| 1. |
|
|
| 2. |
- Bunse, Carina, et al.
(author)
-
Spatio-Temporal Interdependence of Bacteria and Phytoplankton during a Baltic Sea Spring Bloom
- 2016
-
In: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X. ; 7
-
Journal article (peer-reviewed)abstract
- In temperate systems, phytoplankton spring blooms deplete inorganic nutrients and are major sources of organic matter for the microbial loop. In response to phytoplankton exudates and environmental factors, heterotrophic microbial communities are highly dynamic and change their abundance and composition both on spatial and temporal scales. Yet, most of our understanding about these processes comes from laboratory model organism studies, mesocosm experiments or single temporal transects. Spatial -temporal studies examining interactions of phytoplankton blooms and bacterioplankton community composition and function, though being highly informative, are scarce. In this study, pelagic microbial community dynamics (bacteria and phytoplankton) and environmental variables were monitored during a spring bloom across the Baltic Proper (two cruises between North Germany to Gulf of Finland). To test to what extent bacterioplankton community composition relates to the spring bloom, we used next generation amplicon sequencing of the 16S rRNA gene, phytoplankton diversity analysis based on microscopy counts and population genotyping of the dominating diatom Skeletonema rnarinoi. Several phytoplankton bloom related and environmental variables were identified to influence bacterial community composition. Members of Bacteroidetes and Alphaproteobacteria dominated the bacterial community composition but the bacterial groups showed no apparent correlation with direct bloom related variables. The less abundant bacterial phyla Actinobacteria, Planctomycetes, and Verrucomicrobia, on the other hand, were strongly associated with phytoplankton biomass, diatom:dinoflagellate ratio, and colored dissolved organic matter (cDOM). Many bacterial operational taxonomic units (OTUs) showed high niche specificities. For example, particular Bacteroidetes OTUs were associated with two distinct genetic clusters of S. marinoi. Our study revealed the complexity of interactions of bacterial taxa with inter- and intraspecific genetic variation in phytoplankton. Overall, our findings imply that biotic and abiotic factors during spring bloom influence bacterial community dynamics in a hierarchical manner.
|
|
| 3. |
- Godhe, Anna, 1967, et al.
(author)
-
Physical barriers and environmental gradients cause spatial and temporal genetic differentiation of an extensive algal bloom
- 2016
-
In: Journal of Biogeography. - : John Wiley & Sons. - 0305-0270 .- 1365-2699. ; 43:6, s. 1130-1142
-
Journal article (peer-reviewed)abstract
- Aim: To test if a phytoplankton bloom is panmictic, or whether geographical and environmental factors cause spatial and temporal genetic structure.Location: Baltic Sea.Method: During four cruises, we isolated clonal strains of the diatom Skeletonema marinoifrom 9 to 10 stations along a 1132 km transect and analysed the genetic structure using eight microsatellites. Using F-statistics and Bayesian clustering analysis we determined if samples were significantly differentiated. A seascape approach was applied to examine correlations between gene flow and oceanographic connectivity, and combined partial Mantel test and RDA based variation partitioning to investigate associations with environmental gradients.Results: The bloom was initiated during the second half of March in the southern and the northern- parts of the transect, and later propagated offshore. By mid-April the bloom declined in the south, whereas high phytoplankton biomass was recorded northward. We found two significantly differentiated populations along the transect. Genotypes were significantly isolated by distance and by the south–north salinity gradient, which illustrated that the effects of distance and environment were confounded. The gene flow among the sampled stations was significantly correlated with oceanographic connectivity. The depletion of silica during the progression of the bloom was related to a temporal population genetic shift.Main conclusions: A phytoplankton bloom may propagate as a continuous cascade and yet be genetically structured over both spatial and temporal scales. The Baltic Sea spring bloom displayed strong spatial structure driven by oceanographic connectivity and geographical distance, which was enhanced by the pronounced salinity gradient. Temporal transition of conditions important for growth may induce genetic shifts and different phenotypic strategies, which serve to maintain the bloom over longer periods.
|
|
| 4. |
- Hugerth, Luisa, 1987-, et al.
