Phytoplankton dynamics in freshwater ecosystems can be faced as a meaningful natural stressor for its main grazers, and hence constrain bottom-up interactions within the trophic structure of the food-web. Filter-feeding zooplankters, such as Daphnia, cope with resources fluctuations by adjusting their life-history as a function of balances in the energy allocation rules. Additionally, Daphnia populations often withstand interspecific competition within coexisting related species, and it is generally assumed that body size is a strategic trait conditioning exploitative ability and the related competitive advantage of species. The lifehistory responses of one Daphnia magna population and three populations of Daphnia cf longispina to a discrete gradient of algae concentration were assessed. This experiment was focused on (i) how these distinct populations regulate life-history when feeding over low, intermediate and high food-levels; and on (ii) whether the large-bodied D. magna can be better in exploiting resources over the gradient than can the smaller D. cf longispina populations. We found evidences that body size might not be the single trait influencing the exploitative ability of related species. The D. cf longispina populations were often better than D. magna in exploiting different levels of resources, and remarkable differences in fitness were found between these similar-sized individuals within food-level; indeed, these differences were frequently of higher scale than those found between the larger D. magna and any of the D. cf longispina populations.

The Asian clam Corbicula fluminea is one of the most invasive species in freshwater aquatic ecosystems. The rapid growth, earlier sexual maturity, short life span, high fecundity and its association with human activities makes C. fluminea a non-indigenous invasive species likely to colonize new environments. This species, originally distributed in Asiatic ecosystems, is now a common inhabitant of American and European freshwater habitats. The present paper reviews the information related to the life cycle, ecology and potential ecological and economic impacts caused by C. fluminea in the invaded habitats. Furthermore, this paper also proposed future works that may be implemented in order to increase our general knowledge about the ecology of this bivalve.

The distribution and overall fish abundance, and biomass of fish populations in the open water of meso-eutrophic Lake Balaton were studied in 2003-2007 using hydroacoustics and gill nets. Gillnet catches revealed that bleak (53-76 %) common bream (8-42 %), white bream and razor fish (2-18 %) dominated in the open water of the lake. Comparisons of target strength distribution from hydroacoustics and length distribution from the gillnets showed that the fishing gear did not quantitatively catch the smallest and largest size groups of fish. Mean acoustic fish abundance and biomass fluctuated significantly between both basins and years. The biomass of fish populations reflects the trophic gradient along the longitudinal axis of the lake (min-max.: 89-181 kg ha-1) showing a decreasing trend with years. The mean acoustic fish biomass was significantly higher in the eutrophic western basin, compared with mesotrophic eastern and middle ones.

Particulate organic matter (POM), dissolved organic matter (DOM), bacteria and cladoceran were sampled seasonally at Zhihugang Estuary and Lake Center in Taihu Lake. The δ13C of the four organic matter fractions showed consistent temporal variation, with heaviest values in summer and lower at other times of the year. The cladoceran δ13C showed a significant correlation with that of POM, reflecting a heavy dietary dependence on POM during the study period. The bacteria became enriched in 13C compared with that of DOM throughout the sampling dates, although no significant relationship was found between the two fractions. δ13C values of POM, cladoceran and bacteria were all negative significantly correlated with oxidation and reduction potential (ORP), and specific conductivity (SpCond). As for δ15N, the seasonal pattern of food web components was variable. The POM δ15N signature exhibited the most enriched isotope ratios during the summer months when dissolved inorganic nitrogen (DIN) nutrients were at their lowest concentrations. The consumption of DIN in summer can explain in part the progressive accumulation of heavy nitrogen isotopes during this period. Spatially, δ13C and δ15N of the food web components were all slightly depleted at Estuary than that at Lake Center during the study period, possibly due to large allochthonous inputs at Zhihugang Estuary. Relatively wide ranges of stable isotopic values from both sites suggest that seasonality should be considered when attempting to establish food web structures in a eutrophic lake.

