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The lack of proper wastewater treatment inhibits the social and economic development in many communities. The South African town Wakkerstroom is an example where wastewater is first treated before it is released. Due to the lack of technical expertise and funding to manage the sewage disposal system, a large part of the wastewater goes directly, without any treatment, into a stream feeding the Wakkerstroom wetland. The wetland purifies the wastewater and provides clean water downstream, thus is indispensable for its detoxification capacity. One relatively cheap method to determine the absorption capacity of a wetland with respect to nitrogen loading is to investigate the nitrogen uptake by the wetland vegetation. In this study, the nitrogen uptake of the vegetation in the Wakkerstroom wetland during the growing seasons between the years 2000-2018 was investigated by using harvested biomass and its nitrogen content as a proxy. The interannual variability of Net Primary Production (NPP) was calculated using a Light Use Efficiency (LUE) model for the period 2000-2018. The NPP derived with LUE-modelling was compared to NPP based on an end-of season harvest of biomass in March 2019. The nitrogen content and carbon and nitrogen (C:N) ratio were determined in the harvested biomass by carbon and nitrogen content analysis. The annual nitrogen uptake of the growing seasons between the years 2000-2018 was subsequently determined by multiplying the calculated NPP by the fraction of nitrogen found in the harvested material. The NPPtot based on harvested biomass (NPPharvest) towards the end of the growing season 2018/2019 was estimated to be 2.01 kg‧m-2‧season-1. The NPPtot calculated from LUE modelling (NPPLUE) varied between 0.49-1.64 kg‧m-2 for the growing seasons between 2000-2018. NPPharvest was between 1.2-4 times higher compared to NPPLUE, probably due to overestimation of NPPharvest because of biomass sampling of more than one-year production, or underestimation of NPPLUE due to a low maximum radiation conversion efficiency factor, εmax. The community mean nitrogen (N) content found in the biomass harvested aboveground was 1.29 % for the Phragmites community and 1.00 % for the Typha community. The nitrogen uptake of the vegetation was estimated to vary between 6.10-20.5 g N∙m-2 per growing season between the years 2000-2018. / Bristen på adekvata reningstekniker för att behandla avloppsvatten hämmar den sociala och ekonomiska utvecklingen i många samhällen. Den sydafrikanska staden Wakkerstroom är ett exempel där avloppsvatten först renas innan det släpps ut. På grund av brisen på teknisk kompetens och finansiering att hantera reningsverket som avlägsnar avloppsvatten så läcker en stor del av det orenade avloppsvattnet ut i en våtmark i Wakkerstroom via en närliggande å. Våtmarken är av regional betydelse för sin reningskapacitet då den renar avloppsvattnet och förser användare nedströms med rent vatten. En viktig aspekt för att bestämma en våtmarks reningskapacitet med avseende på kväve (N) är att undersöka växternas kväveupptag i våtmarken. Kväveupptaget hos växterna i våtmarken i Wakkerstroom under växtsäsongerna mellan år 2000–2018 undersöktes genom att använda skördad biomassa och dess kväveinnehåll som proxy. Den årliga variabiliteten hos nettoprimärproduktionen (NPP) beräknades genom att använda en LUE (Light Use Efficiency)-modell för perioden 2000-2018. NPP framtaget med LUE-modellering jämfördes med NPP baserat på biomassa skördad i slutet av växtsäsongen i mars 2019. Kväveinnehållet och kol-kväve (C:N) kvoten bestämdes hos den skördade biomassan genom en kol- och kväveanalys. Det årliga kväveupptaget under växtsäsongerna mellan 2000–2018 togs därefter fram genom att multiplicera beräknad NPP med kvävefraktionen erhållen från den skördade biomassan. NPPtot framtaget med biomassa skördad i slutet av växtsäsongen 2018/2019 (NPPbiomassa) uppskattades vara 2,01 kg‧m-2‧säsong-1. NPPtot beräknat med LUE-modellering (NPPLUE) varierade mellan 0,49–1,64 kg‧m-2 under växtsäsongerna mellan år 2000–2018. NPPbiomassa var 1,2–4 gånger högre i jämförelse med NPPLUE, vilket troligtvis berodde på att NPPbiomassa överskattades på grund av att mer än en årsproduktion av biomassa skördades, eller för att NPPLUE underskattades på grund av ett för lågt värde på den maximala effektivitetsfaktorn εmax valdes. Medelvärdet för kväveinnehållet erhållen i biomassan skördad ovanför vattennivån var 1,29 % för Phragmites-samhället och 1,00 % för Typha-samhället. Kväveupptaget hos växterna varierade mellan 6,10–20,5 g N∙m-2 per växtsäsong mellan år 2000–2018.

