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1.
J Phycol ; 60(5): 1305-1318, 2024 10.
Artigo em Inglês | MEDLINE | ID: mdl-39364699

RESUMO

This study investigated the changes in sea ice temperature, microalgae species distribution, shape changes, and photosynthetic activity observed in the first-year ice that forms in winter in Saroma-ko Lagoon, Hokkaido, Japan. Temperatures at the bottom of the ice remained constant at -1.7°C, near the freezing point, while they varied between -6 and -1°C with diel fluctuations at the surface layer. Carefully collected algal samples showed high photosynthetic quantum yield and acclimation to the light intensities of individual ice layers; this indicates that the algal photosynthetic activity responds to dynamic changes in the ice environment, such as variations in temperature, salinity, and brine space. The algal communities consisted of more than 95% diatoms. Smaller algal cells were distributed in the upper layer of the sea ice compared to the lower layers. Chaetoceros sp., the dominant small-cell species, was evenly distributed throughout the layers. In contrast, Detonula confervacea, the dominant large-cell species, was unevenly distributed in the lower layer, with smaller colony size and cell volume in the upper layer. The shape differences observed in this species were thought to be a response to the changing environment within the first-year sea ice.


Assuntos
Camada de Gelo , Microalgas , Japão , Microalgas/fisiologia , Fotossíntese , Diatomáceas/fisiologia , Salinidade
2.
Harmful Algae ; 138: 102708, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39244226

RESUMO

Domoic acid (DA) is a dangerous phycotoxin produced by several strains of diatoms of the genus Pseudo-nitzschia, and responsible for Amnesic Shellfish Poisoning (ASP) in humans. The increasingly intense ASP-outbreaks along the English Channel over the last three decades have forced persistent harvest closures of economically important and highly contaminated bivalve stocks exhibiting slow DA-depuration rates, like the king scallop Pecten maximus. Under this scenario, other pectinid species, such as the queen scallop Aequipecten opercularis have been empirically proposed as alternative resources to redress the high economic losses due to the banning of the exploitation of P. maximus. Nevertheless, the kinetics of DA depuration in A. opercularis have not been assessed so far, and its direct extraction after ASP-episodes could represent a serious threat to public health. Hence, the main objective of this work was to estimate the DA-depuration rate in the digestive gland (DG) of naturally contaminated scallops A. opercularis after a toxic Pseudo-nitzschia australis bloom subjected to experimental depuration in the laboratory for 30 days. This study also intended to go further in the knowledge about the anatomical distribution of DA in scallop tissues, and corroborate the implications of autophagy in DA-sequestration in the DG of this species as recently hypothesized. In the DG, the DA-depuration rate (0.018 day-1) suggested that even with toxin burdens as low as 40 mg⋅kg-1 in the DG, queen scallops may remain contaminated for about 70 days, thus longer under intensely contamination scenarios. The subcellular analyses corroborated DA-sequestration mainly through late-autophagy within residual bodies in the DG, without differences in the frequencies of anti-DA labeled residual bodies across the entire depuration process. These results revealed that A. opercularis cannot be considered a fast DA-depurator, and represent a baseline knowledge for decision-making about harvesting natural beds of queen scallops after toxic Pseudo-nitzschia blooms. The findings of this work also represent a cornerstone for further research to accelerate DA-depuration in this species.


Assuntos
Ácido Caínico , Pectinidae , Ácido Caínico/análogos & derivados , Ácido Caínico/metabolismo , Pectinidae/fisiologia , Animais , Toxinas Marinhas/análise , Toxinas Marinhas/metabolismo , Diatomáceas/fisiologia , Diatomáceas/metabolismo , Intoxicação por Frutos do Mar , Proliferação Nociva de Algas
3.
Harmful Algae ; 138: 102702, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39244237