A model (DALIS 1.0) of pelagic zone trophic interactions was developed using long-term, comprehensive data sets of the Sulejow Reservoir. We calibrated the model using observations from the pelagic zone of the Sulejow Reservoir made between 1999 and 2001. The model performed well in the description of Daphnia sp. – L. kindtii interactions when hydrological conditions were stable. A discrepancy between observed and simulated results was found when water inflows were high, which washed out the biota. We suggested that the hydrological impacts should be coupled in the updated DALIS model. Using DALIS, we also tested two scenarios: the food web model (A) without Leptodora; and (B) without YOY fish, under both good and bad food conditions for Daphnia. Results indicated that Leptodora would have a more significant impact on the reduction of Daphnia biomass than juvenile fish during some periods. As the maintenance of high Daphnia densities is recognised as a key factor in top-down effects, the DALIS model may provide frameworks that support ongoing empirical work. It is therefore recommended that the model be incorporated into the programme of the Sulejow Reservoir restoration.

Life history patterns of the three most abundant chironomids were analysed in Lake Balaton by monitoring the population dynamics of larvae and the presence of pupal exuviae. Procladius choreus had two generations per year with at least two parallel cohorts during 1996-1999. Tanypus punctipennis had a trivoltine life cycle with occasional parallel cohorts, overlapping generations and long, interrupted emergence periods between 1997 and 1999. At Tihany, Chironomus balatonicus had only one detectable generation between 1995 and 2002. Meanwhile at Keszthely, the abundance of C. balatonicus larvae peaked from autumn to the beginning of summer in 1996/1997, 1998/1999 and 2000/2001, and it was continuously high from August 2001 to October 2002. However, between these abundance peaks there were long periods when larvae could not be found at all. The extreme population dynamics of C. balatonicus suggests that living conditions may fluctuate around the limit of this species in Lake Balaton. Although C. balatonicus larvae practically were not found at both sampling sites from July 1997 to August 1998, and from July 1999 to August 2000, sporadic occurrence of exuviae during these periods proves that refuge areas should exist within the lake. Possible background of the uncommon population dynamics of C. balatonicus is discussed.

White-clawed crayfish, bullhead, and freshwater pearl mussel are different model organisms in terms of biological traits. Analysing their distribution patterns, habitat demands, and causes of decline may thus help to derive broader frameworks for conservation projects. This paper includes a wide-ranging literature review for these three threatened freshwater animals, then uses general patterns to make suggestions about broader protection measures for freshwater species. Each species has a patchy distribution, from local to broad spatial scales. However, we point out the difficulty to summarise such knowledge, because many variables were not consistently and/or accurately recorded by workers, and because the range of colonised habitats depends on the environmental heterogeneity within study areas. Causes of decline are chiefly related to human activities which modify the biological, chemical, and physical features of the aquatic environment, and can be classified into four types: physical habitat alterations, interspecific interactions, overfishing and poaching, and natural disturbance. By analysing causes of decline and possible actions, we develop seven general trends that could be adopted for a wider array of species. However, protection plans cannot be effective without actual collaborations between river managers, local inhabitants, and authorities. Finally, the re-introduction procedure itself (if needed) depends on the biology of the species under survey, and remains specific. At the same time, further fundamental research is needed to generalise relationships between population and habitat dynamics at different spatial and temporal scales.

The population dynamics and life cycle of two mollusc species Pisidium amnicum and Valvata piscinalis of the Saône river were studied for nine years. The newborn of the former species appeared in April each year. The latter species produced two cohorts per year until 2003. Spawning in spring led to the birth of the early cohort, which generally appeared in May, while spawning in the summer led to the birth of the late cohort, which appeared from July to November. The increase of the mean annual temperature by 1.9°C from 1998 to 2000 was followed by an increase in the density of mollusc populations, possibly triggering or amplifying inter and intra specific competition for food. However, the 2003 heatwave was responsible for the sudden decline of the P. amnicum population, then the more progressive decline of that of V. piscinalis after having strongly modified its demographic structure and its life cycle. In 2004 and 2005 V. piscinalis only produced one cohort per year. The observations carried out strongly suggest that the insufficiency of available resources was one of the possible causes of their failure to recover in 2004 and 2005. The increase of global warming predicted by different models could result in the gradual disappearance of P. amnicum from the potamon and of V. piscinalis from the freshwater systems most directly exposed to climatic warming, such as the Saône River.

