专家解读达赉湖

在“体验”和“对话”中,我们请到了两位专家参与其中,为大家借读保护区的意义、价值,讲述生态知识。     

来自湖畔的忧虑

在当地蒙古族牧民的守护下,达里湖千万年来充当着候鸟驿站以及繁育家园。然而,它们却不知道维系它们生命的这个天堂正面临干涸的危机。当太阳渐渐西沉,温暖柔和的斜光撒满了草原,达里湖迎来了一天中最为安详和动人的时刻。湖岸边一丛丛的芨芨草变成了橘红色,逆光看去,草叶的边缘、饮水的牛只、挥着鞭子的牧人,全都披上了毛茸茸的金色光圈。等太阳最后从火山锥后面隐去时,天空中布满了五彩的晚霞,倒映在宽阔的湖面上,水天一色。就在这样的天色中,牛群慢吞吞地往家走去,被霞光染成了粉     

Bacterioplankton response to eutrophication in Lake Ladoga

Myriophyllum sibiricum Komarov, an aquatic dicotyledonous macrophyte with a north temperate distribution, was assessed for use in a new bioassay to determine the effect of pesticides, agricultural runoff and municipal waste upon non-target aquatic macrophytes. An axenic culturing system was developed for which an optimal growth medium is required before a bioassay will be reliable. Five media (Murashige and Skoog, Hoagland's, Gaudet's, modified Andrew's, and Hard Water media), commonly used for aquatic plant culturing, were compared to determine the effect on M. sibiricum growth and development. Morphological endpoints for the assay included shoot length, total root length and number, fresh weight and plant area. Membrane integrity, chlorophyll a, chlorophyll b and carotenoid content were the physiological endpoints examined. Based upon these criteria, the modified Andrew's medium at a pH of 5.8, without the addition of a buffer was chosen as a medium which supported rapid and consistent development of M. sibiricum during the two week assay period.     

A Model to Predict Lake Water Colour

This study is an attempt to quantitatively determine variables of significance for predicting colour in small glacial lakes. Lake colour is an important variable in many lake ecological contexts. The data emanate from two extensive data-sets from Sweden, one of which concerns 1456 lakes, and the other 91 more well-suited lakes. Four year average values of lake colour were compared to catchment and morphometric parameters to help identify the processes which influence variability in colour between lakes. Various hypotheses concerning the factors regulating colour in lakes were formulated and tested. Various statistical tests were used to separate random influences from causal influences. Those “map parameters” with the most significant influence on colour were the theoretical lake water retention time, the percent of rocks, lakes and mires of the drainage area, the ratio between lake area and drainage area and the lake mean depth. Each model parameter provides only a limited explanation (statistical) of the variability in colour between lakes. The predictability of colour by these models can not be markedly improved by accounting for the distribution of the characteristics in the drainage area. The stability of the final model, which gives an r²-value of 0.74, has been tested with positive results. The model allows lake colour to be estimated from knowledge of “geological” characteristics of the lake and its drainage area. The variability between lakes from other factors, such as temperature, precipitation and/or contamination of acidifying substances and nutrients, may then be quantitatively differentiated from the impact of these “geological” factors.     

Organic Carbon Flux to a Large Salt Lake: Pyramid Lake,Nevada, USA

Energy flux to a large, deep, salt lake from phytoplankton, periphyton and macrophyte primary production as well as fluvial transport and wind-transported terrestrial vegetation and dust were quantified. Average areal phytoplankton net photosynthesis was 511 mg C m⁻² d⁻¹. Highest rates were during water-blooms of the bluegreen alga, Nodularia spumigena. Although areal daily net photosynthesis by periphyton in Pyramid Lake was comparable to other salt lakes, annual carbon influx by periphyton was small due to the lake's graben morphology and moderate euphotic depth (mean, 11.9 m). Macrophytes were uncommon and, therefore a minor source of energy. Truckee River is the only major fluvial discharge to Pyramid Lake and dissolved organic carbon was the principal organic carbon fraction in river water. Large upstream water diversions coupled with several drought years resulted in an average fluvial organic carbon load of only 7.3 g Cm⁻²y⁻¹ or 4% of median phytoplankton net photosynthesis. Tumbleweeds were the most common terrestrial plant material observed in Pyramid Lake comprising a maximum projected importance of 6% of total annual carbon input. Windborne dust represented < .1% of annual carbon input. Phytoplankton primary production is the predominant energy source to Pyramid Lake, accounting for over 80% of annual carbon influx. The relative magnitude of autochthonous and allochthonous vectors to the annual carbon budget of this desert salt lake are comparable to those of the few other large lakes for which detailed energy input budgets have been calculated.     

