Connectivity in rivers: Can it be assessed by tracing microorganisms?

Area of Science:

• Ecology
• Environmental Science
• Microbiology

Background:

• River connectivity is crucial for ecosystem function but is threatened by human activities.
• Traditional assessments of river connectivity focus on physical and chemical aspects, neglecting ecosystem-level characterization.
• Microbial communities are sensitive to environmental changes and exhibit continuity, making them potential indicators of river connectivity.

Purpose of the Study:

• To investigate the feasibility of using microbial community composition to characterize river connectivity.
• To analyze the connectivity of environmental characteristics, bacterial communities, and eukaryotic microbial communities in the Nu River.
• To identify the driving factors influencing microbial and environmental connectivity.

Main Methods:

• Bayesian classification and generalized additive models were employed.
• Analysis included environmental characteristics, bacterial communities, and eukaryotic microbial communities.
• Longitudinal connectivity was assessed for water and sediment components.

Main Results:

• Microbial-based longitudinal connectivity is more sensitive to environmental heterogeneity than environmental connectivity.
• Bacterial community connectivity is more sensitive than eukaryotic microbial community connectivity.
• Water-based connectivity is more indicative than sediment-based connectivity, with bacterial transport influenced by sediment release.
• Human activities significantly impact bacterial community connectivity during low-flow periods, showing a negative correlation with land use.
• Natural factors dominate during high-flow periods for bacterial communities, while eukaryotic microbial communities are influenced by natural factors in low-flow and human factors in high-flow periods.

Conclusions:

• Microbial community composition provides a novel and sensitive approach to evaluating river connectivity.
• Understanding microbial connectivity is essential for effective river management, especially considering the differential impacts of human activities and natural factors across flow periods.
• The study offers a scientific basis for incorporating microbial indicators into river health assessments and management strategies.