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1.
Mar Pollut Bull ; 145: 105-117, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31590766

RESUMO

The Beagle Channel is a remote subantarctic environment where mussel aquaculture initiatives have existed since the early 1990s. Here we analyze phytoplankton biomass and composition, and the occurrence of harmful microalgae species and their toxins at three sites during the period 2015-2016. The occurrence of potentially harmful algae was observed throughout the study period, including toxigenic dinoflagellates such as Alexandrium catenella (Group I of the A. tamarense complex), A. ostenfeldii, Dinophysis acuminata, Gonyaulax spinifera, Azadinium sp., and the diatoms Pseudo-nitzschia australis and P. fraudulenta. Toxic dinoflagellates were detected in low densities whereas a Pseudo-nitzschia bloom was observed in late February. Isolates of A. catenella and P. delicatissima sensu stricto were phylogenetically characterized. The toxin profile of A. catenella was dominated by GTX4, while P. delicatissima sensu stricto showed no production of the neurotoxin domoic acid in culture conditions. The results provide base-line information for the management of harmful algal blooms in this little explored subantarctic area.


Assuntos
Aquicultura , Diatomáceas/química , Dinoflagelados/química , Toxinas Marinhas/análise , Fitoplâncton/química , Animais , Biomassa , Diatomáceas/classificação , Diatomáceas/crescimento & desenvolvimento , Dinoflagelados/classificação , Dinoflagelados/crescimento & desenvolvimento , Proliferação Nociva de Algas , Microalgas/química , Microalgas/classificação , Microalgas/crescimento & desenvolvimento , Fitoplâncton/classificação , Fitoplâncton/crescimento & desenvolvimento , América do Sul
2.
Nat Commun ; 10(1): 4234, 2019 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-31530807

RESUMO

Phytoplankton account for nearly half of global primary productivity and strongly affect the global carbon cycle, yet little is known about the forces that drive the evolution of these keystone microscopic organisms. Here we combine morphometric data from the fossil record of the ubiquitous coccolithophore genus Gephyrocapsa with genomic analyses of extant species to assess the genetic processes underlying Pleistocene palaeontological patterns. We demonstrate that all modern diversity in Gephyrocapsa (including Emiliania huxleyi) originated in a rapid species radiation during the last 0.6 Ma, coincident with the latest of the three pulses of Gephyrocapsa diversification and extinction documented in the fossil record. Our evolutionary genetic analyses indicate that new species in this genus have formed in sympatry or parapatry, with occasional hybridisation between species. This sheds light on the mode of speciation during evolutionary radiation of marine phytoplankton and provides a model of how new plankton species form.


Assuntos
Evolução Molecular , Haptófitas/genética , Fitoplâncton/genética , Variação Genética , Genoma , Haptófitas/classificação , Biologia Marinha , Filogenia , Fitoplâncton/classificação
3.
Environ Monit Assess ; 191(10): 603, 2019 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-31482206

RESUMO

The spatial and temporal variation of phytoplankton communities including HAB species in relation to the environmental characteristics was investigated in the protected meso-oligotrophic Mellah lagoon located in the South Western Mediterranean. During 2016, a biweekly monitoring of phytoplankton assemblages and the main abiotic factors were realized at three representative stations. Taxonomic composition, abundance, and diversity index were determined. In total, 227 phytoplankton species (160 diatoms and 53 dinoflagellates) were inventoried. There was a clear dominance of diatoms (62.9%) compared with dinoflagellates (36.8%). Diatoms dominated in spring and dinoflagellates developed in summer and early autumn in Mellah showing a marked seasonal trend. Data showed that the dynamic of the phytoplankton taxa evolving in the lagoon was mainly driven by temperature and salinity. For the first time, a number of potentially toxic species have been identified, including 2 diatoms (Pseudo-nitzschia group delicatissima, Pseudo-nitzschia group seriata) and 5 dinoflagellates (Alexandrium minutum, Alexandrium tamarense/catenella, Dinophysis acuminata, Dinophysis sacculus, Prorocentrum lima). These harmful species could threat the functioning of the Mellah lagoon and human health and require the establishment of a monitoring network. Finally, our study suggests that the observed decrease of the phytoplankton diversity between 2001 and 2016 could result from the reduction in water exchanges between the lagoon and the adjacent coast following the gradual clogging of the channel.


