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1.
2.
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   

3.
I addressed the question how lake and catchment morphometry influences water chemistry and water quality over a large scale of European lakes, and developed the regression equations between most closely related morphometric and water quality indices. I analysed the data of 1,337 lakes included in the European Environment Agency (EEA) database, carrying out separate analyses for three basic lake types: large lakes (area ≥100 km2, 138 lakes), shallow lakes (mean depth ≤3 m, 153 lakes) and large and shallow lakes (area ≥100 km2 and mean depth ≤8 m, 35 lakes). The study revealed that in Europe, the lakes towards North are larger but shallower and have smaller catchment areas than the southern lakes; lakes at higher altitudes are deeper and smaller and have smaller catchment areas than the lowland lakes. Larger lakes have generally larger catchment areas and bigger volumes, and they are deeper than smaller lakes, but the relative depth decreases with increasing surface area. The lakes at higher latitudes have lower alkalinity, pH and conductivity, and also lower concentrations of nitrogen and phosphorus while the concentration of organic matter is higher. In the lakes at higher altitudes, the concentration of organic matter and nutrient contents are lower and water is more transparent than in lowland lakes. In larger lakes with larger catchment area, the alkalinity, pH, conductivity and the concentrations of nutrients and organic matter are generally higher than in smaller lakes with smaller catchments. If the lake is deep and/or its residence time is long, the water is more transparent and the concentrations of chlorophyll a, organic matter and nutrients are lower than in shallower lakes with shorter residence times. The larger the catchment area is with respect to lake depth, area and volume, the lower is the water transparency and the higher are the concentrations of the nutrients, organic matter and chlorophyll as well as pH, alkalinity and conductivity. The links between lake water quality and morphometry become stronger towards large and shallow lakes. Along the decreasing gradients of latitude, altitude and relative depth, the present phosphorus concentration and its deviation from the reference concentration increases.  相似文献   

4.
In Europe there is a renewed focus on relationships between chemical determinands and ecological impact as a result of the Water Framework Directive (WFD). In this paper we use regression analysis to examine the relationship of growing season mean chlorophyll a concentration with total phosphorus and total nitrogen using summary data from over 1,000 European lakes. For analysis, lakes were grouped into types with three categories of mean depth, alkalinity and humic content. The lakes were also divided into broad geographic regions covering Atlantic, Northern, Central/Baltic and for some types the Mediterranean areas of Europe. Chlorophyll a was found to be significantly related to both total phosphorus and total nitrogen, although total phosphorus was almost always found to be the best predictor of chlorophyll. Different nutrient chlorophyll relationships were found for lakes according to mean depth and alkalinity, although no significant effect of geographic region or humic content was found for the majority of lake types. We identified three groups of lakes with significantly different responses. Deep lakes had the lowest yield of chlorophyll per unit of nutrient, low and moderate alkalinity shallow lakes the highest and high alkalinity lakes were intermediate. We recommend that the regression models provided for these three lake groups should be used for lake management in Europe and discuss the limitations of such models.  相似文献   

5.
A fish – based index for the assessment of the ecological quality of natural temperate lakes was developed, in accordance to the requirements of the Water Framework Directive (WFD) 2000/60/EC. As a case study, 11 natural lakes located at northern and western Greece were selected. Fish surveys were conducted during mid summer to mid autumn in 2010, 2011 and 2012 using Nordic gillnets and electrofishing. Environmental parameters and anthropogenic pressures were assessed for each lake. Fish species richness, abundance, trophic, reproductive and habitat functional guilds were used for extracting a set of 107 metrics, meeting the requirements of the WFD. All metrics were initially tested as candidates for the index development. A stepwise linear regression of each metric against environmental parameters (lake area, altitude, maximum depth, alkalinity) and anthropogenic pressures (drainage area covered by non-natural land uses – NNLC, water total phosphorus concentrations – TP, Lake Habitat Modification Score – LHMS) was initially conducted for ensuring pressure-response relationships. Reference conditions for each lake were estimated by the hindcasting procedure and the ecological quality for each lake was expressed as the ecological quality ratio (EQR) by a value ranging from 0 (poor quality) to 1 (excellent quality). Two fish fauna metrics, the relative numerical abundance of introduced species (Introduceda) and the relative biomass of omnivorous species (OMNIb) were finally extracted as the most significant, responding to LHMS and TP, respectively. The final index was expressed as the mean values of the EQRs of these two metrics. The multimetric fish index presented herein could serve as a tool for assessing the ecological quality of natural lakes at broad geographical scale and generally, in the Mediterranean temperate lakes with similar hydromorphological characteristics.  相似文献   

