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Ecology of phytoplankton

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... Los procariotas son organismos que no tienen una membrana nuclear por lo cual el ADN se encuentra disperso en el citoplasma, mientras que los eucariotas, sí tienen membrana nuclear y también organelos con membranas. Sus poblaciones están conformadas por organismos que pertenecen a diferentes grupos taxonómicos, incluyendo Cyanobacteria (algas verde-azules), Chlorophyta (algas verdes), Dinophyta (dinoflagelados), Bacillariophyta (diatomeas), Euglenophyta, Haptophyta, Prasinophyta, Chrysophyta, Cryptophyta y Raphidophyta (Pal y Choudhury, 2014;Reynolds, 2006). ...
... Dentro de los factores químicos que controlan su crecimiento se encuentra la disponibilidad de nutrientes (carbono, nitrógeno, fósforo, sílice y ciertos elementos que se encuentran en muy bajas concentraciones). La disponibilidad de nutrientes delimita la productividad primaria de los ecosistemas acuáticos, por lo cual su distribución espacial y temporal juega un papel fundamental en la dinámica del fitoplancton (Reynolds, 2006, Pal y Choudhury, 2014. ...
... Otros organismos importantes en los ciclos biogeoquímicos son los que tienen un impacto directo sobre el ciclo del sílice. Los "silicifi-Tabla 1. Clasificación del fitoplancton de acuerdo a la nomenclatura de tamaños propuesta por Sieburth et al. (1978) y resumida por Reynolds (2006 cadores", tales como las diatomeas, forman parte del microfitoplancton y contribuyen mayoritariamente a la producción primaria y biomasa durante los florecimientos de primavera en regiones templadas y polares. Las diatomeas aportan eficientemente a la exportación de carbono orgánico hacia el fondo marino, ya sea directamente a través del hundimiento de las células, o indirectamente al ser consumidas por los organismos pastoreadores. ...
... Phytoplankton, an ecological group of unicellular or colonial photosynthetic organisms adapted to live in apparent suspension in water masses (Reynolds, 2006), is a provider of many of the aforementioned services, in all the identified categories, to the ecosystems in which it lives and also to humankind. ...
... Among phytoplankton species significant variability exist in their growing rates (Reynolds, 2006). As an example, green algae and diatoms can grow much faster than toxin-producing cyanobacteria under adequate light and nutrient conditions (Naselli-Flores & Barone, 2011; but see also Lürling et al., 2013). ...
... Phytoplankton species are easily cultivated under lab conditions and culture collections of hundreds of species are existing since decades. This has contributed to significantly increase scientific knowledge in population and community ecology since many species with different ecological/physiological performances can be available in large numbers and successfully used to investigate the role of biological interactions as competition and predation under different environmental conditions (Reynolds, 2006) and testing general ecological concepts like the Intermediate Disturbance Hypothesis (Flöder & Sommer, 1999). Phytoplankton has been frequently used as a model to investigate, among others, population growth and assembly rules (e.g., Reynolds et al., 2002;Padisák et al., 2009;Rojo, 2021), adaptations to extreme environmental conditions (e.g., , relationships between predators and preys (e.g., Harvey & Menden-Deuer, 2012), and understanding the pathways to adaptation for living in suspension . ...
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Phytoplankton, the ecological group of microalgae adapted to live in apparent suspension in water masses, is much more than an ecosystem's engineer. In this opinion paper, we use our experience as phytoplankton ecologists to list and highlight the services provided by phytoplankton, trying to demonstrate how their activity is fundamental to regulate and sustain Life on our Planet. Although the number of services produced by phytoplankton can be considered less numerous than that produced by other photosynthetic organisms, the ubiquity of this group of organisms, and their thriving across oceanic ecosystems make it one of the biological engines moving our biosphere. Supporting services provided by phytoplankton include almost half of the global primary and oxygen production. In addition, phytoplankton greatly pushes biogeochemical cycles and nutrient (re)cycling, not only in aquatic ecosystems but also in terrestrial ones. In addition, it significantly contributes to climate regulation (regulating services), supplies food, fuels, active ingredients and drugs, and genetic resources (provisioning services), has inspired artistic and craft works, mythology, and, of course, science (cultural services), and much more. Therefore, phytoplankton should be considered in all respects a true biosphere's engineer.
... In aquatic ecosystem, they are the "fuel" of primary production and are often referred to as macronutrients in opposition to micronutrient that primary producers take up in a much smaller amount, and that essentially include Boron (Bh), Copper (Cu), Iron (Fe), Chloride (Cl), Manganese (Mn), Molybdenum (Mo) and Zinc (Zn) and others. In addition to these nutrients the Silicon dioxide (SiO2), also known as silica is also an important component of primary production (especially diatoms) in aquatic ecosystems (Reynolds, 2006). The several studies revealed that K, Ca, Mg, Na, Cl, are abundant in relation to relatively modest requirements, while Bh, Mn, Zn, Cu, Mo, Ba, Va occur as traces and are used as such. ...
... The several studies revealed that K, Ca, Mg, Na, Cl, are abundant in relation to relatively modest requirements, while Bh, Mn, Zn, Cu, Mo, Ba, Va occur as traces and are used as such. In contrast, a failure of supply to satiate demand of N, P, Fe, Si, or an over-enrichment of aquatic systems in N and P, has important ecological consequences (Reynolds, 2006). For these reasons, the rest of this section, mainly focus on N and P in aquatic ecosystems. ...
... However, it is less the amounts in which these elements are required that constrains growth than does the ease with which they are obtained. It is the demand relative to the supply of the bioavailable forms of nutrient that is ultimately critical, bearing in mind that a measurable presence is not a measure of bioavailability if the nutrient in question is not both soluble and diffusible and, so, assimilable by aquatic organisms (Reynolds, 2006). ...
Thesis
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Lake Nokoué is the largest and most productive lake of Benin. It supports the livelihoods of more than 500.000 people through fish production, manual lagoon sand mining and fertile floodplain for agriculture. The health of the lake, however, is jeopardised by eutrophication and excessive growth of the invasive water hyacinth. For an efficient management of eutrophication in Lake Nokoué, as for most of the tropical coastal lakes, the establishment of the main nutrient (nitrogen, phosphorus) budget is crucial. This requires a quantification of the inlet, the recycling and the outlet nutrients. Therefore, this research estimated and compared the amount of nitrogen (N) and phosphorous (P) contained in all the component of Lake Nokoué Ecosystem. Water quality parameters and nutrient contents of the sediments and the macrophytes (mainly water hyacinth) were monitored from November 2016 to October 2017. Water samples were collected every 30 days while sediments samples were collected during high water period to take into account the new sediment deposits brought by the lake’s tributaries. A spatio-temporal analysis of the parameters collected indicated that the water quality variations of Lake Nokoué is highly influenced by its hydrological regime. During the dry season, where the tributaries water inputs were lower than 50 m3/s, the salinity of the lake rose beyond 16.0 ppt in the whole lake under the influence of the tide from the Atlantic Ocean, and the nutrient concentration in the water column decreased below 0.5 mg/L of bioavailable N and 10 µg/L of bioavailable P. In opposite, during the rainy season, the tributaries water inputs increased beyond 385 m3/s and the subsequently, the salinity in the lake decrease below 0.1 ppt in the whole lake. The nutrient concentrations at this period when compared to the value recorded during the low water period were 4 times greater for bioavailable N and 10 times greater for bioavailable P. The water hyacinth in Lake Nokoué died off and sunk to the sediments during the low water period when salinity increased and reappeared when the salinity decreased below 6 ppt. This water hyacinth apparition cycle constitutes a potential source of internal nutrient (nutrient recycled) in the lake. In total, 1722 tons of inorganic N and 281 tons of inorganic P were recycle in 2016 by water hyacinth biomass. This represents approximately 5 – 7 times the amount of N and P that comes into the lake from the sum of sewage inputs and atmospheric depositions. Riverine nutrient was far greater than nutrient recycled by water hyacinth and was estimated at 13158 tons of total nitrogen and 588 tons of total phosphorous. However, an analysis of the spatio-temporal variation of the nutrient inputs and outputs revealed that 80% of riverine nutrient input was immediately flushed out from the systems, and could not be therefore responsible of the eutrophication of the systems. These results suggested that the water of poor quality (charged in nutrient) from the runoffs in the Ouémé catchment was flushed out from the lake into the Atlantic Ocean during the water recession period. The eutrophication of Lake Nokoué is mainly caused by nutrient release from the decomposition of sediment detritus. This process occurred during the low water period. The total internal nutrient load from the sediment was estimated at 24,908 tons of inorganic N and 3,489 tons inorganic P. A management option to reduce eutrophication could be a seasonal harvest of water hyacinth before they died and sink to the bottom. However, the contribution of water hyacinth removal compared to total loading from sediment detritus decomposition remains an open question because of the high uncertainties on the estimation of nutrient released from sediment. Further study should investigate the processes at the water – sediments interface for a better estimation of nutrient released from sediment. A reduction of the eutrophication will progressively increase the benefit that the population gain from fishery which was estimated at 42,158,750 USD per year, representing about 0.49% of the 2016 gross domestic product (GDP) of Benin. This study is the first to map water hyacinth coverage of Lake Nokoué in Benin. The study also provides data and maps of water quality and salinity, which are useful to understanding the seasonal dynamics of salt-water intrusion, relevant to many other aspects of lake ecology and fish production. More broadly, this study contributes significantly to understanding how an invasive macrophyte affects nutrient dynamics in an ecologically and economically important coastal lake ecosystem in West Africa. It uses an approach rarely used in aquatic ecology, which is to link data from remote sensing to the process-level understanding of nutrient uptake by water hyacinth and its production as it relates to wet-dry seasonality and salinity. This offers the possibility of monitoring large areas with fewer resources and time, which can be applied elsewhere. There is little information in general on these kinds of coastal systems in West Africa, though they often share common environmental problems and are similarly important to local livelihoods and economies.
... Worldwide, it is widely documented that eutrophication is one of the main factors controlling the increase in the frequency and duration of HABs (Reynolds, 2006;Heisler et al., 2008;Paerl and Huisman, 2008;Carey et al., 2012;Paerl and Paul, 2012;O'Neil et al., 2012;Huisman et al., 2018). Other regulatory factors of HABs are the availability of light, water temperature, and water residence time (Paerl and Huisman, 2008;Moss, 2009;Reichwaldt and Ghadouani, 2012). ...
... Gao et al. (2015) did report that "The sensitivity analyses indicated that a positive relationship existed between Chla and pH". This is in fact in most cases true, but the increase in pH is actually a consequence of productivity instead of its cause; and this concept is one of the basic paradigms of microalgae productivity (Margalef, 1983;Schneider and Campion-Alsumard, 1999;Wetzel, 2001;Reynolds, 2006;Stumm and Morgan, 2012). In the same regard, Zhao et al. (2019) simply reported threshold pH levels for microalgae growth. ...
