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Many of the world’s lakes are located at high latitudes in the northern hemisphere where seasonal ice cover is common. The ice restricts lake-atmosphere gas exchange, causing an under-ice accumulation of CO2. However, there are few spatial under-ice CO2 studies of river influence on lakes. Here, I examine the river plume of a river-influenced bay and compare it to a control bay without river influence in lake Örträsk, a humic of 7 km2 lake in boreal Sweden. There was no relationship between CO2 or DIC and distance from the Vargån river outlet in Vargån bay, even though the CO2 and DIC concentration of the river was found lower in Vargån river (median CO2: 53,2 µM; DIC: 178 µM) than in Vargån bay (median CO2: 84,7 µM; DIC: 301 µM). The median values of the control bay were CO2: 92,7 µM and DIC: 345 µM. There was a negative relationship in CO2 concentration with distance in the control bay, but not in DIC. The control bay had a higher concentration of CO2 at 0-60 m distance than Vargån bay, but there was no difference at 70-180 m. The DIC concentration was higher in the control bay than in Vargån bay. I have reported lower CO2 and DIC concentrations in the river than in the lake, which is not in accordance with literature and is probably due to an earlier ice-melt in the river than in the lake. The negative CO2 relationship in the control bay is likely due to sediment respiration.

[EN] This research work constitutes a first approximation to the study of the viability of carbonic fertirrigation in citrus fruits as a CO2 drain potential. To that effect, carbonic fertirrigation experiments were carried out with citrus fruits of the Nadarcott variety from the year 2010 to the year 2015. The study required the monitoring of parameters related to the leaf surface, the phenological state of the trees, the ground, the leaves and the fruits of the tested trees. The analysis of the results obtained showed there were no significant differences in the size and quality of the fruits irrigated with CO2. Differences were neither observed in the trees' vegetative development nor in the advance or delay of the blooming and formation of fruits. The analysis of the grounds revealed that the content in organic matter of the grounds irrigated with CO2 was higher than in the grounds used as reference in at least two tenths of a percentage. Similarly, it was noted that the content in iron in the leaves of the trees irrigated with CO2 was significantly higher than in the trees used as reference. The statistical analysis carried out confirmed these conclusions, noting a 24% increase over the average value in the case of the organic matter in the ground and of a 16% in the case of the iron content in the leaves. Both factors indicate that carbonic fertirrigation does have relevant agronomic repercussions, especially on the organic fraction of the ground and on the iron soluble fraction. Various authors confirm the mobilisation of the iron produced by the decrease in the pH of the irrigation water - this study confirms this fact and strengthens the usage of carbon dioxide as a potential substitute of strong acids normally used for this purpose. The increase in the content of the ground's organic matter is an especially interesting result, as it was not expected, even though some authors have related the decrease of soil respiration to different cultural practices that improve the ground's texture. The interaction between the CO2 of the irrigation water and the content in organic matter in the ground and, therefore, soil respiration must be studied in further detail in a future, with experiences specially aimed at valuing the repercussions of this practice on both parameters. / [ES] Este trabajo de investigación constituye una primera aproximación al estudio de viabilidad de la fertirrigación carbónica en cítricos como potencial sumidero de CO2. A tal efecto, se llevaron a cabos experimentos de fertirrigación carbónica con cítricos de la variedad Nadarcott desde el año 2010 hasta el año 2015. El estudio requirió la monitorización de parámetros relacionados con la superficie foliar, los estados fenológicos de los árboles, el suelo, las hojas y los frutos de los árboles ensayados. El análisis de los resultados obtenidos mostró que