Dissertation: Multiple stressors magnify fungicide impacts on freshwater leaf‑shredders (Mohan)
In his doctoral thesis research, Doctoral Researcher Akshay Mohan shows that a widely used fungicide can sharply reduce feeding in the freshwater isopod Asellus aquaticus, an important leaf-shredding detritivore.
- Because these animals help break down fallen leaves, reduced feeding can slow the recycling of organic matter that supports stream and lake food webs, explains Doctoral Researcher Akshay Mohan from the University of Jyväskylä.
Chemical stress looks different under multiple stressors
The work also shows why single-stressor tests can underestimate real-world impacts. When fungicide exposure was combined with predation risk or a short heatwave, the outcome changed. Mohan discovered that anti-predator responses weakened, feeding could drop even further, and recovery after the heatwave was slower than expected.
- In other words, the same chemical stress can look very different depending on what else the animals are facing and whether the system is in a stress or recovery phase, says Mohan.
Seeing the bigger picture through Nested Feedbacks framework
The dissertation work also introduces a conceptual framework, “Nested Feedbacks,” which links short-term trait changes such as behaviour and condition to longer-term population outcomes.
- The aim is to help forecast when ecosystems may buffer stressors versus when small disruptions can cascade into persistent decline, and to support monitoring approaches that can trigger early intervention, specifies Mohan.
Akshay Mohan completed his master’s thesis at the Indian Institute of Science Education and Research (IISER) Thiruvananthapuram and began doctoral studies at the University of Jyväskylä in 2022. The supervisors for the doctoral thesis are Professor Katja Räsänen and Dr. Blake Matthews.
M.Sc. Akshay Mohan defends the doctoral dissertation “Multi-stressor interactions in freshwater ecosystems: fungicide impacts on a keystone detritivore, and conceptual advances” on Friday 6 February 2026 at 12:00 at Ylistönrinne lecture hall YAA303. Opponent is Associate Professor Micael Jonsson (Umeå University) and custos is Professor Katja Räsänen (University of Jyväskylä). The language of the event is English.
The event will be streamed live online:
Follow the event via live stream on Moniviestin
The dissertation “Multi-stressor interactions in freshwater ecosystems: fungicide impacts on a keystone detritivore, and conceptual advances” will be available in the JYX publication archive: https://jyx.jyu.fi/jyx/Record/jyx_123456789_108301?sid=244568875
