This dissertation investigate to determine the presence of biological nitrogen fixation in two reservoirs in the southwestern United States: Lake Arlington and Lake Ray Hubbard.

The effect of power ultrasound on algae blooms (Microcystis aeruginosa) over a 30 minute period was assessed using 200 and 400 mL suspensions of optical density of 2.0 at 680 nm. The frequencies employed were 20, 40, 580 (40%, 80%, and maximum intensity), 864 (40%, 80% and maximum intensity) and 1146 kHz (40%, 80% and maximum intensity). Ultrasound can induce two different effects on algal cells; inactivation at high power (≥ 0.0022 Wcm-3) and de-agglomeration at low power (≤ 0.0042 Wcm-3). Ultrasonic effects were observed using haemocytometer, optical density, UV-visible spectrometer, fluorospectrometer and flow cytometry. Using a 40 kHz bath (0.0214 Wcm-3) led to de-agglomeration resulting in an overall increase in algae of -0.28% by haemocytometer and -4.20% by optical density. The highest inactivation achieved was 91.54% (haemocytometer) and 44.63% (optical density) using 1146 kHz (maximum intensity, 0.0248 Wcm-3) and 200 mL suspension. In terms of efficiency to achieve inactivation (i.e. inactivation % / power) the best result was observed at 864 kHz (40% power setting, 0.0042 Wcm-3) with 200 mL suspension giving 8226.19 by haemocytometer and 5011.90 by optical density. This initial part of the study allowed a comparison to be made of the ultrasonic parameters that would lead to optimum algae removal in terms of acoustic energy input. The haemocytometer results for cells number were generally higher than those indicated by optical density which is probably due to the fact that the former records only cell numbers remaining whereas the latter is an overall measure of algae concentration (ruptured cells will still register, because their contents remain in suspension). Studies on de-agglomeration and inactivation were also undertaken using small or medium-scale ultrasonic equipment that were models for industrial scale systems. The following volumes of algae suspension and equipment were employed: Sonolator (Sonic Corporation, 5L flow), 16 kHz and 20 kHz Dual Frequency Reactor (DFR, Advanced Sonics LLC, 1L static and 3.5 L flow), 20 kHz Vibrating Tray (Advanced Sonics LLC, 1.5L static) and 20 kHz ultrasonic probe (made at Southeast University, 4L static). The most effective inactivation effects were obtained with the DFR reactor in static mode and 60% power setting for 10 minutes which achieved reductions calculated at 79.25% using haemocytometry and 60.44% by optical density. The third part of this study was to gain a greater understanding of the basic mechanisms of the action of ultrasound on algae and to interpret this in terms of its potential for algal cell removal and control. Algal cell activity was assessed by three methods: using a UV-visible spectrometer (Shimazu, 2450PC), a fluorometer (Shimazu, RF5301) and a flow cytometer (BD FACS Calibur). Ultrasonic damage to Chlorophyll A was revealed through observation of the loss in UV-Vis spectrophotometer peaks around 600 nm together with the decrease in fluorometer results for peaks around 500 and 680 nm. Flow cytometer results were able to identify the number of both intact cells and damaged/ruptured cells thus giving greater insight into the mechanism of ultrasonic inactivation. The direct rupture of cells by power ultrasound was prevalent at low frequencies ≤ 40 kHz due to the mechanical effects of cavitation collapse and inactivation of algal cells by free radicals occurred at high frequencies ≥ 100 kHz and medium powers where mechanical effects are much reduced. In conclusion, this work has shown that power ultrasound can provide a suitable method to control algal growth in small and medium laboratory scales. Scale-up beyond this point is the subject of further research but the results herein clearly demonstrate the importance of choosing the correct ultrasonic parameters in terms of frequency, power and exposure time.

No description available.

