Les peuplements d'éphémèroptères de plécoptères et de trichoptères des ruisseaux acides et non acides du massif vosgien : première approche

Les peuplements d'Ephémèroptères, de Plécoptères et de Trichoptères de quatorze cours d'eau du massif vosgien granitique, ont été échantillonnés de mars 1988 à mars 1990. Les stations, au nombre de seize, ont été choisies en amont de toute agglomération et en dehors de zones d'activité agricole.Les mesures de pH, conductivité et aluminium total, ont établi que sept ruisseaux sont acides (pH moyens : 4,67-5,62), très faiblement minéralisés (conductivités moyennes : 17-21,5 µS/cm) et présentent des concentrations moyennes en aluminium total, comprises entre 221 et 387 µg/l.Les sept autres cours d'eau sont faiblement acides à neutres (pH moyens : 6,80-6,98), peu minéralisés (conductivité moyenne : 36-90 µS/cm) et montrent des concentrations moyennes eut aluminium variant de 41 à 78 µg/l.Seules 29 espèces ont été récoltées dans les ruisseaux acides alors que 93 l'ont été dans les cours d'eau non acides.Les Ephémèroptères se révèlent les plus sensibles aux conditions acides et disparaissent totalement. Parmi les Trichoptères, seuls les Polycentropodidae, les Rhyacophilidae et les Limnephilidae sont encore présents dans les ruisseaux acides. Alors que les Plécoptères Filipalpes sont bien représentés, certaines espèces étant même très abondantes, les Plécoptères Sétipalpes ne sont plus récoltés dans les cours d'eau acidifiés, à l'exception de Siphonoperla torrentium.Acidification of freshwaters has become a serious problem in certain parts of the Vosges Mountains (Northeastern France). Aquatic organisms at all major levels are affected by decreased pH. As the Ephemeroptera, Plecoptera and Trichoplera are a significant par of the macrobenthos in mountain streams, the objective of this preliminary study was to determine how the physico-chemical environment in acidified running waters affects the qualitative composition of mayflies, stoneflies and caddis-flies communities compared with non acidified streams and to evaluate the reliability and possible use of the taxonomic groups as indicators of the extent of acidification.A biological survey of fourteen streams was conducted in the Vosges mountains from March 1988 to March 1990. The areas investigated lie on granitic bed-rock and soils in the process of podzolisation. The sampling sites (sixteen), at altitudes of 600 to 1020 meters a.s.l. were located above built-in and agricultural areas thus avoiding organic pollution. The streams drain forested catchments regarded as sensitive to acid inputs and affected by forest decline. Silver fir (Abies alba), Norway spruce (Pecea abies) and European beech (Fagus sylvatica) are dominant.Larvae and pupae of Ephemeroptera, Plecoptera and Trichoptera were collected by band picking and Surber sampler (mesh aperture 350 µm). Adults were collected with an insert net by beating bushes and trees or sweeping low herbage near streams. A long-handled net was required for high-flying Ephemeroptera and Trichoptera. Organisms were preserved in 5 % formalin or 70 % ethanol.The pH was measured in the field using a specific glass electrode for low ionic solutions, compensated for temperature. Water samples were acidified for total aluminium analysis. Determination of aluminium was performed using an atomic absorption spectrophotometer equipped with a graphite furnace. Conductivity was measured in the laboratory al 20 °C.Determination of pH revealed that acidification occurred et seven sites (sampling sites n° 8 to 16). Six were strongly acidic (mean pH : 4.7-5.2) and one moderately acidic (mean pH : 5,6). In such streams mean total aluminium ranged from 221 µg/1 to 387 µg/1 and mean conductivity from 17,0 µS/cm to 21.5 µS/cm. Minimum pH and maximum aluminium values were recorded during snowmelt or rein event. In all these streams the fish population (Salmo trutta fario) has completely disappeared.Others streams (sampling