RESUMEN
Lipids comprise a significant fraction of sinking organic matter in the ocean and play a crucial role in the carbon cycle. Despite this, our understanding of the processes that control lipid degradation is limited. We combined nanolipidomics and imaging to study the bacterial degradation of diverse algal lipid droplets and found that bacteria isolated from marine particles exhibited distinct dietary preferences, ranging from selective to promiscuous degraders. Dietary preference was associated with a distinct set of lipid degradation genes rather than with taxonomic origin. Using synthetic communities composed of isolates with distinct dietary preferences, we showed that lipid degradation is modulated by microbial interactions. A particle export model incorporating these dynamics indicates that metabolic specialization and community dynamics may influence lipid transport efficiency in the ocean's mesopelagic zone.
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Bacterias , Metabolismo de los Lípidos , Océanos y Mares , Fitoplancton , Bacterias/metabolismo , Bacterias/genética , Bacterias/clasificación , Gotas Lipídicas/metabolismo , Interacciones Microbianas , Microbiota , Agua de Mar/microbiología , Agua de Mar/química , Fitoplancton/metabolismoRESUMEN
Most studies on Cu toxicity relied on indirect physicochemical parameters to predict Cu toxicity resulting from adverse impacts. This study presents a systematic and intuitive picture of Cu toxicity induced by exogenous acidification in phytoplankton Chlamydomonas reinhardtii. We first showed that acidification reduced the algal resistance to environmental Cu stress with a decreased growth rate and increased Cu bioaccumulation. To further investigate this phenomenon, we employed specific fluorescent probes to visualize the intracellular labile Cu pools in different algal cells. Our findings indicated that acidification disrupted the intracellular labile Cu trafficking, leading to a significant increase in labile Cu(I) pools. At the molecular level, Cu toxicity resulted in the inhibition of the Cu(I) import system and activation of the Cu(I) export system in acidic algal cells, likely a response to the imbalance in intracellular labile Cu trafficking. Subcellular analysis revealed that Cu toxicity induced extensive mitochondrial dysfunction and impacted the biogenesis and assembly of the respiratory chain complex in acidic algal cells. Concurrently, we proposed that the activation of polyP synthesis could potentially regulate disrupted intracellular labile Cu trafficking. Our study offers an intuitive, multilevel perspective on the origins and impacts of Cu toxicity in living organisms, providing valuable insights on metal toxicity.
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Cobre , Mitocondrias , Fitoplancton , Cobre/toxicidad , Fitoplancton/efectos de los fármacos , Fitoplancton/metabolismo , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Chlamydomonas reinhardtii/metabolismo , Chlamydomonas reinhardtii/efectos de los fármacosRESUMEN
Low-latitude (LL) oceans account for up to half of global net primary production and export1-5. It has been argued that the Southern Ocean dominates LL primary production and export6, with implications for the response of global primary production and export to climate change7. Here we applied observational analyses and sensitivity studies to an individual model to show, instead, that 72% of LL primary production and 55% of export is controlled by local mesopelagic macronutrient cycling. A total of 34% of the LL export is sustained by preformed macronutrients supplied from the Southern Ocean via a deeper overturning cell, with a shallow preformed northward supply, crossing 30° S through subpolar and thermocline water masses, sustaining only 7% of the LL export. Analyses of five Coupled Model Intercomparison Project Phase 6 (CMIP6) models, run under both high-emissions low-mitigation (shared socioeconomic pathway (SSP5-8.5)) and low-emissions high-mitigation (SSP1-2.6) climate scenarios for 1850-2300, revealed significant across-model disparities in their projections of not only the amplitude, but also the sign, of LL primary production. Under the stronger SSP5-8.5 forcing, with more substantial upper-ocean warming, the CMIP6 models that account for temperature-dependent remineralization promoted enhanced LL mesopelagic nutrient retention under warming, with this providing a first-order contribution to stabilizing or increasing, rather than decreasing, LL production under high emissions and low mitigation. This underscores the importance of a mechanistic understanding of mesopelagic remineralization and its sensitivity to ocean warming for predicting future ecosystem changes.