... Both temperature and electric conductivity might exert a positive effect on microalgae growth, but BC2021 actually implies that the observed aquatic eutrophication is driven by temperature, electric conductivity, and pH. A review of undergraduate limnological textbooks would rapidly show otherwise (Margalef, 1983;Wetzel, 2001;Kalff, 2002;Reynolds, 2006). In stark contrast to the implications of BC2021, since the 1970s the international debates around eutrophication have focused on which nutrient, either phosphorus, nitrogen, or both, should be reduced in the basins to reverse the negative effects of eutrophication, both in lakes (e.g., Conley et al., 2009;Paerl et al., 2016aPaerl et al., , 2016bSchindler et al., 2016) and in rivers (McDowell et al., 2009;Dodds and Smith, 2016). ...
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A recent paper by Beretta-Blanco and Carrasco-Letelier (2021) claims that agricultural eutrophication is not one of the main causes for cyanobacterial blooms in rivers and artificial reservoirs. By combining rivers of markedly different hydrological characteristics e.g., presence/absence and number of dams, river discharge and geological setting, the study speculates about the role of nutrients for modulating phytoplankton chlorophyll-a. Here, we identified serious flaws, from erratic and inaccurate data manipulation. The study did not define how erroneous original dataset values were treated, how the variables below the detection/quantification limit were numerically introduced, lack of mandatory variables for river studies such as flow and rainfall, arbitrary removal of pH > 7.5 values (which were not outliers), and finally how extreme values of other environmental variables were included. In addition, we identified conceptual and procedural mistakes such as biased construction/evaluation of model prediction capability. The study trained the model using pooled data from a short restricted lotic section of the (large) Uruguay River and from both lotic and reservoir domains of the Negro River, but then tested predictability within the (small) Cuareim River. Besides these methodological considerations, the article shows misinterpretations of the statistical correlation of cause and effect neglecting basic limnological knowledge of the ecology of harmful algal blooms (HABs) and international research on land use effects on freshwater quality. The argument that pH is a predictor variable for HABs neglects overwhelming basic paradigms of carbon fluxes and change in pH because of primary productivity. As a result, the article introduces the notion that HABs formation are not related to agricultural land use and water residence time and generate a great risk for the management of surface waterbodies. This reply also emphasizes the need for good practices of open data management, especially for public databases in view of external reproducibility.
... Warming and low N levels may result in compositional changes with a positive selection for diazotrophic (N 2 -fixing) cyanobacteria (González-Madina et al., 2019;Wagner & Adrian, 2009) that might compensate for the relative N deficiency in the environment by atmospheric N 2 -fixation (Schindler, 1977;Schindler et al., 2008). However, several experimental and field studies have pointed out that N 2 -fixation by cyanobacteria cannot compensate for low N levels, since the N 2 -fixation is a metabolically expensive process (Reynolds, 2006;Camacho et al., 2003;Díaz et al., 2007;Moss et al., 2013) and, in addition, denitrification can exceed the N 2 -fixation rates (Paerl et al., 2020;Scott et al., 2019). Besides, many other studies have emphasized the relevance of N as limiting or co-limiting the primary production in shallow lakes (Havens et al., 1999;Elser et al., 2007;Paerl et al., 2016;Trochine et al., 2017). ...
... The response of algae production to temperature also depends on nutrient availability (e.g. Reynolds, 2006;Kosten et al., 2012;Liu et al., 2021;Verbeek et al., 2018) and, additionally, on the combined effect of warming and nutrient availability (Feuchtmayr et al., 2009;Jeppesen et al., 2009Jeppesen et al., , 2011. Accordingly, periphyton biomass decreased with warming at high N loadings, which coincides with other studies (Hao et al., 2020;Liu et al., 2021) but did not change at low N loadings. ...
... Periphyton can sequester, store and relocate large amounts of nutrients from the water and released by plants and these reserves can be used to compensate for nutrient imbalances (Carignan & Kalff 1982;Blumenshine et al., 1997;Havens et al., 1999). In contrast, phytoplankton can more effectively capture nutrient from the water (Riber & Wetzel, 1987;Reynolds, 2006) but they have a reduced storage capacity than the periphyton (Cattaneo, 1987;Blumenshine et al., 1997;Havens et al., 1999;Rodusky et al., 2001) and they are therefore more sensitive to prolonged periods of low nutrient conditions. Periphyton biomass was enhanced at low N and low phytoplankton biomass, which indicates that high N concentrations together with high P availability promote phytoplankton over periphyton. ...
Article
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Periphyton is a key primary producer in shallow lakes, sensitive to global warming and changes in nutrient balances. Reduced nitrogen availability due to accelerated denitrification at higher temperatures or in response to reduced N loadings aimed to reduce the eutrophication may affect periphyton biomass and composition, to compensate for the low N availability (e.g. promoting N2-fixing). We analysed periphyton responses to N decline in 12 eutrophic shallow lake mesocosms during one year of low N compared to high N, under three temperature scenarios: ambient, A2 IPCC scenario and A2 increased by 50%. We used two submerged macrophytes (Potamogeton crispus and Elodea canadensis) and artificial imitations of these as substrates for periphyton growth. Nitrogen decline increased periphyton biomass and induced compositional changes irrespective of season, plant type, and temperature. Periphyton biomass was negatively associated to phytoplankton and positively to plant complexity. Warmer scenarios negatively affected periphyton exclusively at high N loadings. Low N conditions were associated with lower periphyton taxonomic richness, lower N2-fixing cyanobacteria biovolume and increased biovolume of large-sized chlorophytes and non-N2-fixing cyanobacteria. Our results suggest that low N conditions promoted periphyton due to a more efficient use of nutrients and improved light conditions resulting from lower phytoplankton biomass and contrasting effects of temperature.
... Figure 2.1 shows the main features of the hydrological cycle. In this context, lakes interact directly with atmospheric water, surface water and groundwater (Reynolds 2006). Lakes and reservoirs represent 3.7% of the Earth's non-glaciated continental area (Verpoorter et al. 2014). ...
... It has a maximum at 4°C and decreases with higher (or lower) temperatures. Density gradients are usually extremely small over the water column, but have great importance (Reynolds 2006). Together with pressure gradients and turbulence, they determine the patterns of currents (Reynolds 2006). ...
... Density gradients are usually extremely small over the water column, but have great importance (Reynolds 2006). Together with pressure gradients and turbulence, they determine the patterns of currents (Reynolds 2006). Taking under examination a water column with a verticallly uniform temperature above 4°C, when a net positive heat flux is entering the water body, the surface layer gets heated and its density decreases. ...
Thesis
The ecological state of freshwater ecosystems worldwide has deteriorated along the past decades. Anthropogenic pressures have altered their physical and biogeochemical dynamics, acting both within their watershed and on the climatic conditions. Eutrophication and climate change contributed to the increase of algal blooms, and in particular of toxic cyanobacteria blooms , which currently constitute one of the main concern in the management of water resources.With the advance of urbanization, an increasing number of lakes are located in metropolitan areas. The high loads of nutrients and pollutants coming from the watershed often lead urban lakes to eutrophic conditions and cyanobacteria blooms, that cause bathing bans and restrictions for aquatic sports. Responsive surveys and long-term climate change impact studies are essential for the management of such sites, but rarely addressed.In this respect, modelling tools are of central importance to better understand the functioning of aquatic ecosystems, the factors triggering harmful algal blooms, and to support the management of water resources. However, aquatic ecological models are often complex and highly parametrized, and their implementation and calibration are challenging. Automated strategies for parameters calibration are available but are rarely applied. Furthermore, data from traditional periodical limnological survey do not allow to test the models on dynamics quicker than the span between two successive campaigns, and to thoroughly assess the uncertainty of their outcomes.In this context, this PhD thesis focuses on the use of deterministic models to reproduce the thermal dynamics and phytoplankton dynamics, notably cyanobacteria, in a small and shallow urban lake on different time-scales. To do so, two coupled hydrodynamic and biogeochemical three-dimensional (3D) models are implemented and analysed. The models used here are the FLOW and BLOOM modules from the Delft3D modelling suite, and the biogeochemical library Aquatic EcoDynamics coupled with the hydrodynamic model TELEMAC3D. The models are applied on Lake Champs-sur-Marne, an urban lake located in the East of Paris that suffers from strong cyanobacterial blooms and for which an extensive data set is available.This work aims to address in detail three strategic elements in lake ecosystem modelling:•The impact of climate change on the thermal regime of small and shallow lakes, and its relation to cyanobacterial growth. This is assessed through long-term 3D hydrodynamic simulations that allowed to hindcast the evolution of the study site during the past six decades.• The applicability and the benefits of automated calibration for complex biogeochemical models. This is done through an innovative methodology for parameter estimation: Approximate Bayesian Computation (ABC), tested here for the first time on a complex, highly-parametrized model.•The coupling and the feedbacks between hydrodynamic and biogeochemical models focusing on different time scales, and the importance of an extensive data set, that includes continuous high-frequency observations.The results show that the impact of climate change on small and shallow lakes can be severe, with consequences on the stratification dynamics and that thermal conditions increasingly favourable for cyanobacterial growth have established over time in the study site. This suggests that cyanobacteria dominance could become a widespread issue in the near future, if such trends are confirmed. Furthermore, this work proves that automated calibration strategies, and ABC in particular, can be profitably applied to complex physically-based biogeochemical models in order to improve their results over the period chosen for calibration. Eventually, this work also highlights the importance of an extensive data set to set-up a coupled 3D hydrodynamic / biogeochemical model, and analyse and exploit its results over different time scales.
... Size structures of phytoplankton communities were estimated two ways-as arithmetic (by geometric shapes) volume (V am ) of the algae cell in a sample and a coenocytic volume estimated as B/N (Vc, µm 3 ). Moreover, we considered the share of a small cell fraction (<20 µm, nannoplankton, according to: [47]) in the total phytoplankton abundance (%N) and biomass (%B). In addition, the dynamics of flagellar forms of phytoplankton were analyzed. ...
... This area became available for the normal functioning of planktonic or benthic algae, including representatives of the "shadow" flora, mainly from the diatoms. Avoidance by diatoms of well-lit surface layers of highly transparent water bodies (both marine and fresh) is a well-known fact in the ecology of phytoplankton and diatoms [47] (the phenomenon of a deepened maximum of photosynthesis). ...
... The size structure of the phytoplankton community, as an important indicator of water ecosystem eutrophication [47], reflected the predominance of nannoplankton components in phytoplankton communities of Lake Klyuchik. The proportion of small-celled organisms increased in communities with more pronounced dominance and decreased with an increase in species diversity and evenness. ...
