data with trophic position data using stable isotope ratios (i.e., δ13C and δ15N). Based on the Bray-Curtis dissimilarity, Collembola community composition differed significantly among the three habitats (i.e., moss, bark and soil). Collembola community-weighted mean δ13C and δ15N values also differed among the three habitats (average δ13C values of moss: −25.94‰, bark: −25.30‰, soil: −25.60‰; average δ15N values of moss: −4.80‰, bark: −3.83‰, soil: −5.11‰), partly reflecting isotopic differences of the habitats themselves (δ13C of moss: −29.83‰, bark: −28.26‰, soil: −29.04‰; δ15N of moss: −7.59‰, bark: −4.18‰, soil: −7.84‰). These findings indicate that Collembola depend on food sources derived from the habitats they inhabit at least at the community level. Collembola community-weighted variance of both δ13C and δ15N values ranked as bark > moss > soil. Species-level data suggested that the bark community included both bark-specific food specialists as well as species which likely use bark only as a temporary habitat based on their morphological traits supporting high mobility. These findings together indicate that the trophic niche variation of the Collembola community is larger in bark than in soil. Our results stress the importance of downed dead wood as a source of habitat heterogeneity, which in turn promotes soil animal diversity, likely via heterogeneity in food sources. Furthermore, the presence of dead wood on the ground could have consequences for organic matter processing by the soil animal community through sustaining a larger trophic niche variation even at a small spatial scale.

Assessing the influence of sewage outfalls on seagrass meadows using nitrogen isotopes

Untreated sewage discharged increases the nutrient loads and changes ecosystem functions. It increases the values of the nitrogen isotopic signature (δ15N) of primary producers such as seagrasses. Itaparica Island (Bahia, Brazil) has undergone extensive urbanization over 50 years. Most of the island has no sewage treatment, and a bridge's construction could increase its population ten times. We evaluated the effects of sewage inputs on the δ15N of seagrass (Halodule wrightii) across Itaparica Island in 14 areas of the island with different degrees of urbanization. Average values of δ15N ranged from −3.95 ‰ (±1.04 SD) to 2.73 ‰ (±1.61). The highest human occupation site also has the highest mean value of δ15N, and seagrass shoot density. The significant correlation (p < 0.05) between δ15N values and shoot density may indicate a possible anthropogenic pressure impacting meadow abundance. Despite a positive correlation, increased anthropogenic nutrient supply can support algae growth and harm seagrass ecosystems.

Diet of deep-sea holothurians in theVolcanologists Massif, Bering sea, as inferred from stable isotope and fatty acid analyses

Holothurians are one of the key components of the deep-sea megabenthos, often forming significant aggregations with high abundance and biomass. The crucial factors determining the pattern of their spatial distribution might be their food strategies, as well as the quantity and quality of available food. Using the set of trophic markers (analysis of fatty acid (FA) composition and stable nitrogen and carbon isotope signatures), we studied the trophic preferences of four common species of deep-sea holothurians (Paelopatides sp., Pannychia henrici, Psolidium sp., and Scotoplanes kurilensis) inhabiting the Volcanologists Massif, Bering Sea, at depths from 984 m to 3395 m. The δ13С values in tissues of all four species varied slightly (from −16.2 to −16.6‰) and were significantly higher than those in sediment organic matter (SOM) (on average, −21.5‰), which indicates the use of organic matter of the same origin by all species. The δ15N values (10.1–12.9‰) were also significantly higher than in SOM (on average, 4.4‰). The lowest average δ15N value was recorded for the deepest-dwelling species (Scotoplanes kurilensis), and the highest value from the shallowest-dwelling ones (Psolidium sp.). All the species differed significantly in FA composition. Psolidium sp. was distinguished by the highest saturated FA content (45.5%) and the lowest polyunsaturated FA (PUFA) content (18.7%). In the rest of the species, PUFAs dominated (>35%). The ratios of major PUFAs varied among the four species studied but all holothurians species were rich in phytoplankton derived FA suggesting tight trophic coupling to phytodetritus. However, for Psolidium sp., bacteria could constitute a substantial portion in the diet. The high level of 20:4n-6 might indicate a significant contribution of protozoans to the diet of Pannychia henrici. Paelopatides sp. and Scotoplanes kurilensis were characterized by a high level of 20:5n-3 and a high value of the 20:5n-3/20:4n-6 ratio, which indicates the predominance of fresh phytodetritus in their diet. The high level of primary production in the upper layers of the Bering Sea provides the high quality of the sedimentary OM and food supply of deposit feeders even at the greatest depths.

