Species sorting along a subsidy gradient alters bacterial community stability

Area of Science:

• Ecology
• Microbiology
• Environmental Science

Background:

• Resource movement between terrestrial and aquatic ecosystems significantly impacts ecological processes.
• Allochthonous inputs, like terrestrial dissolved organic carbon (tDOC), alter resource availability and can change recipient community structure and stability.
• Microorganisms, particularly bacteria, are highly sensitive to changes in resource inputs.

Purpose of the Study:

• To investigate how varying rates of terrestrial dissolved organic carbon (tDOC) supply affect the composition and stability of aquatic bacterial communities.
• To determine if tDOC influences bacterial diversity, relative abundance, and activity.
• To assess bacterial community stability and responsiveness to nutrient pulses under different tDOC supply levels.

Main Methods:

• Experimental manipulation of terrestrial dissolved organic carbon (tDOC) supply rates in aquatic ponds.
• Measurement of bacterial community diversity, taxon-specific abundance, and activity along the tDOC gradient.
• Perturbation of communities with inorganic nutrients to assess stability and responsiveness.

Main Results:

• Increased terrestrial dissolved organic carbon (tDOC) supply significantly altered the active bacterial community composition, reducing richness and evenness.
• Species sorting was observed, with taxon-specific changes in relative abundance and activity along the tDOC gradient.
• Bacterial community responsiveness to nutrient pulses decreased with higher tDOC supply, indicating increased stability in the active community.
• Changes in diversity and stability were observed in the active bacterial community but not the total community, suggesting functional rather than structural shifts.

Conclusions:

• Terrestrial dissolved organic carbon (tDOC) supply is a key driver of aquatic bacterial community composition and stability.
• Altered aquatic-terrestrial linkages can modify the functional stability of the microbial base of aquatic food webs.
• Changes in microbial activity and stability driven by tDOC inputs can have profound effects on overall ecosystem functioning.