Browsing by Subject "BLOOM"

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  • Leikoski, Niina; Fewer, David P.; Jokela, Jouni; Alakoski, Pirita; Wahlsten, Matti; Sivonen, Kaarina (2012)
  • Kokocinski, Mikolaj; Dziga, Dariusz; Antosiak, Adam; Soininen, Janne (2021)
    Bacterioplankton community composition has become the center of research attention inrecent years. Bacteria associated with toxic cyanobacteria blooms have attracted considerable interest.However, little is known about the environmental factors driving the bacteria community, includingthe impact of invasive cyanobacteria. Therefore, our aim has been to determine the relationships be-tween heterotrophic bacteria and phytoplankton community composition across 24 Polish lakes withdifferent contributions of cyanobacteria including the invasive speciesRaphidiopsis raciborskii.Thisanalysis revealed that cyanobacteria were present in 16 lakes, whileR. raciborskiioccurred in 14 lakes.Our results show that bacteria communities differed between lakes dominated by cyanobacteria andlakes with minor contributions of cyanobacteria but did not differ between lakes withR. raciborskiiand other lakes. Physical factors, including water and Secchi depth, were the major drivers of bacteriaand phytoplankton community composition. However, in lakes dominated by cyanobacteria, bacte-rial community composition was also influenced by biotic factors such as the amount ofR. raciborskii,chlorophyll-a and total phytoplankton biomass. Thus, our study provides novel evidence on theinfluence of environmental factors andR. raciborskiion lake bacteria communities.
  • Data Descriptor Group (2018)
    Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment.
  • Omidi, Azam; Esterhuizen-Londt, Maranda; Pflugmacher, Stephan (2019)
    Although microcystins (MCs) are the most commonly studied cyanotoxins, their significance to the producing organisms remains unclear. MCs are known as endotoxins, but they can be found in the surrounding environment due to cell lysis, designated as extracellular MCs. In the present study, the interactions between MC producing and the non-producing strains of Microcystis aeruginosa, PCC 7806 and PCC 7005, respectively, and a green alga, Desmodesmus subspicatus, were studied to better understand the probable ecological importance of MCs at the collapse phase of cyanobacterial blooms. We applied a dialysis co-cultivation system where M. aeruginosa was grown inside dialysis tubing for one month. Then, D. subspicatus was added to the culture system on the outside of the membrane. Consequently, the growth of D. subspicatus and MC contents were measured over a 14-day co-exposure period. The results showed that Microcystis negatively affected the green alga as the growth of D. subspicatus was significantly inhibited in co-cultivation with both the MC-producing and -deficient strains. However, the inhibitory effect of the MC-producing strain was greater and observed earlier compared to the MC-deficient strain. Thus, MCs might be considered as an assistant factor that, in combination with other secondary metabolites of Microcystis, reinforce the ability to outcompete co-existing species.
  • Paul, A. J.; Bach, L. T.; Schulz, K. -G.; Boxhammer, T.; Czerny, J.; Achterberg, E. P.; Hellemann, D.; Trense, Y.; Nausch, M.; Sswat, M.; Riebesell, U. (2015)
    Ocean acidification is expected to influence plankton community structure and biogeochemical element cycles. To date, the response of plankton communities to elevated CO2 has been studied primarily during nutrient-stimulated blooms. In this CO2 manipulation study, we used large-volume (similar to 55 m(3)) pelagic in situ mesocosms to enclose a natural summer, post-spring-bloom plankton assemblage in the Baltic Sea to investigate the response of organic matter pools to ocean acidification. The carbonate system in the six mesocosms was manipulated to yield average fCO(2) ranging between 365 and similar to 1230 mu atm with no adjustment of naturally available nutrient concentrations. Plankton community development and key biogeochemical element pools' were subsequently followed in this nitrogen-limited ecosystem over a period of 7 weeks. We observed higher sustained chlorophyll a and particulate matter concentrations (similar to 25% higher) and lower inorganic phosphate concentrations in the water column in the highest fCO(2) treatment (1231 mu atm) during the final 2 weeks of the study period (Phase III), when there was low net change in particulate and dissolved matter pools. Size-fractionated phytoplankton pigment analyses indicated that these differences were driven by picophytoplankton (<2 mu m) and were already established early in the experiment during an initial warm and more productive period with overall elevated chlorophyll a and particulate matter concentrations. However, the influence of picophyto-plankton on bulk organic matter pools was masked by high biomass of larger plankton until Phase III, when the contribution of the small size fraction (<2 mu m) increased to up to 90% of chlorophyll a. In this phase, a CO2-driven increase in water column particulate carbon did not lead to enhanced sinking material flux but was instead reflected in increased dissolved organic carbon concentrations. Hence ocean acidification may induce changes in organic matter partitioning in the upper water column during the low-nitrogen summer period in the Baltic Sea.
  • 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.
