Dissertations / Theses on the topic 'Spring bloom'

The effects of variability in the physical environment on the development of the spring phytoplankton bloom are investigated using a physically forced model of the annual plankton cycle in the ocean mixed layer. The model is optimised to fit survey data from the eastern North Atlantic, collected over a 1500 x 1500 km area between 39N and 54N, from April-June 1991, establishing the feasibility of using spatially distributed point-in-time data in model calibration. Measurements made below the seasonal pycnocline show the existence of an empirical relationship between preformed nitrate and salinity in this area, allowing salinity-based estimates of pre-bloom mixed layer nitrate concentration to be made. These estimates provide important additional constraints for the model. The observed spatio-temporal patterns, at scales between 36 km and 1500 km, in nutrients, chlorophyll and measures of bloom progression derived from these data with reference to pre-bloom nitrate are discussed, together with the corresponding patterns in seasonal stratification. During the spring bloom, when biogeochemical concentrations vary rapidly in response to the developing stratification, absence of data defining its history limits the value of comparison between point-in-time observations and model results. Predictions of variation in stratification at the seasonal time-scale from general circulation models (GCMs) can be used in place of observational data to force ecosystem models. However, the degree to which observations are used to constrain the model solutions should allow for both model error in stratification and misrepresentation of the seasonal development of stratification by the observations. The latter occurs due to sampling error associated with short-term fluctuations. It can be corrected for if a suitable contemporary sea surface temperature data set is available to define the variation of mixed layer temperature at the seasonal time-scale. It is shown that the accuracy of the GCM predictions can be improved by the application of meteorology specific to the year of observation. It is also shown that the sensitivity of the ecosystem model predictions to error in the physical forcing can be reduced by matching model and observations by a stratification measure, rather than by time, when comparing fields. The survey data show an important contribution to the stratification arising from the 'tilting' action of vertical shear on pre-existing horizontal buoyancy gradients in the winter¬ time mixed layer. This effect was severely underestimated by the GCM. The discrepancy can be accounted for by the absence of density fronts and mesoscale dynamics in the model. Ecosystem model results suggest that spatial variance in Zooplankton grazing, due to the effect of differences in the depth and duration of winter-time mixing on the over-wintering success of plankton populations, is one of the major factors controlling the spatial and temporal characteristics of the phytoplankton bloom.

Much of the primary production in northern latitudes is associated with the relatively short spring phytoplankton bloom. Quantifying the bloom is essential to understanding export production and energy transfer to higher trophic levels. This study focuses on the physical forcing controlling the spring bloom in the Irminger Basin (IB), situated between Greenland and Iceland. In situ data are available from four cruises to the region carried out under the UK Marine Productivity programme. This data set is extended with six years of SeaWiFS satellite chlorophyll-a concentration (chl-a) data, together with the corresponding model net heat flux (NCEP reanalysis) and satellite measured wind speed (QuikSCAT), sea surface temperature (SST; AVHRR) and photosynthetically available radiation (PAR; SeaWiFS). The remotely sensed data are complemented by a 1-D vertical mixing model and temperature and salinity profiles from Argo drifting profilers. The seasonality in temperature-nutrient (TN) relationships is investigated and the TN relationships are improved by including chlorophyll in the regressions. Basin-wide, daily estimates of nitrate, phosphate and silicate are made from satellite SST and chl-a. The study focuses on three biogeographical zones determined by cluster and Empirical Orthogonal Function analysis of SeaWiFS chl-a data. The three areas have distinct chl-a signatures and cover the East Greenland shelf, the Reykjanes Ridge and the Central Basin. An ANOVA analysis reveals that significant interannual variability is occurring in chlorophyll-a. An objective method for determining the start day of the spring bloom is described. Interannual variability in the timing of the initiation of the bloom and its magnitude and duration is discussed. The influence of the prevailing meteorology on chl-a in different seasons are investigated using generalized linear modelling. Whilst net heat flux and PAR are the dominating factors in spring, wind speed and SST become increasingly influential during summer and autumn. A method for estimating time series of Sverdrup’s critical depth from remotely sensed PAR and attenuation coefficient data is outlined. It is found that the spring bloom never begins before the mixed layer depth becomes shallower than the critical depth, and there is a delay of ~10 days. Specific criteria for the start of the bloom in terms of net heat flux and PAR are determined. The effect of nutrient depletion on the decline of the bloom is discussed. The East Greenland coastal zone is used as an example of the lasting impact that anomalous meteorological conditions can have on the following spring’s bloom. In 2002 the East Greenland region experienced anomalously low chl-a concentrations. Strong easterly winds, associated with the tip-jet phenomena, occurred throughout winter and spring and net heat flux was anomalously low in 2002. The spring bloom in the Irminger Basin can be affected by large scale climatic events, such as shifts in the North Atlantic Oscillation. Finally, the timing of nutrient depletion and its impact on community succession is considered. The possibility of iron limitation in the basin is discussed. A lower bound estimate of export production is made based on the timing of silica availability, and hence diatom dominance, of the spring bloom. The contributions to export production by diatoms and non-diatoms are estimated.

