Cyanobacteria are common inhabitants of freshwater lakes and reservoirs throughout the world. Under favourable conditions, certain cyanobacteria can dominate the phytoplankton within a waterbody and form nuisance blooms. Case reports and anecdotal references dating from 1949 describe a range of illnesses associated with recreational exposure to cyanobacteria: hay fever-like symptoms, pruritic skin rashes and gastro-intestinal symptoms (the latter probably related to ingestion of water) are most frequently reported. Some papers give convincing descriptions of allergic responses to cyanobacteria; others describe more serious acute illnesses, with symptoms such as severe headache, pneumonia, fever, myalgia, vertigo and blistering in the mouth. A U.S. coroner recently found that a teenage boy died as a result of accidentally ingesting a neurotoxic cyanotoxin from a golf course pond; this is the first recorded human fatality attributed to recreational exposure to cyanobacteria. One of the main public health concerns with exposure to freshwater cyanobacteria relates to the understanding that some blooms produce toxins that specifically affect the liver or the central nervous system. The route of exposure for these toxins is oral, from accidental or deliberate ingestion of recreational water, and possibly by inhalation. Cyanobacterial lipopolysaccharides (LPS) are also reported to be putative cutaneous, gastrointestinal, respiratory and pyrogenic toxins. The aims of this project were to enhance the understanding of public health issues relating to recreational exposure to cyanobacteria by conducting epidemiological and laboratory-based toxicology studies. A prospective cohort study of 1,331 recreational water users was conducted at various sites in southern Queensland, the Myall Lakes area of New South Wales, and central Florida. The study design sought to make improvements over previously published epidemiological studies, in that an unexposed group was recruited from cyanobacteria-free waters, cyanobacterial toxins were measured in site water samples, and respondents were asked to rate the severity of reported symptoms. This study has shown an increased likelihood of symptom reporting amongst bathers exposed to high cyanobacterial cell density (measured by total cell surface area) compared to those exposed to low cyanobacteria-affected waters. Mild respiratory symptoms appear to be the predominant symptom category. A clinical dermatology study to examine delayed-contact hypersensitivity reactions to cyanobacterial extracts was conducted. The study groups were 20 patients presenting for diagnostic skin patch testing at the Royal Brisbane Hospital's dermatology outpatient clinic; a convenience sample of 20 individuals was recruited from outside the hospital as a control group. One patient developed unequivocal reactions to several cyanobacteria extracts, with no dose-response pattern seen, indicating that the reactions were allergic in nature. A mouse model of delayed-contact hypersensitivity, the mouse ear swelling test, has demonstrated that the purified toxin cylindrospermopsin, a highly water-soluble compound, is capable of producing cutaneous injury. Encrusting lesions were seen on abdominal skin during the induction phase of these experiments. Delayed-contact hypersensitivity reactions were also demonstrated with this toxin. LPS from two non-axenic cyanobacterial samples - Cylindrospermopsis raciborskii and Microcystis aeruginosa - were extracted and purified. Thermoregulation studies were performed using a mouse model of rectal temperature measurement. Separate groups of mice were injected with these LPS extracts at two dose levels. Thermoregulation studies were also conducted with purified cyanobacterial toxins: microcystin-LR and cylindrospermopsin and anatoxin-a; cyanobacterial LPS samples purified by collaborators in Adelaide were also investigated for thermoregulation potential. These experiments have shown that the LPS extracts are weakly active when compared with responses to much lower doses of Escherichia coli LPS. Cylindrospermopsin also produces hypothermic responses in mice - comparable to pyrexia in larger mammals - although at a later stage than was seen with LPS extracts. Supplementing the experimental observations of the toxicology and immunotoxicology of cyanobacterial LPS are insights gained from beyond the cyanobacteria literature on the mechanisms of toxicity of different LPS structures. Cyanobacterial LPS was initially suggested to be toxic in the 1970s, at a time when lipid A, the active moiety of LPS, was thought to be identical across all Gram-negative bacteria. More recent work raises questions about the attribution of cutaneous and gastrointestinal illness to cyanobacterial LPS, with the understanding that some bacterial lipid A structures are LPS antagonists, LPS is not toxic by the oral route, and LPS is not reported as a toxin in the clinical dermatology literature. Gut-derived lipopolysaccharides, however, exert potent synergistic effects with a variety of xenobiotic hepatotoxins, and the well-known shock-like syndromes associated with severe cylindrospermopsin and microcystin poisoning deserve further scrutiny from the perspective of immunotoxicology.

