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1.
Mar Pollut Bull ; 142: 119-128, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31232284

RESUMO

To explore the effects of coastal eutrophication and warming on phytoplankton biomass and cell size, we analyzed current and historical data for size-fractionated chlorophyll a (chla) in Xiangshan Bay, China. Results showed that micro- and nanophytoplankton overwhelmingly dominated (>84%) in all seasons. The contribution of micro-chla was significantly lower in warm than in cold seasons, whereas contribution of pico-chla showed the opposite result. Overall, the micro-chla contribution increased with decreasing pico-chla contribution from the stable, clear, eutrophic upper bay to the turbulent, turbid lower bay, indicating that phytoplankton size structure on a spatial scale was largely shaped by water column stability and light rather than by nutrients. Since the 1980s, phytoplankton biomass, primary productivity, and micro-chla contribution in Xiangshan Bay have increased sharply with increasing nutrient amounts and temperature. Additionally, it seems that algal bloom seasonality has shifted forward from spring to winter since the power plant operations in 2006.


Assuntos
Fitoplâncton , Baías , Biomassa , China , Clorofila A/análise , Eutrofização , Fitoplâncton/citologia , Fitoplâncton/crescimento & desenvolvimento , Centrais Elétricas , Estações do Ano , Análise Espaço-Temporal , Temperatura Ambiente
2.
Eur Phys J E Soft Matter ; 42(3): 31, 2019 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-30879226

RESUMO

Gyrotactic algae are bottom heavy, motile cells whose swimming direction is determined by a balance between a buoyancy torque directing them upwards and fluid velocity gradients. Gyrotaxis has, in recent years, become a paradigmatic model for phytoplankton motility in flows. The essential attractiveness of this peculiar form of motility is the availability of a mechanistic description which, despite its simplicity, revealed predictive, rich in phenomenology, easily complemented to include the effects of shape, feedback on the fluid and stochasticity (e.g., in cell orientation). In this review we consider recent theoretical, numerical and experimental results to discuss how, depending on flow properties, gyrotaxis can produce inhomogeneous phytoplankton distributions on a wide range of scales, from millimeters to kilometers, in both laminar and turbulent flows. In particular, we focus on the phenomenon of gyrotactic trapping in nonlinear shear flows and in fractal clustering in turbulent flows. We shall demonstrate the usefulness of ideas and tools borrowed from dynamical systems theory in explaining and interpreting these phenomena.


Assuntos
Modelos Biológicos , Fitoplâncton/fisiologia , Fenômenos Biomecânicos , Movimento Celular , Hidrodinâmica , Movimento , Fenômenos Físicos , Fitoplâncton/citologia , Reologia , Análise de Sistemas
3.
ISME J ; 13(5): 1133-1143, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30607028

RESUMO

Here we aim to incorporate trait-based information into the modern coexistence framework that comprises a balance between stabilizing (niche-based) and equalizing (fitness) mechanisms among interacting species. Taking the modern coexistence framework as our basis, we experimentally tested the effect of size differences among species on coexistence by using fifteen unique pairs of resident vs. invading cyanobacteria, resulting in thirty unique invasibility tests. The cyanobacteria covered two orders of magnitude differences in size. We found that both niche and fitness differences increased with size differences. Niche differences increased faster with size differences than relative fitness differences and whereas coexisting pairs showed larger size differences than non-coexisting pairs, ultimately species coexistence could not be predicted on basis of size differences only. Our findings suggest that size is more than a key trait controlling physiological and population-level aspects of phytoplankton, it is also relevant for community-level phenomena such as niche and fitness differences which influence coexistence and biodiversity.