Exploratory Hydrocarbon Drilling Impacts to Arctic Lake Ecosystems

Recent attention regarding the impacts of oil and gas development and exploitation has focused on the unintentional release of hydrocarbons into the environment, whilst the potential negative effects of other possible avenues of environmental contamination are less well documented. In the hydrocarbon-rich and ecologically sensitive Mackenzie Delta region (NT, Canada), saline wastes associated with hydrocarbon exploration have typically been disposed of in drilling sumps (i.e., large pits excavated into the permafrost) that were believed to be a permanent containment solution. However, failure of permafrost as a waste containment medium may cause impacts to lakes in this sensitive environment. Here, we examine the effects of degrading drilling sumps on water quality by combining paleolimnological approaches with the analysis of an extensive present-day water chemistry dataset. This dataset includes lakes believed to have been impacted by saline drilling fluids leaching from drilling sumps, lakes with no visible disturbances, and lakes impacted by significant, naturally occurring permafrost thaw in the form of retrogressive thaw slumps. We show that lakes impacted by compromised drilling sumps have significantly elevated lakewater conductivity levels compared to control sites. Chloride levels are particularly elevated in sump-impacted lakes relative to all other lakes included in the survey. Paleolimnological analyses showed that invertebrate assemblages appear to have responded to the leaching of drilling wastes by a discernible increase in a taxon known to be tolerant of elevated conductivity coincident with the timing of sump construction. This suggests construction and abandonment techniques at, or soon after, sump establishment may result in impacts to downstream aquatic ecosystems. With hydrocarbon development in the north predicted to expand in the coming decades, the use of sumps must be examined in light of the threat of accelerated permafrost thaw, and the potential for these industrial wastes to impact sensitive Arctic ecosystems.     

Some effects of demersal trawling in Lake Malawi (Lake Nyasa) from 1968 to 1974

Exploratory trawl data were used to define demersal fish stocks of Lake Malawi in terms of abundance by depth and area. The mean weight of the catch generally declined with increasing depth. A comparison of initial standing stock estimates and the yield from a commercial fishery over a 7 year period suggests a potential yield of less than half of the initial stock. Over 160 species of fish have been identified in the trawl catch of which over 80% by weight were cichlids. Some of the commonest species of cichlids are listed. The composition of the catch in the heavily exploited southern end of the lake has changed from one dominated by large species of Haplochromis sp. and Lethrinops sp. to one dominated by smaller species.     

Results of the introduction of Coregonids to Lake Vashozero

The results of the introduction of coregonids—the whitefish Coregonus lavaretus and the European cisco C. albula—to Lake Vashozero are considered. It is shown that a positive result was obtained from the introduction of the European cisco; it has naturalized in the lake and successfully reproduces. The biology of the European cisco in a water body new for it was studied, and it was compared to its initial form from Onega Lake. The structure of trophic relations in the water body has changed with the introduction of the European cisco. Previously there was one flow of matter and energy in the lake: benthos—benthophagous fish—carnivorous fish. Now, however, another flow has been added: plankton—European cisco—carnivorous fish.     

Pelagic rotifers of Lake Glubokoe from 1897 to 1984

After alteration in the pattern of drainage of run-off from the surrounding swamps and changes in the colour and transparency of the Lake Glubokoe water, the previously epilimnial Trichocerca similis, Conochilus unicornis and Keratella cochlearis showed a shift of their maximum numbers to deeper layers. Pompholyx sp. and Trichocerca capucina, which are regarded as indicators of eutrophic waters, have disappeared from the pelagic zone of the lake and Conochilus hippocrepis, Synchaeta pectinata, Gastropus stylifer, Asplanchna herricki, Ascomorpha ecaudis, Ascomorpha saltans, Euchlanis dilatata and Trichocerca porcellus have made their appearance. Most of the new species are considered to be indicators of oligotrophic conditions. However the total density of pelagic rotifers remained at the same level. Apparently the establishment of the new species of rotifers was possible due to some ‘rarefaction’ of the epilimnion, the disappearance of predaceous Mesocyclops leuckarti and the invasion of the pelagic zone by Peridinium cinctum.     

