A new range of multi-plankton biogeochemical models have recently been developed, designed to advance our understanding of the ocean carbon cycle to improve predictions of its future influence on climate. Synoptic measurements of the different phytoplankton communities are required to validate and ultimately improve such models. Measuring ocean colour from satellite is the only method currently available for synoptically monitoring wide-area properties of ocean ecosystems, such as phytoplankton chlorophyll biomass. Recently, a variety of bio-optical methods have been established that use satellite data to identify and differentiate between either phytoplankton functional types (PFTs) or phytoplankton size classes (PSCs). In this thesis, several of these techniques were evaluated against in situ observations (6504 samples) to determine their ability to detect dominant phytoplankton size classes (micro-, nano- and picoplankton). Results show that spectral-response, ecological and abundance-based approaches can all perform with similar accuracy. However, abundance-based approaches provide better spatial retrieval of PSCs. Based on insights into the abundance-based models, and by utilising a large pigment database, a new three-component model was developed which calculates the fractional contributions of three phytoplankton size classes (micro-, nano- and picoplankton) to the overall chlorophyll-a concentration. Using a globally representative, independent, coupled pigment and satellite dataset the model estimates fractional contributions with a mean accuracy of 9.2 % for microplankton, 17.1 % for nanoplankton and 16.1 % for picoplankton. The effect of optical depth on the model parameters was also investigated and explicitly incorporated into the model. Using the three-component model, the two-component absorption model of Sathyendranath et al. (2001) and Devred et al. (2006) was extended to three-component populations of phytoplankton, namely, pico-, nano- and microplankton. The new model infers total and size-dependent phytoplankton absorption as a function of the total chlorophyll-a concentration. A main characteristic of the model is that all the parameters that describe it have biological or optical interpretation. The three-component model performs better than the two-component model, at retrieving total phytoplankton absorption. Accounting for the contribution of pico- and nanoplankton, rather than the combination of both used in the two-component model, improved significantly the retrieval of phytoplankton absorption at low chlorophyll-a concentrations. The three-component model was applied to a decade of ocean colour observations. In the equatorial region of the Pacific and Indian Oceans, phytoplankton size class anomalies (% total chlorophyll-a) were highly correlated with indices of both the El Niño (La Niña) Southern Oscillation and the Indian Ocean Dipole. Furthermore, in these regions, micro- and nanoplankton size class anomalies were negatively correlated with anomalies of the sea surface temperature, sea surface height and stratification. Whereas, the picoplankton size class anomalies were positively correlated with these physical variables. Results from this thesis indicate that phytoplankton size class can be retrieved from Earth Observation with reasonable accuracy. It is recommended that such information can now be assimilated into multi-plankton biogeochemical models, or alternatively, verify them.

No description available.

One of today's major environmental issues is algal blooms linked to eutrophication of lakes and oceans. That is a result of anthropogenic influence with nutrient loads (including phosphorus) from agriculture and industry, which benefits primary production (phytoplankton). Studies have shown that phosphorus availability in the water column can be limited by liming, therefore could be a way to counteract eutrophication. This was tested in the agriculturally surrounded lake Tåkern in southern Sweden, which in its present state is an internationally important bird lake and therefore in several respects would be affected by eutrophication. The purpose of this study was to investigate whether liming would be a good solution to solve any future eutrophication problems in Lake Tåkern. Liming experiments were performed in mesocosms during April 2015 with a mixture of limestone and slaked lime. Quantity and diversity of plankton and water chemical variables were measured before and after liming. Moreover, samples of phytoplankton from a similar experiment conducted in July 2014 were analyzed. Liming did not show any effect on neither phyto- nor zooplankton when performed in spring of 2015. During summer of 2014, there was an increase in number of phytoplankton (ml-1 ) and chlorophyll in controls while the study showed constant levels in treated mesocosms. For zooplankton there was no significant effects of liming on neither quantity nor diversity. Results of this study suggest that liming is not the most appropriate method to resolve eutrophication in Lake Tåkern.

