Use of diatom life-forms and ecological guilds to assess pesticide contamination in rivers: Lotic mesocosm approaches

The persistence of pesticides in the environment and their effects are a cause of concern to more and more people, and so in 2009 the French government announced plans to reduce pesticide use in agriculture over the next 10 years. Water managers are to monitor the beneficial impact of this reduction on aquatic environments. It has been suggested that diatoms may be good indicators of pesticides, and more particularly of herbicides, in water. Diatoms have been routinely used to assess organic and nutrient pollution for more than 10 years. The general approach is to develop a diatom-based tool to assess pesticide contamination. Diatom indices are usually based on specific pollution sensitivity. Other metrics, such as life-forms, ecological guilds, or cell size offer other advantages. For instance, the relationships between trends in these metrics and environmental gradients are more robust, and make it easier to establish ecological hypotheses. We have therefore opted for this approach.To develop such a tool, outdoor, lotic mesocosm experiments lasting about 2 months were conducted from 2006 to 2008. Herbicides (diuron) and fungicides (azoxystrobin, tebuconazole) were tested at environmental concentrations (sum of pesticides concentrations from 1.11 to 3.01 μg L^?1 for chronic pollutions and from 20.25 to 29.50 μg L^?1 for short-term acute pollutions). Diatom communities in artificial channels were analyzed by light microscopy using standard European methods. The various parameters structuring diatom communities were assessed, and colonization time appeared to be the most important. However, pesticide contamination was the second most important, and had a more significant impact on the composition of ecological guilds than on species composition. Some metrics did not display any significant trends (benthic/planktonic, colonial, pedunculate, pioneer), but others looked promising for use in pesticide contamination assessment: the abundances of motile guild, low-profile guild and mucous tubule diatoms all increased in contaminated channels, whereas high-profile diatoms showed the opposite trend. Some possible explanations, such as a protective effect of the exopolysaccharide matrix, can be advanced: diatoms living inside a mucous tubule may be shielded from dissolved pesticides, as are motile diatoms, which have a micro-habitat preference for thick matrices which also allows them to withstand higher levels of water contamination. In the same way, high-profile guild diatoms are exposed to dissolved pesticides to a greater extent, and this could explain their lower abundance in contaminated channels.     

Using fish guilds to assess community responses to temperature and flow regimes in unregulated and regulated Canadian rivers

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A multimetric diatom index to assess the ecological status of coastal Galician rivers (NW Spain)

There are many rivers in northwest Spain as a consequence of the mountainous landscape and the granitic geology subjected to Atlantic influences. Water and epilithic diatoms samples were collected at 72 sites in Galicia flowing into the Atlantic Ocean and Cantabrian Sea in summer 2002–2003 and spring 2004. These sites included minimally disturbed sites, defined as reference sites, and impacted sites which were influenced by different human pressures. We used the diatom assemblages to calculate diatom indices using the Omnidia software, but we also developed new metrics based on the similarity of species composition in reference sites. The response of the metrics was tested in relation to physicochemical variables. We developed a diatom multimetric index (MDIAT) as a combination of metric values. The sensitivity of the MDIAT to organic and nutrient stressors supports the use of this index to classify the ecological status of Galician rivers. The MDIAT showed higher correlations with some variables and nutrients than the individual metrics. According to the MDIAT, 69% of the sites sampled in Galician coastal rivers achieve good ecological status. The MDIAT has been developed specifically for Galician granitic rivers (NW Spain), and has been intercalibrated at the European level in the Central Baltic Rivers GIG. Our study validates the application of this multimetric index to evaluate the water quality in coastal Galician rivers.     

