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PeerJ 2023Acoels in the family Convolutidae are commonly found with microalgal symbionts. Convolutids can host green algal and dinoflagellates within the family Symbiodiniaceae...
Acoels in the family Convolutidae are commonly found with microalgal symbionts. Convolutids can host green algal and dinoflagellates within the family Symbiodiniaceae and the genus . The diversity of these microalgae has not been well surveyed. In this study, we used PCR and culture techniques to demonstrate the biodiversity of and dinoflagellates in symbiosis with meiofaunal acoels. Here, 66 acoels were collected from seven localities around Okinawa, Ishigaki, and Kochi, Japan. While convolutids were heavily represented in this sampling, some acoels formed a clade outside Convolutidae and are potentially a new family of acoels harboring symbiotic microalgae. From the acoels collected, a total of 32 and 26 Symbiodiniaceae cultures were established. Molecular phylogenies were constructed from cultured material (and from total host DNA) using the 18S rRNA gene () and 28S rRNA gene (dinoflagellates). The majority of sequences grouped within the . clade but strains closely related to . , . , and . were also observed. This is the first report of species, other than . , naturally associating with acoels. For dinoflagellates, members of and were observed, but most Symbiodiniaceae sequences formed clusters within , grouping with . , or sister to . . Several new sequences from this study may represent novel species. This is the first molecular record of and from acoels. Microalgal strains from this study will provide a necessary framework for future taxonomic studies and research on symbiotic relationships between acoels and microalgae.
Topics: Microalgae; Symbiosis; Japan; Phylogeny; Biodiversity; Dinoflagellida
PubMed: 37814628
DOI: 10.7717/peerj.16078 -
Toxins Nov 2022In September and November 2016, eight marine sampling sites along the coast of the southeastern Gulf of Mexico were monitored for the presence of lipophilic and...
In September and November 2016, eight marine sampling sites along the coast of the southeastern Gulf of Mexico were monitored for the presence of lipophilic and hydrophilic toxins. Water temperature, salinity, hydrogen potential, dissolved oxygen saturation, inorganic nutrients and phytoplankton abundance were also determined. Two samples filtered through glass fiber filters were used for the extraction and analysis of paralytic shellfish toxins (PSTs) by lateral flow immunochromatography (IFL), HPLC with post-column oxidation and fluorescent detection (FLD) and UHPLC coupled to tandem mass spectrometry (UHPLC-MS/MS). Elevated nutrient contents were associated with the sites of rainwater discharge or those near anthropogenic activities. A predominance of the dinoflagellate was found with abundances of up to 10 cells L. Identification of the dinoflagellate was corroborated by light and scanning electron microscopy. Samples for toxins were positive by IFL, and the analogs NeoSTX and STX were identified and quantified by HPLC-FLD and UHPLC-MS/MS, with a total PST concentration of 6.5 pg cell. This study is the first report that confirms the presence of PSTs in in Mexican waters of the Gulf of Mexico.
Topics: Humans; Shellfish Poisoning; Marine Toxins; Tandem Mass Spectrometry; Gulf of Mexico; Dinoflagellida; Shellfish; Saxitoxin
PubMed: 36356010
DOI: 10.3390/toxins14110760 -
Nature Communications Nov 2023Efficient nutrient recycling underpins the ecological success of cnidarian-algal symbioses in oligotrophic waters. In these symbioses, nitrogen limitation restricts the...
Efficient nutrient recycling underpins the ecological success of cnidarian-algal symbioses in oligotrophic waters. In these symbioses, nitrogen limitation restricts the growth of algal endosymbionts in hospite and stimulates their release of photosynthates to the cnidarian host. However, the mechanisms controlling nitrogen availability and their role in symbiosis regulation remain poorly understood. Here, we studied the metabolic regulation of symbiotic nitrogen cycling in the sea anemone Aiptasia by experimentally altering labile carbon availability in a series of experiments. Combining C and N stable isotope labeling experiments with physiological analyses and NanoSIMS imaging, we show that the competition for environmental ammonium between the host and its algal symbionts is regulated by labile carbon availability. Light regimes optimal for algal photosynthesis increase carbon availability in the holobiont and stimulate nitrogen assimilation in the host metabolism. Consequently, algal symbiont densities are lowest under optimal environmental conditions and increase toward the lower and upper light tolerance limits of the symbiosis. This metabolic regulation promotes efficient carbon recycling in a stable symbiosis across a wide range of environmental conditions. Yet, the dependence on resource competition may favor parasitic interactions, explaining the instability of the cnidarian-algal symbiosis as environmental conditions in the Anthropocene shift towards its tolerance limits.