Cyanobacteria are common inhabitants of freshwater lakes and reservoirs throughout the world. Under favourable conditions, certain cyanobacteria can dominate the phytoplankton within a waterbody and form nuisance blooms. Case reports and anecdotal references dating from 1949 describe a range of illnesses associated with recreational exposure to cyanobacteria: hay fever-like symptoms, pruritic skin rashes and gastro-intestinal symptoms (the latter probably related to ingestion of water) are most frequently reported. Some papers give convincing descriptions of allergic responses to cyanobacteria; others describe more serious acute illnesses, with symptoms such as severe headache, pneumonia, fever, myalgia, vertigo and blistering in the mouth. A U.S. coroner recently found that a teenage boy died as a result of accidentally ingesting a neurotoxic cyanotoxin from a golf course pond; this is the first recorded human fatality attributed to recreational exposure to cyanobacteria. One of the main public health concerns with exposure to freshwater cyanobacteria relates to the understanding that some blooms produce toxins that specifically affect the liver or the central nervous system. The route of exposure for these toxins is oral, from accidental or deliberate ingestion of recreational water, and possibly by inhalation. Cyanobacterial lipopolysaccharides (LPS) are also reported to be putative cutaneous, gastrointestinal, respiratory and pyrogenic toxins. The aims of this project were to enhance the understanding of public health issues relating to recreational exposure to cyanobacteria by conducting epidemiological and laboratory-based toxicology studies. A prospective cohort study of 1,331 recreational water users was conducted at various sites in southern Queensland, the Myall Lakes area of New South Wales, and central Florida. The study design sought to make improvements over previously published epidemiological studies, in that an unexposed group was recruited from cyanobacteria-free waters, cyanobacterial toxins were measured in site water samples, and respondents were asked to rate the severity of reported symptoms. This study has shown an increased likelihood of symptom reporting amongst bathers exposed to high cyanobacterial cell density (measured by total cell surface area) compared to those exposed to low cyanobacteria-affected waters. Mild respiratory symptoms appear to be the predominant symptom category. A clinical dermatology study to examine delayed-contact hypersensitivity reactions to cyanobacterial extracts was conducted. The study groups were 20 patients presenting for diagnostic skin patch testing at the Royal Brisbane Hospital's dermatology outpatient clinic; a convenience sample of 20 individuals was recruited from outside the hospital as a control group. One patient developed unequivocal reactions to several cyanobacteria extracts, with no dose-response pattern seen, indicating that the reactions were allergic in nature. A mouse model of delayed-contact hypersensitivity, the mouse ear swelling test, has demonstrated that the purified toxin cylindrospermopsin, a highly water-soluble compound, is capable of producing cutaneous injury. Encrusting lesions were seen on abdominal skin during the induction phase of these experiments. Delayed-contact hypersensitivity reactions were also demonstrated with this toxin. LPS from two non-axenic cyanobacterial samples - Cylindrospermopsis raciborskii and Microcystis aeruginosa - were extracted and purified. Thermoregulation studies were performed using a mouse model of rectal temperature measurement. Separate groups of mice were injected with these LPS extracts at two dose levels. Thermoregulation studies were also conducted with purified cyanobacterial toxins: microcystin-LR and cylindrospermopsin and anatoxin-a; cyanobacterial LPS samples purified by collaborators in Adelaide were also investigated for thermoregulation potential. These experiments have shown that the LPS extracts are weakly active when compared with responses to much lower doses of Escherichia coli LPS. Cylindrospermopsin also produces hypothermic responses in mice - comparable to pyrexia in larger mammals - although at a later stage than was seen with LPS extracts. Supplementing the experimental observations of the toxicology and immunotoxicology of cyanobacterial LPS are insights gained from beyond the cyanobacteria literature on the mechanisms of toxicity of different LPS structures. Cyanobacterial LPS was initially suggested to be toxic in the 1970s, at a time when lipid A, the active moiety of LPS, was thought to be identical across all Gram-negative bacteria. More recent work raises questions about the attribution of cutaneous and gastrointestinal illness to cyanobacterial LPS, with the understanding that some bacterial lipid A structures are LPS antagonists, LPS is not toxic by the oral route, and LPS is not reported as a toxin in the clinical dermatology literature. Gut-derived lipopolysaccharides, however, exert potent synergistic effects with a variety of xenobiotic hepatotoxins, and the well-known shock-like syndromes associated with severe cylindrospermopsin and microcystin poisoning deserve further scrutiny from the perspective of immunotoxicology.