15N Natural Abundance Characteristics of Ammonia Volatilization from Soils Applied by Different Types of Fertilizer

Ammonia (NH3) volatilized from cropland significantly impacts the ecological environment and human health. The identification and quantification of atmospheric sources of NH3 from cropland are therefore important for NH3 emission reduction and air pollution control. Choosing appropriate nitrogen (N) fertilizer types is one of the key ways to reduce NH3 emissions from agricultural systems due to different N fertilizers with different emission factors. The natural abundance isotope of N (δ15N) values can well identify the source of NH3 volatilization, although there is rare research on δ15N-NH3 values volatilized when applying different types of N fertilizers. Here, we conducted an incubation experiment to study the characteristics of δ15N-NH3 values during the whole volatilization process after different N fertilizers were applied to the soil. The results show that the cumulative NH3 volatilization from urea (U), urease inhibitor fertilizer (UI), compound fertilizer (CF) and ammonium nitrate phosphate fertilizer (AP) treatment was 5.25 ± 0.00, 3.11 ± 0.00, 3.22 ± 0.19 and 1.38 ± 0.12 kg N ha−1 at the end of the 15-day incubation period, respectively. The average δ15N value of NH3 volatilized from the U, UI, CF and AP treatments was −36.02 ± 4.95, −29.08 ± 9.70, −35.18 ± 4.98 and −29.42 ± 4.33‰, respectively. Generally, the δ15N-NH3 values ranged from −41.33 to −6.30‰ during the NH3 volatilization process. The δ15N-NH3 value was lower in the U treatment than in the UI and AP treatments (p &lt; 0.05), which suggests that N forms and the slow-release additions of different fertilizers, such as NO3−-N and urease inhibitors, can delay or slow down NH3 volatilization, resulting in relative isotopic enrichment. Therefore, the basic properties of different N fertilizers, the changes in soil NH4+-N and cumulative NH3 during the volatilization process significantly impacted the δ15N-NH3 values.

Stable Isotope Analysis Supports Omnivory in Bank Voles in Apple Orchards

With only periodic and incomplete studies of its diet over time, all with differing methods and conclusions, the degree of omnivory in the bank vole (Clethrionomys glareolus) is not fully clear. We assessed the trophic niche of the species using isotopic (δ15N and δ13C) compositions from hair samples and analysed how C. glareolus shares trophic space with herbivores, granivores and insectivores living syntopically. According to the numbers trapped, C. glareolus was the fourth most numerous species in the apple orchards that we investigated, accounting for 14.4% of all trapped small mammals with a relative abundance of 1.12 individuals per 100 trap nights. The average values of both δ15N and δ13C in the hair of C. glareolus differed from the other trophic groups, with the average of δ15N in orchards and neighbouring habitats (6.55–6.95‰) being closest to that of insectivores. Intraspecific trophic niche differences (depending on age, gender and reproductive status) were not expressed, while correlations between body mass, body condition index and both δ15N and δ13C values were not consistent. In comparison to analysed basal resources, isotopic signatures in the hair were closest to the values in invertebrates and apple seeds. The degree of omnivory in C. glareolus was not the same in different habitats. This may be an indication of ecological plasticity within the species, allowing its inclusion/success in multi-species small mammal communities.

Tracing the organic matter source of cage culture sediments based on stable carbon and nitrogen isotopes in Poyang Lake, China

Collected sediment samples from the cage fish farm were measured to determine carbon and nitrogen stable isotope compositions and to understand the influence of the aquaculture waste on the sediment. The average δ13C of the sediment organic matter was −27.2 ‰ and −26.5 ‰, and the average δ15N value was 5.6 ‰ and 6.2 ‰ in October 2017 and November 2018, respectively. A linear mixing model was used to calculate the contribution ratios of the aquaculture waste in sediment organic matter. The contribution ratio of fish feces was 53.9 % and 25.5 %, and the contribution ratio of waste feed was 18.4 % and 52.6 % in October 2017 and November 2018, respectively. The sediment in the “cage fish area” was characterized by high waste feed ratio in sediment organic matter. The sediment organic matter was affected by the aquaculture waste even at sites 1500 m away from the cage fish farm.