Topics: Animals; Carbon; Symbiosis; Sea Anemones; Nitrogen; Photosynthesis; Dinoflagellida
PubMed: 37914705
DOI: 10.1038/s41467-023-42579-7 -
Applied and Environmental Microbiology Nov 2023This study represents the first that investigates virus infection in dinoflagellate blooms. Our findings reveal highly similar viral assemblages that infected the bloom...
This study represents the first that investigates virus infection in dinoflagellate blooms. Our findings reveal highly similar viral assemblages that infected the bloom species and a co-adapted metabolic relationship between the host and the viruses in the blooms, which varied between the prolonged and the short-lived blooms of the same dinoflagellate species. These findings fill the gap in knowledge regarding the identity and behavior of viruses in a dinoflagellate bloom and shed light on what appears to be the complex mode of infection. The novel insight will be potentially valuable for fully understanding and modeling the role of viruses in regulating blooms of dinoflagellates and other algae.
Topics: Humans; Dinoflagellida; Virus Diseases; Harmful Algal Bloom
PubMed: 37874280
DOI: 10.1128/aem.01156-23 -
PloS One 2021There is little information on the impacts of climate change on resource partitioning for mixotrophic phytoplankton. Here, we investigated the hypothesis that light...
There is little information on the impacts of climate change on resource partitioning for mixotrophic phytoplankton. Here, we investigated the hypothesis that light interacts with temperature and CO2 to affect changes in growth and cellular carbon and nitrogen content of the mixotrophic dinoflagellate, Karlodinium veneficum, with increasing cellular carbon and nitrogen content under low light conditions and increased growth under high light conditions. Using a multifactorial design, the interactive effects of light, temperature and CO2 were investigated on K. veneficum at ambient temperature and CO2 levels (25°C, 375 ppm), high temperature (30°C, 375 ppm CO2), high CO2 (30°C, 750 ppm CO2), or a combination of both high temperature and CO2 (30°C, 750 ppm CO2) at low light intensities (LL: 70 μmol photons m-2 s-2) and light-saturated conditions (HL: 140 μmol photons m-2 s-2). Results revealed significant interactions between light and temperature for all parameters. Growth rates were not significantly different among LL treatments, but increased significantly with temperature or a combination of elevated temperature and CO2 under HL compared to ambient conditions. Particulate carbon and nitrogen content increased in response to temperature or a combination of elevated temperature and CO2 under LL conditions, but significantly decreased in HL cultures exposed to elevated temperature and/or CO2 compared to ambient conditions at HL. Significant increases in C:N ratios were observed only in the combined treatment under LL, suggesting a synergistic effect of temperature and CO2 on carbon assimilation, while increases in C:N under HL were driven only by an increase in CO2. Results indicate light-driven variations in growth and nutrient acquisition strategies for K. veneficum that may benefit this species under anticipated climate change conditions (elevated light, temperature and pCO2) while also affecting trophic transfer efficiency during blooms of this species.
Topics: Biomass; Carbon Dioxide; Dinoflagellida; Eutrophication; Hot Temperature; Nitrogen; Sunlight
PubMed: 34705875
DOI: 10.1371/journal.pone.0259161 -
PloS One 2019Dinoflagellates from the Symbiodiniaceae family and corals have an ecologically important endosymbiotic relationship. Scleractinian corals cannot survive for long...
