Metatranscriptomics From a Small Aquatic System: Microeukaryotic Community Functions Through the Diurnal Cycle

Area of Science:

• Aquatic microbial ecology
• Metatranscriptomics
• Freshwater ecosystem dynamics

Background:

• Planktonic organisms rely on light-dark cycles for metabolic regulation.
• Diel responses are well-studied in large lakes and marine systems, but less so in small ponds.
• Understanding diurnal patterns in small freshwater ecosystems is crucial for ecological insights.

Purpose of the Study:

• To investigate the diurnal activity of a microeukaryotic community in a temperate freshwater pond.
• To compare diel metabolic regulation in small ponds with larger aquatic systems.
• To identify key metabolic processes influenced by the light-dark cycle in pond microeukaryotes.

Main Methods:

• Collected freshwater pond samples at midday and night during summer.
• Extracted pigments and RNA for analysis.
• Performed metatranscriptomic sequencing to analyze day and night gene expression patterns.

Main Results:

• Photosynthesis-related and translational processes were upregulated during midday under high light conditions.
• Unique gene ontology classes were identified for day (photoreception, defense, stress) and night (motility, ribosomal assembly).
• Euglenophyta and Chlorophyta were identified as dominant phototrophs via pigment analysis.

Conclusions:

• The microeukaryotic community in a small freshwater pond exhibits diurnal metabolic dynamics similar to larger aquatic ecosystems.
• Light availability strongly influences gene expression, driving photosynthesis during the day and energy-intensive processes at night.
• Integrated analyses of pigments, metatranscriptomics, and environmental factors provide comprehensive insights into pond microbial metabolism.