M.Sc. (Environmental Management) / In South Africa, there are practically no freshwater lakes. Therefore, exploitable water supplies are confined to rivers, artificial lakes behind dams, and groundwater. The many demands for water, and the erratic flow of most South African rivers, have led to the creation of artificial lakes and dams, i.e. impoundments on all the major rivers, in order to stabilise flow and therefore guarantee annual water supply. Cyanobacterial bloom formation in freshwater sources, such as rivers, lakes, dams and reservoirs are known to occur throughout the world. In South Africa, the occurrence of cyanobacteria has also been recorded with the best known being the bloom of the hyper-eutrophic Hartbeespoort Dam. In South Africa specifically, cyanobacteria are mostly seasonally driven. Species that are known to cause bloom formation are Microcystis sp., Anabaena sp., Oscillatoria sp. and Cylindrospermopsis sp. These species are known to produce cyanotoxins that cause health problems in animals and humans, but also produce taste and odour problems in drinking water, if not treated effectively. In most cases where cyanobacteria blooms have been known to occur, it also enters source water for drinking water purification plants. Because source water containing cyanobacteria and the effect it has on the consumer, environment and animals, it is thus important to identify the dominant algae species. Cyanotoxin drinking water guidelines must be developed and implemented and a management plan for the Water Treatment Plant must be produced, to ensure that the risk of human exposure to the cyanotoxins are minimised. The present study focuses on the Vaalkop Dam from which raw water is abstracted and treated by the Magalies Water Vaalkop Water Treatment Plant (MWVWTP) to produce potable water. The source water abstracted from the Vaalkop Dam can contain high numbers of cyanobacteria as well as cyanotoxins that must be removed by the MWVWTP during potable water purification to ensure compliance to water quality standards. The overall objective of the study is to investigate the occurrence of cyanobacteria and cyanotoxins in the Vaalkop Dam at the point where the source water is abstracted for drinking water purification.

PipX es una proteína única de cianobacterias identificada por su habilidad para interactuar de forma excluyente con PII y NtcA, dos reguladores clave implicados en la integración de señales de nitrógeno/carbono y energía, estableciendo un vínculo mecanístico entre ambos. Sin embargo, los datos recabados indican que el papel de PipX no se limita únicamente a esto, sino que parece formar parte de una red de señalización más amplia exclusiva de cianobacterias. La formación de los complejos PII-PipX no solo permite el secuestro de PipX, impidiendo la co-activación de NtcA, sino que favorece la formación de los complejos con el regulador transcripcional cianobacteriano PlmA. Esta interacción con PII afecta a la localización dinámica de PipX en respuesta al estado energético de la célula, limitando su actividad a condiciones de alta energía. Además, PipX está funcionalmente conectado con pipY, el gen aguas abajo que codifica a un miembro de la familia de proteínas PLPBP, universalmente distribuidas e implicadas en la homeostasis de la vitamina B6 y amino ácidos y, en humanos, epilepsia dependiente de vitamina B6. No solo PipX sería capaz de controlar a nivel traduccional la expresión de PipY, sino que ambos participarían en el control de la expresión génica y vías metabólicas comunes. Por último, el análisis de genomas cianobacterianos posiciona a PipX en una red de interacción con PipY y otras 4 proteínas con las que PipX podría tener una relación funcional.

