"Why is it that no one in Hawai'i knows about (the North Pacific Gyre) when it is so unbelievably detrimental to the Pacific Ocean and all things living around and in it, mainly us? ... How is it that no one in Hawai'i's public has been made aware of this when the southwest corner of the gyre is sitting right on top of the NW Hawaiian islands?"— Donny Sato, Wahiawa.

A gyre is a big spiral, and in the North Pacific it is a vast current system, with different names depending on where it flows. Clockwise from the north, it is the east-flowing North Pacific Current, then the California Current, the west-flowing North Equatorial Current, which is south of Hawai'i, and finally the Kuroshio or Japan Current.

As it goes along, the current collects all the stuff that's been dumped into the sea from freighters, fishing boats and even things that wash out from the shores that fringe the Pacific. Much of that material gets sucked into the center of the gyre. If you think of the current as a doughnut, the center area is the hole. And that hole is filled with marine debris.

It's got plastic bottles, nets, ropes, toys, floating shoes and slippers, glass balls and plastic floats, plastic cigarette lighters — great rafts of debris and more debris.

Much of the plastic has become brittle and broken down into smaller and smaller pieces. The tiny bits of colored plastic are mistaken by birds and marine life as food, and get eaten. One result: Birds have their bellies so crammed full of plastic that they can't take in normal food. You can find their bodies drying in the sun on islands of the bird-rich Northwestern Hawaiian Islands.

There are concerns that chemicals in the plastics are poisoning marine life. The debris is also a mechanical danger — entangling turtles, birds and seals, and ripping up the reef as great tangles of rope and net wash onto it in heavy surf.

Greenpeace has an interesting animation showing the progress of marine debris in the north Pacific at oceans .greenpeace.org/en/the-exp edition/news/trashing-our-oceans /ocean_pollution _animation.

The gyre regularly deposits marine debris at the northwestern end of the Hawaiian archipelago, in the islands of the Papahanaumokuakea Marine National Monument. And often during El Niño conditions, the gyre moves southward enough that the debris field intersects the main Hawaiian Islands, dumping piles of debris on our reefs and beaches. Occasionally the remains of dead marine life are found in the debris.

If you have a question or concern about the Hawaiian environment, drop a note to Jan TenBruggencate at P.O. Box 524, Lihu'e, HI 96766 or jant@honoluluadvertiser.com. Or call him at (808) 245-3074.