The primary objective of this masters study is to develop an understanding of the physical processes driving the timing of the spring phytoplankton bloom in Rivers Inlet. The spring bloom is initiated as light limitation is lifted causing an increase in growth which overcomes loses due to grazing and advection. The bloom is terminated by nitrate exhaustion. The physical system can impact the spring bloom through variations of winds, cloud coverage, and river input. Strong winds showed two effects. First, strong winds increased the mixing layer depth which decreased the amount of light available for phytoplankton, thus delaying the timing of the spring bloom. Second, large outflow winds caused flushing events to occur resulting in rapid horizontal advection removing the plankton population from the area. River discharge has two opposite effects on the timing of the spring bloom. High river discharge causes the water column to stratify, reducing the mixing layer depth which provides more light available for growth and results in an earlier bloom. High discharge will also result in higher upwelling advection leading to a larger advective loss term for phytoplankton, delaying the bloom. Changes in cloud coverage will directly affect the incoming solar radiation and the light available for photosynthesis. A coupled bio-physical model is used to explore the driving forces involved in the timing of the spring phytoplankton bloom in Rivers Inlet, British Columbia, Canada. The primary control on the timing of the spring bloom in Rivers Inlet is wind speed and direction. Secondary control on the timing is due to freshwater flow; high river discharge delays the bloom in Rivers Inlet. Single outflow wind events can result in a 7 day delay in the bloom timing. The shift in bloom timing resulting from multiple outflow wind events is greater than the sum of the individual wind events. Implications of flushing events in fjords along the British Columbia coastline are also discussed.

The influence of sea ice seeding on the northern Baltic Sea´s pelagic phytoplankton spring bloom was studied in a laboratory experiment in which microcosms mimicked sea conditions. On March 26th, 2018, samples (ice cores and seawater) were taken from land-fast ice at a coastal station in the Gulf of Bothnia. The seeding experiment lasted for 9 days, during which a 12:12 hours light:dark incubation took place. Four different treatments (two with ice and two without it) were set up in twelve incubated microcosms. Samples for analyses were taken on days 0, 3, 6 and 9. On day 0, measurements were carried out on four melted ice cores and on seawater. On the remaining days analyses were performed on the incubated microcosms. The measured variables were: chlorophyll a, phytoplankton abundance, bacterial abundance, conductivity and nutrients (TDN and TDP). The most abundant algal species were identified in a qualitative analysis. The obtained data were processed to calculate the average and standard deviations and to assess the existence of statistically significant differences among the treatments. A significant increase in chlorophyll a, phytoplankton and heterotrophic bacteria abundances was detected. A parallel decline in the nutrient concentrations was observed. A relationship between phytoplankton´s degree of influence and cell-size is suggested: cells > 3µm were more abundant in ice than in seawater, and the opposite tendency was appreciated for cells < 3 µm. My study shows that sea ice seeding can have a marked seeding effect on the size structure of the spring phytoplankton bloom.