  • Popin, Rafael Vicentini; Delbaje, Endrews; de Abreu, Vinicius Augusto Carvalho; Rigonato, Janaina; Dorr, Felipe Augusto; Pinto, Ernani; Sivonen, Kaarina; Fiore, Marli Fatima (2020)
    The bloom-forming cyanobacterium Nodularia spumigena CENA596 encodes the biosynthetic gene clusters (BGCs) of the known natural products nodularins, spumigins, anabaenopeptins/namalides, aeruginosins, mycosporin-like amino acids, and scytonemin, along with the terpenoid geosmin. Targeted metabolomics confirmed the production of these metabolic compounds, except for the alkaloid scytonemin. Genome mining of N. spumigena CENA596 and its three closely related Nodularia strains-two planktonic strains from the Baltic Sea and one benthic strain from Japanese marine sediment-revealed that the number of BGCs in planktonic strains was higher than in benthic one. Geosmin-a volatile compound with unpleasant taste and odor-was unique to the Brazilian strain CENA596. Automatic annotation of the genomes using subsystems technology revealed a related number of coding sequences and functional roles. Orthologs from the Nodularia genomes are involved in the primary and secondary metabolisms. Phylogenomic analysis of N. spumigena CENA596 based on 120 conserved protein sequences positioned this strain close to the Baltic Nodularia. Phylogeny of the 16S rRNA genes separated the Brazilian CENA596 strain from those of the Baltic Sea, despite their high sequence identities (99% identity, 100% coverage). The comparative analysis among planktic Nodularia strains showed that their genomes were considerably similar despite their geographically distant origin.
  • Enberg, Sara; Majaneva, Markus; Autio, Riitta; Blomster, Jaanika; Rintala, Janne-Markus (2018)
    The phytoplankton biomass in the Baltic Sea is low during the cold-water season (October to May) compared to the warm-water season(June to September). However, the sea ice is a habitat for diverse assemblages in polar and subpolar areas. These areas, including the Baltic Sea, are subject to changing environmental conditions due to global warming, and temporal and spatial studies are required to understand changes in the processes the organisms are involved in. We delineated microalgal succession in the northern Baltic Sea during the cold-water season using a weekly collected data set. Microscopy results together with molecular methods showed that 5 microbial groups could be distinguished: the sea-ice microalgal assemblage and 4 phytoplankton assemblages(fall, winter, under-ice water and spring). Based on cell enumeration, the microalgal biomass in the water column remained low until the end of the ice-covered season and was dominated by small flagellates and dinoflagellates. The young-ice assemblage in January resembled the water-column assemblage, but indicated a partly selective species-concentrating mechanism during ice formation due to lower species richness in ice than in the water column. Biomass of microalgae increased in the ice and water column during the March to May period, and the assemblage changed from flagellate-dominated to diatom-and dinoflagellate-dominated. The result that the spring phytoplankton, based on species and biomass, formed a separate as semblage indicates that sea-ice algae did not contribute to the spring bloom phytoplankton assemblage.
  • Osterholm, Julia; Popin, Rafael V.; Fewer, David P.; Sivonen, Kaarina (2020)
    Cyanobacteria produce an array of toxins that pose serious health risks to humans and animals. The closely related diazotrophic genera, Anabaena, Dolichospermum and Aphanizomenon, frequently form poisonous blooms in lakes and brackish waters around the world. These genera form a complex now termed the Anabaena, Dolichospermum and Aphanizomenon (ADA) clade and produce a greater array of toxins than any other cyanobacteria group. However, taxonomic confusion masks the distribution of toxin biosynthetic pathways in cyanobacteria. Here we obtained 11 new draft genomes to improve the understanding of toxin production in these genera. Comparison of secondary metabolite pathways in all available 31 genomes for these three genera suggests that the ability to produce microcystin, anatoxin-a, and saxitoxin is associated with specific subgroups. Each toxin gene cluster was concentrated or even limited to a certain subgroup within the ADA clade. Our results indicate that members of the ADA clade encode a variety of secondary metabolites following the phylogenetic clustering of constituent species. The newly sequenced members of the ADA clade show that phylogenetic separation of planktonic Dolichospermum and benthic Anabaena is not complete. This underscores the importance of taxonomic revision of Anabaena, Dolichospermum and Aphanizomenon genera to reflect current phylogenomic understanding.
  • Rusak, J. A.; Tanentzap, A. J.; Klug, J. L.; Rose, K. C.; Hendricks, S. P.; Jennings, E.; Laas, A.; Pierson, D.; Ryder, E.; Smyth, R. L.; White, D. S.; Winslow, L. A.; Adrian, R.; Arvola, L.; de Eyto, E.; Feuchtmayr, H.; Honti, M.; Istvanovics, V.; Jones, I. D.; McBride, C. G.; Schmidt, S. R.; Seekell, D.; Staehr, P. A.; Zhu, G. (2018)
    Phytoplankton biomass and production regulates key aspects of freshwater ecosystems yet its variability and subsequent predictability is poorly understood. We estimated within-lake variation in biomass using high-frequency chlorophyll fluorescence data from 18 globally distributed lakes. We tested how variation in fluorescence at monthly, daily, and hourly scales was related to high-frequency variability of wind, water temperature, and radiation within lakes as well as productivity and physical attributes among lakes. Within lakes, monthly variation dominated, but combined daily and hourly variation were equivalent to that expressed monthly. Among lakes, biomass variability increased with trophic status while, within-lake biomass variation increased with increasing variability in wind speed. Our results highlight the benefits of high-frequency chlorophyll monitoring and suggest that predicted changes associated with climate, as well as ongoing cultural eutrophication, are likely to substantially increase the temporal variability of algal biomass and thus the predictability of the services it provides.