Cyanobacteria are common inhabitants of freshwater lakes and reservoirs throughout the world. Under favourable conditions, certain cyanobacteria can dominate the phytoplankton within a waterbody and form nuisance blooms. Case reports and anecdotal references dating from 1949 describe a range of illnesses associated with recreational exposure to cyanobacteria: hay fever-like symptoms, pruritic skin rashes and gastro-intestinal symptoms (the latter probably related to ingestion of water) are most frequently reported. Some papers give convincing descriptions of allergic responses to cyanobacteria; others describe more serious acute illnesses, with symptoms such as severe headache, pneumonia, fever, myalgia, vertigo and blistering in the mouth. A U.S. coroner recently found that a teenage boy died as a result of accidentally ingesting a neurotoxic cyanotoxin from a golf course pond; this is the first recorded human fatality attributed to recreational exposure to cyanobacteria. One of the main public health concerns with exposure to freshwater cyanobacteria relates to the understanding that some blooms produce toxins that specifically affect the liver or the central nervous system. The route of exposure for these toxins is oral, from accidental or deliberate ingestion of recreational water, and possibly by inhalation. Cyanobacterial lipopolysaccharides (LPS) are also reported to be putative cutaneous, gastrointestinal, respiratory and pyrogenic toxins. The aims of this project were to enhance the understanding of public health issues relating to recreational exposure to cyanobacteria by conducting epidemiological and laboratory-based toxicology studies. A prospective cohort study of 1,331 recreational water users was conducted at various sites in southern Queensland, the Myall Lakes area of New South Wales, and central Florida. The study design sought to make improvements over previously published epidemiological studies, in that an unexposed group was recruited from cyanobacteria-free waters, cyanobacterial toxins were measured in site water samples, and respondents were asked to rate the severity of reported symptoms. This study has shown an increased likelihood of symptom reporting amongst bathers exposed to high cyanobacterial cell density (measured by total cell surface area) compared to those exposed to low cyanobacteria-affected waters. Mild respiratory symptoms appear to be the predominant symptom category. A clinical dermatology study to examine delayed-contact hypersensitivity reactions to cyanobacterial extracts was conducted. The study groups were 20 patients presenting for diagnostic skin patch testing at the Royal Brisbane Hospital's dermatology outpatient clinic; a convenience sample of 20 individuals was recruited from outside the hospital as a control group. One patient developed unequivocal reactions to several cyanobacteria extracts, with no dose-response pattern seen, indicating that the reactions were allergic in nature. A mouse model of delayed-contact hypersensitivity, the mouse ear swelling test, has demonstrated that the purified toxin cylindrospermopsin, a highly water-soluble compound, is capable of producing cutaneous injury. Encrusting lesions were seen on abdominal skin during the induction phase of these experiments. Delayed-contact hypersensitivity reactions were also demonstrated with this toxin. LPS from two non-axenic cyanobacterial samples - Cylindrospermopsis raciborskii and Microcystis aeruginosa - were extracted and purified. Thermoregulation studies were performed using a mouse model of rectal temperature measurement. Separate groups of mice were injected with these LPS extracts at two dose levels. Thermoregulation studies were also conducted with purified cyanobacterial toxins: microcystin-LR and cylindrospermopsin and anatoxin-a; cyanobacterial LPS samples purified by collaborators in Adelaide were also investigated for thermoregulation potential. These experiments have shown that the LPS extracts are weakly active when compared with responses to much lower doses of Escherichia coli LPS. Cylindrospermopsin also produces hypothermic responses in mice - comparable to pyrexia in larger mammals - although at a later stage than was seen with LPS extracts. Supplementing the experimental observations of the toxicology and immunotoxicology of cyanobacterial LPS are insights gained from beyond the cyanobacteria literature on the mechanisms of toxicity of different LPS structures. Cyanobacterial LPS was initially suggested to be toxic in the 1970s, at a time when lipid A, the active moiety of LPS, was thought to be identical across all Gram-negative bacteria. More recent work raises questions about the attribution of cutaneous and gastrointestinal illness to cyanobacterial LPS, with the understanding that some bacterial lipid A structures are LPS antagonists, LPS is not toxic by the oral route, and LPS is not reported as a toxin in the clinical dermatology literature. Gut-derived lipopolysaccharides, however, exert potent synergistic effects with a variety of xenobiotic hepatotoxins, and the well-known shock-like syndromes associated with severe cylindrospermopsin and microcystin poisoning deserve further scrutiny from the perspective of immunotoxicology.

