Mammals and fish rely on hormones to regulate blood glucose levels. The two major glucose regulating hormones are insulin and glucagon. Literature on mammalian insulin and glucagon is quite extensive, however, there is limited information on how these hormones regulate blood glucose levels in fish. The material available for fish mostly pertains to changes in glucose concentration and gene expression of enzymes, but there is no information on the direct influence they have on glucose kinetics. Therefore, the main goal of my thesis is to measure the change in hepatic glucose production and glucose disposal when rainbow trout are administered insulin or glucagon. The beginning of my research focused on insulin. I hypothesized that rainbow trout respond to insulin by decreasing hepatic glucose production and increase glucose disposal, just like mammals. To test this, I infused insulin for 4 hours at 1.5 g insulin kg 1 min-1. I measured glucose disposal (Rd glucose), hepatic glucose production (Ra glucose), and blood glucose concentration. Following insulin administration the glucose fluxes decreased steadily (Rd glucose -37% and Ra glucose -43%). The decline in blood glucose levels follows the difference between Rd and Ra. These results explain why rainbow trout are unable to clear a glucose load to the same degree as mammals. The second major glucose hormone (glucagon) is what interested me for the second part of the research. The limited information on fish glucagon is even less than that of fish insulin. I speculated that trout respond to glucagon the same way mammals do (increase hepatic glucose production and show no affect on glucose disposal). To study the effects of glucagon on glucose fluxes, I tracked the changes in Ra and Rd glucose. The results showed glucose fluxes showed no siginificant difference from baseline in the first few hours, then steadily decreasing until the final time point reached values below baseline. Therefore, these experiments revealed that glucagon follows a similar pattern of effects in trout as mammals. However, the strength of the response to glucagon is different between trout and mammals. This thesis is the first to investigate the effects of insulin and glucagon on glucose kinetics in rainbow trout. I have concluded that rainbow trout have different responses to insulin and glucagon when compared to mammals. Furthermore, fish showing limited glucoregulatory capacity can be partially explained by their responses to insulin and glucagon.

The enthalpy (sensible and latent heat) exchange processes within the surface layers at an air-water interface have been examined in 15-m wind-wave tunnel at the University of Miami. Measurements yielded 72 mean values of fluxes and bulk variables in the wind speed (referred to 10 m) range form 0.6 to 39 m/s, covering a full range of aerodynamic conditions from smooth to fully rough. Meteorological variables and bulk enthalpy transfer coefficients, measured at 0.2-m height, were adjusted to neutral stratification and 10-m height following the Monin-Obukhov similarity approach. The ratio of the bulk coefficients of enthalpy and momentum was estimated to evaluate Emanuel's (1995) hypothesis. Indirect "Calorimetric" measurements gave reliable estimates of enthalpy flux from the air-water interface, but the moisture gained in the lower air from evaporation of spray over the rough water remained uncertain, stressing the need for flux measurements along with simultaneous spray data to quantify spray's contribution to the turbulent air-water enthalpy fluxes.

