The intensification of agriculture has drastically modified the structure of rural landscapes, changing field size, destructinghedgerow networks, and increasing nutrients and fine sediments fluxes to rivers. To evaluate the effects of these disturbances atthe catchment scale, we studied the surface and interstitial water chemistry and the invertebrate assemblages in three differenthabitats: the vegetation, the benthic, and the interstitial. Six headwater streams ranging from undisturbed to disturbed forests(wind-fallen area) and from traditional agriculture to intensive farming areas were studied. Differences between forested andagricultural streams lie in changes in water chemistry, in habitat quality, and in the composition of the assemblages with littlereduction in species richness. The forested streams were only disturbed by large-scale modifications of their catchments (i.e.wind-fallen area along the stream), which made the invertebrate assemblages similar to those of agricultural streams, even ifwater characteristics were not modified. In contrast, large scale modifications of landscape structure near the agricultural streams(hedgerow removal) had little effect on the fauna, but the destruction of the riparian strip (with direct access of the cattle to theriver) profoundly affected the system with drastic modifications of in-stream habitat quality and invertebrate assemblagecomposition. The effects of these disturbances differed according to the habitat considered, with increasing differences betweenassemblages from the interstitial, to the benthic, and to the vegetation habitats. Finally, groups of organisms based on bioecologicaltraits appeared as efficient tools for the evaluation of catchment disturbances, at least for the benthic and thevegetation fauna.

To test whether leaf litter from eucalyptus plantations affects stream macroinvertebrate communities, we manipulated litterinputs into a small headwater tributary of the Agüera stream (northern Spain) running under mixed deciduous forests. Threecontiguous 50 m long reaches were used: the upstream reach was left as a control (site C), whereas the two downstream siteswere covered by 1 mm mesh nets to avoid natural litter inputs, and twice a month received litter collected at a deciduous forest(site D, mid) or a eucalyptus plantation (site E, downstream). Benthic Surber samples were taken from the three sites before andafter the treatment and density, biomass and structure of the community were compared. Density and biomass of macroinvertebratesdid not differ among sites before the treatment. Total density and biomass of macroinvertebrates increased in all the sitesduring the experimental period but most considerably at the site were deciduous forest inputs were simulated (station D). At theend of the experiment shredders were significantly less abundant at site E (eucalyptus) than at site D (deciduous). In addition,shredder density and biomass per total organic matter amount and per total leaf amount became higher at site D. In conclusion,these results suggest a subtle negative impact of eucalyptus litter on stream macroinvertebrate communities, especially on shredders.

The green alga Chlamydomonas reinhardtii usually occurs in cultures as single, biflagellated cells. However, C. reinhardtii isknown for its ability to form gelatinous and palmelloid stages that arise as a result of an interaction with its environment.Exponentially growing unicellular C. reinhardtii formed palmelloid colonies rapidly within 25 h when cultured together withtheir enemy the rotifer Brachionus calyciflorus. Consequences of palmelloid formation for population dynamics of both C. reinhardtiiand B. calyciflorus were examined in continuous flow systems. Palmelloids were only formed in a one-stage systemwhere B. calyciflorus grazers and C. reinhardtii prey were cultured together, but not in a two-stage system in which mainly unicellularC. reinhardtii was pumped into a rotifer culture placed in darkness. The rotifer abundance was lower and the algal biomasshigher in the one-stage system compared to the grazing unit of the two-stage system. Inasmuch as palmelloids seemed togive C. reinhardtii cells resistance to grazing, we suggest that at least one of the reasons why C. reinhardtii is capable of formingpalmelloids is to cope with herbivory.