Seasonal source analysis of nitrogen and carbon aerosols of PM2.5 in typical cities of Zhejiang, China

Fine particulate matter (PM2.5) significantly impacts global air quality and human health due to its smaller particle size and larger specific surface area. Nitrogen and carbon aerosols, as the main components of PM2.5, play key roles in air pollution. This study identified the sources and seasonal variation of nitrogen and carbon aerosols in PM2.5 in typical cities of Zhejiang. The annual average PM2.5 concentrations of Hangzhou (HZ), Ningbo (NB), and Huzhou (HUZ) were 39.8 ± 19.1 μg m−‍3, 40.0 ± 21.5 μg m−3, and 50.1 ± 22.6 μg m−3, respectively, which exceeded the Chinese air quality limit of 35.0 μg m−3. The results showed that the concentrations of nitrogen aerosols (NO3− and NH4+) in water-soluble inorganic ions were higher at 9.6 ± 4.6 μg m−3, 9.0 ± 4.5 μg m−3 and 11.5 ± 5.4 μg m−3 in HZ, NB and HUZ, respectively, especially in winter, accounting for over 60% of the total. The annual average δ15N values of PM2.5 were 6.2 ± 1.9‰, 6.4 ± 2.2‰ and 6.7 ± 1.9‰ in HZ, NB and HZ, respectively; the δ15N values in winter were relatively low. A Bayesian isotopic mixing model was employed to analyse the sources of nitrogen aerosols in winter; the results showed that nitrogen concentration was mainly affected by NH3 and NOX emitted by motor vehicle exhaust, coal combustion, biomass combustion, biogenic soil emissions, animal wastes and ocean evaporation (NB). In addition, the carbon component analysis of PM2.5 showed that the annual average mass concentration of TC accounted for 18.7%, 16.4% and 20.1% of PM2.5 in HZ, HUZ and NB, respectively. The same isotope model was used to analyse the sources of carbon aerosols; the results showed that carbon aerosols were mainly affected by the sources of motor vehicle exhaust, coal combustion, biomass combustion and dust. In the PM2.5 in Zhejiang, the most contributory sources of nitrogenous aerosols and carbon aerosols were motor vehicle exhaust sources.

A preliminary study of macrofaunal communities and their carbon and nitrogen stable isotopes in the Haima cold seeps, South China Sea

The macrofaunal community in the Haima cold seeps of the South China Sea was investigated, and trophic relationships were evaluated using carbon and nitrogen stable isotope signatures (δ13C and δ15N). A total of 30 macrofaunal species were identified in this study, most of which were collected from the Gigantidas haimaensis mussel beds. Only four macrofaunal species were collected from the Calyptogena marissinica clam beds, where the environment may not be suitable for the survival of most macrofauna. The bush of slim tubeworms (Sclerolinum sp.) might be an important nursery ground for mussels. G. haimaensis was the predominant species, and its average δ13C and δ15N values were −52.7‰ and 0.6‰, respectively. Compared with the stable isotope signatures of particulate organic matter (POM), it suggested that the food source of macrofauna in the Haima cold seeps was mainly originated from chemosynthetic autotrophs. In the mussel bed, most of the macrofauna had a large δ13C isotopic distance compared with G. haimaensis, suggesting that G. haimaensis was not a direct food source for most cold-seep macrofauna in the mussel bed. The variation in stable isotope signatures of macrofauna might be attributed to different proportions of methanotrophic and thiotrophic endosymbionts. Neolithodes brodiei and Bathynomus jamesi showed the highest δ13C and δ15N values. However, the large isotopic distance indicated that N. brodiei and B. jamesi might just occasionally visit the cold-seep ecosystem and their food sources were mainly from the upper ecosystem relying on photosynthesis. Overall, our results suggested that there was no significant predator-prey relationship among these macrofaunal species in the Haima cold seeps. This study provided important baseline data of stable isotope signatures for further studies to elucidate the trophic interaction among seep organisms.

