Detecting Ocean Microplastics: Scientific Approaches Explored

The ocean conceals many invisible wonders beneath its surface—unique species, intricate ecosystems, and, unfortunately, vast amounts of litter.

According to the United Nations, roughly 52 million metric tons of plastic waste flow into the oceans annually, generating an estimated 24 trillion microplastic particles.

Microplastics—plastic fragments smaller than five millimeters—are present throughout the water column, from the surface to the deep sea, and their ecological impacts remain an active area of research.

Key questions remain: How do these particles enter the marine environment? Which technologies can detect them? And what effects do they have on ocean life?

To address these questions, Euronews Tech Talks visited the Flanders Marine Institute (VLIZ) in Ostend, Belgium. There, a team led by senior researcher Ana Catarino studies marine microplastics, gathering samples directly from the North Sea.

Marine microplastics pollution, climate change and risks

Plastics reach the ocean through various pathways, including lost fishing gear, inadequately managed waste, and other sources.

Marine microplastics fall into two main categories: primary and secondary microplastics.

Primary microplastics include manufactured items such as nurdles—small plastic pellets used in industry—whereas secondary microplastics result from the breakdown of larger plastic debris by wave action, wind, and UV radiation.

The prevalence of microplastic pollution is closely linked to climate change.

“Increased sunny days, greater UV exposure, heat waves, and temperature shifts can accelerate the degradation of stranded plastics,” Catarino noted.

The effects of microplastics on marine life are also intertwined with climate change. While ingesting microplastics alone may not harm an organism significantly, however, when a species is already stressed by rising sea temperatures, the combined impacts can become cumulative within the organism, Catarino explained.

Methods to identify microplastics

Detecting and quantifying marine microplastics is challenging because of their tiny size, irregular shapes, and variable colors.

Nevertheless, detection is feasible, and VLIZ postdoctoral researcher Nelle Meyers has developed a semi‑automated approach for identification.

The method entails collecting seawater samples with a net, removing organic matter, staining the filtrate with Nile Red, and examining it under a microscope. Fluorescence analysis is performed, and the results are processed by two automated algorithms that determine whether each particle is a microplastic and, if so, its polymer type.

“We aimed to automate the workflow to save time,” Meyers said. “We wrote code that analyzes an uploaded image automatically,” she added.

Combining this semi‑automated step with a widely available fluorescence microscope makes the approach both cost‑effective and time‑efficient, according to Meyers.

However, the technique has limitations: it does not provide detailed chemical composition and can identify only specific polymer types.

Microplastics’ impact on marine species

Just as larger plastic debris is ingested by marine organisms, microplastics can also be consumed by tiny creatures such as plankton.

“Microplastics can block the digestive tracts of these small organisms, preventing them from absorbing nutrients or feeding properly,” Catarino explained.

“This is concerning because impaired feeding can hinder reproduction and reduce population viability,” she added.

The specific impacts vary depending on the species, the microplastic type, and concurrent stressors such as rising sea temperatures, ocean acidification, and other environmental factors.

“Often, it is not a single factor but the cumulative effect of multiple stressors that harms the organisms,” Catarino told Euronews Next.

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