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Bertos-Fortis, Mireia
Publications (8 of 8) Show all publications
Berner, C., Bertos-Fortis, M., Pinhassi, J. & Legrand, C. (2018). Response of Microbial Communities to Changing Climate Conditions During Summer Cyanobacterial Blooms in the Baltic Sea. Frontiers in Microbiology, 9, Article ID 1562.
Open this publication in new window or tab >>Response of Microbial Communities to Changing Climate Conditions During Summer Cyanobacterial Blooms in the Baltic Sea
2018 (English)In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 9, article id 1562Article in journal (Refereed) Published
Abstract [en]

Frequencies and biomass of Baltic Sea cyanobacterial blooms are expected to be higher in future climate conditions, but also of longer duration as a result of increased sea surface temperature. Concurrently, climate predictions indicate a reduced salinity in the Baltic Sea. These climate-driven changes are expected to alter not solely the phytoplankton community but also the role of microbial communities for nutrient remineralization. Here, we present the response of summer plankton communities (filamentous cyanobacteria, picocyanobacteria, and heterotrophic bacteria) to the interplay of increasing temperature (from 16 to 18 degrees C and 20 degrees C) and reduced salinity (from salinity 6.9 to 5.9) in the Baltic Proper (NW Gotland Sea) using a microcosm approach. Warmer temperatures led to an earlier peak of cyanobacterial biomass, while yields were reduced. These conditions caused a decrease of nitrogen-fixers (Dolichospermum sp.) biomass, while non nitrogen-fixers (Pseudanabaena sp.) increased. Salinity reduction did not affect cyanobacterial growth nor community composition. Among heterotrophic bacteria, Actinobacteria showed preference for high temperature, while Gammaproteobacteria thrived at in situ temperature. Heterotrophic bacteria community changed drastically at lower salinity and resembled communities at high temperature. Picocyanobacteria and heterotrophic bacterial biomass had a pronounced increase associated with the decay of filamentous cyanobacteria. This suggests that shifts in community composition of heterotrophic bacteria are influenced both directly by abiotic factors (temperature and salinity) and potentially indirectly by cyanobacteria. Our findings suggest that at warmer temperature, lower yield of photosynthetic cyanobacteria combined with lower proportion of nitrogen-fixers in the community could result in lower carbon export to the marine food web with consequences for the decomposer community of heterotrophic bacteria.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2018
Keywords
microscopy, 16S rRNA, cyanobacteria, heterotrophic bacteria, biomass, summer bloom, Baltic Sea, climate change
National Category
Microbiology Ecology
Research subject
Ecology, Microbiology
Identifiers
urn:nbn:se:lnu:diva-77393 (URN)10.3389/fmicb.2018.01562 (DOI)000439753100001 ()30090087 (PubMedID)
Available from: 2018-08-29 Created: 2018-08-29 Last updated: 2018-08-29Bibliographically approved
Bertos-Fortis, M. (2016). Baltic Sea phytoplankton in a changing environment. (Doctoral dissertation). Växjö: Linnaeus University Press
Open this publication in new window or tab >>Baltic Sea phytoplankton in a changing environment
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Future climate scenarios in the Baltic Sea project increasing sea surface temperature, as well as increasing precipitation and river runoff resulting in decreased salinity. These changes can severely impact the dynamics and function of brackish water communities, specifically phytoplankton. Phytoplankton are a significant source of organic matter to other trophic levels, and some species can be toxic. Their response to future climate conditions is of great relevance for the health of humans and aquatic ecosystems. The aim of this thesis was to assess the potential for climate-induced changes, such as decreasing salinity, to affect phytoplankton dynamics, physiology and chemical profiles in the Baltic Sea.

     Phytoplankton successional patterns in the Baltic Proper consist of a spring bloom where diatoms and dinoflagellates co-occur and a summer bloom dominated by filamentous/colonial cyanobacteria. The consensus is that future warmer conditions will promote filamentous/colonial cyanobacteria blooms. This thesis shows that phytoplankton biomass in the spring bloom was lower in years with milder winters compared with cold winters. This suggests that in terms of annual carbon export to higher trophic levels, loss of biomass from the spring bloom is unlikely to be compensated by summer cyanobacteria. High frequency sampling of phytoplankton performed in this thesis revealed a strong relationship between the dynamics of pico- and filamentous cyanobacteria. Large genetic diversity was found in cyanobacterial populations with high niche differentiation among the same species. At community level, high temperature and low salinity were the main factors shaping the summer cyanobacterial composition. These conditions may promote the predominance of opportunistic filamentous cyanobacteria, e.g. Nodularia spumigena. This species produces various bioactive compounds, including non-ribosomal peptides such as the hepatotoxin nodularin. In this work, N. spumigena subpopulations evolved different physiological strategies, including chemical profiles, to cope with salinity stress. This high phenotypic plasticity ensures survival in future climate conditions. Under salinity stress, some subpopulations displayed shorter filaments as a trade-off. This indicates that the future freshening of the Baltic Sea may promote grazing on filamentous cyanobacteria and modify carbon flows in the ecosystem. In this thesis, Baltic N. spumigena chemotypes and genotypes grouped into two main clusters without influence of geographical origin. Thus, chemical profiling can be used to explore conspecific diversity in closely genetically related N. spumigena subpopulations.

     Overall, this thesis has significantly expanded the knowledge on phytoplankton community and population responses to short- and long-term environmental changes, relevant to project the impacts of future climate conditions in the Baltic Sea.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2016. p. 160
Series
Linnaeus University Dissertations ; 267/2016
Keywords
phytoplankton ecology, cyanobacteria, dynamics, environmental factors, successional patterns, interactions, life strategies, non-ribosomal peptides, diversity, nodularin, N. spumigena
National Category
Ecology
Research subject
Ecology, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-57860 (URN)978-91-88357-43-4 (ISBN)
Public defence
2016-11-25, Fullriggaren, Sjöfartshögskolan, Landgången 4, Kalmar, 09:30 (English)
Opponent
Supervisors
Funder
Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGESwedish Institute
Available from: 2016-11-10 Created: 2016-11-08 Last updated: 2016-11-30Bibliographically approved
Mazur-Marzec, H., Bertos-Fortis, M., Torunska-Sitarz, A., Fidor, A. & Legrand, C. (2016). Chemical and Genetic Diversity of Nodularia spumigena from the Baltic Sea. Marine Drugs, 14(11), Article ID 209.
Open this publication in new window or tab >>Chemical and Genetic Diversity of Nodularia spumigena from the Baltic Sea
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2016 (English)In: Marine Drugs, ISSN 1660-3397, E-ISSN 1660-3397, Vol. 14, no 11, article id 209Article in journal (Refereed) Published
Abstract [en]

Nodularia spumigena is a toxic, filamentous cyanobacterium occurring in brackish waters worldwide, yet forms extensive recurrent blooms in the Baltic Sea. N. spumigena produces several classes of non-ribosomal peptides (NRPs) that are active against several key metabolic enzymes. Previously, strains from geographically distant regions showed distinct NRP metabolic profiles. In this work, conspecific diversity in N. spumigena was studied using chemical and genetic approaches. NRP profiles were determined in 25 N. spumigena strains isolated in different years and from different locations in the Baltic Sea using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Genetic diversity was assessed by targeting the phycocyanin intergenic spacer and flanking regions (cpcBA-IGS). Overall, 14 spumigins, 5 aeruginosins, 2 pseudaeruginosins, 2 nodularins, 36 anabaenopeptins, and one new cyanopeptolin-like peptide were identified among the strains. Seven anabaenopeptins were new structures; one cyanopeptolin-like peptide was discovered in N. spumigena for the first time. Based on NRP profiles and cpcBA-IGS sequences, the strains were grouped into two main clusters without apparent influence of year and location, indicating persistent presence of these two subpopulations in the Baltic Sea. This study is a major step in using chemical profiling to explore conspecific diversity with a higher resolution than with a sole genetic approach.

Place, publisher, year, edition, pages
MDPI AG, 2016
Keywords
Nodularia spumigena, Baltic Sea, cyanobacteria, chemotaxonomy, non-ribosomal peptides, PC-IGS
National Category
Microbiology
Research subject
Ecology, Aquatic Ecology; Ecology, Microbiology
Identifiers
urn:nbn:se:lnu:diva-59813 (URN)10.3390/md14110209 (DOI)000390097800016 ()2-s2.0-84996555333 (Scopus ID)
Projects
EcoChange
Available from: 2017-01-16 Created: 2017-01-13 Last updated: 2018-06-08Bibliographically approved
Godhe, A., Sjoekvist, C., Sildever, S., Sefbom, J., Harðardóttir, S., Bertos-Fortis, M., . . . Rengefors, K. E. (2016). Physical barriers and environmental gradients cause spatial and temporal genetic differentiation of an extensive algal bloom. Journal of Biogeography, 43(6), 1130-1142
Open this publication in new window or tab >>Physical barriers and environmental gradients cause spatial and temporal genetic differentiation of an extensive algal bloom
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2016 (English)In: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 43, no 6, p. 1130-1142Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keywords
Adaptation, Environmental gradient, Gene flow, Genetic structure, Isolation by distance, Population, Seascape, Skeletonema
National Category
Ecology
Research subject
Ecology, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-49736 (URN)10.1111/jbi.12722 (DOI)000378711000006 ()2-s2.0-84957818454 (Scopus ID)
Projects
EcoChange
Available from: 2016-02-15 Created: 2016-02-12 Last updated: 2018-06-08Bibliographically approved
Bunse, C., Bertos-Fortis, M., Sassenhagen, I., Sildever, S., Sjöqvist, C., Godhe, A., . . . Legrand, C. (2016). Spatio-Temporal Interdependence of Bacteria and Phytoplankton during a Baltic Sea Spring Bloom. Frontiers in Microbiology, 7, Article ID 517.
Open this publication in new window or tab >>Spatio-Temporal Interdependence of Bacteria and Phytoplankton during a Baltic Sea Spring Bloom
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2016 (English)In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 7, article id 517Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2016
Keywords
16S rRNA, marine bacteria, bacterioplankton, phytoplankton, Skeletonema marinoi, spring bloom, Baltic Sea, spatio-temporal
National Category
Ecology Microbiology
Research subject
Ecology, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-53313 (URN)10.3389/fmicb.2016.00517 (DOI)000374468900001 ()2-s2.0-84966263551 (Scopus ID)
Projects
Ecochange
Available from: 2016-06-10 Created: 2016-06-10 Last updated: 2018-06-08Bibliographically approved
Bertos-Fortis, M., Farnelid, H., Lindh, M. V., Casini, M., Andersson, A., Pinhassi, J. & Legrand, C. (2016). Unscrambling Cyanobacteria Community Dynamics Related to Environmental Factors. Frontiers in Microbiology, 7, Article ID 625.
Open this publication in new window or tab >>Unscrambling Cyanobacteria Community Dynamics Related to Environmental Factors
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2016 (English)In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 7, article id 625Article in journal (Refereed) Published
Abstract [en]

