Papers by Christophe Piscart
Frontiers in environmental science, Feb 27, 2024
The removal of the two dams on the Sélune River since 2019 has led to profound changes in the aqu... more The removal of the two dams on the Sélune River since 2019 has led to profound changes in the aquatic ecosystem. Lentic habitats bordered by forest had shifted to new conditions (running water and sparsely vegetated riverbanks) therefore shaping organisms' assemblies. We studied how the reestablishment of aquatic lotic habitats in interaction with riparian vegetation could mediate the restoration of important ecological functions in the new river. Six stations located along the river continuum were surveyed for 3 years after dam removal: two control stations upstream the former reservoir, three restored stations within the former reservoir, and one control station downstream. We monitored physico-chemical characteristics, phytobenthos biomass and the river's benthic metabolism, and assessed the functional composition of macroinvertebrate communities. We compared the recorded variables among upstream, downstream and restored sampling stations. We observed a rapid recolonization by invertebrates, but a still low phytobenthic primary production in restored stations. Such a low primary productivity was also reflected in the functional composition of invertebrate communities. Three years after dam removal, there was still a significant time lag between communities recovery and expected ecosystem functioning restoration. We observed a quick colonization by aquatic running-water invertebrate communities of new lotic reaches, but a slower recovery of important ecological functions rates such as those observed in control stations.
Ecosystems, Jun 25, 2019
Plant litter decomposition is an essential ecosystem function in temperate streams. Both riparian... more Plant litter decomposition is an essential ecosystem function in temperate streams. Both riparian vegetation and decomposer communities are major determinants of the decomposition efficiency and the interactions occurring within litter mixtures. However, the extent to which such litter mixture interactions are affected by combined shifts in litter traits and decomposer community is not well understood. We used leaf litter from 10 European tree species in order to study litter decomposition and litter mixture effects occurring in two-species litter mixtures in a temperate forested stream of northwestern France. The study distinguished between (i) decomposition involving microorganisms alone or together with invertebrates, and (ii) decomposition involving litter mixtures of similar or dissimilar nutrient content. Increasing mean litter nutrient concentration favored both microbial activity and litter decomposition rate. Surprisingly, the highest litter mixture effects occurred in mixtures containing two nutrient-rich litters and occurred mainly in macroinvertebrate presence. Both the "mass-ratio hypothesis", expressed as the community weighted mean traits (TraitCWM), and the "niche complementarity hypothesis", expressed as the functional dissimilarity of litter traits (TraitFD), contributed to explain litter mixture effects. However, TraitCWM was found to be a better predictor than TraitFD. Finally, when evaluating the individual contributions of litter nutrients, calcium and magnesium appeared as important drivers of litter mixture effects. Our findings suggest that the mass-ratio hypothesis overrules the niche complementarity hypothesis as a driver of litter diversity effects. Our study highlights the key importance of macroinvertebrates and of leaf nutrients, such as Ca and Mg, which are often neglected in decomposition studies in streams.
Crustaceana, 2013
Samplings in the area of Oum El Bouaghi yielded a new species, E. haraktis, belonging to the Echi... more Samplings in the area of Oum El Bouaghi yielded a new species, E. haraktis, belonging to the Echinogammarus simoni-group, in springs and wadis located on Mount EL Hamra in northeastern Algeria. The species is mainly characterised by the high number of long setae on the second antenna of both sexes, the lack of long setae on the basal segment of pereiopod 7 and on the exopodal segment of the uropod 3, and a much reduced second exopodal segment of uropod 3. Key words. -Freshwater Amphipoda, new species. North Africa, Oum El Bouaghi RESUME Des échantillonnages dans la région d'Oum El Bouaghi ont mis en évidence une nouvelle espèce, E. haraktis appartenant au groupe Echinogammarus simoni, dans des sources et des Oueds localisés sur le Mont El Hamra, au nord-est de l'Algérie. L'espèce est principalement caractérisée par la présence de nombreuses et longues soies sur la deuxième paire d'antenne des deux sexes, l'absence de longues soies sur le segment basai des périopodes 7 et sur l'exopodite de l'uropode 3, et un second segment de l'exopodite de l'uropode 3 très réduit.