Au sein des écosystèmes côtiers, la composition, la distribution et la dynamique phytoplanctoniques sont influencées par les variations spatio-temporelles des structures hydrologiques et des para mètres biogéochimiques, sous les pressions naturelles et anthropiques. Les suivis de référence, de par leur faible résolution spatiale et temporelle, peuvent manquer des événements-clés comme l'initiation ou la fin des efflorescences ou nuisibles (du type Harmful Algal Blooms). Pour permettre leur détection et mieux comprendre la distribution et la dynamique de ce compartiment à la base des réseaux trophiques et acteur majeur des cycles biogéochimiques, l'utilisation d'approches automatisées à haute fréquence permet de compléter les approches taxonomiques par la caractérisation fonctionnelle de l'ensemble du spectre de taille du phytoplancton. Cette thèse est consacrée à l'étude des caractéristiques morphologiques et physiologiques des groupes fonctionnels phytoplanctoniques définis à partir de leurs propriétés optiques à l'échelle de l'individu, rencontrés dans des mers épi-et intracontinentales contrastées en utilisant la cytométrie en flux automatisée de type "pulse-shape-recording". Tout d'abord, la distribution des groupes phytoplanctoniques et de leurs traits ont été explorés en Manche occidentale et centrale lors de la transition été-automne, ce qui a permis de mettre en évidence la formation de patches d'abondance et de biomasse à proximité du front d'Ouessant et une structuration à sub-mésoéchelle. En deuxième lieu, la dynamique des groupes fonctionnels phytoplanctoniques en Manche orientale et sud Mer du Nord a été étudiée pendant la période de développement des blooms printaniers de diatomées et de Phaeocystis globosa, avec l'utilisation de la LCBD et de la SCBD permettant l'observation de ségrégation spatiale entre groupes phytoplanctoniques dont leur distribution est expliquées par les paramètres de niche (marginalité et tolérance). Enfin, l'étude des paramètres conditionnant la distribution spatiale verticale le long d'un gradient de salinité en Mer Baltique a été abordée pendant la période estivale, en relation avec les propriétés biogéochimiques des masses d'eaux, qui a permis d'identifier les caractéristiques des groupes phytoplanctoniques participant à la distribution des groupes phytoplanctoniques. Les variations des traits ressortent comme étant les meilleurs prédicteurs de la distribution horizontale et verticale vis-à-vis des paramètres de niche et des descripteurs spatiaux (dispersion, paramètres physiques et biologiques). L'approche par traits fonctionnels, dérivés des mesures optiques à haute résolution, couplée à l'analyse de niche permettent d'avancer dans la compréhension des réponses des communautés aux gradients environnementaux, elles-mêmes détectées par les mesures d'indices de diversité. Ce travail a bénéficié de l'appui des projets régionaux (CPER MARCO), nationaux (convention MTES-CNRS) et européens (JERICO-NEXT)
In coastal ecosystems, phytoplankton composition, distribution and dynamics are strongly influenced by spatial and temporal variations of hydrological structures and biogeochemical parameters, consequences of natural and anthropogenic pressures. Reference monitoring, due to its low spatial and temporal resolution, may fail to detect key events as the initiation and end of phytoplankton outbursts or harmful algal blooms (HABs). By increasing the spatial and/or temporal resolution as well as completing taxonomical counting by investigating the phytoplankton whole size spectra, the use of automated sensors may allow contributing to a better understanding of the distribution and dynamics of this major player in biogeochemichal cycles, at the basis of most foof webs. This thesis consists in studying the characteristics of phytoplankton functional groups defined from their optical properties at the single-cell level, in relation to spatio-temporal variability encountered in contrasting marginal seas, applying the pulse shape-recording automated flow cytometry. This functional classification reflects the diversity of particles according to morphological and physiological properties. First of all, the distribution of phytoplankton groups and their traits where explored in the Western and Central English Channel during the summer period. Most groups formed patches of abundance and biomass near the Ushant front and were structured at the sub-mesoscale. Secondly, phytoplankton functional groups dynamics was characterized in the Eastern English Channel and Southern North Sea during the development period of diatoms and Phaeocystis globosa spring groups, by calculating LCBD and SCBD, wich allowed the observation of spatial segregation between phytoplankton groups. Their distribution was explained by the niche parameters (marginality and tolerance). Finally, the vertical distribution of phytoplankton functional groups in a salinity gradient was addressed in the Baltic Sea, in relation to the biogeochemical properties of the water masses and the characteristics of each PFGs. The variations of the traits are thus stand out as the best predictors of the horizontal and vertical distribution of phytoplankton groups with the respect to niche parameters and spatial descriptors (dispersion, physical and biological parameters). The functional approach, derived from phytoplankton optical properties addressed by automated flow cytometry, coupled to the niche analysis, make it possible to better explain and predict community responses to environmental gradients, such responses being detected in parallel by diversity indices. This work benefited from the support of local (MARCO State-Region Plan Contract), national (CNRS-MTES convention) and international European H2020 JERICO-NEXT projects

Highly-trained athletes are accustomed to varied and high-volume based exercise stimuli and eliciting adaptation in individuals already possessing the necessary physiology to compete at the highest level is difficult. Therefore, identifying novel, potent and time efficient methods of achieving cumulative training stress is a continual quest for coaches and exercise scientists. This thesis examined the acute and chronic effects of manipulating exercise and recovery during brief all-out sprint cycling on adaptive responses favouring enhanced endurance capacity. Chapter 3 highlighted that low-volume non-work matched all-out sprint cycling, whether it be interval- (4 x 30 s bouts) or continuous based (1 x 2 min bout) provides a similarly potent stimulus for the acute induction of cell signalling pathways and key growth factors associated with mitochondrial biogenesis and angiogenesis in trained individuals. In line with manipulating recovery and in attempting to identify a novel and potent exercise intervention capable of giving athletes more return on their training investment, Chapters 4-6 investigated the efficacy of combining sprint interval training with post-exercise blood flow restriction (BFR). Firstly, it was demonstrated that BFR potentiates HIF-1α mRNA expression in response to SIT, tentatively suggesting an enhanced stimulus for hypoxia- and/or metabolic-mediated cell signalling associated with mitochondrial biogenesis and angiogenesis over SIT alone. Secondly, four weeks of SIT combined with post-exercise BFR provides a greater training stimulus over SIT alone in trained individuals to enhance VO2max (4.7 v 1.1 % change) and MAP (3.8 v 0.2 % change), but not 15-km TT performance. Finally, in response to four weeks of SIT combined with post-exercise BFR, an international female track sprint cyclist increased her CP and W by 7 and 2 % and VO2max and absolute MAP by 3 and 4 %, respectively. Through a combination of an acute in vivo molecular experiment, a training study and an athlete case study, this thesis has introduced a potentially potent and novel training concept that appears capable of augmenting aerobic capacity.