RESUMO

Phytoplankton populations in the natural environment interact with each other. Despite rising global concern with Pseudo-nitzschia blooms, which can produce the potent neurotoxin domoic acid, we still do not fully understand how other phytoplankton genera respond to the presence of Pseudo-nitzschia. Here, we used a 4-year high-resolution imaging dataset for 9 commonly found phytoplankton genera in Narragansett Bay, alongside environmental data, to identify potential interactions between phytoplankton genera and their response to elevated Pseudo-nitzschia abundance. Our results indicate that Pseudo-nitzschia tends to bloom either concurrently with or right after other phytoplankton genera. Such bloom periods coincide with higher water temperatures and lower salinity. Pseudo-nitzschia image abundance tends to increase the most from March-May and peaks during May-Jun, whereas the image-derived biovolume and width of Pseudo-nitzschia chains increase the most during Jan-Feb. For most phytoplankton genera, their relationship with Pseudo-nitzschia abundance is noticeably different from their relationship with Pseudo-nitzschia image features. Despite the complexity in the phytoplankton community, our analysis suggests several ecological indicators that may be used to determine the risk of harmful algal blooms.


Assuntos
Diatomáceas , Proliferação Nociva de Algas , Fitoplâncton , Fitoplâncton/fisiologia , Diatomáceas/fisiologia , Baías
4.
Theranostics ; 14(13): 5235-5261, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39267781

RESUMO

As novel biomedical materials, microalgae have garnered significant interest because of their ability to generate photosynthetic oxygen, their antioxidant activity, and their favorable biocompatibility. Many studies have concentrated on the hypoxia-alleviating effects of microalgae within tumor microenvironments. However, recent findings indicate that microalgae can significantly increase the regeneration of various tissues and organs. To augment microalgae's therapeutic efficacy and mitigate the limitations imposed by immune clearance, it is essential to process microalgae through various processing strategies. This review examines common microalgal species in biomedical applications, such as Chlorella, Chlamydomonas reinhardtii, diatoms, and Spirulina. This review outlines diverse processing methods, including microalgae extracts, microalgae‒nanodrug composite delivery systems, surface modifications, and living microalgae‒loaded hydrogels. It also discusses the latest developments in tissue repair using processed microalgae for skin, gastrointestinal, bone, cardiovascular, lung, nerve, and oral tissues. Furthermore, future directions are presented, and research gaps for processed microalgae are identified. Collectively, these insights may inform the innovation of processed microalgae for various uses and offer guidance for ongoing research in tissue repair.


Assuntos
Microalgas , Humanos , Animais , Engenharia Tecidual/métodos , Hidrogéis/química , Regeneração/fisiologia , Chlamydomonas reinhardtii/fisiologia , Materiais Biocompatíveis , Chlorella , Diatomáceas/fisiologia , Spirulina
5.
Commun Biol ; 7(1): 1187, 2024 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-39313522

RESUMO

Raphid diatoms are one of the few eukaryotes capable of gliding motility, which is remarkably fast and allows for quasi-instantaneous directional reversals. Besides other mechanistic models, it has been suggested that an actomyosin system provides the force for diatom gliding. However, in vivo data on the dynamics of actin and myosin in diatoms are lacking. In this study, we demonstrate that the raphe-associated actin bundles required for diatom movement do not exhibit a directional turnover of subunits and thus their dynamics do not contribute directly to force generation. By phylogenomic analysis, we identified four raphid diatom-specific myosins in Craspedostauros australis (CaMyo51A-D) and investigated their in vivo localization and dynamics through GFP-tagging. Only CaMyo51B-D but not CaMyo51A exhibited coordinated movement during gliding, consistent with a role in force generation. The characterization of raphid diatom-specific myosins lays the foundation for unraveling the molecular mechanisms that underlie the gliding motility of diatoms.


