Les douleurs chroniques, d’origine inflammatoire, neuropathique ou incisionnelle, affectent environ 20 % de la population adulte et jusqu’à 50 % de la population âgée. Elles représentent ainsi un véritable enjeu de santé publique. Malgré l’existence de grandes familles d’analgésiques, les traitements restent souvent inefficaces. Cela est dû en grande partie à un manque de connaissances des mécanismes physiopathologiques de la douleur. Durant ma thèse, je me suis intéressée aux rôles et aux régulations de senseurs moléculaires de la douleur récemment mis en évidence: les canaux ioniques ASIC (« Acid Sensing Ion Channels »). Les ASIC forment une famille de canaux cationiques, excitateurs. Les canaux ASIC3, en particulier, sont présents dans les neurones sensoriels qui innervent la peau, les muscles, les viscères et les articulations. Ils sont activés par de faibles acidifications extracellulaires qui se produisent au cours de nombreux mécanismes physiopathologiques comme l’inflammation, l’ischémie, le développement tumoral, ou encore les lésions tissulaires consécutives, par exemple, à une chirurgie. Dans une première étude, nous avons montré que les canaux ASIC3 jouent un rôle primordial dans le développement des douleurs post-opératoires, notamment dans les douleurs posturales, proches des cas cliniques. A partir d’un modèle d’incision plantaire chez le rat, nous avons mis en évidence une surexpression des canaux ASIC3 dans les neurones sensoriels qui innervent la patte opérée. L’inhibition pharmacologique (toxine) et génique (siARN) d’ASIC3 in vivo réduit le comportement douloureux. Notre seconde étude a porté sur le canal ASIC3 humain, peu étudié jusqu’ici. J’ai démontré que ce canal possède une propriété originale et inductible qui lui confère une sensibilité, non seulement à l’acidification, mais également à l’alcalinisation extracellulaire. Cette sensibilité alcaline est une caractéristique intrinsèque du canal. Elle implique deux résidus arginine spécifiques à la protéine humaine et présents sur sa boucle extracellulaire. Le canal ASIC3 humain, en adaptant son activité à différents environnements de pH, pourrait ainsi participer à la régulation fine du potentiel de membrane et à la sensibilisation neuronale. Plus récemment, j’ai étudié la régulation du canal ASIC3 par des lipides inflammatoires et ses conséquences sur la douleur. De manière très intéressante, je démontre que la lysophosphatidylcholine (LPC), un lipide issu de la dégradation membranaire lors de processus inflammatoires, est un nouvel activateur du canal ASIC3 en conditions normales de pH. De plus, en synergie avec une acidose modérée (pH 7,0), la LPC et son analogue non métabolisable produisent une douleur spontanée chez les rats, qui est réduite en présence de toxine inhibitrice d’ASIC3. / Chronic, inflammatory, neuropathic, or incisional pain is affecting about 20 % of the adult population and up to 50 % of the elderly population. It thus represent a real public health issue. Despite the existence of large families of analgesics, treatments are often ineffective. This is due in large part to a lack of knowledge of the patho-physiological mechanisms of pain. During my PhD, I have been interested in the roles and regulation of molecular sensors of the pain recently highlighted: ion channels (ASICs "Acid Sensing Ion Channels "). ASICs constitute a family of excitatory cationic channels. The ASIC3 channels, in particular, are present in sensory neurons that innervate the skin, muscles, organs and joints. They are activated by low extracellular acidification occurring in many patho-physiological mechanisms such as inflammation, ischemia, tumor growth, or the subsequent tissue damage, for example, surgery. In a first study, we showed that ASIC3 channels play a crucial role in the development of post -operative pain, including postural pain, close to clinical cases. From a plantar incision model in rats, we demonstrated an over-expression of ASIC3 channels in sensory neurons innervating the operated hindpaw. Pharmacological inhibition (with toxin) and invalidation (siRNA) of ASIC3 in vivo reduce pain behavior. Our second study focused on the human ASIC3 channel, not yet extensively studied. I demonstrated that this channel has a unique and inducible property which gives it a sensitivity not only to acidification, but also to the extracellular alkalinization. This alkaline sensitivity is an intrinsic characteristic of the channel. It involves two specific arginine residues in the human channel that are present in its extracellular loop.Thus the human ASIC3 channel adapts its activity at different pH environments, and could participate in the fine regulation of membrane potential and neuronal sensitization. More recently, I have studied the regulation of ASIC3 channel by inflammatory lipids and there effects on pain. Interestingly, I showed that lysophosphatidylcholine (LPC), a lipid produced from the degradation of the membrane during inflammation, is a new activator of ASIC3 channel under normal pH conditions. Moreover, in synergy with moderate acidosis (pH 7.0), the LPC and its non-metabolizable analogue produce spontaneous pain in rats. This pain is reduced in the presence of the ASIC3 inhibitory toxin.

