Macroalgal morphology mediates microplastic accumulation on thallus and in sediments

Area of Science:

• Environmental Science
• Marine Biology
• Ecotoxicology

Background:

• Microplastic (MP) accumulation is critical for understanding environmental fate.
• Limited data exists on short-term MP accumulation on macrophytes.
• Macrophytes may facilitate MP deposition by reducing water flow.

Purpose of the Study:

• To investigate microplastic accumulation on different macroalgal morphologies.
• To assess the role of macroalgae in MP deposition in sediments.
• To determine if macroalgal morphology influences microplastic retention.

Main Methods:

• Field observations of macroalgae and associated sediments during Hong Kong's dry season.
• Quantification of microplastics per biomass, surface area, and interstitial volume on algae.
• Analysis of microplastic abundance in sediments under and near macroalgal mats.

Main Results:

• Filamentous algae retained 2.35 times more MPs per biomass than non-filamentous algae.
• Fibers were the dominant MP type, retained similarly across algal morphologies.
• Sediments under vegetated areas had 3.39 times more MPs than unvegetated areas, with filamentous algae sites showing higher retention.

Conclusions:

• Macroalgal systems are identified as short-term microplastic accumulation hotspots.
• Algal morphology, especially filamentous structure, influences MP retention.
• Seasonal dynamics of macrophytes likely drive temporal MP accumulation patterns in coastal environments.