Der Klimawandel bedroht Ökosysteme auf der ganzen Welt. Besonders der Anstieg in Länge, Intensität und Häufigkeit von Dürren kann bedeutenden Einfluss auf den globalen Kohlenstoffkreislauf haben. Die Frage, ob Pflanzen und Mikroorganismen anfällig gegenüber ökologischem Stress wie Dürren sind, wurde bereits in vielen Studien für verschiedene Ökosysteme und mit verschiedenen Ansätzen untersucht, aber Analysen von Dürreauswirkungen, die ober- und unterirdische Interaktionen von Pflanzen und Mikroorganismen mit einbeziehen, sind eher selten. Deshalb wird in der vorliegenden Studie die Frage erörtert, wie Trockenheit und/oder Hitze die Interaktionen von Pflanzen und Mikroorganismen in Bezug auf ihre Kohlenstoff-Verbindung beeinflussen. Dies dient zur Bestimmung der Stärke der Pflanze-Mikroorganismen-Kohlenstoff-Verbindung, wenn das Ökosystem an seine Grenzen gebracht wird. Der Fokus liegt deshalb auf durch Trockenstress und Hitze hervorgerufenen Veränderungen in der ober-unterirdischen Kohlenstoff-Dynamik in zwei vom Klimawandel bedrohten Ökosystemen. Es wurde untersucht, wie extreme Klimaereignisse, deren Häufigkeit in Zukunft weiter ansteigen soll, die Kohlenstoff-Verbindung zwischen Pflanzen und Mikroorganismen beeinflusst und wie mikrobielle Gemeinschaften unter diesen Umständen reagieren, um die Resistenz und Reaktionsmechanismen von Ökosystemen im zukünftigen Klimawandel besser vorhersagen zu können. In Kapitel 4 wurde ein Buchenwaldunterholz-Ökosystem untersucht. Buchenwaldmonolithen wurden einem extremen Klimaereignis (Trockenheit und/oder Hitze) ausgesetzt. Die Stärke der Pflanze-Mikroorganismen-Kohlenstoff-Verbindung und Veränderungen in der mikrobiellen Gemeinschaftsstruktur und -aktivität wurden mithilfe von stabilen 13C Isotopenmethoden und Ansätzen auf molekularer Basis, wie 16S rRNA- und Phospholipid-Analysen, bestimmt. In Kapitel 5 wurde ein kleines aquatisches Ökosystems untersucht. Zwei emerse aquatische Makrophyten, Phragmites australis und Typha latifolia, wurden in einem Mesokosmos-Experiment mit Sediment aus einem Soll einer einmonatigen Dürre ausgesetzt. Mithilfe einer 13CO2 Pulsmarkierung, sowie PLFA- und nicht-strukturbildenden Kohlenhydrat-Analysen wurde Kohlenstoff von den Blättern in die Wurzeln bis ins Sediment verfolgt, wo er teilweise in mikrobielle Phospholipide eingebaut wird. Diese Studie hat gezeigt, dass die zwei untersuchten Ökosysteme Trockenstress und Hitze relativ gut widerstehen können, zumindest kurzfristig, und dass das Kohlenstoff-Kontinuum, beziehungsweise die Verbindung zwischen ober- und unterirdischen Gemeinschaften, auch unter starkem Stress intakt bleibt. Zusammenfassend scheint es, dass Ökosysteme stark von einem funktionierenden Pflanze-Boden/Sediment-Mikroorganismen Kohlenstoff-Kontinuum abhängen und versuchen, es auch unter starkem Stress zu erhalten, was möglicherweise dazu beiträgt, dem