(author)
-
Seasonal dynamics and interactions among Baltic Sea prokaryoticand eukaryotic plankton assemblages
-
Other publication (other academic/artistic)abstract
- One of the main goals of microbial ecology is to identify the mechanismsthat regulate patterns in community structure at temporal scalescompatible with populations’ turnover times across complete seasonalcycles. Here, we examined high-frequency temporal dynamics of marineplankton from a sampling effort covering 2011-2013, roughly twice weekly,comprising 144 samples. Bacterial and eukaryotic communities wereprofiled by 16S and 18S high-throughput sequencing, respectively.Interestingly, we found that no combination of the measured environmentalparameters could predict a significant proportion of the variation inpopulation dynamics of bacterioplankton, and even less so for eukaryoticplankton. Large differences in physicochemical conditions and communitycomposition typical of temperate climates mean that different regimes canquickly succeed each other over the year, with the relative importance ofdifferent drivers changing equally rapidly. Nevertheless, our approachrevealed interesting recurrent co-occurrence patterns across distinctenvironmental changes. Hence, we could make abundance predictions formore than half of the most frequent OTUs based on interactions with otherOTUs. These results suggests that a complex set of biotic interactions arecontributing to temporal patterns among planktonic assemblages despiterapid changes in environmental conditions.
|
|
| 5. |
- Jerney, Jacqueline, et al.
(author)
-
Seasonal genotype dynamics of a marine dinoflagellate : Pelagic populations are homogeneous and as diverse as benthic seed banks
- 2021
-
In: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X.
-
Journal article (peer-reviewed)abstract
- Genetic diversity is the basis for evolutionary adaptation and selection under changing environmental conditions. Phytoplankton populations are genotypically diverse, can become genetically differentiated within small spatiotemporal scales and many species form resting stages. Resting stage accumulations in sediments (seed banks) are expected to serve as reservoirs for genetic information, but so far their role in maintaining phytoplankton diversity and in evolution has remained unclear. In this study we used the toxic dinoflagellate Alexandrium ostenfeldii (Dinophyceae) as a model organism to investigate if (i) the benthic seed bank is more diverse than the pelagic population and (ii) the pelagic population is seasonally differentiated. Resting stages (benthic) and plankton (pelagic) samples were collected at a coastal bloom site in the Baltic Sea, followed by cell isolation and genotyping using microsatellite markers (MS) and restriction site associated DNA sequencing (RAD). High clonal diversity (98%–100%) combined with intermediate to low gene diversity (0.58–0.03, depending on the marker) was found. Surprisingly, the benthic and pelagic fractions of the population were equally diverse, and the pelagic fraction was temporally homogeneous, despite seasonal fluctuation of environmental selection pressures. The results of this study suggest that continuous benthic–pelagic coupling, combined with frequent sexual reproduction, as indicated by persistent linkage equilibrium, prevent the dominance of single clonal lineages in a dynamic environment. Both processes harmonize the pelagic with the benthic population and thus prevent seasonal population differentiation. At the same time, frequent sexual reproduction and benthic–pelagic coupling maintain high clonal diversity in both habitats.
|
|
| 6. |
|
|
| 7. |
- Rinne, Henna, et al.
