PhD students

PhD students in the Marine Ecosystems Research Group:

Norman Gobeler

PhD Student at TZS. Funded by Walter and Andrèe de Nottbeck Foundation.

The intensity and frequency of marine heatwaves have increased globally not sparing the Baltic Sea, an environment already stressed by e.g. eutrophication and hypoxia. My research focuses on the impact of such episodic events on benthic communities and the maintenance of their respective ecosystem functioning of bioturbation and nutrient cycling. Organisms possess different strategies in adapting to changing environmental conditions – but what are the consequences of prompt, intense changes? What traits are favorable in coping with such events? Additionally, I will also assess what habitats (seagrass meadows, bladder wrack belt, mussel bed, etc.) are most susceptible to marine heatwaves.

Current research project:

  • The role of episodic events for biodiversity and ecosystem functioning in coastal waters.
Clio Hall

PhD Student at TZS. Funded by the Onni Talas Foundation.

My main research interests are in understanding the response of plankton food webs to environmental change and in the related development of sustainable marine management strategies. Current climate change predictions indicate increased levels of warming and declining salinity in the Baltic Sea, with negative implications for plankton food webs, which are an important component for ecosystem functioning and the provision of ecosystem services. It is therefore important to understand how these changes may shape the marine environment, to develop improved management strategies that ensure the conservation of marine ecosystems. So far, relatively little is known about the synergistic effect of temperature and salinity from a plankton food web perspective. My PhD aims to address this by investigating the response of trophic interactions within plankton communities (from bacteria to fish larvae) under different scenarios of warming and freshening of the Baltic Sea. 

Current research project:

  • Impact of temperature and salinity change on food web interactions in marine plankton communities. Funded by the Onni Talas Foundation.

Clio´s profile in the University of Helsinki research portal.

Mari Joensuu

PhD student. Funded by Heikki ja Hilma Honkasen säätiö, Walter and Andrée de Nottbeck Foundation, Onni Talaan säätiö.

I am studying sediment erodibility and resuspension in coastal areas of the Baltic Sea. I am specifically interested in the environmental drivers behind the spatial and temporal variability of sediment erodibility in natural environments.

Current research projects:

  • Sediment erodibility and resuspension in shallow coastal areas of the Baltic Sea. (PhD student: Funded by Heikki ja Hilma Honkasen säätiö, Walter and Andrée de Nottbeck Foundation, Onni Talaan säätiö, 2015-2018).
  • BONUS COCOA - Nutrient cocktail in coastal zones of the Baltic Sea – improving understanding of the transformation and retention of nutrients and organic matter in the coastal zone. (PhD student: funded jointly by the EU and the Academy of Finland, 2014-2017).

Mari’s profile in the University of Helsinki research portal and Mari’s profile in Google Scholar.

T. I. Kahma

PhD student at TZS. Funded by the Nottbeck foundation.

My project examines the role of increasing accumulations of drifting detritus on the organic carbon fate of key coastal habitats in the Baltic Sea. The overall aim of this project is to study the fate of macroalgae-derived organic carbon, and examine how detritus source characteristics might affect the composition of organic carbon in coastal areas influenced by large external inputs of algal detritus. An additional aim is to investigate how this role may change seasonally.

Current research projects:

  • The effects of increasing accumulations of algal detritus on the fate of organic carbon in shallow coastal habitats from the Baltic Sea.

Kahma’s profile in the University of Helsinki research portal.

Saara Mäkelin

PhD student at TZS. Funded by the University of Helsinki and the Nottbeck foundation.

I explore the role of benthic animals for carbon and nutrient cycling in the Baltic Sea. Coastal ecosystems are highly threatened by climate change and eutrophication, with harmful consequences for biodiversity and ecosystem functions. Benthic macrofaunal communities play a pivotal role in biogeochemical cycling and can increase the nutrient binding capacity of the seafloor, which enhances ecosystem resistance to eutrophication. I am adapting the theories of ecological stoichiometry and explore the elemental contents in benthic invertebrates to see whether these animals function as nutrient sinks or sources in the ecosystem. I am very interested in biological traits, and the goal of my research is to understand how the features of animals are linked to whole ecosystem processes.

Current research project:

  • Elemental stoichiometry of benthic invertebrates as driver of coastal biogeochemical cycles. (PhD student: funded by University of Helsinki and the Nottbeck foundation, 2019-2021. PI: A. Villnäs).
Pinja Näkki

PhD student at Marine Research Centre in the Finnish Environment Institute. Funded by the Walter and Andrée de Nottbeck Foundation.

