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91.
A large-scale enclosure experiment for lake restoration was carried out in Lake Wuli, a northern bay of shallow and eutrophic Lake Taihu in China. The large enclosure with an area of 10 ha was set up in the littoral zone and was bordered by waterproof fabric which did not cover the sediments. Multiple approaches were used and included fish removal, piscivorous fish stocking, shoreline reconstruction, aquatic macrophyte planting, benthic macro-animal stocking, and silver carp cultivation in pens for reduction of cyanobacteria. The results showed that the coverage of aquatic macrophytes increased from 0% to 45.7%. Mean concentrations of TN and TP inside the enclosure from May 2004 to May 2008 were 22.2% and 26.0% of those outside, respectively. Secchi depth was 0.40 m outside the enclosures and 0.75 m inside. However, responses of phytoplankton to the restoration project lagged behind improvement of water quality and reestablishment of aquatic plants. The phytoplankton biomass gradually decreased after the third year of the restoration. Stocking piscivorous fish and planting submerged macrophytes could not increase zooplankton biomass and enhance graze pressure on phytoplankton, most likely due to high omnivorous fish density and lower nutrition inside the enclosure. Higher grazing pressure of zooplankton on phytoplankton was observed in May and October every year. Zooplankton to phytoplankton biomass ratios were significantly negatively correlated with phytoplankton biomass outside (r = −0.440, p < 0.01) and inside the enclosure (r = −0.336, p < 0.05) from February 2004 to March 2007. Therefore, phytoplankton biomass inside and outside the enclosure was lower in May and October. Higher grazing pressure of zooplankton on phytoplankton in spring may result in occurrence of the clear-water phase that facilitated growth of submerged macrophytes in the littoral in Lake Wuli, and a clear-water state and improved water quality would likely be sustained throughout the year after reestablishment of submerged macrophytes. 相似文献
92.
Dennis Trolle Guangwei Zhu David Hamilton Liancong Luo Chris McBride Lu Zhang 《Hydrobiologia》2009,627(1):31-44
Distinct horizontal water column concentration gradients of nutrients and chlorophyll a (Chl a) occur within large, shallow, eutrophic Lake Taihu, China. Concentrations are high in the north, where some of the major
polluted tributaries enter the lake, and relatively low in the south, where macrophytes generally are abundant. It is not
clear, however, whether these water column concentration gradients are similarly reflected in spatial heterogeneity of nutrient
concentrations within the bottom sediments. The main objective of this study was therefore to test if horizontal and vertical
variations in the phosphorus and nitrogen content in bottom sediments of Lake Taihu are significantly related to (1) horizontal
variations in overlying water column nutrient concentrations and (2) other sediment geochemical constituents. We measured
the concentration of total phosphorus (TP) and total nitrogen (TN) in surficial sediments (0–2 cm) and TP, TN and Chl a concentrations in water column samples, collected from 32 sites in 2005. In 2006 sediment, TP, TN, carbon, iron and manganese
concentrations were measured vertically at 2 cm intervals, extending to a depth of approximately 20 cm, at an additional eight
sites. Linear correlation analysis revealed that surficial sediment TP concentrations across the 32 stations were related
significantly, though weakly, to annual mean water column concentrations of TP, TN as well as Chl a. Correlations of surficial sediment TN with water column variables were, however, not significant (P > 0.05). Amongst the geochemical variables tested, the vertical variability of sediment TP concentrations was most strongly
related to sediment manganese and carbon concentrations. A multiple stepwise linear regression revealed that the combination
of sediment manganese and carbon concentrations explained 91% of the horizontal variability in sediment TP concentrations
and 65% of the vertical variability.
Handling editor: Luigi Naselli-Flores 相似文献
93.
