Research Projects

Lead by Saija Saarni

Funded by: Sakari Alhopuro foundation (MIKS project), Research Council of Finland (BaSeMent project), DIWA Flagship

Archipelago Sea suffers from multiple stressors such as eutrophication, spreading dead zones and variety of pollutants, all these superimposed by the climate change. With the complex bathymetry and the semidetached basin, the water bodies are sensitive to changes in sediment and nutrient loads. Estuaries trap nutrients and organic carbon through various processes involving flocculation and aggregation, but they have the potential to act as microplastic filters as well. These processes are further altered by the changing winter ice conditions. There are indications, that future winter will be warm winters with open sea conditions prevailing throughout the year, the nutrient, detrital and organic matter leaching from Catchment increases, and hence the water quality in the sensitive ecosystems is expected to suffer. The project aims on monitoring fluxes of sediments, organic matter, trace metals, nutrients and microplastics on an estuarine transect at the inner Archipelago Sea (surrounding Kemiö island) using sediment traps. The estuarine system is being monitored since 2018 onwards to improve our understanding on climate and seasonal variability and strives to create a long time series on variables to better describe processes that control the accumulation and transport of different pollutants (including nutrients) within the land sea continuum .

Read more: https://www.sakarialhopuronsaatio.fi/en/blog/on-the-hunt-for-microplastics.html  

Funded by AXA Research Fund

Principal Investigator Saija Saarni

Although plastic is proven to be toxic and harmful to both the planet and human health, its production is reaching record levels. Plastic production and consumption generate a significant amount of hazardous waste and particles. With serious gaps lying in recycling systems across the globe, microplastics (particle size less than 5 mm) keep on infecting our environment. These substances end up in nature, where freshwaters and coastal environments are among the most affected aquatic ecosystems.

Existing laboratory tools and current techniques allow us to test plastic’s impact on species, human beings’ guts, and tissues. Still, microplastics’ toxicity and harmfulness depend on exposure and their concentration in nature. High concentrations of microplastics can weaken ecosystems’ functionality, harm human health, and disrupt a variety of businesses including fishing, farming, and water production which constitute vital sources of revenue for different communities. However, very little is known regarding microplastic concentrations’ harmful levels.

This project aims at providing evidence-based estimates geared towards identifying the chemical reactions arising from microplastics and natural sediments’ interactions to assess future risks and environmental impacts. Sedimentological, microplastic, and chemical analyzes using laminated (varved) sediment Archives are Exploited from a highly polluted Finnish lake system, located near industrial area. These various approaches will enable her to measure environmental parameters’ Evolution over time as well as the speed at which these changes occur, and, ultimately, identify future risks. The outcomes of this research project are expected to help, on the one hand, authorities and policymakers adopt adequate regulatory measures to better identify and mitigate the risks associated with these substances and on the other hand, help Insurers further assess and predict the risks arising from microplastics.

https://axa-research.org/funded-projects/health/better-identifying-and-mitigating-microplastics-threats-to-preserve-ecosystems-and-protect-human-health

https://www.youtube.com/watch?v=7ZVyQt8GjC4&t=2s

https://theconversation.com/profiles/saija-saarni-1475081/articles 

Postdoctoral researcher: PhD Maarit Kalliokoski

Led by PhD, associate professor Saija Saarni, University of Turku (Varved lake sediment records) and consortium project leader PhD Samuli Helama, Natural Resources Institute Finland (Dendrochronology and phenological data).

Funded by Academy of Finland (consortium project)

Arctic moistening (AM) and amplitude of the annual temperature cycle (AATC) form two important but understudied elements of global climate change. Decrease in AATC and increased AM in the Northern Hemisphere are evident from the instrumental records. Moreover, the variability in AATC since 1950 is exceptional in the context of the time period covered by instrumental records, but the extent to which this variability can be explained by natural or anthropogenic forcing remains unclear. The instrumental records are too short for placing the AM or the AATC changes in a long-term context and for identifying the role of different forcing mechanisms acting on various time scales. Therefore, high-resolution proxy series are needed for reconstructions of past, season-specific moisture and temperature conditions.

