<p>Semi-analytical models for remote sensing of water quality parameters need to be parameterized with specific inherent optical properties. In this thesis, data on specific inherent optical properties of Swedish lakes and coastal waters is presented. Also, the problems of measuring in situ spectral backscattering are addressed. It is shown how measured specific inherent optical properties are used to parameterize semi-analytical bio-optical models. The models are then used to produce large synthetic data sets based on the distribution of water quality parameters, and from these data sets, band ratio or single band ratio algorithms for remote estimation of water quality parameters are constructed. A similar model was also used to calculate under water PAR from measured water quality parameters.</p><p>The specific inherent optical properties of Swedish lakes and coastal waters are very similar to earlier reported data from the oceanic environment. However, different relations of the water quality parameters will affect the inherent optical properties absorption and backscattering. The absorption spectra are dominated by yellow substance with terrestrial origin. Phytoplankton absorption is low, and account in general only for about 10 % of the total absorption in regions where phytoplankton pigments are active. The spectral backscattering is dominated by suspended particulate inorganic matter. Phytoplankton backscattering is almost negligible, except in cases where the phytoplankton community is dominated by highly scattering cyanobacteria. Experiences from remote sensing campaigns and modeling shows that remote chlorophyll estimation is most effective at longer wavelengths, where the absorption of yellow substance is low. However, modeling also predicts that large uncertainties have to be expected in the estimation of chlorophyll, both from variation in the specific phytoplankton absorption and from influences of other optically active water quality parameters.</p>

Semi-analytical models for remote sensing of water quality parameters need to be parameterized with specific inherent optical properties. In this thesis, data on specific inherent optical properties of Swedish lakes and coastal waters is presented. Also, the problems of measuring in situ spectral backscattering are addressed. It is shown how measured specific inherent optical properties are used to parameterize semi-analytical bio-optical models. The models are then used to produce large synthetic data sets based on the distribution of water quality parameters, and from these data sets, band ratio or single band ratio algorithms for remote estimation of water quality parameters are constructed. A similar model was also used to calculate under water PAR from measured water quality parameters. The specific inherent optical properties of Swedish lakes and coastal waters are very similar to earlier reported data from the oceanic environment. However, different relations of the water quality parameters will affect the inherent optical properties absorption and backscattering. The absorption spectra are dominated by yellow substance with terrestrial origin. Phytoplankton absorption is low, and account in general only for about 10 % of the total absorption in regions where phytoplankton pigments are active. The spectral backscattering is dominated by suspended particulate inorganic matter. Phytoplankton backscattering is almost negligible, except in cases where the phytoplankton community is dominated by highly scattering cyanobacteria. Experiences from remote sensing campaigns and modeling shows that remote chlorophyll estimation is most effective at longer wavelengths, where the absorption of yellow substance is low. However, modeling also predicts that large uncertainties have to be expected in the estimation of chlorophyll, both from variation in the specific phytoplankton absorption and from influences of other optically active water quality parameters.