Cyanobacteria are a unique organism, a bacterium that develop photosynthesis, thus it contains chlorophyll, a pigment commonly associated to algae. For this reason, cyanobacteria are also known as blue-green algae. One of the secondary metabolites of cyanobacteria is cyanotoxin, a substance which is hepatoxic, neurotoxic, and dermatoxic. The frequency and intensity of cyanobacterial blooms have been of increasing concern in the last decades for drinking water supply. There is a need to improve monitoring of cyanobacteria content at source water for drinking water supply and its indicators and correlation with other chemical, physical and biological parameters. This study aims to identify the potential cyanobacterial bloom risk in Lake Mälaren by determining the influential chemical and physical parameters using Random Forest in classification mode. The classification was done using the WHO Alert Level Frameworks and study cases for lakes in Sweden. The data used to model was downloaded from the website of the Swedish University of Agricultural Science. It comprises 33 monitoring stations from 1964 to 2020, 21 chemical parameters, including cyanobacteria biovolume and chlorophyll content. Given the heterogeneity of data, the monitoring stations were grouped into Clusters. Using the data, statistical, correlation, time series, and principal component analysis were performed. Through these methods, spatial, distribution and temporal analysis were obtained. Afterwards, several models were determined using Random Forest. However, the mean values of cyanobacteria distributed over time indicated a medium risk, the maximum values suggested high risk in several areas of the Lake. Maximum concentrations were present at the west and northeast of the Lake, where the major inflows from the Watershed are discharged. As the water flows through the basin, the concentration of cyanobacteria reduces by half, which suggested that the large and deep bays act as sedimentation ponds. A very high correlation was found between the Cluster 5 and 6, east and middle northeast of the Lake, respectively. Finally, the contributing factors identified after modelling cyanobacteria as target factor were chlorophyll, month, water temperature, oxygen content, transparency, NO2NO3N, TN/TP, Ca, Mg and Cl. / Cyanobakterier är unika organismer, bakterier som utvecklar fotosyntes, så de innehåller klorofyll, ett pigment som vanligtvis förknippas med alger. Av denna anledning är cyanobakterier också kända som blågröna alger. En av de sekundära metaboliterna av cyanobakterier är cyanotoxin, ett ämne som är hepatoxiskt, neurotoxiskt och dermatoxiskt. Frekvensen och intensiteten av cyanobakterieblomningar har varit ett ökande problem under de senaste decennierna för dricksvattenförsörjningen. Många vattenreningsverk mäter inte innehållet av cyanobakterier i vatten; medan andra kemiska, fysikaliska och biologiska parametrar mäts. Denna studie syftar till att identifiera den potentiella risken för cyanobakteriell blomning i Mälaren genom att bestämma de mest inflytelserika kemiska och fysikaliska parametrarna med hjälp av metoden Random Forest i klassificeringsläge. Klassificeringen gjordes med hjälp av WHO Alert Level Frameworks och olika studier av sjöar i Sverige. Data som användes för att modellera laddades ner från Sveriges Lantbruksuniversitets webbplats. Den omfattar 33 övervakningsstationer från 1964 till 2020, med 21 kemiska parametrar, inklusive cyanobakteriers biovolym och klorofyllhalt. Med tanke på heterogeniteten i data grupperades övervakningsstationerna i kluster. Med hjälp av data utfördes statistisk analys, korrelation, tidsserier och huvudkomponentanalys. Genom dessa metoder erhölls rumslig, distribution och tidsanalys. Efteråt bestämdes flera modeller med hjälp av Random Forest. Medelvärdena för cyanobakterier fördelade över tiden indikerade en medelrisk, medan maximivärdena antydde något annat. Maximala koncentrationer fanns i väster och nordost om Mälaren, där de stora inflödena från vattendelaren släpps ut. När vattnet rinner genom bassängen minskar koncentrationen av cyanobakterier till hälften, vilket tyder på att de stora och djupa vikarna fungerar som sedimentationsdammar. En mycket hög korrelation hittades mellan kluster 5 och 6, öster respektive mellan nordost om sjön. Slutligen var de viktigaste faktorerna som identifierades efter modellering av cyanobakterier som målfaktor klorofyll, månad, vattentemperatur, syrehalt, transparens, NO2NO3N, TN/TP, Ca, Mg och Cl.

This diploma thesis is focused on coagulation of humic substances (HS) and BSA (Bovine Serum Albumin) protein which was chosen as a representative of proteins contained in AOM (Algal Organic Matter). Additionally, possible interactions between these compounds were also investigated. It was found that the optimal dosage of coagulant is much higher for HS compared to BSA. The best removal of both HS and BSA was reached in slightly acidic pH range and it is attributed mainly to charge neutralization and adsorption mechanisms. The maximum removal rate was 70 % for humic substances and 80 % for BSA. The results show that BSA has a positive effect on coagulation of HS (resulting in a lower coagulant demand) and vice versa while BSA was removed more efficiently than HS. The existence of interactions between BSA and humic substantces during coagulation was demonstrated in certain pH ranges and it can occur even without the presence of coagulant. These interactions are highly dependent on pH that determines charge properties (and hence reactivity) of organic matters. Finally, the comparison of BSA and cyanobacterial proteins shows that their behavior during coagulation is similar. Consequently, BSA can be used as a model compound representing AOM proteins, especially their high molecular weight fraction....

