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1.
Sci Total Environ ; 694: 133773, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31756832

RESUMO

Phytoplankton is the main indicator group for eutrophication in coastal ecosystems, however its high dispersal potential does not enable the assessment of localized effects of coastal nutrient enrichment. Benthic diatoms are sessile microalgae associated with sandy substrates and have the potential to reflect more localized pollution impacts. Although benthic diatoms are widely used bioindicators in freshwater systems, they have rarely been used for assessing the eutrophication status of oligotrophic environments such as the eastern Mediterranean Sea. In the present study, we assess the efficiency of benthic diatoms as bioindicators of nutrient enrichment in oligotrophic coastal systems, by investigating the effect of different physicochemical conditions and nutrient concentrations on the assemblage composition, diversity and individual species populations. To do this, we sampled along a eutrophication gradient formed by anthropogenic nutrient inputs from a metropolitan area. The main driver of assemblage composition, diversity and biomass of diatoms was nitrogen concentration and its temporal and spatial changes. Nitrogen loadings were positively correlated with increased biomass of Cocconeis spp. and negatively correlated with Mastogloia spp. Our findings suggest that in coastal ecosystems of oligotrophic marine ecoregions, benthic diatom assemblage structure and specific taxonomic groups can be reliable predictors of coastal eutrophication offering higher spatial resolution compared to phytoplankton.


Assuntos
Diatomáceas/fisiologia , Ecossistema , Nitrogênio/metabolismo , Biomassa , Monitoramento Ambiental , Eutrofização , Água Doce , Mar Mediterrâneo , Microalgas , Fitoplâncton , Rios
2.
Sci Total Environ ; 688: 960-969, 2019 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-31726578

RESUMO

Fatty acids (FA) are crucial for the maintenance of membrane fluidity and play a central role in metabolic energy storage. Polyunsaturated fatty acids play an essential ecological role since they are key parameters in the nutritional value of algae. Pesticide impacts on fatty acid profiles have been documented in marine microalgae, but remain understudied in freshwater diatoms. The aims of this study were to: 1) investigate the impact of diuron and S-metolachlor on "classical descriptors" (photosynthesis, growth rate, pigment contents, and on the expression levels of target genes in freshwater diatoms), 2) examine the impact of these pesticides on diatom fatty acid profiles and finally, 3) compare fatty acid profiles and "classical descriptor" responses in order to evaluate their complementarity and ecological role. To address this issue, the model freshwater diatom Gomphonema gracile was exposed during seven days to diuron and S-metolachlor at 10 µg.L-1. G. gracile was mostly composed of the following fatty acids: 20:5n3; 16:1; 16:0; 16:3n4; 14:0 and 20:4n6 and highly unsaturated fatty acids were overall the best represented fatty acid class. S-metolachlor decreased the growth rate and chlorophyll a content of G. gracile and induced the expression of cox1, nad5, d1 and cat genes, while no significant impacts were observed on photosynthesis and carotenoid content. In a more global way, S-metolachlor did not impact the fatty acid profiles of G. gracile. Diuron inhibited photosynthesis, growth rate, chlorophyll a content and induced cat and d1 gene expressions but no significant effect was observed on carotenoid content. Diuron decreased the percentage of highly unsaturated fatty acids but increased the percentage of monounsaturated fatty acids. These results demonstrated that fatty acids responded to diuron conversely to pigment content, suggesting that fatty acids can inform on energy content variation in diatoms subjected to herbicide stress.


Assuntos
Acetamidas/toxicidade , Diatomáceas/fisiologia , Diurona/toxicidade , Herbicidas/toxicidade , Ácidos Graxos , Testes de Toxicidade , Poluentes Químicos da Água/toxicidade
3.
Nat Commun ; 10(1): 4167, 2019 09 13.
Artigo em Inglês | MEDLINE | ID: mdl-31519883

RESUMO

Diatoms possess an impressive capacity for rapidly inducible thermal dissipation of excess absorbed energy (qE), provided by the xanthophyll diatoxanthin and Lhcx proteins. By knocking out the Lhcx1 and Lhcx2 genes individually in Phaeodactylum tricornutum strain 4 and complementing the knockout lines with different Lhcx proteins, multiple mutants with varying qE capacities are obtained, ranging from zero to high values. We demonstrate that qE is entirely dependent on the concerted action of diatoxanthin and Lhcx proteins, with Lhcx1, Lhcx2 and Lhcx3 having similar functions. Moreover, we establish a clear link between Lhcx1/2/3 mediated inducible thermal energy dissipation and a reduction in the functional absorption cross-section of photosystem II. This regulation of the functional absorption cross-section can be tuned by altered Lhcx protein expression in response to environmental conditions. Our results provide a holistic understanding of the rapidly inducible thermal energy dissipation process and its mechanistic implications in diatoms.


