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1.
Environ Monit Assess ; 192(2): 94, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31907685

RESUMO

A multimetric water quality standards (WQS) attainment indicator (MMI) was created to assess the habitat quality of the Chesapeake Bay and its tidal tributaries. The indicator uses metrics of dissolved oxygen concentrations, water clarity assessments, underwater bay grass acreages, and season-specific chlorophyll a distributions. This suite of metrics is recognized as symptomatic of eutrophication and responsive to nutrient and sediment management actions. Habitat criteria for these metrics were established by the US Environmental Protection Agency (USEPA) to protect the survival, growth, and reproduction of tidal bay living resources. The criteria were adopted into state WQS used to define outcome targets of the regulatory 2010 Chesapeake Bay Total Maximum Daily Load (TMDL). Direct accounting of monitoring results compared with state standards would be the most direct measure of water quality status related to achieving habitat health goal conditions under the TMDL. However, the Chesapeake Bay Program long-term water quality monitoring program that supports Clean Water Act 303d water quality impairment assessments does not provide sufficient measurement resolution across all temporal scales represented in these TMDL-related WQS. Recognizing data and analysis gaps, we developed the indicator to provide estimates of WQS attainment for the Chesapeake Bay. The structure of the indicator uses metrics that have been measured consistently with the historical Chesapeake Bay tidal water quality data collections since 1985. The ability to compute scores on contemporary and historical data will provide for bay-wide and spatially explicit long-term trend evaluations of habitat quality.


Assuntos
Baías/química , Monitoramento Ambiental/métodos , Qualidade da Água/normas , Clorofila A/análise , Ecossistema , Eutrofização/fisiologia , Oxigênio/análise , Estados Unidos , United States Environmental Protection Agency
2.
Artigo em Inglês | MEDLINE | ID: mdl-31450850

RESUMO

Nutrients released from sediments have a significant influence on the water quality in eutrophic lakes and reservoirs. To clarify the internal nutrient load and provide reference for eutrophication control in Yuqiao Reservoir, a drinking water source reservoir in China, pore water profiles and sediment core incubation experiments were conducted. The nutrients in the water (soluble reactive P (SRP), nitrate-N (NO3--N), nitrite-N (NO2--N), and ammonium-N (NH4+-N)) and in the sediments (total N (TN), total P (TP) and total organic carbon (TOC)) were quantified. The results show that NH4+-N was the main component of inorganic N in the pore water. NH4+-N and SRP were higher in the pore water than in the overlying water, and the concentration gradient indicated a diffusion potential from the sediment to the overlying water. The NH4+-N, NO3--N, and SRP fluxes showed significant differences amongst the seasons. The NH4+-N and SRP fluxes were significantly higher in the summer than in other seasons, while NO3--N was higher in the autumn. The sediment generally acted as a source of NH4+-N and SRP and as a sink for NO3--N and NO2--N. The sediments release 1133.15 and 92.46 tons of N and P, respectively, to the overlying water each year.


Assuntos
Monitoramento Ambiental , Sedimentos Geológicos/química , Lagos/química , Poluentes Químicos da Água/análise , China , Monitoramento Ambiental/métodos , Eutrofização/fisiologia , Humanos , Nutrientes , Análise Espaço-Temporal , Qualidade da Água/normas
3.
Environ Monit Assess ; 191(9): 586, 2019 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-31440835

RESUMO

Lakes and reservoirs around the world are facing a substantial water quality degradation problem that poses significant environmental, social, and economic impacts. Reservoir productivity is influenced primarily by the climatic, morphometric, and hydro-edaphic features. High nutrient loadings in the reservoir from agriculture runoff often provide ideal conditions for algal blooms, leading to eutrophication. Reservoir and lake management to prevent or reduce eutrophication, therefore, has become the need of the hour. The traditional approach of trophic state monitoring by rigorous field surveys and eutrophication modeling has been revised in the present study by developing a new trophic state index (TSI)-based model for tropical shallow freshwater reservoirs. The new model has been constructed based on Carlson's Limnology and Oceanography, 22, 361-369, (1977) guidelines by establishing an empirical relationship between trophic parameters including total phosphorus (TP), Secchi disk depth (SDD), and chlorophyll (Chl-a). After comparing the new model with various earlier models for its applicability and validation with actual field conditions, it was found to be most precise over previous TSI models. Temporal and spatial fluctuations in the water quality of the Tiru reservoir were primarily attributed to the changing climatic conditions during the study period. Seasonal monsoon with less frequency, heavy nutrient loading from agriculture runoff, and increased turbidity due to a high level of sediment inflow during monsoon raised the TSI (SDD) values of the Tiru reservoir to place it in the hyper-eutrophic class. Average TSI values during winter for SDD, Chl-a, and TP were indicative of the meso-eutrophic to eutrophic state. Saturation of nutrients due to low water level during summer season caused the poly-eutrophic condition for TSI (SDD)- and TSI (TP)-based estimates and eutrophic condition as per TSI (Chl-a) estimates. However, seasonal deviations of the TSI values based on the relationship between TSI (Chl-a) and TSI (SD) indicated a predominance of smaller particles (non-algal turbidity) during all seasons. Even though TP present in the Tiru reservoir is controlling the algal production, it is also affected by low-light conditions due to non-algal turbidity. The recommendation from this study is that the TSI method for estimating the health of the water bodies is the efficient, cost-effective, and time-saving approach. The model developed during the study would help managers and policy makers to take necessary steps to reduce eutrophication levels in the reservoir and would be helpful for researchers in developing new concepts and protocols, mainly focusing on shallow freshwater reservoirs.