Dinoflagellates from the Symbiodiniaceae family and corals have an ecologically important endosymbiotic relationship. Scleractinian corals cannot survive for long periods without their symbionts. These algae, also known as zooxanthellae, on the other hand, thrives outside the coral cells. The free-living populations of zooxanthellae are essential for the resilience of the coral to environmental stressors such as temperature anomalies and ocean acidification. Yet, little is known about how ocean acidification may affect the free-living zooxanthellae. In this study we aimed to test morphological, physiological and biochemical responses of zooxanthellae from the Symbiodinium genus isolated from the coral Mussismilia braziliensis, endemic to the Brazilian coast, to acidification led by increased atmospheric CO2. We tested whether photosynthetic yield, cell ultrastructure, cell density and lipid profile would change after up to 16 days of exposure to pH 7.5 in an atmospheric pCO2 of 1633 μatm. Photosynthetic yield and cell density were negatively affected and chloroplasts showed vesiculated thylakoids, indicating morphological damage. Moreover, Symbiodinium fatty acid profile drastically changed in acidified condition, showing lower polyunsaturated fatty acids and higher saturated fatty acids contents, when compared to the control, non-acidified condition. These results show that seawater acidification as an only stressor causes significant changes in the physiology, biochemistry and ultrastructure of free-living Symbiodinium.
Topics: Animals; Anthozoa; Atmosphere; Carbon Dioxide; Carbonates; Cell Proliferation; Dinoflagellida; Fatty Acids; Hydrogen-Ion Concentration; Photosynthesis; Seawater
PubMed: 31381568
DOI: 10.1371/journal.pone.0220130 -
Toxins May 2022Harmful algal bloom (HAB) species Alexandrium catenella and Dinophysis acuminata are associated with paralytic shellfish poisoning (PSP) and diarrhetic shellfish...
Harmful algal bloom (HAB) species Alexandrium catenella and Dinophysis acuminata are associated with paralytic shellfish poisoning (PSP) and diarrhetic shellfish poisoning (DSP) in humans, respectively. While PSP and DSP have been studied extensively, less is known about the effects of these HAB species or their associated toxins on shellfish. This study investigated A. catenella and D. acuminata toxicity in a larval oyster (Crassostrea virginica) bioassay. Larval activity and mortality were examined through 96-h laboratory exposures to live HAB cells (10−1000 cells/mL), cell lysates (1000 cells/mL equivalents), and purified toxins (10,000 cells/mL equivalents). Exposure to 1000 cells/mL live or lysed D. acuminata caused larval mortality (21.9 ± 7.0%, 10.2 ± 4.0%, respectively) while exposure to any tested cell concentration of live A. catenella, but not lysate, caused swimming arrest and/or mortality in >50% of larvae. Exposure to high concentrations of saxitoxin (STX) or okadaic acid (OA), toxins traditionally associated with PSP and DSP, respectively, had no effect on larval activity or mortality. In contrast, pectenotoxin-2 (PTX2) caused rapid larval mortality (49.6 ± 5.8% by 48 h) and completely immobilized larval oysters. The results indicate that the toxic effects of A. catenella and D. acuminata on shellfish are not linked to the primary toxins associated with PSP and DSP in humans, and that PTX2 is acutely toxic to larval oysters.
Topics: Animals; Dinoflagellida; Humans; Larva; Saxitoxin; Seafood; Shellfish; Shellfish Poisoning; Toxins, Biological
PubMed: 35622582
DOI: 10.3390/toxins14050335 -
Nature Communications Mar 2022Mixotrophic protists (unicellular eukaryotes) that engage in both phototrophy (photosynthesis) and phago-heterotrophy (engulfment of particles)-are predicted to...
Mixotrophic protists (unicellular eukaryotes) that engage in both phototrophy (photosynthesis) and phago-heterotrophy (engulfment of particles)-are predicted to contribute substantially to energy fluxes and marine biogeochemical cycles. However, their impact remains largely unquantified. Here we describe the sophisticated foraging strategy of a widespread mixotrophic dinoflagellate, involving the production of carbon-rich 'mucospheres' that attract, capture, and immobilise microbial prey facilitating their consumption. We provide a detailed characterisation of this previously undescribed behaviour and reveal that it represents an overlooked, yet quantitatively significant mechanism for oceanic carbon fluxes. Following feeding, the mucospheres laden with surplus prey are discarded and sink, contributing an estimated 0.17-1.24 mg m d of particulate organic carbon, or 0.02-0.15 Gt to the biological pump annually, which represents 0.1-0.7% of the estimated total export from the euphotic zone. These findings demonstrate how the complex foraging behaviour of a single species of mixotrophic protist can disproportionally contribute to the vertical flux of carbon in the ocean.