Assuntos
Meio Ambiente , Monitoramento Ambiental , Fitoplâncton/classificação , Estações do Ano , Argélia , Diatomáceas/classificação , Diatomáceas/fisiologia , Dinoflagelados/classificação , Dinoflagelados/fisiologia , Fitoplâncton/fisiologia , Salinidade , Temperatura Ambiente
4.
Nat Microbiol ; 4(10): 1706-1715, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31332382

RESUMO

In the surface ocean, phytoplankton transform inorganic substrates into organic matter that fuels the activity of heterotrophic microorganisms, creating intricate metabolic networks that determine the extent of carbon recycling and storage in the ocean. Yet, the diversity of organic molecules and interacting organisms has hindered detection of specific relationships that mediate this large flux of energy and matter. Here, we show that a tightly coupled microbial network based on organic sulfur compounds (sulfonates) exists among key lineages of eukaryotic phytoplankton producers and heterotrophic bacterial consumers in the North Pacific Subtropical Gyre. We find that cultured eukaryotic phytoplankton taxa produce sulfonates, often at millimolar internal concentrations. These same phytoplankton-derived sulfonates support growth requirements of an open-ocean isolate of the SAR11 clade, the most abundant group of marine heterotrophic bacteria. Expression of putative sulfonate biosynthesis genes and sulfonate abundances in natural plankton communities over the diel cycle link sulfonate production to light availability. Contemporaneous expression of sulfonate catabolism genes in heterotrophic bacteria highlights active cycling of sulfonates in situ. Our study provides evidence that sulfonates serve as an ecologically important currency for nutrient and energy exchange between microbial autotrophs and heterotrophs, highlighting the importance of organic sulfur compounds in regulating ecosystem function.


Assuntos
Bactérias/metabolismo , Eucariotos/metabolismo , Consórcios Microbianos , Fitoplâncton/metabolismo , Água do Mar/microbiologia , Ácidos Sulfônicos/metabolismo , Processos Autotróficos , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Ritmo Circadiano , Eucariotos/classificação , Eucariotos/genética , Eucariotos/isolamento & purificação , Processos Heterotróficos , Luz , Redes e Vias Metabólicas/genética , Oceano Pacífico , Fitoplâncton/classificação , Fitoplâncton/genética , Água do Mar/química , Ácidos Sulfônicos/química
5.
Huan Jing Ke Xue ; 40(5): 2249-2257, 2019 May 08.
Artigo em Chinês | MEDLINE | ID: mdl-31087863

RESUMO

Yilong Lake, a shallow, plateau lake, is the ninth largest water body in the Yunnan Province, China. In order to figure out the characteristics of phytoplankton communities in different regions of this lake, the phytoplankton and environmental factors in the west region, east region, and in a submerged macrophytes restoration demonstration region were monthly investigated and analyzed from August 2013 to July 2014. The results showed that the habitats in different regions were spatially heterogeneous. Total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH4+-N), five-day biochemical oxygen demand (BOD5), transparency (SD), turbidity (Turb.), and electrical conductivity (EC) had no significant differences between the demonstration region and the west region, but these two regions showed significant differences in comparison with the east region (P<0.05). The largest phytoplankton density was Cyanophyta and the dominant species in the three regions were different. Mersmopedia tenuissima had the highest dominance in the west region; Cylindrospermopsis raciborskii and Pseudanabaena limntica were the most dominant taxa in the east region; while Merismopedia tenuissima and Anabaenopsis sp. were dominant in the O. uminata restoration demonstration region. PCoA compared the ß diversity of phytoplankton communities in the three different regions based on the entire year investigations. It was found that the community structures of the west region and O. uminata restoration demonstration region were similar (P>0.05), but they were significantly different from the community from the east region (P<0.01). Redundant analysis (RDA) showed that TN, TP, BOD5, and SD were the main environmental factors affecting the distribution of phytoplankton community in Yilong Lake. In addition, NH4+-N, EC, permanganate index, and pH also have a certain effect on the phytoplankton community.