Assuntos
Clorofila/análise , Monitoramento Ambiental/métodos , Eutrofização/fisiologia , Fósforo/análise , Poluentes Químicos da Água/análise , Agricultura , Clima , Lagos/química , Modelos Teóricos , Estações do Ano , Qualidade da Água , Abastecimento de Água
4.
Artigo em Inglês | MEDLINE | ID: mdl-31159184

RESUMO

To study the microbial community structure in sediments and its relation to eutrophication environment factors, the sediments and the overlying water of Sancha Lake were collected in the four seasons. MiSeq high-throughput sequencing was conducted for the V3-V4 hypervariable regions of the 16S rRNA gene and was used to analyze the microbial community structure in sediments. Pearson correlation and redundancy analysis (RDA) were conducted to determine the relation between microbial populations and eutrophic factors. The results demonstrated four main patterns: (1) in the 36 samples that were collected, the classification annotation suggested 64 phyla, 259 classes, 476 orders, 759 families, and 9325 OTUs; (2) The diversity indices were ordered according to their values as with summer > winter > autumn > spring; (3) The microbial populations in the four seasons belonged to two distinct characteristic groups; (4) pH, dissolved oxygen (DO), total phosphorus (TP), and total nitrogen (TN) had significant effects on the community composition and structure, which further affected the dissolved total phosphorus (DTP) significantly. The present study demonstrates that the microbial communities in Sancha Lake sediments are highly diverse, their compositions and distributions are significantly different between spring and non-spring, and Actinobacteria and Cyanobacteria may be the key populations or indicator organisms for eutrophication.


Assuntos
Eutrofização/fisiologia , Sedimentos Geológicos/química , Lagos/microbiologia , Microbiota , Actinobacteria/crescimento & desenvolvimento , China , Cianobactérias/crescimento & desenvolvimento , Concentração de Íons de Hidrogênio , Nitrogênio/análise , Oxigênio/análise , Fósforo/análise , RNA Ribossômico 16S , Estações do Ano
5.
Environ Pollut ; 252(Pt B): 1325-1334, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31252130

RESUMO

The ammonium (NH4+) pool in the water column of eutrophic lakes is dynamic and undergoes tightly coupled production and consumption processes because of the metabolism of bacterial and algal communities, particularly in summer. However, NH4+ recycling rates along nutrient gradients at river-lake transitional zones and the extent to which NH4+ regeneration can compensate for consumption have been poorly studied. In August (flood period) and November (normal period), 2016, NH4+ regeneration rates (REGs) and potential uptake rates (Upots) were measured in northwestern Lake Taihu and adjacent rivers. Results showed that the REGs ranged from 0.09 to 3.30 µmol N L-1 h-1 and the Upots ranged from 0.20 to 4.88 µmol N L-1 h-1, with higher recycling rates occurring at the river sites. Yet, the lake sites showed significantly higher water column NH4+ demand (WCAD) than that of the adjacent river sites during both seasons (p < 0.05), probably as a result of the low REGs and the lack of exogenous nitrogen (N) inputs. The flood period showed significantly higher REG and Upot values than those of the normal period (p < 0.05), probably controlled by higher water temperature and algal biomass. This study confirms that regenerated NH4+ was more important than the ambient NH4+ for sustaining cyanobacterial blooms in northwestern Lake Taihu and indicates that the river-lake transitional zones are key areas for N control in this hypereutrophic system.