Assuntos
Diatomáceas/metabolismo , Luz , Diatomáceas/fisiologia , Fotossíntese/fisiologia , Complexo de Proteína do Fotossistema II/metabolismo , Complexo de Proteína do Fotossistema II/fisiologia , Xantofilas/metabolismo
4.
Sci Total Environ ; 697: 134104, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31487584

RESUMO

Information on nanomaterial interactions with co-contaminants, including their influence on toxicity and environment fate in aquatic environment is rather limited. In this study, the effect of multiwall carbon nanotubes (MWCNTs) co-exposure on the toxicity, biodegradation and bioaccumulation of carbamazepine (CAB) in diatom Navicula sp. was evaluated. Results showed that the three tested MWCNTs showed high sorption capability of CAB, especially for hydroxyl-functionalized MWCNT (OH-MWCNT) with a Q0 of 24 and 0.7 times higher than that of two pristine MWCNTs (pMWCNT-1 and pMWCNT-2), respectively. The pMWCNT-1 posed no significant effects on growth of Navicula sp., whereas the algal growth was inhibited by 10 mg L-1 pMWCNT-2 (P < 0.05). The toxicity of pristine MWCNTs to algae increased with the diameters. OH-MWCNT stimulated the growth of Navicula sp. within 72 h, indicating that surface functionality of MWCNTs played a role in toxicity to Navicula sp. The presence of pMWCNT-1 and pMWCNT-2 could significantly aggravate the toxicity of CAB to Navicula sp., while OH-MWCNT exhibited insignificant effect on CAB toxicity. MWCNTs with a concentration of <10 mg L-1 played a protective role in the photosynthetic function of Navicula sp. Both pMWCNT-1 and pMWCNT-2 had no significant effect on the removal of CAB by Navicula sp., but OH-MWCNT could inhibit the degradation of CAB at the end. MWCNT co-exposure suppressed the bioavailability of CAB in Navicula sp. The results from the present study clearly demonstrated that CAB could be sorbed onto the surface of MWCNTs and sorption of CAB on MWCNTs had a key effect on the toxicity, biodegradation and bioaccumulation of CAB. The physicochemical properties and surface functionality of MWNCTs played an important role in toxicity and fate of CAB to Navicula sp.


Assuntos
Carbamazepina/toxicidade , Diatomáceas/fisiologia , Nanotubos de Carbono/química , Poluentes Químicos da Água/toxicidade , Carbamazepina/química , Diatomáceas/efeitos dos fármacos , Testes de Toxicidade , Poluentes Químicos da Água/química
5.
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
6.
Sci Total Environ ; 686: 1262-1271, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31412522

RESUMO

Understanding biodiversity patterns and the role of biotic attributes in governing these patterns remains one of the most important challenges in ecology. Here, taking water depth in Lake Lugu as a typical geographical gradient, we studied how these different taxa, that is bacteria, diatoms and chironomids, respond to the water depth and environmental gradients using molecular and morphological methods. We further evaluated the relative importance of water depth, environmental variables and biotic attributes in explaining biological characteristics, such as biomass, species richness, and community composition. The biomass of chironomids and the richness of bacteria and chironomids showed a nonlinearly decreasing pattern associated with increased water depth, while biomass and species richness of diatoms showed U-shaped and hump-shaped patterns, respectively. The three taxonomic groups all showed increasing dissimilarity with water depth changes, and there was clear cross-taxon congruence among the variations in community composition. Abiotic variables were pivotal in structuring biological characteristics; however, the biotic attributes also explained a unique portion of their variations. This suggests that biotic interactions significantly influenced the patterns of biomass, species richness, and community compositions along the water depth gradient for the three taxonomic groups studied. Our results provide new evidence that biotic attributes could help in predicting the biodiversity of aquatic communities along geographical gradients, such as water depth.


