Researchers probe orca poop for microplastics

by NOAA Fisheries 29 May 2020 10:25 UTC

NOAA researchers collecting fecal samples. Photo taken under federal research permit © NWFSC

You might worry about your toddler chewing on a plastic toy with toxic chemicals. Some orca researchers are beginning to worry about whales ingesting a gut full of microplastics, and what that might mean for their health.

Microplastics are everywhere. Millions of tons of plastic enter our oceans annually, and much of it breaks into tiny pieces. Microplastics are plastic particles five millimeters (about two-tenths of an inch) or smaller. They represent 92 percent of plastic pieces polluting the oceans' surface waters. Researchers have found microplastics in all major seas and oceans. They've also found them in the intestinal tracts of organisms at all levels of the ocean food chain, from zooplankton to fish to marine mammals.

Some scientists are concerned that microplastics and their toxic effects are bioaccumulating in killer whales, the oceans' top predators. Endangered Southern Resident killer whales spend much of their summers in Puget Sound and the Salish Sea. Chemical contamination from pollution, particularly in young whales, is one of three primary threats to their population. Could microplastics be part of the problem?

A team of scientists with NOAA Fisheries' Northwest Fisheries Science Center (Center) and the University of Washington have started an investigation. They are looking at what microplastics the Southern Residents are ingesting, at what scale, and whether the whales are being exposed to toxic chemicals associated with microplastics.

An orca fecal sample. - photo © NWFSC

Exploring the "Poop Archive"

For this pilot study, Center Research Geneticist Kim Parsons and her colleagues are finding and classifying microplastics in killer whale feces. The scientists are using their "poop archive." The archive holds hundreds of killer whale fecal samples collected between 2006 and 2018, mostly from Southern Residents. They're stored in a lab at negative 80 degrees Celsius. "We have a lot of poop sitting in the freezer, ready for more analysis," says Parsons.

Whale researchers with the Center collected the fecal samples. They were out following the Southern Resident whales (at a safe distance so as not to disturb them) to gather the remains of salmon that the whales feast on. The researchers were collecting scraps of fish to learn more about the whales' prey. But if they saw or smelled orca poop—stinky, with a hint of rotting fish—they would scoop that up as well in their long-handled nets. The fecal samples have proved valuable for an array of studies. They help with everything from genetic analyses of the whales and their prey fish, to examining the killer whale gut biome, to new areas like microplastics.

For the microplastics pilot study, the scientists dried out a subset of the largest fecal samples in a lab oven for up to 48 hours. They removed the remaining biological matter with hydrogen peroxide, and then began to isolate and identify what was left—bits of plastic. Parsons and her NOAA Fisheries colleagues collaborated with researchers in Materials Science and Engineering at the University of Washington. They used an ultra-high-powered Raman microscope to classify the microplastics by polymer type.

Parsons explains that they won't be able to determine exactly where each piece of microplastic came from. It could be a plastic bag or water bottle, a fiber from a fleece jacket run through a washing machine, or a fishing net. "But we do know which typical human products are associated with each polymer type that we're identifying," she says.

So far the researchers have found a lot of fibers and a variety of very small microplastic particles. Final lab results later this year will give a first indication of which broad categories of plastics are most prevalent in the whales' digestive system.

How do microplastics end up in killer whale feces?

Microplastics can be found in all major seas and oceans. - photo © NOAA Ocean Service

"There are two ways that the whales could ingest microplastics," says Kim Parsons, Research Geneticist with NOAA Fisheries' Northwest Fisheries Science Center. "They could incidentally swallow particles in sea water while eating fish, or they could ingest salmon that are themselves contaminated with microplastic particles."

She suspects that most of the microplastics in orca poop are coming from the whales' prey. The particles are traveling up the food chain from gut to gut, from herring to salmon to orca.

But why does it matter for orcas if their guts are full of microplastic particles and fibers?

How ingestion of microplastics affects marine mammals is both poorly understood and scientifically controversial. So the answer is, we don't know yet, but scientists are concerned for the health of organisms at all levels of the marine food chain.

You might own a reusable water bottle advertised as being free of toxic chemical additives like bisphenol A, or BPA. Many chemicals found in microplastics are pollutants, such as polyethylene, polypropylene, phthalates, and BPA and its substitutes. Some of these chemicals are known endocrine disruptors, which means that the chemicals can disrupt an animal's natural hormones. The chemicals may affect reproduction, growth and development, and ultimately population viability. When microplastics are moving through the whales' digestive tract, the harmful chemicals could leach into their bodies.

Some scientists hypothesize that microplastics may also deliver harmful chemicals or even viruses as "hitchhikers." Chemical pollutants enter the nearshore waters and ocean through stormwater run-off, wastewater effluent, and other pathways. Many pollutants, such as flame retardants, will readily bind to microplastic particles in seawater. These harmful chemicals could then "hitchhike" their way into the bodies of marine organisms.

So Parsons and her colleagues are also examining the whales' fecal samples for xenoestrogens. That is another name for the chemicals that disrupt an animal's hormones by mimicking natural estrogens. The researchers are looking for correlations between the types of microplastics that they find in the feces and the presence and types of estrogenic compounds.

Plastics found in the ocean. - photo © NOAA Fisheries

Exposure to endocrine disruptors would be particularly concerning for the Southern Residents. The population currently has a low birth rate for calves and may be experiencing high levels of miscarriage. Just like for humans, endocrine disruptors may cause the most problems for young whales.

Parsons hopes this pilot study will lead to more research on the effects of microplastics on marine predators and their prey. She wants to look more closely at microplastics in the salmon that the killer whales eat, and in the smaller fish that salmon eat, such as herring. And, whether or not microplastics accumulate in other parts of the animals' bodies, such as fish gills.

What can you do?

NOAA has one main message for what you can do to prevent plastics from entering the ocean: Reduce, Reuse, Recycle!

When Parsons began to realize the enormity of the volume of plastics entering our oceans, she started making changes in her own life. "When I began learning about microparticles and microfibers, I even started avoiding polar fleece clothing, which is pretty hard as a Seattlite," she says.

You can try her changes too: