The New Pollution: Monterey Bay is Swimming in Microplastic

Monterey Bay — long considered an environmental success story–is now facing a new threat: tiny particles of plastic.

And scientists are finding that it’s far worse than they suspected.

The bay is a national marine sanctuary, a place where environmental protections and sustainable fishing have transformed what was once a stew of dumped waste products from local sardine canneries.

Long gone is the industrial filth that John Steinbeck described in his Depression-era novel Cannery Row. Now, the bay is cleaned up and home to seals, otters, and the occasional humpback whale.

“This is not where you would expect to find tons of marine pollution,” said Kyle Van Houtan, who oversees research for the Monterey Bay Aquarium.

But that’s exactly what researchers found when they sent a robot trolling into the water. Van Houtan’s team found  microplastics in quantities much higher than previously expected at nearly every level of the water column, according to a paper published this week in Scientific Reports from the publishers of Nature.

This suggests that the deep sea, the Earth’s largest habitat, could be its “biggest repository of small plastic debris,” said Anela Choy, the report’s lead author, in a statement released with the study.

At about a quarter-mile below the surface they found plastic particles at concentrations four times that near the surface or along the sea floor.

Most of the samples were collected in Monterey Canyon, about 15 miles off the coast. The team took a smaller number of samples from Moss Landing Harbor.

Previous studies focused on plastic on the surface of the ocean, in places such as the much-publicized mid-ocean vortex known as the Great Pacific garbage patch, and on the sea floor. But Scientists have recently begun to focus on degraded motes of microplastics floating around in the water column.

To marine life, scientists say the plastic is indistinguishable from the organic material known as “marine snow,” commonly eaten by small crabs and filter feeders, which consume the plastic and introduce the pollution into the larger food web.

“Our study demonstrates a link between microplastics distributed across the water column and entry of this foreign material into marine food webs,” said Choy, a marine biologist with Scripps Institution of Oceanography in San Diego.

The paper is a joint study between Scripps, Monterey Bay Aquarium, and its sister organization, the Monterey Bay Aquarium Research Institute.

The plastic particles are not likely local, but the accreted debris from plastics that have been in the ocean for years, maybe decades.  Much of it was probably once single-use plastic that has broken down over time.

“We are finding material that circulated throughout perhaps the entire North Pacific,” Van Houtan said.

Using robots that filtered seawater to capture particles smaller than 5 millimeters in size, they collected repeated samples at a range of depths, from just below the surface to 3,000 feet below.

“In order for us to access these areas, we rely on robotics to do that work,” said Kakani Katija, an engineer with  MBARI. “We were able to find microplastics even in the deep sea.”

Removing the plastic from the ocean is a real challenge, Katija said, adding that a solution might be to prevent more of it from polluting the water in the first place.

California lawmakers are considering legislation to phase out the sale and distribution of some plastics. The companion bills, SB 54 and AB 1080,  target a wide range of single-use plastics, such as utensils, containers, and other items that can’t be recycled. The bills moved forward in the Legislature last month.

“I can’t think of a dive that I’ve been on that I haven’t seen some form of plastic, whether it be plastic bottles, or plastic bags,” said Amanda Kahn, who studies deep sea sponges in Monterey Bay as a postdoctoral fellow for MBARI. “One time we saw a plastic lawn chair.”

KQED Fuhs Fellow Jazmine Mejia Munoz contributed to this report.