Assuntos
Fenômenos Fisiológicos Bacterianos , Biodiversidade , Chironomidae/fisiologia , Diatomáceas/fisiologia , Lagos , Animais , Organismos Aquáticos/fisiologia , China
7.
BMC Biotechnol ; 19(1): 53, 2019 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-31349823

RESUMO

BACKGROUND: Increasing CO2 emissions have resulted in ocean acidification, affecting marine plant photosynthesis and changing the nutrient composition of marine ecosystems. The physiological and biochemical processes of marine phytoplankton in response to ocean acidification have been reported, but have been mainly focused on growth and photosynthetic physiology. To acquire a thorough knowledge of the molecular regulation mechanisms, model species with clear genetic background should be selected for systematic study. Phaeodactylum tricornutum is a pennate diatom with the characteristics of small genome size, short generation cycle, and easy to transform. Furthermore, the genome of P. tricornutum has been completely sequenced. RESULTS AND DISCUSSION: In this study, P. tricornutum was cultured at high and normal CO2 concentrations. Cell composition changes during culture time were investigated. The 13C isotope tracing technique was used to determine fractional labeling enrichments for the main cellular components. The results suggested that when lipid content increased significantly under high CO2 conditions, total protein and soluble sugar contents decreased. The 13C labeling experiment indicated that the C skeleton needed for fatty acid C chain elongation in lipid synthesis under high CO2 conditions is not mainly derived from NaHCO3 (carbon fixed by photosynthesis). CONCLUSION: This study indicated that breakdown of intracellular protein and soluble sugar provide C skeleton for lipid synthesis under high CO2 concentration.


Assuntos
Proteínas de Algas/metabolismo , Dióxido de Carbono/metabolismo , Carbono/metabolismo , Diatomáceas/metabolismo , Lipídeos/biossíntese , Açúcares/metabolismo , Isótopos de Carbono/metabolismo , Diatomáceas/genética , Diatomáceas/fisiologia , Ecossistema , Concentração de Íons de Hidrogênio , Espaço Intracelular/metabolismo , Lipogênese , Oceanos e Mares , Fotossíntese , Água do Mar/química , Solubilidade , Açúcares/química
8.
Soft Matter ; 15(29): 6014-6026, 2019 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-31309202

RESUMO

Growing demands for bio-friendly antifouling surfaces have stimulated the development of new and ever-improving material paradigms. Despite notable progress in bio-friendly coatings, the biofouling problem remains a critical challenge. In addition to biofouling characteristics, mechanically stressed surfaces such as ship hulls, piping systems, and heat exchangers require long-term durability in marine environments. Here, we introduce a new generation of anti-biofouling coatings with superior characteristics and high mechanical, chemical and environmental durability. In these surfaces, we have implemented the new physics of stress localization to minimize the adhesion of bio-species on the coatings. This polymeric material contains dispersed organogels in a high shear modulus matrix. Interfacial cavitation induced at the interface of bio-species and organogel particles leads to stress localization and detachment of bio-species from these surfaces with minimal shear stress. In a comprehensive study, the performance of these surfaces is assessed for both soft and hard biofouling including Ulva, bacteria, diatoms, barnacles and mussels, and is compared with that of state-of-the-art surfaces. These surfaces show Ulva accumulation of less than 1%, minimal bacterial biofilm growth, diatom attachment of 2%, barnacle adhesion of 0.02 MPa and mussel adhesion of 7.5 N. These surfaces promise a new physics-based route to address the biofouling problem and avoid adverse effects of biofouling on the environment and relevant technologies.


