Le peuplement en Hydracariens (Hydrachnellae, Acari) a été étudié dans 108 stations (86 espèces) des Pyrénées centrales. L'analyse canonique et l'analyse factorielle des correspondances permettent de mettre en évidence : - d'une part, une corrélation entre les facteurs écologiques habituellement reconnus (température, vitesse du courant,...) et un certain nombre de paramètres topographiques, hydrologiques, géologiques,..., qui constituent un complexe stationnel, stable dans le temps pour une même station. - d'autre part, une corrélation entre les complexes stationnels et un certain nombre (8) d'associations d'Hydracariens. Cinq paramètres, - altitude de la source, altitude de la station, pente, surface du bassin-versant et régime des eaux, - suffisent à définir un complexe stationnel et à expliquer, avec la nature du substrat (galets ou mousses), la distribution des espèces. Le régime des eaux, notamment, joue un rôle fondamental dans cette distribution et justifie la distinction des auteurs de langue allemande entre faune de Mittel - et Hochgebirge. En fonction du substrat, du taux de reproduction, du cycle biologique, différents types biologiques d'Hydracariens sont mis en évidence. Mais, pour expliquer la structure des communautés, et notamment leur diversité, il faut faire appel à des notions comme la stabilité du biotope (durée), sa surface (espace), la distance entre biotopes équivalents, - c'est-à-dire à la théorie des îles de Mac-Arthur et Wilson. Le peuplement des biotopes instables, de surface limitée et isolés est à la limite aléatoire.

A new classification of Perlodinae (sensu Zwick 1973) is proposed in which three tribes are recognized. Arcynopterygini Ricker & Scudder includes genera whose eggs are circular in cross section while Perlodini Klapálek and Diploperlini, new tribe, include genera whose eggs are triangular or semicircular in cross section.

La diapause des Cyclopides pélagiques d'un lac tempéré peu profond (Créteil, France) a été étudiée sur un cycle annuel. Une dormance estivale affecte les copépodites IV de Cyclops vicinus (avril-mai à février) et de Diacyclops bicuspidatus (mars à novembre) ; une diapause hivernale est observée chez les copépodites IV de Thermocyclops crassus et chez les subadultes de Thermocyclops oithonoides (septembre à avril).Quelques subadultes de Th. oithonoides ont un arrêt de développement sans pénétration dans le sédiment (diapause active).La biomasse moyenne de la fraction diapausante égale 36 % (15 % à 80 %) de la biomasse totale des Cyclopides pendant la période d'étude. Les effectifs benthiques, compris entre 27 000 ind. m-2 et 350 000 ind. m-2, représentent un potentiel de recolonisation du domaine pélagique de 6 ind. l-1 à 78 ind. l-1.Alors que la diapause hivernale de Th. oithonoides et de Th. crassus est probablement une adaptation à des conditions climatiques défavorables, la diapause estivale de C. vicinus serait une stratégie adaptative d'évitement de la prédation.

Freshwater systems on volcanic oceanic islands have very particular characteristics as a result of their geological origins, relatively small size, distances from source areas for colonizers, and distinct catchment morphology. These factors result in freshwater communities that are clearly distinct from continental systems. Chironomid spatial and temporal distribution was investigated in chironomid assemblages at 21 sites across the Azores Archipelago. Results using PERMANOVA, a permutational multivariate analysis of variance, indicated significant longitudinal differences in assemblages but none between islands or over time.

Links between hydromorphological and physicochemical variables and the community assemblage were assessed using DISTLM, a linear model for distance-based multivariate analysis. The percentage of variation explained by hydromorphological factors (31%) was slightly higher than that explained by physicochemical (28%) factors. Descriptors of land use (forest area, scrub area, natural area of catchment) and stream slope were found to be the best environmental predictors of chironomid assemblages in Azores. Physicochemical variables such as temperature, pH, nitrite, iron and conductivity were the principal drivers of change in chironomid composition in stream locations. Headwater sites, characterized by lower temperature, acid to neutral pH values, low conductivity, nutrient and metal concentrations were dominated by Rheocricotopus atripes. Mid-section sites, located in agricultural areas were dominated by Thienemanniella clavicornis. Urbanized lower reaches were characterized by higher temperature, pH, conductivity and nutrient levels and were dominated by Cricotopus sp. These results give essential information that allows us to predict the response of different chironomid species to hydromorphological and physicochemical gradients across the archipelago's streams contributing providing the basis for the development of tools for the implementation of the Water Frame Directive.

