Trophic efficiency of the planktonic food web in a coastal ecosystem dominated by Phaeocystis colonies     

V. Rousseau  S. Becquevort  J. -Y. Parent  S. Gasparini  M. -H. Daro  M. Tackx  C. Lancelot 《Journal of Sea Research》2000,43(3-4)

The trophic efficiency of the planktonic food web in the Phaeocystis-dominated ecosystem of the Belgian coastal waters was inferred from the analysis of the carbon flow network of the planktonic system subdivided into its different trophodynamic groups. A carbon budget was constructed on the basis of process-level field experiments conducted during the spring bloom period of 1998. Biomass and major metabolic activities of auto- and heterotrophic planktonic communities (primary production, bacterial production, nanoproto-, micro- and mesozooplankton feeding activities) were determined in nine field assemblages collected during spring at reference station 330. In 1998, the phytoplankton spring flowering was characterised by a moderate diatom bloom followed by a massive Phaeocystis colony bloom. Phaeocystis colonies, contributing 70% to the net primary production, escaped the linear food chain while the early spring diatom production supplied 74% of the mesozooplankton carbon uptake. The rest of mesozooplankton food requirement was, at the time of the Phaeocystis colony bloom, partially fulfilled by microzooplankton. Only one-third of the microzooplankton production, however, was controlled by mesozooplankton grazing pressure. Ungrazed Phaeocystis colonies were stimulating the establishment of a very active microbial network. On the one hand, the release of free-living cells from ungrazed colonies has been shown to stimulate the growth of microzooplankton, which was controlling 97% of the nanophytoplankton production. On the other hand, the disruption of ungrazed Phaeocystis colonies supplied the water column with large amounts of dissolved organic matter available for planktonic bacteria. The budget calculation suggests that ungrazed colonies contributed up to 60% to the bacterial carbon demand, while alternative sources (exudation, zooplankton egestion and lysis of other organisms) provided some 30% of bacterial carbon requirements. This suggests that the spring carbon demand of planktonic bacteria was satisfied largely by autogenic production. The trophic efficiency was defined as the ratio between mesozooplankton grazing on a given source and food production. In spite of its major contribution to mesozooplankton feeding, the trophic efficiency of the linear food chain, restricted to the grazing on diatoms, represented only 5.6% of the available net primary production. The trophic efficiency of the microbial food chain, the ratio between mesozooplankton grazing on microzooplankton and the resource inflow (the bacterial carbon demand plus the nanophytoplankton production) amounted to only 1.6%. These low trophic efficiencies together with the potential contribution of ungrazed Phaeocystis-derived production to the bacterial carbon demand suggest that during spring 1998 most of the Phaeocystis-derived production in the Belgian coastal area was remineralised in the water column.  相似文献   

Channel‐planform evolution in four rivers of Olympic National Park,Washington, USA: the roles of physical drivers and trophic cascades          下载免费PDF全文

Amy E. East  Kurt J. Jenkins  Patricia J. Happe  Jennifer A. Bountry  Timothy J. Beechie  Mark C. Mastin  Joel B. Sankey  Timothy J. Randle 《地球表面变化过程与地形》2017,42(7):1011-1032

Identifying the relative contributions of physical and ecological processes to channel evolution remains a substantial challenge in fluvial geomorphology. We use a 74‐year aerial photographic record of the Hoh, Queets, Quinault, and Elwha Rivers, Olympic National Park, Washington, USA, to investigate whether physical or trophic‐cascade‐driven ecological factors – excessive elk impacts after wolves were extirpated a century ago – are the dominant drivers of channel planform in these gravel‐bed rivers. We find that channel width and braiding show strong relationships with recent flood history. All four rivers widened significantly after having been relatively narrow in the 1970s, consistent with increased flood activity since then. Channel planform also reflects sediment‐supply changes, evident from landslide response on the Elwha River. We surmise that the Hoh River, which shows a multi‐decadal trend toward greater braiding, is adjusting to increased sediment supply associated with rapid glacial retreat. These rivers demonstrate transmission of climatic signals through relatively short sediment‐routing systems that lack substantial buffering by sediment storage. Legacy effects of anthropogenic modification likely also affect the Quinault River planform. We infer no correspondence between channel evolution and elk abundance, suggesting that trophic‐cascade effects in this setting are subsidiary to physical controls on channel morphology. Our findings differ from previous interpretations of Olympic National Park fluvial dynamics and contrast with the classic example of Yellowstone National Park, where legacy effects of elk overuse are apparent in channel morphology; we attribute these differences to hydrologic regime and large‐wood availability. Published 2016. This article is a U.S. Government work and is in the public domain in the USA  相似文献   