Assuntos
Compostos de Amônio/metabolismo , Cianobactérias/metabolismo , Lagos/química , Rios/química , China , Eutrofização/fisiologia , Lagos/microbiologia , Nitrogênio/análise , Nutrientes , Rios/microbiologia , Estações do Ano
6.
PLoS One ; 14(4): e0214933, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30951553

RESUMO

Phytoplankton blooms are an important, widespread phenomenon in open oceans, coastal waters and freshwaters, supporting food webs and essential ecosystem services. Blooms are even more important in exploited coastal waters for maintaining high resource production. However, the environmental factors driving blooms in shallow productive coastal waters are still unclear, making it difficult to assess how environmental fluctuations influence bloom phenology and productivity. To gain insights into bloom phenology, Chl a fluorescence and meteorological and hydrological parameters were monitored at high-frequency (15 min) and nutrient concentrations and phytoplankton abundance and diversity, were monitored weekly in a typical Mediterranean shallow coastal system (Thau Lagoon). This study was carried out from winter to late spring in two successive years with different climatic conditions: 2014/2015 was typical, but the winter of 2015/2016 was the warmest on record. Rising water temperature was the main driver of phytoplankton blooms. However, blooms were sometimes correlated with winds and sometimes correlated with salinity, suggesting nutrients were supplied by water transport via winds, saltier seawater intake, rain and water flow events. This finding indicates the joint role of these factors in determining the success of phytoplankton blooms. Furthermore, interannual variability showed that winter water temperature was higher in 2016 than in 2015, resulting in lower phytoplankton biomass accumulation in the following spring. Moreover, the phytoplankton abundances and diversity also changed: cyanobacteria (< 1 µm), picoeukaryotes (< 1 µm) and nanoeukaryotes (3-6 µm) increased to the detriment of larger phytoplankton such as diatoms. Water temperature is a key factor affecting phytoplankton bloom dynamics in shallow productive coastal waters and could become crucial with future global warming by modifying bloom phenology and changing phytoplankton community structure, in turn affecting the entire food web and ecosystem services.


Assuntos
Eutrofização/fisiologia , Modelos Biológicos , Fitoplâncton/crescimento & desenvolvimento , Estações do Ano , Temperatura , Mar Mediterrâneo
7.
PLoS One ; 14(4): e0215463, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30990831

RESUMO

Harmful Algal Blooms (HABs) are of global concern, as their presence is often associated with socio-economic and environmental issues including impacts on public health, aquaculture and fisheries. Therefore, monitoring the occurrence and succession of HABs is fundamental for managing coastal regions around the world. Yet, due to the lack of adequate in situ measurements, the detection of HABs in coastal marine ecosystems remains challenging. Sensors on-board satellite platforms have sampled the Earth synoptically for decades, offering an alternative, cost-effective approach to routinely detect and monitor phytoplankton. The Red Sea, a large marine ecosystem characterised by extensive coral reefs, high levels of biodiversity and endemism, and a growing aquaculture industry, is one such region where knowledge of HABs is limited. Here, using high-resolution satellite remote sensing observations (1km, MODIS-Aqua) and a second-order derivative approach, in conjunction with available in situ datasets, we investigate for the first time the capability of a remote sensing model to detect and monitor HABs in the Red Sea. The model is able to successfully detect and generate maps of HABs associated with different phytoplankton functional types, matching concurrent in situ data remarkably well. We also acknowledge the limitations of using a remote-sensing based approach and show that regardless of a HAB's spatial coverage, the model is only capable of detecting the presence of a HAB when the Chl-a concentrations exceed a minimum value of ~ 1 mg m-3. Despite the difficulties in detecting HABs at lower concentrations, and identifying species toxicity levels (only possible through in situ measurements), the proposed method has the potential to map the reported spatial distribution of several HAB species over the last two decades. Such information is essential for the regional economy (i.e., aquaculture, fisheries & tourism), and will support the management and sustainability of the Red Sea's coastal economic zone.


Assuntos
Biodiversidade , Recifes de Corais , Eutrofização/fisiologia , Modelos Biológicos , Fitoplâncton/crescimento & desenvolvimento , Aquicultura , Oceano Índico
8.
Sci Total Environ ; 676: 62-71, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31029901