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Organismos Acuáticos , Ecosistema , Nutrientes , Océanos y Mares , Agua de Mar , Movimientos del Agua , Calentamiento Global , Nutrientes/metabolismo , Fitoplancton/metabolismo , Agua de Mar/química , Temperatura , Clima Tropical , Organismos Acuáticos/metabolismo , Movimiento (Física)RESUMEN
The neurotoxin ß-N-methylamino-L-alanine (BMAA), produced by cyanobacteria and diatoms, has been implicated as an environmental risk factor for neurodegenerative diseases. This study first investigated the occurrence and monthly distributions of BMAA and its isomers, 2,4-diaminobutyric acid (DAB) and N-2-aminoethylglycine (AEG), in phytoplankton and mussels from 11 sites along the South Sea Coast of Korea throughout 2021. These toxins were quantified using LC-MS/MS, revealing elevated BMAA concentrations from late autumn to spring, with phase lags observed between phytoplankton and mussels. The highest concentration of BMAA in phytoplankton was detected in November (mean: 1490 ng g-1 dry weight (dw)), while in mussels, it peaked in December (mean: 1240 ng g-1 dw). DAB was detected in phytoplankton but was absent in mussels, indicating limited bioaccumulation potential. In February, the peak mean DAB concentration in phytoplankton was 89 ng g-1 dw. AEG was not detected in any samples. Chlorophyll-a concentrations consistently showed an inverse correlation with BMAA concentrations in mussels throughout the year. Through correlation analysis, four diatom genera, Bacillaria, Hemiaulus, Odontella, and Pleurosigma, were identified as potential causative microalgae of BMAA. This study offers insights into identifying the causative microalgae for BMAA and informs future regulatory efforts regarding unmanaged biotoxins.
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Aminoácidos Diaminos , Bivalvos , Toxinas de Cianobacterias , Microalgas , Neurotoxinas , Fitoplancton , Aminoácidos Diaminos/análisis , República de Corea , Animales , Fitoplancton/metabolismo , Microalgas/metabolismo , Microalgas/química , Bivalvos/metabolismo , Bivalvos/química , Neurotoxinas/análisis , Monitoreo del Ambiente , Aminobutiratos/análisis , Glicina/análogos & derivados , Glicina/análisis , Diatomeas/metabolismo , Estaciones del Año , Espectrometría de Masas en Tándem , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/metabolismoRESUMEN
Global climate change has generated an increasing number of environmental problems, especially in Mediterranean coastal areas, such as the Po Delta (PD), where shellfish production has undergone an overall decline because of strong environmental changes. The present study is centred on assessing the fundamental ecological aspects in one of the most crucial European shellfish production lagoons, Sacca degli Scardovari (SC), addressing phytoplankton community parameters directly affecting shellfish production, namely, chemotaxonomic composition, size fractions, and total biomass, in relation to the physicochemical properties of the water column and mussel filtering activity. Our findings suggest that the phytoplankton community structure, its role within the lagoon food web and its production cycles depend on two distinct allogenic inputs, which shape the community differently and exert substantial control on shellfish production. At the same time, the suspended mussel biomass strongly controls the phytoplankton size composition, as their growth is largely supported by nanophytoplankton. As the Po River collects the drainage waters of the Italian side of the entire Alpine Arch, the phytoplankton dynamics reported here represent a useful baseline for further addressing issues of climatic changes affecting lagoon ecology. We believe that our study presents an innovative tool for the planning and management of interventions aimed at enhancing national mussel production without neglecting aspects of environmental protection or the integrity of the coastal system, with significant scientific implications.