The Belgian Coastal Zone (BCZ) in the Southern Bight of the North Sea is a highly dynamic and optically complex area. This is due to high non-algal particles (NAP) and coloured dissolved organic matter (CDOM) content which in spring adds together with undesirable blooms of the haptophyte Phaeocystis globosa. There is a need for improving the algorithms for chlorophyll a (chl a) retrieval in these highly turbid waters and for developing algorithms for species detection in order to attempt to create an early warning bloom system. This information will contribute to the knowledge of the extent and magnitude of the P. globosa bloom in Belgian waters. In this study, pure cultures of the main taxa present in the BCZ, diatoms and P. globosa, were combined with field measurements of light absorption of total particles, phytoplankton and dissolved material, pigment determination and phytoplankton counts to address the main objectives. Sampling was performed during 8 cruises covering winter, spring, summer and late summer, and along nearshore-offshore gradients from 2003 to 2006. The area is characterised by a high spatio-temporal variability of IOPs due to the high dynamics of the area in terms of currents, salinity gradients and biological production. During spring the presence of P. globosa modulates the IOPs across all the area, the particle absorption is significantly higher than summer and there is no significant coast-offshore variability for phytoplankton and CDOM. The design of chl a retrieval algorithms assumes negligible absorption of NAP and CDOM in the near infrared (NIR) and the use of a fixed value of specific phytoplankton absorption. It is shown that neglecting the NAP and CDOM absorption in the NIR will have a significant overestimation impact in retrieval of chl a. On the other hand, the specific phytoplankton absorption was found to be highly variable (0.015 „b 0.011 m2 mg chl a-1). Both results will affect directly the retrieved chl a. The spatial variability of CDOM was significant varying between 0.20-1.31 m-1 in the marine area and between 1.81-4.29 m-1 in the Scheldt estuary. CDOM was found to be related to salinity with conservative mixing within the Scheldt estuary and during some seasons in the BCZ, however deviations from conservative mixing suggest other inputs to the CDOM pool. Analyses of the spectral slope of the CDOM absorption curve revealed two main CDOM pools in the area, an allochthonous one delivered by the Scheldt estuary and an autochthonous one associated with the phytoplankton spring bloom decomposition. Algorithms for CDOM retrieval will be affected if the variability in the relation between CDOM and salinity is not taken into account. The optical characterisation of diatoms and P. globosa from the BCZ in pure cultures revealed that the main differences in the phytoplankton absorption spectra were found at 467 and 500 nm corresponding to the absorption of the pigments chlorophyll c3 (chl c3) characteristic of P. globosa and fucoxanthin, respectively. Accordingly, both the absorption at 467 nm and the ratio 500/467 nm were successfully used to discriminate the two taxa in cultures and field samples. This latter indicator was not preserved in the reflectance signal due to degradation of the signal when passing from absorption to reflectance, and thus could not be used for algorithm development. The spectral feature at 467 nm was later used as the basis for the development of a flag-type algorithm to detect chl c3 using either absorption or water-leaving reflectance data. Also, the correlation between the algorithm¡¦s retrieved chl c3 and P. globosa cell number allowed the quantification of the bloom. The main findings of this thesis highlight the importance of the IOPs characterisation for the improvement and development of ocean colour retrieval algorithms in these highly complex waters.

In-water biogeochemical constituents and bio-optical properties of the St-Lawrence Gulf and Estuary were monitored during 5 cruises conducted between 1997-2001 accross different seasons. Measured inherent optical properties (IOPs) included vertical profiles of the absorption and attenuation coefficients and the volume scattering function as well as absorption by particles, non-algal particles, phytoplankton and coloured dissolved organic matter (CDOM). Apparent Optical parameters (AOPs) included vertical profiles of the upwelling radiance and downwelling irradiance. The spectral shape of the major IOPs like absorption by phytoplankton, CDOM and non-algal particles as well as the particulate backscattering were parameterized using conventional models and adaptations of conventional models. Descriptive statistics of each variable in the collected dataset were analysed and compared with previous findings in the literature. The optical coherence of the measurements was verified using a radiative transfer closure approach. A complete set of IOP cross-sections for optically significant biogeochemical variables were generated. The magnitude and the spatial, temporal and spectral variation exhibited by the optically significant inwater biogeochemical constituents as well as the bio-optical parameters was consistent with our current knowledge of the ecosystem. The variation of the bio-optical parameters throughout the seasons was also coherent with our expectations. All the measured and derived parameters were found to vary within the ranges reported in the literature. Evidence was presented wherein the Gulf waters, which are usually considered as case I waters could also behave like case II waters. Moreover, spectral signatures exhibited by the IOPs and AOPs were coherent with the variation detected in the concentrations of the measured (optically significant) constituents. The extracted IOP cross-sections were consistent with the results of similar studies previously performed and could eventually be used in the estimation of the biogeochemical constituent concentrations given the related component IOPs. First-order radiative transfer closure was achieved; this underscored the validity of our experimental dataset based on considerations of higher level, integrative, physics. We argue that the current data collection campaign succeeded as a comprehensive framework for describing the behavior of the St-Lawrence bio-optical provinces within the context of remote sensing objectives. This bio-optical dataset should provide the basis for the development of a rigorous, satellite-based, remote sensing algorithm for the retrieval of near surface chlorophyll, fine-tuned to the local characteristics of the St-Lawrence system.

