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Internal loading of nitrogen (N) and phosphorus (P), reduced N forms, and periodic mixing support cyanobacterial harmful algal blooms (HABs) in shallow, eutrophic Honeoye Lake (New York, USA)Myers, Justin Adam 03 June 2021 (has links)
No description available.
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All models are wrong, but some are useful: Assessing model limitations for use in decision making and future model developmentApostel, Anna Maria January 2021 (has links)
No description available.
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A Mixed Aquatic and Aerial Multi-Robot System for Environmental MonitoringSubramaniyan, Dinesh Kumar January 2020 (has links)
No description available.
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Acceleration of Phosphorus Flux from Anoxic Sediments in a Warming Lake ErieSwan, Zachary January 2021 (has links)
No description available.
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Part I: Micromechanics of dense suspensions: microscopic interactions to macroscopic rheology & Part II: Motion in a stratified fluid: swimmers and anisotropic particlesRishabh More (8436243) 18 April 2022 (has links)
<p><b>Part I: Micromechanics of dense suspensions</b></p><p>Particulate suspensions are ubiquitous in the
industry & nature. Fresh concrete, uncured solid rocket
fuel, & biomass slurries are typical industrial applications, while milk & blood are examples of naturally occurring suspensions. These
suspensions exhibit many non-Newtonian properties like rate-dependent rheology &
normal stresses. Other than volume fraction, particle material, inter-particle interactions determine the rheological behavior of suspension. The average
inter-particle gaps between the neighboring particles decrease significantly as
the suspension volume fraction approaches the maximum packing fraction in dense
suspensions. So, in this regime, the short-ranged non-contact interactions are
important. In addition, the particles come into contact due to
asperities on their surfaces. The surface asperities are present even in the
case of so-called smooth particles, as particles in real suspensions are not
perfectly smooth. Hence, contact forces become one of the essential factors to determine the rheology of
suspensions.</p><p> </p><p>Part I of this thesis investigates the effects
of microscopic inter-particle interactions on the rheological properties of
dense suspensions of non-Brownian particles by employing discrete particle
simulations. We show that increasing the roughness size results in a rise in
the viscosity & normal stress difference in the suspensions.
Furthermore, we observe that the jamming volume fraction decreases with the
particle roughness. Consequently, for suspensions close to jamming,
increasing the asperity size reduces the critical shear rate for shear
thickening (ST) transition, resulting in an early onset of discontinuous ST
(DST, a sudden jump in the suspension viscosity) in terms of volume fraction, &
enhances the strength of the ST effect. These findings are in excellent
agreement with the recent experimental measurements & provide a deeper
understanding of the experimental findings. Finally, we propose a constitutive
model to quantify the effect of the roughness size on the rheology of dense ST
suspensions to span the entire phase-plane. Thus, the constitutive model and
the experimentally validated numerical framework proposed can guide
experiments, where the particle surface roughness is tuned for manipulating the
dense suspension rheology according to different applications. </p><p> </p><p>A typical dense non-Brownian particulate
suspension exhibits shear thinning (decreasing viscosity) at a low shear rate
followed by a Newtonian plateau (constant viscosity) at an intermediate shear
rate values which transition to ST (increasing viscosity) beyond a critical
shear rate value and finally, undergoes a second shear-thinning transition at
an extremely high shear rate values. This part unifies & quantitatively
reproduces all the disparate rate-dependent regimes & the corresponding
transitions for a dense non-Brownian suspension with increasing shear rate. The
inclusion of traditional hydrodynamic interactions, attractive/repulsive DLVO
(Derjaguin and Landau, Verwey and Overbeek), contact
interactions, & constant friction reproduce
the initial thinning as well as the ST transition. However, to
quantitatively capture the intermediate Newtonian plateau and the second thinning, an additional interaction of non-DLVO origin & a
decreasing coefficient of friction, respectively, are essential; thus,
providing the first explanation for the presence these regimes.
Expressions utilized for various interactions and friction are determined from
experimental measurements, resulting in an excellent quantitative agreement
with previous experiments. </p><p><br></p><p><b>Part II: Motion in a stratified fluid</b></p><p>Density variations due to temperature or
salinity greatly influence the dynamics of objects like particles, drops, and
microorganisms in oceans. Density stratification hampers the vertical flow &
substantially affects the sedimentation of an isolated object, the hydrodynamic
interactions between a pair, and the collective behavior of suspensions in
various ways depending on the relative magnitude of stratification inertia
(advection), and viscous (diffusion) effects. This part investigates these
effects and elicits the hydrodynamic mechanisms behind some commonly observed
fluid-particle transport phenomena in oceans, like aggregation in horizontal
layers. The physical understanding can help us better model these phenomena
and, hence, predict their geophysical, engineering, ecological, and
environmental implications. </p><p><br></p><p>We investigate the self-propulsion of an
inertial swimmer in a linear density stratified fluid using the archetypal
squirmer model, which self-propels by generating tangential surface waves. We
quantify swimming speeds for pushers (propelled from the rear) and pullers
(propelled from the front) by direct numerical solution. We find that
increasing stratification reduces the swimming speeds of swimmers relative to
their speeds in a homogeneous fluid while reducing their swimming efficiency.
