Our knowledge of how Arctic freshwater ecosystems will respond to continued climate change and variability is fundamentally limited by logistical difficulties of such remote research, resulting in relatively sparse long-term baseline data on these systems. This research applies a unique paired-watershed approach (i.e., two similar, adjacent lakes and catchments) to help address these limitations, which provided an opportunity to identify how broad-scale factors are filtered or modified by site-specific characteristics. My first main objective was to document the seasonal hydrochemical variability of runoff and influences on lake chemistry. Both lakes appear to be relatively insensitive to seasonal hydroclimatic variability, largely because periods of high discharge were also characterized by lower concentrations of dissolved and particulate matter, but also because of the relatively long lake water turnover time that suggests the effects of climatic and environmental changes would be felt later in these systems than in lakes and ponds with smaller lake volumes. My second objective was to investigate spatial and temporal trends in the lake diatom communities in order to refine subsequent paleoenvironmental reconstructions. A critical aspect of this objective was testing how faithfully the whole lake diatom community was represented in deep lake surface sediments where sediment cores are routinely collected. Most differences between the two lakes were largely accounted for with micro-environmental conditions associated with the specific sampling location. Also, both lakes exhibited a degree of disconnection between littoral benthic and profundal zones that manifested as an under-representation of the benthic community in deep lake surface sediments, with implications for paleoenvironmental interpretations. Finally, I present a multi-proxy record of environmental conditions in adjacent lakes spanning the period from pre-industrial times. Biogeochemical records reflected major changes in lake primary productivity and terrestrial organic matter accumulation beginning prior to 1950 in both lakes, pointing to profound environmental changes that culminated with the establishment of an appreciable diatom community in both lakes in the 1980s. Differences in the timing of changes between the two lakes point to differing threshold capacities to external forcings, and suggest that East Lake’s response to post-industrial climate change is advanced compared to West Lake. / Thesis (Ph.D, Geography) -- Queen's University, 2011-10-26 09:34:01.144

Diatoms are a large and diverse group of algae which are distributed throughout the world in all types of aquatic systems and are one of the most important food resources in freshwater ecosystems. The need to sample diatoms arises from the necessity to know the history of the water quality. Diatom communities reflect the overall ecological integrity by integrating various stressors and as result provides a broad measure of their impacts. They are recognized as valuable organisms for bio assessment, due to their ease of identification, rapid life cycle and their visibility to the naked eye. Diatom communities provide interpretable indications of specific changes in the water quality Environmental gradients and assemblage composition in the Mnweni River catchment revealed that water chemistry, habitat structure, flow type and land use were the most important environmental factors for diatom assemblage composition in the Mnweni River. The results indicates that the diatom diversity and assemblage composition in the Mnweni River shows that changes in the water chemistry as well as organic pollution, but also indicate changes in the habitat character which is related to the water flow, river bank character and catchment land use. The diatom assemblages that were found at the sites are typical of clean or mildly enriched water conditions. The changing salinity in St. Lucia is the main physical factor that is driving the constant change in ecological conditions within the estuary. The changes in the diatom community structure in the estuarine system indicate the variable nature of the benthic communities under different salinity conditions. Contrary to the drought conditions that are being experienced, the diatom biomass did not show any significant changes or differences. This may be due to the rapid recovery ability that diatom communities exhibit in response to changes that are occurring in their environment. / Thesis (M.A.)-University of KwaZulu-Natal, 2006.

