Microplastics encapsulation in aragonite: efficiency, detection and insight into potential environmental impacts.

Area of Science:

• Marine Biology
• Environmental Science
• Materials Science

Background:

• Plastic pollution, particularly microplastics, poses a threat to aquatic ecosystems.
• Microplastics can be incorporated into the calcium carbonate skeletons of marine organisms like corals, mollusks, and foraminifera.
• The impact of microplastics on aragonite precipitation and the mechanical properties of coral skeletons is largely unknown.

Purpose of the Study:

• To investigate the encapsulation of polystyrene (PS) and polyethylene (PE) microplastics into precipitated aragonite.
• To determine the effect of dissolved organic matter (humic acid) on microplastic encapsulation into aragonite.
• To assess how microplastic encapsulation influences the mechanical properties of aragonite.

Main Methods:

• Aragonite precipitation experiments were conducted in artificial seawater.
• Polystyrene and polyethylene microspheres, both untreated and humic acid-treated, were introduced during aragonite precipitation.
• Mechanical properties (hardness and indentation modulus) of the resulting aragonite samples were measured.

Main Results:

• Encapsulation efficiency was higher for polyethylene (PE) and humic acid-treated PE (PE-HA) microspheres compared to polystyrene (PS) and humic acid-treated PS (PS-HA) microspheres.
• Microplastic encapsulation altered the mechanical properties of aragonite.
• A decrease in hardness and indentation modulus was observed, with the most significant reduction occurring with PE-HA microspheres.

Conclusions:

• Microplastic incorporation into aragonite can negatively affect its mechanical integrity.
• Dissolved organic matter can influence the extent of microplastic encapsulation.
• These findings raise concerns for the structural stability of coral skeletons and other calcifying marine organisms facing microplastic pollution.