Dissertation 29.9.2023: Environmental change effect on quality of production in boreal lakes (Calderini)

Since only specific algal taxa can synthesize nutritional fatty acids, any shifts in the environmental conditions that influence phytoplankton communities and the intracellular production of biomolecules hold the potential to reverberate through aquatic food webs. In his study, M.Sc. Marco Calderini combined the use of controlled laboratory experimentation with real-world datasets from Finnish boreal lakes. 

Environmental shifts cause complex changes  

Calderini's investigation revealed a mosaic of effects stemming from environmental shifts. The phenomenon of lake browning, for instance, was found to benefit phytoplankton with metabolic plasticity (such as cryptophytes) that coordinate the use of organic carbon with photosynthesis to fuel their growth.  

On a different note, the compounding effects of elevated temperatures and nutrient concentrations, brought about by warming and eutrophication respectively, demonstrated a delicate equilibrium. While higher temperatures might generally decrease phytoplankton production of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), eutrophication could potentially counterbalance this decline through higher biomasses. 

Phytoplankton production of biomolecules vary with trophic state 

Calderini's study found that mesotrophic and early eutrophic lakes have the highest production of EPA and DHA per unit of phytoplankton. This translates into maximal availability of these omega-3s for higher trophic levels.  

- According to my studies, all environmental changes will play a role in shaping phytoplankton responses and ultimately the availability of omega-3s in Finnish boreal lakes, Calderini describes. 

Nevertheless, high availability of EPA and DHA in phytoplankton does not translate into higher contents in zooplankton and fish — a divergence that highlights the complex journey undertaken by biomolecules in lake ecosystems. 

- At higher trophic levels (zooplankton and fish), the content of EPA and DHA are hard to predict since the genetic, physiological and even behavioural characteristics of an organism dictate what it consumes and how the ingested biomolecules are metabolised and stored, Calderini explains. 

These results help ecologists to understand how phytoplankton production of EPA and DHA responds to environmental changes and how such differences in production affect the availability of these biomolecules for higher trophic levels. 

The examination of M.Sc. Marco Calderini’s doctoral thesis “Environmental change effect on quality of production in boreal lakes” is held on 29.9.2023 at noon in Ylistönrinne, room YAA303. Opponent Professor Lasse Riemann (University of Copenhagen, Denmark) and Custos Associate Professor Sami Taipale (University of Jyväskylä). The doctoral dissertation is held in English. 

Publishing information 

The dissertation “Environmental change effect on quality of production in boreal lakes” can be read on the JYX publication archive: https://jyx.jyu.fi/handle/123456789/88824  

More information: Marco Calderini marco.92.calderini@jyu.fi