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Biomasa , Cambio Climático , Fitoplancton , Mariscos , Fitoplancton/crecimiento & desarrollo , Fitoplancton/metabolismo , Animales , Bivalvos/crecimiento & desarrollo , Bivalvos/fisiología , Acuicultura/métodos , Ecosistema , Cadena Alimentaria , Ríos/químicaRESUMEN
Field studies suggest that changes in the stable isotope ratios of phytoplankton communities can be used to track changes in the utilization of different nitrogen sources, i.e., to detect shifts from dissolved inorganic nitrogen (DIN) uptake to atmospheric nitrogen (N2) fixation by diazotrophic cyanobacteria as an indication of nitrogen limitation. We explored changes in the stable isotope signature of the diazotrophic cyanobacterium Trichormus variabilis in response to increasing nitrate (NO3-) concentrations (0 to 170 mg L-1) under controlled laboratory conditions. In addition, we explored the influence of nitrogen utilization at the primary producer level on trophic fractionation by studying potential changes in isotope ratios in the freshwater model Daphnia magna feeding on the differently grown cyanobacteria. We show that δ 15N values of the cyanobacterium increase asymptotically with DIN availability, from -0.7 in the absence of DIN (suggesting N2 fixation) to 2.9 at the highest DIN concentration (exclusive DIN uptake). In contrast, δ 13C values of the cyanobacterium did not show a clear relationship with DIN availability. The stable isotope ratios of the consumer reflected those of the differently grown cyanobacteria but also revealed significant trophic fractionation in response to nitrogen utilization at the primary producer level. Nitrogen isotope turnover rates of Daphnia were highest in the absence of DIN as a consequence of N2 fixation and resulting depletion in 15N at the primary producer level. Our results highlight the potential of stable isotopes to assess nitrogen limitation and to explore diazotrophy in aquatic food webs.
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Cianobacterias , Daphnia , Fijación del Nitrógeno , Isótopos de Nitrógeno , Nitrógeno , Isótopos de Nitrógeno/metabolismo , Isótopos de Nitrógeno/análisis , Animales , Nitrógeno/metabolismo , Daphnia/metabolismo , Cianobacterias/metabolismo , Cianobacterias/crecimiento & desarrollo , Isótopos de Carbono/análisis , Isótopos de Carbono/metabolismo , Nitratos/metabolismo , Nitratos/análisis , Fitoplancton/metabolismo , Fitoplancton/crecimiento & desarrolloRESUMEN
This theme issue features 18 papers exploring ecological interactions, encompassing metabolic, social, and spatial connections alongside traditional trophic networks. This integration enriches food web research, offering insights into ecological dynamics. By examining links across organisms, populations, and ecosystems, a hierarchical approach emerges, connecting horizontal effects within organizational levels vertically across biological organization levels. The inclusion of interactions involving humans is a key focus, highlighting the need for their integration into ecology given the complex interactions between human activities and ecological systems in the Anthropocene. The comprehensive exploration in this theme issue sheds light on the interconnectedness of ecological systems and the importance of considering diverse interactions in understanding ecosystem dynamics. This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'.
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Ecosistema , Cadena Alimentaria , Humanos , Animales , Actividades Humanas , Fitoplancton/metabolismo , Agua de Mar/microbiología , Peces/metabolismo , Explotaciones Pesqueras/legislación & jurisprudenciaRESUMEN
Phaeocystis globosa is an important bloom-forming marine phytoplankton species that often accumulates to large levels in temperate and tropical waters and has significant impacts on food webs and biogeochemical cycles. It can form "giant" colonies that reach 3 cm in diameter. Microscopic observations, colony elemental composition, and pigment composition were analyzed to assess the characteristics of colonies as a function of colony size. Particulate organic carbon (POC) per unit surface area, colonial cell density, and chlorophyll a per unit surface area all increased with colony size, in contrast to results from temperate waters. Cellular chl a averaged 0.85 pg chl · cell-1. Colonies had both photosynthetic and protective pigments, with fucoxanthin being the dominant accessory pigment. Based on chl a and pigment levels, it appears colonies were acclimated to relatively low irradiances, likely due to their life cycle and the extremely turbulent environment in which they grew. Mucous carbon ranged from 16.2% to 79.2% of the total POC, and mucous carbon per unit surface area increased with colony size, suggesting that the mucous envelope did not thin as the colony grew. Based on elemental composition, nitrogen did not appear to limit growth, but phosphorus:carbon ratios were similar to those of P-limited cultures. Giant colonies represent an extreme response to the environment, but they do not appear to have greatly different characteristics than other tropical strains.