6.
Analysis of phytoplankton data from about 1,500 lakes in 20 European countries has revealed that two-thirds of the species that dominate lakes during the summer are dominant right across Europe. Using Canonical Correspondence Analyses, we have examined how both habitat conditions within lakes and environmental factors over broad geographical scales explained the distribution of the 151 most common summer dominant species. The distributions of these species were best explained by water colour and latitude, although alkalinity and total phosphorus also appeared to be important explanatory factors. Contrary to our original hypothesis, summer water temperatures had a negligible impact on the distribution of dominants, although, due to the restricted summer season we examined, only a limited temperature gradient was present in the dataset. Cryptophytes occurred more frequently among dominants in Northern Europe whereas cyanobacteria and dinophytes dominated more in Central and Southern Europe. Our analyses suggest that besides nutrient concentrations, other water chemistry variables, such as alkalinity and the content of humic substances, have at least as important a role in determining the distribution of the dominant phytoplankton species in European lakes.  相似文献   

7.
To date, studies examining the impact of agriculture on freshwater systems have been spatially confined (that is, single drainage basin or regional level). Across regions, there are considerable differences in a number of factors, including geology, catchment morphometry, and hydrology that affect water quality. Given this heterogeneity, it is unknown whether agricultural activities have a pervasive impact on lake trophic state across large spatial scales. To address this issue, we tested whether the proportion of agricultural land in a catchment (% Agr) could explain a significant portion of the variation in lake water quality at a broad inter-regional scale. As shallow, productive systems have been shown to be particularly susceptible to eutrophication, we further investigated how lake mean depth modulates the relationship between % Agr and lake total phosphorus (TP) concentration. We applied both traditional meta-analytic techniques and more sophisticated linear mixed-effects models to a dataset of 358 temperate lakes that spanned an extensive spatial gradient (5°E to 73°W) to address these issues. With meta-analytical techniques we detected an across-study correlation between TP and % Agr of 0.53 (one-tailed P-value = 0.021). The across-study correlation coefficient between TP and mean depth was substantially lower (r = −0.38; P = 0.057). With linear mixed-effects modeling, we detected among-study variability, which arises from differences in pre-impact (background) lake trophic state and in the relationship between lake mean depth and lake TP. To our knowledge, this is the first quantitative synthesis that defines the influence of agriculture on lake water quality at such a broad spatial scale. Syntheses such as these are required to define the global relationship between agricultural land-use and water quality.  相似文献   

8.
1. Classification of European lake fish assemblages can be based on fish‐assemblage structure or morphological, geographical, physical and chemical lake attributes. However, substantial gaps in knowledge exist with respect to the correspondence between both classification approaches. 2. Here, we compiled fish assemblage data from 165 lakes situated in the European ‘Central Plains’ ecoregion. Cluster analysis of fish abundances was performed to compare fish assemblage types of the entire ecoregion with those from previous country‐specific studies. Nonparametric group comparisons, classification trees and partial canonical ordinations were used to infer the correspondence between fish assemblage types and morphology, geographical position and nutrient concentration of the lakes. 3. Three distinct fish assemblages were revealed: vendace (Coregonus albula), ruffe (Gymnocephalus cernuus) and roach (Rutilus rutilus) lake types. Both latitude and lake depth were the best determinants of lake type, but total phosphorus (TP) concentrations were also important. Vendace lakes were deep and had low TP concentrations, whereas the shallower ruffe and roach lakes had higher TP values. Roach lakes were more frequent in the north‐west area of the ecoregion, whereas ruffe lakes were more often found south of the Baltic Sea. 4. Controlling for the influence of nutrient concentration showed that lake morphology and geographical position were important determinants of fish assemblages. However, the variance explained was low (<20%), implying that biological interactions may also be important in forming the lake‐specific fish assemblages. 5. The results suggest that fish assemblages differ between deep and shallow lakes, and between the north‐west and south‐east locations within the Central Plains ecoregion. Accordingly, establishment of depth‐related lake morphotypes is needed, and the European ecoregions recommended to be used in evaluation systems according to the Water Framework Directive seem to be too coarse to reflect the subtle differences of fish species richness along geographical gradients.  相似文献   