Le plancton a un rôle crucial dans le cycle du carbone. Il est donc primordial de projeter son évolution dans le contexte de changement climatique. Une partie des résultats rapportés au niveau des communautés planctoniques montrent une stimulation de la production primaire avec l’augmentation de concentration en CO2 et très peu d’expériences combinant plusieurs facteurs ont été faites. Qui plus est, les expériences ont été réalisées majoritairement dans des conditions naturellement élevées ou enrichies en sels nutritifs et très peu de données existent dans les zones naturellement pauvres en nutriments et chlorophylle a, c’est à dire dans les zones oligotrophes telles que la mer Méditerranée, bien que ces régions représentent une surface importante et en expansion de la surface de l’océan. Plusieurs approches ont été utilisées au cours de cette thèse pour étudier les effets du réchauffement et de l’acidification de l’océan sur des communautés planctoniques dans le NO de la Méditerranée. Une des approches, restreinte à l’effet de l’acidification seule, a été l’utilisation de mesocosmes. En Baie de Calvi (expérience #1; été 2012 sur 22 jours) la communauté étudiée présentait un efficace processus de recyclage des sels nutritifs ainsi qu’une production régénérée importante alors que dans le Baie de Villefranche (expérience #2; hiver/printemps 2013 durant 11 jours) la communauté était caractérisée plutôt par un système autotrophe et par une production nouvelle dominante. Une troisième expérience a été réalisée pour étudier les effets synergétiques de l’acidification et du réchauffement de l’océan (expérience #3; March 2012; post-bloom). Toutes les expériences ont ainsi été menées dans des conditions de faibles concentrations en sels nutritifs avec des communautés dominées par des petites espèces phytoplanctoniques telles que des haptophytes, cynaobacteries et chlorophytes. Lors de l’expérience #3, toutes les populations ont décliné au cours de l’expérience (12 jours) à l’exception des cyanobactéries (principalement Synechococcus spp.) qui ont significativement augmenté durant cette période. Cette augmentation était d’autant plus prononcée dans les conditions de température plus élevée, bien que l’augmentation concomitante de CO2 ai eu tendance à limiter cet effet. Pour les trois expériences, l’acidification de l’océan seule n’a pas montré d’effet sur les taux métaboliques quelque soit la méthode utilisée (O2-LD, marquage au 18O, 13C et 14C) alors que durant l’expérience #3, les conditions élevées en température ont favorisé la production brute déterminée par la méthode de marquage 18O. Des biomarqueurs spécifiques, les acides gras des lipides polaires, utilisés de façon combinée avec du marquage au 13C a permis la détermination des productions primaires par groupe. Ceci a confirmé que l’acidification de l’océan seule n’a pas particuliérement favorisé un groupe phytoplanctonique par rapport à un autre dans nos conditions expérimentales.Basé sur nos résultats et sur une revue de littérature, il apparait que la plupart des expériences (57 % des études) réalisées jusqu’à maintenant n’ont pas montré d’influence notoire de l’acidification de l’océan seule sur les communautés planctoniques, alors que le réchauffement de l’océan semble avoir plus d’effet sur la composition et la production planctonique. De plus, la biomasse dans les écosystèmes dominés par des petites espèces de phytoplancton semble être insensible à l’augmentation de CO2. A l’heure actuelle, il est impossible, basé sur ces résultats, de fournir un concept général de l’effet de l’acidification de l’océan sur les communautés planctoniques. Cependant il semble que l’acidification n’augmentera pas la biomasse et la production primaire pour la majorité des communautés. / Plankton plays a key role in the global carbon cycle. It is therefore important to projectthe evolution of plankton community structure and function in a future high-CO2 world.Several experimental results reported at the community level have shown increased rates ofprimary production as a function of increasing pCO2 and few multi-driver experiments havebeen performed. However, the great majority of these