Marine productivity along the western Antarctic Peninsula (WAP) is declining. The WAP is site of the fastest regional warming in the southern hemisphere, and has experienced atmospheric and oceanic temperature increases leading to increased glacial inputs and reduced winter sea-ice cover. Sea-ice is a key link between climate and phytoplankton production, as melting sea-ice stratifies the water column and provides a source of micronutrients to surface waters. Reductions in ice cover have been accompanied by declining chlorophyll (chl; a proxy for phytoplankton biomass), and a shift to smaller cell sizes in phytoplankton communities. These reductions have implications for carbon drawdown and production available to higher trophic levels. However, little is known about phytoplankton shifts at the community level, as existing studies are based on satellite records and photosynthetic pigment analyses. To elucidate the nature of the changes within phytoplankton assemblages, high-resolution time-series data of diatom speciation are coupled to environmental data from five years in Ryder Bay (Adelaide Island, WAP). Long-term monitoring at this site by the British Antarctic Survey has identified a strong relationship between chl and water column stratification, and this study spans a wide range of physical conditions and biological production. By comparing high- and low-chl phytoplankton assemblages, this study investigates the mechanisms underlying productivity changes and the manner in which these changes impact nutrient cycling, drawdown and trophic transfer. The results presented here are the first full season in-situ records documenting differences in phytoplankton and diatom assemblages between highand low-chl years. The primary difference between chl conditions is a dramatic decline in diatom abundance. This analysis indicates that the mechanism producing low-chl seasons is less stratified surface waters, where light levels are much more variable than in high-chl years. Overall production is reduced, and small increases are seen in biomass of prymnesiophytes, which are better adapted to variable light. These shifts in phytoplankton composition and size structure are consistent with a southward propagation of observed climate change effects. Within the diatom community, changes in seasonal succession and a decrease in species richness occurred following low winter sea-ice. As the main component of high productivity and that most efficiently transferred to higher trophic levels, variation in diatom production due to environmental conditions is a mechanism to explain the observed WAP ecosystem changes and chl decline. Changes in phytoplankton stocks and composition also affect nutrient use, and here the use of silicon and iron (Si and Fe, respectively, which limit productivity in large areas of the Southern Ocean) is investigated. Seasonal Si budgets estimated from Si isotopes indicate a 40 – 70% decline in Si use between high-chl and intermediate-chl years, in agreement with other indices of productivity. The consequences of reduced demand and changing supply suggest future accumulation of Si in WAP surface waters. This should increase Si export away from the WAP shelf, which may act as a mechanism to enhance productivity and carbon drawdown in the wider Southern Ocean. Sources of Fe were assessed by direct measurement and naturally occurring radioisotopes of radium. These reveal significant inputs at the surface (due to glacial sources) and to deep waters (from shelf/slope sediments), which dominate supply to the surface mixed layer at different times. Iron availability and nutrient drawdown indicate that Fe is supplied to WAP surface waters in excess of biological demand. Projected changes to Fe sources and sinks indicate that continued warming will increase the WAP Fe inventory. As for Si, this excess Fe may also be advected away from the shelf, making this region a net Fe source to the Southern Ocean.

Mire pools – shallow water-bodies in peat-forming wetlands – are a characteristic feature of New Zealand’s subalpine and alpine landscapes (>1000 m a.s.l.), yet have been the subject of few biological studies to date, particularly of their algal communities. This research focuses on these subalpine systems, and on their diatom communities. Despite the established paradigm of ubiquitous dispersal in micro-organisms, recent taxonomic studies have confirmed a distinctive endemic component in the freshwater diatom flora of the New Zealand / Tasmania / East Australian region. In this study, I examined benthic diatom communities from >320 freshwater sites throughout New Zealand and showed that over 20% of species may be confined to this region. The endemic diatom species had highest densities in stable, unproductive environments, particularly in high-altitude mire pools and tarns. In most cases, non-endemic taxa coexisted with endemic species. This raised questions about (1) the special characteristics of mire pools and tarns (since endemism might be expected in areas that have unique environmental characteristics), and (2) the mechanisms that have allowed existing endemic taxa to withstand displacement by common cosmopolitan taxa, which, by definition, are successful colonisers. I addressed these questions using two years of data from four subalpine mire pools (Bealey Spur wetland, near Arthur’s Pass, South Island). Physico-chemical data showed that water chemistry of these pools may differ from that of many Northern Hemisphere mire systems with respect to the relationship between pH and dissolved ions (especially calcium). This may be due to a combination of high pH rainfall, high rainfall quantities that limit the acidification effects of humic substances, and possibly vegetation differences. Therefore, some endemic taxa may be confined to these habitats because of the characteristic properties of the pools. I investigated the effects of disturbances in these stable environments. In the largest pool endemic species were shown to decline as wind-induced substrate disturbance increased. Endemic species also declined in two pools following small-scale experimental substrate disturbances. In all cases, non-endemic species remained unchanged. The distinctive species Eunophora cf. oberonica was responsible for much of the observed decline in endemic species abundances, which was evidently due to destruction of their specialised habitat within the cyanobacterial mats that made up the pool substrates. I explained pool-specific responses of diatom communities to disturbances by drawing on recent theory of invasibility as an intrinsic environmental property. I further investigated species coexistence by examining several general patterns of interspecific coexistence described for macroscopic organisms (e.g., abundance – occupancy, abundance – persistence). Patterns in mire-pool diatom communities were generally similar to those in larger organisms, and did not differ with respect to geographical range size (endemics vs. non-endemics), except at the scale of single pools. At this scale, endemic taxa, in particular E. cf. oberonica, can persist as dominant species. All the community analyses were underpinned by detailed taxonomic studies, from which I assessed over 40% of the more common species in the pools to be either endemic or likely to be endemic. Two species occurring in the study area are formally described as new species. Overall, this work highlights the vulnerability of this hidden component of New Zealand’s biodiversity to disturbances and environmental changes.