Article
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Gypsum karst lakes are unique water ecosystems characterized by specific habitat conditions for living organisms, including phytoplankton species, as primary producers and mediating biogeochemical cycles in the water bodies. Studies of diversity and structure of phytoplankton communities can be used to identify the specific and typical lake features and plan basin-wide monitoring. The aim of this research was to analyze the structural variables of algocenoses in the small gypsum karstic Lake Klyuchik (Middle Volga basin), atypical for the subzone of mixed coniferous and deciduous forest zone high values of water mineralization (brackish water) and low temperatures. The lake has two water areas, connected by a shallow strait (ecotone zone) and differing from each other in the chemical compositions and physical properties of the water. A total of 133 species of phytoplankton with prevalence percentages of Bacillariophyta (46%), Chlorophyta (24%), and Ochrophyta (11%) were found; α-diversity varied from 4 to 30 specific and intraspecific taxa per sample. According to Spearman's correlation coefficients, the diversity indices (Shannon, Pielou, Simpson) were mainly determined by the number of dominant species. The uniquely high (up to 130 g/m3) biomass of phytoplankton was noted in the ecotone, on the border between the water column and the bottom. The formation of mono- and oligo-dominant nannoplankton diatom communities with a predominance of the rare species Cyclotella distinguenda Hustedt was demonstrated there. The roles of flagellate algae and cyanobacteria were found to be less significant.
... Los procariotas son organismos que no tienen una membrana nuclear por lo cual el ADN se encuentra disperso en el citoplasma, mientras que los eucariotas, sí tienen membrana nuclear y también organelos con membranas. Sus poblaciones están conformadas por organismos que pertenecen a diferentes grupos taxonómicos, incluyendo Cyanobacteria (algas verde-azules), Chlorophyta (algas verdes), Dinophyta (dinoflagelados), Bacillariophyta (diatomeas), Euglenophyta, Haptophyta, Prasinophyta, Chrysophyta, Cryptophyta y Raphidophyta (Pal y Choudhury, 2014;Reynolds, 2006). ...
... Dentro de los factores químicos que controlan su crecimiento se encuentra la disponibilidad de nutrientes (carbono, nitrógeno, fósforo, sílice y ciertos elementos que se encuentran en muy bajas concentraciones). La disponibilidad de nutrientes delimita la productividad primaria de los ecosistemas acuáticos, por lo cual su distribución espacial y temporal juega un papel fundamental en la dinámica del fitoplancton (Reynolds, 2006, Pal y Choudhury, 2014. ...
... Otros organismos importantes en los ciclos biogeoquímicos son los que tienen un impacto directo sobre el ciclo del sílice. Los "silicifi-Tabla 1. Clasificación del fitoplancton de acuerdo a la nomenclatura de tamaños propuesta por Sieburth et al. (1978) y resumida por Reynolds (2006 cadores", tales como las diatomeas, forman parte del microfitoplancton y contribuyen mayoritariamente a la producción primaria y biomasa durante los florecimientos de primavera en regiones templadas y polares. Las diatomeas aportan eficientemente a la exportación de carbono orgánico hacia el fondo marino, ya sea directamente a través del hundimiento de las células, o indirectamente al ser consumidas por los organismos pastoreadores. ...
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Estas obras contienen registros de aproximadamente 15,000 especies marinas incluidas en 40 fillos de microorganismos. Compilaciones de especies en diferentes regiones del golfo sugieren diferencias regionales en la diversidad. Uno de los retos principales que enfrenta el estudio de las comunidades marinas en el Golfo de México es su gran extensión geográfica, que abarca aproximadamente 1, 577, 000 km2. La plataforma continental del golfo se extiende desde la costa hasta 200 m de profundidad, en donde inicia el talud continental. Las especies marinas están adaptadas a habitar en condiciones ambientales particulares, y la presencia de un amplio intervalo de profundidades se refleja en una alta variedad de habitats que se caracterizan por comunidades marinas específicas. Cerca de la superficie, las condiciones ambientales como la temperatura y salinidad son muy variables y la señal estacional es muy marcada como conseciencia de la interacción entre el océano y la atmósfera.
... Phytoplankton with high species richness, high reproduction rate and very short life cycle enable the examination of both short-term and long-term effects. Therefore, the alterations in phytoplankton species composition and biomass in water body reflect a changing environment and indicate the trophic status [1]. ...
... Actually, various physico-chemical parameters are responsible for controlling phytoplankton growth and reproduction. These factors could include the impact of both environmental conditions and human stressors, such as variations in nutrients concentration, the combined effect of land use/land management and urbanization [1,2]. ...
Article
Phytoplankton community and their correlation with environmental factors were investigated in the Dong Nai River. Higher diversity was observed in dry season with the dominance of diatom. Environmental variables were different between upper and lower sections. Phytoplankton metrics and the nutrient concentration characterized a pollution gradient along the river. Nutrient levels and turbidity governed the distribution of phytoplankton structure in the river.
... This factor can be explained by the significant presence of algal biomass in the water column, since this parameter is the most common form. easy to assimilate by phytoplankton (Reynolds, 2006;Rangel et al., 2012). It is also possible to see that, in Period II, the high values of chlorophyll-a (Chla) are in agreement with the low values of SRP, demonstrating that its development was made possible by a greater availability of nutrients, resulting in a rapid capture of the same (Reynolds, 2006). ...
... easy to assimilate by phytoplankton (Reynolds, 2006;Rangel et al., 2012). It is also possible to see that, in Period II, the high values of chlorophyll-a (Chla) are in agreement with the low values of SRP, demonstrating that its development was made possible by a greater availability of nutrients, resulting in a rapid capture of the same (Reynolds, 2006). ...
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In semiarid regions is recurrent water depletion of some reservoirs during periods of prolonged drought, intensifying eutrophication. After water depletion events, new waters arrival and the trophic state improvement is expected. Therefore, the aim of this study was to evaluate the change of the trophic state after the reservoir’s drying due to a prolonged drought in the Brazilian semiarid region. It is expected that the trophic state improves after the water renewal by decreasing nutrient concentrations and algal biomass. This study was performed in a tropical, semiarid reservoir (Cruzeta Reservoir, Brazil), and was carried out during two different periods: 2012 (beginning of the prolonged drought) and 2019 (after the drying and reflooding). Analyses of Wilcoxon test and principal components analysis (PCA) were used to identify significant changes and patterns between the periods studied. The studied periods differed significantly (p < 0.05) with regard to maximum depth, pH, dissolved oxygen, conductivity, turbidity, inorganic and organic suspended solids, total phosphorus, soluble reactive phosphorus, nitrate and chlorophyll a. The hydrological regime of the Brazilian semi-arid region, governed by the prolonged drought period (from 2012 to 2019), contributed to significant changes in the volume and water quality in Cruzeta reservoir, increasing nutrients and algal biomass, intensifying the symptoms of eutrophication. Thus, contrary to the hypothesis of this study, despite the reflooding after the drought period, a worsening in the trophic state of the reservoir from eutrophic to hypereutrophic was observed.
... These results are reasonable for low-nutrient conditions, where Microcystis spp. are superior competitors for resources compared to other phytoplankton taxa (Reynolds 2006). For instance, Microcystis sp. has the ecophysiological traits of high affinity and storage for phosphorus (Carey et al. 2012). ...
... The increasing relative abundance of cyanobacteria decreased phytoplankton species richness, Shannon index, and community evenness, while increased RUE in Lake Taihu (Table 1). In addition, the abundance of dominant cyanobacteria has stronger positive effects on RUE than other rare species (Reynolds 2006), which thus weakens the effect of species richness on RUE. The mechanism behind our results is supported by findings in the terrestrial ecosystems, where the identity and abundance of dominant species, rather than species richness, drive the biodiversityecosystem functioning relationship (Winfree et al. 2015;Jones and Magurran 2018). ...
Article
The dependency of resource use efficiency (RUE) on phytoplankton diversity is key for understanding aquatic ecosystem responses to eutrophication and climate change. Here, we studied RUE of nitrogen (RUEN), phosphorous (RUEP), or silicate (RUESi) and the associated abiotic and biotic explanatory variables in 3,016 samples collected from 30 sites in Lake Taihu during 2005‐2017, covering cyanobacteria‐ and macrophyte‐dominated regions. We further examined spatiotemporal dependencies of RUE on phytoplankton taxonomic and functional diversity and their underlying drivers. The annual mean RUEsi of each site exhibited an overall increasing temporal trend, while that of RUEN and RUEP displayed U‐shaped patterns over the study period. RUE was affected by nutrients and water temperature, and also was related to phytoplankton diversity in terms of Shannon diversity and functional dispersion diversity. Interestingly, RUE showed negative spatial dependencies on phytoplankton diversity. These negative spatial dependencies had decreasing temporal trends for RUEN and RUESi, while a hump‐shaped pattern for RUEP. The dependencies were generally related to spatial environmental mean of nutrients, such as nitrate and total phosphorus. Furthermore, RUE showed negative temporal dependencies on phytoplankton diversity mainly in the cyanobacteria‐dominated region, while it was occasionally positive in the macrophyte‐dominated region. These temporal dependencies were driven primarily by temporal environmental stability of nutrients, such as dissolved total nitrogen. Collectively, the direction and strength of spatiotemporal dependencies of RUE on phytoplankton diversity were influenced by nutrient status and stability. These findings can be considered in future environmental management plans for long‐term sustainability of ecosystem functioning under global climate change.
... Low levels of turbulence in the mesocosms may also lead to lower populations of negatively buoyant phytoplankton. Similarly, increased sedimentation of particulate organic matter in the quiescent water of the mesocosm tanks may not only lead to less nutrient recycling but also improved underwater light climate (Ostrom et al., 1998;Reynolds, 2006). Lastly, allelopathy from V. natans may also inhibit the growth of phytoplankton (Xian et al., 2006;Wang et al., 2011;Jiang et al., 2019). ...
Article
Urban lakes are important natural assets but are exposed to multiple stressors from human activities. Submersed macrophytes, a key plant group that helps to maintain clear-water conditions in lakes, tend to be scarce in urban lakes, particularly when they are eutrophic or hypertrophic, and their loss is linked, in part, to impaired underwater light climate. We tested if enhancing the underwater light conditions using light-emitting diodes (LEDs) could restore submersed macrophytes in urban lakes. Twelve mesocosms (1000 L each) were each planted with tape grass (Vallisneria natans) and monitored over three months (22 August-7 November), using a control and three artificial light intensity treatments (10, 50, and 100 µmol m-2 s-1). Compared with the control, the high light treatment (100 µmol m-2 s-1) had higher leaf number, maximum leaf length, and average leaf length (3.9, 5.8, and 2.8 times, respectively). Shoot number, leaf number, leaf dry mass, root dry mass, and photosynthetic photon flux density in the highlight treatment were significantly greater than the control, but root length and phyto-plankton chlorophyll a were not related to plant growth variables and were low in all treatments. Periphyton chlorophyll a increased significantly with the plant growth variables (i.e., shoot number, leaf number, and maximum leaf length) and was high in the light treatments but did not hamper the growth of the macrophytes. These results indicate that LED light supplementation enables the growth of V. natans under eutrophic conditions , at least in the absence of fish as in our experiment, and that the method may have potential as a restoration method in urban lakes. Lake-scale studies are needed, however, to fully evaluate LED light supplementation under natural conditions where other stressors (e.g., fish grazing) may need to be controlled for successful restoration of urban lakes.