AusRivAS: using macroinvertebrates to assess ecological condition of rivers in Western Australia

1. AusRivAS (Australian River Assessment Scheme) models were developed, using macroinvertebrates as indicators, to assess the ecological condition of rivers in Western Australia as part of an Australia-wide program. The models were based on data from 188 minimally disturbed reference sites and are similar to RIVPACS models used in Britain. The major habitats in the rivers (macrophyte, channel) were sampled separately and macroinvertebrates collected were identified to family level. 2. Laboratory sorting of preserved macroinvertebrate samples recovered about 90% of families present when 150 animals were collected, whereas live picking in the field recovered only 76%. 3. Reference sites clustered into five groups on the basis of macroinvertebrate families present. Using seven physical variables, a discriminant function allocated 73% of sites to the correct classification group. A discriminant function based on seven physical and two chemical variables allocated 81% of sites to the correct group. However, when the same reference sites were re-sampled the following year, the nine variable discriminant function misallocated more sites than the seven variable function, owing to annual fluctuations in water chemistry that were not accompanied by changes in fauna. 4. In preliminary testing, the wet season channel model correctly assessed 80% of reference sites as undisturbed in the year subsequent to model building (10% of sites were expected to rate as disturbed because the 10th percentile was used as the threshold for disturbance). Nine sites from an independent data set, all thought to be disturbed, were assessed as such by the model. Results from twenty test sites, chosen because they represented a wide range of ecological condition, were less clear-cut. In its current state the model reliably distinguishes undisturbed and severely disturbed sites. Subtle impacts are either detected inconsistently or do not affect ecological condition.     

Evaluating the ecological status of rivers using an index of ecological distance: An application to diatom communities

Community structure changes with pollution or stress. In the Water Framework Directive, high ecological status through biological parameters is defined as a slight or minor deviation from the reference community, while the good status is defined as a small deviation.To assess the importance of this deviation, and then to measure the degradation of ecological status along a river, an index based on the concept of “ecological distance” between species was created and called ecological distance index (EDI). It was tested on diatom data from a pilot watershed (the Garonne river basin, South-West France).The results show a good correlation between the EDI and the IPS (Indice de Pollusensibilité Spécifique – specific pollusensitivity index – a diatom-based biotic index) ecological ratios, which means first that the EDI is a valuable indicator of ecological status, and that it can account for ecoregional specificities. This index can be applied to any communities (macro-invertebrates, fish, etc.), since: (i) typical reference communities are found for each river type; (ii) species are characterised then ranked by pollution sensitivity values.     

Using lichen biomonitoring to assess environmental justice at a neighbourhood level in an industrial area of Northern France

Environmental inequalities are based on the proximity of socio-economically disadvantaged populations to sources of environmental and public health risks, and have recently been extended to environmental contamination. We evaluated such inequalities using a novel approach, at the scale of neighbourhoods in the industrial area of Dunkerque, France, by associating an index of social disadvantage with environmental biomonitoring measurements.A Localised Disadvantage Index (LDI), which characterises the socio-economic status of populations at a neighbourhood level, was developed using an eco-sociological approach. The burdens of 18 trace elements (TE) were recently determined using samples of epiphytic lichens, collected within the study zone. A mean value of TE burden was modelled for each neighbourhood and an integrated index (Mean Impregnation Ratio, MIR) was generated to assess the level of multi-metallic contamination.LDI mapping reveals socio-economic disparities. The neighbourhoods situated near to factories are the most disadvantaged. Environmental maps reveal high contaminations in the vicinity of the industrial zones. The LDI is significantly correlated with the MIR, and with 16 of 18 TE. Significant differences in the level of contamination are observed between high- and low-deprived neighbourhoods.Our results uncover the presence of environmental inequalities. The most disadvantaged populations live in a strongly contaminated environment. We have pioneered the use of biomonitoring data and an integrated index of contamination for the prospection of environmental inequalities.     

Responses of the planktonic diatom Asterionella formosa Hassall to abiotic environmental factors in a reservoir complex (south-eastern France)

The River Durance and its main tributary, the Verdon, are both highly regulated rivers flowing in south-eastern France. The course of both rivers is interrupted by a series of reservoirs with quite different geographical, morphometric, climatic, hydrodynamic and chemical characteristics. The planktonic diatom Asterionella formosa Hassall, which has undesirable cyclic effects from the water management point of view, was studied in this complex of reservoirs located in the Mediterranean region. The results indicate that only the monomictic calcareous reservoirs show a bimodal pattern of Asterionella formosa abundance. The population dynamics of this algal species was found to depend on both the morphometric features and the hydraulic mode of management (retention time) used at each reservoir, as well as on the physical (temperature, suspended matter) and chemical (nitrogen, silica, calcium) characteristics of the water.     