We studied the influence of lotic and lentic stretches on zooseston flux in the karstic barrage Plitvice Lakes (Croatia). Threesampling stretches were selected: 1) a channel with low inclination; 2) water flow through a deep lake (retention), and 3) a channelwith cascades and sharp inclination. At all sampling points of the three stretches, zooseston reached maximum abundance inSeptember (up to 147.39 ind/m3). Rotifers dominated in both zooseston abundance (58 to 80%) and diversity (66 taxa), followedby crustaceans (23 taxa), predominantly Cladocera and Copepoda. Kruskal-Wallis test suggest statistically significant differencesbetween the lentic and both lotic stretches in the biomass net flux of euplanktonic organisms. The net flux of benthicorganism biomass and changes in the biodiversity index were significantly different between the lentic stretch and lotic stretchwith high inclination. Lotic stretches had a greater influence on the increase of abundance and biomass of benthic and semiplanktonicorganisms than on the decrease of euplanktonic organisms. Principal Components Analysis of the species environmentrelationship explained 66% of the variance by the two first axes, where axis 1 accounted for 39% and axis 2 accounted for27% of the variance. Oligochaets, insect larvae, nematodes and total zooseston were associated with component 1, showing thattheir biomass was negatively correlated with discharge and dissolved oxygen concentration and positively correlated with temperature.Other taxa showed a similar correlation with component 1. Biomass of Cladocera, Copepoda, T. birostris, Polyarthraspp., K. cochlearis and rotifers was associated with component 2, and positively correlated with food resources such as chl-a,POM and DOM. The inference is that zooseston flux through Plitvice Lakes is a function of the hydrological and physiographicalfeatures of the stretches, as well as food resources from the lakes.

Two-day life cycle tests with the rotifer Brachionus calyciflorus were run to study the nutritional quality effects to rotifers ofScenedesmus pectinatus grown under non-limiting, nitrogen limiting and phosphorus limiting conditions and the feedback of therotifers on the food algae. Under nutrient-limited conditions of its algal food Brachionus production was depressed, animals producedfewer eggs and were smaller sized. Clearance rates of Brachionus offered non-nutrient-limited and nutrient-limited foodwere similar. The number of cells per colony was similar for S. pectinatus under nitrogen limited and phosphorus limited conditionsboth in the absence and presence of Brachionus. Cell volumes of phosphorus limited S. pectinatus were larger than thoseof nitrogen limited cells. The most dramatic response of the food alga S. pectinatus was observed in non-nutrient-limited conditions:a strong size enlargement occurred only in the presence of Brachionus. This was caused by a higher share of eight-celledcolonies and larger individual cell volumes in the presence of rotifers than in their absence. S. pectinatus might gain an advantageof becoming larger in moving out of the feeding window of its enemy, but nutrient limited conditions might undermine theeffectiveness of such reaction.

Many Oligochaeta were collected during recent investigations in Southern-European caves. This is the first contribution in which some data concerning the Tubificidae are summarized. Three new species of Rhyacodrilinae, including a new genus, are described: Rhyacodrilus omodeoi n. sp., Rhyacodrilus dolcei n. sp., Rhyacodrilus gasparoi n. sp. and Stochidrilus glandulosus n. gen., n. sp. The poorly known species Frearidrilus pescei (Dumnicka 1981, augm. 1987) is redescribed on the basis of new material collected in Slovenian caves; this revision allowed the proposal to ascribe it to the genus Tubifex, considering the monospecific genus Frearidrilus as a junior synonym of Tubifex.