9.
1. This synthesis examines 35 long‐term (5–35 years, mean: 16 years) lake re‐oligotrophication studies. It covers lakes ranging from shallow (mean depth <5 m and/or polymictic) to deep (mean depth up to 177 m), oligotrophic to hypertrophic (summer mean total phosphorus concentration from 7.5 to 3500 μg L?1 before loading reduction), subtropical to temperate (latitude: 28–65°), and lowland to upland (altitude: 0–481 m). Shallow north‐temperate lakes were most abundant. 2. Reduction of external total phosphorus (TP) loading resulted in lower in‐lake TP concentration, lower chlorophyll a (chl a) concentration and higher Secchi depth in most lakes. Internal loading delayed the recovery, but in most lakes a new equilibrium for TP was reached after 10–15 years, which was only marginally influenced by the hydraulic retention time of the lakes. With decreasing TP concentration, the concentration of soluble reactive phosphorus (SRP) also declined substantially. 3. Decreases (if any) in total nitrogen (TN) loading were lower than for TP in most lakes. As a result, the TN : TP ratio in lake water increased in 80% of the lakes. In lakes where the TN loading was reduced, the annual mean in‐lake TN concentration responded rapidly. Concentrations largely followed predictions derived from an empirical model developed earlier for Danish lakes, which includes external TN loading, hydraulic retention time and mean depth as explanatory variables. 4. Phytoplankton clearly responded to reduced nutrient loading, mainly reflecting declining TP concentrations. Declines in phytoplankton biomass were accompanied by shifts in community structure. In deep lakes, chrysophytes and dinophytes assumed greater importance at the expense of cyanobacteria. Diatoms, cryptophytes and chrysophytes became more dominant in shallow lakes, while no significant change was seen for cyanobacteria. 5. The observed declines in phytoplankton biomass and chl a may have been further augmented by enhanced zooplankton grazing, as indicated by increases in the zooplankton : phytoplankton biomass ratio and declines in the chl a : TP ratio at a summer mean TP concentration of <100–150 μg L?1. This effect was strongest in shallow lakes. This implies potentially higher rates of zooplankton grazing and may be ascribed to the observed large changes in fish community structure and biomass with decreasing TP contribution. In 82% of the lakes for which data on fish are available, fish biomass declined with TP. The percentage of piscivores increased in 80% of those lakes and often a shift occurred towards dominance by fish species characteristic of less eutrophic waters. 6. Data on macrophytes were available only for a small subsample of lakes. In several of those lakes, abundance, coverage, plant volume inhabited or depth distribution of submerged macrophytes increased during oligotrophication, but in others no changes were observed despite greater water clarity. 7. Recovery of lakes after nutrient loading reduction may be confounded by concomitant environmental changes such as global warming. However, effects of global change are likely to run counter to reductions in nutrient loading rather than reinforcing re‐oligotrophication.  相似文献   

10.
General relationships between phytoplankton production, chlorophyll, total, dissolved and particulate phosphorus, Secchi depth, humic level, trophic level, fish production and latitude are described by regression equations using an extensive “Soviet” data base covering a wide domain of lake characteristics and a European data base. New systems for defining lake trophic and humic status are presented. The results may be used for more precise estimates of fundamental lake properties and for many practical issues of lake management, e.g., predictions of fish catch. We have used strict chlorophyll‐a concentrations for every trophic class and we have omitted Secchi depth from the trophic classes, since Secchi depth and other variables strongly related to water clarity (like suspended particulate matter and particulate organic carbon) depend on autochthonous production, allochthonous influences and resuspension. We have used the Secchi depth as a simple operational measure of the effective depth of the photic zone. It has also been shown that among these lakes there exist a very strong relationship between primary production and latitude. In fact, 74% of the variability among the lakes in mean summer primary production can be statistically related to variations in latitude. These data also show a strong relationship between primary production and fish yield, which can be used to address many fundamental issues in lake management, like “normal and abnormal fish production”.  相似文献   