Before January 2003, the Dapeng Bay lagoon was occupied by oyster culture racks and fish farming cages. Along with the development of the Dapeng Bay National Scenic Area Administration, the government has started taking actions on removing oyster culture racks, and has kept improving the quality of lagoon water. Nowadays, the government is implementing sediment dredging plan. As to discuss the change of biogeochemical processes, this study is divided by three parts, including the first stage, before the removal of oyster culture rafts; second stage, after the removal of oyster culture rafts, and the third stage, after implementation of sediment dredging. At the first stage, the annual mean of water exchange time at the Dapeng Bay was approximately 10 days. At the second and third stage, the annual mean of water exchange time were 6.2 days and 8.3 days, respectively. The difference is not significant between the second stage and third stage. The trend of water exchange time is similar to the seawater exchange rate. Distributions of chlorophyll a were controlled by temperature and solar radiation, rather than by nutrient concentration throughout three-stage periods. Although the change tendency between chlorophyll a, DIN, and DIP at the third stage is similar, chlorophyll a correlated positively with DIN and DIP only in fall. The net ecosystem production (NEP) was positive (p¡Ðr > 0) at all three stages, so the Dapeng Bay was always an autotrophic system throughout the study period. Before the removal of the oyster culture racks, the NEP was 5.64 mole C m-2 yr-1, after that, it increase to 11.64 mole C m-2 yr-1. During the sediment dredging period, the NEP was 14.31 mole C m-2 yr-1. The NEP increases 106 % from the first stage to the second stage, and increases 23% from the second stage to the third stage. The environmental remediation appears to produce significant influence on NEP. The concentration of DIN¡BDSi¡BDIP decreases by removing the oyster culture of racks. But the concentrations of particulate and dissolved organic carbon and nitrogen increase sharply after removing the oyster culture racks. Nevertheless, the concentration of dissolved organic carbon, nitrogen and the phosphorus decreases during the third stage, resulted mainly from the improvement of water quality. The system changed from the condition of phosphorus surplus (Si/N=1.8¡Ó1.2 and N/P=7.4¡Ó5.2) during the first and second stage to the condition of phosphorus limitation (Si/N=1.0¡Ó1.2 and N/P=22.2¡Ó18.7) during the third stage. The ratios of particulate organic carbon and nitrogen (POC/PN) are 7.7¡Ó1.1, 8.0¡Ó1.0, 6.5¡Ó1.3, respectively. The ratio at the third stage is very close to the Redfield ratio (C/N=6.6), which may result from the improvement of water quality. In terms of temporal and spatial variation of various parameters, DO variability was strong in the time scale than in the spatial scale, but nutrients and POC show a decrease of spatial variability from the first stage to the third stage. The removal of oyster culture racks, and the implementation of sediment dredging plan at the Dapeng Bay have significant influence on the improvement of lagoon environment for the past ten years.

This study aims to understand the role of the Tapong Bay on carbon biogeochemical cycle in the coastal zone and the influence of terrigenous inputs on ecosystem functioning in the Tapong Bay. The Tapong Bay is a semi-enclosed lagoon, occupied largely by fish farming cages and oyster culture racks. There is only one tidal inlet for exchanging water between the Tapong Bay and Taiwan Strait, which results in a low water exchange rate and oxygen deficient condition in the bottom water of the inner bay. The annual mean of water exchange time is about 10.6 days that is much longer than that in the Chiku Lagoon (5.8 days). Experimental results show that biological activity and variations of hydrochemistry primarily control the distributions of carbon and nutrients. Excess of DIP likely occurred in the Tapong Bay. Seasonal variations of primary productivity are apparently controlled by temperature, solar radiation and turbidity. The regression slope between particulate organic carbon and nitrogen approaches the Redfield ratio, indicating that organic carbon is derived primarily from biological production. The stratification of water column in the Tapong Bay was observed throughout the year. Diffusion from sediment may thus contribute significantly to nutrient distributions in bottom water. Diffusion flux estimated from porewater to bottom water is about 7.6% of annual mean input for DIN and is about 1.0% for DIP. Calcification process was observed in the Tapong Bay indicating that the oyster culture would affect the carbon budget in the bay. The annual mean production rate of organic carbon estimated from the biogeochemical model is about 5.80 mole C m-2 yr-1, implying that the Tapong Bay is an autotrophic system. The net ecosystem production (NEP) derived from diel observation is about 6.29 mmole C m-2 d-1 that is closed to 6.65 mmole C m-2 d-1 estimated from the biogeochemical modeling. The annual nitrogen fixation exceeds the annual denitrification [(nfix-denit)¡×1.30 mole m-2 yr-1] in the Tapong Bay. Carbon biogeochemical fluxes and budgets differ significantly between the Tapong Bay and the Chiku Lagoon, which may be arisen from pronounced difference in terrigenous inputs and seawater exchange rates.

The cyclic nucleotide monophosphates (CNs), cAMP and cGMP, are second messengers that participate in the regulation of development, metabolism and adaptive responses. In plants, CNs are associated with the control of pathogen responses, pollen tube orientation, abiotic stress response, membrane transport regulation, stomatal movement and light perception. In this study, we hypothesize that cAMP and cGMP promote changes in the transcription level of genes related to photosynthesis, high light and membrane transport in Arabidopsis thaliana leaves and, that these changes at the molecular level can have functional biological consequences. For this reason we tested if CNs modulate the photosynthetic rate, responses to high light and root ion transport. Real time quantitative PCR was used to assess transcription levels of selected genes and infrared gas analyzers coupled to fluorescence sensors were used to measure the photosynthetic parameters. We present evidence that both cAMP and cGMP modulate foliar mRNA levels early after stimulation. The two CNs trigger different responses indicating that the signals have specificity. A comparison of proteomic and transcriptional changes suggest that both transcriptional and post-transcriptional mechanisms are modulated by CNs. cGMP up-regulates the mRNA levels of components of the photosynthesis and carbon metabolism. However, neither cAMP nor cGMP trigger differences in the rate of carbon assimilation, maximum efficiency of the photosystem II (PSII), or PSII operating efficiency. It was also demonstrated that CN regulate the expression of its own targets, the cyclic nucleotide gated channels - CNGC. Further studies are needed to identify the components of the signaling transduction pathway that mediate cellular changes and their respective regulatory and/or signaling roles.