A brown tide bloom of the pelagophyte Aureoumbra lagunensis caused significant impacts to north Indian River Lagoon (IRL) in 2012-2013, including seagrass die-offs, fish kills, and reduced growth and grazing of ecologically important bivalves. There is potential for another pelagophyte, Aureococcus anophagefferens, to expand into this system. Filtration rates (FR) of the pleated tunicate Styela plicata exposed to Aureoumbra lagunensis and Aureococcus anophagefferens were measured against exposure to a control alga (Tisochrysis lutea) in order to determine its potential use as a bioremediator against these harmful algal blooms (HABs). In addition, whether S. plicata might serve as a vector of HABs was studied by culturing fecal deposits. Short-term exposure to HABs significantly reduced FR, whereas long-term exposure indicates comparable cell removal compared to the control. Vector potential of S. plicata was inconclusive. Results warrant further research to determine whether S. plicata can acclimate or respond to HAB conditions over time. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

<p>Ispitano je prisustvo toksičnih cijanobakterija u različitim ekosistemima sa teritorije&nbsp;Republike Srbije i analizirane su negativne posledice koje mogu da prouzrokuju ovi&nbsp;mikroorganizmi. Formirana je Baza podataka cijanobakterija u Srbiji koja prilaže veliki broj bitnih&nbsp; i korisnih informacija iz preko 70 literaturnih izvora o prostiranju i učestalosti pojave cijanobakterija i njihovih toksina u periodu od 130 godina, kao i njihovih efekata na živi svet u vodenim ekosistemima, ali i &scaron;ire. Istraživana su 64 vodena ekosistema, uključujući reke, jezera, bare, kanale, ribnjake, akumulacije za navodnjavanje, akumulacije za snabdevanje vodom za piće i akumulacije sa drugom namenom, gde je najče&scaron;će cvetalo pet vrsta cijanobakterija i to:&nbsp;<em> Microcystis aeruginosa,&nbsp; Aphanizomenon flos-aquae</em>,&nbsp; <em>Planktothrix agardhii,&nbsp; Microcystis flos-aquae</em>&nbsp; i<em>&nbsp; Planktothrix rubescens</em>&nbsp; koje ujedno i &scaron;ire svoj areal rasprostranjenja na teritoriji Republike Srbije. U brojnim vodenim telima detektovani su mikrocistini i to u visokim koncentracijama.</p><p>Istraživanje vodenog ekosistema Ludo&scaron; sa teritorije Republike Srbije vr&scaron;eno je da bi se ustanovilo prisustvo i uticaj cijanobakterija i cijanotoksina na druge biljne i životinjske organizme u prirodnim uslovima. Trofički status jezera Ludo&scaron; najče&scaron;će je eutrofan, a cvetanje cijanobakterija kontinuirano jo&scaron; od 1970. godine. Tokom 2011. i 2012. godine&nbsp; vrste<em> Limnothrix&nbsp; redekei&nbsp;</em> i&nbsp;<em> Pseudanabaena&nbsp; limnetica</em>&nbsp; nađene&nbsp; u&nbsp; cvetanju. Detektovano je i prisustvo mikrocistina/nodularina i saksitoksina u biomasi i vodi, a mikrocistini su detektovani i u tkivu vodenih biljaka (trske&nbsp;<em> Phragmites communis</em>, rogoza&nbsp; <em>Typha latifolia</em>&nbsp; i ljubičastog lokvanja<em> Nymphaea elegans</em>) i ribi (<em>Carassius gibelio</em>) iz jezera Ludo&scaron;. Histolo&scaron;kim pregledom tkiva ribe&nbsp; pronađene su naizraženije promene u jetri, bubrezima i &scaron;krgama, a primećene su i na crevima.</p><p>Testiranjem biolo&scaron;kih lesnih pokorica sa teritorije Vojvodine nisu detektovani&nbsp;mikrocistini/nodularini, a nije detektovana ni toksičnost uzoraka. Pretpostavlja se da su koncentracije cijanotoksina ispod granica detekcije ili ih nema u testiranim biolo&scaron;kim lesnim pokoricama. Razvojem novih metoda i optimizacijom postojećih za detekciju cijanotoksina u biolo&scaron;kim lesnim pokoricama i drugim terestričnim ekosistemima potrebno je proveriti dobijene rezultate.</p><p>Proučavanjem svojstva 84 soja cijanobakterija iz NSCCC, koji potiču iz terestričnih i&nbsp;vodenih ekosistema sa teritorije Republike Srbije, dobijena je intracelularna toksičnost u eksponencijalnoj i stacionarnoj fazi rasta, kao i ekstracelularna toksičnost &nbsp;kod jednog soja koji potiče sa terestričnog ekosistema. Dobijeni su i pozitivni rezultati &nbsp;na prisustvo mikrocistina, nodularina ili/i saksitoksina kod 34,1% terestričnih i 55,5% vodenih sojeva koji potiču sa teritorije Republike Srbije. Rezultati ukazuju na&nbsp; potencijalnu opasnost pojave ovih&nbsp; mikroorganizama i njihovih toksičnih metabolita u različitim ekosistemima sa teritorije Republike Srbije.