Cyanobacteria are common inhabitants of freshwater lakes and reservoirs throughout the world. Under favourable conditions, certain cyanobacteria can dominate the phytoplankton within a waterbody and form nuisance blooms. Case reports and anecdotal references dating from 1949 describe a range of illnesses associated with recreational exposure to cyanobacteria: hay fever-like symptoms, pruritic skin rashes and gastro-intestinal symptoms (the latter probably related to ingestion of water) are most frequently reported. Some papers give convincing descriptions of allergic responses to cyanobacteria; others describe more serious acute illnesses, with symptoms such as severe headache, pneumonia, fever, myalgia, vertigo and blistering in the mouth. A U.S. coroner recently found that a teenage boy died as a result of accidentally ingesting a neurotoxic cyanotoxin from a golf course pond; this is the first recorded human fatality attributed to recreational exposure to cyanobacteria. One of the main public health concerns with exposure to freshwater cyanobacteria relates to the understanding that some blooms produce toxins that specifically affect the liver or the central nervous system. The route of exposure for these toxins is oral, from accidental or deliberate ingestion of recreational water, and possibly by inhalation. Cyanobacterial lipopolysaccharides (LPS) are also reported to be putative cutaneous, gastrointestinal, respiratory and pyrogenic toxins. The aims of this project were to enhance the understanding of public health issues relating to recreational exposure to cyanobacteria by conducting epidemiological and laboratory-based toxicology studies. A prospective cohort study of 1,331 recreational water users was conducted at various sites in southern Queensland, the Myall Lakes area of New South Wales, and central Florida. The study design sought to make improvements over previously published epidemiological studies, in that an unexposed group was recruited from cyanobacteria-free waters, cyanobacterial toxins were measured in site water samples, and respondents were asked to rate the severity of reported symptoms. This study has shown an increased likelihood of symptom reporting amongst bathers exposed to high cyanobacterial cell density (measured by total cell surface area) compared to those exposed to low cyanobacteria-affected waters. Mild respiratory symptoms appear to be the predominant symptom category. A clinical dermatology study to examine delayed-contact hypersensitivity reactions to cyanobacterial extracts was conducted. The study groups were 20 patients presenting for diagnostic skin patch testing at the Royal Brisbane Hospital's dermatology outpatient clinic; a convenience sample of 20 individuals was recruited from outside the hospital as a control group. One patient developed unequivocal reactions to several cyanobacteria extracts, with no dose-response pattern seen, indicating that the reactions were allergic in nature. A mouse model of delayed-contact hypersensitivity, the mouse ear swelling test, has demonstrated that the purified toxin cylindrospermopsin, a highly water-soluble compound, is capable of producing cutaneous injury. Encrusting lesions were seen on abdominal skin during the induction phase of these experiments. Delayed-contact hypersensitivity reactions were also demonstrated with this toxin. LPS from two non-axenic cyanobacterial samples - Cylindrospermopsis raciborskii and Microcystis aeruginosa - were extracted and purified. Thermoregulation studies were performed using a mouse model of rectal temperature measurement. Separate groups of mice were injected with these LPS extracts at two dose levels. Thermoregulation studies were also conducted with purified cyanobacterial toxins: microcystin-LR and cylindrospermopsin and anatoxin-a; cyanobacterial LPS samples purified by collaborators in Adelaide were also investigated for thermoregulation potential. These experiments have shown that the LPS extracts are weakly active when compared with responses to much lower doses of Escherichia coli LPS. Cylindrospermopsin also produces hypothermic responses in mice - comparable to pyrexia in larger mammals - although at a later stage than was seen with LPS extracts. Supplementing the experimental observations of the toxicology and immunotoxicology of cyanobacterial LPS are insights gained from beyond the cyanobacteria literature on the mechanisms of toxicity of different LPS structures. Cyanobacterial LPS was initially suggested to be toxic in the 1970s, at a time when lipid A, the active moiety of LPS, was thought to be identical across all Gram-negative bacteria. More recent work raises questions about the attribution of cutaneous and gastrointestinal illness to cyanobacterial LPS, with the understanding that some bacterial lipid A structures are LPS antagonists, LPS is not toxic by the oral route, and LPS is not reported as a toxin in the clinical dermatology literature. Gut-derived lipopolysaccharides, however, exert potent synergistic effects with a variety of xenobiotic hepatotoxins, and the well-known shock-like syndromes associated with severe cylindrospermopsin and microcystin poisoning deserve further scrutiny from the perspective of immunotoxicology.