The temporal dynamics in density, life histories, and emergence patterns were described for the first time for five Plecopteraspecies in tributaries of the Futaleufú River in Patagonia, Argentina. Benthic samples and adult collections were made in five loworder Nothofagus forested streams. Four species of Gripopterygidae; Aubertoperla illiesi, Notoperlopsis femina, Antarctoperlamichaelseni and Senzilloides panguipulli had simple, highly synchronized univoltine life histories. The austroperlid Klapopteryxkuscheli takes more than two years to develop. Emergence periods of most of the species were concentrated in late spring andsummer (October to February), which suggests seasonal and synchronized life histories. Most N. femina adults were collected inmid spring indicating this species emerged first, whereas S. panguipulli emerged last from January to April. Aubertoperla illiesishowed a slightly delayed emergence at the high elevation site (La Hoya Stream) when compared to a piedmont stream,suggesting that temperature was an important control. Although we were unable to describe the life history of Limnoperla jaffueli(Gripopterygidae) its adult emergence period was November to January. Life histories of Plecoptera species in the studiedstreams seem to have a high degree of seasonality at least at this latitude, and are possibly determined by predictable temperaturepatterns and discharge regimes. This first contribution on the life histories of Plecoptera species helps us to better understand thedynamics and functioning of pristine but fragile aquatic environments in Patagonia.

— Le cycle de développement de 14 espèces d'invertébrés benthiques est étudié dans trois petits ruisseaux de moyenne altitude (732 m) dans les Pyrenees centrales.

— La température reste relativement constante au cours de l'année (minimum 8,5° C en février; maximum 13° C en août et septembre).

— Différentes classes de tailles ou stades larvaires sont déterminés par observation des fourreaux alaires (Ephéméroptères) ou par mesure de la largeur des capsules céphaliques (Plécoptères, Trichoptères, Coléoptères).

— Les espèces étudiées présentent des périodes d'émergence et d'éclosion en général plus longues ou plus précoces que celles relevées par les divers auteurs; les conditions thermiques entrainent une croissance régulière de la faune.

— Les cycles, classés d'après la durée des périodes d'éclosion et de vie imaginale sont rapprochés de la classification de HYXKS (1901-1970).

Un nouveau type de développement S, correspond à une espèce à croissance lente et période de vol automnale. La juxtaposition de plusieurs indices semble nécessaire pour caractériser le développement larvaire de certaines espèces dont les éclosions sont largement étalées dans le temps.

A straightforward experimental approach was carried out to study the adaptation responses of a typical floating-leaved aquatic plant Nymphoides peltata to changes in water availability. N. peltata grown in terrestrial habitat was approximately 88.77% lower in total biomass, 62.75% higher in root biomass allocation, 80.9% higher in root-shoot ratio, and 54.5% longer in leaf longevity compared with N. peltata grown in aquatic habitats. Anatomical analyses suggest that aquatic-grown N. peltata exhibits a well-developed lacunal system in leaf, petiole, and coarse root. Moreover, aquatic-grown N. peltata had approximately a higher in lacunal system in leaf, petiole, and coarse root by 28.57%, 56.41% and 82.35%, respectively, than those of terrestrial-grown N. peltata. These results indicated that N. peltata was well adapted to the terrestrial habitat because of its biomass allocation, morphological, and anatomical strategies that depended on the increase in root biomass allocation and leaf longevity, as well as the decrease in the lacunal system volume in leaf, petiole, and coarse root. This indicates that N. peltata can develop multiple morphological and anatomical strategies, an integrated approach to enhance survival in dynamic and unpredictable environments.

La consommation d'oxygène de 8 souches de Rotifères planctoniques a été mesurée à la même température (20°) à l'aide de la microméthode de Winkler. Les auteurs ont essayé d'utiliser la teneur en protéines comme base pour la comparaison de la respiration de Rotifères planctoniques de tailles différentes. Le rapport du logarithme du taux de respiration au logarithme de la teneur en protéine indique une corrélation linéaire de pente b = 0,72 en eau de source volcanique et b ~ 1 en eau d'étang calcaire. La plupart des Rotifères étudiés montrent un métabolisme respiratoire plus élevé en eau d'étang.