... Although we have observed equivalent proportions of total nitrogen (TN) between falling and low water periods, the higher total phosphorus (TP) was found in low waters, with concentration values eight times higher when compared to the high water. Phosphorus is one of the key limiting nutrients for phytoplankton primary production and growth (Reynolds 2006). In the Amazon, shallow lakes are strongly affected by sediment resuspension in low water period with a complete circulation of the water column (Bonnet et al 2005;Moreira-Turcq et al. 2013), where the critical values for the mixing zone are cited as 2 m for resuspension events, bringing TP available in the water column (Fosberg et al. 2017). ...
Article
The Amazon floodplains are complex systems influenced by the annual hydrological regime with an effect on the structuring of physical, chemical and biological processes. Thus, we evaluated the relationship of environmental factors with the composition and variation of functional groups based on morphology (MBFG) during the hydrological year in an Amazonian floodplain lake, with monthly sampling (2013 to 2014). We used analysis of variance (ANOVA) and Kruskal–Wallis to show differences in physicochemical variables between hydroperiods. We performed permutation analysis of variance (PERMANOVA) to assess the dissimilarity of morphofunctional groups between hydroperiods and also of environmental data between the months of the study and RDA redundancy analysis to assess the relationship between MBFGs and environmental data. It was registered 101 taxa distributed in eight taxonomic categories and was grouped into 5 MBFGs (III, IV, V, VI and VII), with Chlorophyceae (31 taxa) and Cyanobacteria (27 taxas) with the higher number of taxa. Furthermore, there was a dominance of Cyanobacteria in the total biovolume, which form blooms (MBFGs III and VII) during the periods of falling and low water in lake, influenced mainly by the reduction in the availability of light and an increase in temperature. In another scenario, the dominance of MBFGs V and VI occurred during periods of rising and high water with association with carbon compounds, rainfall, SRP and NO2. Thus, our results demonstrate that the availability of light, the concentration of nutrients and temperature were the most important variables for the morphofunctional structuring of phytoplankton in aquatic system.
... We considered species richness as the total number of taxa registered in each quantitative sample. The algae species were grouped in two size groups: nanoplankton (2-20 µm) and microplankton (21-200µm) according to Reynolds (2006). ...
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Aim We aimed to characterize the structure of the phytoplankton community and identify the main environmental factors driving the community in five reservoirs constructed in the region of the high Paraná River. Methods The phytoplankton and environmental variables were collected at the lacustrine region of the reservoir, between November 2013 and November 2014, with interval between collections ranged from 3 to 6 months. The richness and biomass of the phytoplankton community were measured as a response to the spatial and temporal environmental variability. Data from environmental variables was analyzed by Principal Component Analysis (PCA). Non-Metric Multidimensional Scaling Analyzes (NMDS) were performed on the richness and biomass data of the phytoplankton community. Results We identified 80 taxa distributed in 11 taxonomic classes, from which Cyanobacteria and Chlorophyceae were best represented. We did not observe significant temporal variation for either environmental variables or attributes of the phytoplankton community, which may be related to the prolonged drought in this period in the Brazilian Southwest. Higher phytoplankton richness and biomass were found in the Três Irmãos (Tiete River), reservoir located in the most anthropized basin in the country. Cyanobacteria and dinoflagellates dominated the biomass in all reservoirs during the studied period. The Ilha Solteira, Jupiá and Porto Primavera reservoirs showed a tendency to decrease in the values of phytoplankton richness and biomass, and the reservoirs built in series in the Paraná River probably have strong interdependence, according to the CRCC concept. Conclusions Spatial variation in phytoplankton attributes was influenced mainly by the position occupied by the reservoir in the hydrographic basin, water retention time (RT) and nutrient concentrations in each reservoir.
... Phytoplankton account for <1% of the photosynthetic biomass on Earth, but are responsible for nearly 50% of global net primary production and are the primary energy source for aquatic ecosystems (Field et al., 1998;Kakouei et al., 2021). They can respond quickly to environmental changes due to their small body size, high growth rates and short life-cycle (Sommer, 1989;Reynolds, 2006). Thus, phytoplankton are an important biological indicator of lake water quality and ecosystem functioning. ...
Article
The response of a community to environmental changes is either linear or non-linear, so that they can be investigated approximately by linear or nonlinear models. At community level, redundancy analysis (RDA) and canonical correspondence analysis (CCA), and Mantel test and Generalized Dissimilarity Modelling (GDM) are two pairs of fundamental multivariate approaches. Thus, it is necessary to determine how they are used for a given group of communities or a metacommunity. In the present study, we explored the applications of the two pairs of commonly used multivariate methods for the analysis of tropical phytoplankton communities. Phytoplankton were collected from 60 tropical reservoirs in southern China at two distinct regions and two hydrological seasons. Because of a short environmental gradient, response of phytoplankton communities to the environmental gradients was first explored with linear models: distance-based redundancy analysis (db-RDA) and Mantel test. Then, CCA and GDM were further applied to recognize the nonlinear relationship between phytoplankton community variation and environmental changes, and to detect the significant environmental and/or spatial variables. Our results strongly suggest that the combination of db-RDA and GDM provides a highly effective tool to uncover the linearity and nonlinearity in community responses and the important associated environmental and spatial variables, which were significantly different between flooding and dry seasons.
... Third, the nutrient concentrations during the rainy period were generally higher than those during the post-rainy period (Table 1), but we observed that the Chla concentrations were much lower than those in August 2020 (p < 0.001, Table 1). Heavy rainfall shifts the river to the flood period, resulting in a higher water velocity, while rapid flushing due to high water velocity is not conducive to the growth of cyanobacteria (Reynolds et al., 2006;Zou et al., 2020). As evidenced by the incubation experiment (Fig. 6), the presence of algae can significantly promote methanogenesis, which may be an important explanation for the lower CH 4 concentration in July 2020 compared with that in August 2020. ...
Article
Urban rivers play a vital role in global methane (CH4) emissions. Previous studies have mainly focused on CH4 concentrations in urban rivers with a large amount of organic sediment. However, to date, the CH4 concentration in gravel-bed urban rivers with very little organic sediment has not been well documented. Here, we collected water samples from an oxic urban river (Xin'an River, China; annual mean dissolved oxygen concentration was 9.91 ± 1.99 mg L⁻¹) with a stony riverbed containing very little organic sediment. Dissolved CH4 concentrations were measured using a membrane inlet mass spectrometer to investigate whether such rivers potentially act as an important source of atmospheric CH4 and the corresponding potential drivers. The results showed that CH4 was supersaturated at all sampling sites in the five sampling months. The mean CH4 saturation ratio (ratio of river dissolved CH4 concentration to the corresponding CH4 concentration that is in equilibrium with the atmosphere) across all sampling sites in the five sampling months was 204 ± 257, suggesting that the Xin'an River had a large CH4 emission potential. The CH4 concentration was significantly higher in the downstream river than in the upstream river (p < 0.05), which suggested that human activities along the river greatly impacted the CH4 level. Statistical analyses and incubation experiments indicated that algae can produce CH4 under oxic conditions, which may contribute to the significantly higher CH4 concentration in August 2020 (p < 0.001) when a severe algal bloom occurred. Furthermore, other factors, such as heavy rainfall events, dissolved organic carbon concentration, and water temperature, may also be vital factors affecting CH4 concentration. Our study enhances the understanding of dissolved CH4 dynamics in oxic urban rivers with very little organic sediment and further proposes feasible measures to control the CH4 concentration in urban rivers.
... Cyanobacteria represent a very diverse group of primary producers with a great capacity to adapt to wide environmental gradients and limited resources (light and nutrients) (Margalef, 1978;Reynolds, 2006;Agawin et al., 2007;Paerl et al., 2019;Wurtsbaugh et al., 2019). Cyanobacteria blooms are predicted to become more frequent in the context of climate change and eutrophication (Paerl & Huisman, 2009), and several cyanobacteria traits provide competitive advantages in the set of Anthropocene transformations (O'Neil et al., 2012). ...
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Laguna del Sauce is a eutrophic shallow lake and the second drinking water source in Uruguay. This ecosystem suffers recurrent blooms of potentially toxic nitrogen-fixing cyanobacteria, mostly during summertime. Here we analyze environmental drivers and potential impacts of blooms of the toxic cyanobacteria Raphidiopsis raciborskii in Laguna del Sauce from 2003 to 2020, and assess its effects on governance and biomonitoring. We registered three blooms of R. raciborskii, in 2004, 2015, and 2020, the last two expressed saxitoxin (lack of toxicity information for 2004). The 2015 bloom occurred in autumn, reaching an absolute biovolume of 104 mm3 l−1, and had high saxitoxin concentrations (up to 9.8 μg l−1) which continued to be detected even after the bloom collapsed. This was the first saxitoxin register in this ecosystem and drastically affected the drinking water supply. After this massive bloom, a monitoring program was established which continues up to date. The 2020 bloom also occurred in autumn and lasted until winter; it was of lower magnitude (up to 6.3 mm3 l−1) and had lower saxitoxin concentration (up to 0.9 μg l−1) compared to the 2015 bloom. Blooms of R. raciborskii were associated with a combination of persistent low water level, low water color, and high water transparency, conditions that rarely coincide in this ecosystem. Hence, the programs which started after the 2015 bloom, allowed better characterizing the environmental drivers of R. raciborskii blooms in Laguna del Sauce. Furthermore, these implied adapting the ecosystem management and water treatment strategies, and strengthening of academia—stakeholders’ interactions.
... Lake Trasimeno is in fact an area of exceptional value for flora and fauna richness and for species biodiversity and it is part of a Natural Regional Park and of two Natura 2000 sites (IT5210018 and IT5210070). It is important in such kind of waterbodies to characterize the diurnal variation of phytoplankton abundance, by means of a proxy such as Chl-a concentration, because algal blooms can grow and dissipate within a few days [85]. In addition, the seasonal phytoplankton phenology and distribution are influenced by this short-term variability [86]. ...