RESUMO

Dinoflagellate blooms are the results of rapid cell proliferation governed by cell cycle, a highly-ordered series of events that culminates in cell division. However, little is known about cell cycle progression of the in situ bloom cells. Here, we compared proteomes of the in situ blooming cells of a dinoflagellate Prorocentrum donghaiense collected at different cell cycle phases. The blooming P. donghaiense cells completed a cell cycle within 24 h with a high synchronization rate of 82.7%. Proteins associated with photosynthesis, porphyrin and chlorophyll synthesis, carbon, nitrogen and amino acid metabolisms exhibited high expressions at the G1 phase; DNA replication and mismatch repair related proteins were more abundant at the S phase; while protein synthesis and oxidative phosphorylation were highly enriched at the G2/M phase. Cell cycle proteins presented similar periodic diel patterns to other eukaryotic cells, and higher expressions of proliferating cell nuclear antigen and cyclin dependent kinase 2 at the S phase ensured the smooth S-G2/M transition. Strikingly, four histones were first identified in P. donghaiense and highly expressed at the G2/M phase, indicating their potential roles in regulating cell cycle. This study presents the first quantitative survey, to our knowledge, of proteome changes at different cell cycle phases of the in situ blooming cells in natural environment and provides insights into cell cycle regulation of the blooming dinoflagellate cells.


Assuntos
Dinoflagelados/fisiologia , Eutrofização/fisiologia , Proteoma/metabolismo , Proteômica , Carbono , Ciclo Celular , Nitrogênio , Fotossíntese
9.
Mar Pollut Bull ; 140: 301-307, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30803648

RESUMO

Large-scale green tides caused by Ulva prolifera, occurred for 12 consecutive years in the Yellow Sea of China. To resolve the abrupt shift in species composition between attached and floating macroalgal assemblages, field experiments were conducted from May to July 2017 to quantify the net buoyancy force and compare the floating potential of the common green macroalgae from the red algal seaweed Pyropia yezoensis rafts. At the same time, U. prolifera from different sampling locations were tested to study variable buoyancy of this species and the associated influencing factors. Our results illustrated a stronger positive buoyant force and a proportionally greater buoyancy capacity of U. prolifera, compared to the other co-occurring species. Buoyancy is a dynamic trait and is closely correlated with light intensity, morphology and physiological status. The positive buoyancy of U. prolifera is an important factor that helps explain its predominance in the Yellow Sea's large-scale green tides.


Assuntos
Monitoramento Ambiental/métodos , Eutrofização/fisiologia , Ulva/fisiologia , China , Oceanos e Mares , Estações do Ano , Água do Mar/química , Alga Marinha/fisiologia , Ulva/crescimento & desenvolvimento
10.
Environ Pollut ; 248: 36-47, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30771746

RESUMO

Applications of aluminium (Al) salt or lanthanum (La) modified bentonite (LMB) have become popular methodologies for immobilizing phosphorus (P) in eutrophic lakes. The presence of humic substances, has been shown to inhibit this form of treatment due to the complexation with La/Al. However, the effects of other dissolved organic matter (DOM), especially that derived from phytoplankton (the dominant source in eutrophic lakes) are unknown. In this study, the interaction with La/Al of Suwannee River Standard Humic Acid Standard II (SRHA) and algae-derived DOM (ADOM) were investigated and compared. Differed to SRHA which was dominated by polyphenol-like component (76.8%, C1-SRHA), majority in ADOM were protein-like substance, including 41.9% tryptophan-like component (C2-ADOM) and 21.0% tyrosine-like component (C3-ADOM). Two reactions of complexation and coprecipitation were observed between SRHA/ADOM and La/Al. Complexation dominated at low metal inputs less than 10 µM and coprecipitation was the main reaction at higher metal inputs. For ADOM, the tryptophan-like component (C2-ADOM) was the important component to react with metal. The reaction rate for C2-ADOM with La were about two-third of that for C1-SRHA, indicating that the influence of C2-ADOM was significant during the P immobilization by La/Al-based treatment in eutrophic lakes. The P removal data in the presence of ADOM confirmed the significant inhibition of ADOM. In addition, based on the composition of coprecipitates and relatively biodegradable character of tryptophan-like substances (C2-ADOM), the coprecipitation of ADOM was assumed to reduce the stability of precipitated P in eutrophic lakes. The release of P from the potential biodegradation of the coprecipitates and thus the possible decline of the performance of P immobilization by La/Al-based treatments is an important work in the future.


Assuntos
Alumínio/química , Bentonita/química , Eutrofização/fisiologia , Lagos/química , Lantânio/química , Fósforo/química , Rios/química , Sedimentos Geológicos/química , Substâncias Húmicas/análise , Íons , Fitoplâncton , Espectrometria de Fluorescência/métodos
11.
FEMS Microbiol Ecol ; 95(2)2019 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-30476121