Assuntos
Cianobactérias/fisiologia , Fitoplâncton/fisiologia , Biodiversidade , Cianobactérias/citologia , Ecossistema , Aptidão Genética , Fenótipo , Fitoplâncton/citologia
4.
Microbiologyopen ; 8(2): e00629, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-29656564

RESUMO

The cellular size and biomass of picophytoplankton were studied by flow cytometer during spring monsoon (March-May of 2015) in equatorial eastern Indian Ocean. We established an empirical relationship between forward scatter and cellular size to address the size and biomass of picophytoplankton. Results indicated that mean cell diameter of Prochlorococcus (0.60 µm) was the smallest, and then followed by Synechococcus (0.98 µm) and picoeukaryotic phytoplankton (1.05 µm). Thereafter, the biomass converted by abundance reached 0.64 µg·C·L-1 for Prochlorococcus, 0.34 µg·C·L-1 for Synechococcus, and 0.20 µg·C·L-1 for picoeukaryotic phytoplankton. Additionally, the distinct biomass contribution of picophytoplankton appeared to be affected by abundance, but not changes in cellular size. Vertically, the cellular sizes of picophytoplankton were remarkably small in upper waters, which was predominantly controlled by the nutrient availability. In contrast, they were larger in deeper waters, which was primarily attributed to the combined effects of low temperature and reduced light availability. Spatially, under the influence of high nutrient concentration induced by the different circulations and coastal upwelling, slightly high carbon biomass of picophytoplankton was observed around the coastal zones of Sri Lanka island and Sumatra, as well as the southern Bay of Bengal.


Assuntos
Biomassa , Tamanho Celular , Fitoplâncton/citologia , Fitoplâncton/crescimento & desenvolvimento , Água do Mar/microbiologia , Células Eucarióticas/citologia , Citometria de Fluxo , Oceano Índico , Prochlorococcus/citologia , Prochlorococcus/crescimento & desenvolvimento , Sri Lanka , Synechococcus/citologia , Synechococcus/crescimento & desenvolvimento
5.
Appl Spectrosc ; 73(1): 104-114, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30012006

RESUMO

The use of rotating filter wheels is common in photometric applications. Traditional filter wheel designs typically exhibit a number of filter openings spaced evenly about the circumference of the wheel. In this work we examine a number of shortcomings of this traditional filter design in measurements of phytoplankton fluorescence made with our fluorescence imaging photometer (FIP). We present an alternative asymmetric wheel design that offers a number of advantages over the traditional design as well as a new processing algorithm designed to accommodate convolution of signals from adjacent channels inherent in measurements collected with the asymmetric design. This approach eliminates the need for a separate signal to establish timing and wheel position, unambiguously establishes filter order even when the direction of rotation is unknown, allows for better estimates of signal baseline, and is more resilient to effects of vibration and other dynamic processes that could occur on the time scale of wheel rotation. We demonstrate performance improvements for phytoplankton fluorescence measurements associated with the new wheel design and algorithm compared with previously published methods using the FIP. Both the improved image processing algorithm and filter wheel design were found to reduce noise in our measurements significantly.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador/métodos , Imagem Óptica/métodos , Fitoplâncton , Desenho de Equipamento , Microscopia de Fluorescência/instrumentação , Microscopia de Fluorescência/métodos , Imagem Óptica/instrumentação , Fotometria/instrumentação , Fotometria/métodos , Fitoplâncton/química , Fitoplâncton/citologia
6.
Sci Rep ; 8(1): 16125, 2018 10 31.
Artigo em Inglês | MEDLINE | ID: mdl-30382139

RESUMO

In this first in situ study of the dynamic availability of phytoplankton micronutrients, a SeaExplorer glider was combined with Diffusive Gradients in Thin Films and deployed in the Mediterranean Sea. On the basis of their labile metal complex pools, we discovered that Fe and Co can be potentially limiting and Cu co-limiting to diatom growth, contrary to the generally accepted view that phosphorus (phosphate) is the growth limiting element in the Mediterranean Sea. For flagellates and picoplankton, phosphorus remains the main element limiting growth. Our in situ measurements showed that organic complexes of Fe and Cu (>98% of total dissolved concentration), dissociate slower than inorganic complexes of Co, Cd and Ni (>99% of total dissolved concentration being free ions and inorganic complexes). This strengthens the potential growth limiting effect of Fe and Cu versus phosphate, which is present as a free ion and, thus, directly available for plankton.