Toxic cyanobacteria are common in Portuguese freshwaters and are a cause of concern, given that exposure to subacute levels of cyanobacterial toxins through drinking and recreational water might have deleterious effects on human health. Since 1996 several laboratories have been involved in the screening of cyanotoxins in different freshwater bodies, some on a regularly basis but most on a sporadically basis. Here we present data on the phytoplankton communities and on microcystins production occurring in six freshwater reservoirs located in a dry region of south Portugal, from May to December 2005 and April to July 2006. Most of the reservoirs experienced cyanobacterial blooms of various intensities, following noticeable shifts in phytoplankton composition towards cyanobacterial dominance. The seasonal dominance of cyanobacteria during warmer periods was not a fi xed pattern since considerable amounts of cyanobacteria were also recorded during winter months in some reservoirs. Microcystins were detected in 23% of the 53 samples tested and some of them had concentrations higher than the WHO guideline of 1μg L-1 of microcystins, but their amounts not always reflected the encountered cyanobacteria biomass. Although Microcystis aeruginosa seems to be the major species responsible for microcystins production, other potentially toxigenic bloom-forming species were also found. These results reflect the irregular and unpredictable nature of cyanobacterial blooms in what respects to their occurrence, their composition, their intensity and persistency, as well as to their overall toxicity, strengthening the need of a systematic survey of freshwater resources for the correct risk assessment of cyanobacteria and associated toxins in natural environments.

Mediterranean Temporary Ponds (MTPs) are priority habitats (Natura 2000) of great importance according to the European Legislation (Habitats Directive 92/43/EEC). They are being destroyed mostly because of public ignorance of their significant value. Today, MTPs are subject to high pressures from several human activities (agriculture, livestock, tourism etc.). In this work, the “Drivers-Pressures-State-Impacts-Responses” (DPSIR) model has been used, because it allows to evaluate the impact of the human socioeconomic pressure. We estimated the present condition of West Crete’s MTPs, in order to propose management practices for their restoration. A comparison with the Greek and European MTPs is also developed.

The Guadiana estuary (Iberian Peninsula, Europe) has low agriculture, industry and urban pressure, unlike other major Iberian estuaries; however, this situation is about to change. The Alqueva dam was constructed at 150 km from the river mouth, creating one of the biggest artificial lakes in Europe, which will support 110 000 ha of irrigation areas. Moreover, the estuarine margins are suffering increased human pressure. The risks that the Alqueva dam will pose to the downstream ecosystems, mainly to the estuary and adjacent coastal area, will be reviewed in this paper. Other issues are also analysed, as increased human desertification in the Portuguese basin, real estate pressure and the impact of the construction of a public infrastructure in the Portuguese lower estuary. Increased problems of sediment load reduction, water quality deterioration and shifts in the downstream fish populations are expected due to higher river flow reduction. Irreversible changes to estuarine margins and increased risk of pollution in the estuary will result from the multiple urban pressures. Lack of forest management and increased risk of wildfires, leading to water quality degradation and increased soil erosion, are a result of human desertification in the upper Portuguese basin. Multiple solutions to tackle these problems have to be considered. Creating the International Natural Park of the Lower Guadiana would not be enough and tourism should not be regarded as the only way to develop such a poor region. An ecohydrological approach of the basin should be implemented, to establish scientific based solutions to help solving conflicts and testing scenarios. Ultimately, the creation of a Portuguese-Spanish Basin Management Council for the lower Guadiana, involving those that are interested in the sustainable development of the Guadiana (local populations and associations, private stakeholders (dam managers, tourism entrepreneurs, farmers), local and national authorities, ENGO’s and scientists) is essential to produce ecological and sustainable management decisions.

