Are Amphipod invaders a threat to the regional biodiversity? Conservation prospects for the Loire River

The impact of invasions on local biodiversity is well established, but their impact on regional biodiversity has so far been only sketchily documented. To address this question, we studied the impact at various observation scales (ranging from the microhabitat to the whole catchment) of successive arrivals of non-native amphipods on the amphipod assemblage of the Loire River basin in France. Amphipod assemblages were studied at 225 sites covering the whole Loire catchment. Non-native species were dominant at all sites in the main channel of the Loire River, but native species were still present at most of the sites. We found that the invaders have failed to colonize most of tributaries of the Loire River. At the regional scale, we found that since the invaders first arrived 25 years ago, the global amphipod diversity has increased by 33% (from 8 to 12 species) due to the arrival of non-native species. We discuss the possibility that the lack of any loss of biodiversity may be directly linked to the presence of refuges at the microhabitat scale in the Loire channel and in the tributaries, which invasive species have been unable to colonize. The restoration of river quality could increase the number of refuges for native species, thus reducing the impact of invader

Feeding choice and predation pressure of two invasive gammarids, Gammarus tigrinus and Dikerogammarus villosus, under increasing temperature

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Coupling groundwater modeling and biological indicators for identifying river/aquifer exchanges.

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Diversity of aquatic macroinvertebrates in relationship with the environmental factors of a lotic ecosystem in tropical region: the Sô river in South-East of Benin (West Africa)

International audienceThe present study was aimed to study the diversity of aquatic macroinvertebrate populations in relation to the abiotic parameters of the Sô River. For this purpose, aquatic macroinvertebrates were sampled monthly between February 2016 and April 2017 on 12 sampling stations and in various habitats along the Sô River. Similarly, twenty environmental variables were measured to assess the environmental characteristics of Sô river. The recorded fauna consists of 2053 individuals corresponding to 44 families and 61 taxa belonging to three main zoological groups (Arthropods, Molluscs, Annelids). The stand population showed that Coleoptera (17.06%), Basomatophora (14.19%), Heteroptera (11.37%), Odonata (10.26%), Mesogasteropoda (9.01%) and Decapoda (9%) are the most abundant orders. Another oders constitute only a small fraction of the total fauna harvested. The redundancy analysis performed shows that abiotic parameters that strongly influence taxonomic diversity and taxon abundance are: current velocity, nitrogen and phosphorus compounds, mineralization parameters and canopy

Evaluation de l’Effet des Eaux Usées Industrielles sur la Qualité de l’Eau de la Rivière Klou au Centre du Bénin

La présente étude a pour objectif d’évaluer l’impact des eaux usées industrielles sur la qualité de l’eau de la rivière Klou. Pour cela, des prélèvements d’eau ont été effectués avec une fréquence mensuelle sur des stations témoins et exposées. Les analyses physico-chimiques et le calcul de l’indice de Pollution Organique (IPO) ont été effectués. En période pluvieuse, les valeurs des paramètres physico-chimiques (pH, conductivité, TDS, ammonium, DBO5, nitrate, nitrite et orthophosphates) etaient faibles. De plus, les fortes valeurs des paramètres étudiés sont observées sur les stations plus exposées. Les résultats de l’analyse en composantes principales (ACP) sur les paramètres physico-chimiques ont révélé deux groupes  de stations. Le premier est constitué des deux stations témoins caractérisées par les faibles valeurs des paramètres étudiés alors que le second est composé des stations plus exposées et celles de l’aval avec les fortes valeurs des paramètres étudiés. L’indice de pollution organique a révélé une pollution modérée au niveau des stations témoins et une pollution organique forte et très forte respectivement au niveau des stations plus exposées et celles de l’aval. Il est nécessaire alors de mettre en place une politique de  restauration de la qualité écologique des eaux de cette rivière et des centres d’épuration opérationnels et efficaces.   The objective of this study was to assess the impact of industrial wastewater on the water quality of the Klou River. For this purpose, water sampling was conducted with a monthly frequency on control and exposed stations. Physico-chemical analyses and the calculation of the Organic Pollution Index (IPO) were carried out. In rainy periods, the values of the physico-chemical parameters (pH, conductivity, TDS, ammonium, BOD5, nitrate, nitrite and orthophosphates) were low. Moreover, the high values of the studied parameters were observed at the more exposed stations. The results of the principal component analysis (PCA) on the physico-chemical parameters revealed two groups of stations. The first consists of the two control stations characterized by low values of the studied parameters, while the second consists of the more exposed stations and those downstream with high values of the studied parameters. The organic pollution index revealed moderate pollution at the control stations and strong and very strong organic pollution respectively at the more exposed stations and those downstream. It is then necessary to put in place a mechanism to restore the ecological quality of the waters of this river and operational and effective purification centres

