Ongoing projects in the Marine Ecosystems Research Group:

Microbiology: benthic foraminiferal ecology

Microbiology: the missing link in benthic foraminiferal ecology

The discovery of nitrate accumulation and denitrification in benthic foraminifera challenges our current understanding of the physiology of these common marine eukaryotes. Deeper investigation of foraminiferal ecology, and its impact on benthic carbon and nutrient cycling, are required to provide a comprehensive understanding of modern-day biogeochemical processes in surface sediments. Understanding of the role of potential endosymbionts in foraminiferal carbon and nitrogen processing is currently also lacking and must be critically assessed in relation to sediment biogeochemical processes.

This project focusses on developing a mechanistic understanding of interactions between benthic foraminifera, their potential endobiont community and the sediment microbial community in the context of sediment carbon and nitrogen dynamics. The project applies state-of-the-art molecular approaches, including Next Generation Sequencing, to study foraminiferal endobiont communities, and their direct links with the ambient sediment bacterial community and biogeochemical processes. In addition, trophic interactions between foraminifera and other sedimentary (micro-) organisms are assessed in the context of benthic food webs and carbon transfer.

People: Karoliina Koho, Iines Salonen, Myrsini Chronopoulou, Hidetaka Nomaki (Japan Agency for Marine-Earth Science and Technology- JAMSTEC), Gert-Jan Reichart (Royal Netherlands Institute for Sea Research-NIOZ, Netherlands)

Funding: Academy of Finland Research Fellowship to Karoliina Koho

Next generation tool for environmental assessment

This project aims to develop a new, economically sound tool for ecosystem assessment, which is able to deliver extensive information on biodiversity and environmental status of marine environments. Dead zones, areas of seafloor devoid of animal life, are expanding as a result of increased anthropogenic nutrient loading in coastal environments. Furthermore direct anthropogenic impacts such as trace metal pollution are observed in some areas. As a consequence, there is a growing demand for assessment of human impacts on marine habitats. However, the traditional monitoring approaches are very labor intensive, and are under financial pressure to become more cost-effective. To respond to this need, the project will develop a monitoring tool based on genetic sequencing of sediment samples. The results will be utilized by environmental agencies and other end users interested in quantification and monitoring of ecosystem health in a cost-effective manner.

People: Karoliina Koho, Jesse Harrison, Iines Salonen, Myrsini Chronopoulou, Tom Jilbert, Joanna Norkko, Laura Uusitalo (Finnish Environment Institute-SYKE)

Funding: Academy of Finland Key Funding to Karoliina Koho

Biogeochemical links: climate change and eutrophication

Biogeochemical links between climate change and eutrophication in the Baltic Sea

Climate change and eutrophication are two major stressors which deteriorate the health of the Baltic Sea, in particular by driving the expansion of low-oxygen conditions. However, the feedbacks between these stressors have remained largely unexplored. Such feedbacks are possible because the distribution of two greenhouse gases in marine systems (nitrous oxide and methane) are related to oxygen conditions. In this project we evaluate the Baltic Sea sources and sinks of these gases. We study the factors controlling the balance between their production and consumption. We study coastal sediments and pelagic redoxclines, both of which are hotspots of the organic matter mineralization processes that generate the greenhouse gases. We use stable isotope and radiotracer techniques to test the stability of greenhouse gas sources and sinks under variable oxygen conditions. Eventually, the relationships between oxygen, nitrogen removal and greenhouse gas production will be implemented in large-scale biogeochemical models, increasing their prognostic accuracy.

People: Susanna Hietanen, Dana Hellemann, JP Myllykangas, Tom Jilbert, Maren Voss (Leibnitz Institute for Baltic Sea Research-IOW, Germany)

Funding: Academy of Finland Research Fellowship to Susanna Hietanen

Sedimentary trace metals - coastal hypoxia

Sedimentary trace metals: unlocking the archives of coastal marine hypoxia

"Dead zones" are areas of the ocean where the water contains no oxygen, and most marine organisms cannot survive. These zones are increasingly common in coastal areas of Europe, including the Baltic Sea, where inputs of waste water and agricultural runoff have caused widespread eutrophication. It is important to know how dead zones have expanded in the past, in order to estimate sustainable inputs of nutrients for the future. Unfortunately, many coastal areas have not been monitored sufficiently well to provide this information. This project will fill in these gaps by studying sediment cores from coastal regions of Europe. Using advanced chemical analyses, the project will focus on "trace" metals in sediments, which provide a natural archive of the size of dead zones in the past. New information about the past expansion of dead zones will be used to improve existing models of nutrient cycling in the Baltic Sea.

