A study of plastic debris floating in the Pacific between Hawaii and California shows researchers have been sharply understating the amount of trash there.

Giora Proskurowski, an oceanography faculty scientist with the Sea Education Association, said winds push plastic from the ocean surface down into the upper ocean. This causes researchers collecting debris from the surface to miss a large share of the trash in the water when it is windy.

His group determined this by gathering debris in two nets towed behind a boat.

On one day during a light breeze, the surface net gathered 431 pieces of plastic, while another net 16 feet below gathered 240 pieces.

Proskurowski estimates there is as much plastic in the top 3.2 feet of ocean as in the 29.5 feet below.

“;Surface net tow data dramatically underrepresents the total amount of plastics that are in the ocean,”; said Proskurowski, who presented his findings at a meeting of the American Geophysical Union in Portland, Ore., last month.

The data is from six expeditions between 2004 to 2009 to an area called the North Pacific subtropical gyre, where ocean currents convey plastic debris.

The zone includes a spot now called the Great Pacific Garbage Patch for all the plastic trash that collects there.

The researchers, which included scholars from two Massachusetts organizations—the Sea Education Association and the Woods Hole Oceanographic Institution—gathered 17,000 pieces of plastic in 260 net tows.

Proskurowski told reporters in a teleconference that he realized one day, while observing the sea on a day with no wind, that studies were underreporting the amount of plastic in the ocean.

“;I had a eureka moment on a flat, calm day,”; he said. “;When I looked off the deck of the ship, I saw hundreds and hundreds of little tiny pieces of plastic floating at the surface that I'd never seen before.”;

When winds later picked up to about 7 to 10 knots, he lost sight of all the debris he had been watching.

Most of the trash is small specks that have been broken down over time from plastic bottles and other garbage.