11.
It has been suggested that shallow lakes in warm climates have a higher probability of being turbid, rather than macrophyte dominated, compared with lakes in cooler climates, but little field evidence exists to evaluate this hypothesis. We analyzed data from 782 lake years in different climate zones in North America, South America, and Europe. We tested if systematic differences exist in the relationship between the abundance of submerged macrophytes and environmental factors such as lake depth and nutrient levels. In the pooled dataset the proportion of lakes with substantial submerged macrophyte coverage (> 30% of the lake area) decreased in a sigmoidal way with increasing total phosphorus (TP) concentration, falling most steeply between 0.05 and 0.2 mg L−1. Substantial submerged macrophyte coverage was also rare in lakes with total nitrogen (TN) concentrations above 1–2 mg L−1, except for lakes with very low TP concentrations where macrophytes remain abundant until higher TN concentrations. The deviance reduction of logistic regression models predicting macrophyte coverage from nutrients and water depth was generally low, and notably lowest in tropical and subtropical regions (Brazil, Uruguay, and Florida), suggesting that macrophyte coverage was strongly influenced by other factors. The maximum TP concentration allowing substantial submerged macrophyte coverage was clearly higher in cold regions with more frost days. This is in agreement with other studies which found a large influence of ice cover duration on shallow lakes' ecology through partial fish kills that may improve light conditions for submerged macrophytes by cascading effects on periphyton and phytoplankton. Our findings suggest that, in regions where climatic warming is projected to lead to fewer frost days, macrophyte cover will decrease unless the nutrient levels are lowered.  相似文献   

12.
Phosphorus (P) dynamics in large shallow lakes are greatly influenced by physical processes such as wind-driven sediment resuspension, at times scales from hours to years. Results from long-term (30 year) research on Lake Okeechobee, Florida (area 1,730 km2, mean depth 2.7 m) illustrate key features of these P dynamics. Variations in wind velocity result in changes in water column transparency, suspended solids, and total P (TP). In summer there are diurnal changes in TP associated with afternoon winds, and in winter, when strong winds occur for multiple days, monthly average TP remains high compared to summer. The magnitude of daily and seasonal TP changes can exceed 100 μg l−1. Hurricanes and tropical storms also cause extreme changes in TP that are superimposed on seasonal dynamics. When a hurricane passed 80 km south of the lake in October 1999, mean pelagic TP increased from 88 to 222 μg l−1. During large resuspension events, light attenuation is substantially increased, and this influences the biomass and spatial extent of submerged plants, as well as water column TP. In Lake Okeechobee, TP concentrations typically are ∼20 μg l−1 when submerged plants are dense, and soluble reactive P concentrations are reduced below detection, perhaps by the periphyton and plant uptake and by precipitation with calcium at high pH. In contrast, TP exceeds 50 μg l−1 when submerged plants and periphyton are absent due to prolonged deep water, and phytoplankton biomass and algal bloom frequency both are increased. In Lake Okeechobee and other large shallow lakes, complex models that explicitly consider wind-wave energy, hydrodynamics, and sediment resuspension, transport, and key biological processes are needed to accurately predict how lake water TP will respond to different management options.  相似文献   

13.
Our objective was to assess the potential of Cladocera from mountain lakes for climate reconstruction. We related Cladocera from surface sediments of Alpine lakes (1,502–2,309 m asl) to 29 abiotic environmental variables using statistical methods. The environmental dataset included water chemistry, lake depth, and bi-hourly water-temperature logs, which were used to assess mean monthly water temperatures, dates of freezing and breakup, spring and autumn mixing. We found 14 different Cladocera of the families Bosminidae, Daphniidae, and Chydoridae. Lakes without Cladocera (eight lakes) were cold and/or ultra-oligotrophic, whereas lakes with planktonic and littoral Cladocera (19 lakes) were warmer and/or less oligotrophic. Lakes with only littoral Cladocera (18 lakes) had intermediate water temperatures/trophy. Changes in Cladocera assemblages were related to changes in climate, nutrients, and/or alkalinity. We found a climate threshold at which Bosminidae disappeared in 95% of the lakes. For climate-change research, we propose studying Cladocera along transects that include climatic thresholds. Guest editor: Piet Spaak Cladocera: Proceedings of the 7th International Symposium on Cladocera  相似文献   