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Haptophyta , Vietnam , Haptophyta/crecimiento & desarrollo , Haptophyta/metabolismo , Carbono/metabolismo , Carbono/análisis , Clorofila A/metabolismo , Clorofila A/análisis , Fitoplancton/crecimiento & desarrollo , Fitoplancton/metabolismo , Fitoplancton/químicaRESUMEN
Eukaryotic phytoplankton, also known as algae, form the basis of marine food webs and drive marine carbon sequestration. Algae must regulate their motility and gravitational sinking to balance access to light at the surface and nutrients in deeper layers. However, the regulation of gravitational sinking remains largely unknown, especially in motile species. Here, we quantify gravitational sinking velocities according to Stokes' law in diverse clades of unicellular marine microalgae to reveal the cell size, density, and nutrient dependency of sinking velocities. We identify a motile algal species, Tetraselmis sp., that sinks faster when starved due to a photosynthesis-driven accumulation of carbohydrates and a loss of intracellular water, both of which increase cell density. Moreover, the regulation of cell sinking velocities is connected to proliferation and can respond to multiple nutrients. Overall, our work elucidates how cell size and density respond to environmental conditions to drive the vertical migration of motile algae.
Asunto(s)
Tamaño de la Célula , Nutrientes , Nutrientes/metabolismo , Gravitación , Fitoplancton/fisiología , Fitoplancton/metabolismo , Fotosíntesis , Microalgas/metabolismoRESUMEN
Sea-ice microalgae are a key source of energy and nutrient supply to polar marine food webs, particularly during spring, prior to open-water phytoplankton blooms. The nutritional quality of microalgae as a food source depends on their biomolecular (lipid:protein:carbohydrate) composition. In this study, we used synchrotron-based Fourier transform infra-red microspectroscopy (s-FTIR) to measure the biomolecular content of a dominant sea-ice taxa, Nitzschia frigida, from natural land-fast ice communities throughout the Arctic spring season. Repeated sampling over six weeks from an inner (relatively stable) and an outer (relatively dynamic) fjord site revealed high intra-specific variability in biomolecular content, elucidating the plasticity of N. frigida to adjust to the dynamic sea ice and water conditions. Environmental triggers indicating the end of productivity in the ice and onset of ice melt, including nitrogen limitation and increased water temperature, drove an increase in lipid and fatty acids stores, and a decline in protein and carbohydrate content. In the context of climate change and the predicted Atlantification of the Arctic, dynamic mixing and abrupt warmer water advection could truncate these important end-of-season environmental shifts, causing the algae to be released from the ice prior to adequate lipid storage, influencing carbon transfer through the polar marine system.
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Cubierta de Hielo , Estaciones del Año , Regiones Árticas , Cambio Climático , Microalgas/metabolismo , Diatomeas/metabolismo , Diatomeas/fisiología , Espectroscopía Infrarroja por Transformada de Fourier/métodos , Fitoplancton/metabolismo , Fitoplancton/fisiologíaRESUMEN
Heterotrophic microbial communities play a significant role in driving carbon fluxes in marine ecosystems. Despite their importance, these communities remain understudied in remote polar oceans, which are known for their substantial contribution to the biological drawdown of atmospheric carbon dioxide. Our research focused on understanding the environmental factors and genetic makeup of key bacterial players involved in carbon remineralization in the Weddell Sea, including its coastal polynyas. Our experiments demonstrated that the combination of labile organic matter supply and temperature increase synergistically boosted bacterial growth. This suggests that, besides low seawater temperature, carbon limitation also hinders heterotrophic bacterial activity. Through the analysis of metagenome-assembled genomes, we discovered distinct genomic adaptation strategies in Bacteroidia and Gammaproteobacteria, both of which respond to organic matter. Both natural phytoplankton blooms and experimental addition of organic matter favoured Bacteroidia, which possess a large number of gene copies and a wide range of functional membrane transporters, glycoside hydrolases, and aminopeptidases. In contrast, the genomes of organic-matter-responsive Gammaproteobacteria were characterized by high densities of transcriptional regulators and transporters. Our findings suggest that bacterioplankton in the Weddell Sea, which respond to organic matter, employ metabolic strategies similar to those of their counterparts in temperate oceans. These strategies enable efficient growth at extremely low seawater temperatures, provided that organic carbon limitation is alleviated.