Assuntos
Diatomáceas/crescimento & desenvolvimento , Micronutrientes/análise , Água do Mar/química , Difusão , Cinética , Mar Mediterrâneo , Metais/análise , Fitoplâncton/citologia
7.
Nature ; 563(7731): 412-415, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30429546

RESUMO

Algae produce massive amounts of dimethylsulfoniopropionate (DMSP), which fuel the organosulfur cycle1,2. On a global scale, several petagrams of this sulfur species are produced annually, thereby driving fundamental processes and the marine food web1. An important DMSP transformation product is dimethylsulfide, which can be either emitted to the atmosphere3,4 or oxidized to dimethylsulfoxide (DMSO) and other products5. Here we report the discovery of a structurally unusual metabolite, dimethylsulfoxonium propionate (DMSOP), that is synthesized by several DMSP-producing microalgae and marine bacteria. As with DMSP, DMSOP is a low-molecular-weight zwitterionic metabolite that carries both a positively and a negatively charged functional group. Isotope labelling studies demonstrate that DMSOP is produced from DMSP, and is readily metabolized to DMSO by marine bacteria. DMSOP was found in near nanomolar amounts in field samples and in algal culture media, and thus represents-to our knowledge-a previously undescribed biogenic source for DMSO in the marine environment. The estimated annual oceanic production of oxidized sulfur from this pathway is in the teragram range, similar to the calculated dimethylsulfide flux to the atmosphere3. This sulfoxonium metabolite is therefore a key metabolite of a previously undescribed pathway in the marine sulfur cycle. These findings highlight the importance of DMSOP in the marine organosulfur cycle.


Assuntos
Organismos Aquáticos/metabolismo , Bactérias/metabolismo , Microalgas/metabolismo , Compostos de Enxofre/metabolismo , Bactérias/crescimento & desenvolvimento , Dimetil Sulfóxido/metabolismo , Marcação por Isótopo , Microalgas/crescimento & desenvolvimento , Oxirredução , Fitoplâncton/citologia , Fitoplâncton/metabolismo , Sulfetos/metabolismo , Compostos de Sulfônio/metabolismo , Compostos de Enxofre/química
8.
Mar Pollut Bull ; 135: 562-568, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30301074

RESUMO

The characteristics of phytoplankton assemblages were analyzed by the Utermöhl method in the southern Yellow Sea in summer, 2008. A total of 113 species (including varieties and forms), belonging to 51 genera and 3 phyla, were identified. Diatom was the most dominant group. The dominant species included Eucampia zoodiacus, Leptocylindrus danicus, Chaetoceros affinis, Thalassionema nitzschioides, Skeletonema costatum, Paralia sulcata and Chaetoceros tortissimus, which were eurytopic and temperate species. The cell abundance of phytoplankton ranged from 0.04 to 620.08 cells·mL-1 with an average of 27.52 cells·mL-1. Horizontally, the cell abundance showed a decreasing trend from the south to the north. In terms of vertical distribution, the values in surface and subsurface water layers were higher than those in bottom water layers. Results of correlation analysis showed that phytoplankton cell abundance was positively correlated with water temperature, ammonia and nitrite concentrations, and negatively correlated with salinity and silicate concentration.


Assuntos
Diatomáceas/fisiologia , Fitoplâncton , Biodiversidade , China , Diatomáceas/citologia , Monitoramento Ambiental/métodos , Oceanos e Mares , Fitoplâncton/citologia , Salinidade , Estações do Ano , Temperatura Ambiente
9.
Environ Microbiol Rep ; 10(6): 704-710, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30259678

RESUMO

The verification that many phytoflagellates ingest prokaryotes has changed the view of the microbial loop in aquatic ecosystems. Still, progress is limited because the phagotrophic activity is difficult to quantify in natural assemblages. Linking the food vacuole content in protist with the ingestion rate of prokaryotes would provide a crucial step forward. In this study, using the catalysed reporter deposition - fluorescence in situ hybridization protocol (CARD-FISH), which allows the visualization of labelled prokaryotes inside protists without relying on incubation procedures, we experimentally relate the food vacuole content of prokaryotes (Vc ) to the population-averaged ingestion rates (Ir ) estimated using bacteria-size fluorescent microspheres. The two variables relate according to the equation Ir = 7.52 Vc 0.9 , which indicates a prokaryote half-life of about 6 min in the protist vacuole. Five mixotrophic flagellate species from natural and culture populations were evaluated seven times during 24 h; they provided a broad range of average vacuole content (0.01 to 2.02 prokaryote protist-1 ) and ingestion rates (0.18 to 23 prokaryote protist-1 h-1 ). Consequently, the relationship found can be applied to quantify the mixotrophy activity in a large variety of field and experimental studies.


