O presente trabalho teve como objetivo testar se os fatores ambientais cobertura vegetal, estrutura ambiental, vazão e características físicas e químicas da água (pH, oxigênio dissolvido, temperatura da água e condutividade) podem predizer a abundância, a diversidade e a composição de Chironomidae em riachos. As coletas foram realizadas em riachos localizados nos núcleos Santa Virgínia e Cunha-Indaiá, Parque Estadual Serra do Mar, Estado de São Paulo, e suas adjacências, nos meses de outubro de 2006 e outubro e novembro de 2007. Em cada riacho a fauna associada a 25 rochas (com aproximadamente 20 centímetros de diâmetro) foi coletada. Foram coletados 3758 indivíduos distribuídos em 71 táxons. A riqueza estimada para a região, através do método de Jacknife 2, foi de 105 táxons. Os coeficientes parciais estimados a partir da regressão linear múltipla demonstraram que a cobertura vegetal teve influência significativa sobre a abundância e o oxigênio dissolvido sobre a riqueza. Nenhum fator ambiental foi preditivo da composição faunística. Riachos que apresentaram as maiores vazões e os menores escores do RCE apresentaram menores valores para a diversidade beta / This study aimed to test the effects of vegetation cover, environmental structure, discharge and physical and chemical characteristics (pH, dissolved oxygen, water temperature and conductivity) on the abundance, diversity and composition of Chironomidae fauna in streams. The sampling was done in streams from Parque Estadual da Serra do Mar (Núcleos Santa Virgínia e Cunha-Indaiá) and neighborhoods, in October 2006, and October and November 2007. In each stream, the individuals of Chironomidae associated to 25 individual stones were sampled. The total of 3758 individuals in 71 taxa was collected. The richness, estimated by Jacknife 2, to the streams of the studied region was 105 taxa. The partial coefficients estimated by multiple linear regression showed that canopy cover was related to the abundance and the dissolved oxygen to the richness. No environmental factor was predictive of faunistic composition. Larger size and lower RCE scores streams presented lower beta diversity.

As land use transformations are the main driver of biological diversity loss at the global scale, it is essential to provide predictions and understanding of their impacts in order to improve the mitigation of ecosystem perturbations. The first objective of this project was to describe the response of biological assemblages along a gradient of urbanization and to compare metrics of watershed imperviousness in order to determine, as has been suggested in the literature, whether effective imperviousness, which represents the proportion of impervious area directly connected to the stream by storm sewers, is a better predictor of stream impairement than total imperviousness in the watershed. Decline in sensitive taxa abundance is initiated at 14% total imperviousness and 3% effective imperviousness in the Ottawa-Carleton region and, total and effective imperviousness have equivalent predictive power. The second objective of this project was to describe how the structure of metazoan assemblages in urban streams, as described by size spectra attributes (i.e. slopes, intercepts, number of logarithmic size classes occupied, and residual variance), varies with watershed size, land use and water quality. Streams size spectra of the Ottawa-Gatineau region have relatively shallow slopes, reflecting relatively higher densities of organisms in the larger size classes compared to other ecosystem types (e.g. lakes, oceans, soils, coastal waters). Size spectra slopes, density corrected for size, number of size classes, and residual variance vary predictably along gradients of watershed size, watershed proportion of natural land use and periphyton chlorophyll a. A systematic trend of declining spectra slopes with increasing periphyton biomass suggests that ecological efficiency declines in urban eutrophic streams.

Alterações antrópicas em ecossistemas aquáticos exigem medidas de recuperação dos ambientes degradados, destacando-se projetos de restauração ecológica. Uma das etapas cruciais nesses projetos é a fase de monitoramento, sendo que o uso de macroinvertebrados como bioindicadores apresenta-se como uma importante ferramenta, por eles oferecerem vantagens sobre outros métodos de avaliação. Assim, o objetivo foi verificar os efeitos do assoreamento, antes e depois do rompimento da barragem de um pequeno reservatório em um riacho tropical, sobre a assembleia de macroinvertebrados aquáticos e avaliar a resposta da estrutura da comunidade após a implementação de um projeto de restauração ecológica. A pesquisa foi conduzida no riacho da Campininha, que passou por diversas alterações antrópicas, destacando-se aqui o rompimento de uma barragem e posteriormente a todos esses distúrbios pela implementação de um projeto de restauração ecológica. Foi realizada revisões da literatura para verificação da aplicabilidade da comunidade de macroinvertebrados como bioindicadores de sedimentação e na avaliação de projetos de restauração ecológica. Foram coletados dados pré-existentes antes e após o acidente e realizadas campanhas amostrais dois anos após o início da implantação do projeto de restauração. A comunidade de macroinvertebrados foi avaliada pela aplicação de índices ecológicos estruturais e funcionais alimentares e os resultados analisados por meio de ferramentas de estatística uni e multivariada. A análise da literatura mostrou que a aplicação de índices ecológicos tradicionais, tais como riqueza e diversidade, podem não ser sensíveis o suficiente para indicar impactos relacionados à sedimentação e implementação de projetos de restauração ecológica. Sendo, assim, necessária a utilização de índices que considerem a composição da comunidade, a sensibilidade dos organismos e a utilização de grupos funcionais alimentares e suas relações. Antes do rompimento da barragem a comunidade de macroinvertebrados já apresentava-se empobrecida pelo assoreamento do trecho represado e do canal fluvial. O rompimento da estrutura implicou na perda de importantes grupos e na mudança da composição da comunidade, além da perda de grupos funcionais alimentares, com consequente perda de funções ambientais. Após a implementação do projeto de restauração houve o aparecimento de 20 famílias, no entanto, os índices ecológicos tradicionais não foram capazes de identificar mudanças na comunidade. Métricas de composição e de grupos alimentares apontaram para um processo de recuperação da área. As características do sedimento tiveram um alto poder explicativo da comunidade, mostrando que