Microplastic accumulation in deep-sea sediments from the Rockall Trough

Area of Science:

• Marine Science
• Environmental Science
• Geochemistry

Background:

• Microplastics are ubiquitous in marine environments, but their historical prevalence and distribution remain understudied.
• Understanding long-term microplastic trends is crucial for assessing environmental risks and transport mechanisms.

Purpose of the Study:

• To quantify the temporal distribution and polymer types of microplastics in deep-sea sediments.
• To investigate the historical presence of microplastics in the North Atlantic Ocean.

Main Methods:

• Sediment cores were collected from over 2000m depth in the Rockall Trough.
• Lead-210 (210Pb) dating was used to establish sediment age.
• Microplastic abundance, polymer types, and sediment porosity were analyzed.

Main Results:

• Microplastics were detected throughout the 10cm sediment cores, with abundance decreasing in older layers.
• Polymer diversity increased with sediment age.
• Microplastic presence extended beyond the ~150-year sediment layer dated by 210Pb.
• Microplastic abundance correlated significantly with sediment porosity, suggesting pore water transport.

Conclusions:

• Microplastic pollution in the deep sea is a long-standing issue, predating widespread modern plastic production.
• Vertical redistribution mechanisms like sediment reworking and interstitial transport via pore waters influence microplastic distribution.
• Deep-sea sediments act as a long-term sink for microplastics, with implications for marine ecosystem health.