sites n° 1 to 7) went from slightly acidic to neutral with a range pH between 6.8-7.0 and were characterized by average total aluminium varying from 41 µg/1 to 78 µg/l and average conductivity from 36 µS/cm to 90 µS/cm. These streams have been considered as reference for non acidified running waters.The number of species occurring in acidified streams contrasted markedly with those of the non acidified streams. Specific richness of Ephemeroptera, Plecoptera and Trichoptera are reduced in acidic waters. Only twenty-nine species were found in acidic streams, whereas a total of ninety-three species were collected in non acidic streams.EphemeropteraIn the reference streams, the Ephemeroptera fauna was rich and diverse with twenty taxa. Some species, for example Epeorus sylvicola, Baetis alpinus and B. rhodani were very common and widespread. In contrast, in acidic water only one species, Baetis vernus, was actually present (3 larvae).TrichopteraThirty-eight species of caddis flies were found in non acidic streams. Hydropsychidae (hydropsyche sp) Philopotamidae (Philopotamus ludificatus, P. montanus, Wormaldia sp) and Glossosomatidae (Glossosoma conformis, Agapetus sp) were the organisms most commonly present.In acidic streams, eleven species were food. Rhyacopyhilidae (Rhyacophlla obliterata, R. potamoides, R. praemorsa), Polycentropodidae (Plectrocnemia sp, P. conspersa) and Limnephilidae (Drusus annulatus, D. discolor, Caetopterygopsis maclachlani, Chaelopteryx villosa, Anitella sp) were among the most abundant taxa.PlecopteraIn acidic streams, taxonomic richness (17 species) was about 50% lower than those obtained in the non acidic streams. The common species Perla marginata, Perlodes microcephala and Isoperla oxylepis were not listed when pH was below 5.6. At the opposit, some species were dominant and very abundant. For example, Brachyptera seticornis, was dominant in April, Leuctra nigra in May, Siphonoperla torrentium in June and Leuctra cingulala in July.The sensitivity of organisms towards to acidification appeared to be different among these groupe of aquatic insects. Three types of responses can be distinguished in relation with pH and/or associated factors :- High sensitivity of Ephemeroptera, which have completely disappeared- High sensitivity of most Trichoptera families except the following : Polycentropodidae, Rhyacophilidae and Limnephilidae.- Tolerance of Plecoptera filipalpia which were sometimes very abundant, but disappearance of Plecoptera Setipalpia except for Siphonoperla torrentium.This analysis showed that many species of mayflies, stoneflies and caddis flies do not tolerate low pH (and/or) associated with low conductivity and elevated aluminium concentrations. Because the biological response is the result of present and post environmental situations, we suggest the use of these taxa as indicators of acidification in running waters, particularly when a restricted number of physico-chemical measurements is insufficient to appreciate the acidification level, as during low flow periods or during periodes of no acid stress.Nevertheless, to be considered as a useful indicator of pollution in general and acidification in particular, a taxa (species, genera or family) should be widespread, relatively abundant, present all the year round, very sensitive to the studied factor and easy or relatively easy to identity.For example, in unpolluted streams in the Vosges Mountains, Epeorus sylvicola, Perlodes microcephala, Hydropsyche sp, Philopotamus sp seem to fit these criteria.However, in evaluating aquatic organisms as indicators of pollutional conditions, great caution is necessary because knowledge of the ecological requirements of the species is essential, several ecologic conditions other than the presence of a pollutant may limit the distribution of certain species. For this reason, the benthic macrofauna of a more significant number of sites of different chemical and physical characteristics should be collected