Assuntos
Incrustação Biológica , Estresse Mecânico , Animais , Aderência Bacteriana , Bivalves/fisiologia , Diatomáceas/fisiologia , Flavobacteriaceae/fisiologia , Propriedades de Superfície , Ulva/fisiologia
9.
PLoS One ; 14(5): e0210927, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31048847

RESUMO

Robust inferences of environmental condition come from bioindicators that have strong relationships with stressors and are minimally confounded by extraneous environmental variables. These indicator properties are generally assumed for assemblage-based indicators such as diatom transfer functions that use species abundance data to infer environmental variables. However, failure of assemblage approaches necessitates the interpretation of individual dominant taxa when making environmental inferences. To determine whether diatom species from Laurentian Great Lakes sediment cores have the potential to provide unambiguous inferences of anthropogenic stress, we evaluated fossil diatom abundance against a suite of historical environmental gradients: human population, agriculture, mining, atmospheric nutrient deposition, atmospheric temperature and ice cover. Several diatom species, such as Stephanodiscus parvus, had reliable relationships with anthropogenic stress such as human population. However, many species had little or no indicator value or had confusing relationships with multiple environmental variables, suggesting one should be careful when using those species to infer stress in the Great Lakes. Recommendations for future approaches to refining diatom indicators are discussed, including accounting for the effects of broad species geographic distributions to minimize region-specific responses that can weaken indicator power.


Assuntos
Diatomáceas/fisiologia , Agricultura , Ecossistema , Monitoramento Ambiental/métodos , Sedimentos Geológicos/análise , Lagos
10.
Aquat Toxicol ; 212: 20-27, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31039523

RESUMO

Polybrominated diphenyl ethers (PBDEs), a series of highly persistent organic pollutants (POPs), are ubiquitous in marine ecosystems. As key primary producers, microalgae are of great importance on evaluating the environmental outcome of PBDEs pollution. In this study, the toxic mechanisms of BDE-47 on the marine diatom Thalassiosira pseudonana were evaluated by measuring multiple physiological processes. Three concentrations of BDE-47 (25, 15 and 5 µg L-1) were used along with two controls (blank: no BDE-47 or DMSO; negative control: only DMSO). Experiments lasted 144 h (6 days), in which the actual BDE-47 concentrations, cell densities, nutrient (nitrate and phosphate) uptake, pigment compositions, photosynthetic physiology, cell morphology and cellular contents (organic carbon and nitrogen) were measured at 12-48 h intervals. The toxic mechanisms of BDE-47 on T. pseudonana cells were evaluated by measuring multiple physiological processes including photosynthesis, nutrient uptake, cellular material synthesis and cell cycle progressions. The cell divisions of T. pseudonana were severely inhibited by the stress of BDE-47, but the photosynthetic parameters were much less declined and recovered earlier than the cell divisions in the same BDE-47 treatments. The unsuppressed uptake rates of nutrients, increased cell volume and cellular contents indicated the cellular material synthesis proceeded normally. Finally, we found that the cell cycle was arrested in G2/M phase under the stress of BDE-47, we thus concluded that the inhibition of cell divisions by BDE-47 was not due to the lack of energy or cellular materials, where the cell cycle arrest happened; this might be the most important toxicological outcome.


Assuntos
Diatomáceas/efeitos dos fármacos , Diatomáceas/fisiologia , Éteres Difenil Halogenados/toxicidade , Fenômenos Fisiológicos/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Carbono/metabolismo , Ciclo Celular/efeitos dos fármacos , Diatomáceas/citologia , Diatomáceas/crescimento & desenvolvimento , Nitrogênio/metabolismo , Fotossíntese/efeitos dos fármacos , Complexo de Proteína do Fotossistema II/metabolismo , Pigmentos Biológicos/metabolismo , Estresse Fisiológico/efeitos dos fármacos
11.
Environ Pollut ; 251: 363-371, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31091500

RESUMO

Due to the growing concern about the presence of microplastics (MP) in the environment, the number of studies evaluating the toxicity of these small persistent particles on different marine species has increased in recent years. Few studies have addressed their impact on marine phytoplankton, a subject of great concern since they are primary producers of the aquatic food web. The aim of this study is to unravel the cytotoxicity of 2.5 µg mL-1 unlabelled amino-modified polystyrene beads of different sizes (0.5 and 2 µm) on the marine diatom Chaetoceros neogracile. In addition to traditional growth and photosynthesis endpoints, several physiological and biochemical parameters were monitored every 24 h in C. neogracile cells by flow cytometry during their exponential growth (72 h). Dynamic Light Scattering measurements revealed the strong aggregation and the negative charge of the beads assayed in the culture medium, which seemed to minimize particle interaction with cells and potentially associated impacts. Indeed, MP were not attached to the microalgal cell wall, as evidenced by scanning electron micrographs. Cell growth, morphology, photosynthesis, reactive oxygen species levels and membrane potential remained unaltered. However, exposure to MP significantly decreased the cellular esterase activity and the neutral lipid content. Microalgal oil bodies could serve as an energy source for maintaining a healthy cellular status. Thus, MP-exposed cells modulate their energy metabolism to properly acclimate to the stress conditions.