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Gammaproteobacteria , Fitoplancton , Agua de Mar , Agua de Mar/microbiología , Regiones Antárticas , Gammaproteobacteria/metabolismo , Gammaproteobacteria/genética , Fitoplancton/metabolismo , Fitoplancton/genética , Carbono/metabolismo , Microbiota , Plancton/metabolismo , Plancton/genética , Plancton/crecimiento & desarrollo , Metagenoma , Ecosistema , Bacteroidetes/genética , Bacteroidetes/metabolismo , Bacteroidetes/crecimiento & desarrollo , TemperaturaRESUMEN
Our oceans are populated with a wide diversity of planktonic organisms that form complex dynamic communities at the base of marine trophic networks. Within such communities are phytoplankton, unicellular photosynthetic taxa that provide an estimated half of global primary production and support biogeochemical cycles, along with other essential ecosystem services. One of the major challenges for microbial ecologists has been to try to make sense of this complexity. While phytoplankton distributions can be well explained by abiotic factors such as temperature and nutrient availability, there is increasing evidence that their ecological roles are tightly linked to their metabolic interactions with other plankton members through complex mechanisms (e.g. competition and symbiosis). Therefore, unravelling phytoplankton metabolic interactions is the key for inferring their dependency on, or antagonism with, other taxa and better integrating them into the context of carbon and nutrient fluxes in marine trophic networks. In this review, we attempt to summarize the current knowledge brought by ecophysiology, organismal imaging, in silico predictions and co-occurrence networks using 'omics data, highlighting successful combinations of approaches that may be helpful for future investigations of phytoplankton metabolic interactions within their complex communities.This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'.
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Cadena Alimentaria , Fitoplancton , Fitoplancton/metabolismo , Fitoplancton/fisiología , EcosistemaRESUMEN
Iron is a key micronutrient essential for various essential biological processes. As a consequence, alteration in iron concentration in seawater can deeply influence marine biodiversity. In polar marine environments, where environmental conditions are characterized by low temperatures, the role of iron becomes particularly significant. While iron limitation can negatively influence primary production and nutrient cycling, excessive iron concentrations can lead to harmful algal blooms and oxygen depletion. Furthermore, the growth of certain phytoplankton species can be increased in high-iron-content environments, resulting in altered balance in the marine food web and reduced biodiversity. Although many chemical/physical methods are established for inorganic iron quantification, the determination of the bio-available iron in seawater samples is more suitably carried out using marine microorganisms as biosensors. Despite existing challenges, whole-cell biosensors offer other advantages, such as real-time detection, cost-effectiveness, and ease of manipulation, making them promising tools for monitoring environmental iron levels in polar marine ecosystems. In this review, we discuss fundamental biosensor designs and assemblies, arranging host features, transcription factors, reporter proteins, and detection methods. The progress in the genetic manipulation of iron-responsive regulatory and reporter modules is also addressed to the optimization of the biosensor performance, focusing on the improvement of sensitivity and specificity.
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Biodiversidad , Técnicas Biosensibles , Hierro , Agua de Mar , Técnicas Biosensibles/métodos , Hierro/metabolismo , Monitoreo del Ambiente/métodos , Organismos Acuáticos , Fitoplancton/metabolismo , Animales , EcosistemaRESUMEN
While it is known that increased dissolved CO2 concentrations and rising sea surface temperature (ocean warming) can act interactively on marine phytoplankton, the ultimate molecular mechanisms underlying this interaction on a long-term evolutionary scale are relatively unexplored. Here, we performed transcriptomics and quantitative metabolomics analyses, along with a physiological trait analysis, on the marine diatom Thalassiosira weissflogii adapted for approximately 3.5 years to warming and/or high CO2 conditions. We show that long-term warming has more pronounced impacts than elevated CO2 on gene expression, resulting in a greater number of differentially expressed genes (DEGs). The largest number of DEGs was observed in populations adapted to warming + high CO2, indicating a potential synergistic interaction between these factors. We further identified the metabolic pathways in which the DEGs function and the metabolites with significantly changed abundances. We found that ribosome biosynthesis-related pathways were upregulated to meet the increased material and energy demands after warming or warming in combination with high CO2. This resulted in the upregulation of energy metabolism pathways such as glycolysis, photorespiration, the tricarboxylic acid cycle, and the oxidative pentose phosphate pathway, as well as the associated metabolites. These metabolic changes help compensate for reduced photochemical efficiency and photosynthesis. Our study emphasizes that the upregulation of ribosome biosynthesis plays an essential role in facilitating the adaptation of phytoplankton to global ocean changes and elucidates the interactive effects of warming and high CO2 on the adaptation of marine phytoplankton in the context of global change.