no había diferencias significativas en el tamaño y calidad de los frutos regados con CO2. Tampoco se observaron diferencias en el desarrollo vegetativo de los árboles ni en el avance o retraso de la floración y formación de los frutos. Los análisis de los suelos revelaron que el contenido en materia orgánica de los suelos regados con CO2 era más alto que los suelos tomados como referencia en al menos dos décimas porcentuales. De la misma manera, se observó que el contenido en hierro en las hojas de los árboles regados con CO2 era significativamente más alto que en los árboles tomados como referencia. Los análisis estadísticos realizados confirmaron estas conclusiones, observándose un incremento del 24% sobre el valor promedio en el caso de la materia orgánica del suelo y del 16% en el caso del contenido en hierro de las hojas. Ambos factores indican que la fertirrigación carbónica sí que tiene repercusiones agronómicas relevantes, especialmente sobre la fracción orgánica del suelo y sobre la fracción soluble de hierro. Diversos autores confirman la movilización del hierro producido por la disminución del pH del agua de riego; este estudio confirma este hecho y refuerza la utilización del dióxido de carbono como potencial sustituto de los ácidos fuertes normalmente utilizados para este cometido. El aumento en el contenido de materia orgánica del suelo es un resultado especialmente interesante, pues no era esperado pese a que algunos autores han relacionado la disminución de la respiración edáfica con diferentes prácticas culturales que mejoran la textura del suelo. La interacción entre el CO2 del agua de riego y el contenido en materia orgánica del suelo y, por tanto, la respiración edáfica deben de ser estudiados con más detalle, en un futuro con experiencias especialmente dirigidas a valorar las repercusiones de esta práctica sobre ambos parámetros. / [CA] Aquest treball d'investigació constitueix una primera aproximació a l'estudi de la viabilitat de la fertirrigació carbònica en cítrics com a potencial embornal de carboni. Amb aquesta finalitat es dugueren a terme experiments de fertirrigació carbònica amb cítrics de la varietat Nadorcott des de l'any 2010 fins l'any 2015. L'estudi va requerir la monitoratge de paràmetres relacionats amb la superfície foliar, els estat fenològics del arbres, el sòl, les fulles i el fruits dels arbres assatjats. L'anàlisi dels resultats obtinguts mostrà que no hi havia diferències significatives en el tamany i qualitat del fruits regats amb CO2. Tampoc es varen observar diferències en el desenvolupament vegetatiu dels arbres ni en l'avanç o retard de la floració i formació dels fruits. Les anàlisis dels sòls revelaren que el contingut de matèria orgànica dels sòls regats amb CO2 era més alt que els sòls considerats com a referència en, almenys, dues dècimes percentuals. De la mateixa manera, s'observà que el contingut de ferro en les fulles dels arbres regats amb CO2 era significativament més alt que en els arbres referència. Les anàlisis estadístiques realitzades confirmaren aquestes conclusions, observant-se un increment del 24% sobre el valor mitjà en el cas de la matèria orgànica del sòl i del 16% en el cas del contingut en ferro de les fulles. Tots dos factors indiquen que la fertirrigació carbònica sí que té repercusions agronòmiques rellevants, especialment, sobre la fracció orgànica del sòl i la fracció soluble de ferro. Diferents autors confirmen la mobilització del ferro produit per la disminució del pH de l'agua de reg; aquest estudi confirma aquest fet i reforça l'ús del diòxid de carboni com a potencial subsutitut dels àcids forts normalment gastats per a aquesta tasca. L'augment en el contingut de matèria orgànica del sòl és un resultat especialment interessant, ja que no era esperat, malgrat que alguns autors han relacionat la disminució de la respiració edàfica amb diferents pràctiques culturals que milloren la textura del sòl. La interacció entre el CO2 de l'aigua de reg i el contingut en matèria orgànica del sòl i, per tant, la respiració edàfica han de ser estudiats amb més detall en un futur amb experiències especialment dirigides a valorar les repercussions d'aquesta pràctica sobre tots dos paràmetres. / Tarazona Díez, JV. (2015). ANÁLISIS DEL POTENCIAL DE LA FERTIRRIGACIÓN CARBÓNICA EN CÍTRICOS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59405