Atmospheric CO2 emissions are on the rise and are expected to reach 780 parts per million by the year 2100. Research investigating the impacts of increasing CO2 is a relatively new field and the response of phytoplankton communities is largely unknown, especially in coastal and freshwater ecosystems where no CO2 manipulation studies have completed. The present study attempts to encourage uniformity in methods utilized in CO2 perturbation studies and identifies changes in phytoplankton abundance in freshwater (James River) and coastal ocean (Atlantic, Cape Hatteras) sites. A novel bubbling method to manipulate pCO2 was compared with the classic method of acid addition in conjunction with laboratory and in situ experiments. The novel and classic methods were equally effective at manipulating carbonate chemistry to predicted levels. However, the laboratory experiment saw greater variation in both pCO2 levels and chlorophyll-a concentrations throughout the four-day incubation period. The results from the present study encourage use of the novel methodology in combination with in situ experimental setup to assess changes in phytoplankton communities as a result of pCO2 enrichment. This pairing will allow greater replication of small volume incubations without introducing new abiotic conditions such as temperature and light. Additionally this study found no significant treatment effect on phytoplankton communities in either freshwater James River or coastal Atlantic.

This study examined the extent to which zooplankton in the James River Estuary (Virginia, USA) exploit the available algal-food resources. Zooplankton abundance, community composition and grazing rates were assessed at three locations which included a site with high algal production (near the VCU Rice Center) and two sites where algal production was lower. Grazing rates were measured by determining the rate of phytoplankton decline (as chlorophyll a) during 48-hour incubation experiments in the presence and absence of zooplankton. Significant differences in zooplankton abundance were observed among the three sites, with the greatest average zooplankton density (434 ± 69 ind/L) occurring at the phytoplankton maxima. There were no significant differences in zooplankton filtration or ingestion rates among the three sites. The amount of chlorophyll a consumed was low at all sites (< 5%), suggesting that only a small proportion of primary production was directly passed to higher trophic levels. Low grazing rates were attributed to poor food quality owing to the presence of non-algal particulate matter and a predominance of cyanobacteria comprising the phytoplankton community. These findings are consistent with prior studies showing that cyanobacteria are a poor quality food source for zooplankton and that non-algal particulates may interfere with grazing rates. Further, this study lends support to the hypothesis that food quality is an important determinant of trophic transfer efficiency in aquatic food webs.

Empirical studies have shown that algal- and detrital-based food web components are coupled in many pelagic systems as algal carbon enhances bacterioplankton production and growth efficiencies. Such phyto-bacterioplankton coupling impacts carbon flow through plankton food webs, yet the extent of coupling is poorly understood in systems receiving large amounts of allochthonous carbon. To investigate this issue, bacterioplankton abundance (BA) and community composition were compared to chlorophyll a concentrations and phytoplankton production in the tidal-freshwater James River (VA). BA averaged 107 cells mL-1 and was significantly related to chlorophyll a, phytoplankton production, and DOC concentrations. Analysis of DOC quality using fluorescence spectroscopy revealed that the fulvic DOC fraction was dominated by allochthonous compounds. However, estimates of DOC C:N and DOC turnover rates indicated that DOC was more labile in the lower part of the study reach where BA was highest. T-RFLP analysis of 16s rDNA showed that bacterioplankton community composition significantly varied between the upper and lower portions of the sampling reach. These findings suggest that coupling of food web components is an important pathway affecting carbon cycling within the tidal-fresh water James River.