Assuntos
Betaproteobacteria/crescimento & desenvolvimento , Eucariotos/fisiologia , Fitoplâncton/fisiologia , Vacúolos/microbiologia , Betaproteobacteria/genética , Eucariotos/classificação , Processos Heterotróficos , Hibridização in Situ Fluorescente , Interações Microbianas , Microscopia de Vídeo , Microesferas , Fitoplâncton/citologia , Fitoplâncton/microbiologia , Células Procarióticas , Especificidade da Espécie
10.
J Phycol ; 54(4): 557-570, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29908074

RESUMO

Some diatoms are able to colonize as epibionts on their potential zooplankton predators. Here, we report Pseudohimantidium pacificum living on the copepod Corycaeus giesbrechti and as a new finding on Oithona nana, Protoraphis atlantica living on the copepod Pontellopsis brevis, Protoraphis hustedtiana on the cypris larvae of barnacles, and Falcula hyalina on the copepod Acartia lilljeborgii. The epizoic diatoms were able to grow as free-living forms under culture conditions. Pseudohimantidium pacificum and P. atlantica appeared as the most derived species from their benthic diatom ancestors. The mucilage pad or stalk of the strains of these species showed important morphological distinction when compared with their epizoic forms. Barnacle larvae explore benthic habitats before settlement, and epibiosis on them is an example where P. hustedtiana profits from the host behavior for dispersal of its benthic populations. Molecular phylogenies based on the SSU rRNA and RuBisCO large subunit (rbcL) gene sequences revealed F. hyalina as an independent lineage within the Fragilariales (Tabularia, Catacombas, and others), consistent with its morphological distinction in the low number of rows (≤6) in the ocellulimbus, among other features. We propose the transfer of F. hyalina to the genus Pseudofalcula gen. nov. Molecular phylogeny suggests a single order for the members of the Cyclophorales and the Protoraphidales, and that the epibioses of araphid diatoms on marine zooplankton have been independently acquired several times. These clades are constituted of both epizoic and epiphytic/epilithic forms that evidence a recent acquisition of the epizoic modus vivendi.


Assuntos
Diatomáceas/classificação , Zooplâncton/classificação , Animais , DNA Ribossômico/análise , Diatomáceas/citologia , Diatomáceas/genética , Diatomáceas/ultraestrutura , Microscopia Eletrônica de Varredura , Filogenia , Fitoplâncton/classificação , Fitoplâncton/citologia , Fitoplâncton/genética , Fitoplâncton/ultraestrutura , Ribulose-Bifosfato Carboxilase/análise , Zooplâncton/citologia , Zooplâncton/genética , Zooplâncton/ultraestrutura
11.
PLoS Comput Biol ; 14(4): e1006118, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29702650