Manure for millet: Grain δ15N values as indicators of prehistoric cropping intensity of Panicum miliaceum and Setaria italica

Broomcorn and foxtail millet are the only major domesticated plants indigenous to prehistoric Eurasia to rely on the C4photosynthetic pathway. Here we study the impact of animal manure (AM) on broomcorn millet (Panicum miliaceum) and foxtail millet (Setaria italica), grown in the Askov Long-Term Experiment, using unmanured soil and soil dressed with phosphorus plus potassium (PK) as reference treatments. Animal manure had a marked effect on yields and on the δ15N values of grains. For broomcorn millets grown on manured soil, the average δ15N value was 5.8‰. When grown on unmanured and PK-treated soils, the δ15N values were 0.4‰ and 0.2‰, respectively. For foxtail millet the δ15N values also differed between grains from unmanured (-1.0‰), PK (0.7‰) and manured (6.3‰) treatments. Thus, when compared to unmanured soil, the offset due to manure was 7.3‰ for Setaria and 5.3‰ for the two Panicum varieties. In accordance with previous studies on C3 crops, our study suggests that δ15N values in charred millet grains recovered from archaeological sites could provide a robust indicator of prehistoric manuring intensity.

浙江南部近海前肛鳗营养生态位变化研究——基于稳定同位素技术

PDF HTML阅读 XML下载 导出引用 引用提醒 浙江南部近海前肛鳗营养生态位变化研究——基于稳定同位素技术 DOI: 10.5846/stxb202112073477 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（31902372，41906074）；上海海洋大学青年教师科研启动基金（210021）；温台渔业资源专项调查项目（158053） Change of trophic niche of Dysomma anguillare in the offshore waters of southern Zhejiang by stable isotope analysis Author: Affiliation: Fund Project: National Natural Science Foundation of China；National Natural Science Foundation of China 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于2016年和2020年浙江南部近海收集的71尾前肛鳗样品，通过测定碳氮稳定同位素比值计算其营养生态位指标，对比分析前肛鳗不同发育过程、不同季节及不同年份营养生态位的差异，探究营养生态位的变动规律及对资源的利用情况。结果表明：（1）2016年和2020年前肛鳗平均δ13C值分别为（-15.19±0.31）‰、（-15.90±0.45）‰；平均δ15N值分别为（12.42±0.45）‰、（12.92±0.25）‰；（2）单因素方差分析表明，2016年前肛鳗不同发育过程δ13C值差异不显著（P>0.05），δ15N值差异显著（P<0.05），不同季节间δ13C值和δ15N值均存在显著差异（P<0.05），而2020年前肛鳗不同发育过程δ13C值和δ15N值差异均不显著（P>0.05），不同季节间δ13C值存在显著差异（P<0.05），δ15N值差异不显著（P>0.05）；（3）从个体发育来看，2016年前肛鳗有向高营养级饵料生物摄食的趋势，而2020年前肛鳗摄食特化现象不明显，但均随个体发育过程生态位宽幅逐渐减小，表明个体发育过程营养生态位会出现资源竞争共存分化现象；（4）种群营养多样性指标结果显示前肛鳗在秋、冬两季食物来源较春、夏两季更广泛，春季营养多元化程度与秋季相似，夏季营养多元化程度与冬季相似，各季节间营养生态位重叠较小，存在明显的时间分化现象；（5）2020年前肛鳗种群营养结构多样性指标相比2016年均出现不同程度的降低，两年的SEAc未发生重叠现象。由于种内种间的竞争压力，研究发现前肛鳗在个体发育过程及不同时间段都出现了营养生态位分化现象，从而达到维持物种共存、保持食物网结构稳态的目的。 Abstract:Based on 71 Dysomma anguillare samples collected in the offshore waters of southern Zhejiang in 2016 and 2020, the trophic niche indexes were calculated by carbon and nitrogen stable isotope ratio. The trophic niche in different development processes, seasons and years were compared to explore the variation pattern of trophic niche and the utilization of resources. The results showed that:(1) the average δ13C values of D. anguillare in 2016 and 2020 were (-15.19±0.31)‰ and (-15.90±0.45)‰, respectively; The average δ15N values were (12.42±0.45)‰ and (12.92±0.25)‰, respectively; The results of one-way ANOVA showed that there was no significant difference in δ13C value (P>0.05) and δ15N value (P<0.05) at different development processes of D. anguillare in 2016. There were significant differences in δ13C value and δ15N value between different seasons (P<0.05); In 2020, there was no significant difference in δ13C value and δ15N value at different development processes of D. anguillare (P>0.05), there was significant difference in δ13C value between different seasons (P<0.05), and there was no significant difference in δ15N value (P>0.05). (2) From the perspective of ontogeny, the D. anguillare had a tendency to feed on highly trophic level prey food in 2016, while the feeding specialization of D. anguillare was not obvious in 2020, but the niche width decreased gradually with ontogeny, indicating that there would be interspecific resource competition and differentiation in the ontogeny stage. (3) The results of population trophic diversity index showed that the food sources of D. anguillare in autumn and winter were more extensive than those in spring and summer. The degree of trophic diversity in spring was similar to that in autumn, and that in summer was similar to that in winter. The overlap of trophic niche among seasons was small, and there was an obvious phenomenon of time differentiation. (4) Compared with 2016, the diversity index of trophic structure of D. anguillare population in 2020 decreased to varying degrees, and there was no overlap in corrected standard ellipse area (SEAc) in the two years. Due to the pressure of intraspecific and interspecific competition, it was found that there was a phenomenon of nutritional niche differentiation in the process of ontogeny and different time periods, so as to maintain species coexistence and maintain the stability of food web structure. Exploring the adaptive ability of species to the utilization of bait resources and the ecological environment has scientific significance for investigating the structural pattern and stability mechanism of marine food web. 参考文献 相似文献 引证文献