The increase in the buoyancy force experienced by these squirmers due to the
trapping of lighter fluid in their respective recirculatory regions as they move
in the heavier fluid is one of the reasons for this reduction. Stratification
also stabilizes the flow around a puller, keeping it axisymmetric even at high
inertia, thus leading to otherwise absent stability in a homogeneous fluid. On
the contrary, a strong stratification leads to instability in the motion of
pushers by making the flow around them unsteady 3D, which is otherwise steady
axisymmetric in a homogeneous fluid. Data for the mixing efficiency generated
by individual squirmers explain the trends observed in the mixing produced by a
swarm of squirmers. </p><p><br></p><p>In addition, the ubiquitous vertical density
stratification in aquatic environments significantly alters the swimmer
interactions affecting their collective motion &consequently ecological and
environmental impact. To this end, we numerically investigate the interactions
between a pair of model swimming organisms with finite inertia in a linear
density stratified fluid. Depending on the squirmer inertia and stratification,
we observe that the squirmer interactions can be categorized as i) pullers
getting trapped in circular loops, ii) pullers escaping each other with
separating angle decreasing with increasing stratification, iii) pushers
sticking to each other after the collision and deflecting away from the
collision plane, iv) pushers escaping with an angle of separation increasing
with stratification. Stratification also increases the contact time for
squirmer pairs. The results presented can help understand the mechanisms behind
the accumulation of planktonic organisms in horizontal layers in a stratified
environment like oceans and lakes. </p><p><br></p><p>Much work has been done to understand the settling dynamics of spherical particles in a homogeneous and stratified fluid. However, the effects of shape anisotropy on the settling dynamics in a stratified fluid are not entirely understood. To this end, we perform numerical simulations for settling oblate and prolate spheroids in a stratified fluid. We find that both the oblate and prolate spheroids reorient to the edge-wise and partially edge-wise orientations, respectively, as they settle in a stratified fluid completely different from the steady-state broad-side on orientation observed in a homogeneous fluid. We observe that reorientation instabilities emerge when the velocity magnitude of the spheroids falls below a particular threshold. We also report the enhancement of the drag on the particle from stratification. The torque due to buoyancy effects tries to orient the spheroid in an edge-wise orientation, while the hydrodynamic torque tries to orient it to a broad-side orientation. The buoyancy torque dominates below the velocity threshold, resulting in reorientation instability.<br></p>
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The Integration of Fuzzy Fault Trees and Artificial Neural Networks to Enhance Satellite Imagery for Detection and Assessment of Harmful Algal BloomsTan, Arie Hadipriono January 2019 (has links)
No description available.
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Characterization of cyanobacteria, cyanophage, and the symbiotic bacterial community in drinking water treatment wastes for sustainable control of HABsDavis, Angela Brooke January 2020 (has links)
No description available.
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Varved lake sediment used to assess anthropogenic and environmental change in Summit Lake, Akron, OhioRego, Melissa 26 June 2022 (has links)
No description available.
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Nitrate metabolism in the dinoflagellate Lingulodinium polyedrumDagenais Bellefeuille, Steve DB. 12 1900 (has links)
Les dinoflagellés sont des eucaryotes unicellulaires retrouvés dans la plupart des
écosystèmes aquatiques du globe. Ces organismes amènent une contribution substantielle à la
production primaire des océans, soit en tant que membre du phytoplancton, soit en tant que
symbiontes des anthozoaires formant les récifs coralliens. Malheureusement, ce rôle
écologique majeur est souvent négligé face à la capacité de certaines espèces de dinoflagellés
à former des fleurs d'eau, parfois d'étendue et de durée spectaculaires. Ces floraisons d'algues,
communément appelées "marées rouges", peuvent avoir de graves conséquences sur les
écosystèmes côtiers, sur les industries de la pêche et du tourisme, ainsi que sur la santé
humaine. Un des facteurs souvent corrélé avec la formation des fleurs d'eau est une
augmentation dans la concentration de nutriments, notamment l’azote et le phosphore. Le
nitrate est un des composants principaux retrouvés dans les eaux de ruissellement agricoles,
mais également la forme d'azote bioaccessible la plus abondante dans les écosystèmes marins.
