The Eukaryotic Life on Microplastics in Brackish Ecosystems.

Area of Science:

• Marine Biology
• Environmental Science
• Microbiology

Background:

• Microplastics (MPs) are global contaminants, with rivers and wastewater treatment plants (WWTPs) introducing millions of tons annually into aquatic environments.
• MPs offer artificial surfaces for microbial colonization, yet knowledge of these attached communities is limited, especially in brackish ecosystems.
• Previous studies focused on prokaryotic and fungal communities; this research investigates the total eukaryotic communities on MPs in brackish environments.

Purpose of the Study:

• To analyze the eukaryotic communities colonizing polyethylene and polystyrene microplastics in brackish environments.
• To compare MP-associated eukaryotic communities with those in the surrounding water and on natural surfaces (wood).
• To understand the complexity and potential ecological implications of eukaryotic biofilms on microplastics.

Main Methods:

• Exposure experiments were conducted in the coastal Baltic Sea, an in-flowing river, and a WWTP.
• High-throughput 18S rRNA gene sequencing was used to identify eukaryotic taxa on MPs, surrounding water, and wood.
• Community composition was analyzed, and co-occurrence networks were constructed to explore microbial interactions.

Main Results:

• Over 500 eukaryotic taxa were identified on MPs, primarily Alveolata, Metazoa, and Chloroplastida.
• Eukaryotic community composition on MPs differed significantly from wood and surrounding water, exhibiting lower diversity.
• The potentially harmful dinoflagellate Pfiesteria was found to be enriched on MPs.

Conclusions:

• Microplastic biofilms in brackish environments harbor complex eukaryotic communities distinct from natural substrates.
• These MP-associated eukaryotic communities may influence microbial activities and alter aquatic ecosystem functions.
• This study provides the first comprehensive report on total eukaryotic communities on MPs in brackish settings.