应用稳定同位素测定贵州凤冈麻湾洞洞穴陆生动物的食物来源及营养级

以贵州凤冈麻湾洞洞穴生态系统为研究对象,运用δ¹³C、δ¹⁵N测定了洞穴动物及其有机碳源的同位素比值,分析了洞穴生态系统的营养级关系及洞穴动物食源。结果表明:洞内植物δ¹³C范围为-41. 78‰～-38. 80‰,较洞外植物低;δ¹⁵N范围为-1. 31‰～1.23‰,在洞外陆源有机质δ¹⁵N范围内;洞穴土壤有机质的δ¹³C范围为-31. 09‰～-24.95‰,δ¹⁵N范围为-1.08‰～7.72‰;洞穴动物δ¹³C范围为-30.41‰～-12.02‰,δ¹⁵N范围为2.07‰～8.94‰;洞穴土壤有机质对动物的食源贡献率超过72%,远高于植物对动物的食源贡献率,即洞穴土壤有机质是洞穴动物的主要食物来源。麻湾洞生态系统主要由4个营养层次组成:植物为第一营养层次;闪夜蛾、螺类、马陆类处于第二营养层次;裸灶螽、长头地蜈蚣处于第三营养层次;蜘蛛类处于第三或第四营养层次。即大部分同种(或同类群)...     

How ecological indicators construction reveals social changes—The case of lakes and rivers in France

Social and scientific factors are deeply enmeshed in each other within the development and the use of ecological indicators (EI). Yet low research has assessed which factors contribute to selecting ecological indicators on the long-term. This article proposes to study the historical construction of EI by examining ecological, political, and social background of specific places where EI were developed, in France on lakes and rivers. Our major findings in France were that ecological indicators were never optimised for the present market or political arena. Instead EI development was typically recycling previous tools that were elaborated for other purposes by environmentally committed outsiders, without regular funding. We found that regular funding for monitoring an EI was only provided when it matched an institution's goal. Beyond the geographically limited relevance of the case studies, these results therefore improve the theoretical framework we deploy when constructing or relying on indicators.     

Using stable isotopes to test for trophic niche partitioning: a case study with stream salamanders and fish

1. Stream salamanders and fish often co‐occur even though fish prey on and outcompete salamanders. However, the mechanisms that allow palatable salamanders to coexist with fish are unknown. 2. We tested mechanisms in the field that promote coexistence between Idaho giant salamanders (Dicamptodon aterrimus) and stream salmonid fishes in headwater streams. Previous research in this system indicated that salamander dispersal did not promote coexistence with fish. We tested the hypothesis that D. aterrimus shift their diet when they occur with fish, facilitating coexistence through local niche partitioning. 3. We used nitrogen and carbon stable isotopes to describe the trophic niche of D. aterrimus and fish in three co‐occurring populations of salamanders and fish and three populations of salamanders without fish. We used two approaches to quantify trophic niche partitioning with stable isotopes: 95% kernel density estimators and isotopic mixing models. 4. We found that salamanders and fish were generalists that consumed aquatic invertebrates primarily, but both species were also cannibalistic and predatory on one another. We also found no support for trophic niche partitioning as a coexistence mechanism because there were no differences in the trophic niche metrics among salamander populations with and without fish. 5. Although we did not identify mechanisms that facilitate salamander and fish coexistence, our empirical data and use of novel approaches to describe the trophic niche did yield important insights on the role of predator–prey interactions and cannibalism as alternative coexistence mechanisms. In addition, we found that 95% kernel estimators are a simple and robust method to describe population‐level measure of trophic structure.     