贵阳市百花湖近10年(2009-2018年)的水质时空变化     

贺康康  王敬富  李玉麟  杨小红  曾华献  陈敬安 《湖泊科学》2021,33(2):494-506

百花湖是贵阳市重要的城市饮用水源地,并且近年来经常发生水质异常现象.本文利用2009-2018年百花湖长时间序列的监测数据,采用综合营养状态指数法和Pearson相关性分析,研究了百花湖10年间的水质变化特征和影响因素.结果表明：1）库区叶绿素a（Chl.a）、总磷（TP）、总氮（TN）、高锰酸盐指数（COD_Mn）和透明度（SD）的浓度范围分别是3.43~39.72 mg/m³、0.034~0.115 mg/L、1.200~2.759 mg/L、1.41~5.51 mg/L和0.75~2.07 m,且高氮磷比（12~63）表明百花湖是磷限制型.2）在空间上,TP、TN、氨氮、COD_Mn和Chl.a浓度沿水体流向逐渐降低,SD呈相反变化趋势.3）10年来,百花湖水质由Ⅳ类转变为Ⅲ类,综合营养状态由轻度富营养化状态转变为中营养状态,水质整体向好.4）入库支流是影响百花湖库区水质的主要因素,长期以来,东门桥河、南门河水质TP和TN等超标严重,给库区水质稳定达标带来威胁.5）百花湖Chl.a浓度与气温、水位、风速和TP等指标显著相关,是受水文、气象及营养盐因素的综合控制.未来在百花湖水环境保护治理过程中,应加大对东门桥河、南门河等重点支流的污染治理,加强对水动力学、气候变化等水文气象因素影响库区水质（藻类水华）的机制研究.  相似文献   

Ontogenetic shifts in feeding habits of orangemouth weakfish (Cynoscion xanthulus): From estuarine benthic feeder to marine nektivore top predator     

Víctor M. Muro-Torres  Felipe Amezcua  Lucinda Green  Jorge Payan  Eduardo F. Balart-Páez  Felipe Amezcua-Linares 《Marine Ecology》2023,44(1):e12735

Orangemouth weakfish is a highly important commercial and game fish species in the Tropical Eastern Pacific. However, studies assessing changes in its trophic ecology relevant to size, habitat (estuarine or marine), sex, and season are non-existent. We assessed its feeding habits and trophic position (TP) according to the aforementioned factors. Its dietary breadth was composed of 33 types of prey. The feeding habits and isotopic values (δ¹⁵N and δ¹³C) registered differences between sizes and habitat, indicating ontogenetic changes in habitat as well as TP, as small organisms (TP 3.1) inhabited the estuarine area, feeding on benthic and demersal organisms, whilst large individuals (TP 4.1) were found in the marine environment, preying on nektonic fauna. No differences were found according to sex or season. The isotopic niche showed that the different sizes of this species are generalist consumers with a clear separation between them and between habitats, as estuarine juvenile and preadult organisms have a larger isotopic niche than adult marine organisms, being an opportunist tertiary estuarine consumers during their early stages, and a top marine predator during the adult phase.  相似文献   

贫、富营养湖泊中苦草的形态解剖结构比较   总被引：4，自引：2，他引：2  

王永平  秦伯强 《湖泊科学》2011,23(1):56-60

比较了生长于贫营养的大溪水库(江苏)和富营养的太湖梅梁湾苦草的根系形态性状特征和叶片与匍匐苇的解剖结构差异,结果表明:生长于贫营养状态的大溪水库中的苦草根系形态性状的总根长、表面积、截面积、体积、平均直径和总分叉数等特征参数都显著高于生长于富营养状态的太湖梅梁湾的苦草.大溪水库的苦草叶片表面光洁,受附着生物影响明显较来...  相似文献   

