The amount of plastic in the ocean area known as the “Great Pacific Garbage Patch” has increased a hundredfold since the early 1970s, according to a new study, and the alarming findings could pressure California and other coastal states to do more to reduce plastic trash.

“We were really surprised. It is a very large increase,” said Miriam Goldstein, a Ph.D. graduate student in biological oceanography at the Scripps Institution of Oceanography and lead author of the study.

“Plastic had been detected in the open ocean in the early 1970s,” she said. “People were raising the alarm then. The fact it has gotten so much worse is really disappointing.”

During an expedition in 2009, Scripps researchers took extensive water samples 1,000 miles west of California, then compared the amount of plastic they found with samples taken by other researchers dating back to 1972.

While many of the samples 40 years ago found little or no plastic, vast stretches of the North Pacific are now polluted with billions of tiny pieces of confetti-like trash that comes from garbage that floats out to sea and breaks down in wind and waves.

The tiny bits sit on or near the surface, where they are eaten by fish, sea turtles and other marine animals that confuse them for food. The latest samples show that the garbage patch has grown not in size but in density: There are roughly 100 times more pieces per cubic meter of water than were in samples during the 1970s.

Debris in food web

The research, published in Wednesday’s online editions of the journal Biology Letters, also found the debris is affecting the food web.

Goldstein and her co-authors, Marci Rosenberg of UCLA and Scripps biologist emeritus Lanna Cheng, found a growing number of eggs from a marine insect commonly known as a “water strider” or “sea skater.”

The bugs normally lay eggs on pieces of wood, feathers and other naturally occurring objects that float. But with the increasing amount of plastic, they have found a new place. Goldstein said Tuesday that more research is needed to see what impact the change will have on other species. But because the bugs eat zooplankton and fish larvae, an explosion in their population could lead to a reduced food supply for other animals, including fish and turtles, which eat the same prey. More bugs also could mean more food for animals that eat them.

The study this week follows another study last year by Scripps scientists that showed 9 percent of fish collected on the expedition to the Pacific Garbage Patch in 2009 — nearly 1 in 10 — had plastic in their stomachs.

Goldstein said cleaning up the plastic trash in the ocean is virtually impossible, given the vast scale. The Pacific Garbage Patch, for example, stretches for hundreds of miles and is located 1,000 miles north of Hawaii.

“Most people who work on this issue agree that prevention is the critical step,” she said. “Once a piece of plastic is in the ocean, it is really hard and expensive to get it out again.”

More bans sought

This week’s study is expected to ramp up calls for more cities and states to ban plastic bags and plastic foam packaging. In California, 14 billion plastic bags are distributed annually, and only 3 percent are recycled.

In 2010, the state Senate voted 21-14 to defeat a bill that would have banned plastic bags from being given out at grocery stores and other retailers, after heavy lobbying and donations from the American Chemistry Council and the plastics industry.

Since then, cities and counties have been steadily passing their own bans.

As of this week, 45 California cities and counties including San Francisco, San Jose and Oakland have banned plastic bags at grocery stores and other retailers. Meanwhile, more than 60 California cities and counties have restricted or banned polystyrene foam, commonly known as Styrofoam, with some banning its use in restaurants and others banning it at city events.

Because about 80 percent of the trash in the Pacific Ocean comes from land — running off roads and into creeks and storm drains, or blowing off beaches when left as litter — this week’s study not only shows the need for more laws, it also illustrates a need for a change in behavior, said Kaitilin Gaffney, Pacific program director of the Ocean Conservancy, an environmental group.

“Clearly there is too much plastic in the ocean. An increase of one hundredfold in the past 40 years is alarming by any measure,” Gaffney said.

“This is a problem created by personal action, and frankly, personal carelessness. Ultimately, we need a behavior shift,” she added. “When I was a kid, everybody smoked. Now most people don’t smoke. The solution really is to move away from single-use items, and we need people to basically be more thoughtful.”

Paul Rogers covers resources and environmental issues. Contact him at 408-920-5045.