RESUMO

Nutrient acquisition is a critical determinant for the competitive advantage for auto- and osmohetero- trophs alike. Nutrient limited growth is commonly described on a whole cell basis through reference to a maximum growth rate (Gmax) and a half-saturation constant (KG). This empirical application of a Michaelis-Menten like description ignores the multiple underlying feedbacks between physiology contributing to growth, cell size, elemental stoichiometry and cell motion. Here we explore these relationships with reference to the kinetics of the nutrient transporter protein, the transporter rate density at the cell surface (TRD; potential transport rate per unit plasma-membrane area), and diffusion gradients. While the half saturation value for the limiting nutrient increases rapidly with cell size, significant mitigation is afforded by cell motion (swimming or sedimentation), and by decreasing the cellular carbon density. There is thus potential for high vacuolation and high sedimentation rates in diatoms to significantly decrease KG and increase species competitive advantage. Our results also suggest that Gmax for larger non-diatom protists may be constrained by rates of nutrient transport. For a given carbon density, cell size and TRD, the value of Gmax/KG remains constant. This implies that species or strains with a lower Gmax might coincidentally have a competitive advantage under nutrient limited conditions as they also express lower values of KG. The ability of cells to modulate the TRD according to their nutritional status, and hence change the instantaneous maximum transport rate, has a very marked effect upon transport and growth kinetics. Analyses and dynamic models that do not consider such modulation will inevitably fail to properly reflect competitive advantage in nutrient acquisition. This has important implications for the accurate representation and predictive capabilities of model applications, in particular in a changing environment.


Assuntos
Modelos Biológicos , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/fisiologia , Transporte Biológico Ativo , Carbono/metabolismo , Biologia Computacional , Alimentos , Cinética , Consórcios Microbianos , Fenômenos Microbiológicos , Movimento/fisiologia , Fitoplâncton/citologia
12.
Appl Opt ; 57(7): B197-B204, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29522021

RESUMO

We propose a compact imaging system that integrates an augmented reality head mounted device with digital holographic microscopy for automated cell identification and visualization. A shearing interferometer is used to produce holograms of biological cells, which are recorded using customized smart glasses containing an external camera. After image acquisition, segmentation is performed to isolate regions of interest containing biological cells in the field-of-view, followed by digital reconstruction of the cells, which is used to generate a three-dimensional (3D) pseudocolor optical path length profile. Morphological features are extracted from the cell's optical path length map, including mean optical path length, coefficient of variation, optical volume, projected area, projected area to optical volume ratio, cell skewness, and cell kurtosis. Classification is performed using the random forest classifier, support vector machines, and K-nearest neighbor, and the results are compared. Finally, the augmented reality device displays the cell's pseudocolor 3D rendering of its optical path length profile, extracted features, and the identified cell's type or class. The proposed system could allow a healthcare worker to quickly visualize cells using augmented reality smart glasses and extract the relevant information for rapid diagnosis. To the best of our knowledge, this is the first report on the integration of digital holographic microscopy with augmented reality devices for automated cell identification and visualization.


Assuntos
Diatomáceas/citologia , Holografia/métodos , Microscopia/instrumentação , Reconhecimento Automatizado de Padrão/métodos , Fitoplâncton/citologia , Dispositivos Eletrônicos Vestíveis , Desenho de Equipamento , Humanos , Imagem Tridimensional/métodos , Dispositivos Ópticos
13.
ISME J ; 12(4): 1094-1108, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29348580

RESUMO

Diatoms are a diverse and ecologically important group of phytoplankton. Although most species are considered free living, several are known to interact with other organisms within the plankton. Detailed imaging and molecular characterization of any such partnership is, however, limited, and an appraisal of the large-scale distribution and ecology of such consortia was never attempted. Here, observation of Tara Oceans samples from the Benguela Current led to the detection of an epibiotic association between a pennate diatom and a tintinnid ciliate. We identified the diatom as Fragilariopsis doliolus that possesses a unique feature to form barrel-shaped chains, associated with seven different genera of tintinnids including five previously undescribed associations. The organisms were commonly found together in the Atlantic and Pacific Ocean basins, and live observations of the interaction have been recorded for the first time. By combining confocal and scanning electron microscopy of individual consortia with the sequencing of high-resolution molecular markers, we analyzed their distribution in the global ocean, revealing morpho-genetically distinct tintinnid haplotypes and biogeographically structured diatom haplotypes. The diatom was among the most abundant in the global ocean. We show that the consortia were particularly prevalent in nutrient-replete conditions, rich in potential predators. These observations support the hypothesis of a mutualistic symbiosis, wherein diatoms acquire increased motility and tintinnids benefit from silicification through increased protection, and highlight that such associations may be more prevalent than currently appreciated.


