菲尔德斯半岛潮间带生态系统中的食物网

菲尔德斯半岛潮间带食物链是较简单的 ,一般说来在不利环境条件下的生物群落只有很少的消费者和较少的营养级。食物链中主要的生产者是大型底栖藻类 ,主要消费者是腹足类和石鳖 ,棘皮动物中的海胆与海星 ,甲壳动物 ,鱼和海鸟 ,海鸟和鱼占营养级的上层 ,草食软体动物位于中间营养级 ,大量的固着藻类 -叶状藻类、皮壳状藻类构成营养级的底层。观测实验表明 :(1 )海鸟和鱼类减少了草食性软体动物和肉食性螺类的数量 ;(2 )肉食性腹足类减少了草食性软体动物和固着无脊椎动物的数量 ;(3 )草食性软体动物减少了叶状藻类的数量并影响到皮壳状藻类的数量 ,在不清除消费者的实验中 ,皮壳状藻类显示出与其它固着生物竞争空间的优势。作者观察了并在本文中描述了异性底质与消费者对固着生物多样性的影响。壳状藻类在低潮带岩石表面占优势 ,其它的固着生物 (叶状藻类与固着无脊椎动物 )占据洞穴和狭缝。同质岩石表面固着生物的种类与数量低于异质性的岩石表面。清除岩石表面的消费者后叶状藻类与其它固着无脊椎动物的种数就超过皮壳状藻类     

Human disturbance and trophic status changes in Crystal Lake, McHenry County, Illinois, USA

The paleolimnology (sediment chemistry, ²¹⁰Pb dating, pollen, and diatoms) of Crystal Lake, McHenry County, Illinois, USA was studied to investigate the impact of European settlement on lake trophic status. Pollen clearly indicates a vegetational shift from Quercus dominance to Ambrosia. ²¹⁰Pb dating suggests that the Ambrosia rise likely occurs around the 1840's, which is consistent with historical records on the European settlement in this area. Coincident with the vegetational shifts, several diatom species, Cyclotella meneghiniana, Fragilaria crotenensis, Asterionella formosa and Tabellaria fenestrata, all increase while C. comta decreases after the settlement. However, C. comta and Aulacoseira ambigua, two dominant species, remain abundant throughout the entire core. Their relative abundances at the surface sediments reach presettlement levels. It is hypothesized that Crystal Lake, a glacial lake rich in CaCO₃, may have been able to assimilate increases of phosphorus by coprecipitating phosphorus with CaCO₃. Such a 'buffering mechanism may be responsible for the lake's resistance to trophic changes or recovery following disturbance.     

“海参-对虾”混养海水池塘的食物网结构及营养层级研究

The food sources of aquacultured Apostichopus japonicus and the trophic levels of organisms in a sea cucumber(A. japonicus) and prawn(Penaeus japonica) polyculture system in a saltwater pond in Zhuanghe, Liaoning Province were examined using carbon and nitrogen stable isotopes. Across organisms, δ13C ranged from(–25.47±0.20)‰ to(–16.48±0.17)‰(mean±SD), and δ15N ranged from(4.23±0.49)‰ to(12.44±0.09)‰. The δ13C and δ15N contents of A. japonicus, P. japonica and Fenneropenaeus chinensis were comparatively higher than those of other organisms. Values of δ13C and δ15N revealed that P. japonica, Hemigrapsus sanguineus and Neomysis japonica comprised the largest component of the diet of A. japonicus. The mean trophic level of the organisms in this saltwater pond polyculture system was(2.75±0.08). P. japonica, A. japonicus, F. chinensis,Synechogobius hasta and Neomysis japonica were in the 3rd trophic level(2–3); jellyfish, H. sanguineus and zooplankton were in the 2nd trophic level(1–2); and Enteromorpha prolifera, benthic microalgae, periphyton and suspended matter primarily consisting of phytoplankton, bacteria and humus were in the primary trophic level(0–1).     

数据稀缺生态系统中多种类质量谱模型的构建

多种类生态模型已经被广泛应用于渔业活动影响应预测和管理措施效果评估。质量谱模型是一种基于生理过程构建的生态模型,该模型为描述鱼类群落在个体摄食变异和随个体发生的生态位迁移提供了一个可行的方法。尽管生态模型在增进生态系统认识上具有重要意义,其应用在数据稀缺的渔业中受到很大限制。作为实践基于生态系统渔业管理(EBFM)的第一步,本研究构建了海州湾鱼类群落的质量谱模型。本研究详述了数据收集和模型参数化的过程,以促进该模型在数据稀缺的生态系统中未来的应用。作为一个范例,研究展示了不同捕捞努力量对生态系统的影响,并采用一套生态指标监测其动态。群落生物量、多样性指数、W指数,大鱼指数(LFI),平均体重和群落质量谱斜率对捕捞压力的响应呈非线性,最大的捕捞强度并非总是对鱼类群落产生最强的影响。本文强调了构建谱模型在生态研究中的的价值和可行性,并讨论了模型的局限性和改进的可能。本研究旨在促进质量谱模型的广泛应用以更好地支持基于生态系统的渔业管理。     