14.
Using published paleolimnological results from 14 dimictic calcareous lakes, this study identifies total phosphorous (TP) reference values for the European lake type CB 1. The initial increase in settlement-associated pollen occurred in the catchments between ad ~1000 and ~1820. A departure from diatom-inferred TP reference conditions occurred during periods of increased human activities during Early to Late Medieval Times (ad ~1110–1325; four lakes), early Modern Times (ad ~1575–1600; two lakes), after the 30 years’ war (>ad 1650; two lakes) and during the Anthropocene (after ad ~1850, three lakes). Only one lake continuously has TP reference values until recent days, whilst TP reference values could not be detected in two cases. Thus, we refrain from setting a fixed point in time for defining reference conditions for lakes in the European Central Plains. This study also validates TP reference levels calculated based on common lake models for CB 1-lakes and assesses the range of TP reference levels using paleolimnological diatom studies. The highly variable diatom-inferred TP reference levels only partly support the modelled levels. Thus, we recommend using two subtypes (CB 1a and 1b), based on the watershed to volume ratio to better meet the requirements of lake type-specific reference levels.  相似文献   

15.
16.
Bacterial growth and grazing mortality were estimated from Mayto October in two south Swedish oligotrophic lakes, one beinga clearwater lake (water colour 5–10 mg Pt l–1 DOC2.9–3.4 mg l–1, Secchi disk depth 5.0–9.4m) and the other a humic, brownwater lake (water colour 105–165mg Pt l–1, DOC 13.7–22.7mg l–1, Secchi diskdepth 1.3–2.1 m). Specific rates of growth and grazingmortality were generally similar for both lakes. However, theabundance of bacteria was consistently 2–3 times higherin the water of the humic lake, suggesting that the total productionand consumption of bacterial cells were also higher than inthe dearwater lake. The ratio of bacterial secondary productionto primary production was higher in the humic lake than in theclearwater lake, indicating that the bacterioplankton of thehumic lake utilize allochthonous substrates, in addition tosubstrates originating from autochthonous primary production.Most of the bacterial loss in both lakes could be attributedto small protozoan grazers. This implies that allochthonousand autochthonous organic carbon fixed by bacterioplankton isless important in terms of carbon flow to higher trophic levelsthan would be expected if macrozooplankton were the dominantbacterivores, providing a more direct and efficient transferof carbon to larger organisms.  相似文献   

17.
1. Knowledge of synchrony in trends is important to determining regional responses of lakes to disturbances such as atmospheric deposition and climate change. We explored the temporal coherence of physical and chemical characteristics of two series of mostly alpine lakes in nearby basins of the Colorado Rocky Mountains. Using year‐to‐year variation over a 10‐year period, we asked whether lakes more similar in exposure to the atmosphere be‐haved more similarly than those with greater influence of catchment or in‐lake processes. 2. The Green Lakes Valley and Loch Vale Watershed are steeply incised basins with strong altitudinal gradients. There are glaciers at the heads of each catchment. The eight lakes studied are small, shallow and typically ice‐covered for more than half the year. Snowmelt is the dominant hydrological event each year, flushing about 70% of the annual discharge from each lake between April and mid‐July. The lakes do not thermally stratify during the period of open water. Data from these lakes included surface water temper‐ature, sulphate, nitrate, calcium, silica, bicarbonate alkalinity and conductivity. 3. Coherence was estimated by Pearson's correlation coefficient between lake pairs for each of the different variables. Despite close geographical proximity, there was not a strong direct signal from climatic or atmospheric conditions across all lakes in the study. Individual lake characteristics overwhelmed regional responses. Temporal coherence was higher for lakes within each basin than between basins and was highest for nearest neighbours. 4. Among the Green Lakes, conductivity, alkalinity and temperature were temporally coherent, suggesting that these lakes were sensitive to climate fluctuations. Water tem‐perature is indicative of air temperature, and conductivity and alkalinity concentrations are indicative of dilution from the amount of precipitation flushed through by snowmelt. 5. In Loch Vale, calcium, conductivity, nitrate, sulphate and alkalinity were temporally coherent, while silica and temperature were not. This suggests that external influences are attenuated by internal catchment and lake processes in Loch Vale lakes. Calcium and sulphate are primarily weathering products, but sulphate derives both from deposition and from mineral weathering. Different proportions of snowmelt versus groundwater in different years could influence summer lake concentrations. Nitrate is elevated in lake waters from atmospheric deposition, but the internal dynamics of nitrate and silica may be controlled by lake food webs. Temperature is attenuated by inconsistently different climates across altitude and glacial meltwaters. 6. It appears that, while the lakes in the two basins are topographically close, geologically and morphologically similar, and often connected by streams, only some attributes are temporally coherent. Catchment and in‐lake processes influenced temporal patterns, especially for temperature, alkalinity and silica. Montane lakes with high altitudinal gradients may be particularly prone to local controls compared to systems where coherence is more obvious.  相似文献   