Assuntos
Lagos , Fitoplâncton/classificação , Fitoplâncton/crescimento & desenvolvimento , Análise da Demanda Biológica de Oxigênio , China , Monitoramento Ambiental , Nitrogênio/análise , Fósforo/análise , Qualidade da Água
6.
Environ Sci Pollut Res Int ; 26(17): 17512-17519, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31025277

RESUMO

Phytoplankton assemblages were investigated in 2015 along the seasonal changes of the Genhe River in the Greater Hinggan Mountains. The survey was performed in June (spring), August (summer), and October (autumn) at nine sampling stations to study the community composition, abundance, and biodiversity. The results showed that 61 species belonging to 16 genera were identified, including Bacillariophyta of 31 species, Dinophyta 2 species, Cyanophyta 2 species, Chlorophyta 20 species, Chrysophyta 2 species, and Cryptophyta 1 species; Besides, Bacillariophyta are dominant species. Shannon-Wiener (H') and Pielou (J') indices indicated that phytoplankton community was stable. And these two indices were significantly lower in summer than in spring and autumn. Phytoplankton abundance and biomass show significant differences in each season. The total phytoplankton abundance (1122.3 × 104 ind/L) and biomass (6.5709 mg/L) in summer are much higher than that in spring and autumn. There were few species and low abundance and biomass in the upper reaches of Genhe River; this fact can be explained by the cold climate in the Greater Higgnan Mountains region. Canonical correspondence analysis (CCA) was used to analyze the data. It revealed that Fe3+, Cu2+, pH, and water temperature (WT) were responsible for most of the variation in space in the phytoplankton community. These environmental parameters play an essential role in the community structure variation of phytoplankton in the upper reaches of Genhe River, the strong association between phytoplankton community structure and ecological factors is varied in each season.


Assuntos
Clorófitas/química , Cianobactérias/química , Diatomáceas/classificação , Dinoflagelados/química , Fitoplâncton/classificação , Rios/química , Biodiversidade , Biomassa , China , Diatomáceas/química , Ecologia , Fitoplâncton/química , Estações do Ano , Temperatura Ambiente , Qualidade da Água
7.
J Microbiol ; 57(4): 252-262, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30929228

RESUMO

Phytoplankton and bacterioplankton play a key role in carbon cycling of aquatic ecosystems. In this study, we found that co-occurrence patterns between different types of phytoplankton, bacterioplankton, and environmental parameters in Lake Baikal during spring were different over the course of three consecutive years. The composition of phytoplankton and bacterial communities was investigated using microscopy and 16S rRNA gene pyrosequencing, respectively. Non-metric multidimensional scaling (NMDS) revealed a relationship between the structure of phytoplankton and bacterial communities and temperature, location, and sampling year. Associations of bacteria with diatoms, green microalgae, chrysophyte, and cryptophyte were identified using microscopy. Cluster analysis revealed similar correlation patterns between phytoplankton abundance, number of attached bacteria, ratio of bacteria per phytoplankton cell and environmental parameters. Positive and negative correlations between different species of phytoplankton, heterotrophic bacteria and environmental parameters may indicate mutualistic or competitive relationships between microorganisms and their preferences to the environment.


Assuntos
Organismos Aquáticos/isolamento & purificação , Bactérias/isolamento & purificação , Lagos/microbiologia , Lagos/parasitologia , Fitoplâncton/isolamento & purificação , Organismos Aquáticos/classificação , Organismos Aquáticos/genética , Bactérias/classificação , Bactérias/genética , Ecossistema , Lagos/química , Filogenia , Fitoplâncton/classificação , Fitoplâncton/genética , Estações do Ano , Temperatura Ambiente
8.
Sci Total Environ ; 667: 338-347, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30833237

