Spatiotemporal variation in macroplastic abundances along a subtropical Austral river system

Area of Science:

• Environmental Science
• Ecology
• Riverine Ecosystems

Background:

• Plastic pollution is a global environmental threat, particularly in aquatic ecosystems.
• Limited data exists on macroplastic pollution in African subtropical rivers, hindering effective management.
• Anthropogenic activities contribute significantly to plastic debris accumulation in rivers.

Purpose of the Study:

• To quantify and compare macroplastic abundance and variation across sites and seasons in the Mvudi River, South Africa.
• To identify dominant types and polymers of macroplastic debris in the studied river system.
• To establish a baseline for understanding seasonal dynamics of riverine plastic pollution.

Main Methods:

• Field sampling at four distinct river sites over four seasons.
• Quantification of macroplastic debris abundance and diversity.
• Identification of macroplastic types (e.g., bags, film) and polymer composition (e.g., polypropylene).

Main Results:

• No significant difference in macroplastic abundance across sites and seasons, indicating widespread pollution.
• Decreased macroplastic diversity along river sites.
• Highest macroplastic collection during winter, lowest during autumn.
• Greater macroplastic accumulation on shorelines compared to the river mainstream.
• Plastic bags and film constituted over 57.8% of debris; polypropylene was the most abundant polymer (>25.3%).

Conclusions:

• Macroplastic pollution is pervasive across sites and seasons in the Mvudi River.
• Shoreline accumulation and specific plastic types (bags, film) and polymers (polypropylene) are key characteristics of pollution in this system.
• The findings provide crucial baseline data for developing targeted management strategies for subtropical riverine plastic pollution.