experiments have been performedunder high natural or nutrient-enriched conditions and very few data are available in areaswith naturally low levels of nutrient and chlorophyll i.e. oligotrophic areas such as theMediterranean Sea, although they represent a large and expanding part of the ocean surface.Several approaches have been used during this thesis to investigate the effects ofocean warming and acidification on plankton communities in the NW Mediterranean Sea.One approach, restricted to the investigation of ocean acidification effects alone, was the useof mesocosms. In the Bay of Calvi (experiment #1; summer 2012 during 22 days), thecommunity was very efficient in recycling nutrients and showed important regeneratedproduction while in the Bay of Villefranche (experiment #2; winter/spring 2013 during 11days) the community was characterized by a more autotrophic state and larger newproduction. A third experiment was set-up to investigate the combined effects of oceanacidification and warming in small containers in the Bay of Villefranche (experiment #3;March 2012; post-bloom conditions).All experiments were conducted under low nutrient conditions with communitiesdominated by small species (e.g. haptophytes, cyanobacteria, chlorophytes). During the thirdexperiment, biomass of populations decreased throughout the experiment (12 days), exceptcyanobacteria (mostly Synechococcus spp.) that significantly increased during that period.This increase was even more pronounced under elevated temperature, albeit the combinationwith elevated pCO2 tended to limit this effect. For the three experiments, ocean acidificationalone had no effect on any of the metabolic processes, irrespective of the methods used (O2-LD, as well as 18O, 13C and 14C labelling) while during the multi-driver experiment #3, oceanwarming led to enhanced gross primary production as measured by the 18O labellingtechnique. Specific biomarkers, polar lipid fatty acids, were used in combination with 13Clabelling to assess group primary production rates. This confirmed that ocean acidificationalone did not favour any phytoplankton group under our experimental conditions.Based on our findings and on an extensive literature review, it appears that most (57%) of the experiments performed to date have shown no effect of ocean acidification alonewhile ocean warming seem to have an effect on plankton composition and production.Furthermore, plankton biomass in ecosystems dominated by small phytoplankton speciesappears insensitive to elevated CO2. It remains, for the moment, impossible based on thesefindings to provide a general concept on the effect of ocean acidification on planktoncommunities. However, it appears that ocean acidification will likely not lead to increasedbiomass and primary production rates for most communities, as it was previously anticipated.Furthermore, although warming will likely lead to increased primary production, it appearsthat small species with a low capacity for export will be favoured. If this proves to be awidespread response, plankton will not help mitigating atmospheric CO2 increase through anenhancement of the biological pump.

L'objectif de cette thèse a été d'évaluer l'effet biogéochimique de deux forçages : l'acidification de l'océan et les dépôts de poussières sahariennes. Dans un premier temps, nous avons montré que dans une région dite Low Nutrient Low Chlorophyll (LNLC) l'effet de l'acidification de l'océan sur les cycles marins de l'azote (N), du phosphore (P) et du fer (Fe) sera surement négligeable. L'acidification des eaux de surface appauvries en N et P n'affecterait pas la spéciation de ces éléments, et la composition de la communauté planctonique, n'étant pas significativement modifiée, n'induirait pas de changement dans la dynamique des nutriments inorganiques. Dans un deuxième temps, les expériences menées pendant cette thèse nous ont permis de mieux paramétriser les processus post-dépôts des nutriments atmosphériques à la surface de l'eau de mer lors d'un évènement saharien. Les échanges dissous/particulaire ont lieu sur une courte échelle de temps. Ils sont à la fois contrôlés par la dynamique verticale des particules