Ainsi, l'agriculture humaine a contribué à magnifier significativement les problèmes associés
aux marées rouges au niveau mondial. Cependant, la pollution ne peut pas expliquer à elle
seule la formation et la persistance des fleurs d'eau, qui impliquent plusieurs facteurs biotiques
et abiotiques. Il est particulièrement difficile d'évaluer l'importance relative qu'ont les ajouts de
nitrate par rapport à ces autres facteurs, parce que le métabolisme du nitrate chez les
dinoflagellés est largement méconnu. Le but principal de cette thèse vise à remédier à cette
lacune. J'ai choisi Lingulodinium polyedrum comme modèle pour l'étude du métabolisme du
nitrate, parce que ce dinoflagellé est facilement cultivable en laboratoire et qu'une étude
transcriptomique a récemment fourni une liste de gènes pratiquement complète pour cette
espèce. Il est également intéressant que certaines composantes moléculaires de la voie du
nitrate chez cet organisme soient sous contrôle circadien. Ainsi, dans ce projet, j'ai utilisé des
analyses physiologiques, biochimiques, transcriptomiques et bioinformatiques pour enrichir
nos connaissances sur le métabolisme du nitrate des dinoflagellés et nous permettre de mieux
apprécier le rôle de l'horloge circadienne dans la régulation de cette importante voie
métabolique primaire.
Je me suis tout d'abord penché sur les cas particuliers où des floraisons de dinoflagellés
sont observées dans des conditions de carence en azote. Cette idée peut sembler contreintuitive,
parce que l'ajout de nitrate plutôt que son épuisement dans le milieu est généralement
associé aux floraisons d'algues. Cependant, j’ai découvert que lorsque du nitrate était ajouté à
des cultures initialement carencées ou enrichies en azote, celles qui s'étaient acclimatées au
stress d'azote arrivaient à survivre près de deux mois à haute densité cellulaire, alors que les
cellules qui n'étaient pas acclimatées mourraient après deux semaines. En condition de carence
d'azote sévère, les cellules arrivaient à survivre un peu plus de deux semaines et ce, en arrêtant
leur cycle cellulaire et en diminuant leur activité photosynthétique. L’incapacité pour ces
cellules carencées à synthétiser de nouveaux acides aminés dans un contexte où la
photosynthèse était toujours active a mené à l’accumulation de carbone réduit sous forme de
granules d’amidon et corps lipidiques. Curieusement, ces deux réserves de carbone se
trouvaient à des pôles opposés de la cellule, suggérant un rôle fonctionnel à cette polarisation.
La deuxième contribution de ma thèse fut d’identifier et de caractériser les premiers
transporteurs de nitrate chez les dinoflagellés. J'ai découvert que Lingulodinium ne possédait
que très peu de transporteurs comparativement à ce qui est observé chez les plantes et j'ai
suggéré que seuls les membres de la famille des transporteurs de nitrate de haute affinité 2
(NRT2) étaient réellement impliqués dans le transport du nitrate. Le principal transporteur
chez Lingulodinium était exprimé constitutivement, suggérant que l’acquisition du nitrate chez
ce dinoflagellé se fondait majoritairement sur un système constitutif plutôt qu’inductible.
Enfin, j'ai démontré que l'acquisition du nitrate chez Lingulodinium était régulée par la lumière
et non par l'horloge circadienne, tel qu'il avait été proposé dans une étude antérieure.
Finalement, j’ai utilisé une approche RNA-seq pour vérifier si certains transcrits de
composantes impliquées dans le métabolisme du nitrate de Lingulodinium étaient sous
contrôle circadien. Non seulement ai-je découvert qu’il n’y avait aucune variation journalière
dans les niveaux des transcrits impliqués dans le métabolisme du nitrate, j’ai aussi constaté
qu’il n’y avait aucune variation journalière pour n’importe quel ARN du transcriptome de
Lingulodinium. Cette découverte a démontré que l’horloge de ce dinoflagellé n'avait pas
besoin de transcription rythmique pour générer des rythmes physiologiques comme observé
chez les autres eukaryotes. / Dinoflagellates are unicellular eukaryotes found in most aquatic ecosystems of the
world. They are major contributors to carbon fixation in the oceans, either as free-living
phytoplankton or as symbionts to corals. Dinoflagellates are also infamous because some
species can form spectacular blooms called red tides, which can cause serious damage to
ecosystems, human health, fisheries and tourism. One of the factors often correlated with algal
blooms are increases in nutrients, particularly nitrogen and phosphorus. Nitrate is one of the
main components of agricultural runoffs, but also the most abundant bioavailable form of
nitrogen in marine environments. Thus, agricultural activities have globally contributed to the
magnification of the problems associated with red tides. However, bloom formation and
persistence cannot be ascribed to human pollution alone, because other biotic and abiotic
factors are at play. Particularly, it is difficult to assess the relative importance of nitrate
addition over these other factors, because nitrate metabolism in dinoflagellate is mostly
unknown. Filling part of this gap was the main goal of this thesis. I selected Lingulodinium
polyedrum as a model for studying nitrate metabolism, because this dinoflagellate can easily
be cultured in the lab and a recent transcriptomic survey has provided an almost complete
gene catalogue for this species. It is also interesting that some molecular components of the
nitrate pathway in this organism have been reported to be under circadian control. Thus, in this
project, I used physiological, biochemical, transcriptomic and bioinformatic approaches to
enrich our understanding of dinoflagellate nitrate metabolism and to increase our appreciation
of the role of the circadian clock in regulating this important primary metabolic pathway.