Assuntos
Diatomáceas/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Poliestirenos/toxicidade , Poluentes Químicos da Água/toxicidade , Diatomáceas/metabolismo , Diatomáceas/fisiologia , Microesferas , Tamanho da Partícula , Poliestirenos/química , Poluentes Químicos da Água/química
12.
Sci Total Environ ; 680: 79-90, 2019 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-31102831

RESUMO

Diatoms and other phytoplankton groups are exposed to abrupt changes in pCO2, in waters in upwelling areas, near CO2 seeps, or during their blooms; or to more gradual pCO2 rise through anthropogenic CO2 emissions. Gradual CO2 rises have, however, rarely been included in ocean acidification (OA) studies. We therefore compared how small (Thalassiosira pseudonana) and larger (Thalassiosira weissflogii) diatom cell isolates respond to gradual pCO2 rises from 180 to 1000 µatm in steps of ~40 µatm with 5-10 generations at each step, and whether their responses to gradual pCO2 rise differ when compared to an abrupt pCO2 rise imposed from ambient 400 directly to 1000 µatm. Cell volume increased in T. pseudonana but decreased in T. weissflogii with an increase from low to moderate CO2 levels, and then remained steady under yet higher CO2 levels. Growth rates were stimulated, but Chl a, particulate organic carbon (POC) and cellular biogenic silica (BSi) decreased from low to moderate CO2 levels, and then remained steady with further CO2 rise in both species. Decreased saturation light intensity (Ik) and light use efficiency (α) with CO2 rise in T. pseudonana indicate that the smaller diatom becomes more susceptible to photoinhibition. Decreased BSi/POC (Si/C) in T. weissflogii indicates the biogeochemical cycles of both silicon and carbon may be more affected by elevated pCO2 in the larger diatom. The different CO2 modulation methods resulted in different responses of some key physiological parameters. Increasing pCO2 from 180 to 400 µatm decreased cellular POC and BSi contents, implying that ocean acidification to date has already altered diatom contributions to carbon and silicon biogeochemical processes.


Assuntos
Dióxido de Carbono/análise , Diatomáceas/fisiologia , Monitoramento Ambiental , Concentração de Íons de Hidrogênio , Fitoplâncton , Água do Mar/química
13.
Environ Pollut ; 249: 610-619, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30933758

RESUMO

Nowadays, the occurrence of a large volume of plastic litter in oceanic and coastal zones has increased concern about its impacts on marine organisms. The degradation of plastic polymers leads to the formation of smaller fragments at both micro and nano scale (<5 mm and <1 µm respectively). Nanoplastics (NPs), due to their smaller size and high specific surface area can establish colloidal interactions with marine microalgae, therefore potential toxicity can be led. . To assess this hypothesis, the aim of the present study is to examine the behaviour of polystyrene nanoparticles (PS NPs) of different sizes (50 and 100 nm) in marine water and their possible effects at different physiological and cellular levels in the marine diatom Phaeodactylum tricornutum. Different biomarkers and stress responses in P. tricornutum were analysed when organisms were exposed to environmentally relevant PS NPs concentrations between 0.1 and 50 mg L-1. Our results showed significant differences between controls and exposure microalgae, indicating toxicity. After 24 h, an increase in oxidative stress biomarkers, damage to the photosynthetic apparatus, DNA damage and depolarization of mitochondrial and cell membrane from 5 mg L-1 were observed. Further after 72 h the inhibition of population growth and chlorophyll content were observed. Examining effects the effects related to PS NPs size, the smallest (50 nm) induced greater effects at 24 h while bigger PS NPs (100 nm) at72 h. This bigger particles (100 nm) showed more stability (in size distribution and spherical form) in the different culture media assayed, when compared with the rest of particles used. Strong adsorption and/or internalization of PS NPs was confirmed through changes in cell complexity and cell size as well as the fluorescence of 100 nm fluoresbrite PS NPs after washing cell surface.