Ni la durée des expériences (dans la limite de 6 heures) et par conséquent la tension du milieu en oxygène (au-dessus de 50 % de la saturation), ni la densité en individus, ni la lumière, ni le type de régime alimentaire ne paraissent influencer le taux de consommation d'oxygène des Rotifères.

Phytoplankton dynamics and morphological plasticity were studied in an oligo-mesotrophic lake from late spring to earlyautumn in 2004 on a weekly to bi-weekly basis. This study aimed to evaluate the effect of environmental constraints on morphologicalplasticity and size structure of dominant species through the stratified period of the lake. While centric diatoms developedmainly in the epilimnion, Fragilaria crotonensis, Synedra sp. and Synedra acus were very well distributed through thewhole water column, as was the cryptophyte Plagioselmis nannoplanctica. A filamentous cyanobacterium, Planktothrix rubescens,was stratified in the metalimnion throughout the sampling period, while Mougeotia sp. was entrained through the wholewater column during the early autumn. Surface area / volume (S/V) ratios were calculated for the dominant species on each samplingdate. The minimum S/V ratio was found with centric diatoms, while maximal values measured were for Synedra sp. andAsterionella formosa. The S/V ratio of the only dominant cryptophyte, Plagioselmis nannoplanctica was also high; variationswere negatively correlated with NO3-N and PO4-P (-0.62 and -0.61, respectively) and positively correlated with euphotic depth(r=0.57) and temperature (r=0.82). On the other hand, the S/V ratios of Fragilaria crotonensis and Cyclotella ocellata each showedstrong negative correlation with silica concentrations (-0.55 and -0.62, respectively). It is concluded that allometric relationshipsshowed significant differences among species according to depth and season.

Investigating forces driving the structure of aquatic communities has long been an important issue in ecology. In the present study, we focused on the effects of changed water supply for aquaculture ponds on phytoplankton, zooplankton and macrozoobenthos communities during two seasons of rearing common carp. We compared these communities between two types of inflow water: surface sources of water – a reservoir pond, two open wells and a small stream and groundwater – deep tube well. Significant changes were observed in environmental variables after the introduction of the groundwater source: oxygen concentration and water hardness decreased, while conductivity, phosphorus and un-ionized ammonia increased. Results revealed that all investigated groups, except Mollusca (macrozoobenthos), decreased in species richness, abundance and biomass due to changed water chemistry, but differed in the level of susceptibility. Rotifera and Cladocera were the most affected showing a sharp decline in density and number of species since 66% of species disappeared from the ponds. The abundance of Copepoda was relatively high although significantly lower under new conditions, with adults being more tolerant to changed inflow water than nauplii larvae. Phytoplankton had the highest potential to replace previous species with newcomers more adapted to changed water chemistry, providing 36 immigrant species, whereas 49 became extinct. Although mainly influenced by fish predation, Chironomidae (macrozoobenthos) were undoubtedly affected by changed water chemistry. These results suggest profound changes in three key ecological groups produced by significant changes of important environmental variables and water quality after the shift from surface to groundwater supply.

1) Près de 190 espèces d'algues ont été identifiées dans le phytoplancton de la rivière Lot ; les Diatomées et les Chlorophycées dominent.

2) Les plus fortes biomasses (5 à 15 g de poids frais par m3) apparaissent dans les grands réservoirs de l'amont et dans la zone canalisée de la partie inférieure de la rivière lors de l'étiage estival. Aux très faibles débits sont associées des proliférations de Chlorophycées et une stratification verticale.

3) L'analyse des profils de photosynthèse, mesurée à l'aide de 14C, montre que la production photosynthétique par unité de surface (Σ A) est fonction de la capacité photosynthétique du phytoplancton (Pmax), de l'extinction de la lumière (α) et du logarithme du quotient énergie lumineuse incidente/intensité du début de saturation de la photosynthèse par la lumière (I'o/Ik). Pmax semble être déterminé par l'abondance des Chlorophycées nanoplanctoniques, elle-même liée à l'augmentation des températures et à la diminution du débit. Les variations de α suivent celles de l'abondance des matières en suspension où les algues n'interviennent que pour une faible proportion.