Size-dependent phytoplankton responses to atmospheric forcing in Lake Biwa

Size-dependent changes in chlorophyll a and uptake of inorganiccarbon (C) and nitrogen (N) by phytoplankton were measured inthe shallow South Basin of Lake Biwa, before and during a periodof typhoons (high winds). The latter period was characterizedby complete mixing of the water column, a major decline in underwaterirradiance, and a transient increase in dissolved reactive Nand phosphorus (P). Nutrient concentrations, seston N:P ratiosand uptake rates indicate that P and not N limited phytoplanktonover the whole study period. The typhoon-induced increase inphosphorus supply resulted in Blackman-type (increased C- andN-specific growth rates) and Liebig-type (increased biomassyield) responses by the phytoplankton. Picoplankton were dominantin the relatively stable and clear water column prior to thetyphoons, but were rapidly outgrown by larger cells during andafter wind-induced mixing. The slower response of picoplanktonindicates lower maximum intrinsic growth rates and photosyntheticefficiency. These observations are contrary to the view thatpicoplankton have higher light-harvesting abilities and growthrates than larger cells. Typhoon-induced mixing stimulated theshift to fast-growing, dim light-adapted larger cells. The resultsquestion the allometric paradigm of increasing growth ratesand light-capturing efficiency with decreasing cell size, butare consistent with the oceanographic view that large-celledphytoplankton control the major fluctuations in biomass andprimary productivity, while picoplankton account for a comparativelystable background productivity.     

Contribution to the lithostratigraphy and history of Lake Ladoga

New geological data from Lake Ladoga are presented and an interpretation of the Late Pleistocene and Holocene history of the lake is given. The deglaciation of the southern part of the lake and an origin of the first ice margin Lake Ladoga took place at ca. 14,000 yr B.P.     

近33年白洋淀景观动态变化

湿地具有重要的生态功能,由于各种因素的影响改变了湿地水文条件,并且导致湿地退化。利用1974、1987、1996和2007年遥感影像,使用ERDAS 9.1、ARCGIS 9.2和FRAGSTATS 3.3,分析了白洋淀景观动态变化过程及其驱动力。研究结果表明:从1974至2007年,白洋淀湿地面积从249.4km²下降到182.6km²,农田和居民地面积分别从70.0、2.1km²增加到126.4、12.5km²;在景观水平上,斑块密度、景观形状指数和香农多样性指数增加,蔓延度减小,景观破碎化程度增加,优势景观类型湿地对整个景观的控制作用减小;在类型水平上,明水面和沼泽的斑块密度和周长-面积分维数增加,最大斑块指数、平均斑块面积和连接度减小,居民地的斑块密度、最大斑块指数、平均斑块面积、周长-面积分维数和连接度都增加,农田的斑块密度、最大斑块指数和连接度增加,平均斑块面积和周长-面积分维数减小;水位变化是影响白洋淀景观变化的主要因素,水位升高会使湿地面积增加,反之,使湿地面积减小;流域人类活动和降水量变化是白洋淀水位和景观变化的重要驱动力。引水补淀只能暂时缓解白洋淀缺水问题,从流域角度考虑,实施有效的水资源管理方式,才能从根本上解决白洋淀湿地退化的问题。     

Use of otolith microchemistry to identify subbasin natal origin and use by invasive Lake Trout in Yellowstone Lake

Hydrobiologia - Nonindigenous lake trout (Salvelinus namaycush) expansion in Yellowstone Lake has led to a large decline in the native Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri)...     