L’objectif général de cette thèse est d’étudier et d’analyser l’effet du rayonnement UV-C comme méthodealternative aux produits chimiques dans la lutte et le contrôle de la prolifération des micro-organismesphotosynthétiques dans les grottes touristiques. Dans un premier temps, l’effet des UV-C a été analysé surdifférentes souches cavernicoles de micro-algues cultivées au laboratoire. Des analyses à l’échelle moléculaire,cellulaire et à l’échelle du biofilm d’algues ont permis de mettre en évidence un ensemble de dommages causépar l’irradiation aux UV-C (diminution de la viabilité et de l’activité photosynthétique, dégradation desmembranes, décoloration des cellules par destruction des pigments chlorophylliens, fragmentation de l’ADN,diminution de la surface d’occupation des biofilms d’algues cultivés sur support solide). Ceux-ci sont soit directs(réactions de photooxydation) soit indirects (liés à un stress oxydatif important). L’ensemble de ces résultats ontservi à la sélection de différentes durées d’exposition aux UV-C (traduites en doses d’UV-C) efficaces en termesd’éradication et de décoloration des micro-algues. Ces doses d’UV-C ont dans un deuxième temps été testées enconditions réelles sur le site d’étude de la grotte des Moidons (Jura, France). Une étude préalable à ces tests a étémenée afin de comprendre les dynamiques et les facteurs favorisant l’installation et la prolifération des biofilmsde micro-organismes photosynthétiques dans la grotte. L’étude des facteurs environnementaux mesurés àl’échelle du biofilm (quantité de lumière, type de support, localisation dans la grotte) ainsi que ceux mesurés àl’échelle de la cavité (circulation horizontale et verticale des eaux, vitesse des courants d’air, temps d’allumagedes lampes et temps de présence des visiteurs) ont permis de distinguer des zones de colonisation préférentielle.Plusieurs biofilms ont ensuite été sélectionnés pour tester l’efficacité des UV-C. Selon les caractéristiques desbiofilms (intensité de colonisation) et en fonction de leur emplacement dans la grotte (variations des facteurspréalablement déterminés), nous avons pu mettre en évidence une efficacité des UV-C variable dans le temps.Avec l’appui de résultats complémentaires obtenus sur deux souches de champignons et sur plusieurs types dematières picturales, l’ensemble des données collectées au cours de la thèse souligne l’intérêt et l’applicabilité destraitements aux UV-C dans divers contextes de conservation des matériaux du patrimoine / The aim of this thesis is to study and analyze the effect of UV-C radiation as an alternative method tochemicals to combat phototrophic microorganisms’ proliferation in show caves. First, the effect of UV-C wasanalyzed on several cave-dwelling unicellular green algae sub-cultured in laboratory conditions. Analysis at themolecular, cellular and biofilm scale highlighted several damages (decrease of viability and photosyntheticactivity, membrane degradation, chlorophyll bleaching, DNA fragmentation, decrease of the biofilms’ colonizedarea…) both direct (photooxydation reaction) or indirect (oxidative stress). These results helped to selectefficient UV-C exposure times (traduced in UV-C doses) both to eradicate and bleach green micro-algae.Second, these efficient UV-C doses were used to test the efficiency of UV-C treatments on natural phototrophicbiofilms proliferating in the Moidons Cave (Jura, France). Previous study to the UV-C tests was performed tounderstand the dynamics and factors that promote algal proliferation in this cave. Factors measured at the biofilmscale (quantity of light, type of the physical support, localization in the cave…) and at the cavity scale(horizontal and vertical circulation of waters, air currents, illumination time and visitors’ presence time) allowedto distinguish several preferential areas where growth-supporting conditions were present for algal proliferation.Then, several biofilms were selected to test the efficiency of UV-C treatments. According to the characteristicsof the biofilms (colonization intensity) and their localization in the cave (variations of the factors promotingcolonization) UV-C efficiency varied over time. Supplementary results obtained on filamentous fungi andmineral pigments used for prehistoric paintings, emphasize the interest and the applicability