Our knowledge of how oil spills affect coastal environments is severely limited by the shortage of research that addresses the impact of these events on phytoplankton, the single most important group of organisms in the marine ecosystem. This scarcity of knowledge is mainly attributed to the absence of baseline data, preventing the comparison of pre- and post-spill populations. This unique study aims to identify how dinoflagellates and diatoms, the two major groups of phytoplankton in coastal marine environments, have been affected by the 1989 Exxon Valdez oil spill in Prince William Sound (PWS), Alaska. To do this, sedimentary records of dinoflagellate cysts, produced during a dinoflagellate's life cycle and preserved in the sediment, and biogenic silica, a proxy for diatom abundance, were analyzed prior to, during and after the oil spill. The analysis of two well-dated cores in PWS reveals marked increases during the oil spill in the concentrations of total cysts of the species Operculodinium centrocarpum sensu Wall and Dale, (1966) and Dubridinium spp. Total cyst concentrations doubled in core P-10 from 362 to 749 per g, while in core P-12 the increase was from 1175 to 1771 cysts g-1. During this peak in cyst concentrations, total concentrations were 3 and 2 standard deviations greater than the mean in cores P-10 and P-12, respectively. Dubridinium spp. showed a five and sevenfold increase in concentrations in cores P-10 (4 to 20 cysts g-1) and P-12 (16 to 110 cysts g-1), respectively, while O. centrocarpum sensu Wall and Dale, (1966) doubled in concentrations in the two cores (P-10: 117 to 276 cysts g-1; P-12: 268 to 495 cysts g-1). Biogenic silica values did not show significant changes throughout the cores, with values varying between 8% and 9% in core P-10 and 9.0% to 10.9% in core P-12. These changes lie within or very close to the standard deviation of the analyzed standards, suggesting that much of the changes could be analytical noise. The dinoflagellate cyst signals seen in this study are comparable to those seen as a result of nutrient enrichment in estuarine systems, suggesting that the 1989 Exxon Valdez oil spill and its remediation had a stimulatory effect on some taxa of cyst- producing dinoflagellates. This impact appears to be short-lived, with cyst concentrations returning to pre-spill levels within two years of the event. The lack of change in diatom abundance, on the other hand, suggest that diatom abundance remained relatively constant during the entirety of the sample period. / Graduate / 2020-07-10

As águas continentais existem em menor quantidade na superfície terrestre e apresentam grande importância para a sobrevivência dos seres vivos, motivo pelo qual a preocupação com sua qualidade aumenta a cada dia. As represas de Paraibuna e Paraitinga, localizadas no município de Paraibuna, São Paulo, totalizam 224 km2 de extensão de espelho d´água, com função atual de geração de energia elétrica. Com o objetivo de analisar a qualidade da água destas represas, o presente trabalho apresenta um diagnóstico físico, químico, bem como biológico, no qual foi utilizada a comunidade fitoplanctônica e cálculos de índices de qualidade. Foram realizadas quatro coletas em nove pontos de amostragem distribuídos ao longo das represas. As análises físicas e químicas da água demonstraram baixas concentrações de nutrientes como nitrato (média 0,42 +/- 0,23 mg.L-1) e fosfato (<0,05 mg.L-1). A maior parte dos metais e elementos-traço analisados mostraram-se dentro dos limites estabelecidos pela legislação federal. O elemento fósforo apresentou valores acima (média 0,0293 +/- 0,0153 mg.L-1) do estabelecido pela resolução CONAMA 357/05 (0,020 mg.L-1) em todos os pontos de amostragem no mês de maio, porém este fato pareceu não influenciar a densidade fitoplanctônica. Altos valores de oxigênio dissolvido e transparência, baixos valores de turbidez, condutividade e sólidos dissolvidos, pH próximo à neutralidade, em conjunto com altos índices de diversidade e baixos índices de dominância fitoplanctônica, com predomínio de clorofíceas, demonstraram que as represas estudadas ainda mantêm características de ambiente aquático preservado. Porém, a presença, ainda que em baixas densidades, de cianofíceas e a existência de atividades de monocultura e pecuária no entorno destas represas merecem especial atenção no que tange ao seu correto manejo para que não se tornem fatores prejudiciais à qualidade daquelas águas. / The inland waters are less on the Earth\'s surface and are extremely important for the survival of living things, why the concern for quality increases daily. The dams Paraibuna and Paraitinga, located in Paraibuna city, state of São Paulo, totaling 224 km2 of extension of water surface, with the current function of generating electricity. In order to analyze the water quality of these dams, this paper presents a diagnostic physical, chemical, and biological, which was used in the phytoplankton community and calculation of quality indexes. Four samples were taken at nine sampling points distributed along the dams. The physical and chemical analysis of water showed low concentrations of nutrients such as nitrate (mean 0,42 +/- 0,23 mg.L-1) and phosphate (<0,05 mg.L-1). Most metals and trace elements analyzed were within the limit established by federal law. The element phosphorus (mean 0,0293 +/- 0,0153 mg.L-1) is presented above the values established by CONAMA Resolution 357/05 (0,020 mg.L-1) on all sampling points in the month of May, but this fact did not seem to influence the phytoplankton amount. High levels of dissolved oxygen and transparency, low levels of turbidity, conductivity and dissolved solids, pH close to neutrality, together with high diversity and low dominance of phytoplankton, with a predominance of green algae, showed that the dams still retain features of aquatic environment preserved, which suffer little influence of anthropogenic factors. However, the presence, even at low densities, of cyanobacteria and the existence of plantations and livestock activities in the borders of these dams deserve special attention in terms of their correct management to not become harmful factors to the quality of those waters.