Stable isotope analysis of consumer food webs indicates ecosystem recovery following prolonged drought in a subtropical estuarine lake

Assessing changes in food-web structure provides a useful monitoring tool for gauging the resilience of ecosystems in the face of climatic impacts. We consider the ecological resilience of a large estuarine lake (St Lucia Estuary, South Africa) in the wake of an extreme climatic event (prolonged drought). Using carbon and nitrogen stable isotopes, food-web structure was assessed at five sites across the estuary during the winter and spring of 2013. Sampling occurred approximately three years after heavy rains flooded the system and returned it to a relatively diluted state following an almost decade-long drought that decimated food webs in the upper parts of the estuary due to hypersalinity effects. Comparisons of niche width and variance of consumer food webs among sites revealed a general homogenisation of food webs across the entire system, contrasting with the spatial differentiation of food webs documented during the drought phase. Our results indicate that the estuary is able to maintain ecological resilience at the whole-system level in the face of an extreme drought. This is likely facilitated by source pools of species residing in the relatively stable lower estuary, which are able to rapidly recolonise areas denuded by drought in the upper estuary.     

Water Flow, Trophic Depletion, and Benthic Macrofauna Impoverishment in a Submarine Cave from the Western Mediterranean

Abstract. Biotic zonation and severe impoverishment of benthic macrofauna are two of the most conspicuous features of submarine caves. The prevailing explanation assumes trophic depletion caused by reduction of water flow. However, no isolation of water was found in the studied Catalan submarine cave, even in the wall microlayer. Fluorescein diffusion was so fast that it was detectable everywhere in the cave already only a few minutes after the injection. The rate of dissolution of plaster spheres was even greater in the cave than in a nearby tunnel – without benthic macrofauna impoverishment – showing a considerable water flow. The oxygen concentration of water in dialysis bags placed at varying distances from the cave walls showed that no wall microlayer gradients were present.
Biochemical gradients did not indicate any decrease in food supply. Although photosynthetic pigment concentration generally decreased inside the cave, and although the gradients were not linear but formed different patterns throughout the cave, the BOD₅, the POM, the C:N ratio, the [³H]-thymidine incorporation rate, and the ETS activity were higher in the inner part of the cave. There was an accumulation of detritic material and bacteria in the inner parts that constitute a plausible food supply for benthic macrofauna.
If neither water motion nor food supply can be invoked, research into the causes of zonation and disappearence of benthic macrofauna is proposed to be carried out on biotic interactions and behavioural processes.     

The Diets in Four Pacific Tube Blennies (Acanthemblemaria: Chaenopsidae): Lack of Ecological Divergence in Syntopic Species

Abstract. The diets of three syntopic Gulf of California Acanthemblemaria (A. balanorum, A. crock-eri and A. macrospilus) and A. castroi from the Galapagos Island are nearly uniformly composed of harpacticoid copepods and other small benthic-vagile or planktonic crustaceans. On occasion, large prey items such as crabs or other small fishes are taken. HORN'S index of niche overlap indicates that the three syntopic Acanthemblemaria are not separated along the food resource utilization axis. Slight variations in diets among the syntopic species seem to be related to differences in degree of microhabitat specialization.     

Reference and current Trophic Level Index of New Zealand lakes: benchmarks to inform lake management and assessment

ABSTRACT

Knowledge of trophic status is fundamental to understanding the condition and function of lake ecosystems. We developed regression models to predict chlorophyll a concentrations (chl a) in New Zealand lakes for reference and current states, based on an existing dataset of total nitrogen (TN) and total phosphorus (TP) concentrations for 1031 lakes. Models were then developed to predict Secchi depth based on chl a and a sediment resuspension term applicable to shallow lakes. Estimates of all four Trophic Level Index (TLI) variables (chl a, TN, TP and Secchi depth) were analysed to estimate reference and current state TLI for the nationally representative sample of 1031 lakes. There was a trend of eutrophication between reference and current states, with systematic differences among lake geomorphic types. Mean chl a increased 3.5-fold (2.42?mg?m^?3 vs. 8.32?mg?m^?3) and mean Secchi depth decreased (indicating lower clarity) by approximately one-third (9.62?m vs. 6.48?m) between reference and current states. On average, TLI increased by 0.67, with the TLI increase >1 in approximately one-third (31%) of lakes. This study informs the status of lake ecosystems in NZ and provides benchmarks to guide management and assessment.