Profiling microplastics in a forgotten river system in Southern Africa

Area of Science:

• Environmental Science
• Ecotoxicology
• Riverine Ecology

Background:

• Microplastic pollution is a global concern impacting aquatic ecosystems.
• Understanding microplastic distribution dynamics in rivers is crucial for effective management.
• Limited data exists on seasonal microplastic distribution in South African transboundary rivers.

Purpose of the Study:

• To characterize microplastic profiles in the Nyl, Mogalakwena, and Limpopo Rivers.
• To identify environmental factors driving microplastic distribution across seasons.
• To assess microplastic bioavailability in riverine benthic macroinvertebrates.

Main Methods:

• Seasonal sampling of water and sediment for microplastic analysis.
• Quantification and characterization of microplastic polymers.
• Correlation analysis between environmental factors (flow) and microplastic abundance/distribution.
• Analysis of microplastics in benthic macroinvertebrates.

Main Results:

• Microplastic abundance in water and sediment was significantly higher during low-flow seasons.
• High-flow seasons showed decreased microplastic concentrations but more homogenous distribution.
• Microplastics were found in benthic macroinvertebrates, indicating bioavailability.
• Significant differences in microplastic polymer types were observed between water and sediment samples across seasons.

Conclusions:

• River flow is a key determinant of microplastic distribution and concentration.
• Low flow can lead to microplastic accumulation, while high flow promotes wider dispersal.
• Microplastic bioavailability to aquatic organisms is confirmed in this system.
• This study provides the first baseline data for this critical transboundary river system.