This study examined the effects of 14 days of L-carnitine supplementation on blood and muscle lactate concentrations, and carnitine fractions, during high intensity sprint cycling exercise. Eight subjects performed three experimental trials - control I (CON I, 0 days), control II (CON II, 14 days), and L-carnitine (LCN, 28 days). Each trial consisted of a 4 min ride at 90% VO2max, followed by a rest period of 20 min, and then 5 x 1 min rides at 115% VO2max (2 min restbetween each). Following CON II, all subjects began dietary supplementation of L-carnitine for a period of 14 days (4 g/day). L-carnitine supplementation had no significant effect on either muscle carnitine or lactate concentrations following the 4 min 90% ride. Plasma total acid soluable and free carnitine concentrations were significantly higher at all time points following supplementation. Differences observed in blood hydrogen ion and lactate concentrations between CON I and CON II appear to be the result of an order effect. The data from the present investigation indicate that L-carnitine supplementation has no significant effect on blood or muscle lactate accumulation following high intensity sprint cycling exercise.
School of Physical Education

Persistent organic pollutants (POPs) are hydrophobic substances that readily sorb to organic matter in particles and colloids instead of being freely dissolved in the water phase. This sorption affects the bio­availability and environmental transport of the POPs. The major part of this thesis concerns the role of sediments as secondary sources of POPs. As the primary emissions decrease, contaminated sediments where POPs have accumulated can become the main source of contamination. If the contaminated sediment by time becomes covered with cleaner layers, the POPs are buried and no longer in contact with the aquatic environment. Experiments in this thesis showed, however, that new invading species can alter the sediment-water dynamics as a result of their bioturbation, i.e. mixing of sediment particles and pore-water. Marenzelleria spp., invading species in the Baltic Sea that burrow deeper than native species, were found to increase the remobilization of buried contaminants. The sediment-to-water flux was inversely related to the burial depth (2-10 cm) of the POP congeners (polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers) and also inversely related to the hydrophobicity of the congener. The flux was therefore most pronounced for less hydrophobic contaminants, which was linked to the bioirrigating behaviour of these species. Marenzelleria spp. also accumulated the buried POPs and increased concentrations in surface sedi­ment. Contaminants previously considered buried at a ’safe’ depth can thus be remobilized as a result of the invasion of Marenzelleria spp. in the Baltic Sea. One method to decrease the remobilization of contaminants from sediments is ’capping’, i.e. a layer of clean material is placed as a cap on the sediment. By amending the cap with active materials, which sequester the POPs and decrease their availability, thinner layers can be used (’active capping’ or ’thin-layer capping’). Results from an experiment with thin-layer capping using different active materials (activated carbon (AC) and kraft lignin) showed that both the sediment-to-water flux and the bioaccumulation by benthic species of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), hexachlorobenzene (HCB) and octachlorostyrene (OCS) decreased with increased thick­ness of the cap layer (0.5-5 cm). Amendments with active materials further increased the cap efficiency. AC was more efficient than kraft lignin, and a 3 cm cap with 3.3% AC reduced the flux and bioaccumulation with ~90%. The reduction of the sediment-to-water flux was inversely related to the hydrophobicity of the POP, and reductions in the flux had similar magnitudes as reductions in the concentration in deep-burrowing polychaetes, demonstrating the importance of bioturbation for sediment-to-water transport. In a one-year study on the levels of PCDD/Fs, PCBs, and HCB in a coastal area of the Baltic Sea, the correlations between the POP levels and the levels of particles and organic carbon in the water were found to differ for POPs of different structure and hydrophobicity. The levels of PCDD/Fs decreased to one third in May, which could be related to the increased sedimentation, i.e. water-to-sediment transport, during spring bloom.