4) La production primaire du Lot moyen et inférieur a été estimée à 275 g C/m2/an dont près de 80 % correspond aux trois mois d'été.

5) L'étude d'une masse d'eau au cours de son déplacement montre qu'une grande part (80 %) du carbone assimilé est perdue par respiration. Cette respiration représente moins de la moitié de l'oxygène consommé. La production extracellulaire est importante en été.

Une étude de 32 prélèvements de macrobenthos est effectuée au Surber dans 13 stations du Furans et de ses affluents, cours d'eau du Bas-Bugey.

Des analyses factorielles des correspondances permettent de hiérarchiser les différences entre prélèvements, et d'établir une typologie d'après le macrobenthos. L'abondance de chacun des 99 taxons récoltés est donnée en nombre d'individus/0,1 m2, puis en classe d'abondance en progression géométrique (de 1 à 12). Cette évaluation semi-quantitative contient encore toute l'information nécessaire.

Les ressemblances entre prélèvements d'une même station sont en général plus grandes, malgré les différences de faciès, que celles entre prélèvements de stations différentes.

L'examen de ces ressemblances permet de diviser le système en 3 secteurs : l'affluent Arène, caractérisé par sa charge organique, le cours supérieur du Furans et le cours moyen et inférieur issu d'une grosse exurgence. Les effets modérés dus aux pollutions organiques apparaissent au second plan par rapport aux perturbations physionomiques (cascade, résurgence, influence du Rhône).

Chaque groupe faunistique considéré seul donne une image de la structure d'ensemble. Les Trichoptères (20 taxons) et les Coléoptères (17 espèces) suffisent chacun à rendre compte de cette structure. Les Ephéméroptères et Plécoptères pris ensemble (19 taxons) soulignent plutôt les effets eutrophisants, de même que les Oligochètes. Diptères et groupes divers sont imprécis, surtout à cause de l'insuffisance de leur identification.

La prospection de 33 rizières, considérées comme des milieux aquatiques temporaires estivaux et réparties sur l'ensemble de la Camargue, a permis de récolter 41 espèces de Copépodes, Cladocères et Ostracodes.

L'étude de la sucession des espèces dominantes et l'utilisation de deux indices de diversité biologique et de variété montrent une évolution saisonnière du peuplement caractérisée par deux phases :

- une phase juvénile au printemps où la diversité biologique est relativement faible. Moina brachiata et Metacyclops minutus sont abondants.

- une phase de maturité en été où le nombre d'espèces augmente. Cryptocyclops bicolor apparaît en fin de saison. Les relations trophiques se compliquent.

L'impact des interventions humaines (traitements phytosanitaires, etc...) sur le peuplement est discuté.

The aim of this study was to examine morphometric differentiation of gudgeon (Romanogobio and Gobio) species inhabiting the Carpathian Basin, Hungary, with special regard to two recently described species classified into the Gobio genus. For statistical analyses, 23 morphometric and 8 meristic characters were measured on each of the 733 preserved specimens originating from museum collections. The analyses of the standardized morphometric traits revealed low intraspecific variability in all studied species, but varying degrees of interspecific differences. The strongest morphometric differentiation was found in Romanogobio uranoscopus (Agassiz, 1828), which can be characterized by the most special environmental needs. The two allopatric Gobio species showed the weakest morphometric difference. The meristic characters showed high variability in the Romanogobio spp., but did not show significant differences in the two Gobio species. The results show that the morphometric and meristic similarity of the studied Gobio species is definitely high, which preclude reliable identification based on phenotypic characters if only some specimens are available. It seems that the most usable discriminating feature for these species is the localization of the collection site.

A partir d'une population de 500 alevins vésicules de Truite commune Salmo trutta L., introduits dans un ruisseau artificiel, les alevins "dévalants" sont isolés par un système de piégeages successifs et marqués par ablation de nageoire. Puis ils sont introduits dans d'autres ruisseaux artificiels vides d'occupants et leur comportement est observé.