RESUMO

Riverine floodplains are among the most diverse and dynamic ecosystems, but river regulation measures have altered the natural hydrological regime threatening their ecological integrity. We compared spatial patterns of phyto- and zooplankton functional diversity and of environmental heterogeneity between floodplain wetlands located in free-flowing and impounded stretches of the Danube River (Austria). We included two nested spatial scales (different habitats and water sections within wetland areas) and two contrasting hydrological conditions (post-flood, no flood). Environmental heterogeneity was lower in the wetland in the impounded stretch than in the free-flowing ones. At post-flood conditions, increased alpha diversity of rotifers and microcrustaceans and decreased beta diversity of phytoplankton and rotifers occurred in the impounded stretch as compared to the wetlands in free-flowing one. Beta diversity was higher between water sections than between habitats in free-flowing wetlands and similar across scales in the wetland in the impounded stretch. Regarding functional composition, the wetland in the impounded stretch hosted more homogeneous communities, as some ecological traits were nearly absent. Our results indicate that patterns of functional diversity in floodplain wetlands affected by river regulation are altered, highlighting the major role of the gradient of lateral connectivity and dynamic water level fluctuations as drivers for planktic diversity in river floodplains. This study contributes with essential knowledge to optimize restoration and diversity conservation measures in riverine ecosystems.


Assuntos
Monitoramento Ambiental , Fitoplâncton/classificação , Áreas Alagadas , Animais , Áustria , Conservação dos Recursos Naturais , Crustáceos , Ecologia , Ecossistema , Inundações , Hidrologia , Fitoplâncton/crescimento & desenvolvimento , Rios
9.
Environ Monit Assess ; 191(4): 201, 2019 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-30826892

RESUMO

Both environmental and geographic factors interact to structure the metacommunities in river networks, but the importance of these factors is difficult to distinguish. We used six aquatic taxonomic groups to test the relationship between environmental and geographic factors and their effect on species turnover patterns in an agriculturally dominated river (Chaohu Lake Basin, China). The relationships between three dissimilarity indices and geographic distance were assessed using the Mantel test while considering the differences in environmental factors between sites. Then, we employed a variation partitioning method to distinguish the isolated and combined effects of environmental and geographic distance on species turnover. There were significant relationships between environmental distance and species turnover in all groups. All organisms except periphytic diatoms were significantly correlated with two geographic (Euclidean and network) distances when the Chao dissimilarity index was considered. The results suggest that the strength of the correlations changed with environmental and geographic distances and with the aquatic community. The communities displayed more complex relationships with the distance measures when different dissimilarity (Jaccard, Chao, and Bray-Curtis dissimilarity) indices were considered. Nevertheless, aquatic communities are strongly influenced by both environmental and geographic distance, and the former has a stronger effect than the latter.


Assuntos
Biodiversidade , Diatomáceas/classificação , Monitoramento Ambiental , Peixes/classificação , Fitoplâncton/classificação , Rotíferos/classificação , Zooplâncton/classificação , Agricultura , Animais , China , Diatomáceas/isolamento & purificação , Geografia , Lagos , Fitoplâncton/isolamento & purificação , Rios , Rotíferos/isolamento & purificação , Zooplâncton/isolamento & purificação
10.
Environ Sci Pollut Res Int ; 26(14): 14266-14276, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30864033

RESUMO

Ecosystem-based management is one of the strategies to protect the coastal areas. One of the key elements is phytoplankton community composition since it represents a good indicator of anthropogenic pressures. This identifies the seasonal patterns of phytoplankton, and its alterations by the stress factors induced by human activities are highly valuable. This research represents the first attempt to study that 476 km of western Mediterranean coastal belongs to the Valencian Community (Spain) based on the phytoplankton composition approach. The water samples during a 5-year period (6757 water samples) were taken to determine its phytoplankton group's dynamics and its relationship with anthropogenic stressors by means of a series of plots and statistical analyses. Diatoms are the group that most contribute to the whole community composition with two periods of maximum abundance. The Prasinophyceae and Cryptophyceae show unimodal patterns varying its maximum values depending on the season. The picocyanobacteria group exhibited the clearest and best-defined pattern. Other groups have no clear seasonal pattern and become abundant in areas of higher anthropogenic pressure. Graphical abstract Figure A contains poor quality of text in image. Otherwise, please provide replacement figure file.A new graphical abstract, with higher quality is attached.