Topics: Carbon; Carbon Cycle; Dinoflagellida; Heterotrophic Processes; Oceans and Seas
PubMed: 35288549
DOI: 10.1038/s41467-022-28867-8 -
Toxins Apr 2021Microplastics (MP) widely distributed in aquatic environments have adverse effects on aquatic organisms. Currently, the impact of MP on toxigenic red tide microalgae is...
Microplastics (MP) widely distributed in aquatic environments have adverse effects on aquatic organisms. Currently, the impact of MP on toxigenic red tide microalgae is poorly understood. In this study, the strain of ATHK, typically producing paralytic shellfish toxins (PST), was selected as the target. Effects of 1 and 0.1 μm polystyrene MP with three concentration gradients (5 mg L, 25 mg L and 100 mg L) on the growth, chlorophyll (Chl ), photosynthetic activity (F/F) and PST production of ATHK were explored. Results showed that the high concentration (100 mg L) of 1 μm and 0.1 μm MP significantly inhibited the growth of ATHK, and the inhibition depended on the size and concentration of MP. Contents of Chl showed an increase with various degrees after MP exposure in all cases. The photosynthesis indicator F/F of ATHK was significantly inhibited in the first 11 days, then gradually returned to the level of control group at day 13, and finally was gradually inhibited in the 1 μm MP treatments, and promotion or inhibition to some degree also occurred at different periods after exposure to 0.1 μm MP. Overall, both particle sizes of MP at 5 and 25 mg L had no significant effect on cell toxin quota, and the high concentration 100 mg L significantly promoted the PST biosynthesis on the day 7, 11 and 15. No significant difference occurred in the cell toxin quota and the total toxin content in all treatments at the end of the experiment (day 21). All MP treatments did not change the toxin profiles of ATHK, nor did the relative molar percentage of main PST components. The growth of ATHK, Chl content, F/F and toxin production were not affected by MP shading. This is the first report on the effects of MP on the PST-producing microalgae, which will improve the understanding of the adverse impact of MP on the growth and toxin production of .
Topics: Chlorophyll A; Dinoflagellida; Marine Toxins; Microalgae; Microplastics; Photosynthesis; Polystyrenes; Shellfish Poisoning; Time Factors; Water Pollutants, Chemical
PubMed: 33924256
DOI: 10.3390/toxins13040293 -
Harmful Algae Nov 2023Allelopathy is a biological mechanism that can promote harmful algal blooms (HAB) via the inhibition of sympatric phytoplankton. While nutrient loading can also promote...
Allelopathy is a biological mechanism that can promote harmful algal blooms (HAB) via the inhibition of sympatric phytoplankton. While nutrient loading can also promote HABs, the ability of allelopathy to stimulate HABs via the regeneration of nutrients has yet to be explored. To examine the impacts of allelopathically liberated N on HAB species, a series of experiments were performed using multiple allelopathic HAB species including the dinoflagellates Alexandrium catenella and Margalefidinium polykrikoides, and the pelagophyte, Aureoumbra lagunensis. These HAB species were paired with the cosmopolitan dinoflagellate, Akashiwo sanguinea, that was labeled with NO or NH, allowing the release and transfer of N to be traced as a time course during allelopathic interactions. During all experiments, the allelopathic inhibition of Akashiwo was accompanied by increases in cell densities, growth rates, and the δN content of the HAB species, evidencing the transfer of N liberated from Akashiwo. The cellular transfer of N and release of dissolved N was higher when Akashiwo was grown with NO compared to NH suggesting a differential subcellular-compartmentalization of N sources. Regardless of the type of N, HAB species obtained 60 - 100% of their cellular N from lysed Akashiwo cells and there was an enrichment of the δN content of the dissolved NH pool post-lysis of Akashiwo. Collectively, the results demonstrate that beyond facilitating species succession, allelopathy can supply HABs with N and, therefore, is likely important for promoting and sustaining HABs. Given that allelopathy is known to be a dose-dependent process, allelopathy may induce a positive feedback loop, whereby competitors are lysed, N is liberated, HABs are intensified and, in turn, become more strongly allelopathic.
Topics: Harmful Algal Bloom; Allelopathy; Nitrogen; Dinoflagellida; Phytoplankton
PubMed: 37951604
DOI: 10.1016/j.hal.2023.102490