Profiles

Ellen Schagerström, researcher

Ellen Schagerström

Forskare

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Arbetar vid Institutionen för ekologi miljö och botanik
Telefon 08-16 37 78
E-post ellen.schagerstrom@su.se
Besöksadress Svante Arrhenius väg 20 A
Rum N506
Postadress Institutionen för ekologi miljö och botanik 106 91 Stockholm

Om mig

My research is focused on macroalga and their ecology, mainly within the relatively species poor ecosystem of the brackish Baltic Sea. I am currently coordinator of the international research group FunkVeg, which is part of the Baltic Bridge collaboration between Stockholm and Helsinki Universities. FunkVeg aims to determine the functional role of vegetation in the Baltic Sea, and is currently working on the distribution, origin and life-cycle of the little known free-living forms of bladderwrack. I am currently co-supervising a PhD student, Roxana Preston, who is working with the genetic part of the study.

Other questions I find interesting are those of speciation processes, such as what drives speciation, how long does it take to form a new species and what IS a species when it comes to algae. My PhD thesis “On the endemic Fucus radicans in the Baltic Sea” investigates what role Fucus radicans (narrow wrack) has in the Baltic Sea ecosystem, compared to the closely related and widely spread Fucus vesiculosus (bladder wrack). This includes looking at how different clones are distributed on both small and large scales, if Fucus radicans is better adapted to low salinity than Fucus vesiculosus and how the vegetative reproduction, characteristic for Fucus radicans, is affected by seasonality.

I currently work within several projects. For the National Marine Monitoring Program of Vegetated Bottoms, I annually take part in surveying the vegetation on shallow soft and hard bottoms of the Baltic Sea in the Gotland, Askö, Singö  and Höga Kusten areas. This program is funded by HaV.

As a researcher at the Baltic Sea Centre, I am managing a research project funded by the BalticSea2020 foundation on restoration of bladderwrack, the perennial brown Fucus species that forms the main underwater “forests” of the Baltic Sea.

You will find more about my science and seaweed related events on my blogs www.tangbloggen.com (in Swedish) or www.balticseaweed.com (in English).

I am happy to supervise BSc (kandidat) and MSc (master) projects in subjects relating to my own research field. If you are interested in doing your thesis with me as a supervisor, please contact me well in advance and we'll book a first meeting! There are several fun and fieldwork-filled ideas that awaits an eager student.

Sub surface activities

I hold the professional diver certificates A40, the international IDSA level 1, and dive supervisor (DykL) A40, and am currently responsible for diving activities at the Baltic Sea Centre field station, the Askö Laboratory. When not working in the academic sector, I occasionally serve as an instructor for professional divers at YRGO dive school in Svanesund.

Publikationer

I urval från Stockholms universitets publikationsdatabas
  • 2013. Ann-Britt Florin (et al.). BioInvasions Records 2 (4), 303-309

    The invasive, biofouling, Conrad's false mussel Mytilopsis leucophaeata was first recorded in Sweden during spring 2011 in the cooling water system of the power plant of Forsmark in the southern Bothnian Sea. The cooling water discharge area offers a favourable environment for growth, survival, and reproduction of M. leucophaeata and may provide a stepping stone for further spread. We present three different studies in the area, revealing a rapid increase in mussels in the artificially heated area, with densities of the magnitude of thousands of individuals m-2, as well as mussels living in surrounding waters, indicating an on-going expansion in the region.

  • 2014. Ellen Schagerström (et al.). Estuarine, Coastal and Shelf Science 149, 187-193