</p><p>Eksperimentalno je potvrđena akumulacija mikrocistina u račiću<em>&nbsp; Daphnia pulex&nbsp; </em>usled ishrane toksičnim sojem iz NSCCC, zbog čega upotreba ove vrste račića u izvođenju biolo&scaron;kih testova za testiranje prisustva cijanotoksina treba da se preispita.&nbsp; &Scaron;tavi&scaron;e, veliki broj jedinki dafnija (92,2%) koristio je istraživane sojeve iz NSCCC za ishranu, odnosno ishrana je bila moguća sa svim vodenim i sa gotovo 90% terestričnih sojeva, &scaron;to može poslužiti kao osnov za dalja istraživanja prevencije cvetanja.</p><p>S obzirom na mogućnost ishrane račića&nbsp;<em> Daphnia&nbsp; sp</em>. cijanobakterijama, kompleks&nbsp;<br />ribnjaka sa teritorije Republike Srbije kori&scaron;ćen je za istraživanje potencijalnog načina&nbsp;<br />prevencije pojave i cvetanja cijanobakterija u zavisnosti od pravovremenog uno&scaron;enja&nbsp;<br />pomenutog račića. Na osnovu koncentracije hlorofila&nbsp; a&nbsp; i trofičkog statusa,&nbsp; kvalitativne i kvantitativne analize cijanobakterija, toksičnosti vode&nbsp; i prisustva cijanotoksina mikrocistina/nodularina i saksitoksina, potvrđeno je smanjenje cvetanja cijanobakterija i drugih negativnih efekata u eksperimentalnim jezerima u odnosu na kontrolna. Ukoliko pak dođe do cvetanja i proizvodnje toksina&nbsp; ijanobakterija u vodenim ekosistemima, zbog ozbiljnost pojave i mogućih negativnih posledica po zdravlje ljudi, neohodno je uvesti postupke eliminacije ćelija&nbsp; cijanobakterija i njihovih &nbsp;toksina u praksu pri obradi&nbsp; otpadnih voda i preči&scaron;ćavanja vode iz povr&scaron;inskih akumulacija u Republici Srbiji.</p> / <p>The presence of toxic&nbsp; cyanobacteria in different ecosystems from the territory of the Republic of Serbia was analyzed as well as the negative consequences that may be causeed by these microorganisms. Serbian Cyanobacterial Data Base was formed where great number of important and useful information from over 70 literary sources regarding the distribution and frequency of cyanobacteria and their toxins over a period of 130 years, as well as their effects on wildlife in aquatic ecosystems, and beyond was presented. The study consisted of 64 aquatic ecosystems, including rivers, lakes, ponds, canals, irrigation reservoirs, reservoirs for drinking water supply and reservoirs with other purpose, where five species of cyanobacteria <em>Microcystis aeruginosa,&nbsp; Aphanizomenon flos-aquae,&nbsp; Planktothrix agardhii,&nbsp; Microcystis flosaquae&nbsp;</em> and&nbsp; <em>Planktothrix rubescens</em>&nbsp; frequently bloomed, and also expanded their area of distribution on the territory of the Republic of Serbia. In many water bodies microcystins were detected in high concentrations.</p><p>Research into aquatic ecosystem Ludo&scaron;, located on the territory of the Republic of Serbia, was performed in order to determine the presence and effect of cyanobacteria and cyanotoxins on other plant and animal organisms in natural conditions. Trophic status of&nbsp; the lake Ludo&scaron; was usually eutrophic, and cyanobacteria bloom is constant since 1970. During 2011 and 2012, the species <em>Limnothrix&nbsp; redekei</em>&nbsp; and&nbsp; <em>Pseudanabaena&nbsp; limnetica&nbsp;</em> were found in blooming. Presence of microcystins/nodularin and saxitoxin was detected in&nbsp; biomass and water, and microcystins were detected in tissues of aquatic plants (reed <em>Phragmites communis,</em> cattail&nbsp;<em>Typha latifolia&nbsp;</em>and royalblue waterlily&nbsp; <em>Nymphaea elegans</em>) and fish (<em>Carassius gibelio</em>) from the lake Ludo&scaron;. Histological examination of tissue showed most prominent changes in liver, kidney and gills, and alterations were also observed in the intestine.