Assuntos
Diatomáceas , Miosinas , Diatomáceas/metabolismo , Diatomáceas/genética , Diatomáceas/fisiologia , Miosinas/metabolismo , Miosinas/genética , Filogenia , Movimento , Actinas/metabolismo , Actinas/genética
6.
Mar Pollut Bull ; 208: 116956, 2024 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-39303550

RESUMO

This study investigated differences in total biomass (ash-free dry weight) of the periphyton and autotrophic biomass (chlorophyll-a content) of benthic diatoms in the absence or presence (No Grazer vs With Grazer) of two invertebrate grazers (Stichopus cf. horrens and Trochus maculatus) under simulated ambient (PRESENT), independent ocean acidification (OA) and warming (OW), and their combination (FUTURE) over an eight-day period. In the absence of a grazer, there were no significant differences in the average of the total and autotrophic biomass among treatments for both experiments. Stichopus significantly reduced the total and autotrophic biomass after 1 day, except under OW. Trochus significantly reduced the total biomass in the OA and OW treatments after 5 days, and the autotrophic biomass in the OA treatment after 1 and 5 days of grazing. In treatments where total and autotrophic biomass were not reduced, nutrients from the fecal matter and metabolic wastes of grazers seemingly stimulated the regeneration of microalgal biomass. The amount of fecal matter produced also affected the rate of microalgal renewal. In addition, due to the unexpected difference in seawater nutrient concentration during the two experiments, comparison of primary production under PRESENT was done to tease out nutrient effects. In PRESENT, autotrophic biomass was higher in Experiment 1 than Experiment 2, which was likely influenced by differences in nutrient concentrations. Results of this study elucidate underlying mechanisms in microalgal interactions with biotic and abiotic factors in tropical systems under changing ocean conditions.


Assuntos
Biomassa , Diatomáceas , Água do Mar , Diatomáceas/fisiologia , Água do Mar/química , Animais , Concentração de Íons de Hidrogênio , Nutrientes/análise , Herbivoria , Clorofila A
7.
Sci Total Environ ; 951: 175676, 2024 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-39179048

RESUMO

Intertidal microphytobenthos (MPB) are a major contributor to primary production in estuarine ecosystems. While their biomass is highly variable at multiple spatial and temporal scales, the underlying drivers are as yet little understood. Both in situ sampling and remote-sensing techniques often lack the temporal resolution or coverage to simultaneously capture short-term (intratidal to daily) and longer-term (weekly to annual) biomass changes. Our field setup with in-situ NDVI sensors allowed us to study MPB surface biomass variability at high temporal resolution (10 mins) for up to two years in a freshwater euglenoid dominated mudflat, and a brackish and a marine diatom dominated mudflat. MPB biomass showed marked periodicities at multiple temporal scales: seasonal, spring-neap and intratidal. The diatom-dominated MPB community showed a seasonal biomass peak in winter, while the euglenoid-dominated community showed biomass peaks during spring and summer, probably caused by underlying divergent responses to mainly irradiance, temperature and wind-induced resuspension, and macrobenthos grazing. Spring-neap periodicity likely resulted from differential migratory responses of the MPB communities to variation in timing and duration of daylight exposure. In the freshwater community, upward migration only occurred when exposure duration was sufficiently long (≥4 h). In the diatom-dominated community, morning daylight exposure resulted in highest NDVI values. This study highlights the differences in MPB biomass dynamics between MPB communities within estuarine ecosystems, and underscores the great potential of high-resolution temporal NDVI monitoring for more accurate estimates of MPB biomass and primary production.


Assuntos
Biofilmes , Biomassa , Diatomáceas , Monitoramento Ambiental , Estações do Ano , Diatomáceas/fisiologia , Monitoramento Ambiental/métodos , Ecossistema , Euglênidos
8.
Mar Pollut Bull ; 207: 116864, 2024 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-39180965

RESUMO

This study analyzed the response of marine phytoplankton to environmental changes induced by mesoscale warm eddies through the lens of functional groups, highlighting the complex interactions within the ecosystem. It was found that warm eddies significantly affected phytoplankton distribution, with cell abundance in the center being only 75.60 cells/L, compared to 1095.00 cells/L in the periphery. Vertical transport within warm eddies altered light conditions, affecting photophilic diatoms more, while increased temperatures favored the growth of warm-water dinoflagellates. This study also emphasized that ocean currents were significant factors, showing correlations with various functional groups and playing a key role in material transport and phytoplankton distribution. Additionally, the distinct responses of different functional groups to temperature and salinity underscored their unique adaptations to environmental changes. In periods without warm eddies, phytoplankton primarily congregated in shallower water layers.