O Reservatório do Lobo, inserido no APA de Corumbataí, Município de Itirapina, faz parte do sistema Jacaré Guaçú. Este sistema, nas últimas décadas, tem sofrido impactos antrópicos significativos. Apesar deste fato, o trabalho desenvolvido (coletas mensais em nove estações no Reservatório do Lobo), com coleta de dados a respeito das variáveis físicas, químicas e biológicas, entre os meses de junho de 1999 a maio de 2000, demonstrou que este sistema ainda apresenta uma comunidade fitoplanctônica semelhante à observada em trabalhos anteriores. As mudanças nesta comunidade estão ligadas às funções de forças físicas que atuam no sistema, principalmente a temperatura e aos regimes hidrológicos. O reservatório pôde ser caracterizado em dois compartimentos: o inferior (mais profundo, com a coluna d\'água mais homogênea) e o superior (entrada dos principais afluentes, com bancos de macrófitas). A Bacillariophyceae Aulacoseira distans predominou nos três primeiros meses (junho a agosto de 1999), favorecida pela transparência e mistura da coluna d\'água. A espécie Aphanocapsa delicatissima (Cyanophyceae), nos meses posteriores (setembro a dezembro de 1999) substituiu em densidade aquela espécie, devido ao aumento da temperatura na coluna d\'água, às estratificações e à diminuição da concentração de nutrientes (especialmente fósforo). A espécie Cyclotella stelligera (Bacillariophyceae) predominou junto de Aphanocapsa delicatissima, em densidade (janeiro/2000), devido ao fato de ser eficiente competidora. A classe Chlorophyceae predominou em densidade no período chuvoso (fevereiro a março de 2000), representada pelos táxons Coelastrum reticulatum e Chlorela vulgaris. A Cyanophyceae Aphanocapsa delicatissima voltou a predominar em densidade nos dois últimos meses (abril a maio de 2000), em relação à densidade, devido ao aumento da insolação e, conseqüentemente, à ocorrências de períodos de estratificações durante o período de estudo. As espécies Aulacoseira distans, Coelastrum reticulatum e Aulacoseira granulata var. granulata foram os táxons predominantes em relação ao biovolume. Os táxons predominantes no período de estudo apresentaram a seguinte composição, quanto às suas estratégias de sobrevivência: R (Aulacoseira ditans) &#8594 CS (Aphanocapsa delicatissima) &#8594 CR (Cyclotela stellygera e Coelastrum reticulatum) &#8594 CS (Aphanocapsa delicatíssima) /CR (Coelastrum reticulatum). Essas estratégias indicam um ambiente em constante transição entre períodos de estratificação e mistura. Ao se analisar a composição fitoplanctônica por grandes grupos, a seqüência de transição destes mostra um ambiente tipicamente mesotrófico. / The Reservoir of the Lobo inserted in APA (protection environmental of area) of Corumbataí, Municipal district of Itirapina, is part of the system Jacaré Guaçú. This system, in the last decades, it has been suffering impacts significant antropics. In spite of this fact, the developed work (monthly collections in nine stations in the Reservoir of the Wolf), with collection of data regarding the physical variables, chemistries and biological, among the months of june of 1999 to may of 2000, demonstrated that this system introduces a community observed similar phytoplankton her in previous works. The alterations in the community are linked to the functions of physical forces that act in the system, mainly temperature and cycles hidrologics. The horizontal distribution was verified forming two compartments; the inferior (deeper and homogeneous) and the superior (the flowing principal entrance, with macrófitas banks). Aulacoseira distans (Bacillariophyceae) it prevailed in the first three months (June to August of 1999), favored by the transparency and it mixes of the column of water. Aphanocapsa delicatissima (Cyanophyceae), in the subsequent months (September to December of 1999) it substituted in density that species, due to increase of the temperature in the column of water, beddings and the decrease of nutritious (specially match). Cyclotella stelligera prevailed Aphanocapsa delicatissima near in density (January of 2000), should be this species efficient competitor. The class Chlorophyceae prevailed in density in the rainy period (February to March of 2000), represented by the taxon Coelastrum reticulatum and Chlorella vulgaris. Aphanocapsa delicatissima prevailed in density in the last two months again (April to May of 2000) in relation to density, due to the increase of the heatstroke and, consequently, to periods of beddings. During the study period, Aulacoseira distans, Coelastrum reticulatum and (Continuing) Aulacoseira granulata were predominant taxons in relation to the biovolume. The predominant taxons in the study period, presented the following composition, with relationship to your survival strategies: R (Aulacoseira distans) &#8594 CS (Aphanocapsa delicatissima) &#8594 CR (Cyclotela stellygera and Coelastrum reticulatum) &#8594 CS (Apahnocapsa delicatissima) /CR (Coelastrum reticulatum). These strategies indicate atmosphere in constant transition among bedding periods and it mixes and when analyzing the composition phytoplankton for great groups, the sequence of transition of these, display environmental typically mesotrophic.

