The trophic interaction of freshwater chironomids using DNA metabarcoding and stable isotope analysis in stream...

Identifying the food sources of aquatic insects is crucial for understanding their ecological roles and ecosystem dynamics. However, obtaining direct information on food sources in freshwater ecosystems can be challenging. This study employed DNA metabarcoding and stable isotope analysis to identify the primary food sources of chironomids, the first dominant group of aquatic insects, and to monitor their response to water temperature changes. We conducted field sampling surveys to identify the most dominant taxonomy and analyze the gut contents of chironomids in the urban stream of Yeosu City Center, South Korea. DNA metabarcoding analysis of chironomid gut contents revealed that algae were the dominant food source, with a high relative abundance of diatoms (Bacillariophyta) and green algae (Chlorophyta). Stable isotope analysis of chironomid tissues and their habitat environment supported these findings, indicating that particulate organic matter and algae were the primary dietary components. We found that seasonal changes influenced chironomid community composition and food source preferences. The genus Cricotopus (Orthocladiinae) was dominant in cooler water temperatures, while Chironomus (Chironominae) became dominant as water temperatures increased. DNA metabarcoding analysis revealed that Cricotopus consumed a wider variety of algae, including diatoms and green algae, while Chironomus primarily consumed diatoms. This study highlights the importance of DNA metabarcoding and stable isotope analysis as effective tools to assess food source diversity and trophic levels in aquatic insects and their associated environmental conditions. The findings provide new insights into the trophic relationships within freshwater ecosystems and the potential impacts of environmental changes on aquatic insect communities.