Site-specific chlorophyll reference conditions for lakes in Northern and Western Europe 总被引:1,自引:1,他引:0
Laurence Carvalho Angelo G. Solimini Geoff Phillips Olli-Pekka Pietiläinen Jannicke Moe Ana Cristina Cardoso Anne Lyche Solheim Ingmar Ott Martin Søndergaard Gianni Tartari Seppo Rekolainen 《Hydrobiologia》2009,633(1):59-66
The Water Framework Directive (WFD) requires EU Member States to assess the “ecological status” of surface waters. As a component of ecological status, many European countries are developing a classification scheme for chlorophyll concentrations as a measure of phytoplankton biomass. The chlorophyll classification must be based on the degree of divergence of a water body from an appropriate baseline or ‘reference condition’. This article describes the development of a series of regression models for predicting reference chlorophyll concentrations on a site-specific basis. For model development, a large dataset of European lakes considered to be in reference condition, 466 lakes in total, was assembled. Data were included from 12 European countries, but lakes from Northern and Western Europe dominated and made up 92% of all reference lakes. Data have been collated on chlorophyll concentration, altitude, mean depth, alkalinity, humic type, surface area and geographical region. Regression models were developed for estimating site-specific reference chlorophyll concentrations from significant predictor ‘typology’ variables. Reference chlorophyll concentrations were found to vary along a number of environmental gradients. Concentrations increased with colour and alkalinity and decreased with lake depth and altitude. Forward selection was used to identify independent explanatory variables in regression models for predicting site-specific reference chlorophyll concentrations. Depth was selected as an explanatory variable in all models. Alkalinity was included in models for low colour and humic lakes and altitude was included in models for low colour and very humic lakes. Uncertainty in the models was quite high and arises from errors in the data used to develop the models (including natural temporal and spatial variability in data) and also from additional explanatory variables not considered in the models, particularly nutrient concentrations, retention time and grazing. Despite these uncertainties, site-specific reference conditions are still recommended in preference to type-specific reference conditions, as they use the individual characteristics of a site known to influence phytoplankton biomass, rather than adopt standards set to generally represent a large population of lakes of a particular type. For this reason, site-specific reference conditions should result in reduced error in ecological status classifications, particularly for lakes close to typology boundaries. 相似文献
94.
Wolfgang Nikolaus Probst Stefan Stoll Lars Peters Philipp Fischer Reiner Eckmann 《Hydrobiologia》2009,632(1):211-224
In Lake Constance, Eurasian bream Abramis brama (L.) spawn in very shallow littoral areas by the beginning of May. They attach their adhesive eggs to pebble and cobble substratum
at <40 cm depth. Increasing water levels before spawning inundate bare substratum to which bream eggs may attach better than
to deeper substratum covered by epilithon. Consequently, the water level increase prior to spawning should determine the amount
of pristine spawning substratum available to bream and thus influence their breeding success. In order to test this hypothesis,
the influence of hydrology and climate on the abundance of age-0 bream was combined with the results from field investigations
on the egg survival and abundance of age-0 bream. A strong positive correlation between the mean water level increase during
the spawning season of bream (April–May) and the abundance of juvenile bream was found. In contrast, the absolute water level
during spawning and during the nursery stage in summer, the cumulative temperature during the egg, larval and juvenile stages
and two North Atlantic Oscillation (NAO) indices did not affect the abundance of juvenile bream. The field investigations
confirmed that bream eggs attach better to and have higher survival rates on bare substratum than on substratum with epilithon
cover. Accordingly, eggs within a spawning habitat of bream were most abundant between 10 and 20 cm depth, where the epilithon
cover was lower than at depths exceeding 30 cm. The results of this study confirm an adverse influence of epilithon cover
on the attachment and subsequent survival of bream eggs and emphasize the importance of spring inundations for the successful
breeding of the bream.
Handling editor: J. A. Cambray 相似文献
95.
Sébastien Personnic Isabelle Domaizon Ursula Dorigo Lyria Berdjeb Stéphan Jacquet 《Hydrobiologia》2009,627(1):99-116
Flow cytometry (FCM) was used to assess microbial community abundances and patterns in three natural, large and deep peri-alpine
hydrosystems, i.e., lakes Annecy (oligotrophic), Bourget, and Geneva (mesotrophic). Picocyanobacteria, small eukaryotic autotrophs,
heterotrophic prokaryotes, and viruses were studied in the 0–50 m surface layers to highlight the impact of both physical
and chemical parameters as well as possible biotic interactions on the functioning of microbial communities. Some specificities
were recorded according to the trophic status of each ecosystem such as the higher number of viruses and heterotrophic bacteria
in mesotrophic environments (i.e., Lakes Geneva and Bourget) or the higher abundance of picocyanobacteria in the oligotrophic
Lake Annecy. However, both seasonal (temperature) and spatial (depth) variations were comparatively more important than the
trophic status in driving the microbial communities’ abundances in these three lakes, as revealed by principal component analysis
(PCA). A strong viral termination of the heterotrophic bacterial blooms could be observed in autumn for each lake, in parallel
to the mixing of the upper lit layers. As virus to bacteria ratio (VBR) was indeed very high at this period with values varying
between 87 and 114, such important relationships between viruses and bacteria were likely. The magnitudes of seasonal variations
in VBR, with the highest values ever reported so far, were largely greater than the magnitude of theoretical variations due
to the trophic status, suggesting also a strong seasonality in virioplankton production associated to prokaryotic dynamics.