Assuntos
Diatomáceas/crescimento & desenvolvimento , Microalgas/efeitos dos fármacos , Nanopartículas/toxicidade , Fitoplâncton/crescimento & desenvolvimento , Poliestirenos/toxicidade , Poluentes Químicos da Água/toxicidade , Clorofila/metabolismo , Dano ao DNA/efeitos dos fármacos , Diatomáceas/efeitos dos fármacos , Diatomáceas/fisiologia , Água Doce , Membranas Mitocondriais/patologia , Estresse Oxidativo , Fotossíntese/efeitos dos fármacos , Fitoplâncton/efeitos dos fármacos , Fitoplâncton/fisiologia , Água/metabolismo
14.
Photosynth Res ; 141(3): 355-365, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30993504

RESUMO

Controlling excitation energy flow is a fundamental ability of photosynthetic organisms to keep a better performance of photosynthesis. Among the organisms, diatoms have unique light-harvesting complexes, fucoxanthin chlorophyll (Chl) a/c-binding proteins. We have recently investigated light-adaptation mechanisms of a marine centric diatom, Chaetoceros gracilis, by spectroscopic techniques. However, it remains unclear how pennate diatoms regulate excitation energy under different growth light conditions. Here, we studied light-adaptation mechanisms in a marine pennate diatom Phaeodactylum tricornutum grown at 30 µmol photons m-2 s-1 and further incubated for 24 h either in the dark, or at 30 or 300 µmol photons m-2 s-1 light intensity, by time-resolved fluorescence (TRF) spectroscopy. The high-light incubated cells showed no detectable oxygen-evolving activity of photosystem II, indicating the occurrence of a severe photodamage. The photodamaged cells showed alterations of steady-state absorption and fluorescence spectra and TRF spectra compared with the dark and low-light adapted cells. In particular, excitation-energy quenching is significantly accelerated in the photodamaged cells as shown by mean lifetime analysis of the Chl fluorescence. These spectral changes by the high-light treatment may result from arrangements of pigment-protein complexes to maintain the photosynthetic performance under excess light illumination. These growth-light dependent spectral properties in P. tricornutum are largely different from those in C. gracilis, thus providing insights into the different light-adaptation mechanisms between the pennate and centric diatoms.


Assuntos
Diatomáceas/fisiologia , Diatomáceas/efeitos da radiação , Luz , Clorofila/metabolismo , Oxigênio/metabolismo , Espectrometria de Fluorescência , Fatores de Tempo
15.
Aquat Toxicol ; 211: 148-162, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30981038

RESUMO

This study screened binary mixtures of pesticides for potential synergistic interaction effects on growth of the marine microalgae Tisochrysis lutea and Skeletonema marinoi. It also examined the single and combined effects of three of the most toxic substances on microalgal physiology. Single substances were first tested on each microalgal species to determine their respective EC50 and concentration-response relationships. The toxicity of six and seven binary mixtures was then evaluated in microplate experiments on the growth of T. lutea and S. marinoi, respectively, using two mixture modelling approaches: isobolograms and the MIXTOX tool, based on Concentration Addition (CA) or Independent Action (IA) models. Significant cases of antagonism (for both species) and synergism (for S. marinoi) were observed for the mixtures of isoproturon and spiroxamine, and isoproturon and metazachlor, respectively. These two mixtures, together with that of isoproturon and diuron, for which additivity was observed, were further studied for their impacts on the physiology of each species. Exposures were thus made in culture flasks at three concentrations, or concentration combinations for mixtures, selected to cause 25%, 50% and 75% growth rate inhibition. The effects of the selected pesticides singly and in combination were evaluated at three perceived effect concentrations on esterase metabolic activity, relative lipid content, cytoplasmic membrane potential and reactive oxygen species (ROS) content by flow cytometry, and on photosynthetic quantum yield (ϕ'M) by PAM-fluorescence. Isoproturon and diuron singly and in mixtures induced 20-40% decreases in ϕ'M which was in turn responsible for a significant decrease in relative lipid content for both species. Spiroxamine and metazachlor were individually responsible for an increase in relative lipid content (up to nearly 300% for metazachlor on S. marinoi), as well as cell depolarization and increased ROS content. The mixture of isoproturon and metazachlor tested on S. marinoi caused a 28-34% decrease in ϕ'M that was significantly higher than levels induced by each of substances when tested alone. This strong decrease in ϕ'M could be due to a combined effect of these substances on the photosynthetic apparatus, which is likely the cause of the synergy found for this mixture.