Algal blooms plague freshwaters across the globe, as increased nutrient loads lead to eutrophication of inland waters and the presence of potentially harmful cyanobacteria. In this context, remote sensing is a valuable approach to monitor water quality over broad temporal and spatial scales. However, there remain several challenges to the accurate retrieval of water quality parameters, and the research in this thesis investigates these in an optically complex lake (Lake Balaton, Hungary). This study found that bulk and specific inherent optical properties [(S)IOPs] showed significant spatial variability over the trophic gradient in Lake Balaton. The relationships between (S)IOPs and biogeochemical parameters differed from those reported in ocean and coastal waters due to the high proportion of particulate inorganic matter (PIM). Furthermore, wind-driven resuspension of mineral sediments attributed a high proportion of total attenuation to particulate scattering and increased the mean refractive index (n̅p) of the particle assemblage. Phytoplankton pigment concentrations [chlorophyll-a (Chl-a) and phycocyanin (PC)] were also accurately retrieved from a times series of satellite data over Lake Balaton using semi-analytical algorithms. Conincident (S)IOP data allowed for investigation of the errors within these algorithms, indicating overestimation of phytoplankton absorption [aph(665)] and underestimation of the Chl-a specific absorption coefficient [a*ph(665)]. Finally, Chl-a concentrations were accurately retrieved in a multiscale remote sensing study using the Normalized Difference Chlorophyll Index (NDCI), indicating hyperspectral data is not necessary to retrieve accurate pigment concentrations but does capture the subtle heterogeneity of phytoplankton spatial distribution. The results of this thesis provide a positive outlook for the future of inland water remote sensing, particularly in light of contemporary satellite instruments with continued or improved radiometric, spectral, spatial and temporal coverage. Furthermore, the value of coincident (S)IOP data is highlighted and contributes towards the improvement of remote sensing pigment retrieval in optically complex waters.

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No. of bitstreams: 1 andrade_cp_me_prud.pdf: 3003528 bytes, checksum: 19259069721e1c717d15aa96a145d1fb (MD5) Previous issue date: 2018-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente estudo objetivou estimar as concentrações de clorofila-a (Chl-a) no reservatório da usina hidroelétrica de Ibitinga (RHI), localizado no Rio Tietê, estado de São Paulo, Brasil, por meio de coeficientes de absorção obtidos via algoritmos quase-analíticos (QAAs). Para isso, realizou-se uma caracterização bio-ótica e biogeoquímica do RHI, por meio de dados espectrais e de qualidade da água coletados em dois trabalhos de campo, conduzidos em Julho de 2016 e Junho de 2017. Os desempenhos das versões originais QAAV5 e QAAV6 em estimar as propriedades óticas inerentes (POIs) no RHI foram avaliados. Versões re-parametrizadas para dois reservatórios localizados no sistema em cascata do Rio Tietê, QAABBHR e QAAOMW, foram também testadas para a área de estudo. Além disso, foram avaliadas as performances de esquemas compostos pelas versões do QAA já mencionadas, seguidas por quatro modelos para estimativa de Chl-a, os quais utilizam coeficientes de absorção como dados de entrada. A distribuição espacial das concentrações de Chl-a foi analisada por meio da aplicação desses esquemas em uma imagem do sensor Ocean and Land Colour Instrument (OLCI) instalado a bordo do satélite Sentinel-3A, com aquisição coincidente com o segundo trabalho de campo realizado na área de estudo. A caracterização bio-ótica demonstrou variabilidade espacial e temporal dos constituintes oticamente significativos (COSs) no RHI, com predominância da absorção pelo material orgânico colorido dissolvido (CDOM). As versões do QAA testadas para o primeiro conjunto de dados não se mostraram completamente adequadas na obtenção de coeficientes de absorção em todos os comprimentos de onda. Com relação aos esquemas para estimativa de concentração de Chl-a, apenas aqueles baseados no QAAV5 foram capazes de obter resultados razoáveis - Raiz do Erro Médio Quadrático Normalizado (REMQN) < 47.50 % - para os dados da imagem OLCI. Todos os quatro modelos para estimativa de Chl-a testados apresentaram resultados similares para os dados de saída do QAAV5. Esses resultados enfatizam o desafio gerado pela grande variabilidade ótica dos sistemas em cascata, com relação à modelagem bio-óptica. Os resultados obtidos dão suporte a futuros trabalhos, os quais podem resultar em aplicações como o monitoramento do estado trófico na área de estudo a partir de dados de satélite, com maior acurácia proveniente do uso de modelos que possam estimar consistentemente suas POIs. / This research was aimed at retrieving chlorophyll-a (Chl-a) concentrations in Ibitinga Hydroelectric Reservoir (IHR), located at Tietê River, São Paulo State, Brazil, using absorption coefficients obtained via Quasi-analytical algorithms (QAAs). For this purpose, a bio-optical and bio-geochemical characterization of IHR was carried out, through spectral and water quality data collected in two field campaigns conducted in July, 2016 and June, 2017. The suitability of two QAA native forms (QAAV5 and QAAV6) in retrieving inherent optical properties (IOPs) in IHR was assessed. Versions re-parameterized for two reservoirs also located in the Tietê River cascading system, QAABBHR and QAAOMW, were also tested for the study area. Besides that, the performances of schemes composed by the QAA versions already mentioned followed by four models that use absorption coefficients as inputs for estimating Chl-a concentration in Ibitinga Reservoir were evaluated. Spatial distribution of Chl-a in the reservoir was analyzed, since these schemes were applied in an image of the Ocean and Land Colour Instrument (OLCI) sensor onboard Sentinel-3A satellite, with acquisition date coincident with the second field campaign. The bio-optical characterization showed spatial and temporal variability of optically significant constituent (OSC) in IHR and colored dissolved organic matter (CDOM) predominance in its absorption budget. None of the QAA versions tested for the first dataset was completely satisfactory in retrieving absorption coefficients for IHR in all wavelengths. Regarding the schemes for Chl-a concentration estimates, only the ones based on QAAV5 were able to obtain reasonable results - Normalized Root Mean Square Error (nRMSE) < 47.50 % - for the OLCI image data. All four models for Chl-a estimation tested presented similar results for QAAV5 outputs. These results highlight the challenge of copying with high optical variability in cascading systems. The results obtained support further works, which can, prospectively, lead to many practical applications, as monitoring of trophic state in the study area from satellite data, with higher accuracy provided by the use of models that can consistently retrieve the IOPs for this specific water system. / FAPESP: 2012/19821-1 e 2015/21586-9

Indiana University-Purdue University Indianapolis (IUPUI) / Cyanobacterial blooms are currently one of the most important issues faced by environmental agencies, water authorities and public health organizations. Remote sensing provides an advanced approach to monitor cyanobacteria by detecting and quantifying chlorophyll-a (Chl-a) and phycocaynin (PC). In this thesis, an analytical bio-optical model, more typically applied to ocean waters, was modified to accommodate the complexity of inland waters. The newly developed models work well to estimate inherent optical properties, including absorption and backscattering coefficients, in eight different study sites distributed around the globe. Based on derived absorption coefficients, Chl-a and PC concentrations were accurately retrieved for data sets collected annually from 2006 to 2010, and the estimation accuracy exceeded that of currently used algorithms. An important advantage of the model is that low concentrations of Chl-a and PC can be predicted more accurately, enabling early warning of cyanobacterial blooms. In addition, the results also indicated good spatial and temporal transferability of the algorithms, since no specific calibration procedures were required for data sets collected in a different sites and seasons. The compatibility of the newly developed algorithm with MERIS spectra provides the possibility for routine surveillance of cyanobacterial growth in inland waters.

