Nous avons étudié les réponses biologiques des individus, populations et communautés d'invertébrés de rivières à la contamination des sédiments par les métaux lourds. Nous avons examiné les malformations du mentum des larves de Chironomus riparius (Insecta-Diptera) pour évaluer l'effet toxique de la contamination d'un cours d'eau, Le Genna (Italie Centrale). L'aire d'étude est soumise à une activité zootechnique intense qui accroit la pollution métallique de la rivière, notamment par le cuivre, le zinc, le cadmium, le chrome et le nickel. La fréquence des malformations larvaires (56%) a été directement liée aux contaminations, ce qui montre quel es malformations du mentum constituent un proxy pertinent des effets toxiques sur les écosystèmes. Nous avons également analysé, dans une aire industrielle d'Italie Centrale, la bioaccumulation de métaux lourds dans les tissus de Procambarus clarkii (Crustacea-Decapoda), une écrevisse allochtone utilisée comme bioindicateur de la santé écologique des eaux douces. L'hépatopancréas, tissus de détoxification, a montré les concentrations de métaux les plus élevées, en comparaison aux muscles abdominaux (tissus non détoxifiant). Ce ratio de concentration entre les deux types de tissus représente un marqueur pertinent du niveau de stress bio-écologique. Le rapport décroit comme suit : Cd (11,7) > Cu (5,5) > Pb (3,6) > Cr (1,5) > Zn (1,0), Ni (1,0). La comparaison des bioaccumulations avec un site de référence non impacté confirme quel es métaux qui s'accumulent de façon significative dans l'hépatopancréas sont le cadmium et le cuivre. A l'échelle des communautés, nous avons étudié les relations entre combinaison de traits fonctionnels des invertébrés et conditions environnementales (24 variables physico-chimiques) à l'échelle du réseau hydrogaphique (bassin du Nestore, Italie Centrale). Les stations de bonne qualité physico-chimique ont montré une plus forte variabilité dans la composition en traits fonctionnels que dans les conditions physico-chimiques. Un résultat inverse a été observé aux sites pollués, où les traits biologiques sont peu diversifiés et stables dans l'espace et dans le temps, en relation avec la chute de diversité taxonomique liée aux perturbations anthropiques. Enfin, les traits fonctionnels se sont avérés plus efficaces quel es analyses physico chimiques pour détecter des changements de fonctionnement écologique lors que les concentrations en polluants sont faibles. Les cartes auto-organisatrices de Kohonen (SOM, réseaux de neurones) ont permis de modéliser plus en détailla distribution spatio-temporelle des divers taxons en relation avec la variabilité environnementale naturelle et le niveau de pollution chimique (nutriments et métaux lourds). Nous avons enfin développé et validé un indice multimétrique basé sur les communautés d'invertébrés, pour évaluer la santé écologique des cours d'eau d'Italie Centrale en terme d'écart à la référence. Sur 71 métriques biologiques testées, nous n'avons retenues que celles qui présent le meilleurs compromis en terme d'efficacité de discrimination, de faible spécificité et de faible redondance, et montrant une grande stabilité en conditions de référence. Ces métriques, qui renseignent sur la diversité, l'abondance, le rôle fonctionnel et la tolérance des organismes sont : l'indice de Margalef, le score "Biological Monitoring Water Pollution", le nombre de familles et la richesse relative des déchiqueteurs. Cet indice, qui satisfait les pré requis de la Directive Cadre sur l'Eau de l'Union Européenne, répond de façon significative à la pollution des eaux douces et à la contamination des sédiments par les métaux lourds. / We studied the biological responses of individuals, populations and invertebrate communities to river sediment contamination by heavy metals. We examined the deformities of the mentum of Chironomus riparius larvae (Insecta, Diptera) to assess toxic effect of contamination of streams, the Genna (Central Italy). The study area is subjected to intense livestock activity that increases the metal pollution of the river, including copper, zinc, cadmium, chromium and nickel. The frequency of larval malformations (56%) was directly related to contamination, which shows that malformations of the mentum form a relevant proxy of toxic effects upon ecosystems. We also analyzed, in an industrial area of Central Italy, the bioaccumulation of heavy metals in the tissues of Procambarus clarkii (Crustacea-Decapoda), a non-native crayfish used as a bio-indicator of the ecological health of freshwaters. The hepatopancreas, a detoxifying tissue, showed the highest metal concentrations compared to the abdominal muscles (non detoxifying tissue). This concentration ratio between the two types of tissues is a relevant marker of