Assuntos
Diatomáceas/efeitos dos fármacos , Haptófitas/efeitos dos fármacos , Microalgas/efeitos dos fármacos , Praguicidas/toxicidade , Fotossíntese/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Diatomáceas/fisiologia , Sinergismo Farmacológico , Haptófitas/fisiologia , Microalgas/fisiologia , Praguicidas/metabolismo , Poluentes Químicos da Água/metabolismo
16.
Environ Sci Pollut Res Int ; 26(16): 16388-16395, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30982194

RESUMO

Diatoms are experiencing striking fluctuations in seawater carbonate chemistry in the natural marine environment, especially in coastal seawaters. Here, we show that the diatoms Thalassiosira weissflogii and Phaeodactylum tricornutum, which utilize different carbon acquisition mechanisms, respond differently to short-term changes in seawater carbonate chemistry. Our results showed that T. weissflogii showed significantly higher photosynthetic oxygen evolution rates than that of P. tricornutum at low levels of CO2 or HCO3-. This suggests that T. weissflogii had higher affinities for CO2 or HCO3- when their concentrations were not sufficient to support saturated growth and photosynthesis. While the activity of Rubisco in P. tricornutum positively correlated with carbonic anhydrases (CA), we observed negative relationship between Rubisco and CA activity in the diatom T. weissflogii. These contrasting physiological responses of diatoms with varied carbon acquisition mechanisms indicate different abilities to cope up with abrupt changes in seawater carbonate chemistry. We propose that the ability to respond to varying carbonate chemistry may act as one determinant of the diatom distributions and phytoplankton community structures.


Assuntos
Dióxido de Carbono , Anidrases Carbônicas/metabolismo , Diatomáceas/metabolismo , Ribulose-Bifosfato Carboxilase/metabolismo , Água do Mar/química , Carbono/metabolismo , Diatomáceas/crescimento & desenvolvimento , Diatomáceas/fisiologia , Fotossíntese/fisiologia , Fitoplâncton/metabolismo , Especificidade da Espécie
17.
Mar Pollut Bull ; 141: 1-8, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30955713

RESUMO

As mariculture expands offshore in response to the increasing demand for seafood, a new set of ecological concerns arises. We report on presented phosphate and silicate deficiencies in spring in the Zhangzi Island area, northern Yellow Sea, used for farming scallops. Silicon limitation was observed at up to 77.3% of stations, with an average silicate concentration as low as 1.7 µM in March 2014. Average phosphate concentration decreased from 0.12 to 0.05 µM from March to May. Stoichiometric ratios and absolute concentrations indicate that 78%-90% of stations showed phosphate limitation. Correspondingly, the phytoplankton community shifted from predominately diatoms to dinoflagellates. The higher frequency of nutrient limitation in farmed areas, compared with unseeded areas and northern Yellow Sea in general, imply intensified bottom-up controls on scallop production. The "bottle-neck" effect of limited food availability in spring suggests that carrying capacity was originally overestimated, when calculated from annual primary production.


Assuntos
Aquicultura/métodos , Diatomáceas/fisiologia , Dinoflagelados/fisiologia , Fitoplâncton/fisiologia , Animais , China , Nutrientes , Pectinidae , Fosfatos/análise , Estações do Ano
18.
Mar Pollut Bull ; 141: 550-560, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30955767

RESUMO

The relative importance of organic nitrogen (ON) and inorganic nitrogen (IN) as nitrogen sources for the phytoplankton communities were studied through a seasonal time series of nitrogen species in the eastern Arabian Sea. Seasonal data on nitrogen species showed that ON dominates the system throughout the year and account for >90% of the total nitrogen (TN) during north east monsoon (NEM). The average ON concentration in the study region was 11.5 µM during NEM as compared to 7.2 µM during south west monsoon (SWM). The contribution of picoplankton to the total phytoplankton pool (fpico) increased from 19% during SWM to 36% in NEM. Along with cyanobacteria, the diatoms Thalassionema nitzchoides and Thalassiosira sp. and among the dinoflagellates Pronoctiluca sp. were found to proliferate in ON rich waters. We suggest atmospheric deposition, riverine-input, resuspension of bottom sediment and ground water intrusion as the possible sources of ON in the study region.