    On rocky shores, fucoids provide habitat, shelter and food for associated biota. In the northern parts of the Baltic, the Bothnian Sea, the new fucoid species Fucus radicans (Bergstrom et Kautsky) was recently described. This study compares the thallus complexity and size as well as quantified the abundance and biomass of epiphytic algae and invertebrate taxa of the two fucoid species F. radicans and Fucus vesiculosus L. from sympatric sites in the Bothnian Sea on the Swedish coast and around the Estonian island Saaremaa. We found that F. radicans was more complex than F. vesiculosus within the whole study range, but both species had a more complex thallus structure in the Bothnian Sea compared to Estonia. The complexity of host algae did not contribute to their associated flora and fauna taxon richness; instead, the size of thalli was a good proxy for associated communities. Specifically, on a biomass basis, F. vesiculosus displayed highest species richness and highest faunal abundance in the Bothnian Sea, whereas no such differences were found around Saaremaa, probably because both Focus species had similar height around Saaremaa whereas F. vesiculosus grew much taller and larger in the Bothnian Sea. There were some unique associated macroalgal and invertebrate species that were found only on either of the fucoids, indicating the importance of separating them as species in surveys and monitoring.

  • 2015. Ellen Schagerström, Lena Kautsky, Inga Kjersti Sjøtun.

    The brown macroalgae Fucus radicans is endemic to the Baltic Sea, but little is known about this newly described species. This thesis investigates the ecology and role of F. radicans within the species poor Baltic Sea ecosystem. The thallus of F. radicans had a more complex structure but was smaller than F. vesiculosus, the other important foundation species with which it grows in sympatry at several sites. The variability of the associated flora and fauna communities of these two Fucus species, however, was explained by the thallus size, not the complexity. Comparisons between the populations of F. radicans in the Bothnian Sea with those in Väinameri Sea on the Estonian coast, showed that the Estonian thalli were smaller, less complex and lacking the numerous adventitious branches which occur extensively in the Bothnian Sea populations.

    The distribution of F. radicans in Sweden is limited to the Bothnian Sea coast. The low salinity at the northern limit prevented successful fertilization, while increased salinity did not restrict F. radicans but improved its reproductive success. The southern distribution limit was instead shown to be negatively impacted by a combination of grazing and competition. The asexual reproduction through settling of detached fragments was favoured by high light levels and high temperature in laboratory conditions. Re-attachment occurred by basally formed rhizoids but settling also occurred through a calcium-rich substance, seemingly secreted by the fragment. Genetic spatial distribution of F. radicans showed a dominance of a few widespread clones both within and between sites with an intermingled rather than clustered pattern. The extensive female clone, common in most sites, is most likely old and several clonal lineages have derived from her.  Although more clearly expressed in the clonal populations, the macroscopic sexual dimorphism discovered appears to be a species specific trait in F. radicans. This thesis presents further insight in F. radicans role within the Baltic Sea ecosystem and its value as a study species for adaptation, clonality and speciation.

  • 2015. Angelica Ardehed (et al.). Ecology and Evolution 5 (19), 4233-4245

    In dioecious species with both sexual and asexual reproduction, the spatial distribution of individual clones affects the potential for sexual reproduction and local adaptation. The seaweed Fucus radicans, endemic to the Baltic Sea, has separate sexes, but new attached thalli may also form asexually. We mapped the spatial distribution of clones (multilocus genotypes, MLGs) over macrogeographic (>500km) and microgeographic (<100m) scales in the Baltic Sea to assess the relationship between clonal spatial structure, sexual recruitment, and the potential for natural selection. Sexual recruitment was predominant in some areas, while in others asexual recruitment dominated. Where clones of both sexes were locally intermingled, sexual recruitment was nevertheless low. In some highly clonal populations, the sex ratio was strongly skewed due to dominance of one or a few clones of the same sex. The two largest clones (one female and one male) were distributed over 100-550km of coast and accompanied by small and local MLGs formed by somatic mutations and differing by 1-2 mutations from the large clones. Rare sexual events, occasional long-distance migration, and somatic mutations contribute new genotypic variation potentially available to natural selection. However, dominance of a few very large (and presumably old) clones over extensive spatial and temporal scales suggested that either these have superior traits or natural selection has only been marginally involved in the structuring of genotypes.