La présence de bactéries dans le sang, un milieu normalement stérile, peut avoir des conséquences graves voire fatales pour l’organisme atteint. Afin de diagnostiquer au plus tôt cette infection, appelée bactériémie, et ainsi administrer le traitement adéquat, il est nécessaire d’identifier les microorganismes isolés à partir du sang. Mais, la nature complexe de ce fluide biologique, associée à la faible charge bactérienne, parfois inférieure à 1 UFC par millilitre de sang ont des conséquences sur les méthodes pouvant être utilisées pour l’identification des bactéries. La plupart d’entre elles ont donc recours à une première étape, l’hémoculture, au cours de laquelle les microorganismes présents dans le prélèvement sanguin de volume important (20-30 mL) vont se multiplier. Leur croissance est facilitée par la dilution du sang dans des milieux de culture dédiés à cette étape particulière. C’est seulement ensuite que l’identification peut débuter. Elle nécessite encore entre 2 et 48 heures et parfois plus, selon les moyens à disposition et les microorganismes impliqués. Réduire considérablement le temps nécessaire à l’identification aurait pourtant des retombées bénéfiques à l’échelle du patient mais aussi plus globalement en réduisant les coûts associés à cette infection et en limitant la pression de sélection exercée par l’emploi d’antibiotiques à large spectre.Au cours de ce travail, l’évaluation d’une stratégie basée sur l’identification des bactéries lors de leur multiplication dans le milieu d’hémoculture est donc proposée. Elle repose sur l’observation en temps réel et sans marquage par Résonance Plasmonique de Surface par imagerie (SPRi) des interactions entre les bactéries et des ligands déposés à la surface d’un capteur. Dans un premier temps, des ligands alternatifs aux anticorps parmi lesquels figurent les aptamères, des protéines de l’immunité innée et la vancomycine sont testés. Suite à cette étude, les anticorps ont été retenus pour poursuivre ce travail. Leur emploi n’est cependant pas dénué de difficultés lorsqu’il s’agit de détecter spécifiquement Staphylococcus aureus, choisi comme l’un des modèles expérimentaux. En effet, la présence de protéine A chez cette bactérie est à l’origine d’interférences sur les immunoglobulines. Différentes stratégies pour s’affranchir de ces effets ont été évaluées, comme le clivage enzymatique des anticorps ou l’emploi d’anticorps de poule pour lesquels la protéine A n’a pas d’affinité. Ces essais aboutissent à des résultats encourageants en milieu de culture simple. L’ajout de sérum humain au milieu a soulevé de nouveaux problèmes pour la détection de cette bactérie. Les résultats montrent qu’en interagissant avec des constituants de l’échantillon sanguin, dont les anticorps, S. aureus devient indétectable par une biopuce à anticorps. Une discussion des moyens possibles pour lever cette inhibition est ensuite proposée. Des expériences de détection d’une autre bactérie, Salmonella enterica sérovar Enteritidis pour laquelle nous disposons d’un anticorps hautement affin et spécifique ont alors été entreprises afin de conclure sur l’employabilité du dispositif dans des conditions proches d’une hémoculture. Des interférences affectant différentiellement les anticorps selon leur point isoélectrique ont ainsi été mises en évidences et l’implication de l’anticoagulant (polyanéthole sulfonate de sodium, SPS) présent dans les milieux d’hémoculture a été démontrée. La résolution partielle de ce problème a finalement permis la détection de 1 UFC.mL-1 de sang dans 32 mL au total démontrant ainsi la possibilité de détecter spécifiquement une bactérie dans des conditions proches d’une hémoculture
The presence of bacteria in the blood, a normally sterile environment, can cause dramatic consequences for an organism. In order to diagnose this infection, called bacteremia, the identification of the microorganism present in blood must be performed. Furthermore, proper diagnosis enables the administration of a suitable antibiotic therapy. Blood complexity as well as the low bacterial load, usually lower than 1 CFU.mL-1, make the diagnosis of this infection quite challenging. Indeed, most identification methods begin only after the blood culture turns positive due to their insufficient sensitivity. For this they require incubation of a large blood sample volume (20 – 30 mL) in specific culture media that allows bacterial growth above their detection limit. Therefore, its increases considerably the time of diagnosis, which usually takes between 2 and 48 hours and sometimes even more time after blood culture positivity depending on the method and the microorganism present in blood. A reduction of the time required for identification would have a positive impact for both the patient and the healthcare systems by reducing selective pressure on resistant bacteria and hospitalization costs by giving proper treatment faster.In this work, the evaluation of a new strategy based on the identification of bacteria during their multiplication in the blood culture is presented. This method is based on Surface Plasmon Resonance imaging (SPRi) which enables real time and label-free measurements of interactions occurring between bacteria and specific probes. Alternative ligands like aptamers, innate immune proteins and vancomycin have been tested. Following this study antibodies have been chosen as the major specific probes in this work. Nonetheless, the presence of the staphylococcal protein A leads to false-positive results in all immunoglobulin G (IgG). Enzymatic cleavage to remove the constant fragment of antibody where protein A interacts and the use of chicken antibodies (IgY) for which protein A has no affinity have been evaluated. Both methods allow to get rid of protein A interactions in pure culture media. But the presence of human serum in the media results in the total loss of signal. Our results show that interactions between blood components and staphylococcal proteins exposed at the bacterial surface, including the interactions between protein A and circulating antibodies, are responsible for this phenomenon. Solutions to alleviate this inhibition are discussed and tested. Detection experiments of another bacterial model, Salmonella enterica serovar Enteritidis in blood culture media are presented. The crucial role played by the anticoagulant Sodium Polyanethole Sulfonate in non-specific interactions on antibodies is demonstrated. These interactions leading to a total loss of specificity for some antibodies are influenced by the isoelectric point (pI) of the probes which interact with this anionic compound and then attract blood components. After the partial resolution of this issue, we show the feasibility of detecting less than one bacteria per blood milliliter in a total volume of 32 milliliters, conditions close to real blood culture