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The monitoring of water bio-physical parameters and the management of aquatic ecosystems are crucial to cope with the current state of inland water degradation. Not only does water quality monitoring support management decision making, it also provides vital insights to better understand changing structural and functional lake processes. Remote sensing has been widely recognized as an essential integrating technique for water quality monitoring, thanks to its capabilities to utilize both historical archive data for thousands of lakes as well as near-real time observations at multiple scales. To date, most of the applications developed for inland water have been based on multispectral and mid to coarse spatial resolution satellites, while a new generation of spaceborne imaging spectroscopy is now available, and future missions are under development. This review aims to present the exploitation of data gathered from two currently orbiting hyperspectral sensors (i.e., PRISMA and DESIS) to retrieve water quality parameters across different aquatic ecosystems, encompassing deep clear lakes and river dammed reservoirs.
... Conductivity-temperature-depth (CTD) measurements were collected with an SBE-19plus profiler. Seawater for biogeochemical analyses was collected with a 5 L Niskin bottle at different depths (2,10,20,50,75, 100 m), according to the bathymetry of each station (PYR 135 m, AKR 130 m, VAS 55 m). ...
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Alterations in phytoplankton biomass, community structure and timing of their growth (phenology), are directly implicated in the carbon cycle and energy transfer to higher trophic levels of the marine food web. Due to the lack of long-term in situ datasets, there is very little information on phytoplankton seasonal succession in Cyprus (eastern Mediterranean Sea). On the other hand, satellite-derived measurements of ocean colour can only provide long-term time series of chlorophyll (an index of phytoplankton biomass) up to the first optical depth (surface waters). The coupling of both means of observations is essential for understanding phytoplankton dynamics and their response to environmental change. Here, we use 23 years of remotely sensed, regionally tuned ocean-colour observations, along with a unique time series of in situ phytoplankton pigment composition data, collected in coastal waters of Cyprus during 2016. The satellite observations show an initiation of phytoplankton growth period in November, a peak in February and termination in April, with an overall mean duration of ~4 months. An in-depth exploration of in situ total Chl-a concentration and phytoplankton pigments revealed that pico- and nano-plankton cells dominated the phytoplankton community. The growth peak in February was dominated by nanophytoplankton and potentially larger diatoms (pigments of 19’ hexanoyloxyfucoxanthin and fucoxanthin, respectively), in the 0–20 m layer. The highest total Chl-a concentration was recorded at a station off Akrotiri peninsula in the south, where strong coastal upwelling has been reported. Another station in the southern part, located next to a fish farm, showed a higher contribution of picophytoplankton during the most oligotrophic period (summer). Our results highlight the importance of using available in situ data coupled to ocean-colour remote sensing, for monitoring marine ecosystems in areas with limited in situ data availability.
... Dinophytes were strongly and positively affected by both temperature and DEP during the stratification period June-September, the latter likely reflecting that these motile algae can migrate between a nutrient-rich layer (meta-/hypolimnion) and the surface to harvest light [40]. The stability of the stratification is higher under warmer conditions and often at a shallower depth [4,9]. ...
Article
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Cross-latitude studies on lakes have a potential to predict how global warming may cause major changes in phytoplankton biomass and composition, e.g., the development of favourable conditions for cyanobacteria dominance. However, results from these studies may be influenced by biogeographical factors, and the conclusions may, therefore, not hold when considering local response patterns. We used monthly monitoring data from 504 lakes in Denmark—a small and homogeneous geographical region—to establish empirical relationships between key phytoplankton groups and a set of explanatory variables including total phosphorus (TP), total nitrogen (TN), lake mean depth (DEP) and water temperature (TEMP). All variables had strong effects on phytoplankton biomass and composition, but their contributions varied over the seasons, with TEMP being particularly important in June–October. We found dominance of cyanobacteria in terms of biomass and also an increase in dinophytes biomass at higher TEMP, while diatoms and chlorophytes became less important. In May, however, the TEMP effect on total phytoplankton biomass was negative, likely reflecting intensified zooplankton grazing. Our results suggest that biogeographical effects are of minor importance for the response patterns of phytoplankton to temperature and that substantial concentration reductions of TN and TP are needed in eutrophic lakes to counteract the effect of the climate change-induced increase in TEMP.
... Analysis of both the inorganic dissolved (N:P 13.4 ± 3.92) and seston (C:N 4.8 ± 1.8) nutrient composition suggested the system was slightly N limited prior to the MUE. Silica (Si) is another important nutrient for diatoms [78,79], with averaged ratios of 2:1 (N:Si) and 7:1 (Si:P). The low N:Si ratio further suggests that N is the primary limiting nutrient for diatom growth, and the high Si:P ratio suggests that Si is likely not a limiting nutrient. ...
Article
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Harmful algal blooms (HABs) are increasing globally in frequency, persistence, and geographic extent, posing a threat to ecosystem and human health. To date, no occurrences of marine phycotoxins have been recorded in Mozambique, which may be due to absence of a monitoring program and general awareness of potential threats. This study is the first documentation of neurotoxin, domoic acid (DA), produced by the diatom Pseudo-nitzschia along the east coast of Africa. Coastal Inhambane Province is a biodiversity hotspot where year-round Rhincodon typus (whale shark) sightings are among the highest globally and support an emerging ecotourism industry. Links between primary productivity and biodiversity in this area have not previously been considered or reported. During a pilot study, from January 2017 to April 2018, DA was identified year-round, peaking during Austral winter. During an intense study between May and August 2018, our research focused on identifying environmental factors influencing coastal productivity and DA concentration. Phytoplankton assemblage was diatom-dominated, with high abundances of Pseudo-nitzschia spp. Data suggest the system was influenced by nutrient pulses resulting from coastal upwelling. Continued and comprehensive monitoring along southern Mozambique would provide critical information to assess ecosystem and human health threats from marine toxins under challenges posed by global change.
... Phytoplankton is the most diverse group of photosynthetic microorganisms, and are adapted to live partly or continuously in open seas, lakes, reservoirs, ponds, and river waters, where they contribute part or most of the organic carbon available to pelagic food webs (Reynolds, 2006;Barsanti and Gualtieri, 2006;Klais et al., 2017;Santana et al., 2017;Lee et al., 2018;Affe et al., 2019;Beak et al., 2019;Bhaskar et al., 2020). They are the agents of primary production and the key to the base of food chains and food webs, directly providing nutrients to zooplankton, fishes, and other aquatic animals (Shubert, 1984;Millman et al., 2005;Moser et al., 2017;Abonyi et al., 2018;Kim et al., 2019a;Bom and Colling, 2020). ...
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As a multinational river, the Naf River flows into the Bay of Bengal in the Indian Ocean, between the Cox's Bazar district of Bangladesh and the Rakhine state of Burma. In a multidisciplinary approach, several experiments were carried out to understand the seasonal diversity of the phytoplankton community structure. A total of four layers of water was sampled from four depths in the Naf River during monsoon (September) and winter (December) of 2016. 41 species of phytoplankton were identified, and 3 different dominant groups (Cyanobacteria, Diatoms, and Dinoflagellates) were found. Diatoms and cyanobacteria alone were found to be most prevalent. Higher species diversity was observed in the monsoon season, with Synedra sp. (1.84×10 5 cells L-1 , 18.76%) and winter with Microcystis sp. (1.41×10 5 cells L-1 , 17.74%), respectively. In monsoon, NO3-N and PO4-P were both higher than winter (450.9 and 34.4 µg L-1 , respectively) especially, at downstream Naf River. Moreover, high diversity indexes (richness) of phytoplankton were recorded along with these estuarine stations. Significant correlations (P<0.01) of nutrients with phytoplankton may liable behind these scenarios. An analysis of principal component analysis (PCA) and linear regression supported this correspondence. In the monsoon season, the concentration of Chlorophyll-α reached the highest level (165 µg L-1) at a depth of 1.5 m, in Station-D. Cluster analysis based on the nutrient content of the Naf River was found two (upstream and downstream) mentionable zones during the winter and monsoon seasons. The results of the present study indicate that estuarine downstream areas are more productive than upstream areas of the Naf River at the southwest coastal zone of the Bay of Bengal.
... Fitoplankton merupakan mikroalgae yang hidup melayang-layang di air dengan kemampuan renang yang rendah atau tidak ada sama sekali dan merupakan produsen dalam rantai makanan pada ekosistem perairan (Reynolds, 2006;Suthers dan Rissik, 2009). Pada semua ekosistem laut di dunia dengan perkiraan 95% produksi primer di laut berasal dari fitoplankton (Nontji, 2006). ...
... Minimum DSi required for diatom growth was shown to be 0.1 mg L −1 (3.57 μM Si) [52]. Early research reported that the monosilicic acid concentrations of 8.1-81.0 ...
Article
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In order to increase shrimp production and minimize detrimental environmental impacts of aquaculture, the maintenance and regulation of the growth and composition of phytoplankton communities and nutritional balance are critical. Silicon (Si) is an essential nutrient for diatoms and other types of microorganisms, but the information about the Si impact on their growth is extremely scarce. Monosilicic and polysilicic acids were tested in several shrimp cultivation systems in Jiangsu Province, China. In pond waters, the concentrations of monosilicic and polysilicic acids were sharply reduced by 36-95% and 35-75%, accordingly, as compared with those in supply water sources. The microbial cell abundance was strongly dependent on monosilicic acid. In laboratory experiments, monosilicic acid added to pond water or probiotic solutions at 1- and 2-mM Si had a significant positive effect on cell abundance. Over three days, the concentrations of monosilicic acid decreased by 81 to 91% in pond water and by 11 to 24% in probiotic solution. In probiotic solutions, the degree of polymerization of silicic acid was more intensive than that in shrimp pond waters. The data obtained demonstrates the importance of systematic studies related to the functions of Si in shrimp aquaculture.
... The strong seasonal cycle within the environmental parameters was also apparent in the results of PERMANOVA ( Table 2). The segregation between the diatoms (on the left in Figure 4B) and the dinoflagellates (on the right in Figure 4B) niche positions is typical of the species seasonal succession [78]. In the EEC, the dominance shift in the succession from the diatoms to the dinoflagellates is caused by the decline of silicate concentration, which becomes a limiting factor for diatom growth. ...
Article
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Global environmental change modifies the phytoplankton community, which leads to variations in their phenology and potentially causes a temporal mismatch between primary producers and consumers. In parallel, phytoplankton community change can favor the appearance of harmful species, which makes the understanding of the mechanisms involved in structuring phytoplankton ecological niches paramount for preventing future risk. In this study, we aimed to assess for the first time the relationship between environmental conditions, phenology and niche ecology of harmful species Phaeocystis globosa and the complex Pseudo-nitzschia along the French coast of the eastern English Channel. A new method of bloom detection within a time-series was developed, which allowed the characterization of 363 blooms by 22 phenological variables over 11 stations from 1998 to 2019. The pairwise quantification of asymmetric dependencies between the phenological variables revealed the implication of different mechanisms, common and distinct between the taxa studied. A PERMANOVA helped to reveal the importance of seasonal change in the environmental and community variables. The Outlying Mean and the Within Outlying Mean indexes allowed us to position the harmful taxa niche among the rest of the community and quantify how their respective phenology impacted the dynamic of their subniches. We also discussed the possible hypothesis involved and the perspective of predictive models.