bio-ecological stress. The ratio decreased as follows: Cd (11.7) > Cu (5.5) > Pb (3.6) > Cr (1,5) > Zn (1.0), Ni (1.0). Comparison of bioaccumulations with a non-impacted reference site confirms that those metals that significantly accumulate in the hepatopancreas are cadmium and copper. At the community level, we studied the relationships between the combination of invertebrate functional traits and environmental conditions (24 physical-chemical variables) across the stream system (Nestore Basin, Central Italy). Stations with a good physical-chemical status showed higher variability in their composition of functional traits than in their physical-chemical variables. An opposite trend was observed in the polluted sites, where biological traits are poorly diversified and stable in space and in time, in relation to the decrease in taxonomic diversity linked to human disturbance. Finally, functional traits have proven more effective than physical-chemical analyzes in detecting changes in ecological functioning of streams when contaminant concentrations are low. The self-organizing map algorithm (SOM neural networks) was used to further model the spatial and temporal distribution of the various taxa in relation to the natural environmental variability and the level of chemical pollution (nutrients and heavy metals). Finally we have developed and validated a multimetric index based on invertebrate communities, to assess the ecological health of rivers of Central Italy in terms of deviation from a reference state. Out of 71 tested biological metrics, we retained those metrics that showed the best compromise in terms of discrimination efficiency, low specificity and low redundancy, and higher stability under reference conditions. These metrics, which provide information on the diversity, abundance, functional role and tolerance of organisms are: the Margalef index, the "Biological Monitoring Water Pollution" score, the number of families and the relative richness of shredders. This index, which complies with the prerequisites of the Water Framework Directive of the European Union responds significantly to freshwater pollution and sediment contamination by heavy metals.

Abstract In this thesis I studied lotic trout predation and its ecological effects, and investigated invertebrate predator-prey interactions under natural and anthropogenically modified flow conditions. Given the growing concern about the reliability of extrapolations from small-scale studies to larger spatio-temporal scales, results of mechanistic small-scale experiments were scaled up by linking them to large-scale field surveys. An intensive survey assessed changes in diel feeding periodicity, prey selection and daily ration of juvenile brown trout (Salmo trutta L.) over the course of the open water period. This survey provides the first field estimates of juvenile brown trout daily rations and indicates crepuscular feeding peaks. Trout selectively preyed on medium- to large-sized prey, shifting towards epibenthic feeding with increasing availability of suitable prey. In a small-scale field experiment, trout displayed clear size-related predation concentrating on invertebrate predators and cased caddisflies, a pattern that scaled up successfully in large-scale surveys. Further, predation effects on large-sized prey were also repeated in a meta-analysis on lotic salmonid predation. While dense blackfly populations in lake-outlet streams are common, mass outbreaks of blackflies in short-term regulated rivers are poorly studied. In our studies the principal invertebrate predator of vernal benthic communities, the caseless caddisfly Rhyacophila, displayed significant preference for blackflies and was almost unable to capture any other prey, thus resulting in passive selection for larval blackflies. Rhyacophila larvae displayed highest capture success in intermediate current velocities, whereas further increases in current velocities decreased capture success. Short-term regulation releases increased both predator and prey drift but, unlike for Rhyacophila, magnitude of drift was unrelated to substrate for blackflies. Indeed, field observations indicated that blackflies rarely face detrimental effects of short-term regulation due to their fast growing rates and early emergence. Moss was the most preferred habitat of Rhyacophila and provided the best buffer against sudden increases in current velocities. These results suggest that several factors maintain spring-time outbreaks of blackfly populations in short-term regulated rivers: exaptation of the dominant blackfly species to prevailing conditions, degradation of the key habitat of the predator, and recurring annual drift losses and diminished capture success of Rhyacophila during short-term regulation releases.

