Effect of microplastics on ecosystem functioning: Microbial nitrogen removal mediated by benthic invertebrates

Area of Science:

• Environmental Science
• Ecotoxicology
• Microbiology

Background:

• Microplastic pollution is a growing concern in aquatic ecosystems.
• The impact of microplastics on ecosystem functions, particularly nitrogen cycling mediated by benthic organisms, is poorly understood.
• Benthic invertebrates play a key role in sediment nutrient dynamics.

Purpose of the Study:

• To investigate the effects of microplastics on nitrogen removal in freshwater sediments.
• To understand the interactive effects of microplastics and benthic invertebrates (chironomid larvae) on nitrogen cycling.
• To assess the impact of microplastics on microbial communities involved in nitrogen removal.

Main Methods:

• Microcosm experiments were conducted using freshwater sediments.
• Sediments were exposed to polyethylene microplastics at varying concentrations (0, 0.1, 1 wt%).
• The presence or absence of chironomid larvae was varied, and nitrogen removal rates were measured after 28 days.

Main Results:

• Both microplastics and chironomid larvae independently increased nitrogen removal by promoting denitrifying and anammox bacteria.
• In the presence of both microplastics and chironomid larvae, nitrogen removal was less than additive, particularly at 1 wt% microplastics.
• Microplastics adversely affected microbially mediated nitrogen removal when invertebrates were present.

Conclusions:

• Microplastics can interfere with nitrogen cycling in freshwater ecosystems, especially when benthic invertebrates are involved.
• The concentration of microplastics influences the extent of disruption to nitrogen removal processes.
• Further research is needed for a comprehensive understanding of microplastic impacts on freshwater ecosystem functions.