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171.
172.
Anna Soler-Membrives Sergio Rossi Toms Munilla 《Estuarine, Coastal and Shelf Science》2011,92(4):819-597
Fatty acid analysis has proved valuable in determining seasonal trophic links and the feeding behavior in organisms in which these diet and trophic links cannot be inferred from stomach content analyses. Seasonal variations in total free fatty acid content (TFFA) and fatty acid composition of seston (<250 μm), the brown macroalgae Stypocaulon spp., polychaetes (Nereididae) and the pycnogonid Ammothella longipes have been used to establish their trophic links, with particular focus on seasonality and feeding ecology of A. longipes. Samples were collected in a coastal environment (NW Mediterranean Sea) at 7–10 m depth, in five different periods (August and October 2008, February, June and September 2009). Seston and Stypocaulon spp. samples did not show significant seasonal variations in TFFA content, while nereids showed a significant variation. Analysis of fatty acid profile showed high similarities of fatty acid composition between seston and Stypocaulon spp. Nereids were closer to seston and Stypocaulon spp. than A. longipes, which seemed to follow a seasonal trend. The results of this study reveal that A. longipes may change its feeding behavior depending on the season and available food. This pycnogonid species appears to be carnivore during spring and early summer but seems to feed on detritus when availability of prey diminishes during winter. Notable high amounts of odd-chain fatty acids are found in summer–autumn for this species, which may come from bacteria acquired from the detrital diet or from de novo biosynthesis from propionate. The results obtained provide new and valuable data on the understudied feeding biology of pycnogonids in general, and contribute to the understanding of their functioning of Mediterranean shallow oligotrophic systems and their trophic links. 相似文献
173.
Mark Brenner Thomas J. Whitmore Jason H. Curtis David A. Hodell Claire L. Schelske 《Journal of Paleolimnology》1999,22(2):205-221
We explored the use of carbon and nitrogen isotopes (13C and 15N) in sedimented organic matter (OM) as proxy indicators of trophic state change in Florida lakes. Stable isotope data from four 210Pb-dated sediment cores were compared stratigraphically with established proxies for historical trophic state (diatom-inferred limnetic total phosphorus, sediment C/N ratio) and indicators of cultural disturbance (sediment total P and 226Ra activity). Diatom-based limnetic total P inferences indicate a transition from oligo-mesotrophy to meso-eutrophy in Clear Lake, and from eutrophy to hypereutrophy in Lakes Parker, Hollingsworth and Griffin. In cores from all four lakes, the carbon isotopic signature of accumulated OM generally tracks trophic state inferences and cultural impact assessments based on other variables. Oldest sediments in the records yield lower diatom-inferred total limnetic P concentrations and display relatively low 13C values. In the Clear, Hollingsworth and Parker records, diatom-inferred nutrient concentrations increase after ca. AD 1900, and are associated stratigraphically with higher 13C values in sediment OM. In the Lake Griffin core, both proxies display slight increases before ~1900, but highest values occur over the last ~100 years. As Lakes Clear, Hollingsworth and Parker became increasingly nutrient-enriched over the past century, the 15N of sedimented organic matter decreased. This reflects, in part, the increasing relative contribution of nitrogen-fixing cyanobacteria to sedimented organic matter as primary productivity increased in these waterbodies. The Lake Griffin core displays a narrow range of both 13C and 15N values. Despite the complexity of carbon and nitrogen cycles in lakes, stratigraphic agreement between diatom-inferred changes in limnetic total P and the stable isotope signatures of sedimented OM suggests that 13C and 15N reflect shifts in historic lake trophic state. 相似文献
174.