L'acidification des torrents vosgiens. Mise en évidence. Impact sur les populations de macroinvertébrés

Les auteurs donnent les résultats d'une étude physico-chimique et biologique portant sur quatre torrents situés sur le versant lorrain des Vosges. Les stations étudiées sont placées en amont de toute agglomération et dans des secteurs non perturbés par l'activité agricole. L'assise rocheuse de nature siliceuse est granitique. La différence dans la composition des granites et leur altération pourraient être à l'origine des différences physico-chimiques observées entre torrents situés dans un même secteur.La présence permanente ou temporaire d'eaux acides appartenant au crénon et au rhitron a été établie. Cette acidité s'accompagne de concentrations élevées en aluminium (Al total > 200 µg/l). Une enquête piscicole et la réalisation de pêches électriques ont révélé l'absence de salmonidés dans les cours d'eau acidifiés en permanence, alors que leur présence est connue antérieurement. L'existence d'épisodes acides lors de la fonte des neiges et des pluies printanières a été démontrée; les auteurs retiennent les retombées acides comme cause de l'acidification des eaux de surface. Ces événements d'ordre hydrométéorologique sont caractérisés par l'augmentation des concentrations en H+, NO3-, SO42- et aluminium, ainsi que par une baisse des ions HCO3-, dans les eaux torrenticoles. Les macroinvertébrés benthiques intègrent ces épisodes et l'étude comparative de leurs populations montre des modifications apparaissant dans les secteurs acidifiés par rapport aux secteurs non perturbés. L'intégration par les invertébrés benthiques des conditions physico-chimiques se traduit notamment par la disparition des Ephéméroptères, et par un appauvrissement de la diversité taxonomique des Plécoptères, Trichoptères et Coléoptères.A biological and physico-chemical survey of four streams has been conducted in the Vosges Mountains. The areas investigated have granitic bed rock and soils in the process of podzolisation; they are regarded as sensitive to inputs of strong acids. The streams drain forested catchments that are affected by decline of the forests Coniferous trees (Abiea alba, Picea abies) are dominant.The sampling sites were located above constructed and agricultural areas (645-685 metres above sea level) thus avoiding organic pollution. Samples of invertebrate fauna in the streams were collected using a surber-type sampler. The presence of fish (Salmo trutta fario) was determined by electro-fishing.To determine water chemistry, pH, Ca2+ , Mg2+ , K+, SO42-, NO3-, total dissolved aluminium, alcalinity (T.A.C.) and HCO3-/SO42- were measured. The permanent or occasional presence of acidic streamwaters was established. Acidification occurred in all streams during snow melting and rainstorms.During these hydrometeorological events, characteristically low pH levels (pH < 5.5), low alkalinity associated with high concentrations of aluminium, nitrates and sulfates, occurred in the water. These are critical periods for aquatic organisms owing to the toxicological effects of low pH and high concentrations of aluminium.Two streams (the "Rouge-Rupt" and the "Grand-Rupt") did not contain trout.Diversity and abundance of benthic macroinvertebrates are reduced with increasing acidity. Only 17 taxa were found in the most acidic stream (mean pH : 4.68), whereas 51 taxa were found in the one with less acidity. Likewise, in the less acidic river, abundance was more than three times higher (933 ind/m2) than in the one with most acidity (295 ind/m2). Ephemeroptera were absent when the pH was below 5.9. This order of aquatic insects seems to be the most sensitive to acidification.The benthic macroinvertebrate community also contained less Trichoptera. Only some Limnephilidae and the genera Plectrocenemia and Rhyacophila were common in acidic streamwaters and seemed to tolerate the acidification process.The Plecoptera dominated benthic communities in acidified streams. Nemouridae, Capniidae and Leuctridae were common and abundant. However, apart from Chloroperla sp., the Setipalpia were absent.A decrease in the diversity and abundance of Coleoptera was observed when the pH was lower than 5.9. The only beetle found in all the streams was Heldes sp.Diptera, Oligochaetes and Flatworms occurred in all four streams and did not present any difference in their distribution when the pH was low.Knowledge of the biology and ecology of the species appears essential in order to understand the impact of acidification on macroinvertebrates.The possibility that some species can carry out their development cycle in periods of no acid stress, thus being protected from the harmful effect of acidification, is suggested. In contrast, other species are undoubtedly partly or totally eliminated, owing to their presence at a sensitive development stage during periods of intense acidification

Leaf litter breakdown budgets in streams of various trophic status: effects of dissolved inorganic nutrients on microorganisms and invertebrates