FCM analyses allowed discriminating several viral groups. Virus-Like Particles group 1 (VLP1) and group 2 (VLP2) were always
observed and significantly correlated to bacteria for the former and chlorophyll a and picocyanobacteria for the latter, suggesting that most of VLP1 and VLP2 could be bacteriophages and cyanophages, respectively.
On the basis of these results, new ways of investigation emerge concerning the study of relationships between specific picoplanktonic
groups; and overall these results provide new evidence of the necessity to consider further viruses for a better understanding
of lake plankton ecology.
Handling editor: Luigi Naselli-Flores 相似文献
96.
Lake Victoria, the world's largest tropical freshwater lake, is an important resource, ecologically and economically. THg distribution in the northern parts of the lake are not well known, so to answer this gap, patterns in total mercury (THg) in water, soil and two dated sediment cores from northern Lake Victoria were determined. Water THg concentrations ranged from 0.7 to 5.8 ng/L, and there were no apparent differences observed between Napoleon and Winam Gulfs. Two precipitation samples had Hg concentrations of 7 and 31 ng/L. Surface soil samples collected from various agricultural sites around Jinja, Napoleon Gulf, have THg concentrations between 12.7 and 48.4 ng/g dry weight; they were correlated with organic carbon, total phosphorus and % clay. A near-shore core taken in Itome Bay in Napoleon Gulf, and an offshore core collected from the deepest part of the lake had similar THg concentrations and profiles (78 to 458 ng/g dry weight). The increase in THg concentration in the profiles of both cores began around 1960 and peaked around 1980. The similar sedimentary THg profiles and fluxes in the cores suggest that the THg sources to L. Victoria are primarily atmospheric, with some erosion inputs, and that equatorial African ecosystems are not exempt from the global increase in baseline THg concentrations. 相似文献
97.
98.
99.
洞庭湖黄颡鱼生物学特性 总被引:17,自引:1,他引:16
20 0 0年 3~ 5月 ,收集洞庭湖黄颡鱼 1 5 5尾 ,对其生物学特性进行研究。结果表明 ,黄颡鱼鳍式为D Ⅱ ,2~ 6,A 1 9~ 2 2 ,主要以虾、小型底栖鱼类、软体动物为食。体重 (W :g)与体长 (L :cm)关系为 :W =7 9861× 1 0 -2 L2 4471;体长生长方程为Lt=2 3 0 482 [1 -e-0 592 8(t+ 0 13 54) ];体重生长方程为 :Wt=3 68 3 90 9[1 -e-0 592 8(t+ 0 13 54) ]3 。生长速度以 1~ 2龄最快 ,以后逐步减慢 ,绝对繁殖力为 1 3 45~ 72 0 8粒 ,相对繁殖力为 48~ 78 3粒 g。繁殖力系数F =1 1 5 4977L1 453 9;性成熟年龄为 1 + 龄 ,自然性成熟雌鱼W =3 0 67g,L =1 0 2 9cm ,黄颡鱼人工养殖宜用 2年生产周期。 相似文献
100.
吴县市露采矿区生态重建与环太湖地区生态旅游模式的契合 总被引:3,自引:1,他引:2
从景观生态学的定义入手,结合吴县市环太湖地区露采矿区的环境问题现状,提出了吴县市生态重建的基本原则和方法。基于每个废矿区都是一个脆弱的生态系统,在其恢复过程中,首先要在宏观上合理安排生态重建景观格局的规划及布局,然后在微观上创造出合适的生态条件服务于整个生态系统的恢复与重建。同时以生态重建后的矿区所要具有的三大基本功能:生物生产、环境服务、文化支持为依托,构建了生态功能系统图及生态功能区相互关联图。生物生产功能主要是针对农业利用,环境服务是对用于旅游、娱乐、绿化用地的露采矿区,文化支持则是针对作为建筑用地的废弃地,其城镇及居民点用地是人类聚集场所,支撑了工矿企业、旅游商贸服务业及整个城市体系的运行。最后总结了环境生态重建后所产生的环境、生态及经济效益。 相似文献