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Dióxido de Carbono , Diatomeas , Diatomeas/metabolismo , Diatomeas/genética , Diatomeas/fisiología , Dióxido de Carbono/metabolismo , Fitoplancton/genética , Fitoplancton/fisiología , Fitoplancton/metabolismo , Adaptación Fisiológica , Transcriptoma , Calentamiento Global , Fotosíntesis , MetabolómicaRESUMEN
Phytoplankton Chl:C:N:P ratios are important from both an ecological and a biogeochemical perspective. We show that these elemental ratios can be represented by a phytoplankton physiological model of low complexity that includes major cellular macromolecular pools. In particular, our model resolves time-dependent intracellular pools of chlorophyll, proteins, nucleic acids, carbohydrates/lipids, and N and P storage. Batch culture data for two diatom and two prasinophyte species are used to constrain parameters that represent specific allocation traits and strategies. A key novelty is the simultaneous estimation of physiological parameters for two phytoplankton groups of such different sizes. The number of free parameters is reduced by assuming (i) allometric scaling for maximum uptake rates, (ii) shared half-saturation constants for synthesis of functional macromolecules, (iii) shared exudation rates of functional macromolecules across the species. The rationale behind this assumption is that across the different species, the same or similar processes, enzymes, and metabolites play a role in key physiological processes. For the turnover numbers of macromolecular synthesis and storage exudation rates, differences between diatoms and prasinophytes need to be taken into account to obtain a good fit. Our model fits suggest that the parameters related to storage dynamics dominate the differences in the C:N:P ratios between the different phytoplankton groups. Since descriptions of storage dynamics are still incomplete and imprecise, predictions of C:N:P ratios by phytoplankton models likely have a large uncertainty.
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Modelos Biológicos , Fitoplancton , Fitoplancton/metabolismo , Diatomeas/metabolismo , Nitrógeno/metabolismo , Clorofila/metabolismo , Fósforo/metabolismo , Carbono/metabolismo , Sustancias Macromoleculares/metabolismo , Factores de TiempoRESUMEN
Molecular observational tools are useful for characterizing the composition and genetic endowment of microbial communities but cannot measure fluxes, which are critical for the understanding of ecosystems. To overcome these limitations, we used a mechanistic inference approach to estimate dissolved organic carbon (DOC) production and consumption by phytoplankton operational taxonomic units and heterotrophic prokaryotic amplicon sequence variants and inferred carbon fluxes between members of this microbial community from Western English Channel time-series data. Our analyses focused on phytoplankton spring and summer blooms, as well as bacteria summer blooms. In spring blooms, phytoplankton DOC production exceeds heterotrophic prokaryotic consumption, but in bacterial summer blooms heterotrophic prokaryotes consume three times more DOC than produced by the phytoplankton. This mismatch is compensated by heterotrophic prokaryotic DOC release by death, presumably from viral lysis. In both types of summer blooms, large amounts of the DOC liberated by heterotrophic prokaryotes are reused through internal recycling, with fluxes between different heterotrophic prokaryotes being at the same level as those between phytoplankton and heterotrophic prokaryotes. In context, internal recycling accounts for approximately 75% and 30% of the estimated net primary production (0.16 vs 0.22 and 0.08 vs 0.29 µmol l-1 d-1) in bacteria and phytoplankton summer blooms, respectively, and thus represents a major component of the Western English Channel carbon cycle. We have concluded that internal recycling compensates for mismatches between phytoplankton DOC production and heterotrophic prokaryotic consumption, and we encourage future analyses on aquatic carbon cycles to investigate fluxes between heterotrophic prokaryotes, specifically internal recycling.
