Newswise — CORVALLIS, Ore. – According to researchers from Oregon State University, gray whales feeding off the Oregon Coast ingest approximately 21 million microparticles each day, and this discovery was partially informed by analyzing whale excrement.

The microparticles consist of microplastics and other human-derived materials, including fibers from clothing. The findings, recently published in the journal Frontiers in Marine Science, are significant because the concentration of these particles is rapidly increasing and is expected to continue to do so in the coming decades, as stated by researchers Leigh Torres and Susanne Brander.

Microparticle pollution poses a threat to the well-being of gray whales, in addition to the challenges they face due to heightened boat traffic and depletion of their prey.

Leigh Torres, an associate professor at Oregon State and one of the paper's authors, expressed concern about these alarming figures. "I believe they should raise concerns among individuals who are passionate about the marine environment or concerned about their own exposure to microplastics," she said. "Gradually, we are all being exposed to more and more microplastics. It is now inevitable across all ecosystems, even right off the coast here in Oregon."

Susanne Brander, an associate professor and ecotoxicologist at Oregon State, and co-author of the study, emphasized the importance of curbing the release of microparticles due to their adverse effects on organisms and ecosystems. "This issue is gaining global momentum, and while some states, like California, have taken important measures," Brander explained, "more action needs to be taken, including here in Oregon, because this problem will persist for the foreseeable future."

The study focused on a specific subgroup of gray whales known as the Pacific Coast Feeding Group, consisting of around 230 individuals. These whales spend their winters in Baja California, Mexico, and migrate north to coastal habitats from northern California to southern British Columbia between June and November to forage for food.

Since 2015, Leigh Torres, leading the Geospatial Ecology of Marine Megafauna Laboratory at the OSU Marine Mammal Institute, and her team, including doctoral student Lisa Hildebrand, have utilized drones and other tools to study the health and behavior of this subgroup of gray whales off the Oregon Coast. As part of their research, they collect fecal samples from the gray whales.

For the current study, the researchers gathered zooplankton, a crucial food source for gray whales, as well as commercially and recreationally caught fish.

"We had previously determined the caloric content of various zooplankton species, so our next objective was to assess their microparticle concentrations to gain a more comprehensive understanding of the quality of these prey items," explained Hildebrand.

Brander, Hildebrand, and researchers from Brander's Ecotoxicology and Environmental Stress Lab examined the microparticle levels in 26 zooplankton samples obtained from areas where whales feed, and they discovered microparticles in all of them. A total of 418 suspected microparticles were identified, with fibers comprising over 50% of the findings.

Torres and Hildebrand combined this data with known estimates of energetic requirements for lactating and pregnant female gray whales to quantify the daily intake of zooplankton and microparticles. The analysis revealed that lactating and pregnant whales consume between 6.5 million and 21 million microparticles per day.

"It's alarming that whales are ingesting such a significant amount of microplastics through their diet," commented Torres. "It is likely that humans are also consuming a considerable quantity of microplastics through our own consumption of fish."

Torres noted that the estimates of microparticle consumption are likely conservative since they only account for what the whales consume from zooplankton. Gray whales are likely ingesting additional microparticles directly from the water and sediment on the seafloor because they are filter feeders that take in large volumes of water while consuming prey, as well as using suction feeding to obtain prey from the seafloor.

The analysis of fecal samples provided insights into the types of microparticles that these gray whales were digesting. The researchers examined five samples and found microparticles in all of them. Similar to the zooplankton samples, fibers constituted the majority of the microparticles.

Furthermore, the researchers observed that the microparticles found in the fecal samples were significantly larger than those in the zooplankton, leading them to believe that the larger particles originated from the water or sediment rather than from the prey (as the prey was too small to consume these larger particles).

The findings raise concerns for Torres, whose previous research has indicated that this subgroup of gray whales is thinner than other groups.

"These whales are already under stress due to the constant presence of boats and the risk of collisions," she remarked. "They might also have a scarcity of prey due to environmental changes, such as a decrease in kelp. And now, the quality of their prey may be compromised due to high loads of microplastics."

Brander and Torres are continuing their investigations by studying the effects of microfibers on zooplankton, which are a vital food source for whales and fish in Oregon waters.

"All of these factors can lead to poor nourishment and overall poor health," Torres added. "This can result in stunted growth, smaller body size, reduced reproductive ability, and the abandonment of this habitat by the animals. All of these consequences are significant areas of concern."

Other authors of the paper are Julia Parker, Elissa Bloom, Robyn Norman, Jennifer Van Brocklin and Katherine Lasdin. They are all from Oregon State and in the colleges of Agricultural Sciences, Engineering and Science. Brander is also affiliated with Oregon State’s Coastal Oregon Marine Experiment Station at the Hatfield Marine Science Center in Newport.

Journal Link: Frontiers in Marine Science