Assuntos
Nitrogênio/análise , Fitoplâncton/fisiologia , Cianobactérias/fisiologia , Diatomáceas/fisiologia , Dinoflagelados/fisiologia , Monitoramento Ambiental , Índia , Oceano Índico , Estações do Ano
19.
Sci Total Environ ; 669: 711-720, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30893626

RESUMO

Benthic diatoms are useful indicators of the ecological state of river systems. To understand the factors determining benthic diatom metacommunity composition in urban rivers, we studied in situ surface sediment diatom communities from 23 rivers in Shanghai City. Based on our study results on the metacommunity structure of benthic diatoms and hierarchical cluster analysis (HCA), we found substantial differences between restored (G1) and unrestored rivers (G2-G4) in taxa richness, relative abundances, and dominant and indicator taxa of benthic diatoms. The epiphytic diatoms Cocconeis placentula and Amphora libyca var. baltica were representative of the restored rivers (G1), where aquatic macrophytes were more abundant and the water was clearer. The motile epipelic diatoms Navicula recens and Navicula germainii dominated the moderately polluted rivers (G2). The eutrophic taxa Cyclotella meneghiniana, Aulacoseira granulata, and Cyclostephanos tholiformis dominated in G3, which comprised relatively heavily polluted rivers with low organic matter sediment and high disturbance. The polysaprobic taxon Nitzschia palea and the halophilous taxon Fallacia pygmaea represented relatively heavily polluted rivers with a comparatively higher sedimentary salinity (SSal) (G4). Redundancy analysis (RDA) revealed that total phosphorus (TP), dissolved organic carbon (DOC), silicon dioxide (SiO2), dissolved oxygen (DO), Secchi depth (SD), SSal, and the ratio of carbon to nitrogen (C/N) in the sediment were important environmental factors explaining variation among benthic diatom metacommunity composition. Partial RDA (pRDA) implied that the relative importance of environmental factors in structuring benthic diatom metacommunity was much higher than spatial factors. Classification and regression trees (CART) further indicated that DOC, the sediment C/N ratio, and SSal were the key local environmental factors affecting grouping patterns of benthic diatom metacommunities. Our study proposes that benthic diatom metacommunities respond to the complex characteristics of local environment in urban rivers and provides useful knowledge for consideration in the ecological monitoring of urban river systems.


Assuntos
Diatomáceas/fisiologia , Ecossistema , Monitoramento Ambiental , Rios/química , Carbono , China , Cidades , Nitrogênio , Fósforo , Dióxido de Silício
20.
Environ Monit Assess ; 191(4): 228, 2019 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-30888530

RESUMO

We assessed how diatom metrics were related to different ranges of agricultural land use. Diatom assemblage composition, nutrients, and landscape characteristics were determined at 232 sites in eight agriculturally dominated study areas of the continental United States. Two regional groups based on differences in diatom relations to human disturbance were determined. Changes in diatom species composition were related to nutrients, pH, and conductivity in the eastern study areas (due to more wetlands) and more exclusively to nutrients in the west-central study areas. Homogenization of diatom flora among streams was related to high agricultural disturbance at this transcontinental scale. Species traits were developed separately for the east and west-central study groups and calculated two ways: indicator species analysis for taxa in low and high TN or TP conditions and weighted average partial least squares models of TN and TP concentration. These diatom metrics were significantly related to many indicators of agricultural land use in watersheds, especially percent row crops. Further analysis was conducted on only the west-central region due to its larger sample size. Overall, diatom metrics using species responses to N gradients were better related to agricultural land use than were species responses to P gradients. Most nutrient-based diatom metrics changed greatly in response to low ranges of percent row crops, but only a few high N diatom metrics responded to high row crop conditions. The greater response of diatoms to changes in low agriculture conditions may be due to past diatom evolution occurring when most waters had low nutrient conditions.


Assuntos
Agricultura , Diatomáceas/fisiologia , Monitoramento Ambiental/métodos , Monitoramento Ambiental/normas , Nitrogênio/análise , Fósforo/análise , Rios , Áreas Alagadas
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