Considerable spatial and temporal variability was detected in the environmental conditions in 30 coldwater springs in southernOntario, Canada. Using standard pyramidal emergence traps, a total of 86 insect species was recorded from these springs (notincluding the Chironomidae). These represented nine taxonomic groups, among which the Limoniidae (Diptera) was the mostdiverse with 38 species. Fifty-five per cent of all species recorded had a low frequency (found at three or fewer sites), and onlyfor very few of these rare species were more than 10 individuals m-2 collected. Interannual differences were also apparent.Continuous sampling over time showed that emergence records from a single year, on average, contained only around 50% ofthe total number of species obtained during the entire study. Species-environment relationships analyzed by CanonicalCorrespondence Analysis indicated that temperature and discharge correlated most strongly with insect community similarityamong spring sites. The prospects for developing regional typologies of coldwater springs, based on their environmental conditions,and the implications of species loss to the continuity of function of coldwater spring ecosystems are discussed.

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.

The aim of this study was to analyse the digestibility and viability of diatoms following gut passage through Aegla uruguayana.Crabs (n=28) and diatom samples were collected from Las Pencas Stream (Entre Ríos Province, Argentina).Organisms were allowed to graze on the source, then they were placed in aquaria to defecate. Samples of faecal and source materialwere analysed microscopically to quantify 'live', 'dying' and 'dead' diatoms, and inoculated onto Chu 10-infused agar culturesto observe cell viability. Significant differences were found among source and faeces content of 'live' and 'dead' cells(p<0.01). Nevertheless, the percentage of digestion after gut passage was only 11.5 %. Both agar cultures produced colonies thatincreased in cell density over time with significantly higher enhancement in faecal treatment (p<0.05). Evidence of digestionresistance and reproductive stimulation by gut passage could be tested in this experience.

Total sediment and water organic carbon and nutrient (nitrogen and phosphorus) concentrations of different environment types ofa Mediterranean coastal wetland (temporary and brackish, temporary and freshwater, semi-permanent and brackish, andpermanent and brackish basins) were analysed during two hydroperiods. A nitrogen limitation was found for both sediment andwater. The total organic carbon concentration of the water was significantly related to the water level, which varies throughoutthe hydroperiods. In contrast, the total organic carbon concentration of the sediment was not related to water level. However,significant differences in total organic carbon of the sediment were found between hydroperiods. On the other hand, total organiccarbon of the sediment varied spatially, being higher in temporary brackish basins with lower sand content, and lower inpermanent and semi-permanent brackish basins with higher sand content.

In French Guyana, the dynamics of young prawn migrations from marine to estuarine waters remains equivocal, raising thequestion of habitat utilization in the adjacent mangrove systems. The temporal distribution of juvenile penaeid species was thusinvestigated in the main drainage channel of a Guianese coastal mangrove. A total of 2275 juvenile prawns belonging to fivespecies, including two penaeid species (Penaeus subtilis, Xiphopenaeus kroyeri) were collected by stake net on four occasionsduring the wet season. Catches were dominated by large-sized, highly-valued P. subtilis and exclusively occurred (a) at the endof flood tide and (b) at the beginning of ebb tide, when water velocity was maximum. Size structures were very similar betweenflood- and ebb tides, suggesting that the same assemblages entered then withdrawed from the mangrove on a given tidal cycle.Residence times of prawns in the mangrove were short (3-4 hours per tidal cycle), as juveniles gained access to the coastal mangroveonly a few hours per day during high tide. These results will need further confirmation at larger (Guianese) scale, but provideevidence for original, tidal-dominated mangrove utilization patterns by juvenile prawns. Given the economic importance ofP. subtilis in French Guyana, there is an urgent need to assess the contribution of coastal mangrove habitats to sustaining nearshore fisheries.

