Does invasive submerged macrophyte diversity affect dissimilatory nitrate reduction processes in sediments with...

Area of Science:

• Environmental Science
• Ecology
• Limnology

Background:

• Nitrogen removal is vital for eutrophic lake restoration, with microorganisms and aquatic plants playing key roles.
• Microplastic (MP) pollution and invasive aquatic plants pose significant threats to lake ecosystems.

Purpose of the Study:

• To investigate the impact of invasive submerged macrophyte diversity on nitrogen removal processes (denitrification, anammox, DNRA) in lake sediments.
• To assess the influence of microplastics on these microbial processes and invasive species dynamics.

Main Methods:

• Field mesocosm study examining lake sediments with varying microplastic concentrations.
• Quantification of denitrification (DNF), anammox (ANA), and dissimilatory nitrate reduction to ammonium (DNRA) rates.
• Assessment of invasive and native macrophyte biomass and sediment environmental parameters.

Main Results:

• Invasive macrophytes suppressed denitrification (DNF) rates, while DNRA and ANA showed less sensitivity to species diversity.
• Sediment microplastics increased invasive macrophyte biomass but did not directly impact microbial processes.
• Microplastics altered the sediment environment, increasing DNF rates and the competitive advantage of DNF over DNRA, leading to a decoupling of DNF and ANA.

Conclusions:

• Invasive submerged macrophytes significantly alter sediment nitrogen cycling, primarily by suppressing denitrification.
• Microplastics exacerbate the impact of invasive species by promoting their growth and modifying nitrogen cycling pathways.
• Findings highlight the complex interactions between invasive species, microplastics, and the lake nitrogen cycle, with implications for lake restoration strategies.