Understanding the trophic interactions of ecologically important mesopredators such as Myliobatiformes (stingrays) is vital, but, given their susceptibility to overexploitation, the collection of stomach contents for dietary analysis necessitates the use of non-lethal methods. We provide a detailed method of using gastric lavage to collect stomach contents from the ‘Vulnerable’ porcupine ray Urogymnus asperrimus at the St Joseph Atoll of the Amirantes Group, Seychelles. Rays were captured by hand, inverted and restrained while a plastic hose, connected to a bilge pump, was inserted into the stomach to flush out the contents. A high percentage (94.5%) of gastric lavage attempts resulted in the collection of stomach contents. There was no visual evidence of stress or short-term, post-release mortality and, given the success and relative ease of this technique, we conclude that the described method of gastric lavage is an effective, non-lethal means of obtaining stomach contents from stingrays. 相似文献
175.
Partitioning of the feeding niche along spatial,seasonal and size dimensions by the fish community in a tropical Bay in Southeastern Brazil 下载免费PDF全文
Ana Paula P. Guedes Francisco G. Araújo André L. M. Pessanha Rosana R. Milagre 《Marine Ecology》2015,36(1):38-56
Feeding guilds and spatial, seasonal and ontogenetic changes in the diets of 24 fish species in a tropical bay in Southeastern Brazil were examined. The hypotheses tested were that groups of species form specific trophic guilds and that the feeding partitioning differs along the niche dimensions. Five trophic guilds (Polychaeta, Copepoda, Teleostei, Teleostei/Crustacea and Polychaeta/Crustacea) and two species with specialised feeding, one teleost (Aspistor luniscutis) and one bivalvia (Sphoeroides testudineus), were found. Polychaeta was the most important resource for nine fish species, followed by Copepoda (6 spp.), Teleostei (5 spp.) and Caprelidae Amphipoda (3 spp.). Polychaeta was the most used resource for species in the inner bay zone, and Crustaceans in the outer bay zone. We detected a predominance of Polychaeta between the spring and autumn, whereas crustaceans were consumed at a greater rate in the winter. The most conspicuous changes in diet occurred along the spatial and seasonal dimensions, rather than the size dimensions. The hypotheses tested were accepted. Identifying and incorporating information about the bay food web is a first step towards developing management strategies that are sensitive to this particular ecosystem. 相似文献
176.
Stable carbon and nitrogen isotopes were used to investigate nutrient pathways and trophic relationships from the rice-crab system in Panjin,Liaoning Province,China. Values of δ 13 C ranged from-27.38‰±0.44‰ to-18.34‰±0.26‰ and δ 15 N ranged from 1.10‰±0.88‰ to 9.33‰±0.57‰. Pseudorasbora parva(Stone moroko) had the highest δ 13 C and δ 15 N values. The lowest δ 13 C values were obtained for the macrophytes and the lowest δ 15 N value was found in sediments. Stable carbon and nitrogen isotopes were used to determine the contribution of different food items to the diets of crabs. The δ 13 C results indicated that the P seudorasbora parva made the greatest contribution to the diet of E riocheir sinensis(Chinese mitten crab),while the δ 15 N results indicated that most food items contributed more than 10% to the diet of the crab. There were three trophic levels identified in the system(Levels 0–2). The crab Eriocheir sinensis,fish Pseudorasbora parva and Misgurnus anguillicaudatus(Oriental weatherfish),and the oligochaete L imnodrilus hoffmeisteri(Limnodrilus worm),were at the second level,zooplankton were at the first level and suspended particulate matter and macrophytes were at trophic position 0. 相似文献
177.
陈昌齐 《广东海洋大学学报》1991,(2)
采用常规统计方法,对影响湖、库营养状况的12项因素数据进行了分析。从因素数值在同一营养型内分布的稳定性、在不同营养型间的差异显著性以及因素彼此间的相关性出发,为各因素在湖、库营养型划分中的作用提供参考。结果表明,就所讨论的因素而言,浮游植物产量、总氮、有机物耗氧最为重要,浮游动物量、浮游植物现存量、无机氮、总磷有一定作用;pH盐量、活性磷无甚价值。 相似文献
178.