Assuntos
Cilióforos , Diatomáceas/fisiologia , Diatomáceas/classificação , Diatomáceas/citologia , Diatomáceas/genética , Haplótipos , Processos Heterotróficos , Oceanos e Mares , Fitoplâncton/citologia , Fitoplâncton/genética , Fitoplâncton/fisiologia , Simbiose
14.
Nat Commun ; 9(1): 74, 2018 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-29311545

RESUMO

Photosynthesis by marine diatoms plays a major role in the global carbon cycle, although the precise mechanisms of dissolved inorganic carbon (DIC) uptake remain unclear. A lack of direct measurements of carbonate chemistry at the cell surface has led to uncertainty over the underlying membrane transport processes and the role of external carbonic anhydrase (eCA). Here we identify rapid and substantial photosynthesis-driven increases in pH and [CO32-] primarily due to the activity of eCA at the cell surface of the large diatom Odontella sinensis using direct simultaneous microelectrode measurements of pH and CO32- along with modelling of cell surface inorganic carbonate chemistry. Our results show that eCA acts to maintain cell surface CO2 concentrations, making a major contribution to DIC supply in O. sinensis. Carbonate chemistry at the cell surface is therefore highly dynamic and strongly dependent on cell size, morphology and the carbonate chemistry of the bulk seawater.


Assuntos
Carbonatos/metabolismo , Microambiente Celular , Diatomáceas/metabolismo , Fitoplâncton/metabolismo , Transporte Biológico , Carbono/química , Carbono/metabolismo , Dióxido de Carbono/química , Dióxido de Carbono/metabolismo , Carbonatos/química , Anidrases Carbônicas/metabolismo , Diatomáceas/citologia , Concentração de Íons de Hidrogênio , Modelos Biológicos , Fotossíntese , Fitoplâncton/citologia , Água do Mar/química
15.
J Math Biol ; 76(1-2): 67-96, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28547211

RESUMO

The Sheldon spectrum describes a remarkable regularity in aquatic ecosystems: the biomass density as a function of logarithmic body mass is approximately constant over many orders of magnitude. While size-spectrum models have explained this phenomenon for assemblages of multicellular organisms, this paper introduces a species-resolved size-spectrum model to explain the phenomenon in unicellular plankton. A Sheldon spectrum spanning the cell-size range of unicellular plankton necessarily consists of a large number of coexisting species covering a wide range of characteristic sizes. The coexistence of many phytoplankton species feeding on a small number of resources is known as the Paradox of the Plankton. Our model resolves the paradox by showing that coexistence is facilitated by the allometric scaling of four physiological rates. Two of the allometries have empirical support, the remaining two emerge from predator-prey interactions exactly when the abundances follow a Sheldon spectrum. Our plankton model is a scale-invariant trait-based size-spectrum model: it describes the abundance of phyto- and zooplankton cells as a function of both size and species trait (the maximal size before cell division). It incorporates growth due to resource consumption and predation on smaller cells, death due to predation, and a flexible cell division process. We give analytic solutions at steady state for both the within-species size distributions and the relative abundances across species.


Assuntos
Ecossistema , Modelos Biológicos , Plâncton/citologia , Animais , Organismos Aquáticos/citologia , Biomassa , Divisão Celular , Biologia Computacional , Cadeia Alimentar , Conceitos Matemáticos , Fitoplâncton/citologia , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/fisiologia , Plâncton/crescimento & desenvolvimento , Plâncton/fisiologia , Especificidade da Espécie , Zooplâncton/citologia , Zooplâncton/crescimento & desenvolvimento , Zooplâncton/fisiologia
16.
Harmful Algae ; 69: 48-64, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-29122242

RESUMO

Clay dispersal is one of only a few mitigation methods for harmful algal blooms (HABs) ever applied in the field; however, low flocculation efficiency has always been the most significant drawback associated with natural unmodified clays. This review discusses key factors affecting the flocculation efficiency, based on results obtained in studies of the mechanisms underlying interactions between clay particles and HAB organisms. It further elaborates clay surface modification theory and methods for improving removal efficiency of HAB cells, followed by descriptions of various modified clays successfully prepared with removal efficiencies of HAB cells that are up to hundreds of times greater than natural clays and have lower dosing requirements of 4-10t/km2. Presently, modified clays are the most widely used method for the mitigation of HAB in the field in China. This review also evaluates potential ecological effects of modified clay disposal on water quality, typical aquatic organisms, benthic environments, and ecosystems. Both laboratory and field results have demonstrated that modified clays markedly can actually improve water quality after treatment and pose no negative effects on aquatic ecosystems.