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Bacterias , Carbono , Procesos Heterotróficos , Fitoplancton , Estaciones del Año , Fitoplancton/metabolismo , Carbono/metabolismo , Bacterias/metabolismo , Bacterias/clasificación , Bacterias/genética , Ciclo del Carbono , Células Procariotas/metabolismo , EcosistemaRESUMEN
There is considerable inconsistency in results pertaining to the biomagnification of PAHs in aquatic systems. Zooplankton specifically play an important role controlling the fate and distribution of organic contaminants up the food chain, particularly in large plateau reservoirs. However, it remains largely unknown how secondary factors affect the magnification of organic compounds in zooplankton. The present study assessed plankton species and nutrients affecting the trophic transfer of PAHs through the micro-food chain in plateau reservoirs, Guizhou Province China. Results show soluble ∑PAHs range from 99.9 - 147.3 ng L-1, and concentrations of ∑PAHs in zooplankton range from 1003.2 - 22441.3, with a mean of 4460.7 ng g-1 dw. Trophic magnification factors (TMFs) > 1 show biomagnifications of PAHs from phytoplankton to zooplankton. The main mechanisms for trophic magnification > 1 are 1) small Copepoda, Cladocera and Rotifera are prey for larger N. schmackeri and P. tunguidus, and 2) the δ15N and TLs of zooplankton are increasing with the increasing nutrients TN, NO3- and CODMn. As a result, log PAHs concentrations in zooplankton are positively correlated with the trophic levels (TLs) of zooplankton, and log BAFs of the PAHs in zooplankton are increasing with increasing TLs and log Kow. Temperature further enhances TMFs and biomagnifications of PAHs as noted by temperature related reductions in δ15N. There are also available soluble PAHs in the water column which are assimilated with increasing phytoplankton biomass within the taxa groups, diatoms, dinoflagellates and chlorophytes. Notable TMFs of PAHs in zooplankton in Guizhou plateau reservoirs are not significantly affected by phytoplankton and zooplankton biomass dilutions. The present study demonstrates the important roles of species selection, nutrients and temperature in the environmental fate of PAHs in freshwaters.
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Cadena Alimentaria , Hidrocarburos Policíclicos Aromáticos , Contaminantes Químicos del Agua , Zooplancton , Hidrocarburos Policíclicos Aromáticos/análisis , Hidrocarburos Policíclicos Aromáticos/metabolismo , China , Animales , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/metabolismo , Zooplancton/metabolismo , Monitoreo del Ambiente , Fitoplancton/metabolismo , Nutrientes/análisis , Nutrientes/metabolismo , Plancton/metabolismoRESUMEN
Inland waters are crucial in the carbon cycle, contributing significantly to the global CO2 fluxes. Carbonate lakes may act as both sources and sinks of CO2 depending on the interactions between the amount of dissolved inorganic carbon (DIC) inputs, lake metabolisms, and geochemical processes. It is often difficult to distinguish the dominant mechanisms driving CO2 dynamics and their effects on CO2 emissions. This study was undertaken in three groundwater-fed carbonate-rich lakes in central Spain (Ruidera Lakes), severely polluted with nitrates from agricultural overfertilization. Diel and seasonal (summer and winter) changes in CO2 concentration (CCO2) DIC, and CO2 emissions-(FCO2)-, as well as physical and chemical variables, including primary production and phytoplanktonic chlorophyll-a were measured. In addition, δ13C-DIC, δ13C-CO2 in lake waters, and δ13C of the sedimentary organic matter were measured seasonally to identify the primary CO2 sources and processes. While the lakes were consistently CCO2 supersaturated and FCO2 was released to the atmosphere during both seasons, the highest CCO2 and DIC were in summer (0.36-2.26 µmol L-1). Our results support a strong phosphorus limitation for primary production in these lakes, which impinges on CO2 dynamics. External DIC inputs to the lake waters primarily drive the CCO2 and, therefore, the FCO2. The δ13C-DIC signatures below -12 confirmed the primary geogenic influence on DIC. As also suggested by the high values on the calcite saturation index, the Miller-Tans plot revealed that the CO2 source in the lakes was close to the signature provided by the fractionation of δ13C-CO2 from calcite precipitation. Therefore, the main contribution behind the CCO2 values found in these karst lakes should be attributed to the calcite precipitation process, which is temperature-dependent according to the seasonal change observed in δ13C-DIC values. Finally, co-precipitation of phosphate with calcite could partly explain the observed low phytoplankton production in these lakes and the impact on the contribution to increasing greenhouse gas emissions. However, as eutrophication increases and the soluble reactive phosphorus (SRP) content increases, the co-precipitation of phosphate is expected to be progressively inhibited. These thresholds must be assessed to understand how the CO32- ions drive lake co-precipitation dynamics. Carbonate regions extend over 15% of the Earth's surface but seem essential in the CO2 dynamics at a global scale.