People: Tom Jilbert, Bo Gustafsson, Christoph Humborg, Alf Norkko, Caroline Slomp (Utrecht University, Netherlands), Helena Filipsson (Lund University, Sweden)

Funding: Academy of Finland Research Fellowship to Tom Jilbert

Iron and manganese cycling in boreal estuaries

Iron and manganese are two commonly occurring metals that take part in microbially mediated chemical reactions.  As such, they are an important source of energy for microorganisms in a range of environments. Estuaries are transitional aquatic systems with strong gradients of salinity, oxygen and pH conditions, which influence the cycling of iron and manganese and hence their potential role in microbial processes. Eutrophication, land use change and climate change are causing major disruptions in biogeochemical cycling in boreal estuaries today. In particular, the rapid accumulation of organic materials in estuarine sediments has stimulated microbial processes such as methanogenesis and altered the oxygen balance of coastal waters. Using geochemical analyses of both water column and sediments, we study the effects of these changes on the cycling of iron and manganese.

People: Tom Jilbert, Eero Asmala, Susanna Hietanen, Joonas Virtasalo (Geological Survey of Finland), Christian Schröder (Stirling University, UK)

Funding: Tenure Track Starting Package to Tom Jilbert (Faculty of Biological and Environmental Sciences, University of Helsinki)


Resource competitive ability of marine phytoplankton along a salinity gradient and the consequences for stoichiometric variation in the sea

Global warming causes changes in oceanic salinity with fresh regions, such as Baltic Sea, becoming fresher and salty regions becoming saltier. Sensitivity to salinity change differs among species causing shifts in community composition, which in turn affect functioning of ecosystems and oceanic biogeochemistry. Within Phytos we investigate how salinity affects the resource utilization traits that determine competitive ability of different phytoplankton groups and how this transfers into stoichiometric patterns observed in the Baltic Sea.

Funding: Walter and Andrée de Nottbeck Foundation

People: Aleksandra Lewandowska, Iris Orizar

Seagrass functional ecology

Seagrasses and other aquatic plants are foundation species that maintain biodiversity and modify the abiotic and biotic environment including primary and secondary production. They form vast underwater meadows that can contain up to 8-9 co-occurring plant species. Our aim is to look at how the diversity of aquatic plant species and their traits i.e. functional diversity, influence ecosystem processes such as primary production along gradients in salinity and wave exposure and the resilience and recovery of benthic vegetated habitats. We investigate the link between aquatic plant traits and ecosystem functioning in the brackish-water Baltic Sea and along the coast of Western Australia. The project outcome is to discern how diverse temperate meadows maintain ecosystem functioning locally in different habitats and in geographically contrasting regions.

People: Camilla Gustafsson, Charlotte Angove, Laura Kauppi, Alf Norkko (TZS), Gary Kendrick and research team (University of Western Australia), Johan Eklöf and research team, Tiina Salo (Stockholm University)

Funding: Walter and Andrée de Nottbeck Foundation, Academy of Finland, UWA Research Collaboration Award, Swedish Cultural Foundation

The breathing seascape

The breathing seascape: resolving ecosystem metabolism and habitat-function relationships across coastal habitats

Coastal ecosystems are exceptionally diverse and productive environments that maintain vital ecosystem functions and services. These ecosystems are, however, under threat from eutrophication, pollution, overfishing and construction. In order to manage the ecosystems wisely, we need to advance our understanding of the role of biodiversity for ecosystem functioning and metabolism. We use novel instruments (Aquatic Eddy Covariance), which for the first time allows us to measure oxygen production and consumption in different key habitats of the Baltic Sea, such as seagrass meadows, mussel beds, bladder wrack belts, bare sand and mud. The measurements can then be linked to the biodiversity and nutrient cycling in these different habitats. Using habitat maps from the national underwater mapping program VELMU, we will scale up our findings to the ecosystem level, i.e. to the scale of societal relevance and management.