Abstract In this thesis, I studied the patterns in the assemblage composition as well as the biogeography and ecology of spring macroinvertebrates and bryophytes in Finland. My main objectives were to assess the importance environmental variables to macroinvertebrate and bryophyte assemblage composition in springs at the level of multiple spatial scales. In addition, I assessed the importance of springs in the boreal mire landscape, and sought the ecological and environmental determinants of a key species in boreal springs. In a large-scale study, I also examined the concordance between macroinvertebrates and bryophytes across boreal ecoregions, and assessed how macroinvertebrate assemblage variation corresponds to terrestrially-based ecoregions. Locally, spring macroinvertebrate assemblage structure displays high variation between different kinds of mesohabitats within springs, highlighting the importance of careful sampling of all habitat types in spring surveys. Helocrenes and other aquatic-terrestrial ecotone habitats harbour the highest species diversity and most spring-dependent species among spring habitat types. Further, spring-influenced mire patches were shown to have distinct cranefly assemblages in the mire landscape and to harbour higher cranefly diversity than mire types with lower trophic status, emphasising the importance of springs for mire biodiversity. Regionally, a red-listed spring-dependent caddisfly species appeared to be a surrogate for a high spring conservation value, indicating high overall species diversity and the occurrence of additional red-listed species. On a large geographical scale, intersecting the boreal ecoregions, a pattern of gradual change of benthic macroinvertebrate assemblage composition from south to north was detected, largely corresponding to terrestrially-derived ecoregions. However, the physical attributes of springs also need to be taken into account in bioassessment studies. Macroinvertebrate assemblage variation also correlated with physical habitat-scale variables, but not with changes in water chemistry. In contrast, spring bryophyte assemblages showed a distinct response to variation in water chemistry, but not to variation in physical habitat characteristics. Bryophytes and insect assemblages were concordant with each other on the large geographical scale, although the concordance was rather weak. Because of their different kind of responses to the physical and chemical variables, insects and bryophytes of springs are poor surrogates for each other in boreal springs.

Disturbance is a central factor shaping composition, structure, and dynamics of local communities. Drying is a disturbance that occurs in aquatic ecosystems globally and can strongly influence their communities. Although the effects of drying may depend on ecosystem connectivity and the dispersal abilities of resident species, there have been no comparisons of community responses to drying between lentic and lotic ecosystems across different climates. Here, we predicted that drying would have stronger effects on aquatic communities in isolated lentic ecosystems than in dendritic lotic ecosystems, owing to the higher hydrological connectivity of the latter, and that drying would have stronger effects on passive than on active dispersers, because of the potentially higher recolonizing ability of the latter. We tested these predictions by comparing alpha diversity, phylogenetic relatedness, and beta diversity for active and passive dispersers, in both ecosystem types across five climatic regions. Drying caused greater declines in alpha diversity in lentic than in lotic ecosystems. Communities that experienced drying were more similar to one another than those of perennial sites, and this pattern was especially pronounced in lentic ecosystems. In contrast, drying did not influence the contributions of turnover and richness gradients to beta diversity. Additionally, dispersal mode did not influence community responses to drying. Relatively weaker effects of drying in lotic compared to lentic systems were likely due to the hydrological connectivity among perennial and temporary river sites, which may facilitate dispersal of organisms to escape drying and recolonize rewetted sites. Collectively, our results suggest that habitat connectivity may ameliorate (and fragmentation may worsen) the impacts of drying disturbance. This is an important finding in light of increasing drying and concomitant aquatic habitat fragmentation under global change.