In this project, annually resolved proxy records from tree-ring chronologies and varved lake sediment records from a region influenced by large-scale atmospheric circulation patterns such as the Scandinavian Pattern, North Atlantic Oscillation (NAO)/Arctic Oscillation, and the East Atlantic Pattern are used for studying the amplitude of the AATC and the AM during the Common Era (past 2000 years). One of the greatest advantages of using varve records in climate studies is that the internal, laminated structure (i.e. the clastic and biogenic components and their chemical compositions) of varves represents separate seasons and their environmental/climatic signals. At the University of Turku, the physical and chemical properties of varved sediment from eight Finnish lakes are investigated using mainly micro-XRF techniques. The geochemical and physical proxies are compared with contemporary weather observation data as well as reconstructed climate data for establishing connections between chemical and physical varve composition and hydroclimate. The multi-lake dataset will be combined with tree-ring data that is mainly sensitive to growing-season temperature. Integration of these datasets allows for well-dated, season-specific reconstructions of climatic variation as opposed to reconstruction of annual means, which enables testing current hypotheses of the climatic forcing driving the decrease in AATC and increase in AM.

Project led by PhD, postdoctoral researcher Sarianna Salminen (University of Turku) in collaboration with PhD, Adjunct Professor Saija Saarni (University of Turku) and PhD, senior researcher Kaarina Lukkari (Finnish Environmental Institute). Linked to DIWA (Digital Waters flagship).

Funded by Maa- ja veskitekniki tuki ry.

Phosphorus is a factor that controls the growth of organisms in marine systems. However, excessive phosphorus input triggers hypoxia and eutrophication, which have been a problem especially in the inner Finnish Archipelago. Although the external phosphorus load has decreased, the problems caused by eutrophication have not been conquered. Previous studies have also shown the significance of internal load of phosphorus on Archipelago recovery. However, the accumulation, preservation, and long-term variations in these factors are not fully known. Thus, we trace long-term variations in sediment phosphorus concentration in detail and reveal how climate controls these variations.

We investigate recent long-term variations in the abundance of different phosphorus fractions (ie different phosphorus bonding types) in Halikonlahti Bay sediments in the inner Finnish Archipelago. Varved marine sediments have been previously used to study long-term variations in different phosphorus fractions. The long time series cover over 60 years of varved marine sediments, which enabled the investigation of each season separately. In addition, we compare these phosphorus abundance variations to climate parameters to study how variations in these parameters, such as growing season Precipitation and temperature as well as duration of snow cover, control the washout of phosphorus from the catchment. The importance of this study lies within the knowledge of the response of phosphorus to climate. This can further improve the use of Rehabilitation actions and target them better spatially and temporally.

PhD project: Mira Tammelin

Supervisors: Tommi Kauppila, Saija Saarni

Funded by: the Finnish Cultural Foundation, Maa- ja vestiteknikan tuki ry., Alfred Kordelin Foundation, the Olvi Foundation, the Geological Survey of Finland, and the Department of Geography and Geology of University of Turku

Geological conditions, together with hydroclimate, control the location, morphology, and water quality of lakes in their natural state. The sensitivity of lakes to anthropogenic influence also varies depending on the natural characteristics of the lake basins and their catchments. Understanding the natural tendency of a lake is crucial when setting Restoration targets and attempting to achieve the good status required by the Water Framework Directive of the European Union. Despite decades of water protection efforts, eutrophication remains one of the main global water quality challenges.

Boreal Lakes are often dilute and relatively nutrient-poor because of the slowly weathering crystalline Bedrock comprising acidic rocks, but naturally eutrophic Lakes also exist in certain regions. These regions are characterized by nutrient-rich soils, such as fine-grained post-glacial clays and silts. Because nutrient-rich soils have attracted cultivation early on, centuries or millennia prior to monitoring programs, the background conditions of naturally eutrophic lakes are not well known. Paleoecology provides a means to study past lake water quality by using biological proxies buried in the bottom sediments, such as diatoms, which are sensitive to changes in epilimnetic water quality.