Two approaches using traits to assess ecological resilience: A case study on earthworm communities

The relation between biological diversity and ecosystem functioning is a central theme in ecology. Ecological traits of species are often regarded as a link between structure and function, and trait distributions in a community may change in response to environmental stressors. Likewise, resilience in a community may be derived from the diversity in traits and trait values relevant to a particular stressor. We combine two approaches to test this: a novel trait frequency analysis and a multivariate ordination approach. The two methods are applied on a case study of an earthworm community in a frequently flooded floodplain in the Netherlands. Periodic flooding in floodplains restricts population growth and recolonization of earthworms. The strategies employed by different earthworm species for coping with this stress can be described by a combination of ecological traits. From the literature we compiled 10 ecological traits for the earthworm species encountered along an inundation gradient in the Duursche Waarden floodplain area flanking the river IJssel. Trait frequency analysis showed a greater diversity at low elevation sites of traits considered to be associated to flood tolerance, suggesting greater community resilience to flooding. The ordination analysis using trait composition provided information on which trait classes in the community were related with the inundation stress. Results from both analyses showed that important traits in species to deal with flooding are active dispersal, high hydrophily, diapause and parthenogenetic reproduction. Thus, a further understanding of community resilience was gained by combining traditional ordination analysis with trait diversity analysis.     

Application of a self-organizing map to select representative species in multivariate analysis: A case study determining diatom distribution patterns across France

Ecological communities consist of a large number of species. Most species are rare or have low abundance, and only a few are abundant and/or frequent. In quantitative community analysis, abundant species are commonly used to interpret patterns of habitat disturbance or ecosystem degradation. Rare species cause many difficulties in quantitative analysis by introducing noises and bulking datasets, which is worsened by the fact that large datasets suffer from difficulties of data handling. In this study we propose a method to reduce the size of large datasets by selecting the most ecologically representative species using a self organizing map (SOM) and structuring index (SI). As an example, we used diatom community data sampled at 836 sites with 941 species throughout the French hydrosystem. Out of the 941 species, 353 were selected. The selected dataset was effectively classified according to the similarities of community assemblages in the SOM map. Compared to the SOM map generated with the original dataset, the community pattern gave a very similar representation of ecological conditions of the sampling sites, displaying clear gradients of environmental factors between different clusters. Our results showed that this computational technique can be applied to preprocessing data in multivariate analysis. It could be useful for ecosystem assessment and management, helping to reduce both the list of species for identification and the size of datasets to be processed for diagnosing the ecological status of water courses.     

Response of epilithic diatom assemblages to water pollution in rivers in the Tokyo Metropolitan area, Japan

1. During the spring of 1992, fifty-two quantitative diatom samples were collected from twenty-eight rivers located in the Tokyo Metropolitan area, Japan, to study the response of the diatom assemblages to water pollution (assessed using physical and chemical data determined monthly from April 1987 to March 1992). 2. Species composition was analysed by means of biotic indices (Pantle and Buck's saprobic index) and multivariate analyses [two-way indicator species analysis (TWINSPAN) for classification and canonical correspondence analysis (CCA) for ordination]. Species-abundance relationships were analysed using diversity indices (species richness, Shannon's diversity index and Pielou's evenness index) and rank-abundance patterns (rank-abundance curves). 3. CCA revealed two major gradients. The first corresponded to organic pollution and eutrophication. The second corresponded to variables related to geographical location. Four main station groups were determined by TWINSPAN. The location of the indicator species of groups 1–3 along the CCA axis 1 is consistent with their known pollution tolerance characteristics. Indicator species for group 4 had larger scores on CCA axis 2, and are representative of brackish water environments. 4. Species richness tended to be higher in the intermediate range of water pollution. Pielou's evenness index and Shannon's diversity index followed the same tendency but only weakly. 5. The rank-abundance patterns of diatom assemblages were more or less constant in all stations. The curves were very similar in shape, differing only in length and gradient (directly related to species richness and evenness, respectively). 6. The results of this study indicate that the response of diatom assemblages to environmental change can be observed in species compositional variation. Multivariate analyses and pollution indices revealed this response and are to be preferred to species diversity measures.     

The use of fish community structure as a measure of ecological degradation: a case study in two tropical rivers of India

Fish community structure and water chemistry of two tropical rivers of West Bengal, an eastern province of India, were studied for two annual cycles (January 2003-December 2004) and a higher degree of pollution was found in one river (the Churni) than in the other river (the Jalangi). This was reflected in the water quality as well as in fish community structure of the rivers. We observed that 63.6% of fish species appeared to have been eliminated from the polluted Churni river since 1983 in 20 years. For the protection of fish biodiversity and enhancement of fish production, a rational management program should be implemented for the Churni river.     