Acid mine drainage (AMD) is a major environmental issue worldwide. On the West Coast of the South Island, New Zealand, numerous catchments receive AMD, with significant negative impacts on in-stream flora and fauna. Diatoms are commonly regarded as powerful biological indicators and may be found in high abundance in AMD-contaminated streams; however, relatively little work has been done on diatoms in mining environments in New Zealand. Initially, I conducted a survey of epiphytic diatom communities in 39 streams ranging from non-impacted reference streams to those severely impacted by AMD. Streams were assigned to one of four classes along an AMD gradient: circum-neutral reference, naturally acidic reference, moderately impacted, and severely impacted. There was a wide range in diatom taxonomic richness in reference and moderately impacted streams (8 – 33 taxa). Taxonomic richness was greatly reduced in severely impacted streams (1 – 5 taxa) at a threshold of pH 3.4 and was dominated by Pinnularia cf. acidophila (69 – 100% relative abundance). Community composition differed between circum-neutral reference, moderately, and severely impacted streams; however, naturally acidic and moderately impacted streams had similar diatom communities primarily composed of acid-tolerant Eunotia and Frustulia species. This indicated that diatoms are strongly structured by pH and able to tolerate moderate conductivity and metal concentrations without a corresponding shift in community composition. Survey data were then used to develop two diatom-based indices for streams impacted by AMD: a single Biotic Index and a Multimetric Index. While neither index was able to distinguish naturally acidic from moderately impacted streams, both indices successfully categorised streams as circum-neutral reference, moderately or severely impacted by AMD. These indices may be useful in assessing AMD impact on circum-neutral streams or in identifying when a stream has crossed a threshold from moderately to severely impacted by AMD. Diatoms would be especially useful as bioindicators of AMD if they respond rapidly to a change in mine discharge. To test this, mature algal biofilms were reciprocally transferred between circum-neutral reference streams and streams of varying degrees of AMD over a period of 13 days. Diatom mortality increased rapidly in the reciprocal transfer between reference and severely impacted streams. Reference communities resembled the ambient diatom community of severely impacted streams 13 days post-transfer. However, in the reverse transfer, a change in community composition was slow to occur. Diatoms respond faster to an increase in pollution than to pollution amelioration. Overall, results indicated that diatom communities may be a useful tool for monitoring the presence and magnitude of AMD in New Zealand streams.

Neurodegenerative diseases have been shown to correlate positively with an ageing population. The most common neurodegenerative diseases are amyotrophic lateral sclerosis (ALS), Parkinson’s disease and Alzheimer’s disease. The cause of these diseases is believed to be the interaction between genetic and environmental factors, synergistically acting with ageing. BMAA (β-methylamino-L-alanine) is one kind of toxin present in our environment and might play an important role in the development of those diseases. BMAA was initially isolated from cycad seeds in Guam, where the incidence of ALS/Parkinsonism-dementia complex among the indigenous people was 50 – 100 times higher than the rest of the world in the 1950’s. BMAA can induce toxic effects on rodents and primates. Furthermore, it can potentiate neuronal injury on cell cultures at concentrations as low as 10 µM. BMAA was reported to be produced by cyanobacteria, and could bio-magnify through the food chain. In this thesis, work was initially focused on the improvement of an existing analytical method for BMAA identification and quantification using liquid chromatography coupled with tandem mass spectrometry.  Subsequently, the refined method was applied to environmental samples for probing alternative BMAA producer(s) in nature and to seafood samples for estimation of human exposure to this toxin. In Paper I, a systematic screening of the isomers of BMAA in a database was performed and seven potential isomers were suggested. Three of them were detected or suspected in natural samples. In Paper II, a deuterated internal standard was synthesized and used for quantifying BMAA in cyanobacteria. In Paper III, Diatoms were discovered to be a BMAA producer in nature. In Paper IV, ten popular species of seafood sold in Swedish markets were screened for BMAA. Half of them were found to contain BMAA at a level of 0.01 – 0.90 µg/g wet weight. In Future perspectives, the remaining questions important in this field are raised.