</p><p>Testing of the biological loess crust from Vojvodina showed no presence of microcystins/nodularin and toxicity of samples was not detected as well. It is assumed that cyanotoxin concentrations were below detection limit or are absent from the tested biological loess crusts. The development of new methods and optimization of existing ones for detection of cyanotoxins in biological loess crustsand&nbsp; other terrestrial ecosystems is necessary in order to revise obtained results.</p><p>Research of the properties from 84 strains of cyanobacteria from NSCCC originating&nbsp;from terrestrial and aquatic ecosystems from the territory of the Republic of &nbsp;Serbia, resulte d inintracellular toxicity in exponential and stationary growth phase, as &nbsp;well as extracellular toxicity of a strain originating from terrestrial ecosystems. The obtained results were positive for the presence of microcystins, nodularin and/or saxitoxin&nbsp; for 34.1% terrestrial and 55.5% aquatic strains originating from the territory of the Republic of Serbia. These results demonstrate the potential risk of occurrence of these microorganisms and their metabolites in different ecosystems from the territory of the Republic of Serbia.</p><p>Accumulation of microcystins in shrimp <em>Daphnia pulex</em>&nbsp;after feeding with toxic strain&nbsp;from NSCCC was experimentally confirmed, indicating that the use of this species of shrimp in biological tests which determine the presence of cyanotoxins needs to be revisited. Moreover, a large number of&nbsp;<em>Daphnia&nbsp; individuals </em>(92.2%) used the investigated strains of NSCCC for food, and the feeding was possible with all &nbsp;the water strains and nearly 90% of terrestrial strains, which can serve as a basis for further research of bloom prevention.</p><p>With regard to the possibility shrimp <em>Daphnia&nbsp;</em>sp. feeding with cyanobacteria, a&nbsp;complex of ponds from the territory of the Republic of Serbia was used to explore &nbsp;potential ways of prevention the occurrence and blooming of cyanobacteria, depending on the timely introduction of the aforementioned shrimp. Based on the concentrations of chlorophyll&nbsp; a&nbsp; and trophic status, qualitative and quantitative analysis of cyanobacteria, the toxicity of water and the presence of&nbsp; cyanotoxins microcystins/nodularin and saxitoxin, reduction in blooming cyanobacteria and other negative effects in the experimental lakes when compared to the control lakes was confirmed. If the blooming regardless occurres as well as production of cyanobacterial &nbsp;toxins in aquatic ecosystems, due to the seriousness of the phenomenon and the possible negative consequences for human health, it would be necessary to introduce &nbsp;procedures for the elimination of cells of cyanobacteria and their toxins into practice in waste water treatment and purification of water from surface reservoirs in the Republic of Serbia.</p>

Eutrophication is one of the primary factors causing harmful cyanobacteria blooms in freshwater lakes; climate change such as warmer temperature can potentially further increase both frequency and intensity of blooms. This study investigated the long-term changes in water quality and summer phytoplankton assemblages in Oswego Lake, OR, in relation to lake management practices (e.g., hypolimnetic aeration and alum treatments), as well as climatic and regional meteorological conditions. Both water quality and phytoplankton assemblages were sampled biweekly during summer seasons between 2001 and 2013. The concentrations of total phosphorus (TP), soluble reactive phosphorus (SRP) and total nitrogen (TN) decreased 66%, 93% and 31%, respectively, in response to the hypolimnetic aeration and alum treatments since 2005. The results of summer phytoplankton assemblages showed a 62% reduction of cyanobacteria biovolume and a switch from cyanobacteria dominance (2001-2005) to diatom and chlorophyte dominance (2006-2013). Cluster analysis identified four statistically different groups of summer phytoplankton assemblages (denoted Groups 1-4). Nonmetric multidimensional scaling analysis indicated that the four groups were associated with different water quality