gray whale forages off coast


By Sean Nealon, Oregon State University news editor

A study partly funded by Oregon Sea Grant found that each day, reproductive female gray whales off Oregon consume millions of microparticles, which include microplastics and other human-sourced materials such as fibers from clothing.

“It’s a wake-up call,” said Leigh Torres, a marine mammals specialist with Oregon Sea Grant and a co-author of the study, which was published in the journal Frontiers in Marine Science.

The researchers collected three species of zooplankton, an important food for gray whales, in nearshore waters off Newport, Oregon, between June and October from 2017 to 2019. They analyzed 26 zooplankton samples and found microparticles in all of them. A total of 418 suspected microparticles were identified, with fibers accounting for more than half of the microparticles in each of the three species of zooplankton. Anthropogenic debris (defined as human-generated but not clearly plastic) made up over half of the particles in each of the species.

Researchers then combined that data with known estimates of energetic requirements for lactating and pregnant gray whales to quantify how many zooplankton and microparticles they consume in a day. Lactating and pregnant gray whales were used because they’re the only gray whale demographic with information on daily energetic requirements.

Researchers concluded that, depending on the species of zooplankton, lactating gray whales consume a minimum of 6.45 million microparticles a day (eating only Neomysis rayii zooplankton) and a maximum of 14.3 million (eating only Atylus tridens). They estimated that pregnant gray whales consume at least 9.55 million microparticles daily (eating only N. rayii) and, at most, 21.2 million (eating only A. tridens).

“These are quite scary numbers. I think they should raise concern for people who care about the marine environment or about their own environment and exposure to microplastics,” Torres said.

Torres noted that the microparticle consumption estimates are likely conservative because they only account for what the whales consume from zooplankton. Gray whales likely ingest more microparticles directly from the water and seafloor sediment because they are filter feeders that engulf large amounts of water while consuming prey. They also use suction feeding to obtain prey from the seafloor, where heavier and larger microparticles sink and accumulate.

Analysis of poop samples provided a window into what kind of microparticles these gray whales were digesting. The researchers analyzed five poop samples from four whales and found microparticles in all of them, for a total of 37 particles. Similar to the zooplankton findings, the majority were fiber.

The researchers also found that the microparticles in the poop were significantly larger than those in the zooplankton, leading them to believe the larger particles came from the water or sediment, not the prey, which are too small to consume these larger particles.

The findings concern Torres. “These whales are already stressed out with boats driving around all the time and the risk of getting hit by one of those boats,” she said. “They might also have less prey around because of changes in the environment, like less kelp. And now the quality of the prey might be poor because of these high microplastic loads.”

The quality of prey is a topic that interests Torres. She and Susanne Brander, an ecotoxicologist at Oregon State University and a co-author of the study, are now looking at how microfibers affect zooplankton.