Aquatic Invasions, 2008
Since the first observation in September 2005 of Gammarus tigrinus in Brittany (Western France), ... more Since the first observation in September 2005 of Gammarus tigrinus in Brittany (Western France), the species' range has expanded slowly. By September 2008, the range of G. tigrinus expanded > 63.6 km to the North and 60.4 km to the West of that observed in 2005. G. tigrinus is thought to be responsible for the replacement of native Gammarus pulex. The relatively slow expansion rate of G. tigrinus in Brittany may result from either a low frequency of ship traffic, a known vector for the species, or from the species' slow acclimatisation to brackish waters. A number of simulated invasion scenarios are presented for the future dispersal of G. tigrinus in Brittany.
An annotated checklist of freshwater stygobiotic crustaceans of Africa and Madagascar
Crustaceana, 2012
ABSTRACT In this study a checklist of the stygobiotic crustaceans specifically for Africa is prov... more ABSTRACT In this study a checklist of the stygobiotic crustaceans specifically for Africa is provided for the first time. Several nomenclatorial and taxonomic changes, as well as many new species or localities, have been included in the list since the publication of Stygofauna Mundi (Botosaneanu, 1986), which deeply modifies our knowledge on the biogeography of Africa. The annotated checklist comprises 280 stygobiotic species of crustaceans belonging to 9 orders, 32 families and 103 genera. Information about the endemism and the biogeographical distribution is provided for each of the systematic orders. Cette étude fournit pour la première fois une liste faunistique des crustacés stygobies d'Afrique. Plusieurs modifications dans la nomenclature et la taxinomie et de nombreuses espèces ou localités nouvelles, qui ont profondément modifié notre connaissance de la biogéographie du continent africain, ont été ajoutées à cette liste depuis la publication de Stygofauna Mundi (Botosaneanu, 1986). La liste faunistique annotée comprend 280 espèces de crustacés stygobies appartenant à 9 ordres, 32 familles et 103 genres. Des informations concernant l'endémisme et la distribution biogéographiques ont également été fournies pour chaque ordre systématique.
Habitat heterogeneity influences the response of microbial communities to severe low-flow periods in alluvial wetlands
Freshwater Biology, Dec 10, 2013
ABSTRACT * Microbial communities play a central role in the functioning of freshwater ecosystems,... more ABSTRACT * Microbial communities play a central role in the functioning of freshwater ecosystems, but the impact of severe low flow on microbial processes at the floodplain scale is largely unexplored, especially in terms of patterns in decline of water level. The differential responses of benthic and interstitial microbial communities are also unknown. * We explored the structural and functional responses of bacterial and fungal communities to severe low-flow periods at the surface and deep in the sediment of three types of wetland, namely running water, upwelling zones and isolated pools. * The different wetland types exhibited distinct microbial communities but the low-flow period induced homogenisation of community composition among wetland types. Despite a convergence in microbial community composition, the response of microbial processes differed among wetland types during the low-flow period: a decrease in biomass and activity in running water and upwelling sites contrasted with an increase observed in isolated pools. * Microbial communities and processes deep in the sediment appeared less affected by the low-flow period and wetland type, but were not insensitive. Homogenisation of community compositions at 50 cm depth was observed 1 month after the low-flow period, suggesting drivers distinct from those at the surface. Our results demonstrate the predominant effect of environmental conditions on rates of microbial processes as opposed to community composition. * Wetland heterogeneity, in terms of modalities of water level decrease, seems to be important for the maintenance of microbial processes at the floodplain scale in the context of increasing frequency and severity of low-flow periods.
Hydrobiologia, Jun 17, 2015
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Chemosphere, Dec 1, 2016
S-metolachlor (SMOC) and deethylatrazine (DEA) toxicities on non-target crustaceans. SMOC and DEA... more S-metolachlor (SMOC) and deethylatrazine (DEA) toxicities on non-target crustaceans. SMOC and DEA are more toxic to surface water species than groundwater one. Temperature rise did not affect SMOC toxicity but increased its potency. Joint action predictability by Concentration Addition -Independent Action models. Significance of species ecological group in risk assessment procedures.
