How do microplastics enter the food chain?

Plastic is everywhere. Its in the air, the water, and the everyday items we use. Most shockingly; its even in us. According to one major study, humans ingest about 5 grams of microplastic each week. its no wonder the contamination of microplastics has reached this far; after all, we rely on plastic for nearly everything.

So, how do microplastics get in our body? Or rather, how does it enter the food chain in the first place and what are its impacts?

Keywords:

Trophic transfer

Trophic levels

Microplastics

Food chain

Predators

Consumers

What are microplastics?

Microplastics are small pieces of plastic that are smaller than 5mm in size. Microplastics come from a variety of sources such as larger broken down plastic pieces and mostly microbeads.

Microbeads are synthetic beads used in skincare and cosmetics that are intentionally made to be small. Although cheap and efficient, microbeads quickly entered waterways through drains, polluting oceans and other large bodies of waters. Furthermore, these beads were also mistaken by birds to be seeds and consumed by many other different organisms who saw it as food.

On December 28, 2015, President Obama signed the Microbead-Free Waters Act of 2015, banning the use of plastic microbeads in skincare and cosmetics. However, plastic still plagues the waters with other sources such as city dust, marine coatings, plastic bags, and ecetera.

How microplastics enter the food chain

A Greenpeace Philippines display after a sperm whale was found in Indonesia with 1000 plastic piece in its stomach.

Microplastic first enters the ocean (where the majority of plastic waste ends up) mainly through drains, wind flow, and littering. If in large amounts, the plastic breaks down over time into small pieces and is consumed by fish, oysters, and other marine organisms due to their consistent uptake of the contaminated water.

Figure 1: diagram of trophic transfer in marine ecosystems.

As represented in the diagram above, microplastic is first directly ingested by plankton and microscopic sea life (e.g. zooplankton and bivalves) as they are the primary consumers nearing the bottom of the food chain that are the base nutrition for larger species such as fish and crabs that are then eaten by larger predators.

In today’s environment, most if not all organisms are already carrying small amounts of microplastics in their body. When these organisms are consumed, the consumer also ingests these microplastics in a process called the ‘trophic transfer‘ of microplastics: a never-ending cycle in which contaminants are passed through the entire food web from one trophic level to another.

Although microplastics can be excreted after digestion (ex. feces), they can also travel to different parts of the body. One study from researchers in the Rochman lab sampling 7 species of sportfish found that microplastics were widespread in the fillets and livers of all seven species.

What are the impacts of microplastic?

Microplastics have several health-related impacts on organisms such as oxidative stress, DNA damage, organ dysfunction, metabolic disorder, immune response, and neurotoxicity as well as reproductive and developmental toxicity. In addition, medical research and evidence suggests that many chronic diseases may be related to microplastics exposure. This not only poses a risk in animals but also in humans as we are the top predator of the food chain and not only consume organisms with microplastics but interact with plastics in our everyday lives.

Share this!