Assuntos
Dinoflagellida , Ecossistema , Fitoplâncton , Fitoplâncton/fisiologia , Temperatura , Salinidade , Diatomáceas/fisiologia , Movimentos da Água , Água do Mar/química
9.
Sci Total Environ ; 950: 175230, 2024 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-39122028

RESUMO

The dipper (Cinclus cinclus) is a species strongly linked to the riparian ecosystem, known to feed on aquatic macroinvertebrates, which are sensitive to water pollution. For this, dippers have been proposed as useful bioindicators of water quality. While the distribution and ecology of the dipper are well known in Northern European rivers, few studies focus on this in Central Italy, lacking data for dipper conservation. Here, we aimed to (i) assess the dipper occurrence related to water quality using biotic indices based on diatom and macroinvertebrate communities, and (ii) evaluate the river ecosystem's overall state, through the River Functionality Index and land-use analysis in buffer areas. Overall, water quality alone does not explain the dipper occurrence, as the species was not found in many potentially suitable sites with good or high-water quality. Moreover, the diversity of the diatom and macroinvertebrate communities was not a sufficient constraint either. Conversely, the dipper occurrence significantly correlated with the River Functionality Index, which integrates several riparian ecosystem factors, indicating that well-preserved ecosystems with high functionality levels are important for dipper occurrence. Land use analyses in the areas surrounding the presence sites have shown, although not significantly, a fair level of naturalness, potentially favouring the riparian zone maintenance. As the dipper was considered in decline and threatened in Central Italy, further research on its auto-ecology and conservation threats is urgently needed. Finally, given the link between the species and the riparian ecosystem, a charismatic species such as the dipper could be used as an umbrella species in protection and conservation projects for the benefit of the entire riparian belt, which represents a buffer area of fundamental importance between terrestrial and aquatic ecosystems, although often resulted severely reduced and fragmented.


Assuntos
Ecossistema , Monitoramento Ambiental , Rios , Rios/química , Itália , Animais , Monitoramento Ambiental/métodos , Invertebrados/fisiologia , Diatomáceas/fisiologia , Qualidade da Água
10.
Nat Microbiol ; 9(9): 2356-2368, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39143356

RESUMO

The bloom and bust patterns of microalgae in aquatic systems contribute massively to global biogeochemical cycles. The decline of algal blooms is mainly caused by nutrient limitation resulting in cell death, the arrest of cell division and the aging of surviving cells. Nutrient intake can re-initiate proliferation, but the processes involved are poorly understood. Here we characterize how the bloom-forming diatom Coscinodiscus radiatus recovers from starvation after nutrient influx. Rejuvenation is mediated by extracellular vesicles that shuttle reactive oxygen species, oxylipins and other harmful metabolites out of the old cells, thereby re-enabling their proliferation. By administering nutrient pulses to aged cells and metabolomic monitoring of the response, we show that regulated pathways are centred around the methionine cycle in C. radiatus. Co-incubation experiments show that bacteria mediate aging processes and trigger vesicle production using chemical signalling. This work opens new perspectives on cellular aging and rejuvenation in complex microbial communities.


Assuntos
Diatomáceas , Vesículas Extracelulares , Microalgas , Espécies Reativas de Oxigênio , Vesículas Extracelulares/metabolismo , Microalgas/metabolismo , Microalgas/crescimento & desenvolvimento , Diatomáceas/metabolismo , Diatomáceas/fisiologia , Diatomáceas/crescimento & desenvolvimento , Espécies Reativas de Oxigênio/metabolismo , Bactérias/metabolismo , Bactérias/genética , Senescência Celular , Oxilipinas/metabolismo , Metionina/metabolismo , Nutrientes/metabolismo , Metabolômica
11.
Glob Chang Biol ; 30(8): e17417, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-39105285

RESUMO

Marine heatwaves (MHWs) are increasing in frequency, duration and intensity, disrupting global marine ecosystems. While most reported impacts have been in tropical areas, New Zealand experienced its strongest and longest MHW in 2022, profoundly affecting marine sponges. Sponges are vital to rocky benthic marine communities, with their abundance influencing ecosystem functioning. This study examines the impact of this MHW on the photosynthetic sponge Cymbastella lamellata in Fiordland, New Zealand. We describe the extent, physiological responses, mortality, microbial community changes and ecological impact of this MHW on C. lamellata. The Fiordland MHW reached a maximum temperature of 4.4°C above average, lasting for 259 days. Bleaching occurred in >90% of the C. lamellata Fiordland population. The population size exceeded 66 million from 5 to 25 m, making this the largest bleaching event of its kind ever recorded. We identified the photosynthetic symbiont as a diatom, and bleached sponges had reduced photosynthetic efficiency. Post-MHW surveys in 2023 found that over 50% of sponges at sampling sites had died but that the remaining sponges had mostly recovered from earlier bleaching. Using a simulated MHW experiment, we found that temperature stress was a driver of necrosis rather than bleaching, despite necrosis only rarely being observed in the field (<2% of sponges). This suggests that bleaching may not be the cause of the mortality directly. We also identified a microbial community shift in surviving sponges, which we propose represents a microbial-mediated adaptive response to MHWs. We also found that C. lamellata are key contributors of dissolved organic carbon to the water column, with their loss likely impacting ecosystem function. We demonstrate the potential for MHWs to disrupt key marine phyla in temperate regions, highlighting how susceptible temperate sponges globally might be to MHWs.


Assuntos
Microbiota , Poríferos , Poríferos/microbiologia , Poríferos/fisiologia , Animais , Nova Zelândia , Fotossíntese , Calor Extremo/efeitos adversos , Ecossistema , Simbiose , Diatomáceas/fisiologia , Diatomáceas/crescimento & desenvolvimento
12.
PLoS Biol ; 22(8): e3002733, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-39116044

RESUMO

A principal goal in ecology is to identify the determinants of species abundances in nature. Body size has emerged as a fundamental and repeatable predictor of abundance, with smaller organisms occurring in greater numbers than larger ones. A biogeographic component, known as Bergmann's rule, describes the preponderance, across taxonomic groups, of larger-bodied organisms in colder areas. Although undeniably important, the extent to which body size is the key trait underlying these patterns is unclear. We explored these questions in diatoms, unicellular algae of global importance for their roles in carbon fixation and energy flow through marine food webs. Using a phylogenomic dataset from a single lineage with worldwide distribution, we found that body size (cell volume) was strongly correlated with genome size, which varied by 50-fold across species and was driven by differences in the amount of repetitive DNA. However, directional models identified temperature and genome size, not cell size, as having the greatest influence on maximum population growth rate. A global metabarcoding dataset further identified genome size as a strong predictor of species abundance in the ocean, but only in colder regions at high and low latitudes where diatoms with large genomes dominated, a pattern consistent with Bergmann's rule. Although species abundances are shaped by myriad interacting abiotic and biotic factors, genome size alone was a remarkably strong predictor of abundance. Taken together, these results highlight the cascading cellular and ecological consequences of macroevolutionary changes in an emergent trait, genome size, one of the most fundamental and irreducible properties of an organism.


Assuntos
Diatomáceas , Tamanho do Genoma , Oceanos e Mares , Filogenia , Diatomáceas/genética , Diatomáceas/fisiologia , Tamanho Corporal , Temperatura
13.
Mar Environ Res ; 199: 106630, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38964247

RESUMO

Harmful algal blooms (HABs) of Alexandrium pacificum have affected the Marlborough Sounds in New Zealand since 2010, posing a threat to green-lipped mussel (GLM, Perna canaliculus) farming. Previous studies have shown A. pacificum has negative effects GLM embryos and larvae. To further investigate these toxic mechanisms, in vitro bioassays were conducted on GLM spermatozoa, hemocytes, and the diatom, Chaetoceros muelleri. The three cell types were exposed to several treatments of A. pacificum for 2 h and responses were measured using flow cytometry and pulse amplitude-modulated fluorometry. Significant spermatozoa mortality was recorded in treatments containing A. pacificum cells or fragments, while hemocyte and C. muelleri mortality was recorded in cell-free treatments of A. pacificum which contained paralytic shellfish toxins (PSTs). Variation in sensitivity between cell types as well as the sublethal effects observed, emphasise the diverse toxic mechanisms of A. pacificum on co-occurring species in the environment.


