Microplastics reduce microalgal biomass by decreasing single-cell weight: The barrier towards implementation at scale

Area of Science:

• Environmental Science
• Ecotoxicology
• Biotechnology

Background:

• Microplastics (MPs) pose a pervasive environmental threat, particularly in aquatic ecosystems.
• Water quality is critical for efficient biomass production in microalgal industries.

Purpose of the Study:

• To investigate the chronic effects of polystyrene (PS) and polyethylene (PE) microplastics on the biomass yield of industrially relevant microalgae.
• To assess the impact of microplastic contamination on microalgal cell density, size, and biomass production.

Main Methods:

• Three microalgal species (Tetraselmis suecica, Scenedesmus armatus, Nannochloropsis gaditana) were exposed to PS- and PE-MPs (10-20 μm) at concentrations of 5 and 10 mg/L for four days.
• Chronic effects were evaluated over 27 days, monitoring cell density, biomass yield, single-cell weight, and cell size.
• Computational modeling was employed to evaluate concentration-dependent impacts and systematic risks.

Main Results:

• Microplastics induced varied cell density responses: T. suecica decreased, S. armatus showed no change, and N. gaditana increased.
• All species exhibited significant decreases in biomass production (up to 52%), primarily due to reduced single-cell weight and/or smaller cell size.
• S. armatus exposed to PS-MPs and N. gaditana exposed to PE-MPs were most affected.
• Despite cell density normalization after chronic exposure, biomass production remained reduced.

Conclusions:

• Microplastic contamination negatively impacts microalgal biomass production in a concentration-dependent manner.
• The findings highlight significant risks to microalgal-based industries and emphasize the need for MP containment strategies.
• Computational models aid in assessing MP risks and guiding mitigation efforts in microalgae cultivation.