The freshwater scud Echinogammarus stammeri is a very abundant benthic crustacean in riverine systems of northern Italy.The molecular physiology of L-[3H]leucine transport across cell membranes of E. stammeri was investigated. At pH 7.4, thepresence of a NaCl gradient stimulated the leucine transport rate, when compared with KCl gradient. By contrast, alkaline pHstrongly inhibited transport activity. In NaCl medium at acidic pH, leucine uptake displayed a specific activity 2.1-fold lowerthan that measured at neutral pH. Analysis of the uptake as a function of external leucine concentration revealed saturation kinetics.Leucine uptake appeared broadly unspecific and it was much strongly inhibited by the non-polar amino acids phenylalanine,methionine, and BCH, as well as by hydrophobic hydroxyacids. These results revealed important differences with respect toamino acid transport systems described in marine crustaceans. Their relevance in the feeding adaptation of the scud is brieflydiscussed.

Animal populations have a certain synchronization between their fluctuations and the environmental factors which have adirect influence on density, sex ratio and recruitment. Trichodactylus borellianus is a common freshwater crab of theTrichodactylidae family, originary from South America. This crab is omnivorous and grazes upon the littoral communities. Thepresent study is the first analysis of the natural distribution and population dynamics of freshwater crabs in La Plata Basin(Argentina) and their relationship with certain abiotic and biotic parameters. It was carried out in three environments (riverinezone of streams and river) of the Paraná River floodplain. Crab populations were sampled monthly from August 2001 to October2002. The mean crab abundance among the study sites was significantly different, being lower in samples from the environmentsurrounding the principal channel of the Paraná River. Crab density showed two peaks: the highest occurred during late winterand early spring, and the lowest during late summer. Males were only more abundant in late winter and spring. In spring, summerand autumn, the population showed a contagious distribution. The population displayed a regular arrangement in winter.From mid-spring to mid-autumn juveniles were very frequent whereas adults predominated the rest of the year. Total crab numberin the stream nearest to the main channel varied according to the level and temperature of the river. In the other sites, locatedfurther from the main channel of the Paraná River, crab numbers and vegetation biomass showed a more similar arrangementwith a higher correlation.

This study evaluated the status of the Asian clam Corbicula fluminea (Müller, 1774) in the River Lima estuary (Portugal),which it first invaded in 2002. During the summers of 2004 and 2005, spatial and temporal variations in the abundance, biomassand population structure of C. fluminea were investigated in this estuary. This species was present in a limited intertidal area ofthe estuary and was rarely found in the subtidal zone. Its abundance and biomass were considerably lower than those found inother estuarine systems. Based on these studies it appears that salinity fluctuations and possibly other factors such as nutrientsand environmental contaminants are keeping this invasive species from reaching its full potential. Given the lower abundanceand biomass recorded and the restrict distribution of the species in this estuary, the eradication of this nonindigenous invasivespecies is still possible. The findings of this study may be useful for the management of this species not only in the River Limaestuary but also in other locations it may invade.

The habitat preferences, temporal dynamics in density and the life history of two species of mayflies, Metamonius anceps andMeridialaris chiloeensis, were investigated in a Patagonian mountain stream over a period of one year. Benthic samples weretaken in a low order Nothofagus forested stream. M. anceps was univoltine with small nymphs predominating in winter andemergence occurring in summer. M. chiloeensis showed a bivoltine life cycle with a winter and summer generation, andemergence period in spring and summer. Both species were significantly more abundant in the low water period than in the highdischarge season. Gravels supported significantly more individuals of M. chiloeensis than sand in pools and leaf packs. Temporaloverlap of abundance between species was low. The existence of different life history strategies and the temporal shift of maingenerations and density peaks were critical to allow species coexistence.

Artificial Neural Network models (ANNs) were used to predict habitat suitability for 12 macroinvertebrate taxa, usingenvironmental input variables. This modelling technique was applied to a dataset of 102 measurement series collected in 31sampling sites in the Greek river Axios. The database consisted of seven physical-chemical and seven structural variables, as wellas abundances of 90 macroinvertebrate taxa. A seasonal variable was included to allow the description of potential temporalchanges in the macroinvertebrate communities. The induced models performed well for predicting habitat suitability of themacroinvertebrate taxa. Senso-nets and sensitivity analyses revealed that dissolved oxygen concentration and the substratecomposition always played a crucial role in predicting habitat suitability of the macroinvertebrates. Although ANNs are oftenreferred to as black box prediction techniques, it was demonstrated that ANNs combined with sensitivity analyses can provideinsight in the relationship between river conditions and the occurrence of macroinvertebrates, and thus deliver new ecologicalknowledge. Consequently, these models can be useful in decision-making for river restoration and conservation management.