Assuntos
Diatomáceas , Dinoflagellida , Hemócitos , Espermatozoides , Animais , Dinoflagellida/fisiologia , Diatomáceas/fisiologia , Diatomáceas/efeitos dos fármacos , Hemócitos/efeitos dos fármacos , Masculino , Espermatozoides/efeitos dos fármacos , Espermatozoides/fisiologia , Perna (Organismo)/fisiologia , Perna (Organismo)/efeitos dos fármacos , Proliferação Nociva de Algas , Nova Zelândia , Toxinas Marinhas/toxicidade
14.
Sci Rep ; 14(1): 14984, 2024 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-38951587

RESUMO

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.


Assuntos
Camada de Gelo , Estações do Ano , Regiões Árticas , Mudança Climática , Microalgas/metabolismo , Diatomáceas/metabolismo , Diatomáceas/fisiologia , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Fitoplâncton/metabolismo , Fitoplâncton/fisiologia
15.
Biofouling ; 40(7): 377-389, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38955544

RESUMO

Biofouling on marine surfaces causes immense material and financial harm for maritime vessels and related marine industries. Previous reports have shown the effectiveness of amphiphilic coating systems based on poly(dimethylsiloxane) (PDMS) against such marine foulers. Recent studies on biofouling mechanisms have also demonstrated acidic microenvironments in biofilms and stronger adhesion at low-pH conditions. This report presents the design and utilization of amphiphilic polymer coatings with buffer functionalities as an active disruptor against four different marine foulers. Specifically, this study explores both neutral and zwitterionic buffer systems for marine coatings, offering insights into coating design. Overall, these buffer systems were found to improve foulant removal, and unexpectedly were the most effective against the diatom Navicula incerta.


Assuntos
Biofilmes , Incrustação Biológica , Diatomáceas , Dimetilpolisiloxanos , Incrustação Biológica/prevenção & controle , Diatomáceas/fisiologia , Dimetilpolisiloxanos/química , Animais , Soluções Tampão , Propriedades de Superfície , Concentração de Íons de Hidrogênio
16.
Sci Total Environ ; 947: 174345, 2024 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-38960174

RESUMO

Seaweed cultivation can inhibit the occurrence of red tides. However, how seaweed aquaculture interactions with harmful algal blooms will be affected by the increasing occurrence and intensity of marine heatwaves (MHWs) is unknown. In this study, we run both monoculture and coculture systems to investigate the effects of a simulated heatwave on the competition of the economically important macroalga Gracilariopsis lemaneiformis against the harmful bloom diatom Skeletonema costatum. Coculture with G. lemaneiformis led to a growth decrease in S. costatum. Growth and photosynthetic activity (Fv/Fm) of G. lemaneiformis was greatly reduced by the heatwave treatment, and did not recover even after one week. Growth and photosynthetic activity of S. costatum was also reduced by the heatwave in coculture, but returned to normal during the recovery period. S. costatum also responded to the stressful environment by forming aggregates. Metabolomic analysis suggests that the negative effects on S. costatum were related to an allelochemical release from G. lemaneiformis. These findings show that MHWs may enhance the competitive advantages of S. costatum against G. lemaneiformis, leading to more severe harmful algal blooms in future extreme weather scenarios.