Limnologica, May 1, 2011
Because of its geographic and economic position, the Western part of Europe and France is prone t... more Because of its geographic and economic position, the Western part of Europe and France is prone to biological invasions. Among the aquatic species non-native to France, a high proportion of these species are considered to be salt-tolerant. To verify this assumption, we compared the salinity tolerance of 18 native and non-native species in France in order to determine whether the introduced non-native species are more salt-tolerant than the native ones. Contrary to our expectations, our study shows that both native and non-native macroinvertebrate species from the same taxonomic group which had originated from within Eurasia had very similar salinity tolerance. Our results show that species originate from outside Eurasia (introduced by the ballast or drinking water on ships) were more salt tolerant than native from France and non-native species originated from Eurasia. Thus, derivation of the acute test of the salinity tolerance in native ranges may give good indications of their potential ability to survive during the translocation by shipping from the area of origin to another area. Our approach does provide empirical evidence for potential of non-native species to survive translocation in saline water using standard, quick and inexpensive protocols.
Faune des eaux souterraines du Bénin : un nouveau champ de recherches
HAL (Le Centre pour la Communication Scientifique Directe), Sep 27, 2016
International audienc
Influence d’un double barrage sur la dynamique saisonnière des communautés de phytoplancton et de microphytobenthos
HAL (Le Centre pour la Communication Scientifique Directe), Sep 27, 2016
International audienc
HAL (Le Centre pour la Communication Scientifique Directe), 2006
Salinization has been disturbing increasing numbers of inland waterways, and new analytical tools... more Salinization has been disturbing increasing numbers of inland waterways, and new analytical tools are needed to survey water quality and to assess the impact of salinization. Researchers have developed new protocols that reduce the number and type of samples required to reduce the cost of existing assessment methods. Our study contributes to this effort with the primary objective of identifying a single, unique river-bottom substrate that could be sampled to detect the impact of rising salinity on macroinvertebrate assemblages. We hoped to define a new concept of sentinel substrate, a substrate with an invertebrate assemblage that would signal an environmental impact (in this case increasing salinity) and that could be used at the site scale to assess that impact. We worked on the Meurthe River, which presents a significant salinity gradient (from 0.2 to 2.6 g/L) over a 19-km section of river in which all other physicochemical variables remain stable. We sampled substrates present at each of 4 sites along the salinity gradient in 2002 and described the effects of rising salinity on the structure (richness, diversity, and dominance) of the macroinvertebrate assemblage in each substrate type. Only the assemblage in pebbles adequately reflected site-level responses. Moreover, only assemblages in pebbles satisfied important criteria such as widespread availability, low variability among seasons, and high invertebrate diversity.
During recent investigations of the groundwater fauna of Cameroon, specimens of a new species of ... more During recent investigations of the groundwater fauna of Cameroon, specimens of a new species of the stygobitic genus Metastenasellus, M. boutini sp. nov. were collected in wells of the city of Douala. The new species can be easily distinguished from the other species of the genus by its relatively large size (up to 11 mm), pleonite 1 and 2 half the length of pereonite 7, the shape of pleopod 2 in males (presence of an external lobe on the protopodite, distal part of the spermatic duct slightly protruding out of the second article, lack of a distal seta on the exopodite), and uropod half the length of the pleotelson. Ecological data and a key to Metastenasellus species are provided. We also performed an exhaustive analysis of the literature on Stenasellidae in Africa to study the geographical distribution of the family in this continent and discuss some hypotheses about the origin of African species.
During recent investigations of the groundwater fauna of Cameroon, specimens of a new species of ... more During recent investigations of the groundwater fauna of Cameroon, specimens of a new species of the stygobitic genus Metastenasellus, M. boutini sp. nov. were collected in wells of the city of Douala. The new species can be easily distinguished from the other species of the genus by its relatively large size (up to 11 mm), pleonite 1 and 2 half the length of pereonite 7, the shape of pleopod 2 in males (presence of an external lobe on the protopodite, distal part of the spermatic duct slightly protruding out of the second article, lack of a distal seta on the exopodite), and uropod half the length of the pleotelson. Ecological data and a key to Metastenasellus species are provided. We also performed an exhaustive analysis of the literature on Stenasellidae in Africa to study the geographical distribution of the family in this continent and discuss some hypotheses about the origin of African species.