RESUMO

Cyanobacterial blooms are threatening freshwater ecosystems. The physiological basis involved in the onset of cyanobacterial bloom is fundamental to advance in bloom predictions. Generally, cyanobacteria grow until the availability of nitrogen (N), phosphorus (P) or both nutrients becomes limited. Population survival may depend on physiological adjustments to nutrient deficiency as well as on the efficient use of episodic N and P inputs. This study investigated the effect of N inputs on phosphate uptake affinity and activity of N-deficient bloom-forming cyanobacteria. Lake samples dominated by filamentous cyanobacteria were preincubated with and without nitrate addition, and the uptake of [32P] phosphate pulses was measured in the following days. Phosphate uptake kinetics were analyzed with a flow-force model that provides the threshold concentration, reflecting phosphate uptake affinity, and the membrane conductivity coefficient that corresponds to the activity of uptake systems. After 24 h of nitrate preincubation, phosphate uptake kinetics showed a progressive increase in affinity (nanomolar [Pe]A) and activity (25-fold) concomitant with cyanobacterial growth. It was demonstrated that the alleviation of N-deficiency by N inputs boosts the activation of phosphate uptake systems of non-N2-fixing cyanobacteria to sustain growth. Therefore, reduction of dissolved inorganic N levels in lakes is also mandatory to limit cyanobacterial phosphate uptake affinity and activity capabilities.


Assuntos
Cianobactérias/crescimento & desenvolvimento , Eutrofização/fisiologia , Nitratos/metabolismo , Fosfatos/metabolismo , Cianobactérias/metabolismo , Ecossistema , Lagos/microbiologia
12.
Environ Pollut ; 245: 408-418, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30453139

RESUMO

Cyanobacterial blooms are of global concern due to the multiple harmful risks they pose towards aquatic ecosystem and human health. However, information on the fate of organic pollutants mediated by cyanobacterial blooms in eutrophic water remains elusive. In the present study, endocrine disruptive potentials of phytoplankton samples were evaluated throughout a year-long surveillance in a large and eutrophic freshwater lake. Severe cyanobacterial blooms persisted during our sampling campaigns. Estrogenic agonistic, anti-estrogenic, anti-androgenic, and anti-glucocorticogenic effects were observed in the phytoplankton samples using in vitro reporter gene bioassays. 27 endocrine disrupting chemicals (EDCs) of different modes of action were detected in the samples via UPLC-MS/MS system. Results from mass balance analysis indicated that the measured estrogenic activities were greater than the predicted estrogenic potencies from chemical analysis, demonstrating that chemical analysis of targeted EDCs is unable to fully explain the compounds responsible for the observed estrogenicities. Results from Spearman's correlation analysis concluded that the concentrations of ten EDCs in phytoplankton samples were negatively correlated with cyanobacterial biomass, suggesting the potential occurrence of biomass bio-dilution effects of EDCs due to the huge biomass of cyanobacteria during bloom seasons. The present study provided complementary information about the potential endocrine disruptive risks of cyanobacterial blooms, which is important for understanding and regulating EDCs in eutrophic lakes.


Assuntos
Cianobactérias/crescimento & desenvolvimento , Disruptores Endócrinos/análise , Eutrofização/fisiologia , Lagos/química , Fitoplâncton/crescimento & desenvolvimento , Biomassa , China , Cianobactérias/metabolismo , Ecossistema , Humanos , Fitoplâncton/metabolismo , Estações do Ano , Espectrometria de Massas em Tandem , Poluentes Químicos da Água/análise
13.
Mar Drugs ; 16(12)2018 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-30563009

RESUMO

Microalgae are well known as primary producers in the hydrosphere. As sources of natural products, microalgae are attracting major attention due to the potential of their practical applications as valuable food constituents, raw material for biofuels, drug candidates, and components of drug delivery systems. This paper presents a short review of a low-molecular-weight steroid and sphingolipid glycoconjugates, with an analysis of the literature on their structures, functions, and bioactivities. The discussed data on sterols and the corresponding glycoconjugates not only demonstrate their structural diversity and properties, but also allow for a better understanding of steroid biogenesis in some echinoderms, mollusks, and other invertebrates which receive these substances from food and possibly from their microalgal symbionts. In another part of this review, the structures and biological functions of sphingolipid glycoconjugates are discussed. Their role in limiting microalgal blooms as a result of viral infections is emphasized.