... Bioturbation on one hand releases nutrients stored in the sediment into water column; on the other hand, it directly increases non-algal turbidity of water and thus, leads to light limitation (Adámek and Maršálek, 2013). This may be the reason why, despite the high concentration of available nutrients, the phytoplankton biomass in the very shallow Eastern Continental lakes remains far below the theoretical maxima, which should be around 300-600 μg/L chl-a, assuming a water column no deeper than two metres (Reynolds, 2006). ...
Article
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Nutrient targets based on pressure-response models are essential for defining ambitions and managing eutrophication. However, the scale of biogeographical variation in these pressure-response relationships is poorly understood, which may hinder eutrophication management in regions where lake ecology is less intensively studied. In this study, we derive ecology-based nutrient targets for five major ecoregions of Europe: Northern, Central-Baltic, Alpine, Mediterranean and Eastern Continental. As a first step, we developed regressions between nutrient concentrations and ecological quality ratios (EQR) based on phytoplankton and macrophyte communities. Significant relationships were established for 13 major lake types; in most cases, these relationships were stronger for phosphorus than for nitrogen, and stronger for phytoplankton than for macrophytes. Using these regressions, we estimated the total phosphorus (TP) and total nitrogen (TN) concentrations at which lakes of different types are likely to achieve good ecological status. However, in the very shallow lakes of the Eastern Continental region, relations between nutrient and biological communities were weak or non-significant. This can be attributed to high nutrient concentrations (in the asymptotic zone of phosphorus-phytoplankton models) suggesting other factors (light, grazing) limit primary production. However, we also show that fish stocking is a major pressure on Eastern Continental lakes, negatively affecting ecological status: lakes with low fish stocking show low chlorophyll-a concentrations and good ecological status despite high nutrient levels, while the lakes with high fish stocking show high chlorophyll-a and low ecological status. This study highlights the need to better understand lakes in biogeographic regions that have been, for historical reasons, less studied. This, in turn, helps reveal factors that challenge the dominant paradigms of lake assessment and management.
... The concentrated water samples were transferred to 110 mL vials after each sampling location, labeled, and fixed with formalin 2-4% [14]. The analysis of species composition was performed using a microscope at the magnitude of 10X-40X to identify the species of phytoplankton, using the techniques presented in the handbooks [15][16][17][18], which all describe the identification of phytoplankton in detail to the species level. ...
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An assessment of varying density, species composition and dynamics of phytoplankton in a combined rice-shrimp culture was carried out in My Xuyen district, Soc Trang province in the Vietnamese Mekong delta. Water was sampled six times at six separate locations within the culture system, on days 1, 20, 34, 57, 68, and day 81 of the rice-shrimp crop cycle. The results showed the abundance of 95 phytoplankton species belonging to five phyla including Cyanophyta, Chlorophyta, Bacillariophyta, Euglenophyta, and Pyrrophyta. The values of Shannon–Wiener index indicated high phytoplankton diversity, while the water quality ranged from medium to good. A Cluster Analysis showed that the phytoplankton density variation can be divided into three distinct periods. The initial phase of crop growth was dominated by Pandorina morum, Pediastrum simplex, Eudorina elegans, Oscillatoria limosa, and Anabaena circinalis. The midstage, reproductive phase of crop growth was dominated by Scenedesnus acuminatus, Pediastrum duplex, Closterinm setaceum, Scenedesnus quadricauda, and Actinastnum hantzschii. Whereas Scenedesnus acuminatus, Scenedesnus quadricauda, Closterinm closterioides, Staurastrum arcuatum, Euglena nhrenbergii, and Phacus lnsmorensis were dominant at the end of crop cycle. The findings provide useful information on phytoplankton assemblages in a typical rice-shrimp culture, which has recently gained popularity as an adaptive livelihood system.
... The mechanisms responsible for changes in algal diversity are mostly unknown (Reynolds 2006). Traditionally, external nutrient loads (total N and total P) and changes to lake morphometry (lake level) are considered "driving forces" of the shifts in the phytoplankton community (Hakanson et al. 2000, WFD 2000). ...
... It is widely accepted that cyanobacterial blooms are caused by many factors occurring simultaneously (Paerl et al., 2011a;Qin et al., 2016), but the formation of surface cyanobacterial blooms is possible only when cyanobacteria biomass in the water column is sufficient and floating conditions are suitable for cyanobacteria to ascend to the water surface (Reynolds, 2006). Given that in situ environmental conditions in Lake Taihu can support adequate cyanobacterial cells , the surface bloom is always promoted by environmental factors facilitating cyanobacteria ascending to the water surface. ...
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Cyanobacterial blooms are one of the most severe ecological problems affecting lakes. The vertical migration of cyanobacteria in the water column increases the uncertainty in the formation and disappearance of blooms, which may be closely associated with light, temperature, and wind speed. However, it is difficult to quantitatively evaluate the influencing factors of cyanobacteria vertical movement in natural environment compared to the laboratory experimental environment. Besides, both field survey and laboratory experiment method have the difficulties in determining the diurnal vertical migration of cyanobacteria at the synoptic lake scale. In this study, based on the diurnal dynamics of cyanobacterial bloom intensity (CBI) observed by the Geostationary Ocean Color Imager (GOCI) from 2011 to 2019, the daily variations, floating rate, and sinking rate of Microcystis aeruginosa were calculated in the natural environment. Then, the effects of light, temperature, and wind speed on the vertical migration of M. aeruginosa were analysed from the perspectives of day, night, and season. The results are as follows: the records of three typical patterns of diurnal CBI exhibited strong seasonal variability from the 9-year statistics; at night, the buoyancy recovery rate of cyanobacterial colonies increased with temperature, so that at temperature >15 °C and wind speed <3 m s⁻¹, CBI reached the maximum of the whole day at 08:16; the sinking rate of M. aeruginosa was positively correlated with the cumulated light energy at both synoptic and pixel scale; the upward migration speed of M. aeruginosa was positively correlated with the maximum wind speed of the day before cyanobacterial bloom. Therefore, the severer cyanobacterial blooms were often observed by satellite images after strong winds. The analysis of diurnal variation, floating rate, and sinking rate of M. aeruginosa will expand our knowledge for further understanding the formation mechanism of cyanobacterial blooms and for improving the accuracy of model simulation to predict the hourly changes in cyanobacterial blooms in Lake Taihu.
... where CPGc represents the cyanophycin content (% of R. raciborskii dry cell weight); C CPG (µg•mL − 1 ) is the cyanophycin concentration in the extract solution; V CPG (mL) is volume of the extract solution; B rap (mg•L − 1 ) is the biomass concentration of Raphidiopsis sp. in the ZH Reservoir; V w (mL) is the volume of water samples; and 10% is an empirical value representing the proportion of dry cell weight out of total fresh algal biomass (Reynolds, 2006). ...
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Nutrient storage is considered a critical strategy for algal species to adapt to a fluctuating nutrient supply. Luxury phosphorus (P) uptake into storage of polyphosphate extends the duration of cyanobacterial dominance and their blooms under P deficiency. However, it is unclear whether nitrogen (N) storage in the form of cyanophycin supports persistent cyanobacterial dominance or blooms in the tropics where N deficiency commonly occurs in summer. In this study, we examined genes for cyanophycin synthesis and degradation in Raphidiopsis raciborskii, a widespread and dominant cyanobacterium in tropical waters; and detected the cyanophycin accumulation under fluctuating N concentrations and its ecological role in the population dynamics of the species. The genes for cyanophycin synthesis (cphA) and degradation (cphB) were highly conserved in 21 out of 23 Raphidiopsis strains. This suggested that the synthesis and degradation of cyanophycin are evolutionarily conserved to support the proliferation of R. raciborskii in N-fluctuating and/or deficient conditions. Isotope ¹⁵N-NaNO3 labeling experiments showed that R. raciborskii QDH7 always commenced to synthesize and accumulate cyanophycin under fluctuating N conditions, regardless of whether exogenous N was deficient. When the NO3⁻-N concentration exceeded 1.2 mg•L⁻¹, R. raciborskii synthesized cyanophycin primarily through uptake of ¹⁵N-NaNO3. However, when the NO3⁻-N concentration was below 1.0 mg•L⁻¹, cyanophycin-based N was derived from unlabeled N2, as evidenced by increased dinitrogenase activity. Cells grown under NO3⁻-N < 1.0 mg•L⁻¹ had lower cyanophycin accumulation rates than cells grown under NO3⁻-N > 1.2 mg•L⁻¹. Our field investigation in a large tropical reservoir underscored the association between cyanophycin content and the population dynamics of R. raciborskii. The cyanophycin content was high in N-sufficient (NO3⁻-N > 0.45 mg•L⁻¹) periods, and decreased in N-deficient summer. In summer, R. raciborskii sustained a relatively high biomass and produced few heterocysts (< 1%). These findings indicated that cyanophycin-released N, rather than fixed N, supported persistent R. raciborskii blooms in N-deficient seasons. Our study suggests that the highly adaptive strategy in a N2-fixing cyanobacterial species makes mitigating its bloom more difficult than previously assumed.
... Foram realizadas duas (2) (Cole, 1994). considerando-se limitantes ao crescimento fitoplanctônico concentrações abaixo de 10 µg P L -1 , 100 µg N L -1 e 100 µg Si L -1 (Sas, 1989;2006). A turbidez (UNT) foi medida com turbidímetro de bancada, e a clorofila-a (µg L -1 ) foi estimada conforme Nusch (1980) (3) e Dinophyceae (2). ...