Global Scale Variation in the Salinity Sensitivity of Riverine Macroinvertebrates: Eastern Australia, France, Israel and South Africa

Salinity is a key abiotic property of inland waters; it has a major influence on biotic communities and is affected by many natural and anthropogenic processes. Salinity of inland waters tends to increase with aridity, and biota of inland waters may have evolved greater salt tolerance in more arid regions. Here we compare the sensitivity of stream macroinvertebrate species to salinity from a relatively wet region in France (Lorraine and Brittany) to that in three relatively arid regions eastern Australia (Victoria, Queensland and Tasmania), South Africa (south-east of the Eastern Cape Province) and Israel using the identical experimental method in all locations. The species whose salinity tolerance was tested, were somewhat more salt tolerant in eastern Australia and South Africa than France, with those in Israel being intermediate. However, by far the greatest source of variation in species sensitivity was between taxonomic groups (Order and Class) and not between the regions. We used a bayesian statistical model to estimate the species sensitivity distributions (SSDs) for salinity in eastern Australia and France adjusting for the assemblages of species in these regions. The assemblage in France was slightly more salinity sensitive than that in eastern Australia. We therefore suggest that regional salinity sensitivity is therefore likely to depend most on the taxonomic composition of respective macroinvertebrate assemblages. On this basis it would be possible to screen rivers globally for risk from salinisation

Effects of intense agricultural practices on heterotrophic processes in streams

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Short-term effects of macrophyte removal on aquatic biodiversity in rivers and lakes

Mass development of macrophytes is an increasing problem in many aquatic systems worldwide. Dense mats of macrophytes can negatively affect activities like boating, fishing or hydropower production and one of the management measures often applied is mechanical removal. In this study, we analyzed the effect of mechanical macrophyte removal on phytoplankton, zooplankton, and macroinvertebrate (pelagic and benthic samples) assemblages. Our study covered five sites in four countries in Europe and Africa with highly variable characteristics. In all sites, dense mats of different macrophyte species (Juncus bulbosus in a river in Norway; a mix of native macrophytes in a German river, Elodea nuttallii in a lake in Germany, Ludwigia spp. In a French lake and Pontederia crassipes in a South African lake) are problematic and mechanical removal was applied. In every country, we repeated the same BACI (Before-After-Control-Impact) design, including “before”, “one week after”, and “six weeks after” sampling in a control and an impact section. Repeating the same experimental design at all sites allowed us to disentangle common effects across all sites from site-specific effects. For each taxonomic group, we analyzed three structural and three functional parameters, which we combined in a scoring system. Overall, the removal of macrophytes negatively affected biodiversity, in particular of zooplankton and macroinvertebrate assemblages. In contrast, plant removal had positive effects on the phytoplankton assemblages. Effects were more pronounced one week after removal than six weeks after. Consequently, we suggest a stronger consideration of the effect of plant removal on biodiversity to arrive at more sustainable management practices in the future.acceptedVersio

Les crustacés aquatiques souterrains d’Afrique et de Madagascar : bilan et enjeux

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Intra and Inter-Population Morphological Variation of Shape and Size of the Chilean Magnificent Beetle, Ceroglossus chilensis in the Baker River Basin, Chilean Patagonia

The alteration of habitat generates different degrees of stress in insects. It has been suggested that the degrees of phenotypic disturbances reflect the ability of an individual to overcome the effects of stress. The Baker River Basin in the Aysén Region, Chilean Patagonia has a very fragmented landscape, due to the destruction of the native forest and the use of land for agriculture and animal husbandry. This alteration should generate different degrees of disturbances in the insect communities, whose effects may be quantified by geometric morphometric tools. We analyzed morphological differences in 244 males and 133 females of the the Chilean magnificent beetle, Ceroglossus chilensis (Eschscholtz) (Coleoptera: Carabidae) collected in January, 2007, in mixed forests of Nothofagus dombeyi Mirbel (Ørsted) (Fagales: Nothofagaceae) and N. nitida Hofmus and in Second-growth forest of N. pumilio (Poepp. & Endl.) Krasser. Males were generally wider in the pronotum, while females had wider abdominal sternites. Although there were significant differences in shape and size between mature forests and second-growth forest, these were less significant among the sites within each type of vegetal formation. Individuals had more shape variations in the mature forest. We suggest that differences in shape are due at least in part to the isolation of the habitat. The differences found between sexes raises the question of how morphological variations and sexual dimorphism may be affected spatially by natural selection