Assuntos
Diatomáceas , Proliferação Nociva de Algas , Alga Marinha , Diatomáceas/fisiologia , Alga Marinha/fisiologia , Calor Extremo , Aquicultura , Gracilaria/fisiologia , Fotossíntese
17.
Sci Total Environ ; 948: 174902, 2024 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-39053551

RESUMO

Understanding local hydraulic conditions is imperative to coastal harmful algal bloom (HAB) monitoring. The research summarized herein describes how the locations and tidal phases selected for coastal hazard sampling can influence measurement results used to guide management decisions for HABs. Our study was conducted in Frenchman Bay, Maine, known for its complex deglaciated coastline, strong tidal influence, and shellfishing activities that are susceptible to problematic HABs such as those produced by some species (spp.) of the diatom genus Pseudo-nitzschia. In-situ measurements of current velocity, density, and turbulence collected over a semidiurnal tidal cycle and a companion numerical model simulation of the study area provide concurrent evidence of two adjacent counter-rotating sub-mesoscale eddies (2-4 km diameter) that persist in the depth-averaged residual circulation. The eddies are generated in the wake of several islands in an area with abrupt bathymetric gradients, both legacy conditions partly derived from deglaciation ∼15 kya. Increased concentrations of Pseudo-nitzschia spp. measured during the semidiurnal survey follow a trend of elevated turbulent dissipation rates near the water surface, indicating that surface sampling alone might not adequately indicate species abundance. Additional measurements of Pseudo-nitzschia spp. from two years of weekly sampling in the region show that algal cell abundance is highest where residual eddies form. These findings provide incentive to examine current practices of HAB monitoring and management by linking coastal geomorphology to hydraulic conditions influencing HAB sampling outcomes, coastal morphometric features to material accumulation hotspots, and millennial time scales to modern hydraulic conditions.


Assuntos
Diatomáceas , Monitoramento Ambiental , Estuários , Proliferação Nociva de Algas , Hidrodinâmica , Diatomáceas/fisiologia , Monitoramento Ambiental/métodos , Maine , Movimentos da Água
18.
J Phycol ; 60(5): 1105-1120, 2024 10.
Artigo em Inglês | MEDLINE | ID: mdl-39073104

RESUMO

Diatoms are among the most important primary producers in alpine and polar freshwaters. Although temperate diatoms are sensitive to freezing, polar diatoms often exhibit more resistance. This is particularly true for members of the (predominantly terrestrial) Pinnularia borealis species complex. However, it remains unclear to what extent this resistance applies to other representatives of the genus. Here, we compare the freezing-stress tolerance of 11 freshwater, benthic strains representing different species of Pinnularia (including Caloneis) from polar, alpine, and temperate habitats. As vegetative cells, strains were exposed to freezing temperatures of -4, -10, -20, -40, -80, and -196°C. Survival was assessed by light microscopy and photosynthetic measurements. We observed vegetative cells to be sensitive to low freezing temperatures; only "mild" freezing was survived by all tested strains, and most tested strains did not survive treatments ≤-10°C. However, individual strain sensitivities appeared related to their original habitats. For example, polar and alpine strains better withstood "mild" and "moderate" freezing (-4 and -10°C, respectively); although temperate strains were significantly affected by the "mild" freezing treatment, polar and alpine strains were not. The -10°C treatment was survived exclusively by polar strains, and only P. catenaborealis survived all treatments. Interestingly, this species exhibited the lowest survival in the -10°C treatment, potentially implying some metabolic activity even at freezing temperatures. Thus, despite more extensive sampling throughout the genus and finer temperature scaling compared to previous studies, the remarkable freezing-stress tolerance of the P. borealis species complex remains unique within the genus.


Assuntos
Diatomáceas , Ecossistema , Congelamento , Diatomáceas/fisiologia , Água Doce , Estresse Fisiológico
19.
Sci Total Environ ; 945: 173913, 2024 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-38880157

