Microbial communities are sensitive indicators for freshwater sediment copper contamination.

Area of Science:

• Environmental Science
• Microbiology
• Ecotoxicology

Background:

• Freshwater systems worldwide are increasingly contaminated with copper due to anthropogenic activities like mining and agriculture.
• Prokaryotes are crucial for ecosystem functions, yet their response to copper in freshwater sediments is understudied, with only three prior investigations.
• Existing sediment quality guideline values (SQGV) may not adequately protect microbial communities from copper toxicity.

Purpose of the Study:

• To investigate the impact of varying copper concentrations on prokaryote community structure and function in freshwater sediments.
• To assess the ecological relevance of copper contamination below established SQGV.
• To provide a comprehensive analysis of microbial community shifts using advanced molecular and physiological techniques.

Main Methods:

• Outdoor mesocosms were utilized to simulate freshwater environments with controlled copper spiking.
• Prokaryote community taxonomic profiles were determined using next-generation high-throughput sequencing of 16S ribosomal RNA (rRNA) genes (DNA and RNA).
• Community-level physiological profiling was conducted using Biolog Ecoplates and leaf analogue baiting to assess functional responses.

Main Results:

• Distinct changes in prokaryote community composition were observed at copper concentrations as low as 46 mg/kg, identified through both DNA and RNA 16S rRNA gene profiling.
• Elevated copper levels significantly reduced the utilization of carbon substrates by sediment microbial communities.
• Prokaryote communities colonizing leaf analogues in copper-spiked mesocosms differed markedly from those in control environments.

Conclusions:

• Copper contamination, even at concentrations below current regulatory guidelines, profoundly impacts freshwater prokaryote community structure and function.
• Observed alterations in microbial communities and carbon substrate utilization suggest potential disruption of critical ecosystem processes like carbon cycling.
• The findings highlight the need for revised sediment quality guidelines to better protect vital freshwater microbial ecosystems from copper pollution.