Assuntos
Monitoramento Ambiental/métodos , Fitoplâncton/crescimento & desenvolvimento , Estações do Ano , Poluentes Químicos da Água/análise , Diatomáceas/classificação , Diatomáceas/efeitos dos fármacos , Diatomáceas/crescimento & desenvolvimento , Ecossistema , Humanos , Estudos Longitudinais , Mar Mediterrâneo , Fitoplâncton/classificação , Fitoplâncton/efeitos dos fármacos , Água do Mar/química , Espanha
11.
Environ Monit Assess ; 191(3): 130, 2019 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-30725187

RESUMO

Seasonal water quality analysis helps to evaluate the impact of anthropogenic activities on reservoirs. The water quality may be judged by estimating various chemical parameters like dissolved oxygen (DO), free CO2, total alkalinity, total hardness, pH, Ca++, Mg++, Cl-, NO3-, SO4- bicarbonate, and total dissolved solids (TDS) along with environmental parameters like rainfall and temperature. Most of these abiotic factors are subject to human interventions and are interrelated. This cumulative effect directly influences the biota of the reservoir ecosystem where plankton communities are significant. The current work was carried out with the goal to understand the effect of abiotic factors on planktonic growth in a medium-sized artificial reservoir. The study was attempted to analyze two objectives, which were the variations of parameters with respect to three distinct seasons encountered in the region (summer, monsoon, and winter) and second being the impact of such varying parameters on countable/detectable planktonic diversity. From the water samples collected, 44 genera of planktons belonging to Cyanophyceae, Chlorophyceae, Dinophyceae, Desmids, Bacillariophyceae, and Euglenozoa were identified. There was a marked variation in the seasonal parameters pH, EC, temperature, CO2, and HCO3-. Comparison to the BIS and WHO values shows that though water is not potable, it can be used for agriculture and fishing. Thus, it is necessary that this predominantly rainfed reservoir be maintained for sustainable use.


Assuntos
Monitoramento Ambiental/métodos , Água Doce/química , Fitoplâncton/efeitos dos fármacos , Estações do Ano , Qualidade da Água , Biodiversidade , Índia , Fitoplâncton/classificação , Fitoplâncton/crescimento & desenvolvimento , Dinâmica Populacional , Temperatura Ambiente
12.
Environ Pollut ; 245: 1050-1057, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30682739

RESUMO

Monitoring diverse components of aquatic ecosystems is vital for elucidation of diversity dynamics and processes, which alter freshwater ecosystems, but such studies are seldom conducted. Phytoplankton and zooplankton are integral components which play indispensable parts in the structure and ecological service function of water bodies. However, few studies were made on how zooplankton and phytoplankton community may respond simultaneously to change of circumstance and their mutual relationship. Therefore, we researched synchronously the phytoplankton communities as well as zooplankton communities based on monthly monitoring data from September 2011 to August 2012 in heavily polluted areas and researched their responses to variation in environmental parameters and their mutual relationship. As indicated by Time-lag analysis (TLA), the long-term dynamics of phytoplankton and zooplankton were undergoing directional variations, what's more, there exists significant seasonal variations of phytoplankton and zooplankton communities as indicated by Non-Metric Multidimensional scaling (NMDS) methods. Also, Redundancy Analysis (RDA) demonstrated that environmental indicators together accounted for 25.6% and 50.1% variance of phytoplankton and zooplankton, respectively, indicating that environmental variations affected significantly on the temporal dynamics of phytoplankton as well as zooplankton communities. What's more, variance partioning suggested that the major environmental factors influencing variation structures of zooplankton communities were water temperature, concentration of nitrogen, revealing the dominating driving mechanism which shaped the communities of zooplankton. It was also found that there was significant synchronization between zooplankton biomass and phytoplankton biomass (expressed as Chl-a concentration), which suggested that zooplankton respond to changes in dynamic structure of phytoplankton community and can initiate a decrease in phytoplankton biomass through grazing in a few months.