Nutrient and physicochemical properties as potential causes of stress in mangroves of the central Red Sea.

Mangrove ecosystems are some of the most productive and important sinks for sediment globally. Recently, there has been an increasing interest in possible causes of stress in mangroves, such as nutrient limitation, high salinity, solar radiation and temperature. We measured different factors casing stress and determined how they influenced oxidative stress and growth biomarkers in six study sites dominated by mangroves; Al Lith, South Jeddah, Dahban, Thuwal, Rabigh and Mastorah. Significant differences (P < 0.05) were recorded in water salinities and temperatures, nitrogen and phosphorus content in sediments, and antioxidant enzyme activities in different study sites. The highest salinity (40.75 ‰) and temperature (29.32°C) were recorded in the Rabigh mangrove stand, which corresponds to the lowest dissolved oxygen (5.21 mg/L). Total organic carbon, total nitrogen and total phosphorus in sediment across the study areas were in the order Rabigh>Thuwal>Dahban>Al Lith>South Jeddah>Mastorah. Total nitrogen in mangrove leaves at Rabigh was the highest and about 1.3 times higher than the total nitrogen in South Jeddah mangrove ecosystem, very different from the ratio of total nitrogen in the sediments at Rabigh and South Jeddah mangrove ecosystems. The average values of δ13C (-17.60‰) and δ15N (2.84‰) in the six mangrove ecosystems, and the highest δ13C (-13.62‰) and δ15N (4.39‰) at Rabigh in the sediments suggest that nutrient input differed among study sites. Higher nutrient levels at Rabigh mangrove ecosystem were attributed to restricted circulation, camel grazing and land runoff with agricultural waste during seasonal flooding events. However, N limitation and possibly salinity contributed to stress in Al Lith, South Jeddah, Dahban, Thuwal, Rabigh, and Mastorah mangrove ecosystems. Salinity (r = 0.9012) contribute more to stress at Rabigh.

Impacts of Spartina alterniflora invasion on the benthic food web in the Yellow River Delta during autumn

Spartina alterniflora was introduced into the Yellow River Delta (YRD) in 1990 with the purpose of shore protection and siltation accretion. However, it spread rapidly and became a severe threat to the local coastal wetland ecosystem. To assess the impacts of S. alterniflora invasion on the benthic food web, we sampled the potential food sources of macrobenthos in November 2020, analyzed the trophic level and the benthic food web structure based on stable isotope technique. Results showed that the average δ13C values of macrobenthic food sources followed an order: sediment organic matter (SOM) > S. alterniflora > benthic microalgae > particulate organic matter (POM) > Suaeda salsa. The average δ15N values significantly differed among food sources, ranging from 1.24‰ to 9.03‰. The trophic levels of different macrobenthos ranged from 1.73 to 4.19, of which the bivalve species was the lowest one. S. alterniflora and the decayed debris were the most important food sources for macrobenthos, but without any impact on the trophic level structure of macro-benthos. In conclusion, Spartina alterniflora invasion distinctly changed the composition of food sources of macrobenthos through a "bottom-up" effect, which would probably impact the local food web structure in the YRD wetland.