People: Alf Norkko, Karl Attard, Iván Rodil and the rest of the benthic ecology team (TZS), Ronnie Glud (University of Southern Denmark)

Funding: Academy of Finland, Walter and Andrée de Nottbeck Foundation 

Funding details:

The Breathing Seascape: resolving ecosystem metabolism and habitat-function relationships across coastal habitats (PI Prof Alf Norkko, Academy of Finland Project ID 294853. 01-09-2016 to 31-08-2020) 

​Sediment resuspension: an understudied key factor for biogeochemical functioning of coastal habitats (PI Prof. Ronnie N. Glud, The Danish Council for Independent Research. 01-01-2018 to 31-12-2019)


Fate of algal detritus

Baltic Sea eutrophication: the effects of increasing accumulations of drifting algal detritus on the functioning of shallow coastal habitats (01.01.2017–31.12.2020)

We study the effects of increasing accumulations of macroalgal detritus on the functioning of coastal habitats. An excess of ephemeral macroalgae and drifting detritus accumulations due to eutrophication can influence almost all levels of ecology, from species interactions to productivity, food-web stability and population dynamics. The goal of the project is to examine how detritus source dynamics might affect benthic communities, oxygen metabolism and the composition of carbon in coastal areas. We will assess the relative importance of the organic carbon derived from primary producers and from detritus into the coastal food-web using stable isotopes (δ13C, δ15N and δ34S). The project is expected to (a) deliver significant advances with regards to an understanding of the ecological role of increasing algal detritus on the functioning of shallow habitats, and (b) provide new insights into the fate of organic carbon production in coastal ecosystems.

People: Iván F. Rodil, T.I. Kahma, Alf Norkko, Christoph Humborg (Baltic Sea Centre, Stockholm University)

Funding: Walter and Andrée de Nottbeck Foundation

Living at the edge

Living at the edge (1.1.2017 – 31.12.2020)

We are studying population ecology of blue mussels from the perspective of species distribution margins. Species living at the edge of their distribution face a number of challenges that differ from those they face in their distribution centers. With ongoing large-scale changes in the environment, including global climate change, understanding range ecology is becoming increasingly important. We are trying to understand the factors that structure Baltic blue mussels and how changes in blue mussel beds affect the wider coastal community that is dependent on them. We are therefore looking at the links between blue mussels and fish and between blue mussels and eider ducks.

People: Mats Westerbom, Kim Jaatinen, Mikael Kilpi, Olli Mustonen, Alf Norkko

Collaboration: Patrik Kraufvelin (SLU), Baltic Bridge

Funding: Svenska kulturfonden

COCOA - the coastal nutrient filter

Nu­tri­ent cock­tail in coastal zones of the Baltic Sea (1.1.2014-31.12.2017)

The role of the coastal zone as a filter for nutrients from land to the sea is largely an unknown black box. The BONUS-project COCOA will analyse the pathways of nutrients in the coastal zones of the Baltic Sea by quantifying the role of bacteria, phytoplankton, benthic microalgae, seagrasses, macroalgae and fauna in transforming and accumulating nutrients in four different types of coastal ecosystems (learning sites: lagoons, river-dominated estuaries, embayments, and archipelagos). In the area around TZS, we concentrate on the links between biodiversity and nutrient cycling.

People: Alf Norkko, Anna Villnäs, Johanna Gammal, Mari Joensuu, Guillaume Bernard, Joanna Norkko (TZS), Dana Hellemann, Susanna Hietanen (HU), and partners in Finland, Denmark, Sweden, Germany, Lithuania, Poland, Russia, and the Netherlands.

Funding: BONUS (EU) and Academy of Finland

BONUS project website

Diversity strikes back

Diversity strikes back: Does trait diversity enhance resilience in aquatic plant and faunal ecosystems (2017-2022)

Diverse communities are hypothesized to be able to maintain functioning during environmental disturbance because of species redundancy, where more resistant species can step up and continuously maintain functioning when more sensitive species are lost. Despite increasing numbers of studies on plant functional traits and ecosystem processes in the terrestrial realm, analogous studies in marine environments and particularly seagrasses and other aquatic plants are very few although humans heavily depend on seagrass ecosystems for many goods and services. The infaunal assemblages associated with aquatic plant communities often differ in species composition and densities compared to bare sediment, and contribute to important ecosystem functions, such as provision of nutrients for primary production. The main aim of this project is to explore how the functional diversity of aquatic plants affects the resilience of benthic vegetated habitats. Due to the high species and trait diversity of the aquatic plant communities in the northern Baltic Sea they provide an excellent model system to study how trait diversity affects community resilience.  We investigate this in a long-term field experiment, where we follow the recovery of vegetation and the associated faunal communities after a disturbance (simulated drift algal coverage) for five years.