I first studied the particular case of dinoflagellate blooms that occur and persist in
conditions of nitrogen depletion. This idea may seems counterintuitive, because nitrogen
addition rather than depletion, is generally associated with algal blooms. However, I
discovered that when nitrate was added to nitrogen-deficient or nitrogen-sufficient cultures,
those that had been acclimated to nitrogen stress were able to survive for about two months at
high cell densities, while non-acclimated cells died after two weeks. In conditions of severe
nitrogen limitation, cells could survive a little bit more than two weeks by arresting cell
division and reducing photosynthetic rates. The incapacity to synthesize new amino acids for
these deprived cells in a context of on-going photosynthesis led to the accumulation of
reduced carbon in the form of starch granules and lipid bodies. Interestingly, both of these
carbon storage compounds were polarized in Lingulodinium cells, suggesting a functional role.
The second contribution of my thesis was to identify and characterize the first nitrate
transporters in dinoflagellates. I found that in contrast to plants, Lingulodinium had a reduced
suite of nitrate transporters and only members of the high-affinity nitrate transporter 2 (NRT2)
family were predicted to be functionally relevant in the transport of nitrate. The main
transporter was constitutively expressed, which suggested that nitrate uptake in Lingulodinium
was mostly a constitutive process rather than an inducible one. I also discovered that nitrate
uptake in this organism was light-dependent and not a circadian-regulated process, as
previously suggested.
Finally, I used RNA-seq to verify if any transcripts involved in the nitrate metabolism
of Lingulodinium were under circadian control. Not only did I discovered that there were no
daily variations in the level of transcripts involved in nitrate metabolism, but also that there
were no changes for any transcripts present in the whole transcriptome of Lingulodinium. This
discovery showed that the circadian timer in this species did not require rhythmic transcription
to generate biological rhythms, as observed in other eukaryotes.
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Phytoplankton dynamics in a seasonal estuaryChan, Terence January 2006 (has links)
[Truncated abstract] The Swan River is a highly seasonal estuary in the south-west of Western Australia. Salinity may vary from fresh to marine at various times throughout the estuary, depending mostly on the intensity of freshwater discharge. There are occasional problematic dinoflagellate blooms which have spurred investigation of the dynamics of the phytoplankton community. The objective of this research was to examine how phytoplankton biomass and species' successions are influenced by the multiple variables in the aquatic ecosystem, and, if possible, to determine the dominant factors ... Comparisons of phytoplankton nutrient limitation simulations with experimental observations from field bioassays require further investigation, but reinforce findings that nutrients may only limit phytoplankton biomass when there is a convergence of favourable hydrological and hydrodynamic conditions. The Swan River estuary has undergone substantial hydrological modifications from pre-European settlement. Land clearing has increased freshwater discharge up to 5- fold, while weirs and reservoirs for water supply have mitigated this increase and reduced the duration of discharge to the estuary. Nutrient loads have increased approximately 20-fold from pre-European levels. The individual and collective impacts of these hydrological changes on the Swan River estuary were examined using the hydrodynamic-ecological numerical model. The simulation results indicate that despite increased hydraulic flushing and reduced residence times, increases in nutrient loads are the dominant perturbation, producing increases in the frequency and biomass of blooms by both estuarine and freshwater phytoplankton. By comparison, changes in salinity associated with altered seasonal freshwater discharge have a limited impact on phytoplankton dynamics. Reductions of nutrient inputs into the Swan River estuary from its catchment will provide a long-term improvement in water quality but manipulations of freshwater discharge have the potential to provide a provisional short-term remediation measure allowing at least partial control of phytoplankton bloom potential and eutrophication.
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