Plastic pollution has infiltrated every ecosystem in every ocean on the planet, but perhaps the most iconic organisms impacted are the whales. The problem is monumental. For example, consider the blue whale. Our most optimistic estimates put the global blue whale population size at about 25,000 individuals (down 89 percent since before commercial whaling began in 1911). Based on recent estimates, an amount of plastic waste equivalent to about 3.5 times the weight of the entire blue whale population is put into the ocean every year. That staggering figure alone is enough to make one feel, well, blue, but the devastating impact is underscored by the now-familiar images of deceased whales—their guts bursting with plastic bags or completely entangled in derelict or discarded plastic fishing gear.

Plastic waste also poses insidious, less obvious threats to whales in the form of microplastics. As it is exposed to the sun and elements, plastic waste is broken down into microplastics that are less than 5mm (roughly one-fifth of an inch). Even smaller pieces, called nanoplastics (less than 1µm, one “micrometer”), are roughly 400 times smaller than the period at the end of this sentence. At such small sizes it can be difficult to imagine that the ocean giants have anything to fear from these plastics, but scientists are concerned about health threats when whales ingest them.

As a member of the Nowacek Lab at the Duke University Marine Lab I study the movement of tiny plastic pieces throughout the bodies of whales and other marine mammals. A big concern is that once ingested, the micro/nanoplastics will migrate from the digestive tract to other parts of the body, a biological process called translocation. Most marine mammals are at risk of exposure. Microplastics are ubiquitous across the oceans, in low concentrations in places like the Southern Ocean surrounding Antarctica, but also in high concentrations in many others, like the Mediterranean Sea. Microplastics can leach toxic chemicals and even soak up other pollutants in the environment, making them potentially even more harmful when swallowed. Filter feeding whales like humpbacks, for example, take in enormous volumes of water when they hunt prey like krill. They push the water out of their mouths, straining krill through fine, comb-like plates made of a fibrous material called baleen. Some residual water containing microplastic particles may be ingested incidentally with the krill, not to mention the prey themselves could contain plastics they have eaten.

Consequences of an Invisible Threat

What happens to microplastics once animals ingest them and how they impact whales is still a bit of a mystery. Scientists call these “sub-lethal effects,” or more plainly, effects that do not kill but still cause harm. Their tiny size means it is plausible for microplastics to hitch a ride in the circulatory system to other organs, one of which is unique to marine mammals: blubber. Blubber is composed of fatty tissues and is critical for storing energy, warmth, and even swimming efficiency. Plastics are both hydrophobic and lipophilic meaning if they have their way, they prefer to avoid water and seek fatty environments. That makes fatty whale blubber a prime destination for the tiny plastic bits to travel. I suspect that once in the blubber the micro/nanoplastics and their associated toxicants negatively impact the ability of various hormones to efficiently convert blubber into energy.

Studying the impact of microplastic on whale blubber is tricky. First, we need blubber, however marine mammals are highly protected species, particularly in the United States. Working with them requires extensive permitting in order to shield these animals from unnecessary harm. Thus, the majority of blubber samples come from animals that have died of natural causes. A smaller subset is collected from live animals at sea, as pictured in the lead photo; a minimally invasive dart collects a pea-sized biopsy of blubber. In some cases, blubber samples from animals lawfully harvested by native subsistence hunters are examined. This set of samples is particularly exciting to look at because it will allow us to answer questions about food security for native peoples as well as the well-being of the animals.

Any microplastics present will be very tiny, which requires special instruments to see: a raman spectrometer or a scanning electron microscope, which adds to the challenges of collecting data in the field. Despite these obstacles, researchers have managed to show that ingested microplastics move throughout the bodies of other species, some which are of commercial importance for human consumption; the methods used are encouraging for my research on whale blubber.

Greatest Concerns & Paths Forward

Marine scientists and ocean protection groups see microplastic pollution as a serious emerging concern for whales, but entanglement in and ingestion of large plastic waste (along with ship strikes, habitat loss, and climate change) remain more immediate threats. Imagine walking around with weights tied to your ankles. Whales struggle to get untangled from large nets and they end up dragging this weight along with them, expending extra energy they need to migrate and raise their young. An increasingly common tragedy is when whales become so overburdened by the weight of the plastic debris they cannot surface to breathe, and drown. Ingestion of macroplastics can also lead to a whale’s death. For some toothed whales, like sperm whales  which eat squid, the appearance of plastic bags is sometimes mistaken for prey and consumed. Large pieces of plastic cannot pass through the digestive tract so they accumulate in the stomach, leading to a false sense of satiation. These whales get full off of literal junk food, leading to emaciation and eventually death.

The plastic pollution problem requires a holistic plan of action. Avoiding prepackaged foods and using reusable bags/ziplocks/cups/utensils/containers/hygiene products are great ways to reduce plastic pollution at the individual level. But curbing plastic pollution in the oceans (and on land) will require a serious reduction in commercial production, especially single-use items. Writing policymakers and plastic producers to express your encouragement for action could be a huge step in helping save the whales, and ourselves, from our trash.