There is a paucity of data on dry forests, the most threatened biome in the tropics. The Nandamojo is a tropical dry forest watershed in Western Costa Rica that has been impacted by varying degrees of human induced modifications. This research was conducted to examine the influence of land use and channel characteristics on invertebrate communities within a sub basin of the Nandamojo watershed. This study addressed three hypotheses: (1) sites with low tree cover and small riparian buffer zones will have high erosion, (2) macroinvertebrate abundance will be lower at sites with low channel stability values, and (3) benthic macroinvertebrate abundance will be higher in years of high rainfall and flow regimes. Sites were established along three tributaries, which were surveyed in 2013 and 2015. Data were compared (1) along the length of respective tributaries and their elevation gradients, and (2) between survey years. Although Nandamojo is a mixed land use watershed, two of the four land uses were dominant; pasture and forest. Macroinvertebrate counts were statistically different across survey years and seasons. The abundance of macroinvertebrates was greatest on Tributary 3, where the dominant land use was forest. Regional interannual rainfall is suggested as a driving factor for interannual differences in macroinvertebrate abundance. Although results suggest that this sub basin is in good health, taking preventative action by developing a subbasin management plan is needed. As tropical dry forest is the most threatened forest biome, educating local residents not only about the numerous risks of human induced modifications such as forest to pasture land conversion, but also the corresponding importance of maintaining riverbank vegetation in headwater streams should be a foremost priority.

Os sistemas lóticos são considerados sistemas abertos e de fluxo unidirecional de energia. Nestes sistemas a intensa relação com o meio terrestre adjacente faz com que as condições ecológicas dos rios sejam um reflexo das transformações ocorridas em sua bacia de drenagem. O objetivo do presente estudo foi traçar um perfil dos aspectos ecológicos do rio Uberaba-MG, em função dos usos preponderantes da bacia hidrográfica. Foram avaliadas as características limnológicas, a comunidade de macroinvertebrados bentônicos e o estado de conservação da área de entorno do rio. Procurou-se ainda avaliar a evolução espacial e a variação temporal das variáveis mensuradas à luz de teorias ecológicas de sistemas lóticos. Os resultados mostraram que no rio Uberaba três zonas com impactos preponderantes, diferentes, devem ser avaliadas com maior cautela: a) antes do município de Uberaba existe a predominância de atividades agrícolas, que promovem impactos pela entrada contínua de sedimentos e oferecem riscos pela entrada de agrotóxicos e fertilizantes, b) abaixo do município de Uberaba, a entrada de efluentes gera acentuada degradação da qualidade da água e o conseqüente perecimento das comunidades biológicas, até a região próxima ao município de Veríssimo, e c) a região compreendida entre os municípios de Veríssimo, Conceição das Alagoas e Planura, pelo crescente risco de degradação da qualidade da água decorrente da entrada de efluentes e do aumento do desmatamento nas margens do rio Uberaba e afluentes. Discute-se ainda a necessidade de serem aprimoradas teorias ecológicas para sistemas lóticos tropicais, com o intuito de aumentar a capacidade de predição sobre este sistema e remeter estratégias de conservação mais eficientes aos gestores ambientais. / Lotic systems are considered opened and one-way energy flux systems. In these cases, the intense relationship with adjacent terrestrial environment renders rivers ecological conditions a reflex of transformations occurred at its watershed. The present study aimed to profile an Uberaba river ecological features as a function of the watershed main uses. Limnological characteristic, benthic macroinvertebrates community and conditions at river nearby area were evaluated. Based on the lotic systems ecological theories, it was attempted to evaluate the measured variable space evolution and temporal variation. Results showed that in Uberaba river, three zones with different impacts should be carefully evaluated: a) before Uberaba city, agricultural activities predominates, promoting impacts due to the continuous sediment input, and offering risks of pesticide and fertilizers contribuition; b) below Uberaba city, wastewater effluent generates high water quality degradation, resulting in biological communities decay until the area closed to Veríssimo City; and c) at the region embracing Veríssimo, Conceição das Alagoas and Planura cities, in function of the growing water quality degradation risk due to effluents entrance and deforesting increase at the margins of Uberaba river and tributaries. The needs of improved ecological theories for tropical lotic systems are also discussed, aiming to increase the prediction capacity on this lotic systems and to transmit more efficient conservation strategies to environmental managers.

ABSTRACT A review of annual monitoring reports for stream restoration projects on surface coal mines in the central Appalachian Mountains found that the criteria used for judging the success of the projects was generally based on visual assessments of habitat structure which were evaluated using the Rapid Bioassessment Protocol (RBP) (Palmer and Hondula, 2014). In recent years the Hydrogeomorphic Approach (HGM), which was originally developed to evaluate wetlands, has been adapted for stream evaluations as well (Summers, et al., 2017). Both of these methods are primarily a means to determine if suitable habitat structure and riparian growth are present to support aquatic life. It is assumed that if habitat structure is suitable then macroinvertebrate and other life will be present. However, each of these two methods place emphasis on different aspects of habitat and riparian structure. The primary purpose of this project is to compare and contrast how effective these two methods are at evaluating reconstructed streams on surface coal mines. A secondary objective is to determine if macroinvertebrate assemblages in reconstructed streams is significantly different from that of reference streams not impacted by mining. Research on benthic community structure downstream of coal mining activities suggests that even after many decades taxa richness and abundance still have not recovered from indirect impacts (Petty, et al., 2010). Information on reconstructed streams directly impacted is lacking. This project evaluates streams that were reconstructed five years prior using the RBP and HGM methods, and compares them to local reference streams that have minimal to no mining impacts. Multiple benthic metrics are also used to evaluate community structure. REFERENCES Petty, J. Todd, Jennifer B. Fulton, Michael P. Strager, George T. Merovich Jr., James M. Stiles, and Paul F. Ziemkiewicz. 2010. Lanscape indicators and thresholds of stream ecological impairment in an intensely mined Appalachian watershed. Journal of the North American Benthological Society, 29(4): 1292-1309. Palmer, Margaret A., and Kelly L. Hondula. 2014. Restoration as mitigation: analysis of stream mitigation for coal mining impacts in southern Appalachia. Environmental Science and Technology 48: 10552-10560. Summers, Elizabeth A., Chris V. Noble, Jacob F. berkowitz, and Frank J. Spilker. 2017. Operational Draft Regional Guidebook for the Functional Assessment of High-Gradient Headwater Streams and Low-Gradient Perennial Streams in Appalachia. ERDC/EL TR-17-1.

No description available.

<p>Aquatic macroinvertebrates of channelized headwater streams in agricultural landscapes are exposed to alterations in chemistry and physical characteristics of benthic sediments. These habitat alterations are known to influence communities of aquatic macroinvertebrates. Benthic sediments can have a wide range of impacts and influences on aquatic macroinvertebrates. I hypothesized that sediments would play a significant role in determining macroinvertebrate community structure within agriculturally dominated headwater streams. I evaluated the influences of sediment chemistry characteristics and physical characteristics on aquatic macroinvertebrate communities in Cedar Creek, Indiana and Michigan, and the Upper Big Walnut Creek, Ohio, during 2017 and 2018. Macroinvertebrates were collected twice per year using artificial substrate and leaf pack samplers and identified to the family level. Sediments were sampled two times per year and analyzed for seven physical characteristics and twenty sediment chemistry characteristics. Principle component analyses were used to create axes that are indicators of gradients of sediment chemistry and physical characteristics that occur among the samples. Macroinvertebrate community metrics used in the analyses included abundance, Shannon Diversity Index, Hilsenhoff Biotic Index scores, Invertebrate Community Index scores, percentage of collector-filters, percentage of scrapers, percentage of Chironomidae and a Berger-Parker Reciprocal Index of dominance. Linear Mixed Effect Model analyses revealed that both sediment chemistry and physical characteristics influence macroinvertebrate community metrics. Aquatic macroinvertebrate abundance was negatively correlated with increasing concentrations of simazine and decreasing concentrations of calcium. Percentages of Chironomidae were positively correlated with increasing percentages of sand and decreasing percentages of clay and decreasing