The aim of this PhD project is to identify geological and morphological reasons behind the spatial variation in the nutrient status of Boreal Lakes in Finland prior to anthropogenic influence. Furthermore, temporal water quality changes of both nutrient-rich and -poor lakes are examined to better understand their varying responses to anthropogenic impacts. The study is based on the top-bottom sediment sampling of ~70 lakes in Northern Savo and southern Finland, as well as on the detailed temporal sampling of three naturally eutrophic lakes with varying morphological features. The main statistical methods include: 1) the development of a diatom-inferred total-phosphorus transfer function specifically targeted for naturally eutrophic lakes and 2) multivariate ordinations on Diatom assemblage, water quality, and lake Basin and Catchment characteristics data. The PhD project is interconnected with geochemical sediment accumulation research led by Jari Mäkinen at the Geological Survey of Finland.

Publications:

Mäkinen, J., Tammelin, M., and Kauppila, T. (2023) Recent increase in sediment dry matter, carbon, and phosphorus accumulation in small Boreal Lakes with Clayey catchments. Anthropocene 44: 100421. doi: 10.1016/j.ancene.2023.100421

Tammelin, M., Kauppila, T., Miettinen, J., and Jokinen, S. (2019) Eutrophication histories of three contrasting lakes in a naturally nutrient-rich Boreal watercourse. Journal of Paleolimnology 61: 165–183. doi: 10.1007/s10933-018-0051-y

Tammelin, M. and Kauppila, T. (2018) Quaternary landforms and Basin morphology control the natural eutrophy of Boreal Lakes and their sensitivity to anthropogenic forcing. Frontiers in Ecology and Evolution 6:65. doi: 10.3389/fevo.2018.00065

Tammelin, M., Kauppila, T., and Viitasalo, M. (2017) Factors controlling recent Diatom assemblages across a steep local nutrient gradient in central-eastern Finland. Hydrobiology 799: 309–325. doi: 10.1007/s10750-017-3229-9

Tammelin, M. and Kauppila, T. (2015) The inherent lushness of the Iisalmi route. Water Economics 56(2): 41–44.

Mäkinen, J., Tammelin, M., and Kauppila, T. (2012) Assessment of natural leaching in the clay areas of Southern Finland. Water Economics 53(4): 27–29.

PhD project

Karoliina Kehusmaa

Supervisors: Associate Professor Saija Saarni, Research Professor Tommi Kauppila (GTK), Professor Peter Österholm (ÅAU)

Funded by K.H. Renlund Foundation, Maa- ja vesitekniikan tuki ry.

Active and closed or abandoned mine sites are a significant point-source polluter of the aquatic environment. Sulfidic mine waters in particular remain a major and often still unresolved ecological threat to nearby waterbodies, not only due to the acidity and the high concentrations of metals, but also because of the high salinity of the drainage. Increasing salinity is a stressor on organisms adapted to freshwater conditions and can have harmful effects on the ecosystem. In some cases, the increase in salinity can lead to a change in the circulation regime of a lake. Most boreal lakes have a dimictic mixing regime where the water column is thermally stratified in winter and summer and circulates vertically twice a year during spring and autumn overturns. This circulation can be disturbed by saline mine water, because the denser saline water sinks to the bottom of the lake water column and prevents the water column from circulating. This leads to a chemical stratification of the water column where the upper water is oxic and circulates, and the bottom water is anoxic and enriched in harmful substances such as metals. This permanent stratification of the water column is known as meromixis.

The focus of my PhD project is on the evolution and effects of mine water induced meromixis in boreal natural lakes. Two small mine impacted lakes, Lake Valkeinen and Lake Sortavalanjärvi, located near now-closed Ni-Cu mines, were selected. Long-term water monitoring data from lakes is seldom available. In these cases, lake sediment offers a natural archive of past water quality in the lake. Meromictic lakes especially are a great opportunity for palaeolimnological studies because the anoxic conditions of the lake bottom protect the sediments from the post-depositional reworking by animals and plants. By studying the sediments thoroughly and with well-considered methods, we will gain valuable new knowledge on the processes controlling lake water regime shifts in general and on the processes leading to mine water induced meromixis in particular. The evolution of meromixis in the lakes will be studied temporally and spatially from lake sediment samples. In addition to investigating the past conditions from the sediments, the present conditions of the two lakes will be established from water samples and measurements of water column properties. The results of this thesis will help with the planning of more sustainable mine water policies in boreal environments.