The aim of this paper is to report the colonization process of three headwater rivers of two large trans-national Pacific river basins shared by Chile and Argentina, by exotic Chinook salmon (Oncorhynchus tshawytscha). To characterize the populations at the sites, fish were analyzed in terms of length, weight, age, and stream residency patterns. Fishermen familiar with the area were interviewed to establish the seasonal occurrence of fish and to reconstruct the history of the colonization process. Records of salmon production in Chile by regions were examined to evaluate the potential origin of fish in coastal net pen aquaculture. The regularity of spawning runs in our study sites indicates that Chinook salmon have established spawning populations in these rivers. While spawning was verified in all three rivers, only one seems to serve as a holding area for pre-spawning salmon early in spring. The correlation in the historical occurrence of Chinook salmon in the three rivers suggests that they have been colonized as part of the same introduction event. Moreover, the temporal correlation with the development of ocean net pen production for this species in the Chiloé region suggests that the fish may originate from escapes from these enterprises. As in all previous reports of exotic Chinook salmon in Patagonia and New Zealand, populations in the three rivers have a combination of stream and ocean ecotypes. We discuss the importance of plasticity in critical life history characteristics for the success of Chinook salmon in Patagonia, compared to other species of anadromous salmonids.

At present, 99 species of cladocerans are known from Thailand, but up to ten more have not been identified to species, particularly in Chydorus, Ephemeroporus and Pleuroxus. Cosmopolitan species are a minority, while wide-ranging circumtropical taxa are an important element, beside species that only occur in the tropics-subtropics of two continents. At least three species are suspected of a neotropical - southeast Asian disjunction, while three more are provisionally considered endemic of Thailand. Daphnia, as usual in the tropics, is rare and reduced to the single D. lumholtzi.

Benthic macroinvertebrates collected at seven different streams displaying different pollution levels were used to investigate species abundance patterns in polluted streams. Community response to disturbances in streams was analysed using species abundance distribution (SAD) for benthic macroinvertebrates across different levels of pollution. The slopes of rank abundance were characteristically steeper with decreasing species richness at the polluted sample sites, while the slopes were less steep with higher species richness at the clean or slightly disturbed sample sites. The SADs were broadly fitted to the log normal distribution in benthic macroinvertebrate communities across different levels of pollution. A geometric series was partly accepted for the communities at the severely polluted sites where new species could not be readily introduced. A power law was applied to the SADs, and the parameters reflected the states pertaining to the sample sites. The SADs were also efficient in revealing ecological state of communities where physico-chemical indicators could not be easily differentiated for stressful conditions in streams.

We reported diel fluctuation in isotopic composition of surface seston from two connected lakes in China, oligotrophic Lake Fuxian and eutrophic Lake Xingyun. The decrease in nighttime and the increase in daytime of isotope signatures of seston might be attributed to the light-dependent balance between the photosynthesis and the respiration of phytoplankton and to the changes in the species composition and the relative abundance of phytoplankton functional groups at the water’s surface in diel growth. The relatively high isotopic signatures and the large-extent diel fluctuation of phytoplankton in the eutrophic lake could be due to utilization of heavy-isotope-enriched inorganic sources and the high primary productivity. Extent of diel fluctuation in δ13C and δ15N of phytoplankton were relatively small compared with the isotopic enrichment per trophic transfer and thus might have negligible effect on the source identifi cation and the trophic evaluation of consumers.

Without human intervention, ponds progressively fill up with aquatic vegetation, so that the structure and age of the vegetal formations show great contrasts within a given set of water bodies. We hypothesized that the biological traits of pond invertebrate communities differed significantly among ponds having different vegetal formations. To test this hypothesis, we selected three neighbouring ponds showing a gradient of vegetation cover and type (sparse bryophytes on rocky substrata (pond 1), extensive submerged Chara beds (pond 2), aerial Typha stands (pond 3)), and we studied between-ponds variations in the combinations of species traits. Taxa biomass was monthly recorded in each pond over one year, to take into account species’ seasonality. Species traits were described using a fuzzy-coding method and a simultaneous analysis of the two matrices (co-inertia analysis) was used to investigate changes in biological trait composition. Biomass increased from pond 1 to pond 3, and was higher in vegetal than in muddy mesohabitats. Among 25 biological traits, 10 were significantly correlated to the distribution of samples: number of generations per year, cohort production interval, adult longevity, adult size, number of eggs per female, dispersal ability, dispersal mode, consumer level, ingested food type, and feeding group. Invertebrates in pond 1 species allocated much energy to reproduction, while in pond 3 resource use was favoured by larger body size, long-lived organisms, and a higher diversity of feeding groups. Our results suggest that the structure and age of the vegetal formation play role in selecting species traits related to population dynamics and feeding habits.