Genetic variation in the marbled lungfish Protopterus aethiopicus in Lake Victoria and introduction to Lake Baringo, Kenya

Marbled lungfish Protopterus aethiopicus in Lake Victoria and two nearby smaller lakes were found to have high levels of DNA sequence variation in their mitochondrial control regions (35 haplotypes in 61 fish) but no population genetic structure (Φ_ST= 0·00). In contrast, marbled lungfish in Lake Baringo, Kenya, appeared to be fixed for a single control region haplotype, which occurred at low frequency in the other lakes. Using FLUCTUATE software, the female effective population size in Lake Victoria during the late Pleistocene was estimated to be c. 500 000, similar to the value estimated for the present-day population. These observations suggest that, during the late Pleistocene dry period, a large marbled lungfish population survived either in wet refugial areas within the lake basin or in surrounding areas. Marbled lungfish were reported to have been introduced into Lake Baringo 30 years ago with a founding population of only three individuals. The lack of control region variation in the Lake Baringo population is consistent with that situation.     

Lake circulation and sediment transport in Lake Myvatn

Lake circulation and sediment transport in Lake Myvatn have been calculated using AQUASEA, a numerical model developed by Vatnaskil Consulting Engineers. The goal of the modelling was to calculate changes in sediment transport within the lake due to changes in lake bathymetry caused by diatomite mining. The model uses the Galerkin finite element method and consists of a hydrodynamic flow model and a transport-dispersion model. The flow model is based on the shallow water equations and the wave equation. The transport model is based on the conservation of mass for suspended sediment. The model was calibrated against measurements performed during the summer of 1992. These included measurements of water elevation, current velocity, wave height, and concentration of suspended sediment. After calibration, the model was run for different mining scenarios to determine their impact on the sediment transport in the lake.     

Development of a visualization platform oriented to Lake water quality targets management - A case study of Lake Taihu

Lake Taihu is well known for its severe environmental degradation. In previous studies of lake quality target management, the water quality targets were poorly correlated with watershed pollutant reduction, and most studies lacked visualized management platform that covered all elements including lakes, in-lake estuaries, rivers and watershed regions. In this study, a browser/server-based visualization platform for lake quality target management was developed. Five models that covered both the watershed and lake scales were integrated based on two critical functions. First, the proposed method can be used to determine watershed pollutant reduction amounts based on certain lake quality target parameters, such as those for TN, TP, NH₃N and COD. Second, the method can simulate the lake quality trends associated with different watershed adjustment plans. The platform was deployed by the Taihu Basin Authority (TBA) of the Ministry of Water Resources. Overall, this platform is a useful tool for watershed-lake environmental management.     

Linking Host Prokaryotic Physiology to Viral Lifestyle Dynamics in a Temperate Freshwater Lake (Lake Pavin,France)

In aquatic ecosystems, fluctuations in environmental conditions and prokaryotic host physiological states can strongly affect the dynamics of viral life strategies. The influence of prokaryote physiology and environmental factors on viral replication cycles (lytic and lysogeny) was investigated from April to September 2011 at three different strata (epi, meta, and hypolimnion) in the mixolimnion of deep volcanic temperate freshwater Lake Pavin (France). Overall, the euphotic region (epi and metalimnion) was more dynamic and showed significant variation in microbial standing stocks, prokaryotic physiological state, and viral life strategies compared to the aphotic hypolimnion which was stable within sampled months. The prokaryotic host physiology as inferred from the nucleic acid content of prokaryotic cells (high or low nucleic acid) was strongly regulated by the chlorophyll concentration. The predominance of the high nucleic acid (HNA) prokaryotes (cells) over low nucleic acid (LNA) prokaryotes (cells) in the spring (HNA/LNA?=?1.2) and vice versa in the summer period (HNA/LNA?=?0.4) suggest that the natural prokaryotic communities underwent major shifts in their physiological states during investigated time period. The increase in the percentage of inducible lysogenic prokaryotes in the summer period was associated with the switch in the dominance of LNA over HNA cells, which coincided with the periods of strong resource (nutrient) limitation. This supports the idea that lysogeny represents a maintenance strategy for viruses in unproductive or harsh nutrient/host conditions. A negative correlation of percentage of lysogenic prokaryotes with HNA cell abundance and chlorophyll suggest that lysogenic cycle is closely related to prokaryotic cells which are stressed or starved due to unavailability of resources for its growth and activity. Our results provide support to previous findings that changes in prokaryote physiology are critical for the promotion and establishment of lysogeny in aquatic ecosystems, which are prone to constant environmental fluctuations.