The lichen flora of freshwater habitats in the Italian Alps is reviewed: 20 genera and 43 species are known, of which crustoselichens with sexual reproduction prevail. Freshwater lichen richness is highest near the treeline on siliceous substrata in exposedand well-lit sites. The importance of several ecological factors on freshwater lichen distribution and ecology is discussed.

In order to assign 18 mayfly taxa found in streams in the Macaé River basin into Functional Feeding Groups, the anatomy of their feedingapparatus was examined through scanning electron microscopy. Also, habitat preference and field observations of feeding behaviour were madeto assure FFG assignment. Ephemeropteran taxa were classified into five FFGs: Passive Filterers - Hylister plaumanni; Active Filterer -Lachlania boanovae and Campylocia sp.; Brushers - Askola froehlichi, Farrodes carioca, Hagenulopsis spp., Massartela brieni, Miroculis froehlich,Miroculis sp., and Thraulodes spp; Grazers - Cloeodes spp., Americabaetis spp., Camelobaetidius spp.and Baetodes spp.; Scrapers -Leptohyphes pereirae, Leptohyphes spp., Tricorythodes spp. and Tricorythopsis spp. Species of the three best represented mayfly families insouth-east Brazil were assigned to different FFGs (Leptophlebiidae - Brushers; Baetidae - Grazers and Leptohyphidae - Scrapers), with oneexception, Hylister plaumanni (Leptophlebiidae; Active filterers). This information is useful to understand the role of mayflies in stream ecosystems,and to help the development of ecological theories for tropical streams.

Field investigations in two lymnaeid habitats located along river banks were carried out over three years to study snailcolonization in relation to water-level variations, to determine the number of annual generations, and to analyse the ability ofG. truncatula to emerge from water. As these river banks were located 6.7 km upstream from a dam, water recedes each day,thus permitting the study of snails on banks for several hours per day. From March to December, snails followed seasonal variationsof water-level. However, only a few G. truncatula were observed following the daily retreat of water. Two annual generationsof G. truncatula, the first from the onset of July and the second in December, were noted in these habitats. When waterreceded each day, the mean distance covered by non-aestivating snails ranged from 25 to 44 cm. However, they escaped waterrise by seeking refuge in still emerged zones of their habitats. From July to October, snails following each day water recedingshowed a significantly quicker growth than that of G. truncatula which only moved in the same zone of their habitat. Populationsof G. truncatula living along these river banks would be completely adapted to their habitat. The escape of snails from waterrise between July and October might correspond to a physiological reaction of survival when a too rapid increase of water-leveloccurs.

Mediterranean temporary ponds (MTPs) are highly distinctive habitats with intermittent and unstable environmental conditions,inhabited by several rare and endemic plant and animal species. Temporary pond ecosystems have been classified asendangered all over the world; nevertheless, they are disappearing at a high rate, especially in the Mediterranean region. MTPsare a priority habitat under the European Union Habitats Directive and thus appropriate management and conservation effortsshould be applied. Further research is needed in order to better understand the environmental characteristics and ecology of thishabitat which is not always the case in many countries. In this study a range of environmental data were collected from the GreekMTP habitat sites including the altitude, the geology, the representativity, the ecological status and other biological data aimingto assess the environmental status of all known Greek MTPs. Statistical analysis were performed and thematic maps were createdusing a Geographical Information System (GIS). Greek MTP’s were classified according to their characteristics and habitatpressures were identified and further analysed. A comparison between the present environmental status of the MTPs in Greecewith the MTPs in other Mediterranean countries was undertaken and relevant conservation and management measures were proposed.The outcome of this study was that a significant percentage of the MTP habitat sites in Greece are at risk mainly due tohuman activities, such as agricultural pollution, expansion of cropland and water resources over-exploitation. It was concludedthat immediate restoration and conservation actions should be taken so as to prevent further ecological degradation.

