Polystyrene microplastics at environmentally realistic concentrations exacerbate diatom blooms caused by phosphorus...

Area of Science:

• Marine Biology
• Environmental Science
• Ecotoxicology

Background:

• Algal blooms are frequent coastal events driven by eutrophication, primarily phosphorus pollution.
• Microplastics (MPs) are pervasive pollutants that may affect algal growth, but their combined effects with phosphorus are unclear.

Purpose of the Study:

• To investigate the combined effects of microplastics and phosphorus pollution on diatom growth and physiology.
• To understand the mechanisms by which microplastics influence phosphorus uptake and algal bloom formation.

Main Methods:

• Diatoms were exposed to environmentally relevant concentrations of polystyrene microplastics (PS MPs) and phosphorus (P).
• Cell density, cell-associated organic phosphorus, and extracellular polymeric substance phosphorus (EPS-P) were measured.
• Gene expression related to phosphorus transport, photosynthesis, and cell division was analyzed.
• Diatom ultrastructure and photosynthetic activity were assessed.

Main Results:

• Polystyrene MPs alone did not affect diatoms, but at 10 μg/L with P pollution, they increased cell-associated organic phosphorus by 11% and cell density by 13%.
• MPs accelerated P transport into cells, reducing EPS-P by 41% and enhancing P availability.
• Diatoms exposed to P+MPs showed denser thylakoid membranes, higher photosynthetic activity, and upregulated genes involved in key metabolic processes.

Conclusions:

• Environmentally relevant concentrations of PS MPs exacerbate P-driven diatom growth, contributing to coastal algal blooms.
• Microplastic pollution should be integrated into models and warnings for coastal diatom blooms.