Biotechnology

The droppings and prey helped researchers predict gray whales off the coast of Oregon

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CORVALLIS, Ore.- Oregon State University researchers estimate that gray whales feeding on the Oregon Coast consume up to 21 million microparticles per day, a finding that is partially informed by whale excrement.

Credit: GEMM Lab, Oregon State University.

CORVALLIS, Ore.- Oregon State University researchers estimate that gray whales feeding on the Oregon Coast consume up to 21 million microparticles per day, a finding that is partially informed by whale excrement.

Microparticle pollution includes microplastics and other human-sourced materials, including fibers from clothing. The findings have just been published in a journal Frontier in Marine Scienceis important because it is increasing exponentially and is expected to continue to increase in the coming decades, according to researchers Leigh Torres and Susanne Brander.

Microparticle pollution is a threat to the health of gray whales, as well as obstacles related to increased boat traffic and loss of prey.

“These are pretty scary numbers,” said Leigh Torres, a professor at Oregon State and author of the paper. “I think they should raise awareness about people who are concerned about the marine environment or about their own environment and exposure to microplastics.

“Little by little we are all getting exposed to microplastics. It is unavoidable at this point in all ecosystems, including directly off our coast here in Oregon.

Susanne Brander, a professor and ecotoxicologist at Oregon State and a co-author of the study, said the findings reinforce the need to curb the release of microparticles because of their adverse effects on organisms and ecosystems.

“This issue is gaining momentum globally and some states, such as California, have taken important steps,” Brander said. “But more action needs to be taken, including here in Oregon, because this problem is not going away any time soon.”

The study focused on a subgroup of about 230 gray whales known as the Pacific Coast Feeding Group. They spend the winter in Baja California, Mexico and migrate north to forage in coastal habitats from northern California to southern British Columbia from June to November.

Since 2015, Torres, who directs the Marine Megafauna Geospatial Ecology Laboratory at OSU’s Marine Mammal Institute, and his team, including doctoral student Lisa Hildebrand, have been using drones and other tools to study the health and behavior of this subgroup of gray whales. Oregon Coast. As part of this work, they collected faecal samples from gray whales.

For the new study, the researchers collected zooplankton, which are an important food supply for gray whales, as well as commercial and recreational fish.

“We have determined the caloric content of several species of zooplankton, so next we wanted to know their microparticle load to get a more complete picture of the quality of these prey,” said Hildebrand.

Brander, Hildebrand and members of Brander’s Ecotoxicology and Environmental Stress Laboratory analyzed microparticle loading in 26 zooplankton samples collected from the whale feeding area and found microparticles in all of them. A total of 418 suspected microparticles were identified, with fibers accounting for more than 50% of them.

Torres and Hildebrand then combined that data with known estimates of energy requirements for lactating and pregnant female gray whales to calculate how much zooplankton and microparticles they consume in a day. That yields estimates that lactating and pregnant whales consume between 6.5 million and 21 million microparticles per day.

“This is a warning that whales get a lot of microplastic from what they eat,” said Torres. “It seems that humans also get a lot of microplastic from our own fish diet.”

Torres notes that estimates of microparticle consumption tend to be conservative because they only account for what whales consume from zooplankton.

Gray whales likely ingest more microparticles directly from the water and bottom sediments because they are filter feeders that swallow large amounts of water while consuming prey and also use suction to get prey from the seafloor.

Analysis of fecal samples provides an idea of ​​what kind of microparticles these gray whales ingested. The researchers analyzed five fecal samples and found micro-particles in all of them. Similar to zooplankton, most of the microparticles are fibers.

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

The finding is a cause for concern to Torres, whose previous research has shown that this subgroup of gray whales is thinner than other groups of gray whales.

“These whales are already stressed by the constantly moving boats and the risk of being hit by one of them,” he said. “They may also have had less prey due to environmental changes, such as less seaweed. And now the quality of the prey may be poor because of this high microplastic load.”

Brander and Torres continued their investigation by studying the effects of microfibers on zooplankton, an important food source for whales and fish in Oregon waters.

“All of these can lead to poor nutrition and poor health,” says Torres, “It can lead to stunted growth, smaller body size, lower ability to have calves and animals not using this habitat anymore. These are all areas of important concern.

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


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