Browsing by Subject "dinoflagellates"

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  • Camarena‐Gómez, María Teresa; Ruiz‐González, Clara; Piiparinen, Jonna; Lipsewers, Tobias; Sobrino, Cristina; Logares, Ramiro; Spilling, Kristian (American Society of Limnology and Oceanography, 2021)
    Limnology and Oceanography 66: 1, 255-271
    In parts of the Baltic Sea, the phytoplankton spring bloom communities, commonly dominated by diatoms, are shifting toward the co-occurrence of diatoms and dinoflagellates. Although phytoplankton are known to shape the composition and function of associated bacterioplankton communities, the potential bacterial responses to such a decrease of diatoms are unknown. Here we explored the changes in bacterial communities and heterotrophic production during the spring bloom in four consecutive spring blooms across several sub-basins of the Baltic Sea and related them to changes in environmental variables and in phytoplankton community structure. The taxonomic structure of bacterioplankton assemblages was partially explained by salinity and temperature but also linked to the phytoplankton community. Higher carbon biomass of the diatoms Achnanthes taeniata, Skeletonema marinoi, Thalassiosira levanderi, and Chaetoceros spp. was associated with more diverse bacterial communities dominated by copiotrophic bacteria (Flavobacteriia, Gammaproteobacteria, and Betaproteobacteria) and higher bacterial production. During dinoflagellate dominance, bacterial production was low and bacterial communities were dominated by Alphaproteobacteria, mainly SAR11. Our results suggest that increases in dinoflagellate abundance during the spring bloom will largely affect the structuring and functioning of the associated bacterial communities. This could decrease pelagic remineralization of organic matter and possibly affect the bacterial grazers communities.
  • Peltomaa, Elina; Hällfors, Heidi; Taipale, Sami J. (2019)
    Recent studies have clearly shown the importance of omega-3 (-3) and omega-6 (-6) polyunsaturated fatty acids (PUFAs) for human and animal health. The long-chain eicosapentaenoic acid (EPA; 20:5-3) and docosahexaenoic acid (DHA; 22:6-3) are especially recognized for their nutritional value, and ability to alleviate many diseases in humans. So far, fish oil has been the main human source of EPA and DHA, but alternative sources are needed to satisfy the growing need for them. Therefore, we compared a fatty acid profile and content of 10 diatoms and seven dinoflagellates originating from marine, brackish and freshwater habitats. These two phytoplankton groups were chosen since they are excellent producers of EPA and DHA in aquatic food webs. Multivariate analysis revealed that, whereas the phytoplankton group (46%) explained most of the differences in the fatty acid profiles, habitat (31%) together with phytoplankton group (24%) explained differences in the fatty acid contents. In both diatoms and dinoflagellates, the total fatty acid concentrations and the -3 and -6 PUFAs were markedly higher in freshwater than in brackish or marine strains. Our results show that, even though the fatty acid profiles are genetically ordered, the fatty acid contents may vary greatly by habitat and affect the -3 and -6 availability in food webs.
  • Sörenson, Eva; Bertos-Fortis, Mireia; Farnelid, Hanna; Kremp, Anke; Krüger, Karen; Lindehoff, Elin; Legrand, Catherine (Wiley & Sons, 2019)
    Environmental Microbiology Reports, 11: 425-433
    Phytoplankton and bacteria interactions have a significant role in aquatic ecosystem functioning. Associations can range from mutualistic to parasitic, shaping biogeochemical cycles and having a direct influence on phytoplankton growth. How variations in phenotype and sampling location, affect the phytoplankton microbiome is largely unknown. A high-resolution characterization of the bacterial community in cultures of the dinoflagellate Alexandrium was performed on strains isolated from different geographical locations and at varying anthropogenic impact levels. Microbiomes of Baltic Sea Alexandrium ostenfeldii isolates were dominated by Betaproteobacteria and were consistent over phenotypic and genotypic Alexandrium strain variation, resulting in identification of an A. ostenfeldii core microbiome. Comparisons with in situ bacterial communities showed that taxa found in this A. ostenfeldii core were specifically associated to dinoflagellate dynamics in the Baltic Sea. Microbiomes of Alexandrium tamarense and minutum, isolated from the Mediterranean Sea, differed from those of A. ostenfeldii in bacterial diversity and composition but displayed high consistency, and a core set of bacterial taxa was identified. This indicates that Alexandrium isolates with diverse phenotypes host predictable, species-specific, core microbiomes reflecting the abiotic conditions from which they were isolated. These findings enable in-depth studies of potential interactions occurring between Alexandrium and specific bacterial taxa.
  • Jerney, Jacqueline; Suikkanen, Sanna; Lindehoff, Elin; Kremp, Anke (2019)
    Abstract Environmental conditions regulate the germination of phytoplankton resting stages. While some factors lead to synchronous germination, others stimulate germination of only a small fraction of the resting stages. This suggests that habitat filters may act on the germination level and thus affect selection of blooming strains. Benthic ?seed banks? of the toxic dinoflagellate Alexandrium ostenfeldii from the Baltic Sea are genetically and phenotypically diverse, indicating a high potential for adaptation by selection on standing genetic variation. Here, we experimentally tested the role of climate-related salinity and temperature as selection filters during germination and subsequent establishment of A. ostenfeldii strains. A representative resting cyst population was isolated from sediment samples, and germination and reciprocal transplantation experiments were carried out, including four treatments: Average present day germination conditions and three potential future conditions: high temperature, low salinity, and high temperature in combination with low salinity. We found that the final germination success of A. ostenfeldii resting cysts was unaffected by temperature and salinity in the range tested. A high germination success of more than 80% in all treatments indicates that strains are not selected by temperature and salinity during germination, but selection becomes more important shortly after germination, in the vegetative stage of the life cycle. Moreover, strains were not adapted to germination conditions. Instead, highly plastic responses occurred after transplantation and significantly higher growth rates were observed at higher temperature. High variability of strain-specific responses has probably masked the overall effect of the treatments, highlighting the importance of testing the effect of environmental factors on many strains. It is likely that A. ostenfeldii populations can persist in the future, because suitable strains, which are able to germinate and grow well at potential future climate conditions, are part of the highly diverse cyst population. OPEN RESEARCH BADGES This article has been awarded Open Data badge. All materials and data are publicly accessible via the Open Science Framework at https://doi.org/10.5061/dryad.c8c83nr. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.
  • Elovaara, Samu; Degerlund, Maria; Franklin, Daniel J.; Kaartokallio, Hermanni; Tamelander, Tobias (Springer Link, 2020)
    Hydrobiologia 847 11 (2020)
    Cell death drives the magnitude and community composition of phytoplankton and can result in the conversion of particulate organic carbon to dissolved organic carbon (DOC), thereby affecting carbon cycling in the aquatic food web. We used a membrane integrity probe (Sytox Green) to study the seasonal variation in the percentage of viable cells in the phytoplankton population in an estuary in the northern Baltic Sea for 21 months. The associated dissolved and particulate organic matter concentrations were also studied. The viable fraction of phytoplankton cells varied from < 20% to almost 100%, with an average of 62%. Viability was highest when a single phytoplankton group (diatoms or dinoflagellates) dominated the community. Viability of sinking phytoplankton cells, including some motile species, was in general as high as in surface water. Changes in viability were not closely related to nutrient concentrations, virus-like particle abundance, seawater temperature or salinity. There was a weak but significant negative correlation between viability and DOC, although at this location, the DOC pool was mainly influenced by the inflow of riverine water. This study demonstrates that cell viability, and its relationship with carbon export, is highly variable in the complex microbial populations common within estuarine and coastal marine ecosystems.