Histidinkinase-Rhodopsine (HKRs) können als besondere Gruppe der Hybrid-Histidinkinasen beschrieben werden, deren N-terminale sensorische Domäne ein mikrobielles Rhodopsin ist. HKR-codierende Sequenzen konnten in den Genomen verschiedener Algen, Pilze und Amoeben gefunden werden doch ihre Aufgaben und Wirkungsweisen sind bisher ungeklärt. Im Rahmen dieser Arbeit wurden die rekombinanten Rhodopsin-Domänen von zwei HKRs mit verschiedenen spektroskopischen Techniken charakterisiert. Sie zeigten mehrere Besonderheiten. Das Rhodopsin-Fragment von Cr-HKR1 aus Chlamydomonas reinhardtii kann durch alternierende kurzwellige und langwellige Belichtung zwischen zwei stabilen Absorptionsformen konvertiert werden: einer Blaulicht-absorbierenden (Rh-Bl) und einer UVA-Licht-absorbierenden Form (Rh-UV). Dies resultiert aus der ungewöhnlichen thermischen Stabilität des Zustandes mit deprotonierter Schiff’scher Base. Das zweite charakterisierte HKR, die Os-HKR-Rhodopsin-Domäne aus der marinen Picoalge Ostreococcus tauri, zeigt eine Dunkelabsorption von 505 nm. Auch Os-HKR ist photochrom und die deprotonierte Spezies kann effizient akkumuliert werden. Diese P400-Absorptionsform ist jedoch nicht völlig stabil sondern es kommt nach Belichtungsende zur langsamen Dunkelzustands-Regeneration. Überraschenderweise konnte die Bindung sowie die transiente Abgabe eines Anions während des Os-HKR-Photozyklus festgestellt werden. Somit beeinflusst nicht nur das Licht, sondern auch das Salz in der Umgebung die Os-HKR-Reaktionen. Aufgrund ihrer photochromen Eigenschaften werden die HKRs als wirksame lichtinduzierte Schalter für die C-terminalen Signaltransduktionsdomänen postuliert. Schwingungsspektroskopische Analysen deckten eine Heterogenität hinsichtlich der im Protein gebundenen Retinal‐Konfiguration sowie die Existenz von zwei parallelen Photozyklen auf. Jeder dieser Photozyklen geht aus einer der beiden Retinal-Isomere hervor. / Histidine kinase rhodopsins (HKRs) can be described as hybrid histidine kinases with a microbial rhodopsin as N-terminal sensory domain. HKR-encoding sequences were found in the genomes of various unicellular organisms such as algae, fungi and amoeba but their mechanistic and physiologic function is unknown. During this work the absorptive properties of the recombinant rhodopsin domains of two HKRs were studied by the usage of different spectroscopic techniques. Both HKRs showed unusual characteristics. The rhodopsin fragment of Cr‐HKR1 from Chlamydomonas reinhardtii can be interconverted between two stable absorbance forms by the alternate application of short‐ and long‐wavelength light: a blue light-absorbing dark form (Rh-Bl) and a UVA light-absorbing form (Rh-UV). This unusual photocycle results from the uncommon thermal stability of the absorbance state with a deprotonated retinal Schiff base. The second studied HKR, the Os‐HKR rhodopsin domain from the marine picoalga Ostreococcus tauri, shows an absorbance maximum at 505 nm in darkness. Likewise Cr‐HKR1 the Os‐HKR is photochromic and the deprotonated form P400 can be efficiently accumulated. But the Os-HKR P400-form is not completely stable. A slow dark state recovery occurs. Surprisingly the dark state absorbance of Os‐HKR was found to be dependent on anion binding in the protein. Furthermore during the photocycle the transient anion release occurs and therefore not only light but also salt impacts the Os-HKR-reactions. Due to their pronounced photochromic properties, the HKRs are postulated to act as effective molecular switches for the C-terminal signal transduction domains in response to the light conditions. Vibrational spectroscopy revealed the heterogeneity with regard to the retinal configuration bound in the HKRs suggesting the existence of two parallel photocycles. Either of these photocycles originates from one of the two retinal isoforms.