L’analyse microbiologique pour confirmer l’absence de bactéries dans des échantillons biologiques normalement sains, comme le sang, est une routine dans de nombreux laboratoires. En effet, la présence de bactéries dans le sang, appelée bactériémie, peut avoir des conséquences très graves, voire mortelles pour le patient. Le protocole standard pour la détection des bactériémies repose jusqu’ici sur l’enrichissement des échantillons sanguins prélevés sur les patients lors de l’hémoculture, afin d’obtenir une population suffisante pour analyse. La lenteur de ce procédé retarde ainsi de parfois plusieurs jours le diagnostic et donc l’adaptation du traitement antibiotique administré au patient. Ces dernières décennies, des techniques comme l’identification par spectrométrie de masse ou les analyses moléculaires, ont permis de diminuer le délai requis pour identifier les pathogènes en cause. Dans ce contexte, l’emploi de biocapteurs est également une alternative. Ce travail propose d’inclure des sondes à large spectre dans un capteur optique par imagerie SPR (résonance de plasmons de surface). Ce système est déjà développé pour la reconnaissance spécifique de pathogènes au cours de leur croissance dans le sang. Les nouveaux ligands proposés et évalués sont les peptides antimicrobiens (PAM). Ces courts peptides cationiques et amphiphiles, présentent l’avantage d’un large spectre d’interaction couplé à une haute stabilité (chimique, thermique et séchage) comparativement aux anticorps employés jusqu’ici. Leur immobilisation sur des prismes SPRI permet d’évaluer simultanément l’affinité de plusieurs PAM à la même souche bactérienne. Les biocapteurs ainsi préparés ont permis de détecter des souches pathogènes d’Escherichia coli et Staphylococcus aureus en milieu de culture simple, comme en plasma et en sang dilué au milieu d’hémoculture. Le système obtenu permet la détection des pathogènes présents à une concentration initiale de l’ordre de 1 UFC.ml-1, en moins de 24 heures et quel que soit le milieu. Enfin, la mise en place d’analyses statistiques multidimensionnelles a abouti à une classification cohérente des espèces ciblées en milieu simple, comme en sang. Ces résultats montrent le potentiel de ce système pour parvenir à développer un biocapteur à large spectre capable à la fois de détecter mais aussi d’identifier par affinité croisée des pathogènes bactériens
Microbiological analysis to confirm the absence of bacteria in normally sterile biological samples, such as blood, is routine in many laboratories. The presence of bacteria in blood, called bacteremia, can have very serious, and even fatal consequences for the patient. So far, the standard protocol for their detection has been based on the enrichment of blood samples collected from patients, thanks to blood culture, in order to obtain a sufficient population for analysis. These procedures are time consuming which sometimes lead to delays in diagnosis and subsequent adaptation of antibiotic treatments by several days. In recent decades, techniques such as mass spectrometry identification or molecular analyses have reduced the time required to identify the pathogens involved. In this context, the use of biosensors is another promising alternative. This work proposes to include wide spectrum probes in an optical sensor using SPR imaging (surface plasmon resonance). This system is already developed for the specific recognition of pathogens during their growth in the blood. The new ligands we propose to evaluate are antimicrobial peptides (AMP). These short, cationic and amphiphilic peptides have the advantage of having a broad spectrum of interaction with bacteria, coupled with high stability (chemical, thermal and drying), especially compared to the antibodies used so far in this technique. Their immobilization on SPRI prisms allows the simultaneous evaluation of the affinity of several AMP to the same bacterial strain. The biosensors based on AMP were able to detect pathogenic strains of Escherichia coli and Staphylococcus aureus in simple culture medium, such as plasma and diluted blood in blood culture medium. The system obtained allows the detection of pathogens present at an initial concentration of about 1 CFU.ml-1, in less than 24 hours and in all assayed media. Finally, the implementation of multidimensional statistical analyses has resulted in a consistent classification of targeted species, in simple culture medium, such as blood. These results show the potential of this system to develop a wide-spectrum biosensor capable of both detecting and cross-referencing bacterial pathogens

The timing of the spring phytoplankton bloom in the subpolar North Atlantic Ocean has important consequences for the marine carbon cycle and ecosystems. There are currently several proposed mechanisms to explain the timing of this bloom. The conventional theory holds that the bloom begins when the ocean warms and the seasonal mixed layer shoals in the spring, decreasing the depth to which phytoplankton are mixed and increasing the light available to the population. Recent work has attributed the beginning of the bloom to decreases in turbulence within the upper ocean, driven by the onset of positive heat fluxes or decreases in the strength of local winds. Other studies have focused on the increase in the seasonal mixed layer in the winter as a driver of changes in ecosystem interactions and a control on the spring bloom. Finally, submesoscale eddies, occurring as a result of lateral density gradients, have been proposed as a stratification mechanism that can create phytoplankton blooms prior to the onset of ocean surface warming.