Biodiversity of freswhater organisms of the Selune River: assessment of phyto- and zoo-plankton and benthic macroinvertebrates
HAL (Le Centre pour la Communication Scientifique Directe), Mar 21, 2016
International audienc
Zenodo (CERN European Organization for Nuclear Research), Jan 30, 2023
A research to study the zooplanktonic population in relation to some abiotic variables of the Kri... more A research to study the zooplanktonic population in relation to some abiotic variables of the Kribian coast waters was conducted from July to December 2020 following a monthly sampling in six (6) selected sites. The physicochemical parameters were determining out using standard methods. Concerning the zooplankton, the water was collected at the surface, in the trophogenic and tropholytic layers, then filtered through a 64 µm plankton sieve and the retentate was fixed with 96% alcohol. Identification and counting were done in the laboratory using a Wild M5 binocular loupe, appropriate keys and works. The physicochemical results showed a very good oxygenation of the waters (91.85 ± 3.87%), basic pH (8.43 ± 0.54 U.C), a low salinity and conductivity of respectively 13.04 ± 3.92 g/L and 23.07±4.23 µS/cm characteristic of the haline domains and a temperature of 28.66 ± 1.35°C. With regard to nutrients, the values recorded showed a progressive enrichment of the water in nitrate (2.2±1.81mg/L) and a low concentration in orthophosphate (0.25±0.41mg/L). the zooplankton community haboured, 54 taxa belonging to 3 major groups (Copepoda, Cladocera, Ciliate) and other Zooplankton, 24 families and 29 genera were recorded. The Copepod group dominated the taxonomic richness with 34 taxa (62.96% of total richness), followed by Tintinidae with 4 taxa (7.4%), Cladocera with 1 marine taxa (1.9%) and 15 taxa for other zooplankton (27.8%). Quantitatively, Copepods were once again the most abundant group in the population, with an average of 78.3% of the total zooplankton abundance. The dominant copepod taxa in terms of abundance were those of the families of: Paracalanidae (mean abundance: 116 ind/L) and Oithonidae (mean abundance: 99ind/L).
During recent investigations of the groundwater fauna of Cameroon, specimens of a new species of ... more During recent investigations of the groundwater fauna of Cameroon, specimens of a new species of the stygobitic genus Metastenasellus, M. boutini sp. nov. were collected in wells of the city of Douala. The new species can be easily distinguished from the other species of the genus by its relatively large size (up to 11 mm), pleonite 1 and 2 half the length of pereonite 7, the shape of pleopod 2 in males (presence of an external lobe on the protopodite, distal part of the spermatic duct slightly protruding out of the second article, lack of a distal seta on the exopodite), and uropod half the length of the pleotelson. Ecological data and a key to Metastenasellus species are provided. We also performed an exhaustive analysis of the literature on Stenasellidae in Africa to study the geographical distribution of the family in this continent and discuss some hypotheses about the origin of African species.
UNESCO eBooks, 2023
The Sanaga River is the largest in Cameroon and one of the main resources for the economic develo... more The Sanaga River is the largest in Cameroon and one of the main resources for the economic development of the country. A lack of electricity is one of the primary setbacks for the Cameroonian economy, and the national authorities plan to at least double, from 2,000 MW, the nation's hydropower electricity supply by 2035. Representing more than 75% of the estimated total hydro potential of Cameroon, the Sanaga River has one of the greatest hydropower potentials in Africa. As well as being a vital asset for the national economy, it possesses exceptional natural features such as waterfalls, biodiversity hotspots with endemic and rare wildlife (e.g., the West African manatee, hippopotamus, chimpanzee and forest elephant), and very high cultural diversity, with numerous ethnic groups represented. There are many human activities along the river (use of water resources for food security and irrigated agriculture, inland fisheries, intensive aquaculture, sand extraction and hydropower production) that are increasing, and with visibly detrimental effects. The construction of dams has forced the local population to move from one livelihood activity to another. The unique cultural heritage and biodiversity are hence under pressure, due to over-fishing, logging, hunting, agrochemical pollution and habitat destruction. Unfortunately, the management actions necessary for remediation of these detrimental impacts are not well captured in basin development plans. It is therefore considered urgent to implement more sustainable human activities, including the development of alternative economic resources, such as ecotourism.
Journal of Environmental Management
Mass development of macrophytes is an increasing problem in many aquatic systems worldwide. Dense... more 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.
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Papers by Christophe Piscart