Anstieg von extremen Dürreperioden aufgrund des Klimawandels besser zu widerstehen. / Climate change is threatening ecosystems around the world. Especially the increase in duration, intensity, and frequency of droughts can have a considerable impact on the global carbon cycle. The question whether plants and microbes are susceptible to environmental stress like drought has been assessed in many studies for different ecosystem types and by using numerous approaches, but research on drought effects that includes above- and belowground interactions is rather scarce. Therefore, the present study assesses the question of how drought and/or heat influence the interactions of plants and microbes, especially the carbon coupling, in order to determine the strength of plant-microbe carbon linkages when an ecosystem is pushed to its limits. The focus of this study thus lies on changes in aboveground-belowground carbon dynamics and the subsequent effects on the soil microbial community under drought and/or heat stress in two climate-threatened ecosystems. It was evaluated how extreme climate events, that are predicted to be more frequent in the near future, affect the carbon coupling between plants and microorganisms and how microbial communities respond under these circumstances, in order to be able to better predict ecosystem resistance and response mechanisms under future climate change. In chapter 4 a beech forest understory ecosystem was investigated. An extreme climate event (drought and/or heat) was imposed on beech forest monoliths and the strength of the plant-microbe carbon linkages and changes in the microbial community structure and activity were determined by using stable 13C isotope techniques and molecular-based approaches like 16S rRNA and microbial phospholipid-derived fatty acid (PLFA) analysis. In chapter 5 a small aquatic ecosystems was investigated. Two emergent aquatic macrophytes, Phragmites australis and Typha latifolia, were grown on kettle hole sediment and then exposed to a month-long summer drought in a mesocosm experiment. By conducting a 13CO2 pulse labeling as well as PLFA and non-structural carbohydrate analyses, the fate of carbon was traced from the plant leaves to the roots and into the sediment, where some of the recently assimilated carbon is incorporated into microbial PLFAs. Overall, this study showed that the two investigated ecosystems can endure environmental stress like heat and drought relatively well, at least in the short-term, and that the carbon continuum, or the linkage between above- and belowground communities, remained intact even under severe stress. In conclusion, it seems that ecosystems strongly depend on and try to maintain a functional plant-soil/sediment microorganism carbon continuum under drought, which might help to withstand the increase in extreme drought events under future climate change.