Articles:

Kehusmaa, K., Kauppila, T., Österholm, P. et al. Properties and Stability of Mining-Induced Meromixis in Two Small Boreal Lakes in Eastern Finland. Mine Water Environ 42, 24–39 (2023). https://doi.org/10.1007/s10230-023-00915-9.

PhD project

Mohib Billah

Supervisor: Saija Saarni, Associate Professor, UTU

Funded by Maa- ja vesitekniikan tuki ry.

Rapidly changing global climate, mainly due to anthropogenic changes and natural forcings, contributes to altering the atmosphere-cryosphere-ocean system resulting in fluctuating ice extent and snow cover. Moreover, different ecosystems and habitats also seem sensitive to a range of human actions, in addition to changes in natural systems. The key to protecting ecosystems, the environment, and climate is to predict future changes and their anticipated influence. A detailed understanding of past changes is crucial for evaluating future scenarios. Changes in climate, ecosystems, and habitats that occurred within the last several millennia can be detected by investigating different natural archives, e.g., varves.

Varve, a natural archive composed of annually laminated sediment deposits in terrestrial and marine settings, can be used to reconstruct a comparatively precise chronology of paleoclimatic variability and anthropogenic changes. In addition to extracting paleoclimatic signals, it is also possible to detect anthropogenic control in varve formation from deposits within varves.

The aim of this PhD project is to reconstruct hydroclimatic and human-induced changes in the water column of Lake Kallio-kourujärvi and Malijlahti Bay from central Finland and Karhusaari Basin of the Archipelago Sea through investigating geochemical changes in the varved sediment. Statistical analysis of geochemical data and available climate data, I intend to reconstruct late Holocene hydroclimatic changes in central Finland and discuss the underlying forces responsible. In addition, geochemical analyses of the varved sediment will be carried out to detect manmade variabilities and their impact on the water quality.

PhD project: Laura Laaksonen

Supervisions: Saija Saarni, Vivi Fleming

Funded by: DIWA Flagship

Plastic pollution in natural environment is a global issue. The unique set of properties that makes plastic so practical for multiple applications, also makes it considered durable, leading to accumulation of plastic waste in the natural environment. These mobile and light weight plastic particles are able to reach even the most remoted areas on earth, far away from their primary consumption area. Marine environment is especially been exposed for plastic pollution and nowadays plastic waste is encountered as high quantities from surface waters to deep sea sediments. Enrichment of plastic pollution in seafloor sediments is affecting the aquatic ecosystems and food chains as marine organisms ingest the plastic litter by mistake.

Semi-closed basins such as the Baltic Sea are especially vulnerable for pollutants as the pollutions remains in the basin for a long time due the very limited exchange of fresh ocean water by narrow Danish Straits. Pollutants like plastic particles are originally transported from urban areas to the sea via river runoff. Whereas larger parts of plastics usually get deposited close to the coastline, the microplastics can be transported further away from the original source all the way to deep-sea sediments. Therefore, the marine sediments have been considered as a final sink for plastic litter.

The aim of this PhD project is to research the sedimentary and hydrological processes that leads to accumulation of microplastics into Baltic Sea. This study is going to research the microplastics (particles size from 1 μm to 5 mm) appearance from estuaries to deep sea depressions of Baltic Sea. The research will be carried by analyzing microplastic compositions of sediment cores and traps, and also water samples from the different depths of the water column. The focus is on evaluating the spatiotemporal accumulation of microplastic in seafloor sediment and consider the estuary-to-ocean transport and flux rate of microplastics.

This PhD project is part of Digital Waters flagship’s PhD pilot.