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Dióxido de Carbono , Lagos , Estaciones del Año , Lagos/química , Dióxido de Carbono/análisis , Dióxido de Carbono/metabolismo , España , Monitoreo del Ambiente/métodos , Ciclo del Carbono , Fitoplancton/metabolismoRESUMEN
Phages play an essential role in controlling bacterial populations. Those infecting Pelagibacterales (SAR11), the dominant bacteria in surface oceans, have been studied in silico and by cultivation attempts. However, little is known about the quantity of phage-infected cells in the environment. Using fluorescence in situ hybridization techniques, we here show pelagiphage-infected SAR11 cells across multiple global ecosystems and present evidence for tight community control of pelagiphages on the SAR11 hosts in a case study. Up to 19% of SAR11 cells were phage-infected during a phytoplankton bloom, coinciding with a ~90% reduction in SAR11 cell abundance within 5 days. Frequently, a fraction of the infected SAR11 cells were devoid of detectable ribosomes, which appear to be a yet undescribed possible stage during pelagiphage infection. We dubbed such cells zombies and propose, among other possible explanations, a mechanism in which ribosomal RNA is used as a resource for the synthesis of new phage genomes. On a global scale, we detected phage-infected SAR11 and zombie cells in the Atlantic, Pacific, and Southern Oceans. Our findings illuminate the important impact of pelagiphages on SAR11 populations and unveil the presence of ribosome-deprived zombie cells as part of the infection cycle.
Asunto(s)
Bacteriófagos , Ribosomas , Ribosomas/metabolismo , Bacteriófagos/genética , Bacteriófagos/fisiología , Fitoplancton/virología , Fitoplancton/genética , Fitoplancton/metabolismo , Hibridación Fluorescente in Situ , Alphaproteobacteria/genética , Alphaproteobacteria/metabolismo , Ecosistema , Agua de Mar/microbiología , Agua de Mar/virología , Océanos y MaresRESUMEN
Laminarin, a ß(1,3)-glucan, serves as a storage polysaccharide in marine microalgae such as diatoms. Its abundance, water solubility and simple structure make it an appealing substrate for marine bacteria. Consequently, many marine bacteria have evolved strategies to scavenge and decompose laminarin, employing carbohydrate-binding modules (CBMs) as crucial components. In this study, we characterized two previously unassigned domains as laminarin-binding CBMs in multimodular proteins from the marine bacterium Christiangramia forsetii KT0803T, thereby introducing the new laminarin-binding CBM families CBM102 and CBM103. We identified four CBM102s in a surface glycan-binding protein (SGBP) and a single CBM103 linked to a glycoside hydrolase module from family 16 (GH16_3). Our analysis revealed that both modular proteins have an elongated shape, with GH16_3 exhibiting greater flexibility than SGBP. This flexibility may aid in the recognition and/or degradation of laminarin, while the constraints in SGBP could facilitate the docking of laminarin onto the bacterial surface. Exploration of bacterial metagenome-assembled genomes (MAGs) from phytoplankton blooms in the North Sea showed that both laminarin-binding CBM families are widespread among marine Bacteroidota. The high protein abundance of CBM102- and CBM103-containing proteins during phytoplankton blooms further emphasizes their significance in marine laminarin utilization.