Influence of sedimentary organic matter sources on the distribution characteristics and preservation status of organic carbon, nitrogen, phosphorus, and biogenic silica in the Daya Bay, northern South China Sea

Surface sediment samples were collected from Daya Bay in October 2018, and analyzed for total organic carbon (OC), total nitrogen (TN) and their stable isotopes (δ13C and δ15N), total phosphorus (TP), biogenic silica (BSi), sediment textures and specific surface area (SSA). The primary objective was to evaluate the influence of mariculture/aquaculture on the distribution characteristics of organic matter (OM), and preservation status of OC, TN, TP, and BSi in sediments. The average δ13C and δ15N values, and OC/TN ratios were −21.27‰, 6.74‰, and 8.90, respectively. Monte Carlo simulation results revealed that mariculture/aquaculture biodeposits accounted for >40% of the buried OM at sites where the breeding rafts and cages are located, whereas marine OM increased gradually to the open sea. Terrestrial OM was generally low accounting for 17% by average. The contents and distribution characteristics of biogenic elements were more influenced by mariculture/aquaculture and primary productivity than sediment textures. Lower OC/SSA (0.3–1.2 mg OC/m2), TN/SSA (~0.05–0.18 mg TN/m2), and TP/SSA (0.02–0.04 mg TP/m2) loadings indicated that increased sequestration of labile OM in a coastal bay could contribute to significant degradation of recalcitrant OM in sediments with significant loss of P relative to OC. Nitrogen contamination in surface sediments was due to increased injection of aquaculture biodeposits, and may pose a detrimental effect on the ecological sustainability of the bay. Higher BSi/SSA loadings (0.9–1.7 mg BSi/m2) revealed that BSi was more preserved, and that BSi-based proxy could be used for paleo-productivity studies. However, such preservation may induce adverse dissolved silicate limitation in a bay perturbed by eutrophication. Fine-grained sediments (clay and silt) accounted for >77% of the sediment texture types with higher SSA, and while controlling the contents of biogenic elements under given depositional conditions were not the main determining factors of OC, TN, TP, and BSi preservation.

Variations in Nitrogen Isotope Composition in Clay Deposits of the Permian–Triassic Boundary Beds in the Verkhoyansk Region (Northeast Asia) and Their Implication for Reconstruction of Marine Environments

The first sediment N-isotope data on the Permian–Triassic boundary transition of the Verkhoyansk region are obtained. Together with the other published materials on other regions of eastern Russia allow us to distinguish a number of N-isotope intervals of various ranks in the Permian–Triassic of eastern Russia. In addition to the well-known method of reconstructing the redox conditions of the marine environment from N‑isotope data (in combination with data on elevated concentrations of redox-sensitive trace metals), the possibility of using N-isotope data also to determine the direction of temperature changes in the marine environment is substantiated. It is assumed that N-isotope signals are primarily a reflection of events associated with denitrification and N2 fixation, the main processes of the global nitrogen biogeochemical cycle (NBC). Deviations in the direction of increasing δ15N values in the considered sections are associated with an increase in upwelling activity and the supply of cool deep waters enriched in the heavy N isotope to the shelf zone; the opposite deviations are associated with a slowdown or cessation of inflow of cool deep waters. The N-isotope data obtained, in combination with the published materials on O-isotope thermometry in the Tethyan Superrealm during the Permian and Triassic, indicate a very likely coincidence of the direction of temperature changes caused by both regional (upwelling) and global (climatic) events of that time. In this regard, the reconstructions of the marine environment that we conduct by the example of the Permian–Triassic sections of Northeast Asia (Verkhoyansk, Kolyma–Omolon, and South Primorye) seem to be appropriate, although they require additional confirmation on the material from other sections of the world. The problems associated with differences in the average δ15N values in the Permian–Triassic sections of different provinces of the Boreal Superrealm, as well as other superrealms, are considered.