Decrease of Population Divergence in Eurasian Perch (Perca fluviatilis) in Browning Waters: Role of Fatty Acids and...

Area of Science:

• Environmental Science
• Ecology
• Evolutionary Biology

Background:

• Climate change is increasing dissolved organic carbon (DOC) in Northern Hemisphere freshwater systems, leading to water "brownification."
• Previous studies show brownification affects Eurasian perch (Perca fluviatilis) morphology, but drivers remain unclear.
• This study investigates the link between DOC, polyunsaturated fatty acid (PUFA) composition, and perch morphological divergence.

Purpose of the Study:

• To explore the relationship between DOC concentration, PUFA profiles, and morphological divergence in Eurasian perch.
• To assess the impact of degraded visual conditions on perch foraging efficiency in brown water environments.
• To identify potential causes for observed habitat-specific morphological variations in perch.

Main Methods:

• Conducted a field study across six lakes with varying DOC concentrations, analyzing perch morphology and PUFA composition.
• Performed a laboratory experiment to evaluate perch foraging efficiency on littoral prey under simulated brown water conditions.
• Measured perch attack rates in feeding trials with altered habitat structure and feeding modes.

Main Results:

• Perch morphological divergence generally decreased with increasing DOC concentrations.
• Specific PUFAs linked to morphological differences between clear and brown-water perch showed a tendency to decline with increasing DOC.
• Perch foraging efficiency on littoral prey was significantly reduced in brown water due to degraded visual conditions.

Conclusions:

• Water brownification negatively affects perch foraging ability, impacting their capacity to locate specific food resources.
• Impaired foraging due to poor visibility may be a key factor limiting the development of evolutionary traits like habitat-specific morphological divergence in perch.
• While PUFA levels showed a trend, they did not indicate severe essential fatty acid limitation in brown water perch.