Understanding the drivers of climate change requires knowledge about the global carbon (C) cycle. Although inland waters play an important role in the C cycle by emitting and burying C, streams and lakes are in general overlooked in bottom-up approached C budgets. In this thesis I estimated emissions of carbon dioxide (CO2) and methane (CH4) from all lakes and streams in a 15 km2 subarctic catchment in northern Sweden, and put it in relation to the total catchment C exchange. I show that high-latitude aquatic systems in general and streams in particular are hotspots for C emission to the atmosphere. Annually, the aquatic systems surveyed in this study emitted about 10.8 ± 4.9 g C m-2 yr-1 (ca. 98 % as CO2) which is more than double the amount of the C laterally exported from the catchment. Although the streams only covered about 4% of the total aquatic area they emitted ca. 95% of the total aquatic C emission. For lake emissions, the ice break-ups were the most important annual events, counting for ca. 45% of the emissions. Overall, streams dominated the aquatic CO2 emission in the catchment while lakes dominated CH4 emission, 96 % and 62 % of the totals, respectively. When summing terrestrial and aquatic C fluxes together it showed that the aquatic emissions alone account for approximately two thirds of the total annual catchment C loss. The consequence of not including inland waters in bottom-up derived C budgets is therefore a risk of overestimating the sink capacity of the subarctic landscape. However, aquatic systems can also act as C sinks, by accumulating C in sediment and thereby storing C over geological time frames. Sediment C burial rates were estimated in six lakes from a chronology based on 210Pb dating of multiple sediment cores. The burial rate ranged between 5 - 25 g C m-2 yr-1, which is of the same magnitude as lake C emissions. I show that the emission:burial ratio is about ten times higher in boreal compared to in subarctic-arctic lakes. These results indicate that the balance between lakes C emission and burial is both directly and indirectly dependent on climate. This process will likely result in a future increase of C emissions from high-latitude lakes, while the C burial capacity of these same lakes sediments weaken.

Unproductive lakes are one of few natural landscape compartments with net release of carbon to the atmosphere. Lakes also generally decrease the net terrestrial carbon uptake, since most of the CO2 production in unproductive lakes are derived from organic carbon produced on land (e.g. in forests). High latitude lakes are predicted to be particularly affected by the global climate change. The carbon cycling in these lakes and their role in the landscape are therefore important to study. In this thesis, carbon turnover processes were studied in two lakes above the arctic circle (Lake Diktar-Erik and Lake Merasjärvi) in year 2004 and 2005. Both lakes were net heterotrophic, with large variations in CO2 concentrations both on shorter (30min) and longer (24h) time-scales. The pelagic habitat supported a major part of the net production of CO2, with larger dynamics in the CO2 production than the sediments. The CO2 variations of the surface water were related to respiration of allochthonous organic carbon, and were affected by the concentration and quality of the DOC, as well as the whole lake water temperatures, and vertical water movements. The emission of CO2 from Lake Merasjärvi was measured with the eddy covariance tech­nique. The results showed that the gas transfer rate during moderate winds were higher than expected, causing the two most commonly used models to underestimate the long term fluxes of CO2 from the lake. Taken together, the results of the thesis show that the studied lakes contributed to bring terrestrial organic carbon back into the atmosphere, driven by a substantial internal CO2 production based on mineralization of allochthonous organic carbon. Major results are that the eddy covariance technique indicated that commonly used models tend to underestimate the net release rate of CO2 from lakes to the atmosphere, and that the lake CO2 dynamics can be the results of interactions between biogeochemical and physical processes in the lake water.