We studied the effects of a waste water treatment plant on organic matter dynamics in Fosso Bagnatore, a Mediterraneanstream near Rome (Italy). Concentrations of dissolved organic carbon and seston, along with the standing crops of coarse benthicorganic matter and fine benthic organic matter, were monitored monthly during 2002 in two reaches situated upstream anddownstream of a waste water treatment plant effluent. Additionally, we examined two stream functional characteristics: wholestream metabolism, which was measured from diel changes in oxygen concentrations, and nutrient removal, which was studiedby experimental additions of NH4-N, NO3-N and PO4-P. The possible influence of WWTP organic matter alterations on ecosystemfunctioning was addressed by measuring epilithon characteristics (standing crop, C:N:P ratios and chlorophyll a content).The WWTP effluent caused an increase (several-fold) of DOC and seston concentrations, and FBOM standing crop, moreoverit modified their temporal variation. Downstream of the wastewater treatment plant we detected an higher heterotrophic microbialbiomass and a correspondent higher community respiration. The uptake of NH4-N, NO3-N and PO4-P was highly variableprobably as consequence of the high variability of the compartments involved (e.g. DOC, FBOM, community respiration). Weshowed that WWTP effluent altered the organic matter dynamics of this Mediterranean-type headwater stream and that theseeffects were reflected in its ecosystem functioning. Because of the linkage of headwaters to downstream ecosystems and due totheir significant role in landscape and catchment processes, the alterations of organic matter dynamics that we detected at a localscale may have important consequences on a broader scale.

Obtaining an adequate and representative sample is a continuing challenge of community ecology. The present study focuseson what sample area represents adequately the structural composition of the caddisfly fauna of a riffle, at a given sampling occasion.Sixty-two Surber samples were collected from a riffle in a second-order reach of the Bernecei Stream (BörzsönyMountains, Hungary). This data set was used to estimate sample representativeness at different sample sizes (from 1 to 31 Surbersamples, 0.09 m2 - 2.79 m2) generated a re-sampling procedure. Sample representativeness was measured with mean JaccardCoefficient and Bray-Curtis Index between samples for species presence-absence data and abundance data, respectively. Wefound that a sample size of 2.25 m2 represented well (mean similarity 0.998) the species composition of the caddisfly fauna ifrare species were excluded from the analysis. In contrast, sample representativeness of species composition proved to be relativelylow (0.719) if rare species were included in the analysis. Curves of sample representativeness based on both raw-, or transformedabundance data were less sensitive to the presence of rare species and showed lower representativeness than samplerepresentativeness based on presence/absence data.

There is very little information on the genus Branchiobdella and the species relationships with their freshwater crayfish hosts inCroatia. Therefore, a base-line study was needed so that future changes in available habitat brought about by urban developmentand the probable introduction of non-native species can be accurately assessed. This investigation used preserved freshwatercrayfish collected from across Croatia between 1995 and 2005 as its source of the ectosymbionts. Crayfish species includedAstacus astacus, A. leptodactylus, Austropotamobius pallipes, A. torrentium, and the allochtonous North American species,Orconectes limosus. Only native European species of branchiobdellids were found: Branchiobdella astaci, B. parasita, B.pentodonta, B. hexodonta, B. italica, and B. balcanica, and this is the first report on the occurrence of these species, apart from B.italica, in Croatia. The distribution of these branchiobdellidans is compared with climatic and river drainage systems, andliterature reports of populations in other countries in the region.