Browsing by Subject "ALGAE"

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  • Elovaara, Samu; Eronen-Rasimus, Eeva; Asmala, Eero; Tamelander, Tobias; Kaartokallio, Hermanni (2021)
    Microbial consumption of phytoplankton-derived organic carbon in the pelagic food web is an important component of the global C cycle. We studied C cycling in two phytoplankton-bacteria systems (non-axenic cultures of a dinoflagellate Apocalathium malmogiense and a cryptophyte Rhodomonas marina) in two complementary experiments. In the first experiment we grew phytoplankton and bacteria in nutrient-replete conditions and followed C processing at early exponential growth phase and twice later when the community had grown denser. Cell-specific primary production and total community respiration were up to 4 and 7 times higher, respectively, in the A. malmogiense treatments. Based on the optical signals, accumulating dissolved organic C (DOC) was degraded more in the R. marina treatments, and the rate of bacterial production to primary production was higher. Thus, the flow of C from phytoplankton to bacteria was relatively higher in R. marina treatments than in A. malmogiense treatments, which was further supported by faster C-14 transfer from phytoplankton to bacterial biomass. In the second experiment we investigated consumption of the phytoplankton-derived DOC by bacteria. DOC consumption and transformation, bacterial production, and bacterial respiration were all higher in R. marina treatments. In both experiments A. malmogiense supported a bacterial community predominated by bacteria specialized in the utilization of less labile DOC (class Bacteroidia), whereas R. marina supported a community predominated by copiotrophic Alphaand Gammaproteobacteria. Our findings suggest that large dinoflagellates cycle relatively more C between phytoplankton biomass and the inorganic C pool, whereas small cryptophytes direct relatively more C to the microbial loop.
  • Barboza, Francisco R.; Kotta, Jonne; Weinberger, Florian; Jormalainen, Veijo; Kraufvelin, Patrik; Molis, Markus; Schubert, Hendrik; Pavia, Henrik; Nylund, Goran M.; Kautsky, Lena; Schagerstrom, Ellen; Rickert, Esther; Saha, Mahasweta; Fredriksen, Stein; Martin, Georg; Torn, Kaire; Ruuskanen, Ari; Wahl, Martin (2019)
    In the course of the ongoing global intensification and diversification of human pressures, the study of variation patterns of biological traits along environmental gradients can provide relevant information on the performance of species under shifting conditions. The pronounced salinity gradient, co-occurrence of multiple stressors, and accelerated rates of change make the Baltic Sea and its transition to North Sea a suitable region for this type of study. Focusing on the bladderwrack Fucus vesiculosus, one of the main foundation species on hard-bottoms of the Baltic Sea, we analyzed the phenotypic variation among populations occurring along 2,000 km of coasts subjected to salinities from 4 to >30 and a variety of other stressors. Morphological and biochemical traits, including palatability for grazers, were recorded at 20 stations along the Baltic Sea and four stations in the North Sea. We evaluated in a common modeling framework the relative contribution of multiple environmental drivers to the observed trait patterns. Salinity was the main and, in some cases, the only environmental driver of the geographic trait variation in F. vesiculosus. The decrease in salinity from North Sea to Baltic Sea stations was accompanied by a decline in thallus size, photosynthetic pigments, and energy storage compounds, and affected the interaction of the alga with herbivores and epibiota. For some traits, drivers that vary locally such as wave exposure, light availability or nutrient enrichment were also important. The strong genetic population structure in this macroalgae might play a role in the generation and maintenance of phenotypic patterns across geographic scales. In light of our results, the desalination process projected for the Baltic Sea could have detrimental impacts on F. vesiculosus in areas close to its tolerance limit, affecting ecosystem functions such as habitat formation, primary production, and food supply.