18.
Phytoplankton data from 606 lakes were used to characterize indicator taxa of near-pristine reference conditions in clearwater and humic lowland lakes of Northern and Central Europe. Reference lakes were selected based on low pressure from catchment land-use, low population density and the absence of point sources. Reference lakes had low phytoplankton biomass and taxa richness compared to non-reference lakes. In low alkalinity lakes of Northern Europe, the reference communities had high biomass proportions of chrysophytes and low proportions of cyanobacteria; in the Central European high alkalinity lakes, the biomass was distributed more evenly among algal groups. Indicator species analysis and similarity analysis listed 5–29 taxa indicating reference conditions. Indicator taxa differed especially between the low alkalinity and the high alkalinity lakes, but there were also country-specific differences. Most common indicator taxa for the northern reference lakes were chrysophytes (e.g. Bitrichia, Dinobryon). In the Central European reference lakes, diatoms (e.g. Cyclotella) were more characteristic. Despite the differences, there was a general finding that taxa present in reference lakes were often also present in non-reference lakes, but typically in lower biomass proportions; another characteristic of the reference communities is the absence of many taxa typically found in non-reference lakes.  相似文献   

19.
In order to establish a fish-based typology of Italian lakes and identify possible reference and indicator fish species for each lake type, we analysed historical data on fish assemblages of all Italian natural lakes >0.5 km2 from the period prior to the major decline in water quality in the 1950s. General linear regression models showed the ecoregion and lake altitude being the best predictors of fish species richness. The number of species was significantly higher in the Alpine than in the Mediterranean ecoregion. Among Alpine lakes, the number of fish species increased significantly with lake volume whilst decreased with altitude. In the Mediterranean lakes, none of the selected parameters was significant. Cluster analysis of fish assemblages (presence/absence) divided the lakes of the Alpine and Mediterranean ecoregions into four and two types, respectively. Pike (Esox lucius), rudd (Scardinius erythrophthalmus) and tench (Tinca tinca) were the main indicator species for the small and mostly shallow lakes in both the Alpine (Type 1) and Mediterranean (Type 6) ecoregions, minnow (Phoxinus phoxinus) for the alpine high altitude lakes (Type 2) and landlocked shad (Alosa fallax lacustris), European whitefish (Coregonus lavaretus) and burbot (Lota lota) for the large and very deep alpine lakes (Type 4). The European whitefish was the only indicator species for the deep Mediterranean lakes (Type 5). These species and associated fish assemblages may be useful indicators in future assessments of the ecological status of Italian lakes according to the European Directives (2000/60/EC and 2008/105/EC).  相似文献   

20.
中国典型湖泊富营养化现状与区域性差异分析   总被引:4,自引:0,他引:4  
为全面科学地综合评估全国富营养化现状, 以全国五大湖区22个典型湖泊为研究对象, 科学评估了其富营养化状态, 分析了全国湖泊富营养化状态的区域性差异, 并探讨了富营养化状态与总磷的定量关系。结果表明, 2010—2011年, 59.1%的调研湖泊处于不同程度的富营养化状态, 其中云贵湖区的富营养化程度最为严重, 蒙新湖区的富营养化呈两极分化状态, 东北山地-平原湖区与东部湖区的湖泊基本均处于中营养-轻度富营养之间, 青藏高原湖区的富营养化程度最低。通过分析日照数、无霜期、气温、水深、海拔、降雨与湖泊营养状态的关系, 揭示了湖泊所处的地理位置是影响湖泊富营养化的基本因素, 具有区域性的分布规律。综合分析结果表明, 全国范围内湖泊中叶绿素a与总磷浓度存在显著相关性, 其中东部平原湖区、东北平原-山地湖区、青藏高原湖区和云贵高原湖区的叶绿素a与总磷浓度符合三次曲线方程, 蒙新湖区的叶绿素a与总磷浓度符合S型曲线方程; 东部平原湖区、东北平原-山地湖区、青藏高原湖区叶绿素浓度随着总磷浓度的增加, 首先出现1个极小值点, 然后出现1个极大值点, 其中3个湖区极小值点对应的总磷浓度分别为: 0.054、0.089和0.072 mg/L, 可为我国对应湖区的湖泊富营养化控制指标提供借鉴。  相似文献   

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