Au cours des dernières décennies, une grande variété de pesticides émergents, tels que le chlorantraniliprole (CAP), ont été introduits malgré le manque de connaissance approfondie de leur risque écotoxicologique. Les marais filtrants (TW) sont des technologies écologiques et durables qui ont montré un grand potentiel d’atténuation des polluants agricoles communs, tels que les pesticides dans le ruissellement. L’objectif de cette étude était d’optimiser l’utilisation du marais filtrant sous-surfacique à écoulement horizontal (HSSF) en déterminant: a) l'effet d’un amendement de biochar au substrat et b) la performance de trois espèces de macrophytes (Phragmites australis subsp. americanus, Scirpus cyperinus et Sporobolus michauxianus) dans l'abattement du CAP du ruissellement agricole. L'efficacité d'abattement a été calculée en utilisant la méthode du bilan de masse dans des mésocosmes HSSF matures alimentés avec un ruissellement agricole synthétique contenant du CAP pendant une période d'un mois. Les mésocosmes avec l’ajout de biochar se sont avérés très efficaces dans l’abattement du CAP (90 à 99%) et ils le sont restés tout au long de la période expérimentale. Cette efficacité est probablement due à la grande capacité d’adsorption du biochar, bien que ce mécanisme n’ait pas été directement mesuré. En revanche, l'abattement du CAP dans les mésocosmes plantés sans biochar était faible et limité et il n’y avait pas de différence entre les espèces, bien qu’elles aient eu des différences dans leur biomasse aérienne et leur taux d'évapotranspiration (ET). Cependant, les traitements plantés ont agi comme zone tampon, en atténuant la masse du CAP de l'influent et en la libérant lentement dans l'effluent. Le taux d'ET de Scirpus et Phragmites était plus élevé que celui de Sporobolus, ce qui s’est traduit par un meilleur effet tampon. Cette étude suggère que l'ajout de biochar au substrat HSSF TW est prometteur pour l'atténuation du CAP dans le ruissellement agricole, mais leur efficacité à long terme reste à être étudiée. Malgré tout, les TW devraient être utilisés comme un outil complémentaire, dans le cadre d'actions plus larges visant à réduire la pression des polluants sur les écosystèmes aquatiques. / Over the past decades, a wide variety of emergent pesticides, such as chlorantraniliprole (CAP), have been introduced despite the lack of in-depth knowledge of their ecotoxicological risk. Treatment wetlands (TWs) are environmentally friendly and sustainable technologies that have shown great potential to mitigate common agricultural pollutants, such as pesticides in runoff. The objective of this study was to optimize the use of the horizontal subsurface flow treatment wetlands (HSSF TWs) by determining a) the effect of biochar amendment to the substrate and b) the performance of three species of macrophytes (Phragmites australis subsp. americanus, Scirpus cyperinus and Sporobolus michauxianus) in CAP removal from agricultural runoff. The removal efficiency was calculated using the mass balance method in mature HSSF mesocosms fed with synthetic agricultural runoff containing CAP for a period of one month. Mesocosms with the addition of biochar were very effective in removing CAP (90-99%) and remained so throughout the experimental period. This efficiency is likely due to the high adsorption capacity of biochar, although this mechanism has not been directly measured. In contrast, CAP removal in mesocosms planted without biochar was low and limited and there was no difference between species, although there were differences in their above-ground biomass and their evapotranspiration (ET) rate. However, the planted mesocosms acted as buffer zones, reducing the CAP mass of the influent and slowly releasing it into the discharge. The ET rate of S. cyperinus and P. australis was higher than that of S. michauxianus, resulting in a better buffering effect. This study suggests that adding biochar to the HSSF TW substrate is promising for CAP attenuation in agricultural runoff, but their long-term effectiveness remains to be investigated. Nevertheless, TWs should be used as a complementary tool, as part of wider actions aimed at reducing the pressure of pollutants on aquatic ecosystems.