Future climate scenarios in the Baltic Sea project an increase of cyanobacterial bloom frequency and duration, attributed to eutrophication and climate change. Some cyanobacteria can be toxic and their impact on ecosystem services is relevant for a sustainable sea. Yet, there is limited understanding of the mechanisms regulating cyanobacterial diversity and biogeography. Here we unravel successional patterns and changes in cyanobacterial community structure using a 2-year monthly time series during the productive season in a 100 km coastal-offshore transect using microscopy and high-throughput sequencing of 16S rRNA gene fragments. A total of 565 cyanobacterial OTUs were found, of which 231 where filamentous/colonial and 334 picocyanobacterial. Spatial differences in community structure between coastal and offshore waters were minor. An "epidemic population structure" (dominance of a single cluster) was found for Aphanizomenon/Dolichospermum within the filamentous/colonial cyanobacterial community. In summer, this cluster simultaneously occurred with opportunistic clusters/OTUs, e.g., Nodulana spumigena and Pseudanabaena. Picocyanobacteria, Synechococcus/Cyanobium, formed a consistent but highly diverse group. Overall, the potential drivers structuring summer cyanobacterial communities were temperature and salinity. However, the different responses to environmental factors among and within genera suggest high niche specificity for individual OTUs. The recruitment and occurrence of potentially toxic filamentous/colonial clusters was likely related to disturbance such as mixing events and short-term shifts in salinity, and not solely dependent on increasing temperature and nitrogen-limiting conditions. Nutrients did not explain further the changes in cyanobacterial community composition. Novel occurrence patterns were identified as a strong seasonal succession revealing a tight coupling between the emergence of opportunistic picocyanobacteria and the bloom of filamentous/colonial clusters. These findings highlight that if environmental conditions can partially explain the presence of opportunistic picocyanobacteria, microbial and trophic interactions with filamentous/colonial cyanobacteria should also be considered as potential shaping factors for single-celled communities. Regional climate change scenarios in the Baltic Sea predict environmental shifts leading to higher temperature and lower salinity; conditions identified here as favorable for opportunistic filamentous/colonial cyanobacteria. Altogether, the diversity and complexity of cyanobacterial communities reported here is far greater than previously known, emphasizing the importance of microbial interactions between filamentous and picocyanobacteria in the context of environmental disturbances.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2016
Keywords
cyanobacteria, community, environmental factors, climate change, temperature, salinity
National Category
Microbiology Ecology
Research subject
Ecology, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-53266 (URN)10.3389/fmicb.2016.00625 (DOI)000375401300001 ()2-s2.0-84973580285 (Scopus ID)
Projects
EcoChange
Available from: 2016-06-10 Created: 2016-06-10 Last updated: 2018-06-08Bibliographically approved
Legrand, C., Fridolfsson, E., Bertos-Fortis, M., Lindehoff, E., Larsson, P., Pinhassi, J. & Andersson, A. (2015). Interannual variability of phyto-bacterioplankton biomass and production in coastal and offshore waters of the Baltic Sea. Ambio, 44(supplement 3), S427-S438
Open this publication in new window or tab >>Interannual variability of phyto-bacterioplankton biomass and production in coastal and offshore waters of the Baltic Sea
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2015 (English)In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, no supplement 3, p. S427-S438Article in journal (Refereed) Published
Abstract [en]

The microbial part of the pelagic food web is seldom characterized in models despite its major contribution to biogeochemical cycles. In the Baltic Sea, spatial and temporal high frequency sampling over three years revealed changes in heterotrophic bacteria and phytoplankton coupling (biomass and production) related to hydrographic properties of the ecosystem. Phyto- and bacterioplankton were bottom-up driven in both coastal and offshore areas. Cold winter temperature was essential for phytoplankton to conform to the successional sequence in temperate waters. In terms of annual carbon production, the loss of the spring bloom (diatoms and dinoflagellates) after mild winters tended not to be compensated for by other taxa, not even summer cyanobacteria. These results improve our ability to project Baltic Sea ecosystem response to short- and long-term environmental changes.

Place, publisher, year, edition, pages
Springer, 2015
Keywords
Phytoplankton, Bacteria, Baltic Sea, Production, Climate change, Microbial foodwebs
National Category
Oceanography, Hydrology and Water Resources
Research subject
Natural Science, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-45554 (URN)10.1007/s13280-015-0662-8 (DOI)000362290800010 ()26022325 (PubMedID)2-s2.0-84937577225 (Scopus ID)
Projects
ECOCHANGE
Funder
Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGESwedish Research Council Formas
Available from: 2015-07-25 Created: 2015-07-25 Last updated: 2018-01-11Bibliographically approved
Israelsson, S., Bunse, C., Baltar, F., Bertos-Fortis, M., Fridolfsson, E., Legrand, C., . . . Pinhassi, J.Seasonal dynamics of Baltic Sea plankton activities: heterotrophic bacterial function under different biological and environmental conditions.
Open this publication in new window or tab >>Seasonal dynamics of Baltic Sea plankton activities: heterotrophic bacterial function under different biological and environmental conditions
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(English)Manuscript (preprint) (Other academic)
National Category
Microbiology Oceanography, Hydrology and Water Resources Environmental Sciences
Research subject
Ecology, Microbiology
Identifiers
urn:nbn:se:lnu:diva-69151 (URN)
Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2018-02-26Bibliographically approved
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