conditions. Group 1 occurred prior to hypolimnetic aeration and was primarily comprised of cyanobacteria, associated with water conditions of high nutrients and high primary production. Group 2, dominated by cyanobacteria and chlorophytes, occurred between hypolimnetic aeration and alum surface application. Group 2 was associated with turbid water conditions. Group 3 was dominated by diatoms, occurring after alum surface application. Group 4 included R-strategist phytoplankton that quickly respond to environmental changes, occurring in the years following alum injection, drawdown and inflow alum treatment. Both Group 3 and 4 were associated with reduced nutrients in the lake. The results demonstrated a strong temporal relationship between the long-term changes in water quality and summer phytoplankton assemblages and the lake management practices. The Pacific Decadal Oscillation (PDO) index, an El-Niño-like pattern of Pacific climate variability, showed a statistically significant correlation with the summer phytoplankton dynamics, while the multivariate ENSO index (MEI) and regional meteorological variables (air temperature, rainfall, wind speed, wind direction and solar radiation) were not significantly related to the changes of phytoplankton communities during the study period. In conclusion, the study results suggest that the lake management practices had strong effects on both production and community compositions of phytoplankton, and suggest the need for a future study on large-scale climate impacts on lake ecosystems and best management practice.

The investigation presented in this thesis examined the microbial and functional diversity of the meltwater ponds Fresh, Orange and Salt Ponds on the McMurdo Ice Shelf, near Bratina Island, Antarctica. These sites were chosen because of the ecological importance and absence of detailed characterisations of their diversity and function as part of Antarctica?s largest wetland. Particular focus was on cyanobacterial diversity, nitrogen fixation and secondary metabolite production. Using 16S rRNA gene and morphological analysis a large diversity of cyanobacteria (more than 22 phylotypes) was identified with high phylogenetic similarities (up to 99% sequence identity) to cyanobacteria from mats in other regions of Antarctica. In addition biogeographical distributions were identified including potentially endemic and cosmopolitan cyanobacteria. High salinities were also connected to the change and reduction of diversity. Lipid marker analyses were performed targeting hydrocarbons, ether-linked hydrocarbons, methylated fatty acid esters (FAME), wax esters, hopanols and sterols. Lipid biomarker profiles were similar to typical cyanobacteria dominated mats with major input from microorganisms including oxygenic and anoxygenic phototrophs, obligate aerobic and anaerobic heterotrophs that conduct the metabolic processes of fermentation, sulphate reduction, sulphate and iron-oxidation, methanogeneses. Signature lipids indicative of Chloroflexus and archaea, as well as branched aliphatic alkanes with quaternary substituted carbon atoms (BAQCs), were identified for the first time in Fresh, Orange and Salt Ponds. Based on nifH gene analysis, the nitrogen fixing diversity characterised in Orange Pond consisted of cyanobacterial Nostoc sp. as well as firmicutes, beta-, gamma- and delta-proteobacteria. Acetylene reduction assays and nifH gene RNA transcript diversity identified Nostoc sp. as a main contributor of nitrogenase activity in these ponds. Furthermore, analytical methods were used to identify the cyanobacterial secondary metabolites microcystins, although the genetic basis for this production and the toxin producer could not been identified. However non-ribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) genes were identified which could be the genetic basis for novel bioactives. The use of a multi-disciplinary approach synthesis and subsequent results significantly increased our understanding of the diversity and function of microbial mat communities in the unique meltwater ponds of the McMurdo Ice shelf, Antarctica.