The climate on earth keeps getting warmer where heat waves, eutrophication, rising sea levels, extreme weather like flooding, droughts and wildfires are an expanding problem. The focus of this bachelor thesis is to determine the potential of mitigating eutrophication and while contributing to blue growth by harvesting and make use of reeds like Phragmites australis and Arundo donax. Reeds have the ability to quickly absorb nutrients from aquatic environments and there are opportunities to use them as a feedstock for producing biochar to be potentially used in areas such as soil improvement, fodder additive and carbon sequestration. Additionally, optimal biochar properties for the observed applications gets analysed. The thesis is based on a systematic literature review and an interview with Niclas Anvret at the non-profit organisation “Race for the Baltic”.  Results show that biochar produced according to parameters such as heating rate, biomass species and especially, different temperatures, results in varied characteristics that change the biochar's adsorption abilities, nutrient retention, alkalinity, stability, surface area and porosity volume. The different applications of biochar are, however, not easily determined. This is because of the fact that certain biochar properties, that are prominent in entirely different pyrolysis conditions, could both be beneficial for the same application. Additionally, the different attributes sometimes influence each other which gives rise to unclear patterns affecting use potential. To overcome these issues, more research is needed to clarify the correlations between attributes of the biochar and to determine which characteristics of biochar are best suited for each application.  In terms of how large-scale harvesting of reed could affect the ecosystem is also unclear, there is not enough research regarding the question to be able to draw clear conclusions. The reasoning behind this is that there are knowledge gaps, geographical differences, different unit measuring and methodology. The potential for biochar in the coal market is high and the demand in Sweden has risen over the past couple of years. There is also interest in using biochar as a soil amendment, to make use of nutrient content as well as applying organic matter to soils to potentially achieve long-term carbon sequestration. However, the production cost of biochar out of reed is relatively expensive, and it cannot compete with coal or other fertilisers/soil amendments on the market, with feedstock management usually being the most expensive part of production. Lastly, there is currently no harvesting method that can measure the amount of reed that needs to be harvested to be able to produce biochar on a large scale. / Klimatet på jorden blir allt varmare och värmeböljor, övergödning, stigande havsnivåer, extrema väder som översvämningar, torka och bränder är ett stigande problem. Syftet med denna kandidatuppsats är att undersöka potentialen att mildra eutrofiering och samtidigt bidra till blå tillväxt genom att skörda - och använda sig av vass som Phragmites australis och Arundo donax. Vass har en framträdande förmåga att absorbera näringsämnen. Det finns därför möjligheter att använda dem som råvara för att producera biokol som potentiellt kan användas i områden såsom jordförbättring, fodertillsatser och kolbindning. Utöver detta undersöks optimala egenskaper för biokol enligt de observerade applikationerna. Kandidatuppsatsen bygger på en systematisk litteraturstudie och en intervju med Niclas Anvret på den ideella organisationen ”Race for the Baltic”.  Resultaten indikerar att biokol, producerad i pyrolys enligt parametrar som uppvärmningshastighet, biomassa och i synnerhet olika temperaturer, resulterar i varierande egenskaper som förändrar biokolets absorptionsförmåga, bibehållande av näring, alkalinitet, stabilitet, ytarea och porositetsvolym. De olika tillämpningarna av biokol är emellertid svåra att avgöra på grund av vissa biokolegenskaper. Dessa egenskaper är framträdande under helt olika pyrolysförhållanden men kan samtidigt vara fördelaktiga för samma typ av applikation. Dessutom påverkar de olika attributen ibland varandra vilket ger upphov till komplexa trender som påverkar användningspotentialen. För att kunna dra tydliga slutsatser behövs mer forskning för att klargöra sambandet mellan biokolens attribut och för att bestämma vilken samling egenskaper hos biokol som passar bäst för varje applikation.  Hur storskalig skörd av vass kan påverka ekosystemet är fortfarande oklart. Det finns inte tillräckligt med forskning kring frågan för att kunna dra tydliga slutsatser. Detta beror på att det finns kunskapsluckor, geografiska skillnader, olika måttenheter och metoder för de studier som gjorts inom detta område. Potentialen för biokol på kolmarknaden är hög och efterfrågan i Sverige har ökat de senaste åren. Det finns också intresse för att använda biokol för jordförbättring, dels för att använda näringsinnehållet men också för att applicera biokol i jorden för att potentiellt uppnå långvarig kolbindning. Dock är produktionskostnaden för biokol gjort på vass mycket kostsam och kan därför inte konkurrera med fossilt kol eller andra gödselmedel jordförändringar på marknaden. Detta beror främst på råvaruhanteringen som är den dyraste delen av produktionen. Slutligen finns det för närvarande ingen skördemetod som kan mäta den mängd vass som behöver skördas för att kunna producera biokol i stor skala.