Ocean optical studies have been conducted extensively in open ocean waters but less so in coastal waters where the influence of human population is increasing dramatically. The waters of the Strait of Georgia, British Columbia, Canada, are very important to the rearing of young salmon and herring, and to the fishing industry of British Columbia overall. The oceanography and plankton communities of the Strait have been researched extensively, however the forces behind the frequent occurrence of phytoplankton blooms in these waters still causes debate among researchers. In order to shed some light onto this topic and increase our knowledge of the characteristics of the waters of the Strait of Georgia, optical and bio-physical data were measured in the euphotic waters of the Strait in late spring and early summer of 2006. Hyperspectral optical data were measured for the first time in these waters using in situ optical profilers to collect inherent optical properties and radiometric quantities that were later used to derive apparent optical properties. The inherent optical properties included absorption coefficient, spectral beam attenuation coefficient, chromophoric dissolved organic matter absorption coefficient, particulate absorption coefficient, and particulate scattering coefficient. In situ irradiances and radiances were used to derive various diffuse attenuation coefficients. Water masses in the euphotic zone of the Strait of Georgia were then classified into three optical water masses according to their inherent optical properties using a clustering algorithm. OM1 waters were characterized by high and spectrally-invariant particulate scattering due to inorganic particles carried by the Fraser River plume. Absorption and scattering showed some spectral dependence in OM2 waters, with particles and chromophoric dissolved organic matter contributing equally to light absorption. The deepest waters, OM3, were the least influenced by the Fraser River, and the contribution of chromophoric dissolved organic matter to absorption was greater than in OM1 and OM2. A radiative transfer model, Hydrolight, was used to model some of the optical properties that were not collected in situ and then used to assess the magnitude of light available to phytoplankton in the Strait. Based on the minimum light requirements for photosynthesis of two of the main phytoplankton species in the Strait, the analysis presented here showed that there was enough light available for photosynthesis in the photosynthetically-available radiation range for the two phytoplankton species in all three optical water masses.

The Belgian Coastal Zone (BCZ) in the Southern Bight of the North Sea is a highly dynamic and optically complex area. This is due to high non-algal particles (NAP) and coloured dissolved organic matter (CDOM) content which in spring adds together with undesirable blooms of the haptophyte Phaeocystis globosa. There is a need for improving the algorithms for chlorophyll a (chl a) retrieval in these highly turbid waters and for developing algorithms for species detection in order to attempt to create an early warning bloom system. This information will contribute to the knowledge of the extent and magnitude of the P. globosa bloom in Belgian waters. In this study, pure cultures of the main taxa present in the BCZ, diatoms and P. globosa, were combined with field measurements of light absorption of total particles, phytoplankton and dissolved material, pigment determination and phytoplankton counts to address the main objectives. Sampling was performed during 8 cruises covering winter, spring, summer and late summer, and along nearshore-offshore gradients from 2003 to 2006. <p>The area is characterised by a high spatio-temporal variability of IOPs due to the high dynamics of the area in terms of currents, salinity gradients and biological production. During spring the presence of P. globosa modulates the IOPs across all the area, the particle absorption is significantly higher than summer and there is no significant coast-offshore variability for phytoplankton and CDOM. <p>The design of chl a retrieval algorithms assumes negligible absorption of NAP and CDOM in the near infrared (NIR) and the use of a fixed value of specific phytoplankton absorption. It is shown that neglecting the NAP and CDOM absorption in the NIR will have a significant overestimation impact in retrieval of chl a. On the other hand, the specific phytoplankton absorption was found to be highly variable (0.015 „b 0.011 m2 mg chl a-1). Both results will affect directly the retrieved