Many of the habitats occupied by fish are highly dynamic, naturally demonstrating substantial abiotic fluctuations over diurnal, tidal or seasonal cycles. It is also the case that throughout their 545 million year evolutionary history, fish have existed in aquatic environments very different to those of the present day. However, the past several decades have seen unprecedented rates of environmental change, at local and global scales, arising from human activities. The two major themes of the present thesis are: 1) Respiratory responses of fish to changes in environmental oxygen and temperature in the context of exploring intra- and inter-specific trait variation and its ecological implications 2) The effects of environmental factors (oxygen, carbon dioxide, temperature and seawater chemistry) on the intestinal precipitation and excretion of calcium carbonate by marine teleosts. In the first study (chapter two) a comprehensive database of fish critical PO2 (Pcrit) data compiled from the published literature is presented. The systematic review of this literature provided the opportunity to critically examine methodologies for determining Pcrit as well as its usefulness as an indicator of hypoxia tolerance in fish. The second study (chapter three) examines whether inter- and intra-specific variation in thermal and hypoxia tolerance in two reef snapper species (Lutjanus carponotatus and Lutjanus adetii) reflects their distributions across the contrasting biophysical environments of the reef flat and reef slope surrounding Heron Island on the Great Barrier Reef. L. carponotatus was clearly the most thermally and hypoxia tolerant of the two species, demonstrating a ~3.5 °C wider thermal tolerance zone (higher CTmax, lower CTmin) and ~26% lower Pcrit than L. adetii. These results suggest that the contrasting distribution of these species between flat and slope reef zones is reflected in their physiological tolerances. However, there was no evidence of intra-species variation in tolerance between flat and slope caught L. carponotatus individuals, indicating that this species does not form physiologically distinct subpopulations between these reef zones. The third study (chapter four) experimentally quantified the effect of hypercarbia (3000 μatm) and hypoxia (50% air saturation) on gut carbonate production by the European flounder (Platichthys flesus). Both hypercarbia and hypoxia resulted in a significant increase in carbonate excretion rate (1.5-fold and 2.4-fold, respectively) and acted synergistically when combined. In the final study (chapter five), gut carbonate production was measured in the European flounder undergoing conditions simulating the ‘calcite seas’ of the Cretaceous. The results of this study support the hypothesis that ocean conditions prevalent during the Cretaceous period resulted in piscine carbonate production rates substantially higher (~14-fold) than the present day. Ultimately, this thesis directly links the environmental physiology of fish at the individual level to wider scale implications (past, present and future), ranging from local ecological patterns all the way up to global carbon cycles.

La formation d’un squelette de CaCO3 par les coraux Scléractiniaires est à la base de l’édification des récifs coralliens. Nombre de ces coraux constructeurs de récif vivent en symbiose avec des Dinoflagellés photosynthétiques. Ces deux processus reposent sur le transport et l’utilisation de carbone inorganique (Ci) provenant de l’eau de mer pour la photosynthèse, et du métabolisme animal pour la calcification. Cette thèse s’est intéressée à l’étude moléculaire et physiologique des mécanismes, permettant l’utilisation de ce carbone inorganique.Malgré l’importance des transports de HCO3-, aucun transporteur n’a été caractérisé à cejour et leur implication dans la physiologie des coraux n’est que suggérée par la pharmacologie. Durant cette thèse nous avons cloné un gène codant pour un transporteur deHCO3- chez le corail Acropora sp. La conversion de ce HCO3- en CO2 pour la photosynthèse est facilitée par l’acidification de l’environnement proche du Dinoflagellé dans la cellule animale. Cette acidification est causée par une H+-ATPase de type P que nous avons caractérisée. Ce gène est le premier à montrer une expression dépendante de la vie en symbiose chez le symbiote.Nous avons aussi cloné et localisé deux anhydrases carboniques (AC). L’une impliquée dans la calcification et l’autre dans la régulation du pH intracellulaire et l’équilibre entre leCO2 et HCO3-. Une étude pharmacologique de ces deux AC, a identifié des molécules inhibitrices et activatrices qui ont permis des expériences de physiologie in vivo. Celles-ci permettent une analyse plus discriminante du rôle des AC dans la calcification. / Coral reefs edification is based on the formation of a calcium carbonate skeleton byscleractinian corals. Many of these reef-building corals establish a symbiotic association with photosynthetic Dinoflagellates. Both processes involve the transport and utilization of inorganic carbon (Ci) coming from seawater for photosynthesis, and from animal metabolismfor calcification. This work focused on the molecular and physiological study of poorlyknown mechanisms that allow the utilization of Ci.Despite the importance of bicarbonate transport, no transporter has been characterized and their role in coral physiology is only suggested by pharmacological experiments. We have cloned a gene encoding a bicarbonate transporter in the coral Acropora sp. The conversion of this bicarbonate into CO2 for photosynthesis is mediated by the acidification of the are asurrounding the Dinoflagellate in the animal cell. This is performed by a P type H+-ATPasethat we characterized here. This is the first gene with a symbiosis-dependent expression in the symbiont.This work also allowed the cloning and the localization of two carbonic anhydrases (CA).The first one is involved in calcification, the second one plays a role in the intracellular pHregulation and the CO2 / HCO3- equilibrium. A pharmacological study of these two enzymes identified inhibitor and activator compounds that have been then used in physiology experiments. This last approach represents a more accurate study of the role of CAs incalcification.