  • Tossavainen, Marika; Ilyass, Usman; Ollilainen, Velimatti; Valkonen, Kalle; Ojala, Anne; Romantschuk, Martin (2019)
    Nitrogen limitation is considered a good strategy for enhancement of algal lipid production while conversely N repletion has been shown to result in biomass rich in proteins. In this study, the influence of long-term N limitation on Euglena gracilis fatty acid (FA), protein, chlorophyll a, and carotenoid concentrations was studied in N limited cultures. Biomass composition was analyzed from three-time points from N starved late stationary phase cultures, exposed to three different initial N concentrations in the growth medium. Total lipid content increased under N limitation in ageing cultures, but the low N content and prolonged cultivation time resulted in the formation of a high proportion of saturated FAs. Furthermore, growth as well as the production of proteins, chlorophyll a and carotenoids were enhanced in higher N concentrations and metabolism of these cellular components stayed stable during the stationary growth phase. Our findings showed that a higher N availability and a shorter cultivation time is a good strategy for efficient E. gracilis biomass production, regardless of whether the produced biomass is intended for maximal recovery of polyunsaturated FAs, proteins, or photosynthetic pigments. Additionally, we showed an increase of neoxanthin, beta-carotene, and diadinoxanthin as a response to higher N availability.
  • Edelmann, Minnamari; Aalto, Sanni; Chamlagain, Bhawani; Kariluoto, Susanna; Piironen, Vieno (2019)
    This study aimed to investigate the riboflavin, niacin, folate and B12 content in microalgae powders. Riboflavin was determined with an ultra-high-performance liquid chromatographic (UHPLC) method after extraction and a two-enzyme treatment. Niacin analysis involved mild acidic hydrolysis, with niacin quantitated as the sum of nicotinic acid and nicotinamide using a UHPLC method. Both a microbiological (MBA) and a UHPLC method was used for vitamin B12 quantification as a cyanocobalamin (CNCb1) and UHPLC-mass spectrometry was used to confirm the vitamin B12 form. Total folate was determined both with MBA and as a sum of the vitamers with a UHPLC method after extraction and tri-enzyme treatment. The riboflavin and niacin content varied from 21 to 41 mu g/g and 0.13-0.28 mg/g, respectively, in Chlorella sp., Spirulina (Arthrospira sp.) and Nannochloropsis gaditana powders. Chlorella powders were, on average, richer in total folate (19.7 mu g/g) than Spirulina powders were (3.5 mu g/g). The sum of the folate vitamers determined with UHPLC matched better with the microbiological total folate content in Chlorella than in Spirulina powders. Pseudovitamin B12 was the predominant form over active vitamin B12 in Spirulina powders, whereas Chlorella sp. and N. gaditana powders solely contained active vitamin B12 up to 2.1 mu g/g.
  • Taipale, Sami; Peltomaa, Elina; Salmi, Pauliina (2020)
    Phytoplankton synthesizes essential omega-3 and omega-6 polyunsaturated fatty acids (PUFA) for consumers in the aquatic food webs. Only certain phytoplankton taxa can synthesize eicosapentaenoic (EPA; 20:5 omega 3) and docosahexaenoic acid (DHA; 22:6 omega 3), whereas all phytoplankton taxa can synthesize shorter-chain omega-3 and omega-6 PUFA. Here, we experimentally studied how the proportion, concentration (per DW and cell-specific), and production (mu g FA L-1 day(-1)) of omega-3 and omega-6 PUFA varied among six different phytoplankton main groups (16 freshwater strains) and between exponential and stationary growth phase. EPA and DHA concentrations, as dry weight, were similar among cryptophytes and diatoms. However, Cryptomonas erosa had two-27 times higher EPA and DHA content per cell than the other tested cryptophytes, diatoms, or golden algae. The growth was fastest with diatoms, green algae, and cyanobacteria, resulting in high production of medium chain omega-3 and omega-6 PUFA. Even though the dinoflagellate Peridinium cinctum grew slowly, the content of EPA and DHA per cell was high, resulting in a three- and 40-times higher production rate of EPA and DHA than in cryptophytes or diatoms. However, the production of EPA and DHA was 40 and three times higher in cryptophytes and diatoms than in golden algae (chrysophytes and synyrophytes), respectively. Our results show that phytoplankton taxon explains 56-84% and growth phase explains similar to 1% of variation in the cell-specific concentration and production of omega-3 and omega-6 PUFA, supporting understanding that certain phytoplankton taxa play major roles in the synthesis of essential fatty acids. Based on the average proportion of PUFA of dry weight during growth, we extrapolated the seasonal availability of PUFA during phytoplankton succession in a clear water lake. This extrapolation demonstrated notable seasonal and interannual variation, the availability of EPA and DHA being prominent in early and late summer, when dinoflagellates or diatoms increased.