Phosphorus is a key element for life. This work reviews the role of phosphorus in life. Theories on the origin of life are confounded by a lack of reactive phosphorus, and attempts to overcome the dearth of reactive phosphorus must employ unrealistic phosphorus compounds, energetic organic compounds, or unusual physical conditions.Meteoritic schreibersite provided an abundant source of reactive phosphorus for the early Earth. Water corrodes schreibersite to form a mixed valence series of phosphorus compounds. Schreibersite corrosion was studied by a variety of techniques, including NMR, MS, XRD, and EPR. Reduced phosphorus in schreibersite corrodes through release of phosphite radicals which react with other radicals to form the phosphorus compounds observed. These radicals are also capable of phosphorylating simple organic compounds to form P-C and P-O-C linkages.The meteoritic mass flux was calculated using the mass frequency distribution of several meteorite collections. Much of the meteoritic mass that falls to the Earth is composed of metallic material which supplies abundant reactive phosphorus. Meteorites are a comparatively poorer source of carbon. Craters concentrate both reduced phosphorus and organic compounds through geomorphologic processes.Phosphorus and sulfur biochemistry are intricately linked in metabolism. The cosmochemistry of sulfur was studied in depth using changing C/O ratios, sulfide formation kinetics, and gas diffusion. The results have implications for meteorites, studies of Jupiter, and of protoplanetary disks.

Throughout the late 20th and early 21st century, the global temperature has been on the rise, a process that has been accelerated in the Arctic. The Arctic surface temperatures have risen at a factor of 3 greater rate than the global average, leading to the term Arctic Amplification of climate change. In this study, the enhanced warming of the Arctic, and the enhancement at the Arctic surface in comparison to the warming of the atmosphere aloft, is investigated through a reconstruction of the past surface energy balance by a model driven by downwelling irradiance reconstructed using radiosonde profiles and the radiative transfer code SBDART. The downwelling irradiance is shown to be increasing over the time-period of 1994-2009, and the sources of this increase are diagnosed. The time-evolution of the surface flux terms are discussed, and the sensitivity of the surface temperature to changes in atmospheric temperature is investigated.