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Given the multiplicity of uses to which reservoirs are generally subjected, it is expected to find different conditions of composition, density and biomass of phytoplankton, due to possible spatial and seasonal variations of limnological conditions and land uses in the basin. Aiming to know the structure of phytoplankton and its variation in function of spatial heterogeneity in Moxotó Reservoir, located in the semiarid region of Northeastern Brazil, samples were analyzed in two periods, rainy (June 2009) and dry (December 2009). Samples were collected at a station in body (dam upstream) and at five in arms representing several human activities (aquaculture, agriculture, urban settlement, landfill and without punctual activity). Limnological variables, richness, density and biomass of phytoplankton were analyzed. Abundance/biomass comparison curves (ABC) were used to analyze phytoplankton structure. Algae diversity between periods and samples was estimated by cluster analysis, using species presence/absence data. Samples were ordinate (NMDS) by abundance and biomass of phytoplankton descriptor species. The relation between phytoplankton and limnological data was accessed by Pearson’s univariate correlation and BIOENV multivariate analysis. The reservoir presented regulated flow, short theoretical retention time (<7 days) and high water transparency (median zEUF: zMAX = 1.0). Phytoplankton biomass was consistent with low-productive systems (median = 0.9 µg L-1), limited mainly by phosphorus in rainy period (median SRP = 8.4 µg L-1), and nitrogen in dry period (median DIN = 36.5 µg L-1). Phytoplankton composition showed marked seasonality, especially for diatoms, with main contributions of planktonic in rainy period and typically periphytic in dry period. Under limitation by SRP and DIN, organisms adapted to mixotrophy (dinoflagellates and euglenoids) reached higher biomass. In contrast, nanoplanktonic organisms (chlorophytes and cryptophytes) were dominant in conditions of high nutrient availability. The studied sites showed three distinct environments: body, arms with submerged macrophytes and arms under influence of tributaries. Among human activities observed, agriculture was considered the most striking in relation to eutrophication. Moreover, proliferation of submerged macrophytes in arms can cause impairment for multiple uses, despite apparent benefits on water quality (increased transparency). Human activities, presence of submerged macrophytes and retention time influenced the availability of resources, being considered the driving forces of phytoplankton structure.
... The maximum abundance of phytoplankton communities was recorded during the SWM (627-1117 Cells L −1 ) and NEM (777-1240 Cells L −1 ) periods. Rainfall is an important factor that carries a higher concentration of macronutrients to the coastal waters and supports the higher abundance of phytoplankton and chlorophyll a concentration (Reynolds, 2006;Sridhar et al., 2006;Sarma et al., 2010;Jha et al., 2014). The higher relative abundance of diatom during the SWM and NEM might be due to the high concentration of silicate from the landward runoff, which induces rapid growth of diatom. ...
Article
We report here a year-round baseline assessment on phytoplankton diversity and abundance from the pristine coastal waters of the Andaman Islands (September 2011 - October 2012). A total of 84 phytoplankton species belonging to 47 genera were recorded from the North to South Andaman Islands. The maximum number of phytoplankton diversity (84 species under 47 genera) was recorded during the northeast monsoon (NEM) at a highly urbanized coastal environment like South Andaman Islands, whereas the minimum diversity (53 species under 34 genera) was recorded during the inter-monsoon (IM) period at the less anthropogenic activity sites viz. North and Middle Andaman Islands. All over seasons, the community composition of phytoplankton was mostly dominated by diatoms (45%–87%) followed by dinoflagellates (11%–46%) and blue–green algae (1%–35%). Besides, the abundance of phytoplankton was recorded as a gradual decrease from South Andaman to North Andaman Islands. The Canonical Correspondence Analysis (CCA) revealed the impact of physicochemical variables on phytoplankton assemblages. Thus, the temperature, salinity, and nitrite were the major environmental variables that influenced phytoplankton assemblage and distribution in the coastal waters of the Andaman Islands. The Principal Component Analysis (PCA) showed a strong variability of phytoplankton diversity in the South Andaman Islands (PC1: 32.6 - 36.2% variance). In addition, the Metric-multidimensional Scaling analysis also showed the gradual species intensity in the South Andaman than the Middle and North Andaman Islands. அந்தமான் தீவுகளின் (செப்டம்பர் 2011 - அக்டோபர் 2012) அழகிய கடலோர நீரில் இருந்து பைட்டோபிளாங்க்டன் பன்முகத்தன்மை மற்றும் மிகுதியாக இருப்பது குறித்த ஆண்டு முழுவதும் அடிப்படை மதிப்பீட்டை நாங்கள் இங்கு தெரிவிக்கிறோம். வடக்கு முதல் தெற்கு அந்தமான் தீவுகள் வரை 47 வகைகளைச் சேர்ந்த மொத்தம் 84 பைட்டோபிளாங்க்டன் இனங்கள் பதிவு செய்யப்பட்டுள்ளன. தென் அந்தமான் தீவுகள் போன்ற அதிக நகரமயமாக்கப்பட்ட கடலோர சூழலில் வடகிழக்கு பருவமழையின் போது (NEM) அதிகபட்ச எண்ணிக்கையிலான பைட்டோபிளாங்க்டன் பன்முகத்தன்மை (47 இனங்களுக்கு கீழ் உள்ள 84 இனங்கள்) பதிவு செய்யப்பட்டுள்ளது, அதே சமயம் குறைந்தபட்ச பன்முகத்தன்மை (34 இனங்களுக்கு கீழ் உள்ள 53 இனங்கள்) இடைப்பட்ட காலத்தில் பதிவு செய்யப்பட்டது. குறைந்த மானுடவியல் செயல்பாடு தளங்களில் பருவமழை (IM) காலம். வடக்கு மற்றும் மத்திய அந்தமான் தீவுகள். அனைத்து பருவங்களிலும், பைட்டோபிளாங்க்டனின் சமூக அமைப்பு பெரும்பாலும் டயட்டம்களால் (45%–87%) ஆதிக்கம் செலுத்தியது, அதைத் தொடர்ந்து டைனோஃப்ளாஜெல்லட்டுகள் (11%–46%) மற்றும் நீல-பச்சை பாசிகள் (1%–35%). தவிர, பைட்டோபிளாங்க்டனின் மிகுதியானது தெற்கு அந்தமானில் இருந்து வடக்கு அந்தமான் தீவுகளுக்கு படிப்படியாகக் குறைந்து வருவதாக பதிவு செய்யப்பட்டது. பைட்டோபிளாங்க்டன் கூட்டங்களில் இயற்பியல் வேதியியல் மாறிகளின் தாக்கத்தை கேனானிகல் கடிதப் பகுப்பாய்வு (CCA) வெளிப்படுத்தியது. எனவே, வெப்பநிலை, உப்புத்தன்மை மற்றும் நைட்ரைட் ஆகியவை அந்தமான் தீவுகளின் கடலோர நீரில் பைட்டோபிளாங்க்டன் கூட்டத்தையும் விநியோகத்தையும் பாதிக்கும் முக்கிய சுற்றுச்சூழல் மாறிகள் ஆகும். முதன்மை கூறு பகுப்பாய்வு (PCA) தெற்கு அந்தமான் தீவுகளில் பைட்டோபிளாங்க்டன் பன்முகத்தன்மையின் வலுவான மாறுபாட்டைக் காட்டியது (PC1: 32.6 - 36.2% மாறுபாடு). கூடுதலாக, மெட்ரிக்-பல்பரிமாண அளவிடுதல் பகுப்பாய்வு, மத்திய மற்றும் வடக்கு அந்தமான் தீவுகளை விட தெற்கு அந்தமானில் படிப்படியான இனங்கள் தீவிரத்தை காட்டியது
... It is thought that due to their small size, high abundance, fast population growth, and long-range dispersal, algae such as other microorganisms are considered as cosmopolitan because they occur in very diverse habitats and distribute globally (Fenchel and Finlay, 2004;Hillebrand, 2004;Graneli and Turner, 2006;Reynolds, 2006). However, recent studies reported that spatial diversity patterns also exist for algae (Ptacnik et al., 2010;Stomp et al., 2011;Wang et al., 2011;Maileht et al., 2013). ...
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Turkish lakes which have different morphometry and hydrology, have a great potential that supports distinct algal diversity as a result of different climate types and geographical variation (latitudinal, longitudinal, and altitudinal gradients). However, the algal flora of Turkey has not been completed, and the number of new taxa has increased due to new studies in Turkey. This study aims to describe new planktonic algal taxa for the Turkish freshwater algal flora. A total of 330 Chlorophyta, 164 Cyanobacteria and 187 Euglenozoa taxa were determined in a study conducted from 2017 to 2019 in 275 lakes of 25 river basins of Turkey. During this study, 116 Chlorophyta, 41 Cyanobacteria, and 81 Euglenozoa were found new records for the freshwater algal flora of Turkey.
... Adicionalmente, la interacción entre el caudal de entrada y la operación del embalse provoca gradientes longitudinales en las condiciones físicas, químicas y biológicas que definen una configuración longitudinal del sistema. La presencia y éxito reproductivo del fitoplancton en los embalses están determinados por el efecto combinado de factores abióticos y bióticos como la temperatura, la turbidez, la concentración de nutrientes, el pH, la herbivoría, los cambios en el nivel del agua, la estratificación térmica, la mezcla inducida por el viento y el caudal captado para generación en diferentes escalas espaciales y temporales (Reynolds, 2006). Por lo tanto, esta comunidad representa una efectiva herramienta de seguimiento para determinar la calidad del agua y ayudar a comprender las características y variaciones de estos ecosistemas acuáticos (Crossetti & Bicudo, 2008, Costa et al., 2009). ...
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Los rasgos funcionales morfológicos, fisiológicos y ecológicos de las comunidades planctónicas en sistemas naturales han mostrado sensibilidad frente a la variabilidad hidrológica, no obstante, hay poca información respecto a la dinámica funcional del fitoplancton en embalses tropicales con alto tiempo de residencia. En este trabajo se estudió la composición y biomasa de los grupos funcionales del fitoplancton propuestos por Reynolds et al. (2002), sus cambios durante periodos hidrológicos contrastantes y a lo largo del gradiente espacial (longitudinal y vertical) y su relación con variables físicas y químicas en el embalse El Peñol-Guatapé. Se registraron siete grupos funcionales, de acuerdo con su preferencia en términos de luz, estado trófico y condiciones de mezcla: GF-F (Botryococcus braunni, Oocystis cf. lacustris), GF-Lm (Ceratium furcoides y Microcystis wesenbergii), GF-Lo (Chroococcus minutus, Peridinium gatunense y un organismo de Peridiniales), GF-P (Staurastrum rotula), GF-S1 (Oscillatoria limosa), GF-Y (Cryptomonas sp. y Parvodinium sp.) y GF-Sin (que incluyó a Cyclotella sp.). A nivel temporal, los grupos respondieron a factores asociados con la hidrodinámica, el clima y las sustancias suspendidas y disueltas. En la escala espacial-longitudinal las condiciones impuestas por el afluente principal, especialmente el gradiente de luz, fueron determinantes en la distribución de los grupos. En cuanto a la dimensión vertical, los procesos de mezcla favorecieron la permanencia de los organismos en la zona fótica, de acuerdo con sus rasgos morfológicos y fueron determinantes de su distribución.
... Correctly identifying and quantifying the species present in an ecosystem is essential to bioassessment programs (McElroy et al., 2020). Conventional assessments are performed by trained taxonomists who identify taxa via morphological and structural traits (Gao et al., 2018;Reynolds, 2006;Vuorio et al., 2020) which include the organization, shape and size of cells as well as specialized cells (Castenholz, 2015;Li et al., 2019a). Light microscopy is still widely used today to identify and count algal cells (Karlson et al., 2010;Li et al., 2019b;Utermöhl, 1958). ...