Os reservatórios Billings e Guarapiranga integram uma das principais fontes de abastecimento público da cidade de São Paulo, suprindo água para milhões de pessoas. O aporte de nutrientes em corpos hídricos, advindos de efluentes domésticos e industriais, fertilizantes agrícolas, leva à eutrofização das águas propiciando condições ideais para a proliferação do fitoplâncton. Os objetivos do trabalho foram acompanhar a dinâmica da comunidade fitoplanctônica durante um ciclo sazonal e verificar a influência das variáveis físicas e químicas sobre a estrutura dessa comunidade. A maior densidade (ind.mL-1) da comunidade fitoplanctônica em ambos os reservatórios, foi representada por organismos das classes Chlorophyceae e Cyanobacteria, sendo a última dominante no reservatório Billings e abundante no reservatório Guarapiranga. Os fatores ambientais que interferiram na dinâmica da comunidade fitoplanctônica, em ambos os reservatórios, foram elevados valores de temperatura da água, pH e nutrientes. / Billings and Guarapiranga reservoirs are part of the main public water supply of São Paulo city, supplying water to millions of people. The nutrient input to hidric resources from domestic and industrial effluents, fertilizers causes eutrophication, thus creating ideal conditions to phytoplankton blooms to occur. The objectives of the present work were to follow up the phytoplankton community along one seasonal cycle and to identify the influence of physical and chemical parameters of the water on the community structure. The greatest phytoplankton density (ind.mL-1) in both reservoirs was due to individuals of Chlorophyceae and Cyanobacteria classes, the last being dominant in Billings reservoir and abundant in Guarapiranga reservoir, be it rainy or dry season. The environmental factors that interferred in phytoplankton dynamics were high temperature values, pH and nutrients, in both reservoirs.