Les marais filtrants artificiels sont des écosystèmes recréés par l’homme dans le but d’optimiser l’épuration des eaux usées. Lors de la sélection d’espèces végétales pour la mise en place de ces marais filtrants, l’utilisation d’une polyculture ainsi que d’espèces indigènes non invasives est de plus en plus recommandée. Néanmoins, la plupart des marais filtrants existants sont des monocultures utilisant des plantes envahissantes, probablement à cause du manque d’évidences scientifiques sur les avantages de la diversité végétale et de la performance des espèces locales. Ainsi, les questions de recherche autour desquelles s’oriente ma thèse sont: Les polycultures présentent-elles un potentiel épuratoire aussi ou plus grand que les monocultures, et une espèce indigène est-elle aussi efficace et performante qu’une espèce exotique envahissante dans des marais filtrants ? Trois expériences ont été conduites afin de répondre à ces questions. J’ai d’abord testé l’influence de la richesse végétale sur l’élimination des polluants en deux dispositifs expérimentaux: 1) comparant deux espèces de plantes émergentes en monoculture ou combinées séquentiellement, et 2) évaluant la performance de quatre espèces flottantes plantées en monoculture par rapport à des associations de deux (avec toutes les combinaisons possibles) et de quatre espèces. Une troisième expérience a été réalisée afin de comparer l’efficacité épuratoire de l’haplotype européen envahissant du roseau commun (Phragmites australis) et de la sous-espèce locale non-invasive (P. australis subsp. americanus). La composition en espèces végétales a produit un effet notable sur la performance des marais filtrants. La comparaison des performances en mono- et en polyculture n’a pas permis de démontrer clairement les avantages de la diversité végétale pour l’élimination des polluants dans les marais filtrants. Toutefois, les marais filtrants plantés avec une combinaison d’espèces étaient aussi efficaces que les monocultures des espèces les plus performantes. La comparaison entre les deux sous-espèces de P. australis indiquent que la sous-espèce indigène pourrait remplacer le roseau exotique envahissant, évitant ainsi les potentiels risques environnementaux sans toutefois compromettre l’efficacité du traitement. Les résultats prometteurs de la sous-espèce indigène de P. australis doivent encore être testés dans des expériences à grande échelle avant d’utiliser largement cette espèce dans les marais filtrants. Nos résultats suggèrent que, dans des conditions où la performance des macrophytes disponibles est inconnue ou ne peut être déterminée, l’utilisation d’une combinaison d’espèces présente les meilleures chances d’accomplir le plus haut niveau possible d’élimination de polluants. De plus, même si la diversité végétale ne présente pas un avantage mesurable en termes d’efficacité épuratoire, celle-ci améliore la résilience des marais filtrants et leur résistance aux stress et aux maladies. / Treatment wetlands (TWs) are complex engineered ecosystems designed to remove pollutants from wastewater. In selecting plant species for TWs, the use of polycultures as well as the choice of local non-invasive species is increasingly recommended. However, to date, the majority of TWs have been planted in monoculture using invasive species, probably because the performance of native species and the possible advantages associated with plant diversity have not been clearly demonstrated. The research questions of my thesis are: Are polycultures as good as or better than monocultures for pollutant removal, and could a native species be as efficient as an exotic invasive species in TWs? Three experiments were performed to answer this question. The influence of plant richness on pollutant removal was tested in two mesocosm experiments: 1) comparing two emergent plant species in monoculture and planted in sequence, and 2) evaluating four free-floating species, each in monoculture versus pairs of species (all possible combinations) and the four species planted together. A third experiment was carried out to compare the removal efficiency of the invasive European haplotype of common reed (Phragmites australis) and the native non-invasive subspecies (P. australis subsp. americanus). Plant species composition influenced the performance of TWs. The comparison of the performance of monocultures versus polycultures showed that, overall, TWs planted with a combination of species were as efficient as monocultures of the best performing species. Comparing the performance of native and invasive P. australis strongly suggests that the native could replace the invasive species in TWs, thereby avoiding possible environmental risks without compromising treatment efficiency. The promising results of the native P. australis subspecies need to be further tested in full-scale experiments in order to encourage the use of this species in TWs. The results obtained comparing plant species combinations suggest that under circumstances in which the performance of available macrophytes is unknown or cannot be determined, using a mixture of species offers the best chances of achieving the highest possible level of pollutant removal. Furthermore, it has been suggested that plant diversity contributes to TWs in terms of their resilience to stress and disease.