et la nature de la matière organique dissoute (DOM) pouvant s'agréger sur les particules lithogéniques. Dans des conditions d'acidification de l'océan, alors que la dissolution des éléments anthropiques adsorbés sur les poussières sahariennes, tels que l'azote inorganique, ne sera pas affectée, celle des éléments d'origine crustale (P et Fe) pourrait être accrue ou accélérée selon les agrégats organique-minéral formés. Le rôle majeur du processus d'agrégation dans la mise à disposition des nutriments atmosphériques a été mis en évidence par une rapide et importante formation abiotique de particules exopolymériques transparentes juste après le dépôt de poussières. / The objective of this thesis was to assess the biogeochemical effect of two forcings: the ocean acidification and the dust deposition. Firstly, we showed that in the Low Nutrient Low Chlorophyll (LNLC) area the effect of the ocean acidification on the marine cycle of nitrogen (N), phosphorus (P) and iron (Fe) will be likely negligible. The pH decrease of the surface waters depleted in N and P would not affect the speciation of these elements, and the absence of effect on the composition of the plankton community would not lead to a shift in the dynamic of inorganic nutrients. Secondly, the experiments performed during this thesis allowed a better parametrization of the post-depositional processes of atmospheric nutrients in the surface seawater after a Saharan event. The exchanges dissolved/particulate occurred in the short timescale. They were controlled by both the particles dynamic and the nature of the dissolved organic matter (DOM) that can aggregate with the lithogenic particles. Under ocean acidification conditions, while the dissolution of anthropogenic elements adsorbed onto dust, such as the inorganic nitrogen, will not be affected, the dissolution of the crustal elements (P and Fe) could be higher and faster according the formation of organic-dust aggregates. The major role of the aggregation process on the availability of atmospheric nutrients was highlighted by the rapid and large abiotic formation of transparent exopolymeric particles (TEP) following the dust deposition to the surface waters.

Focalisé sur le groupe phytoplanctonique des diatomées, ce travail de thèse a permis d'étudier l'impact du réchauffement climatique et de l'acidification des océans afin d'appréhender la réponse de ce taxon au changement climatique actuel. L'augmentation de la pCO2 atmosphérique depuis la première révolution industrielle est à l'origine de l'augmentation de la concentration en carbone inorganique dissous (DIC) dans l'océan de surface, et donc d'une acidification des océans à laquelle s'ajoute un réchauffement de l'océan de surface conduisant finalement à l'extension des zones oligotrophes très stratifiées et pauvres en sels nutritifs. Différentes approches in situ et au laboratoire ont donc été utilisées lors de ce travail de thèse afin de mieux comprendre la place des diatomées dans une province oligotrophe et d'apprécier ensuite leur réponse à un réchauffement et une acidification dans un «chémostat oligotrophe», limité en phosphate. / Specifically orientated on the diatoms' phytoplanktonic group, this work tryed to understand the impact of warming and ocean acidification on diatoms and aimed at understand the taxon's response to the ongoing climate change. Amospheric pCO2 increase since the first industrial revolution lead to the augmentation of dissoveld inorganic carbon (DIC) concentration in the surface ocean, and thus to the ocean acidification, accompanied by an ocean surface warming leading finally to the extension of oligotrophic areas well stratified and nutrient depleted. Different in situ and lab techniques were used in order to better understand the diatom role in oligotrophic system and their response to warming and acidification in an oligotrophic chemostat, limited by phosphate.

The cellular regulation of acidification and intracellular ph (pHi) was studied in the integument of Rana pipiens, a model renal epithelium. Acidification was enhanced by : (1) chronic metabolic acidosis, (2) high salinity adaptation, and (3) ibuprofen treatment.