Anthropogenic effects are causing significant environmental degradation, and regardless of actions taken to mitigate further changes, humans and animals will have to live with these impacts (IPCC 2019). Rapid population growth in coastal regions, saltwater intrusion (SWI), lowering water quality, and increased presence of toxic materials are degrading coastal resiliency. An important and popular coastal region for the United States is the state of Florida, and it is also an area extremely vulnerable to aspects of climate change such as sea-level rise (SLR) (Noss 2011). This project analyzes how the state is currently experiencing the direct and indirect impacts of toxic materials on the state’s people, environment, and economy. It will do so through analysis of the performance of federal legislation created with the intent to protect human and environmental health, quantification of current rates of using toxic chemicals and potential pollution, as well as quantifying effects of both anthropogenic and natural toxic materials on Florida’s housing market. It was anticipated that legislation such as the Safe Drinking Water Act (SDWA) to ensure strict enforcement of drinking water standards and the Emergency Planning Community Right to Know Act (EPCRA) to prevent toxic pollution would be present in the vulnerable region. Also that natural phenomenon such as the harmful algal blooms significantly degrade the housing market through decreasing income through tourism and lowering housing prices in coastal neighborhoods. This project found that the SDWA is not being enforced, EPCRA data shows a huge risk to potential exposures from large storms, and that algal blooms are significant to housing prices in the state. Using these scientific findings to improve policy and appropriately communicating complex scientific topics to the public is extremely important. Doing so will enable a higher level of coastal resiliency as communities continue attempt to mitigate climate change, but also learn to understand current impacts and better live in a degrading environment.

Mälaren är Sveriges tredje största sjö och även den dricksvattentäkt som försörjer flest människor i Sverige med vatten. Ett hot mot Mälarens vattenkvalité är algblomningar då vissa cyanobakterier producerar giftiga cyanotoxiner. Under 60-talet ledde övergödningen i Mälaren till kraftiga algblomningar och för att kunna råda bot på problemet infördes ett övervakningsprogram som nu har följt Mälarens utveckling i snart 60 år. I denna studie undersöktes med hjälp av detta övervakningsprogram vid vilka förhållanden cyanobakterier, framförallt de kvävefixerande Nostocales, frodas i Mälaren. Därefter önskades slutsatser kunna dras om vilka åtgärder som kan vara lämpliga för hålla nere populationen och därmed inte utgöra en risk för dricksvattenkvalitén.  Först genomfördes en långtidsstudie för att analysera vilka parametrar som historiskt har haft den tydligaste kopplingen till biovolymen växtplankton, cyanobakterier och Nostocales med hjälp av en multivariat regressionsmodell (PLS). Från detta framgick att de undersökta parametrarna kunde förklara 29 % av variationen i biovolymen för växtplankton, 41 % för cyanobakterier och 45 % för Nostocales. För växtplankton var pH och siktdjup de parametrar som kunde förklara störst del av variationen i biovolym och för cyanobakterier och Nostocales var istället vattentemperaturen, oorganiskt kväve/totalfosfor samt halten oorganiskt kväve de parametrar som hade tydligast koppling till biovolymen.  Därefter genomfördes en säsongsstudie för att kunna förklara nutida halter och säsongsvariationer för fem av Mälarens mätstationer (Ekoln, Galten, Granfjärden, Görväln och Södra Björkfjärden). Variationen av halten cyanobakterier kopplades närmast till temperaturen eftersom cyanobakterierna till stor del var begränsade till sommar och sensommar. Övriga växtplankton kunde däremot förekomma i höga halter även under våren. Att Ekoln hade betydligt högre halter oorganiskt kväve än Galten skulle kunna förklara skillnaden i andelen Nostocales mellan de två mätstationerna, där Galten hade en stor andel Nostocales och Ekoln en låg andel. Dock kunde kvävehalten inte förklara skillnader i fördelning mellan kvävefixerande och icke kvävefixerande cyanobakterier för de andra mätstationerna. Galtens stora tillrinning, grunda förhållanden och artrikedom skulle även kunna förklara bassängens höga halter av växtplankton under hela året.  Då temperaturen visat sig vara den parameter med tydligast koppling till cyanobakteriernas tillväxt är att begränsa den globala uppvärmningen den viktigaste åtgärden för att förhindra en ökad algblommning i framtiden. Kring resterande parametrar var slutsatser svåra att dra och i och med osäkerheten i frågan är en fortsatt noggrann miljöövervakning och handlingsplan när problemen väl uppstår av stor vikt. / Lake Mälaren is the third largest lake in Sweden and the source of drinking water for two million people. A threat to the water quality of Lake Mälaren is algal blooms since some cyanobacteria produce toxic cyanotoxins. In the 1960s, eutrophication in Lake Mälaren led to heavy algal blooms and in order to handle the problem, a monitoring program was introduced that has now followed Lake Mälaren's development for almost 60 years. In this study, the conditions under which cyanobacteria, especially the nitrogen-fixing Nostocales, thrive in Lake Mälaren was analysed using data from the monitoring program. Thereafter the goal was to draw conclusions regarding which measures may be needed to keep the population down so as not to pose a risk to drinking water quality. To begin with, a long-term study was conducted to analyse which parameters have historically had the clearest connection to the biovolume of phytoplankton, cyanobacteria and Nostocales using a multivariate regression model (PLS). This showed that the examined parameters could explain 29 % of the variation in phytoplankton biovolume, 41 % of the variation in the cyanobacteria biovolume and 45 % of the variation in Nostocales biovolume. For phytoplankton, pH and water transparency were the parameters that could explain most of the variation in biovolume, and for cyanobacteria and Nostocales, water temperature, the ratio between inorganic nitrogen and total phosphorus and the content of inorganic nitrogen were the parameters most clearly linked to the biovolume. Thereafter, a seasonal study was conducted to help explain current levels and seasonal variations for five of Lake Mälaren's measuring stations (Ekoln, Galten, Granfjärden, Görväln and Södra Björkfjärden). The variation of the cyanobacteria level was most closely linked to the temperature, as cyanobacteria was mostly limited to the summer. The ratio between inorganic nitrogen and total phosphorus and the content of inorganic nitrogen seemed to be an explanation for the difference between the high share of Nostocales in Galten where nitrogen was scarce, and the low proportions in Ekoln where nitrogen was abundant, but did not explain the distribution between nitrogen-fixing and non nitrogen-fixing cyanobacteria in the other basins. Galten's large inflow, shallow conditions and species richness could also explain the basin's high levels of phytoplankton throughout the year. With temperature as the parameter most clearly linked to the content of cyanobacteria, limiting global warming is the most important of measures to prevent increased algal blooms in the future. With regard to the remaining parameters, conclusions were difficult to draw and due to the uncertainty in the matter, continued close environmental monitoring and an action plan once the problems arise are of great importance.