1. We investigated the effect of trophic status on the organic matter budget in freshwater ecosystems. During leaf litter breakdown, the relative contribution of the functional groups and the quantity/quality of organic matter available to higher trophic levels are expected to be modified by the anthropogenic release of nutrients. 2. Carbon budgets were established during the breakdown of alder leaves enclosed in coarse mesh bags and submerged in six streams: two oligotrophic, one mesotrophic, two eutrophic and one hypertrophic streams. Nitrate concentrations were 4.5–6.7 mg L−1 and the trophic status of each stream was defined by the soluble reactive phosphorus concentration ranging from 3.4 (oligotrophic) to 89 μg L−1 (hypertrophic). An ammonium gradient paralleled the phosphate gradient with mean concentrations ranging from 1.4 to 560 μg L−1 NH4-N. The corresponding unionised ammonia concentrations ranged from 0.08 to 19 μg L−1 NH3-N over the six streams. 3. The dominant shredder taxa were different in the oligo-, meso- and eutrophic streams. No shredders were observed in the hypertrophic stream. These changes may be accounted for by the gradual increase in the concentration of ammonia over the six streams. The shredder biomass dramatically decreased in eu- and hypertrophic streams compared with oligo- and mesotrophic. 4. Fungal biomass increased threefold from the most oligotrophic to the less eutrophic stream and decreased in the most eutrophic and the hypertrophic. Bacterial biomass increased twofold from the most oligotrophic to the hypertrophic stream. Along the trophic gradient, the microbial CO2 production followed that of microbial biomass whereas the microbial fine particulate organic matter and net dissolved organic carbon (DOC) did not consistently vary. These results indicate that the microorganisms utilised the substrate and the DOC differently in streams of various trophic statuses. 5. In streams receiving various anthropogenic inputs, the relative contribution of the functional groups to leaf mass loss varied extensively as a result of stimulation and the deleterious effects of dissolved inorganic compounds. The quality/quantity of the organic matter produced by microorganisms slightly varied, as they use DOC from stream water instead of the substrate they decompose in streams of higher trophic status

Global patterns and drivers of ecosystem functioning in rivers and riparian zones

River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth's biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented "next-generation biomonitoring" by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.peerReviewe

Hyperventilation and loss of hemolymph Na+ and Cl- in the freshwater amphipod Gammarus fossarum exposed to acid stress: a preliminary study

International audienc

Haemolymph [Na+] and [Cl-] loss in Gammarus fossarum exposed in situ to a wide range of acidic streams

International audienc

Short-term physiological responses to a severe acid stress in three macroinvertebrate species: A comparative study

International audienc

Cotton-strip assays: Let's move on to eco-friendly biomonitoring!

There is increasing recognition that functional bioindicators are needed for ecosystem health assessments. In this perspective, cotton strip assays are widely considered as a standard method to account for organic matter decomposition in streams. However, cotton cultivation and manufacture raise both environmental and societal dramatic issues that are e in our opinion e irreconcilable with the objectives of bioindication. In this study, we assessed the relevance of four alternative e eco-friendly e textiles (made of organic cotton, hemp and linen) by comparing their chemical composition and degradation rates in six streams. Chemical composition exhibited low variations among textiles, but contrasted sharply with the expectation that cotton is mostly composed of cellulose. Moreover, surprisingly high nutrient (0.49% N) contents occurred in the conventional cotton strips compared with the organic textiles (N &lt; 0.12%). All textiles provided similar degradation rates across the six streams, meaning that they could be interchangeably used as alternatives to conventional cotton strips.We thus call for the adoption of such ethical and eco-friendly tools as 'next-generation' indicators for the functioning of stream ecosystem

Physiological recovery from episodic acid stress does not mean population recovery of Gammarus fossarum

International audienc

ASPIRE : un cadre méthodologique pour l'appréciation du succès des projets d'ingénierie et de restauration écologiques : application à une opération de restauration d'une zone humide d'altitude

The high number of dimensions of ecological engineering and restoration projects contributes to their values but also to their assessment issues. The objective of the ASPIRE (Assessment of Ecological Engineering and Restoration Projects) framework is to provide a tool delivering a global project assessment, while also providing detailed scores for each of its dimensions. ASPIRE is composed of 3 levels: variables, objectives and the project. Variables are measured on the study site. Their values are normalized to range between 0 and 1. Objectives correspond to a variable list, and their score are the weighted mean of variables normalized values. The final project score is the weighted mean of the objectives scores. Scores attributed to variables are relative to references, therefore they can be compared to each other's, and objectives and scores can also be compared to each other's. While being calculated on the same study site measurements, variables and objectives weighting allows highlighting different visions of the project (for instance, from various stakeholders). ASPIRE is illustrated by its application on a mountain wetland restoration project.Du fait de la multiplicité des dimensions des projets de restauration, peu de retours sont réalisés pour évaluer leur réussite. Ces retours sont pourtant nécessaires à l'élaboration de projets futurs plus efficaces. Le cadre méthodologique ASPIRE a pour but de permettre une appréciation globale du projet en s'appuyant notamment sur les variables (mesures prises sur le terrain), les objectifs de la réhabilitation et le projet en lui-même