The western embayment of Lake Ontario, Hamilton Harbour, is one of the most polluted sites in the Laurentian Great Lakes and in recent years has seen a reoccurrence of cyanobacterial blooms. This study uses a multidisciplinary approach to examine the presences of toxic Cyanobacteria in the harbour in order to gain insight into these recurrent blooms. Microscopic analyses of phytoplankton samples collected during the 2009 summer-fall sampling season from two locations within the harbour showed the spatial and seasonal diversity of the contemporary cyanobacterial community. Microcystis colonies relative abundances in relation to total algal numbers were estimated. The lowest and highest relative abundances of Microcystis in the phytoplankton population were 0.6% and 9.7%, respectively, and showed seasonal variability between stations. Fourteen cyanobacterial genera comprising six families and three orders were identified and for which the most abundant filamentous genera during the summer-fall sampling season were Planktothrix, Aphanizomenon and Limnothrix. Potential microcystin producers Microcystis, Planktothrix, Aphanizomenon and Dolichospermum were also present and during the sampling period Microcystis was recorded at both stations on all dates, however, its relative abundance was below 10 % throughout the study period. The composition and abundance of filamentous cyanobacteria were observed to be positively statistically correlated to water quality environmental parameters dissolved nitrates (NO3/NO2), dissolved inorganic carbon (DIC), and conductivity. Redundancy analysis (RDA) found that 53.35% total variance of Aphanizomenon was correlated to low water column NO3/NO2 and conductivity, and higher water column DIC. 58.13% of the relative abundance of Planktothrix was correlated to high concentrations of dissolved nitrates, while 51.69% of total variance of Limnothrix was correlated to higher DIC and lower water column dissolved nitrate concentrations. Information about past cyanobacterial communities was obtained from the sediment core analysis, using paleolimnological and modern molecular methods. The age of the 100.5 cm long sediment core retrieved from the deepest part of Hamilton Harbour was established to be 140 years (1869-2009), using the Constant Rate of Supply (CRS) 210Pb age model. This age was not sufficient to provide information of harbour’s environmental conditions, presence of the blooms, and triggers for their occurrence before European settlement in the area. Results of the HPLC analysis of fossil pigments indicated that the dominant members of the algal community have not changed over the 140 years and that cyanobacteria were regular members of the phytoplankton community. The composition of the major chlorophyll pigments indicated high presence of Chlorophyta and Bacillariophyta in the harbour at all times. The main algal groups identified on the basis of marker pigments presence, besides the Chlorophyta and Bacillariophyta, were the Dinophyta and the Cryptophyta. The presence of a scytonemin derivative, compound B, indicated that cyanobacterial blooms were occurring in past, before the first officially recorded blooms in the 1960s. Cyanobacterial pigments presence indicated that Cyanobacteria have been a regular but not dominant feature of Hamilton Harbour phytoplankton in the past. To our knowledge, this study is the first one examining fossil pigments from Hamilton Harbour. Results of the PCR-DGGE molecular analysis of 16S rRNA-V3 gene fragments from sedimentary DNA revealed the presence of thirteen cyanobacterial genotypes. The temporal change in the cyanobacterial community composition was indicated by the increasing number of species over time, from the oldest to the most recent sediment layers. The deepest sediment strata showed the lowest number (two bands) and intensity of bands. The most recent sediment layer had the greatest numbers (11) and intensity of bands. This increased diversity indicated changing environmental conditions in the harbour, primarily nutrient pollution and worsening water quality. Results of the PCR-DGGE molecular analysis of mcyE-AMT gene fragments showed that Microcystis aeruginosa and Planktothrix