a recuperação do habitat bentônico é um dos fatores que leva à uma melhor resposta da comunidade, mesmo esse não tendo sido o foco da aplicação do projeto de restauração avaliado. O relativo curto período transcorrido após a implementação do projeto já foi suficiente para indicar melhorias na qualidade ambiental. Tais resultados contrapõe a maioria dos estudos verificados na revisão da literatura. No entanto destaca-se que os mesmos foram conduzidos principalmente em ambientes temperados, indicando que em ambientes tropicais a dinâmica de recuperação é diferente. Assim aponta-se a necessidade da intensificação da implantação de projetos e monitoramento dos mesmos para a criação de um arcabouço teórico para auxiliar gestores e projetistas na sua elaboração. / Anthropic alterations in aquatic ecosystems demand the implementation of recuperation actions, highlighting ecological restoration projects. The monitoring is an important step to these projects, and the macroinvertebrates application as bioindicators is an important tool, because they are advantageous in comparison to another assessment methods. Thus, the goal was verify the effects of silting, and dam rupture in macroinvertebrate community, in a tropical stream, and assess the answer to an ecological restoration project implementation. The research was conducted in the Campininha stream, that was impacted by anthropic alterations, featured a dam rupture and after all this disturbances was implemented an ecological restoration project. A literature review was conducted to verification of the applicability of macroinvertebrates as bioindicators of silting and in ecological restoration projects assessment. Data was collected before and after the dam rupture, and samplings were done two years after the project implementation began. The macroinvertebrates community was assessed by application of structural and functional feeding indexes and the results analyzed by univariate and multivariate statistic. The literature review showed that the traditional indexes application may be not sensible to indicate impacts related to silting and ecological restoration projects implementation, and it is necessary the utilization of indexes that consider the community composition, organisms sensibility and functional feeding groups and your relations. Before the dam rupture, the macroinvertebrate community was already poor by the silting of the lake and fluvial channel. The dam rupture leaded to the loss of important groups and in the change of the macroinvertebrate community composition, also loss of functional feeding groups and consequently environmental functions. After the ecological restoration project implementation were found another 20 families, however, the traditional indexes were not sensible to indicate changes in macroinvertebrates community. Composition and functional feeding groups indexes showed the stream recuperation process. The sediment characteristics had a community high explanative power showing that the benthic habitat recovery is a factor that guide to a better community answer, even this was not the goal of the restoration project application. The relative short time after the project implementation was enough to point a environmental quality recovery, in contrast with the literature review. However the most studies analyzed was conducted in temperate environments, showing that in tropical environments the recovery dynamics is different. Thus, is necessary a intensification of restoration projects implementation and monitoring to a creation of data bases to guide managers and professionals responsible by the projects elaboration in decision make.

As áreas de várzea estão entre os ecossistemas mais ameaçados, porém no Brasil essa situação agrava-se devido à falta de uma abordagem ecológica robusta na Lei de Proteção da Vegetação Nativa, o que torna necessário a atuação do poder público municipal para salvaguardar esses sistemas. A presente pesquisa empregou uma abordagem ecológica aplicada (limnologia, macroinvertebrados, macrófitas aquáticas) para avaliar a relação do rio Sorocaba com suas várzeas no município de Sorocaba, o uso e ocupação da terra e a sua influência sobre às variáveis limnológicas, além das demandas dos serviços ambientais fornecidos pelas várzeas ao município. Duas amostragens foram realizadas durante o ano de 2017, sendo uma no período de cheia (fevereiro) e outra na estiagem (junho). Métodos padronizados foram empregados para o desenvolvimento do presente trabalho. Evidenciou-se que a poluição orgânica e o predomino de áreas antropizadas são os principais fatores responsáveis pela alteração das variáveis limnológicas analisadas. Alguns serviços ambientais (i.e. provisão de água, controle do fluxo, regulação dos processos erosivos, regulação de nutrientes, ciclagem da água, pesca voltada ao lazer e valor intrínseco da biodiversidade) prestados pelos ecossistemas de várzea do Município de Sorocaba apresentam um balanço negativo (i.e. demanda superior à oferta). As espécies de macrófitas e famílias de macroinvertebrados encontradas são espécies indicadoras de poluição orgânica. Por fim, destaca-se a contribuição da ação estratégica e o papel da gestão municipal para o manejo dos ecossistemas de várzea. / The wetlands are among the most threatened ecosystems, although in the Brazil that situation is worse because of an ecological approach lack in the Law of Native Vegetation Protection, what makes necessary the public power action to safeguard those systems. The present research employed an applied ecological approach (limnology, macroinvertebrates, aquatic macrophytes) for Sorocaba River and its wetlands assessment in Sorocaba-SP municipality, the land cover and its influence on limnological variables, as well as the environmental services demand supplied by the municipality wetlands. Two samples were performed during 2017, one during the rainy (February) season and other on the dry season (June). Patronized methods were employed in the present research. The organic pollution and the anthropic areas predominance are the mainly factors responsible for limnological variables alteration. Some environmental services (i.e. water provision, water flow control, erosive process control, nutrient control, water cycling, recreation fishing and biodiversity intrinsic value) provided by the studied wetlands showed a negative balance (i.e. demand superior to the provision capacity). The macrophyte species and macroinvertebrate families found are organic pollution indicators. Finally, stand out the strategic action contribution and the municipality governance role for wetlands ecosystem management.