Compte tenu de la forte incitation réglementaire à la valorisation de déchets de cuisine, le développement de procédés de méthanisation à petite échelle (10 à 100 T de déchets par an) pourrait voir un essor potentiellement important. Cependant, la simplicité (préparation limitée des substrats, peu d'apport d'eau) et la robustesse (stabilité) du procédé représente des enjeux cruciaux pour valider cette échelle de fonctionnement. Dans le procédé de méthanisation, l'étape de l'hydrolyse reste la plus limitante due, d'une part, à une lente cinétique, qui provoque une dégradation non uniforme des carbohydrates structuraux (p.ex. la cellulose), et d'autre part, d'une transformation rapide des composants facilement biodégradables, ce qui peut générer une accumulation des acides gras volatiles, conduisant à une inhibition de l'activité méthanogène. Dans l'objectif de surmonter les problèmes liés à l'étape de l'hydrolyse, de nombreux travaux ont été menés sur les prétraitements mécaniques, thermiques, ou chimiques de la matière organique. En comparaison, l'utilisation d'une pré-étape aérobie a été relativement peu étudiée. Un prétraitement aérobie pourrait aider à éliminer les fractions les plus biodégradables pour limiter les risques d'acidose du milieu et à mieux dégrader certaines fractions de la matière organique plus résistante. Toutefois l'utilisation d'un prétraitement aérobie peut provoquer une oxydation excessive des déchets, limitant leur potentiel méthanogène. Par conséquent, il est indispensable de bien maîtriser les conditions d'aération. Ce travail de thèse avait donc l'objectif de valider l'impact du prétraitement aérobie dans la digestion anaérobie de déchets de cuisine et de suggérer quel mode de mise en œuvre du prétraitement aérobie faudrait préconiser. / Given the strong incentive to source separation of organic fractions of household waste, the development of anaerobic processes on a small scale (10 to 100 t of waste per year) could see significant growth. However, to validate this scale of operation, stability and efficiency of the treatment process will represent crucial issues. Concerning anaerobic processes, the hydrolysis step is the limiting step for two reasons. First, due to relatively slow kinetics, non-uniform degradation of structural carbohydrates (e.g. cellulose) may be produced. On the other hand, the rapid transformation of easy biodegradable compounds produces a rapid production of volatile fatty acids, which may lead to their accumulation, inhibiting the methanogenic activity. To overcome the problems associated with the hydrolysis step, many studies have been conducted on the mechanical, thermal or chemical pre-treatment of the organic matter introduced into the digesters. In comparison, the use of an aerobic biological pre-stage has been relatively less studied. Aerobic degradation can indeed eliminate more biodegradable fractions to reduce the risk of acidosis in the digester and enhance the degradation of some recalcitrant organic fraction. However the duration of the aerobic treatment should be well managed not to oxidize excessively the methanogenic potential of the pre-treated organic waste. The aim of the thesis was be to validate the effectiveness of a pre-treatment to improve the anaerobic digestion of food waste and to suggest the best ways to implement this pre-treatment.

L’océan côtier occupe une position clé dans le cycle du carbone et est exposé à l’acidification des océans. Une grande partie de matière organique(MO) marine et continentale est minéralisée dans les sédiments estuariens par des voies aérobies ou anaérobies. Cette minéralisation produit du carbone inorganique dissous (DIC), mais aussi de l’alcalinité totale(TA) pour la partie anoxique, ce qui tamponne les variations de pH du système et augmente la capacitéde l’eau de mer à absorber du CO2. Des mesures dans les sédiments du prodelta du Rhône ont montré que la minéralisation anoxique, surtout la sulfato-réduction, y est dominante et produit des forts flux de TA et de DIC. Proche de l’embouchure, c’est surtout la MO continentale qui est minéralisée et la fraction marine augmente vers le large. Une expérience d’acidification des sédiments de la baie de Villefranche-sur-mer a montré que l’acidification des océans cause la dissolution des carbonates ce qui tamponne le pH dans les sédiments. / Continental shelves are key regions for theglobal carbon cycle and particularly exposed to oceanacidification. A large part of organic matter (OM) ofcontinental and marine origin is mineralized in estuarinesediments following oxic and anoxic pathways.This mineralization produces dissolved inorganic carbon(DIC) leading to acidification of the bottom waters.Anoxic mineralization can produce total alkalinity(TA) that can contribute to buffer bottom water pHand increase the CO2 storage capacity of seawater. Measurementsin the sediments of the Rhˆone River prodeltashowed that anoxic mineralization, especially sulfate reduction,are the major pathways of OM mineralizationand create high DIC and TA fluxes. Land derived OMis mineralized close to the river mouth and marine OMtakes over on the shelf. An acidification experiment withsediment cores from the bay of Villefranche evidencedthat acidification causes carbonate dissolution at thesediment surface that buffers porewater pH.