<p>Modern microbialites and microbial mats are the focus of ongoing research as they provide an opportunity to understand microbial-mineral interactions during carbonate precipitation and the generation of biosignatures that can inform our interpretation of the geological record. This study determined the natural abundance isotopic compositions ([13]C, [14]C) of the primary carbon pools and microbial communities associated with modern freshwater microbialites located in Pavilion Lake and in carbonate rich microbial mats on the nearby Cariboo Plateau in British Columbia, Canada. </p> <p> Natural abundance [14]C analysis of carbon pools associated with the Pavilion Lake microbialites demonstrated that structures were actively growing and that groundwater carbon inputs to the lake and microbialites were minimal. Rather, ambient dissolved inorganic carbon (DIC) was the primary carbon source for both microbial communities and recent carbonate. </p> <p> Isotopic enrichment of calcium carbonate within microbial communities associated with the microbialites was identified as a biosignature of microbial photosynthetic influence driving precipitation. Elevated oxygen concentrations and pH within the microenvironment of small, sporadic nodular microbial surface communities was concurrent with in situ precipitation of carbonate with δ[13]C values higher than predicted abiotic values and δ[13]C of bulk organic matter and phospholipid fatty acids (PLFA) that were consistent with a photosynthetically dominated community. Elevated carbonate δ[13]C values were also noted in the thin surface microbial mat recovered from shallow (11m) microbialites. These samples showed increased biomass during summer sampling periods as compared to deeper samples, consistent with expected high rates of photosynthetic activity due to higher light levels and temperature at these depths. These results contrast other recent studies of modern microbialite systems that identified biosignatures of heterotrophic influences on precipitation of carbonates. PLFA profiles demonstrated that the surface microbial mat community consisting of both photosynthetic and heterotrophic microbes was stable over seasonal and spatial changes in light and temperature. However, changes in microbial biomass with depth and season indicated that microbial activity and growth plays an important role in the development of isotopic biosignatures. </p> <p> Biosignatures of high levels of photosynthetic activity were also observed in carbonate, rich microbial mats that exhibited undersaturated p CO2 concentrations during the summer and DIC δ[13]C values enriched above values predicted for isotopic equilibrium with atmospheric CO2. Seasonal and annual shifts in the balance of heterotrophy and autotrophy in the lakes and microenvironment of the mat accounted for observed variations in DIC and associated carbonate δ[13]C values. In contrast to other organic rich microbial mats, bulk organic δ[13]C values were not enriched and the systems did not show evidence of CO2 limitation. Rather, these results indicated that low bulk organic δ[13]C values and large isotopic discriminations can exist under conditions of high DIC concentrations and carbonate content that provide a non limiting carbon source to replenish photosynthetic drawdown. </p> / Thesis / Doctor of Philosophy (PhD)

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