The temporal dynamics in density, life histories, and emergence patterns were described for the first time for five Plecoptera species in tributaries of the Futaleufú River in Patagonia, Argentina. Benthic samples and adult collections were made in five low order Nothofagus forested streams. Four species of Gripopterygidae; Aubertoperla illiesi, Notoperlopsis femina, Antarctoperla michaelseni and Senzilloides panguipulli had simple, highly synchronized univoltine life histories. The austroperlid Klapopteryx kuscheli takes more than two years to develop. Emergence periods of most of the species were concentrated in late spring and summer (October to February), which suggests seasonal and synchronized life histories. Most N. femina adults were collected in mid spring indicating this species emerged first, whereas S. panguipulli emerged last from January to April. Aubertoperla illiesi showed 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 studied streams seem to have a high degree of seasonality at least at this latitude, and are possibly determined by predictable temperature patterns and discharge regimes. This first contribution on the life histories of Plecoptera species helps us to better understand the dynamics and functioning of pristine but fragile aquatic environments in Patagonia.

Based on a literature survey and the identifi cation of all available collection material from Flanders, a checklist is presented, distribution maps are plotted and the relationship between the occurrence of the different species and water characteristics is analysed. Of the sixteen stonefly species that have been recorded, three are now extinct in Flanders (Isogenus nubecula, Taeniopteryx nebulosa and T. schoenemundi), while the remaining species are rare. The occurrence of stoneflies is almost restricted to small brooks, while observations in larger watercourses are almost lacking. Although a few records may indicate that some larger watercourses have recently been recolonised, these observations consisted of single specimens and might be due to drift. Most stonefly population are strongly isolated and therefore extremely vulnerable. Small brooks in the Campine region (northeast Flanders), which are characterised by a lower pH and a lower conductivity, contained a different stonefly community than the small brooks in the rest of Flanders. Leuctra pseudosignifera, Nemoura marginata and Protonemura intricata are mainly found in small brooks in the loamy region, Amphinemura standfussi, Isoperla grammatica, Leuctra fusca, L. hippopus, N. avicularis and P. meyeri mainly occur in small Campine brooks, while L. nigra, N. cinerea and Nemurella pictetii can be found in both types. Nemoura dubitans can typically be found in stagnant water fed with freatic water. Sustainable populations of these stonefly species can only be achieved when their present habitats are adequately protected and in addition, measures should be taken to connect and enlarge the remaining populations.

Sediment-water interactions play an important role in influencing the water quality of aquatic systems. Water quality management of freshwater systems needs to take into account this behaviour, which depends largely on early diagenetic processes that condition the physical and biogeochemical properties of the sediment. Among these processes, the redox transformations resulting from the oxidation of organic matter by the microbial activity have a major influence on the biogeochemical properties of sediments. In particular, these reactions condition the vertical profiles of nutrient concentrations, pH and metals along the sedimentary column. This paper presents a method which couples both experimental and modelling approaches in order to characterise and analyse the biogeochemistry of freshwater sediments. The modelling approach is based on a coupling between biogeochemical processes and interstitial diffusion. As pore water pH influences the behaviour of the biogeochemical species, we have extended these models to allow for the calculation of pH by taking into account the inventory of protons consumed or produced by different biogeochemical reactions. In parallel, an analytical protocol has been developed to obtain vertical distributions of the main physicochemical parameters in natural sediments cores. To illustrate this approach, we apply our method to sediments cores sampled in the Durance, a river in the south-east of France.

I examined ephippial females and males of the Palaearctic Macrothrix hirsuticornis Norman & Brady, 1867 and M. tripectinata Weisig, 1934 (Cladocera: Anomopoda: Macrothricidae). Parthenogenetic and ephippial females, and males of a third species, M. dadayi Behning, 1941, are redescribed on material from the Ciscaucasian coast of the Black Sea (Russia). A series of male characters, useful for species discrimination was found. Ephippia of M. tripectinata and M. dadayi are covered with small spinules, a unique synapomorphy of these species. Recent progress in Macrothrix systematics allows us to predict that the taxonomy will improve as more males and ephippial females (currently known only in half the species), yet especially valuable for systematics, are described.