Microplastics alter feeding selectivity and faecal density in the copepod, Calanus helgolandicus

Area of Science:

• Marine Biology
• Environmental Science
• Ecotoxicology

Background:

• Microplastics are pervasive marine pollutants impacting marine ecosystems.
• Copepods are crucial to marine food webs and nutrient cycling.
• The effects of microplastic ingestion on copepod feeding and faecal pellet characteristics are not fully understood.

Purpose of the Study:

• To investigate how microplastic size, shape, and density affect the feeding preferences of the copepod Calanus helgolandicus.
• To determine the impact of microplastic ingestion on the sinking rates of copepod faecal pellets.

Main Methods:

• Controlled laboratory exposure studies using Calanus helgolandicus.
• Inclusion of algal prey and microplastics (nylon fibres and fragments, polyethylene, polyethylene terephthalate) of varying sizes and shapes.
• Measurement of algal ingestion rates and faecal pellet sinking velocities at a concentration of 100 microplastics/mL.

Main Results:

• Prey selection was influenced by microplastic characteristics; nylon fibres decreased chain-forming algae ingestion by 6%, while nylon fragments reduced unicellular algae ingestion by 8%.
• Microplastic ingestion altered faecal pellet sinking rates: low-density polyethylene caused slower sinking, whereas high-density polyethylene terephthalate increased sinking rates.

Conclusions:

• Calanus helgolandicus demonstrates altered feeding behavior, potentially avoiding algae similar in size and shape to encountered microplastics.
• Microplastic ingestion modifies faecal pellet density and sinking rates, with implications for carbon cycling and trophic transfer in marine environments.