Assuntos
Argila/química , Proliferação Nociva de Algas/fisiologia , Modelos Teóricos , Antioxidantes/análise , Organismos Aquáticos/metabolismo , Contagem de Células , China , Floculação , Geografia , Fotossíntese , Fitoplâncton/citologia , Fitoplâncton/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Eletricidade Estática , Transcrição Genética , Qualidade da Água
17.
Appl Opt ; 56(30): 8362-8371, 2017 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-29091614

RESUMO

Phytoplankton cell size is an important property that affects diverse ecological and biogeochemical processes, and analysis of the absorption and scattering spectra of phytoplankton can provide important information about phytoplankton size. In this study, an inversion method for extracting quantitative phytoplankton cell size data from these spectra was developed. This inversion method requires two inputs: chlorophyll a specific absorption and scattering spectra of phytoplankton. The average equivalent-volume spherical diameter (ESDv) was calculated as the single size approximation for the log-normal particle size distribution (PSD) of the algal suspension. The performance of this method for retrieving cell size was assessed using the datasets from cultures of 12 phytoplankton species. The estimations of a(λ) and b(λ) for the phytoplankton population using ESDv had mean error values of 5.8%-6.9% and 7.0%-10.6%, respectively, compared to the a(λ) and b(λ) for the phytoplankton populations using the log-normal PSD. The estimated values of CiESDv were in good agreement with the measurements, with r2=0.88 and relative root mean square error (NRMSE)=25.3%, and relatively good performances were also found for the retrieval of ESDv with r2=0.78 and NRMSE=23.9%.


Assuntos
Tamanho Celular , Clorofila/análise , Fitoplâncton/citologia , Contagem de Células , Clorofila A , Cromatografia Líquida de Alta Pressão , Conjuntos de Dados como Assunto , Densitometria/métodos , Fitoplâncton/química , Tecnologia de Sensoriamento Remoto , Especificidade da Espécie
18.
Nat Commun ; 8(1): 1292, 2017 11 03.
Artigo em Inglês | MEDLINE | ID: mdl-29101388

RESUMO

Cell mortality is a key mechanism that shapes phytoplankton blooms and species dynamics in aquatic environments. Here we show that sterol sulfates (StS) are regulatory molecules of a cell death program in Skeletonema marinoi, a marine diatom-blooming species in temperate coastal waters. The molecules trigger an oxidative burst and production of nitric oxide in a dose-dependent manner. The intracellular level of StS increases with cell ageing and ultimately leads to a mechanism of apoptosis-like death. Disrupting StS biosynthesis by inhibition of the sulfonation step significantly delays the onset of this fatal process and maintains steady growth in algal cells for several days. The autoinhibitory activity of StS demonstrates the functional significance of small metabolites in diatoms. The StS pathway provides another view on cell regulation during bloom dynamics in marine habitats and opens new opportunities for the biochemical control of mass-cultivation of microalgae.


Assuntos
Diatomáceas/metabolismo , Microalgas/metabolismo , Fitoplâncton/metabolismo , Esteróis/metabolismo , Colestadienóis/metabolismo , Colestadienóis/toxicidade , Ésteres do Colesterol/metabolismo , Ésteres do Colesterol/toxicidade , Diatomáceas/citologia , Diatomáceas/efeitos dos fármacos , Ecossistema , Eutrofização/efeitos dos fármacos , Eutrofização/fisiologia , Microalgas/citologia , Microalgas/efeitos dos fármacos , Filogenia , Fitoplâncton/citologia , Fitoplâncton/efeitos dos fármacos , Fitosteróis/metabolismo , Fitosteróis/toxicidade , Transdução de Sinais , Sitosteroides/metabolismo , Sitosteroides/toxicidade , Esteróis/toxicidade , Sulfatos/metabolismo , Sulfatos/toxicidade , Sulfotransferases/genética , Sulfotransferases/metabolismo
19.
PLoS One ; 12(7): e0181720, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28742122