This dissertation critically examines and compares the proposed theories for the initiation of the spring bloom and draws on these theories to propose a new framework: that blooms begin when the active mixing depth shoals, a process generally driven by a weakening of surface heat fluxes and consequent shift from convective mixing to wind-driven mixing. Using surface forcing data, we develop a parameterization for the active mixing depth from estimates of the largest energy-containing eddies in the upper ocean.

Using in situ records of turbulent mixing and biomass, we find that the spring phytoplankton bloom occurs after mixing shifts from being driven by convection to being driven by wind, and that biomass increases as the active mixing depth shoals. Using remote sensing data, we examine patterns of bloom initiation in the North Atlantic at the basin scale, compare current theories of bloom initiation, and find that the shoaling of the active mixing depth better predicts the onset of the bloom across the North Atlantic subpolar basin and over multiple years than do other current theories. Additionally, using a process study model, we evaluate the importance of submesoscale eddy-driven stratification as a control on the initiation of the spring bloom, determining that this mechanism has a relatively minor effect on alleviation of phytoplankton light limitation. Finally, we describe potential techniques and tools to examine whether interannual variability in the active mixing depth acts as a control on variability in the timing of the spring bloom.

Dissertation

Sporadic reports of significant under-ice phytoplankton production indicate a critical knowledge gap of a key component of the Arctic ecosystem. In this thesis I examine the following research objectives in an effort to improve the understanding of under-ice phytoplankton production: (1) to determine the biophysical processes controlling the timing of under-ice phytoplankton production, and (2) to compare and contrast both the timing of the under-ice bloom and the controlling processes between multiple years of data. Data for objective (1) were collected during the three-year Arctic-ICE field campaign (2010-2012) near Resolute Bay, NU in the central Canadian Arctic. Additional data from the region were collected from open source databases and peer-reviewed literature for a dataset that spanned from early 1960 to the present, supporting the analysis to meet objective (2). Two separate under-ice phytoplankton blooms were observed during the three-year Arctic-ICE campaign. It was found that phytoplankton blooms conformed well to the critical depth hypothesis in the Canadian Archipelago under first-year ice, where snow and ice melt both increased light transmission and shoaled the surface mixed layer which, in turn, placed phytoplankton within a favourable light environment for positive net production underneath the ice cover. Factors such as timing of melt water drainage and water column mixing greatly affected bloom onset. From the historical analyses, I was able to show that under-ice phytoplankton blooms have regularly occurred under landfast ice from at least the 1960’s. Significant correlations between the timing of bloom onset with melt onset related variables (i.e., air temperature reaching 0 ºC and complete snow melt) suggested a strong link to climate change. In fact, the ii analysis supported that since the mid 1990s bloom onset has been occurring earlier, and is likely related to decreasing trends in day of complete snow melt, maximum ice thickness, and snow depth. Overall, this thesis has helped improve our understanding of the under-ice spring phytoplankton bloom, showing that under-ice production has been a regular occurrence in the Canadian Arctic. The results also support that timing of the spring phytoplankton blooms could be shifting earlier in response to the warming Arctic and its changing icescape. Such a shift could also have important consequences on the Arctic marine food web, influencing the transfer of energy through the food chain. Therefore, it is of utmost importance to continue future observational programs of the under-ice pelagic environment focussed on the late spring melt period to better understand how the system could change with further perturbations.