(author)
-
Morphological and genetic variation of Fucus in the eastern Gulf of Bothnia, northern Baltic Sea
- 2018
-
In: European journal of phycology. - : TAYLOR & FRANCIS LTD. - 0967-0262 .- 1469-4433. ; 53:3, s. 369-380
-
Journal article (peer-reviewed)abstract
- Fucus vesiculosus and F. radicans (Phaeophyceae) are important habitat-formers on rocky shores in the Bothnian Sea. While both species occur sympatrically along the entire western Bothnian Sea coast, F. radicans has been found only in the northern part of the eastern coast. According to previous studies, the two species can be distinguished based on morphology, F. radicans having narrower thalli and a bushier appearance. However, marine mapping in the eastern Bothnian Sea has revealed that high morphological variation in Fucus, partly caused by gradients in salinity and exposure, makes differentiation between the two species difficult. We studied morphological and genetic variation to find out whether the two Fucus species can be differentiated in the south-eastern Bothnian Sea, and if F. radicans occurs in the area. The study was carried out in six subareas including 350 km of coast, witha salinity gradient of 3.5-6.5 PSU, and varying wave exposure. We found a gradual change towards smaller and narrower thalli and a higher number of holdfasts in Fucus populations when moving northwards to lower salinities. Distinct Fucus morphs were often found within the study sites but the morphs were genetically differentiated only at one study site in the Skaftung subarea, suggesting the occurrence of both species. However, in the Vasa subarea the sample size for analysing genetic differentiation was low due to high clonality. In the Luvia subarea south of Skaftung, Fucus morphology corresponded to that of F. radicans in earlier studies but the population was genetically more similar to F. vesiculosus in the southern subareas. We conclude that by using only morphological characteristics it is not possible to differentiate between the two species in central and northern parts of the eastern Bothnian Sea. Based on genetic analyses, the southernmost known occurrence of F. radicans in the eastern Bothnian Sea is in Skaftung.
|
|
| 8. |
- Sjöqvist, Conny, et al.
(author)
-
Ecologically coherent population structure of uncultivated bacterioplankton
- 2021
-
In: The ISME Journal. - : Springer Nature. - 1751-7362 .- 1751-7370.
-
Journal article (peer-reviewed)abstract
- Bacterioplankton are main drivers of biogeochemical cycles and important components of aquatic food webs. While sequencing-based studies have revealed how bacterioplankton communities are structured in time and space, relatively little is known about intraspecies diversity patterns and their ecological relevance. Here, we use the newly developed software POGENOM (POpulation GENomics from Metagenomes) to investigate genomic diversity and differentiation in metagenome-assembled genomes from the Baltic Sea, and investigate their genomic variation using metagenome data spanning a 1700 km transect and covering seasonal variation at one station. The majority of the investigated species, representing several major bacterioplankton clades, displayed population structures correlating significantly with environmental factors such as salinity and temperature. Population differentiation was more pronounced over spatial than temporal scales. We discovered genes that have undergone adaptation to different salinity regimes, potentially responsible for the populations' existence along with the salinity range. This in turn implies the broad existence of ecotypes that may remain undetected by rRNA gene sequencing. Our findings emphasize the importance of physiological barriers, and highlight the role of adaptive divergence as a structuring mechanism of bacterioplankton species.
|
|
| 9. |
- Wampach, L., et al.
(author)
-
Birth mode is associated with earliest strain-conferred gut microbiome functions and immunostimulatory potential
- 2018
-
In: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9:1
-
Journal article (peer-reviewed)abstract
- The rate of caesarean section delivery (CSD) is increasing worldwide. It remains unclear whether disruption of mother-to-neonate transmission of microbiota through CSD occurs and whether it affects human physiology. Here we perform metagenomic analysis of earliest gut microbial community structures and functions. We identify differences in encoded functions between microbiomes of vaginally delivered (VD) and CSD neonates. Several functional pathways are over-represented in VD neonates, including lipopolysaccharide (LPS) biosynthesis. We link these enriched functions to individual-specific strains, which are transmitted from mothers to neonates in case of VD. The stimulation of primary human immune cells with LPS isolated from early stool samples of VD neonates results in higher levels of tumour necrosis factor (TNF-α) and interleukin 18 (IL-18). Accordingly, the observed levels of TNF-α and IL-18 in neonatal blood plasma are higher after VD. Taken together, our results support that CSD disrupts mother-to-neonate transmission of specific microbial strains, linked functional repertoires and immune-stimulatory potential during a critical window for neonatal immune system priming.
|
|