No description available.

No description available.

No description available.

No description available.

The current study focuses on the phenomenon, mostly accounted within the past recent time, of the algae blooms (chlorophyll burst) in the area of the North Aegean Sea. The study attempts to coincide and amplify the approach of Satellite Remote Sensing monitoring, as means of applied oceanographic methods, in order for possible seasonal, spatio-temporal trends of this phenomenon to be identified, thus making the correlation of the indices-variations, though interdisciplinary, to be explained to an extend plainly, in terms of ‘why’ and ‘why-then’ they occur. The North Aegean Sea is directly influenced by the outflow of the Black Sea water masses, through the Dardanelles Strait. Secondary, riverine discharge is into account, along with special hydrodynamic characteristics of the basin. This Black Sea contribution to the North Aegean basin is cold, brackish and rather rich in biomass and nutrients and via the eutrophic blooms, fluctuate the relative meso-poor nutrient character of the basin. The environmental impacts and causes of the occurrences have a multidisciplinary analysis. They affect local ecology systems, water quality, coastal regions, the ichtyo-stock, the eco-balance on food-dependable species and ultimately the human health. The current study leans emphasis on the meteorological-oceanographic analysis for the algae blooms in the North Aegean Sea, depending on the use of satellite derived data and optical color imaginary, concerning the area under study. The preliminary concern, along with secondary conclusions, among the variable instability of the local biogeochemical recycling of the phenomenon, the prolonged temporal time of its dispersion and its correlation with surface winds and meteo-characteristics, was verified. Data from Giovanni, that is a Web-based application developed by the GES DISC (Goddard Earth Sciences Data and Information Services Center) Interactive Online Visualization ANd aNalysis Infrastructure-NASA, where used for the analysis, in order for possible correlations between oceanographic and meteorological variables to be identified, such as: Chlorophyll-a concentrations, Precipitations rates, Euphotic Zone Depth, Colored Dissolved Organic Matter, Absorption coefficient for phytoplankton, Sea Level Pressure, Surface Pressure and Northwards wind component. / --