O presente trabalho teve como objetivo testar se os fatores ambientais cobertura vegetal, estrutura ambiental, vazão e características físicas e químicas da água (pH, oxigênio dissolvido, temperatura da água e condutividade) podem predizer a abundância, a diversidade e a composição de Chironomidae em riachos. As coletas foram realizadas em riachos localizados nos núcleos Santa Virgínia e Cunha-Indaiá, Parque Estadual Serra do Mar, Estado de São Paulo, e suas adjacências, nos meses de outubro de 2006 e outubro e novembro de 2007. Em cada riacho a fauna associada a 25 rochas (com aproximadamente 20 centímetros de diâmetro) foi coletada. Foram coletados 3758 indivíduos distribuídos em 71 táxons. A riqueza estimada para a região, através do método de Jacknife 2, foi de 105 táxons. Os coeficientes parciais estimados a partir da regressão linear múltipla demonstraram que a cobertura vegetal teve influência significativa sobre a abundância e o oxigênio dissolvido sobre a riqueza. Nenhum fator ambiental foi preditivo da composição faunística. Riachos que apresentaram as maiores vazões e os menores escores do RCE apresentaram menores valores para a diversidade beta / This study aimed to test the effects of vegetation cover, environmental structure, discharge and physical and chemical characteristics (pH, dissolved oxygen, water temperature and conductivity) on the abundance, diversity and composition of Chironomidae fauna in streams. The sampling was done in streams from Parque Estadual da Serra do Mar (Núcleos Santa Virgínia e Cunha-Indaiá) and neighborhoods, in October 2006, and October and November 2007. In each stream, the individuals of Chironomidae associated to 25 individual stones were sampled. The total of 3758 individuals in 71 taxa was collected. The richness, estimated by Jacknife 2, to the streams of the studied region was 105 taxa. The partial coefficients estimated by multiple linear regression showed that canopy cover was related to the abundance and the dissolved oxygen to the richness. No environmental factor was predictive of faunistic composition. Larger size and lower RCE scores streams presented lower beta diversity.

Understanding the composition of lotic communities and the landscape processes and habitat characteristics that shape them is one of the main challenges confronting stream ecologists. In order to better understand the linkages among landscape processes, stream habitat, and biological communities and to understand how accurately our measurements represent important factors influencing biological communities, it is important to test explicit hypotheses regarding these linkages. Increasing our understanding of aquatic communities in a hierarchical context and recognizing how well our measurements represent factors structuring aquatic communities will help managers better evaluate the influence of land management practices on aquatic ecosystems, direct conservation strategies, and lead to better assessments of ecological condition. In Chapter 2, we used spatial data, field-based habitat measurements, and macroinvertebrate community data to 1) examine the influence of landscape processes on two factors of stream habitat; maximum stream temperatures and fine sediment, and to 2) examine how well these landscape and habitat characteristics represent factors influencing gradients in macroinvertebrate community structure. The results of this study showed that spatially derived measurements may be effectively used to test hypotheses regarding landscape influences on stream habitat and that spatial data, used in conjunction with field measurements can provide important information regarding factors influencing gradients in biological communities. In addition, spatially derived measurements may provide the same or additional information regarding influences on community structure as field-based measurements, which suggests that further research should be done to assess how well our field measurements represent factors that are important in shaping stream communities. The objective of Chapter 3 was to compare how well single field measurements and a combination of indicator variables hypothesized to be components of a single ecological processes or concept, known as a latent variable, represent thermal stress and fine sediment influences on macroinvertebrate communities. Results from this study showed that both single and latent variables explained relatively the same amount of variation in macroinvertebrate community structure. This suggests that while latent variables may have a potential to better refine how we represent ecological factors, a better basis for defining a priori hypotheses is needed before these variables can provide any additional information compared to single habitat measurements.