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / Previous studies have indicated that blue-green algae may affect runoff, infiltration and erosion at soil surfaces. Using soil plots upon which blue-green algae were grown under an artificial wetting regime, studies were made using simulated rainfall. A 30% clay content Pima soil and a contrasting 8% clay content river-bottom anthony soil were used. Scytonema hoffmanii and Microcoleus vaginatus grew on the pima soil while Schizothrix calcicola developed on the Anthony soil. The results showed that blue-green algal growths significantly reduced the amount of suspended soil material in runoff water as compared with bare soils. Differences in runoff suspended sediments were also related to differences in soil type and simulated rainfall intensity. An analysis of variance of the effects of these 3 factors and their interactions showed that the smaller differences in suspended sediment production on the Anthony soil due to the microvegetation treatment was verified by a highly significant soils-microvegetation interaction, probably because the finer pima soils wash away more easily without stabilizing microvegetation. Also, less vegetation seems to grow on the Anthony soil. Differences in runoff and infiltration volumes and in settleable sediment amounts were not detected.

MESHWR / Department of Hydrology and Water Resources / In South Africa, inland aquaculture is on the increase, especially among the rural communities. Thus aquaculture is able to provide a source of employment and improve rural incomes. This study assessed algae species and their cyanotoxins in small holder production in Vhembe district, Limpopo, South Africa. Thirteen study sites were selected to assess the algae species and their cyanotoxins. The water samples were collected in four quarters and analysed for water temperature, pH, total dissolved solids, Electrical conductivity, phosphates, nitrates, chlorophyll, cyanobacteria, cyanotoxins, metal species and quality of the water in the fish ponds. In the 1st quarter of the year there was variation in Water Temperature (23.7oC-31.4oC), pH (5.5-9.6), EC (3.82-46.8μS/cm), TDS (2.4-45 mg/L), Phosphate (0.0-1.09mgL-1), Nitrates (0.0-1.00mgL-1), Chlorophyll-a (5.8-11.5mg/m-3). In the 2nd quarter there was variation inwater temperature (22.4-25.0oC), pH (6.6-8.8.9), EC (19.23-21.47μS/cm), TDS (12.5-17.9 mg/L), Phosphate (1.64-1.84mgL-1), Nitrates (1.02-1.88mgL-1), Chlorophyll-a (4.6-15.6mg/m-3). In the 3rd quarter there was variation for water temperature (22.9-25.0oC), pH (7.5-9.1), EC (7.91-293.3μS/cm), TDS (11.7-180.9 mg/L), Phosphate (1.10-1.80mgL-1), Nitrates (1.28-1.84mgL-1),Chlorophyll-a (6.8-15.6mg/m-3). In the 4th quarter there was variation forwater temperature (23.5-30.3), pH (7.1-9.3), EC (18.24-623μS/cm), TDS (23.7-136.4 mg/L), Phosphate (1.45-1.99mgL-1), Nitrates (1.43-1.68mgL-1), Chlorophyll-a (6.6-25.9mg/m-3). The metal content of the fish pond water was variable throughout the year but with moderate levels of Al, Cd, Cr, Mn, Fe, Cu, Zn and Ba were found. The metal Fe, exceeded the DWAF guideline values during this first quarter. The presence of Cd in the fish pond water could be attributed to rainfall eroding the earthen embankments of the fish pond. The results of physico-chemical parameters promotes the growth of cyanobacteria in the fish ponds. Flow cam and SEM were used to identify the cyanobacteria species and most cyanobacteria identified are hazard to human health, fish and other aquatic organisms. Molecular technologies were used to identify cyanotoxins and there was no cyanotoxins detected which was concluded that during collection of water samples no cyanobacteria produced toxins. / NRF

En Bretagne, les « marées vertes » sont récurrentes depuis le début des années 70 et occupent une place importante dans le débat public en terme sanitaire, politique et économique. Lors de cette thèse, une large revue bibliographique a été réalisée sur l’export d’azote et une méthodologie innovante a été mise en place afin d’étudier la variabilité spatio-temporelle de l’export de nutriments dans 2 bassins versants à algues vertes à une échelle intra-annuelle et pendant des évènements extrêmes (évènements pluvieux, période touristique de basses eaux,…). Les bassins versants sélectionnés pour les expérimentations de terrain sont l’Ic et le Frémur (Côtes d’Armor). 