diversity of sediment particle sizes. My data supported the hypothesis that benthic sediments play an important role in determining aquatic macroinvertebrate community structure in headwater streams of agriculturally dominated landscapes. Gradients of chemical characteristics containing simazine and calcium were observed to be negatively correlated with macroinvertebrate abundance. Gradients of physical characteristics including percentages of sand and clay along with the diversity of particle sizes were observed to be positively correlated with percentage of chironomids. My research increases the knowledge that benthic sediments, chemically and physically, can lead to alterations in aquatic macroinvertebrate communities within Midwestern headwater streams. </p>

Degraded rivers and streams caused by disturbances have created a need for reliable tools to assess the ecological status of such ecosystems. Numerous methods and programs have been developed to assess ecological status using biological indicators, benthic macroinvertebrates are the most commonly used biotic indicator. The Hester-Dendy multi-plate sampler is a commonly used tool for sampling benthic macroinvertebrates, but its effectiveness under different environmental conditions has not been adequately tested. The aim of this study was to investigate if HD samplers assess the benthic macroinvertebrate community equally under different flow conditions. I investigated if the colonization of BMI in a constant flow differed from that of a variable flow (simulating a hydropeaking flow regime). This was studied using six aquariums, three as control with constant flows and three with variable flow conditions. One Hester-Dendy sampler and 50 benthic macro invertebrates from five different taxonomic orders were place in each aquarium. After five days of colonization the Hester-Dendy samplers were retrieved and benthic macroinvertebrates colonizing the Hester-Dendy samplers and still remaining in the aquariums were collected, preserved and analysed. Results showed that the mean sampling efficiency did not differ between the two treatments. On the other hand species diversity calculated from Shannon-Wiener index was significantly higher in the control treatment than in the variable flow treatment. The lower species diversity in the variable flow treatment is consistent with previous research on benthic macroinvertebrates affected by hydropeaking powerplants. These results can be seen as an indication of how a variable flow regime might affect the samples collected by HD samplers in a natural environment. As the artificial environments created are greatly different from a natural environment, this result might not therefore be representative in a natural environment. / Vattendrag kraftigt påverkade av antropogena störningarna har skapat ett behov av tillförlitliga verktyg för att kunna bedöma dessa vattendrags ekologiska status. Många olika metoder och program har utvecklats genom att använda olika biologiska indikatorer. Bentiska makroevertebrater är en av de vanligaste biotiska indikatorerna. En vanlig metod för att prov ta bentiska makroevertebrater är Hester-Dendy provtagaren. Syftet med denna studie var således att testa om provtagningseffektiviteten för Hester-Dendy provtagare påverkas olika av ett variabelt vattenflöde jämfört med ett jämnt vattenflöde. Detta studerades i sex akvarium, där tre akvarium agerade kontroll och utsattes för ett jämt flöde samt tre akvarium med variabelt flöde. En Hester-Dendy provtagare och 50 bentiska makroevertebrater från fem olika taxonomiska ordningar placerades i varje akvarium. Efter fem dagars koloniserings tid hämtades Hester-Dendy provtagarna och de bentiska makroevertebrater som koloniserade provtagaren såväl som akvariet bevarades i etanol och analyserades i labbet. Resultaten visade att den genomsnittliga provtagningseffektiviteten inte skilde sig åt mellan de två behandlingarna. Däremot var artdiversiteten beräknad med Shannon-Wiener-index signifikant högre i kontrollbehandlingen. Den lägre artdiversiteten i behandlingen med variabelt flöde stämmer överens med tidigare forskning om bentiska makroevertebrater påverkade av korttidsreglerande vattenkraftverk. Resultaten i denna studie bör ses som en indikation av hur ett varierande flöde kan påverka provtagnings effektiviteten hos en Hester-Dendy-provtagare. Detta med anledning av att den konstgjorda miljön som försöket utfördes i är vitt skilt från organismernas naturliga miljö vilket kan ha påverkat resultatet.