chl a. The spatial variability of CDOM was significant varying between 0.20-1.31 m-1 in the marine area and between 1.81-4.29 m-1 in the Scheldt estuary. CDOM was found to be related to salinity with conservative mixing within the Scheldt estuary and during some seasons in the BCZ, however deviations from conservative mixing suggest other inputs to the CDOM pool. Analyses of the spectral slope of the CDOM absorption curve revealed two main CDOM pools in the area, an allochthonous one delivered by the Scheldt estuary and an autochthonous one associated with the phytoplankton spring bloom decomposition. Algorithms for CDOM retrieval will be affected if the variability in the relation between CDOM and salinity is not taken into account. <p>The optical characterisation of diatoms and P. globosa from the BCZ in pure cultures revealed that the main differences in the phytoplankton absorption spectra were found at 467 and 500 nm corresponding to the absorption of the pigments chlorophyll c3 (chl c3) characteristic of P. globosa and fucoxanthin, respectively. Accordingly, both the absorption at 467 nm and the ratio 500/467 nm were successfully used to discriminate the two taxa in cultures and field samples. This latter indicator was not preserved in the reflectance signal due to degradation of the signal when passing from absorption to reflectance, and thus could not be used for algorithm development. The spectral feature at 467 nm was later used as the basis for the development of a flag-type algorithm to detect chl c3 using either absorption or water-leaving reflectance data. Also, the correlation between the algorithm¡¦s retrieved chl c3 and P. globosa cell number allowed the quantification of the bloom. The main findings of this thesis highlight the importance of the IOPs characterisation for the improvement and development of ocean colour retrieval algorithms in these highly complex waters.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Tesis por compendio / La presente tesis doctoral, titulada "Contribution to the modelling of the light field distribution within Synechocystis sp. PCC 6803 cultures and its influence on cellular photosynthesis processes", engloba diversos trabajos cuyo objetivo es avanzar en la compresión de la distribución lumínica en cultivos de cianobacterias y en los efectos de la luz sobre los mecanismos fotosintéticos de dichos microorganismos. Se trata, en definitiva, de otro paso hacia la integración de modelos matemáticos sobre la fotosíntesis a nivel celular y a escala de cultivo. En primer lugar, para comprender cómo se comporta un cultivo de bacterias fotosintéticas, es fundamental predecir la distribución del campo de luz a lo largo del perfil del biorreactor, tanto a nivel de intensidad total, como respecto a su distribución de flujo de fotones. La distribución de longitudes de onda presente en el medio es importante puesto que muchos procesos de la fotosíntesis están regulados por ciertas longitudes de onda y, por tanto, están modulados por la distribución espectral - el color - de la luz. Aprovechando las propiedades inherentes ópticas del cultivo, se desarrolló un modelo matemático basado en el concepto de campo auto-consistente. Este algoritmo, bautizado en la correspondiente publicación como Auto-consistent Field Approximation Algorithm (AFA), proporciona una predicción del campo lumínico, incluyendo la evolución espectral del mismo a lo largo del camino óptico, para cultivos aclimatados a distintos valores de radiación. Dicha investigación se publicó en la revista Algal Research mediante el artículo titulado "Light distribution and spectral composition within cultures of micro-algae: Quantitative modelling of the light field in photobioreactors", en el que se valida el algoritmo con datos experimentales de dos cepas de estudio de la cianobacteria Synechocystis. Si bien los resultados fueron satisfactorios, el empleo de la ley de Lambert-Beer con un valor constante de atenuación no permite modelizar la parte del campo de luz con menor intensidad, donde el coeficiente de atenuación deja de ser constante y el comportamiento se desvía del exponencial. Por ello, se decidió modelizar el campo de luz con una función que generaliza el caso exponencial mediante el uso de cálculo fraccionario. Se empleó una función de Mittag-Leffler que cumplía con los requisitos formales y ofrecía un ajuste de los datos mejor al obtenido mediante la ley de Lambert-Beer. Como un hallazgo notable, se determinó que el valor de dicho parámetro, que caracteriza la función de Mittag-Leffler, era el mismo para los datos