In Australia, significant effort goes into reducing the amount of nitrogen and phosphorus entering inland waters from point sources. However, little is known of the extent to which riparian organic matter may act as a source of these nutrients. Also, whilst the relationships between the nitrogen, phosphorus and carbon cycles are broadly known, there is little quantitative data regarding the release of these elements from Australian riparian organic matter and their subsequent microbial mineralisation within aquatic environments. In particular, comparatively little is known of their comparative role in nutrient and organic matter cycling within anoxic zones, and the influence that different riparian organic matter may have on stream water quality. This lack of such data presently hampers the ability of water managers to make educated decisions regarding the management of riparian zones in Australia. In order to improve understanding in this area, a combination of laboratory and in situ experiments were carried out in order to compare the abiotic release and aerobic/ anaerobic mineralisation of leaf derived dissolved organic carbon (DOC), dissolved nitrate/nitrite (NOx) and soluble reactive phosphorus (SRP) under different environmental conditions. Four plants common to Australian riparian zones were investigated: two native species, Eucalyptus camaldulensis (gum) and Phragmites australis (common reed), and two exotic species, Salix babylonica (willow) and Lolium multiflorum (rye grass). After 30 days, formaldehyde inhibited 1g willow and rye grass extracts contained the most SRP (0.7 mg/L), whilst gum extracts contained 0.3 mg/L and common reed 0.1 mg/L of SRP.Willow and rye grass abiotically released twice as much NOx than gum and common reed, although concentrations were only between 0.05-0.1 mg/L. Gum and common reed released the most DOC per gram of leaf matter (14 and 12 mmol/g of leaf matter respectively), but based on the initial carbon content of each leaf type, the largest percentage contributor of DOC under abiotic conditions was common reed and rye grass (both 38% mass/mass), with gum (33% mass/mass) and willow (30% mass/mass) being smaller contributors. The most bioavailable DOC was released by rye grass and common reed, with between 83 and 94% of this DOC microbially mineralised after 30 days in oxic conditions. When conditions were not inhibited, microbial growth was evident almost immediately in willow, rye grass and common reed leaf extracts. However, microbial growth was suppressed for the first 48 hours in gum leaf extracts. After this suppression period, the rate of DOC mineralisation was equal in willow and gum leaf extracts (0.1 day-1). Under anoxic conditions, the rate and extent of DOC mineralisation of willow and gum leaves depended on the type of electron acceptor provided. Added nitrate and iron III enhanced the mineralisation of both willow and gum leaves relative to no terminal electron acceptors (from zero to 0.01-0.04 and 0.002- 0.004 moles/day respectively), but added sulphate only enhanced the mineralisation of gum leaves (0.04 moles/day). When no additional electron acceptors were provided, particulate leaf mineralisation was more extensive under oxic than anoxic conditions. However, the mineralisation of leaf derived DOC were the same regardless of oxygen availability, and after 35 days in either condition the percentage of leaf DOC mineralised for each leaf type was of the order common reed > rye grass > willow > gum. All the leaf types tested were able to sustain the caddis fly larvae Triplectides australis under controlled laboratory conditions, and survival rates were high using all four leaf types as a food source. Triplectides australis did not significantly increase the amount of DOC released from each type of leaf matter, but they did consistently increase the proportion of simple carbohydrates present within the DOC fraction. The results of these experiments suggest that changes to riparian vegetation, particularly from the native to exotic species used in this study, will inherently alter in-stream concentrations of dissolved carbon and nutrients (particularly SRP). This potentially will affect in-stream, hyporheic and subsurface processes, particularly in areas where surface water flow is low and riparian leaf inputs are high.