Darbo tema: Šiaulių miesto Vijolės ir Kelmės miesto Kražantės upių vandens kokybės nustatymas ir palyginimas pagal titnagdumblių rūšinę įvairovę nustatant saprobiškumo indeksus (SI). Tyrimo tikslas buvo atlikti epifitinių ir epilitinių titnagdumblių analizę ir pagal jos rezultatus, apibūdinti upių Vijolės ir Kražantės vandens kokybę. Tikslui pasiekti pasirinkti uždaviniai: nustatyti titnagdumblių rūšių įvairovę Vijolės ir Kražantės upėse; apskaičiuoti tiriamųjų upių saprobiškumo indeksus; palyginti tyrimo rezultatus su ankščiau atliktų vertinimų rezultatais. Darbo objektu pasirinkta Vijolės upė tekanti per Šiaulių miestą ir Kražantės upė tekanti per Kelmės miestą. Mėginiai buvo imami 2013 metų pavasario, vasaros ir rudens sezonu, fiksuojami lugol‘o tirpalu, nusodinami naudojant centrifūgą. Mėginiai buvo mikroskopuojami naudojant 600x didinantį mikroskopą. Titnagdumbliai atpažinti spausdintais ir internetiniais šaltiniais. Saprobiškumo indeksui apskaičiuoti buvo naudojama metodika pagal LR ministro įsakymą, paviršinio vandens telkinių tyrimo metodiką pagal fitoplanktoną. Tyrimo metu buvo aptiktos ir atpažintos 52 titnagdumblių rūšys priskiriamos 2 klasėms ir 4 eilėms. Kražantės upė pasižymėjo didesne rūšių įvairove negu Vijolės. Abejose upėse dažniausiai pasitaikančios mėginyje rūšys buvo Navicula pusilla W. Sm., Navicula lanceolata (Ag.) Kütz., taip pat didžiausią masę mėginyje sudarė Navicula Bory genties rūšys. Daugiausia titnagdumblių Vijolės upėje buvo aptikta pavasarį... [toliau žr. visą tekstą] / The main thesis: the quality of water determination and comparison, according to species variety of diatoms, setting the saprobic indexes (SI) at Vijolė river in Šiauliai and Kražantė river in Kelmė. The purpose of the work is to analyse the diatoms, also to describe the quality of water in Vijolė and Kražantė rivers, using the rezults of these analysis. To achieve the goal, these tasks have been chosen: to determine the variety of diatoms in Vijolė and Kražantė rivers; to calculate the saprobic indexes of the rivers explored; to compare the rezults of investigation with rezults of evaluation, made earlier at the areas of investigation. The object of this work is Vijolė river in Šiauliai town, also Kražantė river in Kelmė town. The samples have been taken at the 2013 year‘s spring, summer and autumn seasons. They have been located using the lugol soak, precipitated using the centrifuge. The samples have been explored using the 600x microscope. The diatoms have been recognized using the information of printed and online sourses. The saprobic index was calculated using the methodology in accordance with an order of the LR Minister. The method of surface water bodies – according to phytoplankton. 52 species of diatoms, assigned to 2 categories and 4 ranges, have been detected at the time of research. Kražantė river characterized with higher variety of species, than Vijolė river. In both rivers, the most common species in sample have been Navicula pusilla W. Sm., Navicula... [to full text]