Comme dans la nature, les alevins dévalent la nuit. Certains alevins dévalent plus longtemps que d'autres. Cependant, tous les alevins "dévalants" survivants finissent par adopter un comportement de nage statique diurne et s'organisent en une mosaïque de territoires. Mais ils le font plus tardivement que les sédentaires demeurés dans le premier ruisseau expérimental. Les alevins "dévalants" sont plus petits que les sédentaires à la fin de l'expérience. Leurs comportements de nage et territorial tardifs ainsi que leur moindre croissance renforcent l'hypothèse selon laquelle les alevins "dévalants" présentent un retard de développement par rapport aux alevins sédentaires.

The stability of occurrence, abundance and dominance of fish was compared between two sampling periods, 1963-66 and 2002-04 in two lowland rivers from the Warta/Odra system (Poland): the Widawka and its tributary Grabia (95.8 and 77.3 km long, respectively). The Widawka system has been under strong influence of a brown coal strip mine since the 1970s. Long stretches of the upper Widawka and of its certain tributaries were changed into concrete canals, which receive daily 660 000 m3 of water disposed by the strip mine. The Grabia maintained its natural character. On the basis of the abundance of fish species, the Kohonen artificial neural network almost perfectly separated fish samples collected in 1963-66 from samples collected in 2002-04, which means that: 1) the differences in ichthyofauna between these two sampling periods were more drastic than spatial differences between the severely modified Widawka and the natural Grabia, and 2) in general, ichthyofauna at the most modified sites in 1963-66 was in better condition than at the least modified sites in 2002-04. In 1963-66, the species, roach, gudgeon, bleak and dace composed together 70% of the total fish number, while in 2002-04 the same joint dominance was gained by roach, perch and stone loach. The analysis of temporal changes in the Widawka and Grabia Rivers focused on the following 3 fish groups: (1) Non-psammophilous rheophils (NPR), which are most vulnerable to human-induced modifications, which is why their decline and/or extinction are typical for unbalanced lotic ecosystems. In this study, the total dominance of NPR decreased 5 times; (2) Psammophilous rheophils (stone loach and gudgeon), which often predominate in degraded smaller streams. In this study, the dominance of stone loach increased 3 times and was highest in the most affected stretches of the Widawka River, including those that had been canalised. Gudgeon was often dominant at moderately modified sites of the Widawka; (3) Roach and perch, whose high dominance is typical for disturbed larger rivers, which was supported also in this study by the fact that both species were most dominant in 2002-04. The dominance of roach increased almost twice and was highest in the lower courses of both rivers. A significant increase in abundance was recorded for perch, whose dominance was highest in the canalised section of the Widawka. The described changes were deep enough to influence the hardly sensitive CDI, Simpson and Shannon indices, which indicated a significant increase in dominance and a decrease in diversity of fish assemblages over the last 4 decades.

Aerobic anoxygenic phototrophic (AAP) bacteria are widely distributed in marine and freshwater ecosystems. The aims of this study were to investigate the diversity and abundance of AAP bacteria in cyanobacterial bloom-forming eutrophic lakes and to study the association of AAP bacteria with the bloom-forming cyanobacteria. Analysis of pufM gene (the light-reaction center gene) clone libraries indicated that in eutrophic lakes (Lake Taihu and Lake Chaohu, China) with cyanobacterium Microcystis blooms, the AAP bacteria were related to members of Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. In Lake Taihu and Lake Chaohu, Alphaproteobacteria accounted for 81.5% and 75.0% of Microcystis-associated AAP bacteria, respectively, and 84.6% and 72.5% of free-living AAP bacteria, respectively. The predominance of Alphaproteobacteria in the two lakes was different from the previously reported predominance of Betaproteobacteria in freshwater lakes. Quantitative real-time PCR analysis indicated that in Lake Taihu and Lake Chaohu, AAP bacteria represented an important part of the bacterial community associated with Microcystis, and the abundance of Microcystis-associated AAP bacteria (18.3% and 11.7%, respectively) was higher than that of free-living AAP bacteria (5.1% and 7.9%, respectively). The abundance of AAP bacteria in the two bloom-forming lakes was higher than the previously reported level in other eutrophic freshwater bodies.