Assuntos
Monitoramento Ambiental/métodos , Lagos/química , Fitoplâncton/crescimento & desenvolvimento , Qualidade da Água , Zooplâncton/crescimento & desenvolvimento , Animais , Biodiversidade , Biomassa , China , Nitrogênio/análise , Fitoplâncton/classificação , Estações do Ano , Temperatura Ambiente , Poluentes Químicos da Água/análise , Zooplâncton/classificação
13.
Microb Ecol ; 77(2): 288-303, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30019110

RESUMO

Two annual Baltic Sea phytoplankton blooms occur in spring and summer. The bloom intensity is determined by nutrient concentrations in the water, while the period depends on weather conditions. During the course of the bloom, dead cells sink to the sediment where their degradation consumes oxygen to create hypoxic zones (< 2 mg/L dissolved oxygen). These zones prevent the establishment of benthic communities and may result in fish mortality. The aim of the study was to determine how the spring and autumn sediment chemistry and microbial community composition changed due to degradation of diatom or cyanobacterial biomass, respectively. Results from incubation of sediment cores showed some typical anaerobic microbial processes after biomass addition such as a decrease in NO2- + NO3- in the sediment surface (0-1 cm) and iron in the underlying layer (1-2 cm). In addition, an increase in NO2- + NO3- was observed in the overlying benthic water in all amended and control incubations. The combination of NO2- + NO3- diffusion plus nitrification could not account for this increase. Based on 16S rRNA gene sequences, the addition of cyanobacterial biomass during autumn caused a large increase in ferrous iron-oxidizing archaea while diatom biomass amendment during spring caused minor changes in the microbial community. Considering that OTUs sharing lineages with acidophilic microorganisms had a high relative abundance during autumn, it was suggested that specific niches developed in sediment microenvironments. These findings highlight the importance of nitrogen cycling and early microbial community changes in the sediment due to sinking phytoplankton before potential hypoxia occurs.


Assuntos
Bactérias/isolamento & purificação , Cianobactérias/crescimento & desenvolvimento , Diatomáceas/crescimento & desenvolvimento , Sedimentos Geológicos/microbiologia , Fitoplâncton/crescimento & desenvolvimento , Bactérias/classificação , Bactérias/genética , Biomassa , Cianobactérias/classificação , Cianobactérias/genética , Cianobactérias/isolamento & purificação , Diatomáceas/classificação , Diatomáceas/genética , Diatomáceas/isolamento & purificação , Eutrofização , Sedimentos Geológicos/química , Nitratos/análise , Nitratos/metabolismo , Nitritos/análise , Nitritos/metabolismo , Filogenia , Fitoplâncton/classificação , Fitoplâncton/genética , Fitoplâncton/isolamento & purificação , Estações do Ano , Água do Mar/química , Água do Mar/microbiologia
14.
Mar Pollut Bull ; 147: 16-35, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29454492

RESUMO

Ballast water discharges may cause negative impacts to aquatic ecosystems, human health and economic activities by the introduction of potentially harmful species. Fifty untreated ballast water tanks, ten in each port, were sampled in four Adriatic Italian ports and one Slovenian port. Salinity, temperature and fluorescence were measured on board. Faecal indicator bacteria (FIB), phyto- and zooplankton were qualitatively and quantitatively determined to identify the species assemblage arriving in ballast water. FIB exceeded the convention standard limits in 12% of the sampled tanks. Vibrio cholerae was not detected. The number of viable organisms in the size groups (minimum dimension) <50 and ≥10 µm and ≥50 µm resulted above the abundances required from the Ballast Water Management Convention in 55 and 86% of the samples, respectively. This is not surprising as unmanaged ballast waters were sampled. Some potentially toxic and non-indigenous species were observed in both phyto- and zooplankton assemblages.


Assuntos
Fitoplâncton , Navios , Zooplâncton , Animais , Organismos Aquáticos , Bactérias , Ecossistema , Fezes/microbiologia , Espécies Introduzidas , Mar Mediterrâneo , Fitoplâncton/classificação , Salinidade , Inquéritos e Questionários , Temperatura Ambiente , Água/química , Microbiologia da Água , Zooplâncton/classificação
15.
ISME J ; 13(1): 64-75, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30108304

RESUMO

Many species of phytoplankton produce toxins that may provide protection from grazing. In that case one would expect toxin production to be costly; else all species would evolve toxicity. However, experiments have consistently failed to show any costs. Here, we show that costs of toxin production are environment dependent but can be high. We develop a fitness optimization model to estimate rate, costs, and benefits of toxin production, using PST (paralytic shellfish toxin) producing dinoflagellates as an example. Costs include energy and material (nitrogen) costs estimated from well-established biochemistry of PSTs, and benefits are estimated from relationship between toxin content and grazing mortality. The model reproduces all known features of PST production: inducibility in the presence of grazer cues, low toxicity of nitrogen-starved cells, but high toxicity of P-limited and light-limited cells. The model predicts negligible reduction in cell division rate in nitrogen replete cells, consistent with observations, but >20% reduction when nitrogen is limiting and abundance of grazers high. Such situation is characteristic of coastal and oceanic waters during summer when blooms of toxic algae typically develop. The investment in defense is warranted, since the net growth rate is always higher in defended than in undefended cells.