A quantitative method to assess the ecological indicator system's effectiveness: a case study of the Ecological Province Construction Indicators of China

The ecological indicator system (EIS) is widely used. It is vital to develop a scientific and rational EIS for practical application. Assessment of an EIS's effectiveness is important to understand the gaps between practical indicators and indicators that are considered theoretically ideal. In this paper we develop a conceptual method to quantitatively assess the effectiveness of a practical EIS by comparing it with the ideal EIS that is considered perfect by using three assessment indices: linkage, coverage and representation degrees. Linkage degree reveals the relevance of individual indicators to the ideal system. Coverage degree shows the integrity of the practical indicator system compared with the ideal system. Representation degree is the ultimate goal of the quantitative assessment and can detect the gap and overlap between the practical indicator system and the ideal one. Case study on the Ecological Province Construction Indicators (EPCI) proved that our conceptual method is useful to assess the effectiveness of a practical EIS. Compared with an ideal EIS, the EPCI has a high linkage and coverage degree but biased representation. Although the practical EIS covers most of the objectives detailed in the Fujian eco-province construction documents, many social development indicators are overlooked, including ecological culture and green consumption. Using the quantitative method will improve the practical application of an EIS by detecting its redundancy and weakness.     

Variation in tropical bird survival across longitude and guilds: a case study from the Amazon

Survival estimates of tropical birds have been used to examine life‐history variation across latitudes and dietary guilds. Here, we provide apparent survival estimates of 31 rainforest species from central Amazonian Brazil and compare our results with estimates from Ecuador, Peru (western Amazonia) and French Guiana (eastern Amazonia) to examine geographic variation in demography. Our averaged annual survival estimate for central Amazonian species (?= 0.59, SE = 0.10) was concordant with previously published estimates from the western Amazon (?= 0.58, SE = 0.02), and eastern Amazon (?= 0.63, SE = 0.06). Two predominate demographic patterns were detected across the study areas: within species, survival was highest or lowest in eastern or western Amazonia, but rarely in central Amazonia. The most striking demographic variation was exhibited by Pithys albifrons, for which apparent survival estimates were nearly twice as high in eastern Amazonia (?= 0.80, SE = 0.06) than in western Amazonia (?= 0.42, SE = 0.06) but intermediate in central Amazonia (?= 0.54, SE = 0.04). Although variation in survival may be associated with differences in life history characteristics, our analysis of flocking guild, body size, and nest architecture revealed only moderate differences in survival associated with nest architecture. These results suggest that geographic variation in population processes may be significant for widespread Amazonian species.     

The sensitivity of lizards to elevation: A case study from south-eastern Australia

Lizard distribution patterns were examined in relation to elevation in two undulating landscapes. We asked three specific questions: (1) Were different lizard species associated with particular elevations? (2) Did biological attributes of lizards (e.g. body size, colour, reproduction strategy, etc.) vary with elevation? (3) Did species richness of lizards vary with elevation? Field data were collected in two undulating production landscapes in south‐eastern Australia, approximately 100 km to the west of the Australian Capital Territory. Lizards were surveyed using 648 pitfall traps and 3840 m of drift fence. Both study landscapes were divided into 50 m elevation classes. For each elevation class, survey effort, the capture rate of individual species, and species richness were recorded. Correspondence analysis was used to sort lizards according to their altitudinal distribution profiles. Analysis of variance was used to examine if biological attributes of lizards were related to their altitudinal distribution profiles. Generalized linear modelling was used to relate elevation to the capture rate of individual species, and to species richness. Lizard species differed in their altitudinal preferences. Skinks, taxa with a Bassian distribution or distribution restricted to the Great Dividing Range, dark‐bodied species and viviparous species were more likely to inhabit high elevations. Elevation was significantly related to the capture rate of seven species, and ecologically similar species replaced one another as elevation increased. Species richness peaked significantly at intermediate elevations in both landscapes. We conclude that lizards were highly sensitive to elevation. Elevation changes of as little as 50 m may be related to a change in species richness or species composition. Future research should assess if reptiles in other undulating landscapes with a temperate climate are similarly sensitive to elevation. If so, conservation activities in these landscapes need to consider the full spectrum of topographic positions and elevations.