Water is a scarce and precious resource in South Africa. Not only is the quality and quantity of water available limited by climatic conditions but these resources are often impacted by domestic and industrial effluents, as well as run-off from agriculture. Monitoring the aquatic environment helps to determine the impact of various pollutants. Chemical monitoring, important as it is, can only at best give a "snapshot" of water quality at a particular moment in time. Biomonitoring in particular forms a vital part of monitoring programmes as it gives a time integrated reflection of a particular pollutant or group of pollutants on the ecosystem. Although diatoms have long been studied in South Africa, as well as being used in the past to indicate water quality, the current suite of bioindicator organisms used in this country has not until recently included diatoms, or any autotrophic organisms for that matter. This body of work is presented with the aim of facilitating the use of diatoms as bioindicators of water quality in South Africa. Methods for the collection, preparation and analysis of diatoms have been collated and standardized. A number of European and other indices have been tested in diverse localities for use in indicating recent and historical water quality. The impact of diffuse mine effluent on diatom community structure has also been discussed. A new species common in impacted waters (i.e. a potential indicator species for these conditions) has been described and a guide to the common diatoms of South Africa is presented which, it is hoped, will be of use to those who wish to commence with a study of South Africa's diatom flora. The results of this study show that diatom indices are successful in reflecting both current and past water quality in South Africa. This result justifies the inclusion of diatoms with the current suite of bioindicator organisms as well as in national monitoring initiatives such as the River Health Programme. Concluding comments underline the importance of using diatoms as indicators, not only of water quality, but also as indicators of aquatic microorganism biodiversity, or loss thereof. The need for continued research in the fields of diatom ecology and taxonomy is also highlighted. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2007.

Diatoms have been proven to be reliable indicators of water quality in many countries of the world particularly Europe. The potential use of diatoms as indicators of water quality in South Africa was tested in the studies in this document. This study evaluates the potential use of diatom based indices by testing it against a macroinvertebrate index (SASS 5) and evaluating the variation in the index scores of the two indices due to changes in chemical water quality and habitat. It was concluded that the diatom monitoring system performs well as bioindicator of water quality. It was also concluded that it should be used as a complementary system to the much used SASS 5 invertebrate index. This conclusion was made due to the fact that diatoms react more directly to changes in water quality than macroinvertebrates (SASS 5), and macroinvertebrates react more readily to changes in habitat than diatoms. A further part of the study was to assess whether aut-ecological or diversity based diatom indices performed best in South African conditions. This study found that the ecological indices were more sensitive to changes in water quality than the diversity indices. The diatom based indices that performed best as water quality indicators were the specific pollution sensitivity index (SPI) and the biological diatom index (BDI). A standard method for the sampling, preparation and enumeration for diatoms to be used for index score generation is also suggested to ensure the comparability of diatom based index data to facilitate use of such bio monitoring data for management purposes. The main focus of the study was to eliminate some of the obstacles for the use of diatoms as bio indicators of water quality in South Africa. It is believe that this aim has been accomplished in the study. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2008.

In a semi-arid country like South Africa, the availability and quality of water has always played an important part in determining not only where people can live, but also their quality of life. The supply of water is also becoming a restriction to the socio-economic development of the country, in terms of both the quality and quantity of what is available. Thus different monitoring techniques should be put in place to help inform the process of conserving this precious commodity and to improve the quality of what is already available. Water quality monitoring has traditionally been by the means of physico-chemical analysis; this has more recently been augmented with the use of biomonitoring techniques. However, since the biota commonly used to indicate aquatic conditions are not always present in wetlands; this study tested the use of diatoms as bio-indicators in wetlands. Diatom samples were collected from thirteen wetlands in the Western Cape Province, and cells from these communities were enumerated and diatom ?based indices were calculated using version 3.1 of OMNIDIA. These indices were useful for indicating water quality conditions when compared to the measured physico-chemical parameters. In addition, most diatom species found were common to those found in riverine environments, making the transfer of ecological optima possible. The objective of the study was to provide a preliminary diatom-based index for wetlands, however, given the relatively small study area and the strong bias towards coastal wetlands it was deemed inadvisable to construct such an index, instead several indices are recommended for interim use until further research that more comprehensively covers wetlands in South Africa has been conducted. It is thus the recommendation of this study that more data is collected for comparison to other wetlands and that in the interim, indices such as SPI be applied for routine biomonitoring of these environments. / Thesis (M.Sc. (Botany))--North-West University, Potchefstroom Campus, 2010.