Ever since the creation of synthetic plastic in 1869, plastic has become an inescapable part of life on Earth. From large, bulky items to the invisible-to-the-naked-eye pieces, plastic circulates in the air, water, and even our blood and lungs. Today we are focusing on a new study that looked at microplastics in baleen whales off Auckland, Aotearoa – New Zealand. Researchers found that the local population of whales in Auckland’s harbor consumes about 3 million microplastics per day and that these microplastics likely come directly from the polluted city.
Plastic, plastic everywhere!
Large pieces of plastic enter the environment from multiple sources, whether landfills or large cities. Urban areas can heavily pollute watersheds and contaminate the oceans. The number of plastics released into the water can increase during heavy rainfall events. Once they enter the environment, large pieces of plastic break down into smaller pieces. This repeated process can eventually transform a plastic bottle into thousands of tiny particles called microplastics (pieces smaller than 5mm or 0.2in).
But this is not the only source of microplastics. Tiny plastic fibers from our clothes can enter the environment through our sewage pipes. Fishing lines and nets can also break away during fishing trips, adding another source of plastic pollution. The sad truth is that plastics are now everywhere on our planet. In the words of Sylvia Earle, “we have plasticized the Earth”. As a result, microplastics have contaminated every environment studied, marine or terrestrial. And these microplastics can harm large filter-feeding whales.
A whale’s tale
Baleen whales are particularly good at telling the story of microplastics in the ocean. Indeed, baleen whales are filter-feeders. They take large gulps of water filled with their favorite prey, then close their mouths, and push the excess water through their ‘baleen filters’ with their tongues. Thus, microplastics can enter their digestive tract through accidental ingestion or the ingestion of contaminated prey.
Scientists examined Bryde’s and Sei whales’ poop samples over five years in Auckland’s Hauraki Gulf (Tīkapa Moana — Te Moananui-ā-Toi). The new study reported that the types of microplastics found in the whales’ poop are similar to those found in Auckland beach sediments and waters. These findings thus depict the potential transport of microplastics from terrestrial to marine environments. Like so many before it, this study highlights the need to act now to limit plastic pollution. Scientists even found a 26 mm (1in) piece of plastic in whale poop, meaning it made its way through the whale’s guts. Ouch!
These local populations of whales suffer from constant exposure to microplastics from polluted runoff outside of New Zealand’s largest city. Interestingly, migratory populations swim across ocean gyres, often littered with pollution of all kinds, to get to their final destinations. Future studies could thus look at differences in the composition of microplastics between resident and migratory populations to understand the fate of plastics once they reach the oceans.
You are what you eat
DNA analyses determined that whales off Auckland consumed mainly krill (tiny shrimp-like individuals). By counting the relative number of microplastics in the water, and whale poop, researchers determined that microplastic exposure from the ocean water alone would not explain the high concentration measured in their feces. Instead, they found a significant microplastic contribution from the whales’ diet.
The average size of the microplastic particles sampled in the poop was smaller than the size of their favorite prey, krill. This information led researchers to believe microplastic pieces were first eaten by krill before ending up in the whales. This makes us reflect on how much microplastics we ingest by eating contaminated food, like fish and seafood.
Is there a solution to the plastic problem?
To begin, we need to stop using single-use plastics. If discontinuation is not possible, there must be a transition to sustainably biodegradable bioplastics. Next, we need to pressure our governments to do better. There need to be strong resolutions and regulations regarding the use of plastics and the chemicals used to make them. We thus need to hold companies accountable for our continued exposure and their lack of accountability in solving the plastic pollution crisis.
Citizen science at work
Interestingly, some samples of whale poop were collected in collaboration with a local whale watching company. This collaboration led to a larger pool of samples than individual scientists would have been able to collect on their own, from a broader range of days and locations. In addition, it allowed whale-watching customers to understand how their decisions impact the ocean, even at a microscopic level.
Sources and further reading:
- Zantis, L.J., Bosker, T., Lawler, F., Nelms, S.E., O’Rorke, R., Constantine, R., Sewell, M. and Carroll, E.L., 2022. Assessing microplastic exposure of large marine filter-feeders. Science of the Total Environment, 818, p.151815.
- I highly recommend listening to this podcast episode of Speak Up For Ocean Blue.
- Also, check out this episode of Last Week Tonight with John Oliver.
Brianna has a background in marine biology and currently works as a live-aboard deckhand/educator at the Los Angeles Maritime Institute (LAMI). Her research interests include ocean conservation, specifically in the high seas and polar regions, and identifying marine mammal vocalizations in the global soundscape. She is passionate about music and can’t write without coffee.