汉江流域黑竹冲河五种优势摇蚊的周年生产量及营养基础分析   总被引：3，自引：0，他引：3  

闫云君  李晓宇 《湖泊科学》2006,18(2):163-171

2003年6月至2004年6月间对汉江流域2级河流——黑竹冲河大型底栖动物群落优势种类的生产力进行为期一周年的调查研究,其中主要优势摇蚊中粗腹摇蚊(Pentaneura sp．)和多足摇蚊(Polypedilum sp.)的生活史为一年三代, 小摇蚊(Microtendipes sp．)和帕摇蚊(Pagastia sp．)为一年两代,刺突摇蚊(Chaetocladius sp．)为一年一代．粗腹摇蚊种群生物量和多度在一年中出现两次峰值,多足摇蚊则出现三次,小摇蚊在6月份达到最大峰值,刺突摇蚊在1月份达到最大峰值,帕摇蚊在10月份和次年1月份分别达到次峰值和主峰值．采用龄期频率法(instar-frequency method)测算的周年生产量(鲜重)分别为:粗腹摇蚊,19．9233g/(m2·a),P/B为8．7;多足摇蚊,7．2177g/(m2·a),P/B为8．1;小摇蚊, 0．8996g/(m2·a),P/B为6．0;刺突摇蚊,3．2533 g／(m2·a),P／B为3．4;帕摇蚊,8．5132g/(m2·a),P／B为8．4．除粗腹摇蚊外,其它四种摇蚊的前肠内含物中无形态碎屑所占比例均高于90％,对生产量的贡献率达到77％-96％;粗腹摇蚊的动物性食物所占比例达到14．73％,其对生产量的贡献率高达46．04％．  相似文献   

水体富营养化改善过程中浮游植物群落对非生物环境因子的响应:以武汉东湖为例   总被引：2，自引：0，他引：2  

赵思琪  范垚城  代嫣然  王飞华  梁威 《湖泊科学》2019,31(5):1310-1319

针对武汉东湖存在营养状态梯度的5个子湖（郭郑湖、汤菱湖、团湖、庙湖、水果湖）,结合"空间换时间"理论,研究湖泊富营养状况改善过程中浮游植物群落对环境因子的响应.全年调查期间,各子湖综合营养状态指数分布范围为45.4~76.8,浮游植物密度及生物量变化范围分别为2.03×10⁶~245×10⁶ cells/L和0.819~19.9 mg/L.冗余分析结果显示,浮游植物的物种分布与水温、总氮、透明度、总溶解性固体、氨氮呈显著相关.采用多元逐步回归分析构建浮游植物密度、生物量与环境因子之间的最优响应方程,结果显示,总氮、水温是影响浮游植物密度的主要因子;对于浮游植物生物量而言,总磷、总氮浓度降低能够降低浮游植物生物量.通过对富营养程度改善进程中浮游植物群落组成的动态变化进行分析,发现浮游植物密度及生物量显著下降,但物种组成及生物多样性并未发生明显转变.此外,浮游植物物种多样性与水体富营养水平梯度并不呈现简单的线性相关.因此,在对富营养化湖泊进行修复时,应制定短期修复与长期维护双重措施,同时应重视生物多样性的重建,进而达到理想的修复效果.  相似文献   