We present here a pilot study to examine trophic level effects and migration patterns at the middle Shang Dynasty site of Xiaoshuangqiao in Henan Province using δD results combined with δ13C and δ15N values. A total of 33 specimens (17 humans, 7 cattle, 5 pigs, 3 sheep, 1 dog) of bone collagen were isotopically analyzed for δ13C, δ15N, and dD values. A strong positive correlation (R2 = 0.94) between mean δ15N and δD values of herbivores (cattle and sheep), omnivores (pig), carnivores (dog) and humans was observed. The δD results were found to increase by ~10‰ to 20‰ from herbivores to omnivores to carnivorous, evidence that collagen δD results are a useful indicator for the study of trophic levels and dietary patterns at archaeological sites. The δD results were also used to examine the origins of two different groups of individuals buried at Xiaoshuangqiao. Individuals buried in sacrificial pits of district V had mean δD values (?47.0 ± 2.9‰, n = 11) that were significantly (p = 0.049) elevated compared to the people buried in the stratigraphy of district IX (?51.3 ± 3.3‰, n = 3), indicating that they were ingesting water from different locations. In addition, the D values of the people buried in the stratigraphy were similar to the pigs (?54.5 ± 4.2‰, n = 5) at Xiaoshuangqiao, suggesting that they were most probably of the local population, and that the individuals buried in the sacrificial pits were most possibly from the coast and prisoners of the Dongyi (“东夷”) people. Thus, δD results have the potential to examine human origins and migration patterns and should be increasingly used in conjunction with δ13C and δ15N values at archaeological sites. 相似文献
179.
应用物质平衡模型模拟一个半封闭海湾的营养结构和能流特征 总被引:4,自引:1,他引:3
The marine ecosystem of the Jiaozhou Bay has degraded significantly in fisheries productivity and its ecological roles as spawning and nursery ground for many species of commercial importance has been declining in recent years. A mass-balanced trophic model was developed using Ecopath with Ecosim to evaluate the trophic structure of the Jiaozhou Bay for improving ecosystem management. The model were parameterized based on the fisheries survey data in the Jiaozhou Bay in 2011, including 23 species groups and one detritus group according to their ecological roles. The trophic levels of these ecological groups ranged from 1(primary producers and detritus) to4.3(large demersal fishes). The estimated total system throughput was 12 917.10 t/(km~2·a), with 74.59% and25.41% contribution of the total energy flows from phytoplankton and detritus, respectively. Network analyses showed that the overall transfer efficiency of the ecosystem was 14.4%, and the mean transfer efficiency was 14.5%for grazing food chain and 13.9% for detritus food chain. The system omnivory index(SOI), Finn's cycled index(FCI) and connectance index(CI) were relatively low in this area while the total primary production/total respiration(TPP/TR) was high, indicating an immature and unstable status of the Jiaozhou Bay ecosystem. Mixed trophic impact analysis revealed that the cultured shellfish had substantial negative impacts on most functional groups. This study contributed to ecosystem-level evaluation and management planning of the Jiaozhou Bay ecosystem. 相似文献
180.
内蒙古岱海水体营养状况分析 总被引:2,自引:0,他引:2
岱海是我国半干旱区的一个典型内陆湖。近年来,由于受到流域人类活动的强烈干预,湖泊水位持续下降,湖面不断萎缩。与此同时,湖泊水质也呈现出明显的恶化趋势,2004年水质监测结果显示,湖水中TN、TP和CODMn均出现超标,全湖水质达到劣Ⅴ类。采用综合营养状态指数法进行评价,岱海水体已处于中度富营养化水平,但受湖周生产布局的影响,营养状况空间分布有所差异,自湖西向湖东,营养状态指数逐渐减小,富营养化程度也相应降低。在时间变化上,岱海已由1996年的中营养化过渡到2004年的中度富营养化,上升了两个营养级别。引起岱海水质恶化的原因主要是农田地表径流及城镇所产生的生活污水,另外,湖泊的不断萎缩也是一个不容忽视的影响因素。为防止岱海水环境继续恶化,根据流域特点提出了一些具体的防治对策和建议。 相似文献