Assuntos
Fatores Biológicos/metabolismo , Glicoconjugados/metabolismo , Microalgas/metabolismo , Phycodnaviridae/metabolismo , Biodiversidade , Fatores Biológicos/química , Vias Biossintéticas/fisiologia , Eutrofização/fisiologia , Glicoconjugados/química , Interações Hospedeiro-Patógeno/fisiologia , Microalgas/química , Microalgas/virologia , Estrutura Molecular , Phycodnaviridae/patogenicidade , Serina C-Palmitoiltransferase/metabolismo , Esfingolipídeos/química , Esfingolipídeos/metabolismo , Esteróis/química , Esteróis/metabolismo , Proteínas Virais/metabolismo
14.
Artigo em Inglês | MEDLINE | ID: mdl-30577417

RESUMO

Quinoprotein glucose dehydrogenase (GDH) is the most important enzyme of inorganic phosphorus-dissolving metabolism, catalyzing the oxidation of glucose to gluconic acid. The insoluble phosphate in the sediment is converted into soluble phosphate, facilitating mass reproduction of algae. Therefore, studying the diversity of gcd genes which encode GDH is beneficial to reveal the microbial group that has a significant influence on the eutrophication of water. Taking the eutrophic Sancha Lake sediments as the research object, we acquired samples from six sites in the spring and autumn. A total of 219,778 high-quality sequences were obtained by DNA extraction of microbial groups in sediments, PCR amplification of the gcd gene, and high-throughput sequencing. Six phyla, nine classes, 15 orders, 29 families, 46 genera, and 610 operational taxonomic units (OTUs) were determined, suggesting the high genetic diversity of gcd. Gcd genes came mainly from the genera of Rhizobium (1.63⁻77.99%), Ensifer (0.13⁻56.95%), Shinella (0.32⁻25.49%), and Sinorhizobium (0.16⁻11.88%) in the phylum of Proteobacteria (25.10⁻98.85%). The abundance of these dominant gcd-harboring bacteria was higher in the spring than in autumn, suggesting that they have an important effect on the eutrophication of the Sancha Lake. The alpha and beta diversity of gcd genes presented spatial and temporal differences due to different sampling site types and sampling seasons. Pearson correlation analysis and canonical correlation analysis (CCA) showed that the diversity and abundance of gcd genes were significantly correlated with environmental factors such as dissolved oxygen (DO), phosphorus hydrochloride (HCl⁻P), and dissolved total phosphorus (DTP). OTU composition was significantly correlated with DO, total organic carbon (TOC), and DTP. GDH encoded by gcd genes transformed insoluble phosphate into dissolved phosphate, resulting in the eutrophication of Sancha Lake. The results suggest that gcd genes encoding GDH may play an important role in lake eutrophication.


Assuntos
Sedimentos Geológicos/microbiologia , Glucose Desidrogenase/genética , Lagos/microbiologia , Fósforo/metabolismo , Proteobactérias/genética , China , Eutrofização/fisiologia , Variação Genética , Estações do Ano
15.
Microbiol Res ; 217: 1-13, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30384903

RESUMO

The complicated relationships among environmental microorganisms are regulated by quorum sensing (QS). Understanding QS-based signals could shed light on the interactions between microbial communities in certain environments. Although QS characteristics have been widely discussed, few studies have been conducted on the role of QS in phycospheric microorganisms. Here, we used metagenomics to examine the profile of AI-1 (AinS, HdtS, LuxI) and AI-2 (LuxS) autoinducers from a deeply sequenced microbial database, obtained from a complete dinoflagellate bloom. A total of 3001 putative AI-1 homologs and 130 AI-2 homologs were identified. The predominant member among the AI groups was HdtS. The abundance of HdtS, AinS, and LuxS increased as the bloom developed, whereas the abundance of LuxI showed the opposite trend. Phylogenetic analysis suggested that HdtS and LuxI synthase originated mainly from alpha-, beta-, and gamma-Proteobacteria, whereas AinS synthase originated solely from Vibrionales. In comparison to AI-1, the sequences related to AI-2 (LuxS) demonstrated a much wider taxonomic coverage. Some significant correlations were found between dominant species and QS signals. In addition to the QS, we also performed parallel analysis of the quorum quenching (QQ) sequences. In comparison to QS, the relative abundance of QQ signals was lower; however, an obvious frequency correlation was observed. These results suggested that QS and QQ signals co-participate in regulating microbial communities during an algal bloom. These data helped to reveal the characteristic behavior of algal symbiotic bacteria, and facilitated a better understanding of microbial dynamics during an algal bloom event from a chemical ecological perspective.