People: Camilla Gustafsson (TZS), Tiina Salo (Stockholm University), Laura Kauppi (TZS)

Funding: Svenska Kulturfonden

Wriggling worms

Chasing a moving target: From wriggling worms in the warming mud to ecosystem-level effects and management of our valuable seas (1.1.2019-31.12.2020)

Soft bottoms and their macrofaunal communities have an invaluable importance for coastal ecosystem functioning through their role in nutrient cycling. Management decisions conserving these valuable ecosystems are based on model predictions of key ecosystem processes and services. Bioturbation performed by benthic fauna in aquatic environments is one of these key processes regulating nutrient retention and release, and oxygenation of the sea floor. Changes in the structure of the macrofauna communities as well as changes in the environment affect the outcome of bioturbation, but our understanding of the underlying mechanistic processes and their context-dependency remains limited. Building on the strong background of observational data, the main objective of this project is to provide mechanistic understanding of the bioturbation processes and the relative importance of factors driving these processes underlying the functioning of seafloor ecosystems. The experimental results will be further used to couple the numerical model of benthic fauna with that of biogeochemical cycling.

People: Laura Kauppi (TZS), Bo Gustafsson (Stockholm University), Guillaume Bernard (CNRS/University of Bordeaux), Joanna Norkko (TZS), Alf Norkko (TZS)

Funding: Walter and Andrée de Nottbeck Foundation

Biodiversity and Ecosystem Services

The importance of biodiversity for coastal ecosystems services - consequences of environmental change (1.1.2017 -> )

Coastal marine ecosystems with diverse and healthy communities sustain a wide range of important ecosystem services including oxygen production, nutrient cycling and water filtration. However, these ecosystems are increasingly affected by environmental stressors such as eutrophication and global warming. The goals of this project are to a) increase our understanding regarding what ecosystem services our coastal environments provide and b) explore how environmental change alters the provision of these services. This will be achieved by building further on existing monitoring data across local, regional and a Baltic Sea-wide scale.

People: Anna Villnäs, Alf Norkko

Funding: Sophie von Julins Stiftelse


Benthic nutrient pools

Elemental stoichiometry of benthic invertebrates as predictor of biogeochemical cycles (1.1.2019-31.12.2021)

What is the role of benthic faunal carbon and nutrient pools in the coastal ecosystem? This project will provide new information regarding carbon (C) : nitrogen (N): phosphorous (P) content ratios and allometric traits of important benthic species. By performing field sampling over temporal and spatial scales, the project will provide novel insight into the intra- and interspecific variability in nutrient stoichiometry of macrobenthic species in relation to available food sources (as revealed by stable isotope analysis) and environmental conditions. The information will be used to quantify the contribution of benthic communities to sediment nutrient storage and recycling rates over temporal and spatial scales, by utilizing existing, large-scale monitoring data from the Baltic Sea.

People & Collaborators: Anna Villnäs (PI), Saara Mäkelin, Aleksandra Lewandowska, Iván Franco Rodil (TZS), Agnes Karlsson, Christoph Humborg (Stockholm University), Michael Vanni (Miami University).

Funding: Academy of FinlandUniversity of Helsinki 3 year research grant, Walter and Andrée de Nottbeck Foundation


Impact of climatic variability on biogeochemical processing of riverine organic carbon in coastal environments (01.09.2017-31.08.2020)

Climate change will alter the annual discharge patterns of world’s rivers, and cause more frequent and more extreme flood events. As river discharge increases and its temporality changes, also changes the quantity and characteristics of the associated riverine organic carbon (OC) loading from the terrestrial system to the coastal seas. Additionally, in recent decades there has been a long-term increase of riverine OC concentrations throughout northern hemisphere. The effect of these pressures on coastal seas is largely unknown, as systematic approaches of linking varying river discharge, increasing OC loading and estuarine carbon cycling are lacking.

The proposed research aims to quantify the couplings between the short-term variations in river discharge, the characteristics of the OC entering the estuarine environment and the response in the estuarine ecosystem. The results will ultimately contribute to gaining fundamental understanding about the climatic drivers of organic carbon cycling in coastal environments.


People: Eero Asmala (PI) et al.