Στη διατριβή υπολογίζονται μηνιαίες τιμές για κάθε μια από τις τέσσερις συνιστώσες της ροής θερμότητας στη διεπιφάνεια αέρα-θάλασσας σε πέντε σημεία στο Αιγαίο Πέλαγος για το χρονικό διάστημα 2000-2008 με χρήση δεδομένων α) από το δίκτυο πλωτών μετρητικών σταθμών του συστήματος ΠΟΣΕΙΔΩΝ του Ελληνικού Κέντρου Θαλασσίων Ερευνών, β) από τη δορυφορική πλατφόρμα SSM/I και γ) από την Εθνική Μετεωρολογική Υπηρεσία. Οι μηνιαίες τιμές που υπολογίζονται για κάθε μία από τις τέσσερις συνιστώσες της ροής θερμότητας συγκρίνονται με τις αντίστοιχες από ευρέως χρησιμοποιούμενες βάσεις δεδομένων με σκοπό την αξιολόγηση των βάσεων αυτών για την περιοχή του Αιγαίου Πελάγους. Στη συνέχεια χρησιμοποιούνται οι στατιστικά καλύτερες βάσεις για τη διερεύνηση των χαρακτηριστικών της ροής θερμότητας στο Αιγαίο σε βάθος χρόνου. Εξετάζεται η συσχέτιση των συνιστωσών της ροής θερμότητας με γνωστούς και πειραματικούς κλιματικούς δείκτες, με τη μεγάλης κλίμακας ατμοσφαιρική κυκλοφορία και με το πεδίο του υετίσιμου ύδατος σε μια περιοχή που περιλαμβάνει τον ανατολικό Ατλαντικό, την Ευρώπη και τη βόρεια Αφρική. Τέλος εξετάζεται η συνεισφορά και η συμπεριφορά των συνιστωσών στη μεταβλητότητα της ροής θερμότητας μεταξύ αέρα και θάλασσας στο Αιγαίο Πέλαγος καθώς και το πεδίο της ατμοσφαιρικής πίεσης που ευνοεί την εμφάνιση των ακρότατων τιμών της ξεχωριστά για την ψυχρή και τη θερμή περίοδο του έτους. / Monthly mean values for the each one of the four air-sea heat fluxes components are calculated at five sites in the Aegean Sea for the period 2000-2008. For this calculation three different kinds of data are used: a) data from the Greek network of oceanographic buoys of the Hellenic Centre for Marine Research (the POSEIDON system), b) data from the NASA satellite platform SSM/I, and c) data from the Hellenic National Meteorological Service. The calculated monthly mean values are compared with the corresponding values from broadly used data bases in order to investigate the suitability of these data bases for the Aegean Sea. The statistically robust data archives are used to examine the characteristics of the surface fluxes over an extended time period. More specifically, the correlation between the surface heat exchange and several climatic indices, the large scale atmospheric circulation and the total precipitable water are investigated over an extended area covering the eastern part of the Atlantic Ocean, Europe and north Africa. The behavior and the contribution of each air-sea heat fluxes component to surface fluxes variability over the Aegean are also identified. Last, the sea level pressure (SLP) patterns favoring the uppermost and the lowermost air-sea heat budget values are described separately for the cold and for the warm period of the year.

Direct measurements of wintertime surface heat fluxes between the ocean and atmosphere in lead and polynya environments in the Canadian Arctic are presented. Such environments can yield very large vertical temperature gradients during the winter months and are particularly dynamic micrometeorological environments. We found that sensible heat fluxes can exceed +100 W m-2 during the winter months, much larger than most regional estimates (~ 0 W m-2). In addition, large heat fluxes are shown to affect the characteristics of the near surface temperature inversion (temperature increases with height). The height, depth and strength of the characteristic wintertime inversion are shown to be influenced in cases where large surface fluxes were observed. Such findings are likely to have implications on the regional and planetary heat budget, general circulation models and larger scale weather processes, which most often omit local scale heat fluxes in their analyses and calculations. / February 2016

The stability and survival of salt marshes is typically linked to the competing influences of sea-level rise, subsidence, and sediment accumulation and erosion. However, consideration must also be made for wind waves that regulate the erosion of salt marsh shorelines and resuspend sediments in bordering tidal flats thus providing material for marsh accretion. This thesis examines the mechanisms in which wind waves affect marsh morphology, the mechanisms of salt marsh boundary erosion, in addition to linking the processes responsible for sediment mobilization between tidal flats and adjacent salt marshes. Sediment concentration within an open-coast marsh creek along the Louisiana chenier plain is shown to be related to the local wave climate and channel velocity. Calculations of sediment fluxes during ebb and flood tides indicates that while large volumes of sediment are mobilized into the marsh when wind waves are present, only a small portion is stored during each tidal cycle. In the coastal lagoon setting of Hog Island Bay, Virginia, marsh shoreline erosion rates were estimated from direct surveys and through analysis of aerial photographs. Erosion rates averaged 1.3 m/yr, similar to the 50-year historical average determined from previous work at the same location. Based on a calibrated numerical model for wind waves, the average erosion rate was linked to the energy of the waves attacking the marsh boundary. Additionally, results suggest that the effect of large waves forming during storms on erosion rates is negligible. Variations in erosion rates were linked to shoreline sinuosity (a proxy used to describe the result of wave concentration through erosive gullies), sediment characteristics, faunal activity, and marsh elevation. The culmination of the work leads to the hypothesis that waves have two opposite effects on salt marshes. On one hand they erode marsh boundaries thus reducing marsh area; on the other hand they mobilize large volumes of sediments in nearby tidal flats which may facilitate marsh accretion thus contrasting sea-level rise. In conclusion, wind waves destabilize marshes along the horizontal direction despite their potential vertical stability.