Assuntos
Bactérias/genética , Bactérias/metabolismo , Dinoflagelados/microbiologia , Metagenômica/métodos , Microbiota/genética , Microbiota/fisiologia , Percepção de Quorum/genética , Percepção de Quorum/fisiologia , Aciltransferases/genética , Aciltransferases/metabolismo , Bactérias/classificação , Fenômenos Fisiológicos Bacterianos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Liases de Carbono-Enxofre/genética , Liases de Carbono-Enxofre/metabolismo , China , Dinoflagelados/crescimento & desenvolvimento , Eutrofização/fisiologia , Biologia Marinha , Filogenia , Proteobactérias/genética , Proteobactérias/metabolismo , RNA Ribossômico 16S/genética , Água do Mar/microbiologia , Análise de Sequência , Análise de Sequência de Proteína , Homologia de Sequência , Simbiose , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
16.
FEMS Microbiol Ecol ; 94(12)2018 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-30289447

RESUMO

Cyanobacterial blooms are characterized by intense growth of one or few species that will dominate the phytoplankton community for periods of few months to an entire year or more. However, even during persistent blooms, important seasonal changes among dominant species can be observed. Pampulha reservoir is a tropical eutrophic reservoir presenting permanent blooms. To identify the main species in this environment, a closer analysis performed by microscopy and 16S-rRNA DGGE revealed Cylindrospermopsis raciborskii as highly dominant throughout the year. The second most abundant group comprised species belonging to the Microcystis genus. They followed a well-defined seasonal pattern described by interesting species-specific ecological trends. During thermal stratification in the rainy/warmer season, C. raciborskii dominated in the water column, while Microcystis spp. were abundant at the end of the dry season, a period characterized by higher total phosphorus concentrations. Phylogenetic analyses confirmed the two dominant taxa and their seasonal trends. The results showed that cyanobacteria major controlling factors were strongly species dependent, shifting from physical/climate related (stratification) to more chemical driven (nutrients/eutrophication). Identifying these drivers is therefore essential for the understanding of the bloom dynamics and the real risks associated with each species, and to eventually adopt the most appropriate and effective management strategies.


Assuntos
Cylindrospermopsis/classificação , Cylindrospermopsis/crescimento & desenvolvimento , Eutrofização/fisiologia , Microcystis/classificação , Microcystis/crescimento & desenvolvimento , Cylindrospermopsis/genética , Microcystis/genética , Fósforo/análise , Filogenia , Fitoplâncton/classificação , RNA Ribossômico 16S/genética , Estações do Ano
17.
PLoS One ; 13(10): e0205684, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30335857

RESUMO

Assessing algal nutrient limitation is critical for understanding the interaction of primary production and nutrient cycling in streams, and nutrient diffusing substrate (NDS) experiments are often used to determine limiting nutrients such as nitrogen (N) and phosphorus (P). Unexpectedly, many experiments have also shown decreased algal biomass on NDS P treatments compared to controls. To address whether inhibition of algal growth results from direct P toxicity, NDS preparation artifacts, or environmental covariates, we first quantified the frequency of nutrient inhibition in published experiments. We also conducted a meta-analysis to determine whether heterotrophic microbial competition or selective grazing could explain decreases in algal biomass with P additions. We then deployed field experiments to determine whether P-inhibition of algal growth could be explained by P toxicity, differences in phosphate cation (K vs. Na), differences in phosphate form (monobasic vs. dibasic), or production of H2O2 during NDS preparation. We found significant inhibition of algal growth in 12.9% of published NDS P experiments as compared to 4.7% and 3.6% of N and NP experiments. The meta-analysis linear models did not show enhanced heterotrophy on NDS P treatments or selective grazing of P-rich algae. Our field experiments did not show inhibition of autotrophic growth with P additions, but we found significantly lower gross primary productivity (GPP) and biomass-specific GPP of benthic algae on monobasic phosphate salts as compared to dibasic phosphate salts, likely because of reduced pH levels. Additionally, we note that past field experiments and meta-analyses support the plausibility of direct P toxicity or phosphate form (monobasic vs. dibasic) leading to inhibition of algal growth, particularly when other resources such as N or light are limiting. Given that multiple mechanisms may be acting simultaneously, we recommend practical, cost-effective steps to minimize the potential for P- inhibition of algal growth as an artifact of NDS experimental design.


Assuntos
Processos Autotróficos/fisiologia , Microalgas/fisiologia , Nitrogênio/metabolismo , Fenômenos Fisiológicos da Nutrição , Fósforo/metabolismo , Biomassa , Eutrofização/efeitos dos fármacos , Eutrofização/fisiologia , Peróxido de Hidrogênio/metabolismo , Fósforo/toxicidade , Rios
18.
Harmful Algae ; 78: 36-46, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30196923