贵州红枫湖近10年来(2009-2018年)水质变化及影响因素     

曾华献  王敬富  李玉麟  陈敬安  金祖雪  贺康康  杨小红 《湖泊科学》2020,32(3):676-687

为更好地研究贵州红枫湖的水质变化情况,本文利用贵阳市两湖一库环境保护监测站2009-2018年对红枫湖7个代表性监测点的营养盐、叶绿素a（Chl.a）浓度和水温、气温、透明度、降雨量等水文气象条件逐月监测数据,分析红枫湖10年间水体营养盐和Chl.a浓度以及部分水文气象条件的变化趋势.运用综合营养状态指数（TLI）对红枫湖营养状态进行评价,采用Pearson相关系数法统计分析10年内Chl.a浓度与总磷（TP）、总氮（TN）等水化学组成及水位、气温等水文气象条件的相关性.结果表明,2009-2018年红枫湖水体逐月TN浓度有较大波动（0.56~2.80 mg/L）,春、夏季高于秋、冬季;水体逐月TP浓度为0.016~0.103 mg/L,夏季略高于冬季;逐月氨氮（NH₃-N）浓度为0.007~0.71 mg/L,春季 > 冬季 > 秋季 > 夏季;水体逐月Chl.a浓度呈季节性波动（0.8~38.9 mg/m³）,夏季 > 春季 > 秋季 > 冬季,年内先上升后下降.TP、NH₃-N、Chl.a浓度整体呈下降趋势,10年间水质有很大改善.经计算红枫湖在这10年间处于中营养状态至轻度富营养状态,且营养状态指数呈逐年下降趋势,夏季TLI明显高于其他季节.统计分析表明,红枫湖水体Chl.a浓度与高锰酸盐指数、NH₃-N、TP浓度均呈显著正相关,与氮磷比呈显著负相关,与水温、pH、降雨量、气温、日照时数呈显著正相关,与透明度、气压呈显著负相关,与水位、湿度、风速无显著相关关系.表明这10年来红枫湖水体Chl.a浓度不仅受营养盐浓度控制,很大程度上还受控于气象和水文条件.  相似文献   

Effect of temperature on an alga‐grazer trophic transfer: A dual stable isotope (13C, 15N) labeling experiment          下载免费PDF全文

Erwann Legrand  Sophie Martin  Cédric Leroux  Pascal Riera 《Marine Ecology》2018,39(2)

In this study, we examined the impact of temperature on the carbon and nitrogen trophic transfers from a macroalga to a macro‐grazer by the use of dual ¹³C‐ and ¹⁵N‐labeling. Using an experimental approach in mesocosms, individuals of the urchin Psammechinus miliaris were maintained for 1 month at 17°C (mean summer temperature in the Bay of Brest) and at 20°C (maximum summer temperature) and fed with ¹³C‐ and ¹⁵N‐labeled Solieria chordalis. The results showed that the urchins’ ¹³C uptake was 0.30 µg¹³C g dry weight (DW)^?1 at 17°C and 0.14 µg¹³C g DW^?1 at 20°C at the end of the experiment. The lower uptake at the higher temperature may be attributed to a decrease in metabolic activity at 20°C, involving lower feeding and/or respiration rates. Conversely, no significant effect of temperature was detected on ¹⁵N uptake. At the end of the experiment, the urchins’ ¹⁵N uptake was 0.04 µg¹⁵N g DW^?1 at 17°C and 0.03 µg¹⁵N g DW^?1 at 20°C. This suggests that temperature may affect carbon and nitrogen trophic fluxes differently. The use of dual isotope labeling offers interesting prospects and needs to be further extended in order to better understand trophic interactions in marine communities and the consequences of current environmental changes, such as global warming.  相似文献   

Annual pattern of zooplankton communities and their environmental response in a subtropical maritime channel system in the northern Bay of Bengal, Bangladesh     

ABDULLAH Al Mamun  ALAM Md. Didarul  AKHTAR Aysh  XU Henglong  ISLAM Md. Shafiqul  MUSTAFA KAMAL Abu Hen  UDDIN M Muslem  ALAM Md. Wahidul 《海洋学报(英文版)》2018,37(8):65-73

Zooplankton plays an important role in aquatic food webs by fluxing of energy from primary producer to subsequent trophic levels in the food chain. The annual pattern of zooplankton communities and potential environmental drivers were studied in the Kohelia channel, Bangladesh from summer 2014 to spring 2015. Samples were collected using net at a depth of 1 m. A total of 32 species belonged to 18 orders, 27 families and 15 taxonomic groups were identified. Of these species, 22 distributed in all four seasons of which 8 were dominant and highly contributing to the total communities. Species number peaked in summer next to winter and fall in spring while maximum abundance was in summer and minimum in spring. Multivariate analyses showed that there was a clear annual pattern in the zooplankton communities. Species diversity and evenness peaked in spring but fall in autumn while the high value of species richness was found in winter. Biological-environmental best matching (BIO-ENV) analyses conformed that community pattern of zooplankton was mainly driven by transparency salinity, and temperature individually or combined with water nutrients. These results demonstrate that annual pattern of the zooplankton community shaped by channel environmental factors in subtropical channel ecosystems, thus might be used for community-based subtropical coastal water bioassessment.  相似文献