Plastics Here, Plastics There, Plastics Everywhere

A Close Look at Microplastic Pollution in Coastal Habitats

This was eye-opening. I used to teach undergraduate and graduate students at different universities. We collected sand from a beach in the Great Barrier Reef for one of our labs at my PhD-granting university in Australia.

Using a binocular microscope, the students were asked to classify everything they found in the sample. There were small pieces of corals, tinny calcified unicellular organisms called foraminifera, shells, minerals… and microplastics—an absurd amount of microplastics.

Students quickly understood the implications. Microplastics are everywhere, from mountain peaks to the depths of the ocean. These tiny pieces of plastic, originating from sources like household products and industrial waste, have become a major environmental issue.

However, if microplastics are everywhere in the ocean, they are also in the fish and seafood we eat and the water we drink. We are basically consuming plastics day after day. See the short video from the National Oceanic and Atmospheric Administration (NOAA) below to learn more.

More importantly, microplastics pose a unique challenge for coastal ecosystems, such as seagrass beds and coral reefs.

Three recent studies, all published in 2024 by a team from the National University of Singapore (NUS), shed light on how these coastal habitats interact with microplastics and what that means for the future of marine health.

Seagrass beds, often called the “lungs of the sea,” are known for their ability to trap sediments and provide essential habitats for marine life. But when it comes to trapping microplastics, things aren’t as straightforward.

One of the studies, published in Marine Environmental Research, took a close look at seagrass beds in Singapore, focusing on areas like Chek Jawa and Changi Beach. Their goal was to figure out whether seagrass beds with dense vegetation trap more microplastics than areas without vegetation.

Surprisingly, the results challenged a long-held assumption.

The study found that seagrass beds in Singapore do not trap more microplastics than adjacent non-vegetated areas, regardless of the seagrass density.

One possible reason? The height of the vegetation. In Singapore, common seagrass species like Halophila ovalis and Halodule uninervis have short canopies, around 2–15 cm tall. In contrast, seagrass species in other parts of the world, like Enhalus acoroides, can grow up to 150 cm, providing a much larger surface for microplastics to settle on.

This discovery is important because it shows that not all seagrass beds are equally effective at trapping microplastics. The height of the plants seems to matter a lot, which could influence where microplastic pollution builds up in coastal areas.

It also means that simply having seagrass isn’t enough to guarantee protection against microplastic accumulation.

But what about coral reefs?

Another study published in Science of the Total Environment focused on coral reefs, which are known for their structural complexity and biodiversity.

This research looked specifically at the branching coral Pocillopora acuta, a common species in Singapore’s coral reefs. The team wanted to know how different shapes and structures of coral colonies affect their ability to trap microplastics.

The results were clear: corals with more compact branching morphologies trapped more microplastics than those with more open structures.

But why does this happen? Well, the tightly packed branches create areas of slower water flow, causing microplastics to settle and become trapped. Interestingly, the study found that surface roughness — caused by coral polyps and skeletons — didn’t have much impact on how well the corals trapped microplastics.

However, this raises an important concern. As climate change forces corals to adapt, more compact forms of branching corals are becoming common because they are better at withstanding environmental stressors like warmer temperatures and storms.

However, these compact corals are also more effective at trapping microplastics, putting them at greater risk of being polluted by these particles. Coral reefs, already under pressure from bleaching and ocean acidification, now face an added threat from microplastic accumulation. Remeber when we talked about coral bleaching?

It’s Time To Talk About Global Coral Bleaching

The fourth major global coral bleaching event is not just an environmental problem — it’s a human health and security problem.

But let’s look at the issue from a different perspective.

One of the biggest challenges in studying microplastics is preventing contamination during the sampling process. Many traditional sampling tools are made of plastic, which can inadvertently introduce more microplastics into the samples.

In response, the NUS research team developed plastic-free sampling equipment, which was detailed in their study published in Frontiers in Marine Science. This equipment was designed to eliminate the risk of plastic contamination during research.

By using tools made from non-plastic materials like metal and glass, the researchers were able to get cleaner, more accurate samples from Singapore’s coastal habitats. This step is essential for ensuring that future microplastic studies can produce reliable data free from contamination introduced during the collection process.

But why do microplastics matter?

The harm caused by microplastics is well-documented. They can be ingested by marine organisms, from the tiniest plankton to larger animals like fish and turtles, leading to blockages, malnutrition, and even death.

But more scary, microplastics also act as sponges for harmful chemicals, which can then enter the food chain when these particles are consumed by marine life.

For coastal ecosystems like coral reefs and seagrass beds, microplastics are particularly dangerous. These habitats serve as crucial nurseries for many species of fish and invertebrates, meaning that the accumulation of microplastics in these areas can have far-reaching effects on marine biodiversity and ecosystem health.

Overall, these studies provide valuable insights into the relationship between coastal habitats and microplastic pollution.

Depending on their height, seagrass beds may not be as effective at trapping microplastics as once thought. Corals, particularly those with compact branching structures, are highly effective microplastic traps, which, unfortunately, increases their exposure to pollution. However, thanks to innovations in plastic-free sampling tools, researchers are now better equipped to study these dynamics without contaminating their samples.

Moving forward, it’s clear that reducing the amount of plastic entering the oceans is critical. While efforts like beach cleanups and improved waste management systems are essential, understanding how microplastics move through and accumulate in marine ecosystems is equally important.

Only then can we take the necessary steps to protect our coastal habitats from this growing threat? Or do we really want to normalize students finding microplastics from pristine beaches in coral reef paradises?