Marine litter is one of the most recent global environmental concerns, and information on the effects of especially small-sized plastic litter, microplastics (<5 mm), is urgently needed. I am investigating how benthic invertebrates shape the vertical distribution of microplastics on seafloors while feeding and moving in the sediment, and the capability of plastic fragments to sorb harmful substances from their surroundings. Since most of the microplastics are estimated to accumulate to the seafloor, understanding the interactions between microplastics, benthic communities, and harmful substances is crucial in assessing their potential impacts in the marine environment.

Current research project:

  • The fate and impacts of microplastics on seafloor. Funded by the Nottbeck Foundation.

Pinja’s profile in the University of Helsinki research portal.

Iris Orizar

PhD student at TZS. Funded by the Nottbeck Foundation.

My research interests is  understanding the response of phytoplankton community to environmental changes. I am specifically interested on (1) how environmental changes affect phytoplankton interaction and (2) how environmental changes affects community composition and ecological function. I am looking at the potential effects of salinity to the phytoplankton community using trait-based approach. I will determine traits distribution in the phytoplankton community at different salinity levels and hopefully used these information to determine which groups are more-likely to be benefited by the freshening of the Baltic Sea and how the shift in phytoplankton composition affects their ecological function.

Current research project:

  • Resource competitive ability of marine phytoplankton along a salinity gradient and the consequences for stoichiometric variation in the sea. Funded by The Nottbeck foundation, PI: Assistant Professor Aleksandra Lewandowska.
Mareike Paul

PhD student. Funded by Academy of Finland.

Mareike Paul is a PhD student studying the mechanisms of trace metal enrichment in the sediments of coastal European seas, including the Baltic Sea and Swedish West Coast fjords. Each of the study areas are characterized by varying environmental stress (eutrophication – hypoxia – anoxia/euxinia), as well as a range of salinity and anthropogenic impacts, all of which influence the concentration of trace metals in sediments. In turn, these factors influence the potential use of sedimentary trace metals as proxies for environmental conditions. Many details of sedimentary trace metal chemistry and enrichments are still poorly constrained, which limits their use as quantitative recorders of (past) hypoxia. The aim of this project is to shed light on these ongoing problems by studying a range of environments simultaneously.

Current research project:

  • Sedimentary trace metals: unlocking the archives of coastal marine hypoxia. Funded by the Academy of Finland
Roxana Preston

PhD Student at the University of Helsinki. Funded by the Walter & Andrée de Nottbeck Foundation 2018-2021.

Fucus vesiculosus (L.) is one of the major foundation species in the Baltic Sea littoral zone. My research aims to resolve the functional role, reproduction methods and connectivity between populations of 'free-living' F. vesiculosus that can be found living unattached on soft bottoms in sheltered bays within the Baltic. Very little is known concerning the ecological function and origins of these populations. Accordingly, through genetic analyses I will provide valuable insights into the population structure and phylogeny of these free-living forms. Additional experimentation will identify optimal growth conditions, stress tolerance, and the link between abiotic conditions and phenotype. From this I aim to determine the relationship between genotype and phenotype, and how these affect functionality. Supervisors: Jaanika Blomster, Ellen Schagerström & Perttu Seppä.

Current Research Project:

  • FunkVeg - The relative importance of shallow vegetation for ecosystem functions in the coastal zone - The role & life of free-living bladderwrack. (PhD student: Funded by the Walter & Andrée de Nottbeck Foundation 2018-2021; Project within the Baltic Bridge collaboration program).

Roxana’s profile in the University of Helsinki research portal and Roxana’s profile in Google Scholar.

Mari Vanharanta

PhD student at TZS and the Marine Research Centre, Finnish Environment Institute. Funded by the Walter and Andrée de Nottbeck Foundation.

The aim of my PhD project is to investigate the fate of the remaining phosphate pool after the spring bloom when dissolved inorganic nitrogen has been depleted. I also aim to understand how much of this excess phosphate is available for the summer bloom-forming cyanobacteria. A better understanding of the fate of the oversupply of phosphorus is critically needed to better model biogeochemical fluxes in the Baltic Sea and to improve its management.

Current research project:

  • Asking the microbes: What do you do with the excess phosphorus?