Doctor of Philosophy / Department of Diagnostic Medicine and Pathobiology / Kyeong-Ok Chang / Caliciviruses are important pathogens of humans and animals. Noroviruses are major causes of foodborne gastroenteritis cases, but their research is hindered due to the inability to grow human noroviruses in cell culture. Detailed studies on entry events of caliciviruses are lacking and may be crucial for development of cell culture models. We examined the entry events of caliciviruses using porcine enteric calicivirus (PEC), feline calicivirus (FCV) and murine norovirus-1 (MNV-1). PEC replication in LLC-PK cells requires bile acid in the medium, but the mechanism is not well understood. Our studies showed that bile acids are required in the early stage of virus replication, and while internalization of PEC is not dependent of them, they are required for endosomal escape and successful replication. Further examination on virus entry, we demonstrated that endosomal acidification and cathepsin L activity are essential in the replication of PEC, FCV and MNV-1. The results showed that inhibition of endosomal acidification or cathepsin L activity led to retention of viruses in the endosomes. Also we demonstrated that recombinant cathepsin L cleaved structural protein of PEC, FCV or MNV-1, which suggests that the enzyme may facilitate uncoating viruses in endosomes. In addition to bile acids, we found that a cold shock treatment during virus entry supported PEC replication by facilitating the endosomal escape. While PEC alone did not induce ceramide formation, bile acids or cold shock treatment induce ceramide formation on endosomes through activation acid sphingomyelinase (ASM), and this event was crucial for virus replication because inhibition of ASM blocked ceramide formation and significantly reduced PEC replication. Incubation of FCV or MNV-1 with cells led to ceramide formation during virus entry, and inhibition of ASM also significantly reduced their replication. Inhibition of ASM led to endosomal retention of PEC, FCV or MNV-1 during virus entry, which may be the reason for the reduction of viral replication. These studies revealed the important and common events during calicivirus entry for successful replication, including virus endosomal escape, cathepsin L activity and ASM/ceramide formation. This detailed information may provide clues for understanding the replication of fastidious caliciviruses and for potential therapeutic targets.

Highbush blueberry (Vaccinium corymbosum L.) is adapted to soils with high organic matter and acidic pH. Composts provide organic matter and nutrients for growing blueberry in mineral soils, but many composts are high in pH and soluble salts. Acidification with elemental sulfur (S°) can remedy high pH, but the process further increases compost salinity. The objectives of this study were to: i) determine the effects of diverse composts on blueberry growth and nutrient uptake, ii) determine whether S° acidification can ameliorate the negative effects of high compost pH, and iii) develop and validate a simple titration method to determine pH buffering capacity of compost. In our first study, ten composts were evaluated under greenhouse conditions with one-year-old blueberry. Each compost was either acidified or not with S° and then mixed 30% by volume with silt loam soil before planting. Controls were sawdust incorporation or soil only. Plants were managed with a low rate of fertilization to emphasize compost effects on nutrient supply. Compost inorganic nitrogen (N) ranged from 0.1 to 4.1 g∙kg⁻¹, and NO₃-N to NH₄-N ratios were greater than 20:1. Aboveground plant growth and nutrient uptake, including N, phosphorous (P), potassium (K), and boron (B) were higher in soil with compost than in soil with sawdust or soil only. Composts with pH < 7.5 produced more shoot growth than those with higher pH, and composts with EC > 2 dS∙m⁻¹ produced less root growth than those with lower EC. Adding S° reduced compost pH by an average of 1.9 units, and acidification increased shoot and root growth in the composts as well as uptake of many nutrients. Plant growth and N uptake were not correlated with compost N supply. Composts with greater amounts of plant-based feedstocks produced more total shoot growth than manure-based composts. In our second study, 3.7 L blueberry transplants were grown outdoors for 119 d in pots containing compost and soil. Manure feedstocks included separated dairy solids or horse stall cleanings. Plant feedstocks included urban yard trimmings, leaves from street sweeping, conifer bark conditioned with municipal biosolids, or peppermint distillation residue. Control treatments were sawdust amendment or soil only. Plant-based compost treatments had less effect on soil pH and produced 20% greater plant growth than manure-based compost treatments. Plant growth was not different with plant-based composts vs. the sawdust amendment control. Elemental S addition at potting did not acidify soil enough to overcome the increase in pH resulting from compost addition. In our third study, we titrated eight composts with dilute H₂SO₄ to predict response to S° acidification. Our objective was to develop and validate a simple method to determine