There’s a vast ecosystem stretching far below the ocean’s surface — one where the light dims, the pressure mounts, and life takes on forms that can seem downright alien. But even there, a place that seems a world apart from human society, our plastic trash is building up.
In the deep sea, it’s a challenge to study where that plastic accumulates and how it affects animals. So scientists at the Monterey Bay Aquarium and our partners at the Monterey Bay Aquarium Research Institute (MBARI) launched an ambitious collaboration.
The resulting study, which examined microplastic in the waters of Monterey Bay, was published June 6 in the journal Scientific Reports.
“We designed this study to answer a fundamental gap in our knowledge of marine plastic once it reaches the ocean,” says lead author Anela Choy, a former MBARI researcher and now a professor at the Scripps Institution of Oceanography in San Diego.
The research team gathered data by using remotely operated vehicles (ROVs), robotic submarines designed by MBARI engineers, to collect water samples at depths from 200 to 600 meters (about 650 to 2,000 feet).
They also searched for plastic in animals with important roles in the marine food web: pelagic red crabs; and tadpole-like creatures called giant larvaceans, which surround themselves with clouds of mucus that capture food — and, as the researchers discovered, plastic.
“We have to get our heads collectively around how much [plastic] might be entering the ocean every year,” said Dr. Roland Geyer, an associate professor of industrial ecology and green supply chain management with the Bren School at UCSB.
Global plastic production has far surpassed the production of metals like aluminum and steel. Globally, people have created and used 7 billion metric tons of plastic over the past 65 years—half of that in just the past 15 years.
Monterey Bay is home to an astonishing array of marine life, from kelp forests to sea otters to migrating whales. The secret to its productivity: the California Current.
The California Current flows southward along the West Coast of North America delivering cool, nutrient-rich water from British Columbia to Baja California. Prevailing northwesterly winds drive the current and stimulate upwelling, a process by which cold water rises from the depths to support biodiversity off the coast.
Monterey Bay’s rich ecosystem naturally varies in response to physical changes in the environment. But human-caused carbon dioxide emissions are driving long-term shifts that could impact fisheries and vulnerable marine species in ways we’ve never seen before.
Weird is the new normal
Life in the California Current naturally fluctuates from year to year, partially due to temperature changes, said John C. Field, a fisheries biologist with the National Oceanic and Atmospheric Administration (NOAA).
In cold-water years, he says, upwelling brings nutrient-rich deep waters to the surface, typically supporting an abundance of rockfish, krill and market squid. Warm-water years, when less upwelling occurs, bring more sub-tropical species, such as pelagic red crab. Some years, jellies and other gelatinous creatures dominate the current, for reasons scientists don’t yet understand.