abstract: Sea ice algae dominated by diatoms inhabit the brine channels of the Arctic sea ice and serve as the base of the Arctic marine food web in the spring. I studied sea ice diatoms in the bottom 10 cm of first year land-fast sea ice off the coast of Barrow, AK, in spring of 2011, 2012, and 2013. I investigated the variability in the biomass and the community composition of these sea-ice diatoms between bloom phases, as a function of overlying snow depth and over time. The dominant genera were the pennate diatoms Nitzschia, Navicula, Thalassiothrix, and Fragilariopsis with only a minor contribution by centric diatoms. While diatom biomass as estimated by organic carbon changed significantly between early, peak, and declining bloom phases (average of 1.6 mg C L-1, 5.7 mg C L-1, and 1.0 mg C L-1, respectively), the relative ratio of the dominant diatom groups did not change. However, after export, when the diatoms melt out of the ice into the underlying water, diatom biomass dropped by ~73% and the diatom community shifted to one dominated by centric diatoms. I also found that diatom biomass was ~77% lower under high snow cover (>20 cm) compared to low snow cover (<8 cm); however, the ratio of the diatom categories relative to particulate organic carbon (POC) was again unchanged. The diatom biomass was significantly different between the three sampling years (average of 2.4 mg C L-1 in 2011, 1.1 mg C L-1 in 2012, and 5.4 mg C L-1 in 2013, respectively) as was the contribution of all of the dominant genera to POC. I hypothesize the latter to be due to differences in the history of ice sheet formation each year. The temporal variability of these algal communities will influence their availability for pelagic or benthic consumers. Furthermore, in an Arctic that is changing rapidly with earlier sea ice and snowmelt, this time series study will constitute an important baseline for further studies on how the changing Arctic influences the algal community immured in sea ice.
Dissertation/Thesis
Masters Thesis Biology 2014

碩士
國立東華大學
海洋生物研究所
107
In this study, we use an inorganic fertilization method by simulating spring blooms to raise coral reef larvae. We measure the nutrients, in vivo chlorophyll a, water parameters, as well as zooplankton density and diversity, and larval survival during the experimental period. The experiment was performed twice in total. Control tank was without any fertilization (n = 3), the fertilization 1 group was adding inorganic nitrogen, phosphorus and ferrous (N = 700 μg L-1, P = 100 μg L-1, Fe2+ = 100 μg L-1) (n = 3), the fertilization 2 group was adding inorganic nitrogen, phosphorus, ferrous and silicon (N = 700 μg L-1, P = 100 μg L-1, Fe2+ = 100 μg L-1, Si = 1500 μg L-1 ) (n = 3), each group was three replications. Fish eggs were collected from the exhibit tank at the National Museum of Marine Biology and Aquarium, hatched and cultured in 420-L fiberglass tanks (initial density = 2000 eggs tank-1). The results showed that the in vivo chlorophyll a concentrations in the part of the small phytoplankton (< 20 μm) in both experiments, two fertilized groups were significantly higher than control group (P < 0.05). The in vivo chlorophyll a concentrations in the part of the large phytoplankton (> 20 μm), the fertilization 2 group was significantly higher than control group in the experiment 1 (P < 0.05), but two fertilized groups were not significantly different between both fertilized groups (P > 0.05). In the experiment 2, two fertilized groups were significantly higher than control group (P < 0.05). The density in the part of the small zooplankton (48-150 μm), the fertilization 2 group was significantly higher than control group in the experiment 1 (P < 0.05). In the experiment 2, two fertilized groups were significantly higher than control group (P < 0.05). The density in the part of the large zooplankton (> 150 μm), each group was not significantly different with each other in the experiment 1 (P > 0.05). In the experiment 2, two fertilized groups were significantly higher than control group (P < 0.05). The larval survival of the blacktal snapper (Lutjanus fulvus) in two fertilized groups were significantly higher than control group in the two experiments (P < 0.05). The results demonstrated that either of the method of adding inorganic nitrogen, phosphorus and ferrous, and the method of adding inorganic nitrogen, phosphorus, ferrous and silicaon could enhance higher the density of phytoplankton and zooplankton, and the larval survival.

碩士
臺北市立大學
競技運動訓練研究所
104
Purpose: This study compared physiological responses of ergometer kayaking performance in different intensities of critical velocity to reference an index for specialized training. Methods: eight trained male college kayak sprint athlete (age 19.8 years ± 0.51, height 172cm ± 1.69cm, weight 67.25kg ± 1.43kg) trailed maximum oxygen uptake, 200 meters, 500 meters, 1000 meters on kayak ergometer and converted the critical velocity. Blood lactate, hart rate were recorded instantly end of four minutes different percentage intensity of critical velocity ergometer kayaking. result: 1. An acute blood lactate concentration responses were significant difference at end of the different percentage critical velocity exercises (between 80% of CV, 90% of CV and 100% of CV, p <.01, and between 80% of CV, 90% of CV and 110% of CV, p <.01) but no significantly between 100% of CV and 110% of CV. 2. The percentage of maximum heart rate at end of different CV intensities were significant difference between 80% of CV, 90% of CV and 100% of CV (p <.01) and between 80% of CV, 90% of CV and 110% of CV (p <.01) but not between 100% of CV and 110% of CV. 3. A significantly correlation between with VO2max and 110% of CV(r = -0.757, p <.05), and between with1000m time trail and 110% of CV(r = 0.821, p <.05). Conclusion: According to ergometer kayaking, the magnitude of increase in blood lactate concentration and heart rate were regulated in a percentage of critical velocity-dependent manners. A different percentages of critical velocity can be directly corresponds to the intensity on ergometer kayak specialized training.