empíricos de las dos cepas estudiadas. Este trabajo se publicó en la contribución llamada "Estimation of the light field inside photosynthetic microorganism cultures through Mittag-Leffler functions at depleted light conditions" en la revista Journal of Quantitative Spectroscopy & Radiative Transfer. Después se procedió a utilizar sendos trabajos de investigación para calcular el campo de luz en un cultivo de Synechocystis y relacionarlo con su productividad máxima. En concreto se ha estudiado, como indicador del rendimiento de la fotosíntesis, la producción de oxígeno y los mecanismos respiratorios asociados a distintas intensidades de luz. Esta investigación está en su fase final y se está ultimando la escritura del artículo para enviarlo a una revista científica próximamente. Dicho manuscrito se titula "Experimental characterisation of Synechocystis sp. PCC 6803 cultures productivity up on light conditions". Finalmente, se está desarrollando una cuarta contribución titulada "Individual pigment contribution to overall in vivo absorption in Synechocystis sp. PCC 6803 cells". Esta investigación estudia la cantidad de luz absorbida por los cromóforos de Synechocystis en función del tipo de iluminación utilizada y calcula la concentración de pigmentos presentes en la célula. / The present doctoral thesis, entitled "Contribution to the modelling of the light field distribution within Synechocystis sp PCC 6803 cultures and its influence on cellular photosynthesis processes", includes several works whose objective is to advance in the understanding of the light distribution in cyanobacterial cultures and in the effects of light on the photosynthetic mechanisms of these microorganisms. It is, ultimately, another step towards the integration of mathematical models on photosynthesis at the cellular level and at the scale of culture. First, to understand how a culture of photosynthetic bacteria behaves, it is essential to predict the distribution of the light field along the bioreactor profile, both at the level of total intensity and with respect to its photon flux distribution. The distribution of wavelengths present in the medium is important since many processes of photosynthesis are regulated by certain wavelengths and are therefore modulated by the spectral distribution - the colour - of the light. Taking advantage of the inherent optical properties of the culture, a mathematical model based on the self-consistent field concept was developed. This algorithm, named in the corresponding publication as Auto-consistent Field Approximation Algorithm (AFA), provides an estimation of the light field, including the spectral evolution thereof along the optical path-length, for acclimated cultures to different radiation values. This research was published in the journal Algal Research through the article entitled "Light distribution and spectral composition within cultures of micro-algae: Quantitative modelling of the light field in photobioreactors", in which the algorithm is validated with experimental data of two strains of study of the cyanobacterium Synechocystis. Although the results were satisfactory, the use of the Lambert-Beer Law with a constant attenuation value, cannot correctly model the part of the light field with less intensity, where the attenuation coefficient ceases to be constant and the behaviour deviates from the exponential. Therefore, it was decided to model the light field with a function that generalizes the exponential case through the use of fractional calculus. A Mittag-Leffler function was used that fulfilled the formal requirements and offered a better data fit than that obtained with the Lambert-Beer law. As a remarkable finding, it was determined that the value of this parameter, which characterises the Mittag-Leffler function, was the same for the empirical data of both studied strains. This work was published in the contribution called "Estimation of the light field in photosynthetic microorganism cultures through Mittag-Leffler functions at depleted light conditions" in the journal Journal of Quantitative Spectroscopy & Radiative Transfer. Thereafter we proceeded to use both research works to calculate the light field within Synechocystis cultures and relate it to its maximum productivity. Specifically, it has been studied, as an indicator of the performance of photosynthesis, the production of oxygen and the associated respiratory mechanisms under different light intensities. This research is in its final phase and the writing of the article is being finalised to submit it to a scientific journal soon. This