RESUMO

Macroalgal blooms can trigger adverse biogeochemical conditions at the sediment-water interface of shallow coastal areas, hence threatening critical habitats such as seagrasses meadows. The direction and magnitude of macroalgal blooms impacts on the aquatic ecosystem can be context-dependent, varying according to the local hydrodynamic conditions. Thus, studies investigating the impacts of stagnant algal depositions on the benthos may fail to address realistic situations and interactions which are common in well-flushed systems. This is especially true for the South America coast, where no study has investigated the effects of macroalgal blooms on seagrasses meadows. To fully understand the impacts of macroalgal blooms on sediment biogeochemistry and seagrass habitats across distinct environmental conditions and biogeographical regions, two independent, complementary field experiments replicated the natural temporal patterns of drift macroalgal mats depositions on unvegetated and vegetated (Ruppia maritima meadows) shoals of the Patos Lagoon estuary (PLE), a subtropical, high hydrodynamic system in southern Brazil. Transitory depositions of algal mats alleviated deleterious biogeochemical conditions in the sediment-water interface of unvegetated bottoms. Nevertheless, these unstable algal depositions promoted significant reductions in R. maritima biomass, by reducing their shoot height and density, and rhizome length. That plant biomass reductions were followed by a decrease in the abundance of the dominant infaunal tanaidacean Monokalliapseudes schubarti, indicating that algal impacts on seagrasses were transferred to higher trophic levels. Our results suggest that, although unstable deposition of drift algal mats can attenuate potential adverse impacts at the sediment-water interface, the physical stress during mats advection can still trigger small seagrass losses. This process may diminish the resilience of R. maritima meadows in the PLE, with impacts on estuarine nutrient cycling and secondary production. We conclude that, although harmful drift macroalgal blooms area global phenomenon, the mechanisms through which macroalgae impair seagrass habitats may vary according to the environmental context. Therefore, further studies are necessary to identify the underlying mechanisms of drift macroalgae-seagrass-macrofauna interactions in high hydrodynamic systems and their generality across distinct biogeographical areas.


Assuntos
Alismatales/fisiologia , Biota , Estuários , Eutrofização/fisiologia , Alga Marinha/metabolismo , Biomassa , Brasil
19.
Harmful Algae ; 78: 86-94, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30196928

RESUMO

Recurrent green tides have been recorded in the Yellow Sea for 11 consecutive years. The origin of floating green algae in the Yellow Sea, however, remains a subject of debate. Previous studies suggest that the major bloom-forming green alga Ulva prolifera represent a unique ecotype different from other attached populations of U. prolifera in China. In this study, 97 green algal samples collected during the 2012 green-tide event and from other locations along the coastline of China were analyzed. Based on the sequences of nuclear ribosomal RNA gene (rDNA) internal transcribed spacer (ITS) region and 5S rDNA spacer region, the green alga U. prolifera in the samples were identified. The intraspecific genetic diversity within U. prolifera was then examined using sequences of 5S rDNA spacer and a marker of sequence characterized amplified region (SCAR) highly specific for bloom-forming U. prolifera in the Yellow Sea. The screening results for SCAR marker demonstrated that U. prolifera attached to aquaculture rafts in Subei Shoal belong to the same ecotype of the bloom-forming U. prolifera in the Yellow Sea. These findings offer genetic evidence that aquaculture rafts in Subei Shoal are a major source of floating green algae in the Yellow Sea.


Assuntos
Eutrofização/fisiologia , Variação Genética , Ulva/genética , Aquicultura , China , DNA de Algas/análise , DNA Ribossômico/análise , Marcadores Genéticos , Ulva/classificação
20.
J Theor Biol ; 456: 108-122, 2018 11 07.
Artigo em Inglês | MEDLINE | ID: mdl-30009794

RESUMO

We construct two ordinary-differential-equation models of a predator feeding adaptively on two prey types, and we evaluate the models' ability to fit data on freshwater plankton. We model the predator's switch from one prey to the other in two different ways: (i) smooth switching using a hyperbolic tangent function; and (ii) by incorporating a parameter that changes abruptly across the switching boundary as a system variable that is coupled to the population dynamics. We conduct linear stability analyses, use approximate Bayesian computation (ABC) combined with a population Monte Carlo (PMC) method to fit model parameters, and compare model results quantitatively to data for ciliate predators and their two algal prey groups collected from Lake Constance on the German-Swiss-Austrian border. We show that the two models fit the data well when the smooth transition is steep, supporting the simplifying assumption of a discontinuous prey-switching behavior for this scenario. We thus conclude that prey switching is a possible mechanistic explanation for the observed ciliate-algae dynamics in Lake Constance in spring, but that these data cannot distinguish between the details of prey switching that are encoded in these different models.


Assuntos
Modelos Biológicos , Plâncton/fisiologia , Comportamento Predatório , Animais , Biomassa , Eutrofização/fisiologia , Cadeia Alimentar , Lagos , Método de Monte Carlo , Dinâmica Populacional
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