RESUMO

The globally distributed harmful algal blooms (HAB) species, Heterosigma akashiwo, has been found to exhibit ichthyotoxicity. Previous studies have shown that H. akashiwo achieves a competitive edge during bloom occurrences by inhibiting the growth of a coexisting diatom, Skeletonema costatum, through allelopathy. However, the specific allelopathic mechanisms underlying the allelopathic effects of H. akashiwo on S. costatum remain unknown. To bridge this gap, our study utilized a combination of quantitative real-time PCR and metabolomics to examine the allelopathic processes of H. akashiwo on S. costatum. Our results demonstrate that the growth of S. costatum is hindered when co-cultured with H. akashiwo (initial cell concentration, 2 × 104 cell/mL). Gene expression investigation showed a substantial reduction in the mRNA levels of cytochrome b6, ribulose bisphosphate carboxylase large chain, and silicon transporter in S. costatum when grown in co-culture conditions. Furthermore, metabolic pathway analysis suggested that the allelopathic effects of H. akashiwo disrupted several vital metabolic pathways in S. costatum, including a reduction in purine and pyrimidine metabolism and an increase in fatty acid biosynthesis. Our investigation has revealed the intricate and substantial involvement of allelopathy in the formation of H. akashiwo blooms, demonstrating the complexity of the allelopathic interaction between H. akashiwo and S. costatum. These insights also contribute significantly to our understanding of the dynamics within HAB species.


Assuntos
Alelopatia , Diatomáceas , Proliferação Nociva de Algas , Metabolômica , Diatomáceas/fisiologia , Expressão Gênica , Dinoflagellida/fisiologia , Dinoflagellida/genética , Estramenópilas/fisiologia
20.
mSphere ; 9(7): e0019824, 2024 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-38940599

RESUMO

Skeletonema costatum, a cosmopolitan diatom primarily inhabiting coastal ecosystems, exhibits a typically close yet variable relationship with heterotrophic bacteria. The increasing temperature of surface seawater is expected to substantially affect the viability and ecological dynamics of S. costatum, potentially altering its relationship with bacteria. However, it remains unclear to what extent the elevated temperature could change these relationships. Here, the relationship between axenic S. costatum and natural seawater bacteria underwent a dramatic shift from mutualism to antagonism as the co-culture temperature increased from 20°C to 25°C. The co-occurrence network indicated significantly increased complexity of interaction between S. costatum and bacteria community after temperature elevation, especially with Flavobacteriaceae, implying their potential role in eliminating S. costatum under higher temperatures. Additionally, a Flavobacteriaceae isolate, namely MS1 identified as Tamlana genus, was isolated from the co-culture system at 25°C. MS1 had a remarkable ability to eliminate S. costatum, with the mortality rate at 25°C steadily rising from 30.2% at 48 h to 92.4% at 120 h. However, it promoted algal growth to some extent at 20°C. These results demonstrated that increased temperature promotes MS1 shifts from mutualism to antagonism with S. costatum. According to the comparative genomics analysis, changes in the lifestyle of MS1 were attributed to the increased gliding motility and attachment of MS1 under elevated temperature, enabling it to exert an algicidal effect through direct contact with alga. This investigation provided an advanced understanding of interactions between phytoplankton and bacteria in future warming oceanic ecosystems. IMPORTANCE: Ocean warming profoundly influences the growth and metabolism of phytoplankton and bacteria, thereby significantly reshaping their interactions. Previous studies have shown that warming can change bacterial lifestyle from mutualism to antagonism with phytoplankton, but the underlying mechanism remains unclear. In this study, we found that high temperature promotes Tamlana sp. MS1 adhesion to Skeletonema costatum, leading to algal lysis through direct contact, demonstrating a transition in lifestyle from mutualism to antagonism with increasing temperature. Furthermore, the gliding motility of MS1 appears to be pivotal in mediating the transition of its lifestyle. These findings not only advance our understanding of the phytoplankton-bacteria relationship under ocean warming but also offer valuable insights for predicting the impact of warming on phytoplankton carbon sequestration.


Assuntos
Antibiose , Diatomáceas , Flavobacteriaceae , Água do Mar , Simbiose , Água do Mar/microbiologia , Flavobacteriaceae/genética , Flavobacteriaceae/fisiologia , Diatomáceas/fisiologia , Diatomáceas/genética , Bactérias/classificação , Bactérias/genética , Temperatura , Filogenia , Temperatura Alta , Técnicas de Cocultura , Microbiota
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