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Intensive Landwirtschaft ist eine der allgegenwärtigsten anthropogenen Bedrohungen für aquatische Ökosysteme und beeinflusst sowohl die abiotischen als auch die biotischen Eigenschaften von Fließgewässerökosystemen. Diese resultieren aus der Vielzahl von Störungen, die mit Landnutzungsänderungen verbunden sind, wie z.B. Uferkahlschlag und dem damit verbundenen Verlust von allochthonem organischem Material und Beschattung, Nährstoff- und Pestizidkontamination, Feinsedimenteintrag durch Erosion und Oberflächenabfluss, sowie beeinträchtigte Hydromorphologie und damit verbundenem Verlust von vielfältigen Lebensräumen. Umfangreiche Literatur zu den Auswirkungen von Landwirtschaft auf einzelne Ökosystemkomponenten wie Makroinvertebraten, Biofilm oder Fischfauna existiert bereits, wobei der Schwerpunkt hier zumeist auf strukturellen Ansätzen oder einzelnen Ökosystemprozessen liegt. Allerdings haben nur wenige Studien umfassende Auswertungen angestellt, wie intensive Landwirtschaft die Funktion des gesamten aquatischen Ökosystems und die Wechselwirkungen zwischen den Ökosystemkomponenten beeinflusst. Um komplexe Effektmuster landwirtschaftlicher Stressoren auf Fließgewässerstruktur- und funktion sowie mechanistische Wirkzusammenhänge zwischen trophischen Ebenen besser zu verstehen wurden im Rahmen der vorliegenden Arbeit zwei Bäche die innerhalb landwirtschaftlicher Einzugsgebiete liegen und zwei bewaldete Referenzbäche im Harz, Sachsen-Anhalt, hinsichtlich ihrer physiko-chemischen Eigenschaften, der Menge und der Einträge von benthischem organischem Material, der Primärproduktion und organischen Kohlenstoffkreisläufen sowie der Sekundärproduktion von Makroinvertebraten und Fischen über einen Zeitraum von 12-17 Monate miteinander verglichen. Intensive Landwirtschaft hatte starke Auswirkungen auf die physiko-chemischen Eigenschaften der untersuchten Bachoberläufe. Wir ermittelten spezifische Leitfähigkeitswerte in landwirtschaftlich genutzten Bächen, welche die Konzentration gelöster Ionen in bewaldeten Referenzbächen um eine Größenordnung übertrafen. Die Konzentrationen von gelöstem anorganischem Stickstoff und löslichem reaktivem Phosphor waren in den landwirtschaftlichen Bächen im Durchschnitt viermal höher und der pH-Wert war im Durchschnitt eine Einheit niedriger als in den bewaldeten Bächen. Die Wassertemperatur war in landwirtschaftlich genutzten Bächen im Durchschnitt 3°C wärmer und zeigte höhere tageszeitliche Schwankungen. Der Eintrag von partikulärem organischem Material (POM) in die landwirtschaftlichen Bäche war ca. 30-mal niedriger als der Eintrag in die Referenzbäche, und die Menge an benthischem organischem Material (BOM) war in landwirtschaftlichen Bächen signifikant niedriger als in den Referenzbächen. Landwirtschaftliche Fließgewässer wiesen signifikant höhere Mengen an feinem benthischem organischem Material (FBOM) auf, hatten aber geringere Bestände an grobem benthischem organischem Material (CBOM) als die Referenzgewässer. Während in bewaldeten Fließgewässern die zeitliche Dynamik des BOM einem saisonalen Muster folgte, waren die Schwankungen in den landwirtschaftlichen Fließgewässern überwiegend stochastisch und durch anthropogene Aktivitäten, wie das Mähen der Uferrandstreifen, beeinflusst. Auch die Retention von POM war in landwirtschaftlich genutzten Bächen im Vergleich zu bewaldeten Bächen deutlich geringer, was auf eine geringere morphologische Komplexität und die größere hydrologische Variabilität, insbesondere auf die Abflussganglinien, zurückzuführen ist. Innerhalb des Experimentes zur Aufnahme von gelöstem organischem Kohlenstoff (DOC) war die Biofilmqualität in den landwirtschaftlichen Bächen ebenfalls höher. Interessanterweise zeigte jedoch der landwirtschaftliche Bach Hassel einen höheren Grad an Heterotrophie als der bewaldete Bach Wormsgraben. Da die biofilmspezifische DOC-Aufnahme im bewaldeten Bach nur 4 % der Gesamtaufnahme betrug, kann davon ausgegangen werden, dass die mikrobiell vermittelte Verarbeitung von Nährstoffen in der hyporheischen Zone den größten Anteil an der DOC-Aufnahme ausmachte. Vermutlich begünstigte die höhere Verweildauer und der bessere Austausch zwischen Oberflächenwasser und der hyporheischen Zone im bewaldeten Bach Wormsgraben die heterotrophe Nährstoffumsetzung im interstitiellen Porenraum. Die Bewertung der Makroinvertebraten-Gemeinschaft ergab, dass der Artenreichtum in landwirtschaftlichen Bächen im Vergleich zu bewaldeten Bächen um die Hälfte reduziert war. Die Biomasse, Dichte und Sekundärproduktion der Makroinvertebraten (Makroinvertebratensekundärproduktion, MSP) nahm jedoch entlang eines Gradienten der Ressourcenqualität und -quantität zu, mit höchster Produktivität im landwirtschaftlichen Bach Sauerbach, gefolgt vom landwirtschaftlichen Bach Getel und den bewaldeten Bächen Ochsenbach und Wormsgraben. Der Anstieg der MSP war hauptsächlich auf Zunahmen innerhalb der funktionellen Ernährungsgruppen der Sedimentfresser und Weidegänger zurückzuführen. Höhere MSP, Biomasse und Dichte korrelierten positiv mit niedrigeren N:P- und C:P-Verhältnissen des Biofilms und der Ressourcenmenge (höhere Biofilm-Zuwachsrate und Menge an krautiger Vegetation, Chlorophyll a-, TDN- (Summe an gelöstem Stickstoff), SRP- (gelöster reaktiver Phosphor) und POC- (Partikulärer organischer Kohlenstoff) Konzentrationen von Biofilm und Seston). Hohe Interaktionsstärken zwischen Zerkleinerern und grobpartikulärem organischem Material (CPOM) in landwirtschaftlichen Bächen deuteten auf eine Ressourcenlimitierung durch allochthones organisches Material hin. Da die Interaktionsstärken zwischen Weidegängern und Biofilm sowie zwischen feinpartikulärem organischem Material (FPOM) und Sammlern in landwirtschaftlichen Bächen deutlich geringer waren als in bewaldeten Bächen ist anzunehmen, dass die Gruppe der Zerkleinerer diese Limitation durch hohe funktionelle Plastizität und damit alternative Ressourcennutzung ausgleichen konnten. Die Analyse der Fischsekundärproduktion und Interaktionsstärken zwischen Fischen und ihrer Makroinvertebraten-Beute konnte zusätzlich zeigen, dass die landwirtschaftliche Flächennutzung zu einer starken Verschiebung des Fischartenspektrums führen und die Top-down Kontrolle der MSP durch Fische dadurch deutlich zurückgehen kann. Diese Ergebnisse zeigen, dass der Verlust der Ufervegetation und die übermäßige Nährstoffbelastung ökologische Nischen homogenisieren und hochproduktive Generalisten mit hoher Nahrungsplastizität begünstigten, die flexibel zwischen ubiquitären und stochastisch verfügbaren Nahrungsressourcen wechseln können. Insgesamt konnten wir mit dieser Studie darlegen, durch welche Mechanismen aus hoch-diversen, nährstoffbegrenzten, bewaldeten Bachoberläufen, die stark von terrestrischen Laubeinträgen abhängig sind, durch landwirtschaftliche Flächennutzung homogene, nährstoffbelastete und taxonomisch vereinfachte Bäche, mit einem hohen Maß an Autochthonie, werden können. Die gleichzeitige Analyse struktureller und funktioneller Indikatoren zeigte, dass die Landwirtschaft strukturelle Messgrößen wie den Artenreichtum beeinflusst, ohne dass es zu größeren Veränderungen in der Funktion kommen muss (ähnliche MSP im landwirtschaftlich genutzten Bach Getel im Vergleich zu bewaldeten Referenzbächen), und dass die Variabilität in der Funktion (Retention von organischem Material, Laubabbau) nicht automatisch die Informationen widerspiegelt, die die üblicherweise bewerteten chemischen oder biologischen strukturellen Messgrößen liefern. Die Ergebnisse dieser Arbeit zeigen deutlich, dass eine Kombination mehrerer struktureller und funktioneller Indikatoren entlang der Nahrungsnetzhierarchie erforderlich ist, um mechanistisch zu verstehen, wie intensive Landwirtschaft die Ökosysteme von Fließgewässern beeinflusst. So erlaubten z.B. nur die Informationen über die Qualität und Quantität der Primärproduktion, in Kombination mit strukturellen und funktionellen Informationen über die Makroinvertebratengemeinschaft, ein mechanistisches Verständnis darüber, wie landwirtschaftliche Stressoren die Produktivität mehrerer trophischer Ebenen des Nahrungsnetzes von Fließgewässern beeinflussen und damit auch wie diese Auswirkungen gemildert werden könnten. Diese Ergebnisse verdeutlichen die dringende Notwendigkeit, effektive und breite Gewässerrandstreifen zu erhalten oder zu errichten, um Sedimenteinträge durch Erosion- und Oberflächenabfluss zu verringern, sowie Einträge von Nährstoffen und Pestiziden zurückzuhalten, um eine verbesserte Vereinbarkeit von Landwirtschaft und Naturschutz zu erwirken. Diese Maßnahmen hätten eine positive Auswirkung auf Lebensraum- und Ressourcenvielfalt und schützen damit sowohl terrestrische als auch aquatische Ökosysteme und die damit verbundenen essentiellen Ökosystemdienstleistungen dieser Systeme.:Table of contents Table of contents 1 List of tables 5 List of figures 6 List of abbreviations and acronyms 8 Abstract 11 Zusammenfassung 14 1. General introduction 18 1.1 Forested headwater streams - the significance of aquatic-terrestrial coupling 18 1.2 Effects of agricultural land use on forested headwater streams 22 1.3 Integrating measures of ecosystem functioning in stream ecosystem assessment 24 1.4 Aims and objectives 28 1.5 Thesis outline 30 2. Chapter I: Agricultural land use alters temporal dynamics and the composition of organic matter in temperate headwater streams 31 2.1 Introduction 31 2.2 Methods 33 2.2.1 Study sites 33 2.2.2 Sampling of POM inputs and standing crops 37 2.2.3 Organic matter sample processing 37 2.2.4 Physical and chemical stream characteristics 38 2.2.5 C spiraling metrics 39 2.2.6 Litter decomposition 39 2.2.7 Data analyses 41 2.3 Results 43 2.3.1 Organic matter inputs 43 2.3.2 Benthic organic matter 46 2.3.3 Organic matter retention 52 2.3.4 Environmental drivers of BOM dynamics 55 2.3.5 Leaf litter decomposition 55 2.4 Discussion 57 2.4.1 Effects of agricultural land use on POM inputs and BOM dynamics 57 2.4.2 Organic matter retention 60 2.4.3 Organic matter processing 61 2.4.4 Ecosystem-level implications of altered OM dynamics 62 2.5 Conclusions 63 3. Chapter II: Biofilm-specific uptake does not explain differences in whole-stream DOC tracer uptake between a forest and an agricultural stream 64 3.1 Introduction 64 3.2 Methods 66 3.2.1 Site description 66 3.2.2 Stable isotope tDOC labeling 68 3.2.3 Experimental design 68 3.2.4 Sampling and analysis 69 3.2.5 Statistical analysis 72 3.3 Results 74 3.3.1 Stream characteristics 74 3.3.2 DOC uptake 75 3.3.3 Benthic biofilm attributes 79 3.4 Discussion 84 3.4.1 Mechanisms linking hydromorphology, benthic-biofilm uptake and whole-stream uptake 84 3.4.2 Comparison of whole-stream tDOC uptake with other studies 86 3.4.3 Benthic biofilm attributes 87 3.5 Conclusions 89 4. Chapter III: Resource supply and organismal dominance are associated with high secondary production in temperate agricultural streams 90 4.1 Introduction 90 4.2 Methods 93 4.2.1 Study sites 93 4.2.2 Macroinvertebrate sampling and processing 97 4.2.3 Macroinvertebrate secondary production (MSP) 97 4.2.4 Environmental characteristics of streams 98 4.2.5 Benthic organic matter 99 4.2.6 Biofilm biomass accrual and stoichiometry 99 4.2.7 Fish biomass 100 4.2.8 Ingestion rates and interaction strength 100 4.2.9 Data analyses 101 4.3 Results 104 4.3.1 Environmental characteristics of the study streams 104 4.3.2 Structural descriptors of the macroinvertebrate community 106 4.3.3 Macroinvertebrate secondary production (MSP) 107 4.3.4 Environmental drivers of MSP and biomass 109 4.3.5 Relationships between MSP and species richness and evenness 111 4.3.6 Consumer-resource interactions 111 4.4 Discussion 113 4.4.1 Environmental drivers of MSP and biomass 113 4.4.2 Biological mechanisms associated with MSP 116 4.4.3 Top-down vs. bottom-up control 118 4.5 Conclusion 120 5. General discussion 121 5.1 Environmental conditions 121 5.2 Allochthonous organic matter dynamics 122 5.3 Organic matter processing 124 5.4 Primary production 124 5.5 Drivers of macroinvertebrate secondary production 127 5.6 Fish community 128 6. General conclusion 132 7. Implications for the assessment of running water ecosystems 134 8. Outlook 137 References 139 Appendix 182 Chapter I 182 Chapter II 189 Supplemental methods 189 Chapter III 198 Acknowledgements 212 Curriculum vitae 215 List of publications 217 Publication output during thesis period 217 Further publications 218 Eidesstattliche Erklärung 219 / Intensive crop agriculture is one of the most ubiquitous and pervasive anthropogenic threats to aquatic ecosystems. Important agriculture-related pressures include riparian clearcutting and the associated loss of allochthonous organic matter inputs and shading, nutrient and pesticide contamination, fine sediment inputs due to erosion and run-off, increased surface runoff, flashier hydrographs as well as degraded geomorphology and habitat diversity. The multitude of stressors deriving from agricultural land use often produces concomitant effects on several groups of biological organism and associated functions. While effects on single ecosystem components such as macroinvertebrates, biofilm or fish fauna with primary focus on structural components or single ecosystem processes are well described, only few studies have compiled comprehensive data sets on how agriculture affects the functioning of the entire aquatic ecosystem and interactions among ecosystem components. Thus, this thesis aimed to fill this knowledge gap by comparing agricultural and forested reference streams regarding their physicochemical characteristics, organic matter standing stocks and inputs, primary production, organic carbon spiraling, DOC uptake rates as well as secondary production of macroinvertebrates and fish for a period of 12-17 months. Intensive agricultural land use had strong effects on the physico-chemistry of the studied headwater streams of the main study (two agricultural streams vs. two forested streams in the Harz mountains, Saxony-Anhalt). We ascertained specific conductivity values in agricultural streams that exceeded the ones measured in forested streams by an order of magnitude. Concentrations of dissolved inorganic nitrogen and soluble reactive phosphorus were on average four times higher and pH was on average one unit lower in agricultural streams than in forested streams. Water temperature was on average 3°C higher in agricultural streams and showed higher diurnal variations. Particulate organic matter (POM) inputs to forested streams were approx. 30-times higher than inputs into agricultural streams, and mean standing crops of total benthic organic matter (BOM) were significantly lower in agricultural streams than in forested streams. Agricultural streams had significantly higher standing crops of fine benthic organic matter (FBOM), but less coarse benthic organic matter (CBOM) than forested streams. While in forested streams temporal dynamics of organic matter standing stocks followed a seasonal pattern, variations were predominantly stochastic and influenced by anthropogenic activities such as stream margin mowing in agricultural streams. Also, the retention of POM was distinctly lower in agricultural compared to forested streams due to lower in-stream complexity and flashier hydrographs in agricultural streams indicating that agricultural streams are less efficient to retain organic matter, facilitating the loss of carbon to downstream sections of streams. Within the main study streams, biofilm accrual rates and chlorophyll a content were six and eight times higher, respectively, and biofilm N:P and C:P ratios were three times lower in agricultural than forested streams. In the dissolved organic carbon-uptake experiment (one agricultural stream vs. one forested stream), biofilm quality was similarly higher in the agricultural stream Hassel. Against expectations, the Hassel showed a higher level of heterotrophy than the forested stream Wormsgraben. However, the total and biofilm associated uptake of labeled leaf-leachate dissolved organic carbon (DOC) in the Hassel was six and two times higher than in the forested Wormsgraben, respectively. As the biofilm-specific uptake in the forested stream amounted to only 4% of the whole stream uptake, it seems that microbial-mediated processing of nutrients in the hyporheic zone is responsible for the largest proportion of DOC uptake. Presumably, the higher transient storage and the heterotrophic community resident in the interstitial pore space of the forested stream has a higher demand for labile DOC and hence, retained distinctly more DOC than in the agricultural stream, highlighting the importance of functional hyporheic zones for carbon spiraling. The macroinvertebrate community assessment revealed that species richness was reduced by half in agricultural compared to forested streams. Macroinvertebrate biomass, density, and secondary production (MSP), however, increased along a gradient of resource quality and quantity with highest productivity in the agricultural stream Sauerbach, followed by the agricultural stream Getel, and the forested streams Ochsenbach and Wormsgraben. The increase in MSP was mainly due to higher production within the functional feeding groups (FFGs) of gatherer/collectors and grazers. Higher MSP, biomass, and density correlated positively with lower biofilm N:P and C:P ratios and resource quantity (higher biofilm accrual rate and standing crops of riparian herbaceous vegetation, biofilm and seston chlorophyll a, total dissolved nitrogen, soluble reactive phosphorus, and particulate organic carbon concentrations). High interaction strengths between shredders and coarse particulate organic carbon (CPOM) in agricultural streams indicated a resource limitation of allochthonous organic matter, while this seemed to have no effect on macroinvertebrate productivity as interaction strengths between grazers and biofilm as well as between fine particulate organic carbon (FPOM) and gatherers were distinctly lower in agricultural than in forested streams. These findings show that the loss of riparian canopy and excess nutrient conditions homogenized ecological niches and favored highly productive non-insect generalist species with high feeding plasticity to switch flexibly between ubiquitous and stochastically available food resources. In addition, analyses of fish secondary production and interaction strengths between fish and their macroinvertebrate prey demonstrated that agriculture may cause a major shift in fish species community composition, resulting in a decline in fish top-down control on MSP. Overall, the presented results demonstrate that agriculture induces a shift from nutrient-limited forested headwaters dependent on detrital pathways and closely coupled to riparian subsidies with highly diverse macroinvertebrate communities to homogenous, nutrient contaminated and taxonomically simplified streams with high levels of autochthony. The simultaneous analysis of structural and functional indicators showed that agriculture affects structural measures of community composition such as species richness without major changes in process rates (similar level of macroinvertebrate secondary production in the agricultural stream Getel compared to forested streams) and that variability in function (organic matter retention, decomposition) does not automatically reflect the information provided by commonly assessed structural measures of communities. The results of this thesis clearly showed that a combination of multiple structural and functional indicators along the food web hierarchy is required to mechanistically understand how intensive agricultural land use affects stream ecosystems. For example, only the information on quality and quantity of primary production combined with structural and functional information on the macroinvertebrate community allowed to mechanistically understand how agricultural stressors affect the productivity of multiple trophic levels of the stream food web and thus, how these effects can be mitigated. Given that such mitigation measures would largely address excessive nutrient and sediment inputs, the loss of habitat heterogeneity and natural resource dynamics, the high relevance of riparian buffer zones known for their effective