manuscript is entitled "Experimental characterization of Synechocystis sp. PCC 6803 cultures productivity up on light conditions". Finally, a fourth contribution entitled "Individual pigment contribution to overall in vivo absorption in Synechocystis sp. PCC 6803 cells" is under development. This research studies the amount of light absorbed by Synechocystis chromophores according to the type of employed illumination and calculates the concentration of pigments present in the cell. / La present tesi doctoral, titulada "Contribution to the modelling of the light field distribution within Synechocystis sp. PCC 6803 cultures and its influence on cellular photosynthesis processes", engloba diversos treballs l'objectiu dels quals és avançar en la compressió de la distribució lumínica en cultius de cianobacteris i en els efectes de la llum sobre els mecanismes fotosintètics d'aquests microorganismes. Llavors, es tracta en definitiva d'un altre pas cap a la integració de models matemàtics sobre la fotosíntesi a nivell cel·lular i a escala de cultiu. En primer lloc, per a comprendre com es comporta un cultiu de bacteris fotosintètics, és fonamental predir la distribució del camp de llum al llarg del perfil del bioreactor, tant a nivell d'intensitat total, com pel que fa a la seua distribució de flux de fotons. La distribució de longituds d'ona present en el medi és important ja que molts processos de la fotosíntesi estan regulats per certes longituds d'ona i, per tant, estan modulats per la distribució espectral - el color - de la llum. Aprofitant les propietats inherents òptiques del cultiu, es va desenvolupar un model matemàtic basat en el concepte de camp auto-consistent. Aquest algoritme, batejat en la corresponent publicació com Auto-consistent Field Approximation Algorithm (AFA), proporciona una predicció del camp lumínic, incloent l'evolució espectral del mateix al llarg del camí òptic, per a cultius aclimatats a diferents valors de radiació. Aquesta investigació es va publicar a la revista Algal Research mitjançant l'article titulat "Light distribution and espectral composition within cultures of micro-algae: Quantitative modelling of the light field in photobioreactors", en què es valida l'algoritme amb dades experimentals de dues soques d'estudi de la cianobacteri Synechocystis. Si bé els resultats van ser satisfactoris, l'ús de la llei de Lambert-Beer amb un valor constant d'atenuació no permet modelitzar la part del camp de llum amb menys intensitat, on el coeficient d'atenuació deixa de ser constant i el comportament es desvia del exponencial. Per això, es va decidir modelitzar el camp de llum amb una funció que generalitza el cas exponencial mitjançant l'ús de càlcul fraccionari. Es va emprar una funció de Mittag-Leffler que complia amb els requisits formals i oferia un ajust de les dades millor a l'obtingut mitjançant la llei de Lambert-Beer. Com una troballa notable, es va determinar que el valor d'aquest paràmetre, que caracteritza la funció de Mittag-Leffler, era el mateix per a les dades empíriques de les dues soques estudiades. Aquest treball es va publicar en la contribució anomenada "Estimation of the light field inside Photosynthetic microorganisme cultures through Mittag-Leffler functions at depleted light conditions" a la revista Journal of Quantitative Spectroscopy & Radiative Transfer. Després, es va procedir a utilitzar sengles treballs d'investigació per calcular el camp de llum en un cultiu de Synechocystis i relacionar-lo amb la seua productivitat màxima. En concret s'ha estudiat, com a indicador del rendiment de la fotosíntesi, la producció d'oxigen i els mecanismes respiratoris associats a diferents intensitats de llum. Aquesta investigació està en la seua fase final i s'està ultimant l'escriptura de l'article per enviar-lo a una revista científica pròximament. Dit manuscrit es titula "Experimental characterisation of Synechocystis sp. PCC 6803 cultures productivity up on light conditions". Finalment, s'està desenvolupant una quarta contribució titulada "Individual pigment contribution to overall in vivo absorption in Synechocystis sp. PCC 6803 cells". Aquesta recerca estudia la quantitat de llum absorbida pels cromòfors de Synechocystis en funció del tipus d'il·luminació utilitzada i calcula la concentració de pigments presents en la cèl·lula. / Fuente Herraiz, D. (2018). Contribution to the modelling of the light field distribution within Synechocystis sp. PCC 6803 cultures and its influence on cellular photosynthesis processes [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/106362 / Compendio