The objective of this work was to understand microbial population density and diversity, both spatially and temporally, in wetland mesocosms to gain a better fundamental understanding for use in the optimization and design of constructed wetlands (CWs). A standardized community level physiological profiling (CLPP) data analysis protocol was adapted and utilized for CW mesocosms. A new one-dimensional metric was developed to track community divergence using BIOLOGTM ECO plate data. The method proved easy to use, did not require a background in multivariate statistics, and accurately described community divergence in mesocosm systems. To study mesocosm biofilm-bound bacterial communities an appropriate detachment protocol was required. Various shaking protocols were evaluated for their effectiveness in the detachment of bacteria from mesocosm pea gravel, with a focus on detachment of viable and representative bacterial communities. A protocol based on mechanical shaking with buffer and enzymes was identified as an optimal approach and used further in this study. The bacterial communities associated with the interstitial water, pea gravel media, and rhizospheric regions from both planted and unplanted CW mesocosms were profiled using the CLPP method and compared. Vertical community stratification was observed for all mesocosm systems. Rhizospheric communities were found to be significantly more active than their gravel-associated counterparts, suggesting that although rhizospheric bacteria were less abundant in the mesocosms they may play a more significant role in the removal and fate of water born contaminants. The start-up dynamics of CW mesocosms was investigated using the CLPP and standard CW characterization methods over an eight month period. All mesocosms showed a steep increase in interstitial community divergence until day 75-100, at which point a steady-state was reached. The interstitial communities were also characterized in terms of similarity based on experimental design treatments (planted/unplanted and origin of seeding inoculum). Four stages were identified during the start-up consisting of an initial stage where mesocosm communities were differentiated based on origin of the inoculum, a period where adjustments and shifts occurred in all mesocosm, a time where all mesocosm communities were quite similar, and a final state where community differentiations were made based plant presence in the mesocosms.

The objective of this work was to understand microbial population density and diversity, both spatially and temporally, in wetland mesocosms to gain a better fundamental understanding for use in the optimization and design of constructed wetlands (CWs). A standardized community level physiological profiling (CLPP) data analysis protocol was adapted and utilized for CW mesocosms. A new one-dimensional metric was developed to track community divergence using BIOLOGTM ECO plate data. The method proved easy to use, did not require a background in multivariate statistics, and accurately described community divergence in mesocosm systems. To study mesocosm biofilm-bound bacterial communities an appropriate detachment protocol was required. Various shaking protocols were evaluated for their effectiveness in the detachment of bacteria from mesocosm pea gravel, with a focus on detachment of viable and representative bacterial communities. A protocol based on mechanical shaking with buffer and enzymes was identified as an optimal approach and used further in this study. The bacterial communities associated with the interstitial water, pea gravel media, and rhizospheric regions from both planted and unplanted CW mesocosms were profiled using the CLPP method and compared. Vertical community stratification was observed for all mesocosm systems. Rhizospheric communities were found to be significantly more active than their gravel-associated counterparts, suggesting that although rhizospheric bacteria were less abundant in the mesocosms they may play a more significant role in the removal and fate of water born contaminants. The start-up dynamics of CW mesocosms was investigated using the CLPP and standard CW characterization methods over an eight month period. All mesocosms showed a steep increase in interstitial community divergence until day 75-100, at which point a steady-state was reached. The interstitial communities were also characterized in terms of similarity based on experimental design treatments (planted/unplanted and origin of seeding inoculum). Four stages were identified during the start-up consisting of an initial stage where mesocosm communities were differentiated based on origin of the inoculum, a period where adjustments and shifts occurred in all mesocosm, a time where all mesocosm communities were quite similar, and a final state where community differentiations were made based plant presence in the mesocosms.