RESUMO

Periphytic algae are important components of aquatic ecosystems. However, the factors driving periphyton species richness variation remain largely unexplored. Here, we used data from a subtropical floodplain (Upper Paraná River floodplain, Brazil) to quantify the influence of environmental variables (total suspended matter, temperature, conductivity, nutrient concentrations, hydrology, phytoplankton biomass, phytoplankton species richness, aquatic macrophyte species richness and zooplankton density) on overall periphytic algal species richness and on the richness of different algal groups defined by morphological traits (cell size and adherence strategy). We expected that the coefficients of determination of the models estimated for different trait-based groups would be higher than the model coefficient of determination of the entire algal community. We also expected that the relative importance of explanatory variables in predicting species richness would differ among algal groups. The coefficient of determination for the model used to predict overall periphytic algal species richness was higher than the ones obtained for models used to predict the species richness of the different groups. Thus, our first prediction was not supported. Species richness of aquatic macrophytes was the main predictor of periphyton species richness of the entire community and a significant predictor of the species richness of small mobile, large mobile and small-loosely attached algae. Abiotic variables, phytoplankton species richness, chlorophyll-a concentration, and hydrology were also significant predictors, depending on the group. These results suggest that habitat heterogeneity (as proxied by aquatic macrophytes richness) is important for maintaining periphyton species richness in floodplain environments. However, other factors played a role, suggesting that the analysis of species richness of different trait-based groups unveils relationships that were not detectable when the entire community was analysed together.


Assuntos
Biodiversidade , Fitoplâncton , Zooplâncton , Animais , Biomassa , Brasil , Adesão Celular , Tamanho Celular , Clorofila/análise , Clorofila A , Clorófitas/citologia , Clorófitas/crescimento & desenvolvimento , Clorófitas/fisiologia , Fitoplâncton/citologia , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/fisiologia , Densidade Demográfica , Dinâmica Populacional , Zooplâncton/citologia , Zooplâncton/crescimento & desenvolvimento , Zooplâncton/fisiologia
20.
J Phycol ; 53(4): 889-907, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28593733

RESUMO

The diatom genus Chaetoceros is one of the most abundant and diverse phytoplankton in marine and brackish waters worldwide. Within this genus, Chaetoceros socialis has been cited as one of the most common species. However, recent studies from different geographic areas have shown the presence of pseudo-cryptic diversity within the C. socialis complex. Members of this complex are characterized by curved chains (primary colonies) aggregating into globular clusters, where one of the four setae of each cell curves toward the center of the cluster and the other three orient outwards. New light and electron microscopy observations as well as molecular data on marine planktonic diatoms from the coastal waters off Chile revealed the presence of two new species, Chaetoceros sporotruncatus sp. nov. and C. dichatoensis. sp. nov. belonging to the C. socialis complex. The two new species are similar to other members of the complex (i.e., C. socialis and C. gelidus) in the primary and secondary structure of the colony, the orientation pattern of the setae, and the valve ultrastructure. The only morphological characters that can be used to differentiate the species of this complex are aspects related to resting spore morphology. The two newly described species are closely related to each other and form a sister clade to C. gelidus in molecular phylogenies. We also provide a phylogenetic status along with the morphological characterization of C. radicans and C. cintus, which are genetically related to the C. socialis complex.


Assuntos
Diatomáceas/classificação , Filogenia , Fitoplâncton/classificação , Chile , DNA de Algas/genética , Diatomáceas/citologia , Diatomáceas/genética , Diatomáceas/ultraestrutura , França , Itália , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Fitoplâncton/citologia , Fitoplâncton/genética , Fitoplâncton/ultraestrutura , RNA Ribossômico 18S/genética , RNA Ribossômico 28S/genética , Análise de Sequência de DNA , Especificidade da Espécie
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