  • 2016. Ellen Schagerström, Lena Kautsky. Botanica Marina 59 (6), 485-490

    Sexual dimorphism on a macroscopic scale is unusual within the Phaeophyceae. We report for the first time macroscopic sexual dimorphism in Fucus radicans. A set of morphological characters was measured on three dioecious Fucus species, F. radicans, Fucus serratus and Fucus vesiculosus, to determine if sexual dimorphism occurs in the endemic F. radicans in the Baltic Sea and if it also is found in the other fucoids. F. radicans was sampled from highly clonal populations of the Bothnian Sea and from populations in the Vainameri Sea where no clones have been found. In both locations, sexual dimorphism was recorded in receptacle size and weight in F. radicans. Also, the receptacle dry weight to wet weight ratio was higher in males than in females, showing that male receptacles have a lower water content than females. The dimorphism was more pronounced in the Bothnian Sea populations, where further differences between the sexes in thallus width and fertility index also were present. This has not been shown for any member of the genus Fucus before, but seems to be a species-specific character in F. radicans, as there were no differences between the sexes in either F. serratus or F. vesiculosus.

  • 2016. Angelica Ardehed (et al.). PLoS ONE 11 (8)

    Closely related taxa provide significant case studies for understanding evolution of new species but may simultaneously challenge species identification and definition. In the Baltic Sea, two dominant and perennial brown algae share a very recent ancestry. Fucus vesiculosus invaded this recently formed postglacial sea 8000 years ago and shortly thereafter Fucus radicans diverged from this lineage as an endemic species. In the Baltic Sea both species reproduce sexually but also recruit fully fertile new individuals by asexual fragmentation. Earlier studies have shown local differences in morphology and genetics between the two taxa in the northern and western Bothnian Sea, and around the island of Saaremaa in Estonia, but geographic patterns seemin conflict with a single origin of F. radicans. To investigate the relationship between northern and Estonian distributions, we analysed the genetic variation using 9 microsatellite loci in populations from eastern Bothnian Sea, Archipelago Sea and the Gulf of Finland. These populations are located in between earlier studied populations. However, instead of bridging the disparate genetic gap between N-W Bothnian Sea and Estonia, as expected from a simple isolation-by-distance model, the new populations substantially increased overall genetic diversity and showed to be strongly divergent from the two earlier analysed regions, showing signs of additional distinct populations. Contrasting earlier findings of increased asexual recruitment in low salinity in the Bothnian Sea, we found high levels of sexual reproduction in some of the Gulf of Finland populations that inhabit extremely low salinity. The new data generated in this study supports the earlier conclusion of two reproductively isolated but very closely related species. However, the new results also add considerable genetic and morphological complexity within species. This makes species separation at geographic scales more demanding and suggests a need for more comprehensive approaches to further disentangle the intriguing relationship and history of the Baltic Sea fucoids.

  • 2016. Ellen Schagerström, Lena Kautsky. European journal of phycology 51 (4), 378-386

    Many of the marine species that were introduced to the Baltic Sea during the Littorina stage (c. 8500-3000 years BP), e.g. Fucus vesiculosus and F. serratus, have adapted to the present low salinity. These marine species have gone from marine conditions into lower salinity environments. In this paper we ask why the recently discovered endemic brown alga Fucus radicans shows the opposite pattern. Fucus radicans is only present in the northern parts of the Baltic Sea, the low salinity Bothnian Sea (4-6 psu). Potentially, the fitness of F. radicans might be reduced in higher salinities if it is better adapted to brackish conditions. We hypothesize, however, that the southern distribution limit of F. radicans is set by biotic factors, e.g. competition with F. vesiculosus and higher grazing pressure by Idotea balthica and not by salinity. Our results show that the reproductive output of F. radicans is limited by low salinity (4 psu) but increases in higher salinities. However, the southern distribution limit, i.e. the northern Baltic Proper, is regulated by biotic factors, where the additive effects from shading by taller F. vesiculosus thalli and grazing on F. radicans by the isopod I. balthica limit the biomass production of F. radicans. We suggest that F. radicans still maintains marine traits due to its ability to propagate clonally and is restricted to the Bothnian Sea by interactions with F. vesiculosus and I. balthica. We also propose that increased precipitation due to climate change might affect the northern range limit and that the distribution of F. radicans could be expected to shift further south into the Baltic Proper.

Visa alla publikationer av Ellen Schagerström vid Stockholms universitet

Senast uppdaterad: 1 november 2018

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