Salinity significantly reduces plastic-degrading bacteria from rivers to oceans

Area of Science:

• Environmental Microbiology
• Marine Biology
• Plastic Pollution Research

Background:

• Microplastics (MPs) are ubiquitous environmental contaminants in aquatic ecosystems.
• Limited understanding exists regarding microbial community shifts on MPs as they transition from rivers to marine environments.
• Changes in plastic-degrading bacteria during this transition remain understudied.

Purpose of the Study:

• To investigate the bacterial diversity and composition on MPs and planktonic bacteria in river and offshore waters of Macau.
• To analyze the abundance of plastic-degrading bacteria, their metabolic pathways, and related enzymes.
• To assess the impact of environmental factors, such as salinity, on these microbial communities.

Main Methods:

• Sampling of surface water and MPs from four river and four offshore stations in Macau.
• Analysis of bacterial diversity and species composition using molecular techniques.
• Quantification of plastic-degrading bacteria and identification of related metabolic pathways and enzymes.

Main Results:

• Distinct microbial communities were observed on MPs compared to planktonic bacteria (PB) in both river and offshore environments.
• The proportion of key bacterial families on MP surfaces increased from rivers to estuaries.
• MPs significantly enriched plastic-degrading bacteria, with higher proportions of plastic-related metabolic pathways found in riverine MPs compared to offshore.
• Salinity was identified as a significant factor influencing the distribution of plastic-degrading bacteria.

Conclusions:

• Riverine MP-associated bacteria exhibit a higher potential for plastic degradation compared to those in offshore waters.
• Slower degradation rates of MPs in marine environments suggest a persistent threat to marine ecosystems and human health.
• Understanding microbial dynamics on MPs is crucial for assessing their environmental fate and impact.