the retention of nutrients, erosional run-off and the provision of resource quantity and quality is evident. Consequently, there is an urgent need to preserve or restore effective riparian zones along stream networks aiding both terrestrial and aquatic ecosystems while integrating protection measures for other anthropogenic pressures such as habitat degradation and climate change.:Table of contents Table of contents 1 List of tables 5 List of figures 6 List of abbreviations and acronyms 8 Abstract 11 Zusammenfassung 14 1. General introduction 18 1.1 Forested headwater streams - the significance of aquatic-terrestrial coupling 18 1.2 Effects of agricultural land use on forested headwater streams 22 1.3 Integrating measures of ecosystem functioning in stream ecosystem assessment 24 1.4 Aims and objectives 28 1.5 Thesis outline 30 2. Chapter I: Agricultural land use alters temporal dynamics and the composition of organic matter in temperate headwater streams 31 2.1 Introduction 31 2.2 Methods 33 2.2.1 Study sites 33 2.2.2 Sampling of POM inputs and standing crops 37 2.2.3 Organic matter sample processing 37 2.2.4 Physical and chemical stream characteristics 38 2.2.5 C spiraling metrics 39 2.2.6 Litter decomposition 39 2.2.7 Data analyses 41 2.3 Results 43 2.3.1 Organic matter inputs 43 2.3.2 Benthic organic matter 46 2.3.3 Organic matter retention 52 2.3.4 Environmental drivers of BOM dynamics 55 2.3.5 Leaf litter decomposition 55 2.4 Discussion 57 2.4.1 Effects of agricultural land use on POM inputs and BOM dynamics 57 2.4.2 Organic matter retention 60 2.4.3 Organic matter processing 61 2.4.4 Ecosystem-level implications of altered OM dynamics 62 2.5 Conclusions 63 3. Chapter II: Biofilm-specific uptake does not explain differences in whole-stream DOC tracer uptake between a forest and an agricultural stream 64 3.1 Introduction 64 3.2 Methods 66 3.2.1 Site description 66 3.2.2 Stable isotope tDOC labeling 68 3.2.3 Experimental design 68 3.2.4 Sampling and analysis 69 3.2.5 Statistical analysis 72 3.3 Results 74 3.3.1 Stream characteristics 74 3.3.2 DOC uptake 75 3.3.3 Benthic biofilm attributes 79 3.4 Discussion 84 3.4.1 Mechanisms linking hydromorphology, benthic-biofilm uptake and whole-stream uptake 84 3.4.2 Comparison of whole-stream tDOC uptake with other studies 86 3.4.3 Benthic biofilm attributes 87 3.5 Conclusions 89 4. Chapter III: Resource supply and organismal dominance are associated with high secondary production in temperate agricultural streams 90 4.1 Introduction 90 4.2 Methods 93 4.2.1 Study sites 93 4.2.2 Macroinvertebrate sampling and processing 97 4.2.3 Macroinvertebrate secondary production (MSP) 97 4.2.4 Environmental characteristics of streams 98 4.2.5 Benthic organic matter 99 4.2.6 Biofilm biomass accrual and stoichiometry 99 4.2.7 Fish biomass 100 4.2.8 Ingestion rates and interaction strength 100 4.2.9 Data analyses 101 4.3 Results 104 4.3.1 Environmental characteristics of the study streams 104 4.3.2 Structural descriptors of the macroinvertebrate community 106 4.3.3 Macroinvertebrate secondary production (MSP) 107 4.3.4 Environmental drivers of MSP and biomass 109 4.3.5 Relationships between MSP and species richness and evenness 111 4.3.6 Consumer-resource interactions 111 4.4 Discussion 113 4.4.1 Environmental drivers of MSP and biomass 113 4.4.2 Biological mechanisms associated with MSP 116 4.4.3 Top-down vs. bottom-up control 118 4.5 Conclusion 120 5. General discussion 121 5.1 Environmental conditions 121 5.2 Allochthonous organic matter dynamics 122 5.3 Organic matter processing 124 5.4 Primary production 124 5.5 Drivers of macroinvertebrate secondary production 127 5.6 Fish community 128 6. General conclusion 132 7. Implications for the assessment of running water ecosystems 134 8. Outlook 137 References 139 Appendix 182 Chapter I 182 Chapter II 189 Supplemental methods 189 Chapter III 198 Acknowledgements 212 Curriculum vitae 215 List of publications 217 Publication output during thesis period 217 Further publications 218 Eidesstattliche Erklärung 219

Human disruption of climate, habitat, and ignition has altered the behavior of wildland fire at local to continental scales. In many regions, novel fire regimes are emerging that threaten to exceed the capacity for local management to protect human wellbeing and ecosystem function. Simultaneous changes in climate, species composition, and fire management have resulted in extreme fire behavior in many regions. For the Western United States, the emerging novel fire regime consists of more frequent, severe, and intense wildfires, with annual area burned by wildfire having doubled and high-severity wildfire area having increased 8-fold since the 1980s. The impacts of these increasing stresses in the Great Basin is especially pressing when combined with the many years of historically poor resource management. Here we complete a literature review of changing wildfire regimes globally (chapter 1) and a study of how the abiotic and biotic aspects of aquatic ecosystems stabilize after a megafire in the western United States (chapter 2).