Funding: Academy of Finland


The functional role of vegetation in the Baltic Sea

Bladderwrack is an important habitat forming species in coastal areas of the Baltic Sea, providing shelter and food for a range of fauna and flora. Normally considered a ‘rocky shore organism’, it is an intriguing quirk that bladderwrack can also be found free-living, unattached to the substratum. Normally found on soft bottoms, these populations are perennial and can be quite extensive (10-100m2). In this project we are delving into the peculiarities of this free-living morph. Encompassing both functional and population ecology, our research questions are: 1) What is the functional role of these free-living populations and 2) Where do they originate from and how do they reproduce?

People: Jaanika Blomster, Roxana Preston, Ellen Schagerström, Perttu Seppä, Elina Leskinen, Lena Kautsky, Camilla Gustafsson, Susanne Qvarfordt, Anne Aittamäki, Antti Takolander, Åsa Austin Nilsson, Johan Eklöf, Joakim Hansen, Sofia Wikström

Funding: Walter and Andrée de Nottbeck Foundation, CF Lundström Foundation

Role of biodiversity in maintaining coastal ecosystem health

Assessing the role of biodiversity in maintaining coastal ecosystem health in the Anthropocene (04.2019-03.2021)

With globally accelerating rates of species loss, it is imperative we more fully understand the role of biodiversity in maintaining ecosystem function. Ecosystem functions are the ‘jobs’ that are performed by particular species that contribute to ecosystem service delivery (i.e. the benefits humans derive). A simplified approach assumes that within groups of species that do the same job, some are potentially redundant, and this redundancy should buffer (or provide resilience) against some level of species loss. However, recent research has highlighted that there are multiple other factors that determine resilience to human induced species loss beyond the degree of redundancy; including individual species traits that are tolerant to stress, and population connectivity in the landscape. Using field experiments, this project will investigate the attributes that make seafloor macrofaunal communities resilient to disturbances at different spatial and temporal scales (e.g. patch-scale fishing disturbance vs. landscape-scale coastal eutrophication). A key part of the project is to explore the resilience attributes that are important under both high and low scenarios of biodiversity (Baltic Sea where seafloor biodiversity is low and anthropogenic stresses are high vs. New Zealand where biodiversity is high). This research will shed new light on how key elements of biodiversity may respond to future environmental change, enabling a practical way of assessing of societally important coastal ecosystems.

People: Rebecca Gladstone-Gallagher (University of Auckland, New Zealand)

Funding: Rutherford Foundation Postdoctoral Fellowship (New Zealand), and Walter and Andrée de Nottbeck Foundation

Organic carbon composition and benthic nitrate reduction

Elucidating seasonal substrate limitation of benthic nitrate reduction in the coastal Baltic Sea (2020-2021)

The reduction of bioavailable nitrate to non-bioavailable di-nitrogen gas via denitrification is an important ecosystem service particularly in eutrophic coastal areas. At the Baltic Sea coast, benthic denitrification displays a pronounced seasonality with contrasting patterns between photic and aphotic sediments, which is particularly obvious in early spring when process activity is limited in aphotic sediments only. This limitation has been attributed to seasonally low availability of labile organic carbon, the electron donor in heterotrophic denitrification; yet, it remains elusive how labile organic carbon can become limiting in a eutrophic system such as the Baltic Sea coast. Hence, in this project I investigate the link between organic carbon composition and heterotrophic benthic nitrate reduction processes (denitrification and dissimilatory nitrate reduction to ammonium) to identify key compounds of organic carbon preferentially used in nitrate reduction. I do this by characterizing the biochemical composition of in situ organic carbon in both photic and aphotic Baltic coastal sediments before, during and after the spring bloom, while concurrently quantifying benthic nitrate reduction rates and  applying substrate addition experiments. The methodological approach includes both established and cutting-edge analysis techniques, such as isotope pairing techniques and Fourier-transform ion cyclotron resonance mass spectrometry. The results obtained will enable us to understand the observed substrate limitation and to establish a more distinct view on the ʻlabilityʼ characteristic of organic carbon.

People: Dana Hellemann (HU), Mikko Kiljunen (University of Jyväskylä), Boris Koch (Alfred-Wegener-Institute Bremerhaven, Germany), Joanna Norkko, Alf Norkko (TZS)

Funding: Walter and Andrée de Nottbeck Foundation