Assuntos
Dinoflagelados/metabolismo , Toxinas Marinhas/metabolismo , Fitoplâncton/metabolismo , Animais , Metabolismo Energético/fisiologia , Modelos Biológicos , Nitrogênio/metabolismo , Fitoplâncton/classificação
16.
Water Environ Res ; 90(12): 2036-2048, 2018 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-30538012

RESUMO

Although stratification in deep lakes is well-discussed, few studies pay attention to thermal structure as well as its influences on stratification of biochemical parameters in subtropical lakes in mountainous cities. Here, we studied the depth profile of temperature and biochemical parameters in Longjing Lake, a subtropical reservoir in a mountainous city. Thermal stratification became strong during summer. Biochemical parameters were strongly associated with thermal structure. Stratification started at 2~6 m depth with a substantial decrease in dissolved oxygen, biochemical oxygen demand (BOD5), chlorophyll a, and pH, corresponding to an increase in total nitrogen, ammonium (), nitrite (), total inorganic nitrogen (TIN), total phosphorus, and soluble reactive phosphorus (SRP) with depth; the majority of biochemical parameters showed slight variations from 12 m downward. Our results indicated the stratification of Longjing Lake was stronger and more stable than the stratification of tropical and temperate lakes in lowland cities.


Assuntos
Biodiversidade , Lagos , Centrais Elétricas , Temperatura Ambiente , Poluentes Químicos da Água/química , Abastecimento de Água , Compostos de Amônio/química , Clorofila A/química , Nitritos/química , Nitrogênio/química , Fósforo/química , Fitoplâncton/classificação , Fitoplâncton/fisiologia
17.
BMC Ecol ; 18(1): 51, 2018 12 03.
Artigo em Inglês | MEDLINE | ID: mdl-30509239

RESUMO

BACKGROUND: Phytoplankton species identification and counting is a crucial step of water quality assessment. Especially drinking water reservoirs, bathing and ballast water need to be regularly monitored for harmful species. In times of multiple environmental threats like eutrophication, climate warming and introduction of invasive species more intensive monitoring would be helpful to develop adequate measures. However, traditional methods such as microscopic counting by experts or high throughput flow cytometry based on scattering and fluorescence signals are either too time-consuming or inaccurate for species identification tasks. The combination of high qualitative microscopy with high throughput and latest development in machine learning techniques can overcome this hurdle. RESULTS: In this study, image based cytometry was used to collect ~ 47,000 images for brightfield and Chl a fluorescence at 60× magnification for nine common freshwater species of nano- and micro-phytoplankton. A deep neuronal network trained on these images was applied to identify the species and the corresponding life cycle stage during the batch cultivation. The results show the high potential of this approach, where species identity and their respective life cycle stage could be predicted with a high accuracy of 97%. CONCLUSIONS: These findings could pave the way for reliable and fast phytoplankton species determination of indicator species as a crucial step in water quality assessment.


Assuntos
Aprendizado Profundo , Monitoramento Ambiental/métodos , Citometria de Fluxo/métodos , Estágios do Ciclo de Vida , Fitoplâncton/classificação , Ensaios de Triagem em Larga Escala/métodos , Fitoplâncton/crescimento & desenvolvimento
18.
PLoS One ; 13(12): e0209857, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30586428

