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    Tracking Fatty acids from phytoplankton to jellyfish polyps under different stress regimes: a three trophic levels experiment (2018)
    Frontiers
    In:  Frontiers in Ecology and Evolution, 6 . Art.Nr. 118.
    Details
    Publication Date: 2021-03-09
    Description: The impacts of biochemicals driving food web processes are under investigation for just the last few decades. In addition, as jellyfish are drawing increasing attentions because of their mass developments and of their potential capacity of driving food web structures and energy flow by ‘top-down’ and ‘bottom-up’ controls. We here show that the provision with the biochemical complex thiamin (vitamin B1) to the common phytoplankton Rhodomonas baltica altered its fatty acid (FA) pattern towards 3-highly-unsaturated FAs (3-HUFA) and that this pattern was further transferred up to the zooplankton consumer, the copepod Acartia tonsa. However, polyps of the Jellyfish Aurelia aurita feeding on A. tonsa only had a low relative 3-HUFA content, especially due to a reduction in 22:63 (DHA), but elevated levels of 20:46 (ARA). The high proportion of the -6 HUFA, ARA in polyps may provide evidence for preferential conversion of ARA in polyps, eventually from DHA in a so far unknown pathway. In contrast to A. tonsa, newly hatched A. salina nauplii used as food for A. aurita polyps were almost devoid of HUFA, but contained high levels of C18 polyunsaturated FAs (C18-PUFA). Consequently, polyps feeding on them contained few HUFA, while high levels of C18-PUFA predominated. This suggests that A. aurita polyps cannot efficiently convert 3 C18-PUFA to 3-HUFA. In addition, besides a decrease in saturated FAs, especially an increase in HUFA in A. aurita polyps with decreasing temperature was observed, for which the dietary provision with HUFA seemed to be critical. Altering the FA pattern as a response of temperature reflects an adaptation to seasonal changes and may be related to their life history plasticity.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3389/fevo.2018.00118
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Unicellular eukaryotic community response to temperature and salinity variation in mesocosm experiments (2018)
    Frontiers
    In:  Frontiers in Microbiology, 9 . Art.Nr. 2444.
    Details
    Publication Date: 2021-03-09
    Description: Climate change has profound impacts on marine biodiversity and biodiversity changes in turn might affect the community sensitivity to impacts of abiotic changes. We used mesocosm experiments and Next Generation Sequencing to study the response of the natural Baltic and Mediterranean unicellular eukaryotic plankton communities (control and +6oC heat shock) to subsequent salinity changes (-5 psu, +5 psu). The impact on Operational Taxonomic Unit (OTU) richness, taxonomic and functional composition and rRNA:rDNA ratios were examined. Our results showed that heat shock leads to lower OTU richness (21% fewer OTUs in the Baltic and 14% fewer in the Mediterranean) and a shift in composition towards pico- and nanophytoplankton and heterotrophic related OTUs. Heat shock also leads to increased rRNA:rDNA ratios for pico- and micrograzers. Less than 18% of shared OTUs were found among the different salinities indicating the crucial role of salinity in shaping communities. The response of rRNA:rDNA ratios varied highly after salinity changes. In both experiments the diversity decrease brought about by heat shock influenced the sensitivity to salinity changes. The heat shock either decreased or increased the sensitivity of the remaining community, depending on whether it removed the more salinity-sensitive or the salinity-tolerant taxa.
    Type: Article , PeerReviewed
    Format: text
    Format: other
    DOI: 10.3389/fmicb.2018.02444
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Changes in Heterotrophic Picoplankton Community Structure after Induction of a Phytoplankton Bloom under Different Light Regimes (2019)
    MDPI
    In:  Diversity, 11 (10). Art.Nr. 195.
    Details
    Publication Date: 2022-01-31
    Description: Bacterial and archaeal diversity and succession were studied during a mesocosm experiment that investigated whether changing light regimes could affect the onset of phytoplankton blooms. For this, 454-pyrosequencing of the bacterial V1-V3 and archaeal V3-V9 16S rRNA regions was performed in samples collected from four mesocosms receiving different light irradiances at the beginning and the end of the experiment and during phytoplankton growth. In total, 46 bacterial operational taxonomic units (OTUs) with ≥1% relative abundance occurred (22-34 OTUs per mesocosm). OTUs were affiliated mainly with Rhodobacteraceae, Flavobacteriaceae and Alteromonadaceae. The four mesocosms shared 11 abundant OTUs. Dominance increased at the beginning of phytoplankton growth in all treatments and decreased thereafter. Maximum dominance was found in the mesocosms with high irradiances. Overall, specific bacterial OTUs had different responses in terms of relative abundance under in situ and high light intensities, and an early phytoplankton bloom resulted in different bacterial community structures both at high (family) and low (OTU) taxonomic levels. Thus, bacterial community structure and succession are affected by light regime, both directly and indirectly, which may have implications for an ecosystem's response to environmental changes.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.3390/d11100195
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Phytoplankton Blooms, Red Tides and Mucilaginous Aggregates in the Urban Thessaloniki Bay, Eastern Mediterranean (2019)
    MDPI
    In:  Diversity, 11 (8). Art.Nr. 136.
    Details
    Publication Date: 2022-01-31
    Description: We investigated the plankton community composition and abundance in the urban marine environment of Thessaloniki Bay. We collected water samples weekly from March 2017 to February 2018 at the coastal front of Thessaloniki city center and monthly samples from three other inshore sites along the urban front of the bay. During the study period, conspicuous and successive phytoplankton blooms, dominated by known mucilage-producing diatoms alternated with red tide events formed by the dinoflagellates Noctiluca scintillans and Spatulodinium pseudonoctiluca, and an extensive mucilage aggregate phenomenon, which appeared in late June 2017. At least 11 known harmful algae were identified throughout the study, with the increase in the abundance of the known harmful dinoflagellate Dinophysis cf. acuminata occurring in October and November 2017. Finally, a red tide caused by the photosynthetic ciliate Mesodinium rubrum on December 2017 was conspicuous throughout the sampling sites. The above-mentioned harmful blooms and red tides were linked to high nutrient concentrations and eutrophication. This paper provides an overview of eutrophication impacts on the response of the unicellular eukaryotic plankton organisms and their impact on water quality and ecosystem services
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3390/d11080136
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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