G5 Doctoral dissertation (article)
Microbial degradation of terrestrial organic matter and microplastics in boreal lakes (2024)
Terrestrisen orgaanisen aineksen ja mikromuovien mikrobiologinen hajotus boreaalisissa järvissä

Vesamäki, J. (2024). Microbial degradation of terrestrial organic matter and microplastics in boreal lakes [Doctoral dissertation]. University of Jyväskylä. JYU Dissertations, 767. https://urn.fi/URN:ISBN:978-952-86-0105-0

JYU authors or editors

Publication details

All authors or editors: Vesamäki, Jussi

eISBN: 978-952-86-0105-0

Journal or series: JYU Dissertations

eISSN: 2489-9003

Publication year: 2024

Number in series: 767

Number of pages in the book: 1 verkkoaineisto (61, 13 sivua, 3 numeroimatonta sivua)

Publisher: University of Jyväskylä

Place of Publication: Jyväskylä

Publication country: Finland

Publication language: English

Persistent website address: https://urn.fi/URN:ISBN:978-952-86-0105-0

Publication open access: Openly available

Publication channel open access: Open Access channel

Abstract

Microbes are the main decomposers of organic matter in lakes, playing an important role as recyclers of elements and energy. Natural sources of organic matter include soil organic matter and plant litter, composed of natural polymers such as lignin and carbohydrates. Additionally, the increasing amount and high recalcitrance of plastics in the environment have become a concern worldwide. In this thesis, I study the microbial utilization of different substrates across the recalcitrance gradient (plant litter, hemicellulose, lignin, microplastics), carbon’s biochemical fate, and seasonal variation. I also aim to identify the main microbial groups behind the decomposition. The biochemical fate of carbon was affected by the substrate’s recalcitrance and chemical structure. The carbon from both recalcitrant and labile compounds was mainly respired to carbon dioxide, whereas a smaller proportion ended up in microbial biomass. However, microbial starvation led to the opposite result. Highly recalcitrant polystyrene carbon was more efficiently used for new biomass formation than carbon from labile leaves. Among environmental variables, particularly temperature controlled the decomposition rate and carbon cycling. The relative importance of assimilation in contrast to mineralization was higher in low temperatures. The effect of lake type on decomposition was unclear and contradictory. Labile carbon sources were utilized by a larger number of microbial groups than recalcitrant microplastics. Overall, natural substrates were efficiently utilized, and they subsidized microbial biomass production. In contrast, recalcitrant microplastics decomposed extremely slowly, suggesting their accumulation in lake ecosystems. The correlation of temperature with higher mineralization rates indicates that elevating temperature increases microbial mineralization of terrestrial polymers and thus further increases carbon emissions from lakes, whereas the proportion of terrestrial carbon bound to microbial biomass and aquatic ecosystems decreases.

Keywords: lakes; boreal zone; microbes; microplastic; disintegration; mineralisation; polymers; isotopes; waste utilisation; biomass (ecology); carbon; doctoral dissertations

Free keywords: microbial decomposition; stable isotopes; terrestrial organic matter

Contributing organizations

Ministry reporting: Yes

VIRTA submission year: 2024