the pH buffering capacity of compost. Compost pH decreased linearly with laboratory acid addition. Compost pH buffering capacity (linear slope of titration curve) was 0.16 to 0.39 mol H⁺ per kg dry compost per pH unit. To determine correlation between titration and S° acidification, composts samples were incubated with S° at 22° C for 70 d. The majority of the decrease in pH from S° addition occurred within 28 d. Compost pH at 28 d was closely predicted by the laboratory titration. Because of the linearity of compost response to acid addition, a 2-point titration method (one rate of acid addition) is an effective alternative to the 7-point method we used. We conclude that compost pH is the primary limiting factor affecting blueberry response to compost. Compost incorporation provided benefit to blueberry, especially under low N management, and generally increased plant growth and nutrient uptake when compared with plants grown in mineral soil only. Composts made from plant-based feedstocks, rather than manure-based feedstocks, tend to have characteristics which favor blueberry growth, including low buffering capacity, pH, and soluble salts. Feedstocks which showed promise include deciduous leaves, yard debris, bark, and horse bedding with low manure content. Acidification of composts with S° increased plant growth and nutrient uptake, and is a promising technology for eliminating the negative effects of high compost pH. Our method of laboratory titration with dilute acid addition was effective in determining pH buffering capacity of compost, and predicted the compost acidification by S° and the effect of compost on soil pH. / Graduation date: 2012

The studies presented in this thesis were designed to investigate the effects of reduced sea water pH on the behaviour of intertidal decapod crustaceans, both within the context of the variations occurring naturally in the pH of rock pool habitats, and in relation to predicted changes to ocean pH resulting from ocean acidification and potential carbon dioxide (CO2) leaks from carbon capture storage (CCS) sites. Recent studies on marine fish have shown behavioural disruptions as a result of increased CO2 concentrations in sea water and reduced pH, but the effects on crustaceans are as yet unknown. The first two studies investigated the effects of reduced pH upon the olfactory behaviour of the prawn Palaemon elegans and the hermit crab Pagurus bernhardus, focussing on their responses to food odours. Short-term (five day) exposures to highly reduced pH (pHNBS = 6.60, 6.80) revealed disruptions to the chemo-sensory behaviour of both species with a reduction in their ‘sniffing’ response, and the inability of P. bernhardus to locate the chemical cue. This was also accompanied by elevated haemolymph chloride ions. in In a further study P. bernhardus was subjected to a longer exposure (60 days) and to a range of pH levels (pHNBS = 8.00, 7.90, 7.70, 7.35 and 6.80) in order to detect a threshold for the behavioural disruptions observed, and to determine if there would be any sign of acclimation over a longer period. A clear gradient in the disruptions to the chemo-sensory responses and survival rates of the hermit crabs, and disruption to a physiological marker (elevated haemolymph calcium ions), was found. Possible thresholds for disruption were also identified at levels that match predictions for ocean acidification and leaks from proposed CO2 CCS sites. Some of the crabs in the lower pH treatments exhibited a recovery in their responses by day 60, possibly indicating an acclimation effect. The presence of disruption to haemolymph ion concentrations in both the short and longer term hermit crab studies suggest a mechanism for behavioural disruption. In a final study the effects of reduced sea water pH on a more complex behaviour, involving decision making, was investigated. Reduced sea water pH was shown to disrupt the shell assessment and selection behaviour of P. bernhardus affecting its decision making processes, although not all crabs were affected in the same way. The work presented here therefore demonstrates that reduced sea water pH could have disruptive effects upon both information gathering, via chemo-sensory processes, and decision making in intertidal crustaceans. The mechanism responsible is unlikely to be due to changes in the odour molecule, or physical damage to receptor organs. Rather the observed disruptions could be due (a) to ionic changes, causing metabolic depression or interference with neurotransmitter function, or (b) to disruption to chemoreception per se. Such disturbances to key behavioural processes have implications for inter and intraspecific species interactions and population dynamics in the marine environment. Changes in pH are already experienced by intertidal animals for short periods when rock pools are emersed, but future anthropogencially-induced reductions in sea water pH are likely to cause more sustained and widespread disruptions with, as yet, unpredictable consequences. The differential responses observed between individuals in these studies may warrant further investigation as such differences may provide the basis for selection and adaptation to projected changes in ocean pH.