rubescens were two microcystin producers present in Hamilton Harbour over the last 80 years. The persistent presence and resilience of these two genera indicated a more serious and longer-term issue of toxic blooms than previously recognized. Historical records show that noticeable anthropogenic impact on Lake Ontario environment has been measurable since the 1780s, the first dramatic impact on the Lake Ontario watershed was evident from the mid1880s, the earliest evidence of eutrophication in the lake occurred between 1820 and 1850, while human induced environmental changes in Hamilton Harbour date back ca. 350 years. In the 1960s, cyanobacterial blooms were first officially recognized in the harbour and the lower Great Lakes. The present research is the first report of the mcyE module and AMT domain of microcystin genes being amplified from sediment of North American lakes, and showed that toxic Cyanobacterial have been regular members of Hamilton Harbour phytoplankton community for almost a century. This research considerably deepened the knowledge of the past toxic cyanobacterial blooms in Hamilton Harbour and their possible causes. It also showed that in the absence of historical records, both the PCR-DGGE method and the mcyE-AMT gene may be used for reconstruction of the past toxic blooms not only in the Laurentian Great Lakes, but also in other aquatic regions of the world impacted by toxic cyanobacterial blooms. Also, it demonstrated the utility of the combined molecular and paleolimnological analyses, which might become a useful tool in the determination of the bloom causes factors and in the mitigation of the future production of toxic blooms.

The investigation presented in this thesis examined the microbial and functional diversity of the meltwater ponds Fresh, Orange and Salt Ponds on the McMurdo Ice Shelf, near Bratina Island, Antarctica. These sites were chosen because of the ecological importance and absence of detailed characterisations of their diversity and function as part of Antarctica?s largest wetland. Particular focus was on cyanobacterial diversity, nitrogen fixation and secondary metabolite production. Using 16S rRNA gene and morphological analysis a large diversity of cyanobacteria (more than 22 phylotypes) was identified with high phylogenetic similarities (up to 99% sequence identity) to cyanobacteria from mats in other regions of Antarctica. In addition biogeographical distributions were identified including potentially endemic and cosmopolitan cyanobacteria. High salinities were also connected to the change and reduction of diversity. Lipid marker analyses were performed targeting hydrocarbons, ether-linked hydrocarbons, methylated fatty acid esters (FAME), wax esters, hopanols and sterols. Lipid biomarker profiles were similar to typical cyanobacteria dominated mats with major input from microorganisms including oxygenic and anoxygenic phototrophs, obligate aerobic and anaerobic heterotrophs that conduct the metabolic processes of fermentation, sulphate reduction, sulphate and iron-oxidation, methanogeneses. Signature lipids indicative of Chloroflexus and archaea, as well as branched aliphatic alkanes with quaternary substituted carbon atoms (BAQCs), were identified for the first time in Fresh, Orange and Salt Ponds. Based on nifH gene analysis, the nitrogen fixing diversity characterised in Orange Pond consisted of cyanobacterial Nostoc sp. as well as firmicutes, beta-, gamma- and delta-proteobacteria. Acetylene reduction assays and nifH gene RNA transcript diversity identified Nostoc sp. as a main contributor of nitrogenase activity in these ponds. Furthermore, analytical methods were used to identify the cyanobacterial secondary metabolites microcystins, although the genetic basis for this production and the toxin producer could not been identified. However non-ribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) genes were identified which could be the genetic basis for novel bioactives. The use of a multi-disciplinary approach synthesis and subsequent results significantly increased our understanding of the diversity and function of microbial mat communities in the unique meltwater ponds of the McMurdo Ice shelf, Antarctica.