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Accurately identifying the species present in an ecosystem is vital to lake managers and successful bioassessment programs. This is particularly important when monitoring cyanobacteria, as numerous taxa produce toxins and can have major negative impacts on aquatic ecosystems. Increasingly, DNA-based techniques such as meta- barcoding are being used for measuring aquatic biodiversity, as they could accelerate processing time, decrease costs and reduce some of the biases associated with traditional light microscopy. Despite the continuing use of traditional microscopy and the growing use of DNA metabarcoding to identify cyanobacteria assemblages, methodological comparisons between the two approaches have rarely been reported from a wide suite of lake types. Here, we compare planktonic cyanobacteria assemblages generated by inverted light microscopy and DNA metabarcoding from a 379-lake dataset spanning a longitudinal and trophic gradient. We found moderate levels of congruence between methods at the broadest taxonomic levels (i.e., Order, RV=0.40, p < 0.0001). This comparison revealed distinct cyanobacteria communities from lakes of different trophic states, with Microcystis, Aphanizomenon and Dolichospermum dominating with both methods in eutrophic and hypereutrophic sites. This finding supports the use of either method when monitoring eutrophication in lake surface waters. The biggest difference between the two methods was the detection of picocyanobacteria, which are typically underestimated by light microscopy. This reveals that the communities generated by each method currently are complementary as opposed to identical and promotes a combined-method strategy when monitoring a range of trophic systems. For example, microscopy can provide measures of cyanobacteria biomass, which are critical data in managing lakes. Going forward, we believe that molecular genetic methods will be increasingly adopted as reference da- tabases are routinely updated with more representative sequences and will improve as cyanobacteria taxonomy is resolved with the increase in available genetic information.
... grazing and microbial lysis), often upper hand in regulating the phytoplankton growth and distributions in the pelagic environments (Margalef, 1978;Evans and Brussaard, 2012). Major phytoplankton functional groups (PFGs), such as diatoms, dinoflagellates, cyanobacteria, cryptophytes, coccolithophores, etc., are the chief modulators of organic matter transport from the surface to the deeper waters in the marine systems (Reynolds, 2006). The evaluation of various phytoplankton community dynamics can be achieved either by the traditional microscopy (up to species level) or by the advanced FlowCam (mostly up to generic level) techniques. ...
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Phytoplankton community composition and its temporal dynamics were evaluated in the Alappuzha near shore waters (<15 m depth), including mud bank region, located along the southwest coast of India, using HPLCderived marker pigments and microscope-based species composition data. The study has shown a characteristic phytoplankton succession pattern, wherein an exceptional increase in chlorophyll a (Chl a, >10 mg m􀀀 3), observed in the whole study region during the peak southwest monsoon (SWM - July) period, apparently unveiled the biological manifestation of nutrient enrichments facilitated by the coastal upwelling phenomenon. A conspicuous increase in fucoxanthin (a biomarker for diatoms) perceived across the study region clearly indicated the preponderance of diatoms (mainly Thalassiosira sp., Skeletonema costatum, Trieres mobiliensis, Nitzschia sp. etc.), particularly during the peak SWM period. The CHEMTAX calculations have shown the significant contribution of Chl a (av. 76% of total Chl a) from diatoms, regardless of seasons, compared to other taxonomic groups. Furthermore, the combined results of HPLC-CHEMTAX analyses have demonstrated the seasonal occurrence of various small-sized phytoplankton functional groups (PFGs), specifically cyanobacteria, cryptophytes and chlorophytes, along with the predominant large-sized PFGs, i.e. diatoms (mostly) and dinoflagellates. The relative increase in zeaxanthin prevalent during the warm periods (Pre-SWM and Post SWM) signified the presence of cyanobacteria. By contrast, during the SWM period, a conspicuous increase in Chl b and alloxanthin recorded in the whole study region indicated the abundance of green algae and cryptophytes, respectively. Likewise, a nominal increase in peridinin (a marker for dinoflagellates) prevalent during the onset of SWM was apparently due to the proliferation of dinoflagellates, Tripos furca and Prorocentrum micans (microscopically confirmed). Even though the overall CHEMTAX results clearly complemented the microscopy derived phytoplankton composition data, especially the abundance of large sized PFGs, (i.e. diatoms and dinoflagellates), this particular analysis could enable the portrayal of seasonal dynamics of small-sized PFGs (mainly cyanobacteria and cryptophytes) as well, as this information is highly significant as far as the study region is concerned.
... Moreover, phytoplankton has a key function in lake ecosystems as it is the trophic cornerstone of the pelagic food web since it provides biomass towards higher trophic levels like zooplankton and fish. Moreover, modelling algae is inherently difficult because of their lateral patchiness, vertical distributions, temporal variations (blooming), zooplankton grazing and the still evolving understanding of algae biological dynamics (Hipsey et al., 2006;Reynolds, 2006). ...
... Moreover, the small diatom T. pseudonana had higher growth rates than the bigger C. weissflogii (Figure 3 and Supplementary Figure 3A), this most probably due to a larger surface-tovolume (S/V) ratio in T. pseudonana, which allowed a more efficient resource uptake, especially when algal growth reduced the availability of nutrients and light in the mixed culture (Reynolds, 2006;Ryabov et al., 2021). ...
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... This result supports the documented tendency of dinoflagellates to thrive in warmer, stratified and nutrient-depleted waters in contrast with diatoms (Le Quéré et al., 2005), and corroborates the findings of previous analyses of the L4 phytoplankton data (Mutshinda et al., 2017(Mutshinda et al., , 2019. In diatoms, irradiance effects on species' occurrence probabilities are broadly negative, in line with the notion that diatoms are generally adapted to low light levels (Reynolds, 2006). On the other hand, temperature effects vary widely among the diatom species with negative effects for 15% of them, implying higher occurrence probability at lower temperatures and positive effects for about the same proportion of species indicating higher occurrence probability at higher temperatures. ...
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Phytoplankton biomass data often involve zero outcomes preventing a description by continuous distributions with positive support such as the lognormal distribution commonly used to describe ecological data. Two usual solutions: ignoring the zeroes and adding a small positive number to all outcomes, induce bias and reduce predictive power. To address these shortcomings, we design a Bayesian two-part model with a binary component for presence or absence and a continuous component involving a lognormal model for non-zero biomass. We specify two equations relating species-specific occurrence probabilities and expected log-biomasses when present to potential covariates, with spike-and-slab priors imposed on linear effects to selectively discard the irrelevant predictors. We analyze the biomass data of 74 phytoplankton (57 diatoms and 17 dinoflagellates) recorded weekly at Station L4 (Western English Channel, UK) between April 2003 and December 2009, along with measurements of abiotic covariates. Our results disclose different combinations of environmental predictors for the occurrence and the biomass of individual species. Overall, the occurrence of dinoflagellates is associated with higher temperature and irradiance levels compared to diatoms, with virtually no dependence on nutrient concentrations. Irradiance emerges as the key predictor of biomass when species are present. Optimum temperatures for biomass accumulation and temperature sensitivities vary widely among and within functional types. Compared to one-stage models based on usual zero-handling approaches, our two-part model stands out with higher prediction accuracy. The two-part modeling approach provides a valuable framework for decoupling the predictors of species occurrence and abundance from observational data.
... After determining the dimensions, the identification of the recorded taxa was performed using the standard literature [23][24][25][26][27][28][29][30][31]. The classification into main divisions, Cyanobacteria, Bacillariophyta, Chlorophyta, Chrysophyta, Cryptophyta, Dinophyta, and Euglenophyta, was carried out according to [32]. ...
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The study aimed to investigate the physico-chemical properties as well as phytoplankton and bacterial community diversity of Bovan Lake reservoir in Serbia to gain insight into the seasonal dynamic of water quality. All analyses were performed at three localities and water depths in spring, summer, autumn, and winter 2019. Seven phytoplankton phyla comprising 139 taxa were detected at all three localities (Chlorophyta 58%, Bacillariophyta 14%, Cyanobacteria 9%, Chrysophyta 5%, Dinophyta 5%, Euglenophyta 5%, and Cryptophyta 4%). Winter 2019 was characterized by the presence of 36 unique species in all phyla except Euglenophyta. Bacterial diversity analyses showed that Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, and Verrucomicrobia dominated the water intake locality at all three water depths (0.5, 10, and 20 m below the surface). In general, the physico-chemical parameters, phytoplankton, and bacterial community composition depended on the season and the water depth and showed that Bovan Lake was of satisfactory ecological status and water quality at all localities, and meets the needs for all intended purposes.
... During the experiment, growth rates (r n ) were calculated following Reynolds (2006): ...
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Cyanobacteria harmful blooms can represent a major risk for public health due to potential release of toxins and other noxious compounds in the water. A continuous and high-resolution monitoring of the cyanobacteria population is required due to their rapid dynamics, which has been increasingly done using in-situ fluorescence of phycocyanin (f-PC) and chlorophyll a (f-Chl a). Appropriate in-situ fluorometers calibration is essential because f-PC and f-Chl a are affected by biotic and abiotic factors, including species composition. Measurement of f-PC and f-Chl a in mixed species assemblages during different growth phases - representative of most field conditions - has received little attention. We hypothesized that f-PC and f-Chl a of mixed assemblages of cyanobacteria may be accurately estimated if taxa composition and fluorescence characteristics are known. We also hypothesized that species with different morphologies would have different fluorescence per unit cell and biomass. We tested these hypotheses in a controlled culture experiment in which photosynthetic pigment fluorescence, chemical pigment extraction, optical density and microscopic enumeration of four common cyanobacteria species (Aphanocapsa sp, Microcystis aeruginosa, Dolichospermum circinale and Raphidiopsis raciborskii) were quantified. Both monocultures and mixed cultures were monitored from exponential to late stationary growth phases. The sum of fluorescence of individual species calculated for mixed samples was not significantly different than measured fluorescence of mixed cultures. Estimated and measured f-PC and f-Chl a of mixed cultures had higher correlations and smaller absolute median errors when estimations were based on fluorescence per biomass instead of fluorescence per cell. Largest errors were overestimations of measured fluorescence for species with different morphologies. Fluorescence per cell was significantly different among most species, while fluorescence per unit biomass was not, indicating that conversion of fluorescence to biomass reduces species-specific bias. This study presents new information on the effect of species composition on cyanobacteria fluorescence. Best practices of deployment and operation of fluorometers, and data-driven models supporting in-situ fluorometers calibration are discussed as suitable solutions to minimize taxa-specific bias in fluorescence estimates.
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Thesis (M.S.)--University of Connecticut, 1971. Includes bibliographical references.