3 types d’expérimentations ont été réalisées sur ces bassins versants : 1) Des campagnes de prélèvements ponctuels par temps sec et par temps de pluie (32 stations, 27 campagnes) ; 2) des prélèvements automatiques en crue (3 stations, 8 crues) ; et 3) la mesure haute fréquence (2 stations, en continu). Les paramètres hydrologiques et physico-chimiques classiques, les matières en suspension, les spectres UV et toutes les formes de macronutriments (carbone, azote, phosphore) ont été analysés lors de ces expérimentations. Les résultats obtenus confirment pour une part un certain nombre de résultats de la littérature. D’autre part, il met en lumière la relation carbone/nitrates, jusqu’à présent peu étudiée à différentes échelles spatio-temporelles et pendant des évènements pluvieux, qui semble pourtant primordiale dans la compréhension des phénomènes d’export de nitrates à l’échelle de l’année. Enfin, l’analyse de toutes les formes de nutriments révèle l’importance des formes particulaires issues de l’érosion des sols. Ces résultats soulèvent de nombreuses questions de recherche qui mériteraient un approfondissement afin d’améliorer la connaissance des transferts de nutriments dans les bassins versants et prioriser les actions de remédiations. Les perspectives de ce travail sont à la fois scientifiques et pratiques. Au niveau scientifique, les efforts de recherche sur la relation carbone/nitrate et l’identification de la fraction de carbone organique assimilable par les organismes dénitrifiants doivent être poursuivis. De même, l’amélioration des connaissances sur l’export de nutriments en crue passe par l’identification précise des sources de nutriments particulaires pendant les crues printanières. Au niveau pratique, il doit contribuer à l’amélioration des pratiques agricoles, à la reconnaissance de l’intérêt des zones humides naturelles et à l’amélioration des types de traitement utilisés par les stations d’épuration. Les résultats obtenus lors de cette étude devraient notamment être mis en relation avec la dynamique des nutriments observée dans l’estran pendant la période de développement des algues vertes. Enfin, un effort d’amélioration de l’accès à certains type de données sur les bassins versants est nécessaire afin d’améliorer la compréhension des transferts de nutriments. / In Brittany (Western France), "green tides" are recurrent since the early 70s and have an important place in public debate in health, political and economic terms. In this thesis, a wide bibliographic review was performed on the export of nitrogen, and an innovative methodology has been set up to study the spatial and temporal variability of nutrient export in two coastal watersheds on an intra-annual basis and during extreme events (rainfall events, tourist periods of low water, ...). Watersheds selected for the field experiments are Ic and Frémur (Côtes d'Armor). 3 types of experiments were performed on these watersheds: 1) Campaigns of grab samples by dry and wet weather (32 stations, 27 campaigns); 2) automatic sampling during floods (3 stations, 8 floods); and 3) high frequency measurement (2 stations, continuous). Conventional hydrological and physicochemical parameters, suspended solids, UV spectra and all forms of macronutrients (carbon, nitrogen, phosphorus) were analyzed during these experiments. The results confirm in part a number of results of the literature. Furthermore, it highlights the relationship carbon / nitrates far little studied at different spatial and temporal scales and during rainfall events, which however seems to be crucial in understanding of nitrate export. Finally, the analysis of all forms of nutrients reveals the importance of particulate forms from soil erosion. These results raise many research questions that merit further development in order to improve knowledge on nutrient transfers in watersheds and prioritize remediation actions. The prospects of this work are both scientific and practical. At the scientific level, research efforts on the relationship carbon / nitrate and identification of the assimilable fraction of organic carbon by denitrifying organisms must be continued. Similarly, the knowledge on nutrient export must be improved through the precise identification of particulate nutrient sources during the spring floods. On a practical level, it should contribute to the improvement of agricultural practices, the recognition of the interest of natural wetlands and improvement of the types of treatment used by treatment plants. The results obtained in this study should in particular be linked to the dynamics of nutrients in the foreshore observed during the development of green algae. Finally, an effort to improve access to certain types of data on watersheds is needed to improve understanding of nutrient transfers.