RESUMO

Sydney Harbour is subjected to persistent stress associated with anthropogenic activity and global climate change, but is particularly subjected to pulse stress events associated with stormwater input during episodic periods of high rainfall. Photosynthetic microbes underpin metazoan diversity within estuarine systems and are therefore important bioindicators of ecosystem health; yet how stormwater input affects their occurrence and distribution in Sydney Harbour remains poorly understood. We utilised molecular tools (16S/18S rRNA and petB genes) to examine how the phytoplankton community structure (both prokaryotes and eukaryotes) within Sydney Harbour varies between high and low rainfall periods. The relative proportion of phytoplankton sequences was more abundant during the high rainfall period, comprising mainly of diatoms, an important functional group supporting increased productivity within estuarine systems, together with cyanobacteria. Increased spatial variability in the phytoplankton community composition was observed, potentially driven by the steepened physico-chemical gradients associated with stormwater inflow. Conversely, during a low rainfall period, the proportion of planktonic photosynthetic microbes was significantly lower and the persistent phytoplankton were predominantly represented by chlorophyte and dinoflagellate sequences, with lower overall diversity. Differences in phytoplankton composition between the high and low rainfall periods were correlated with temperature, salinity, total nitrogen and silicate. These results suggest that increased frequency of high-rainfall events may change the composition, productivity and health of the estuary. Our study begins to populate the knowledge gap in the phytoplankton community structure and substantial changes associated with transient environmental perturbations, an essential step towards unravelling the dynamics of primary production in a highly urbanised estuarine ecosystem in response to climate change and other anthropogenic stressors.


Assuntos
Estuários , Fitoplâncton/genética , Austrália , Cianobactérias , Diatomáceas , Monitoramento Ambiental/métodos , Fitoplâncton/classificação , Rios/microbiologia
19.
Nat Commun ; 9(1): 4868, 2018 11 19.
Artigo em Inglês | MEDLINE | ID: mdl-30451846

RESUMO

Variation in ocean C:N:P of particulate organic matter (POM) has led to competing hypotheses for the underlying drivers. Each hypothesis predicts C:N:P equally well due to regional co-variance in environmental conditions and biodiversity. The Indian Ocean offers a unique positive temperature and nutrient supply relationship to test these hypotheses. Here we show how elemental concentrations and ratios vary over daily and regional scales. POM concentrations were lowest in the southern gyre, elevated across the equator, and peaked in the Bay of Bengal. Elemental ratios were highest in the gyre, but approached Redfield proportions northwards. As Prochlorococcus dominated the phytoplankton community, biodiversity changes could not explain the elemental variation. Instead, our data supports the nutrient supply hypothesis. Finally, gyre dissolved iron concentrations suggest extensive iron stress, leading to depressed ratios compared to other gyres. We propose a model whereby differences in iron supply and N2-fixation influence C:N:P levels across ocean gyres.


Assuntos
Carbono/química , Ferro/química , Nitrogênio/química , Fósforo/química , Água do Mar/química , Biodiversidade , Carbono/metabolismo , Oceano Índico , Ferro/metabolismo , Nitrogênio/metabolismo , Fixação de Nitrogênio/fisiologia , Nutrientes/química , Nutrientes/metabolismo , Fósforo/metabolismo , Fitoplâncton/classificação , Fitoplâncton/metabolismo , Prochlorococcus/metabolismo , Água do Mar/microbiologia , Movimentos da Água
20.
Nat Ecol Evol ; 2(11): 1715-1723, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30349092

RESUMO

Diatoms are one of the most abundant and diverse groups of phytoplankton and play a major role in marine ecosystems and the Earth's biogeochemical cycles. Here we combine DNA metabarcoding data from the Tara Oceans expedition with palaeoenvironmental data and phylogenetic models of diversification to analyse the diversity dynamics of marine diatoms. We reveal a primary effect of variation in carbon dioxide partial pressure (pCO2) on early diatom diversification, followed by a major burst of diversification in the late Eocene epoch, after which diversification is chiefly affected by sea level, an influx of silica availability and competition with other planktonic groups. Our results demonstrate a remarkable heterogeneity of diversification dynamics across diatoms and suggest that a changing climate will favour some clades at the expense of others.


Assuntos
Biodiversidade , Diatomáceas/classificação , Filogenia , Fitoplâncton/fisiologia , Dióxido de Carbono/química , Mudança Climática , Código de Barras de DNA Taxonômico , Interações Microbianas , Oceanos e Mares , Fitoplâncton/classificação , Dióxido de Silício/química
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