Oceans and estuaries such as Puget Sound cover over 70 percent of Earth's surface. Most of the planet's biodiversity is found beneath the waves. As food source and regulator of global temperature, the ocean has a profound influence over our lives. And yet, too often, the oceans are "out of sight, out of mind."

Even those of us who live intimately with the shorelines of the ocean realm too often fail to understand the vital role played by all those lives that go on beneath its beguiling surface.

Growing up aboard the research vessel Calypso, for me the dive mask is a window of discovery -- but also a mirror of responsibility. It is impossible to remain indifferent to the fate of plants, animals and places that have given one such intense moments of joy.

The ease with which we ignore or take for granted the life of the oceans has itself become a serious threat to marine health and our own future. When oceans and their life-giving estuaries are so readily overlooked, it becomes easy to use them as global waste dumps and to ignore the signs of crisis.

The signs of ocean decline are evident. They should lend urgency to the thinking of policymakers from county courthouses to Olympia and Washington, D.C., and around the world.

Ultraviolet radiation streaming through the growing ozone hole produces changes at the cellular level of living organisms. It has already been observed to cause reductions in the abundance of phytoplankton and zooplankton, the building blocks of open ocean productivity.

This comes at a time when humans are hungry for fish. According to the United Nations, the world's 17 major fishing grounds are all being exploited at or beyond their sustainable capacity. More than 1,000 fish species are endangered. We have not been fishing, but vacuuming the sea.

When the waters run out of fish -- as is happening here in Puget Sound, not just in far-away places -- governments step in to prop up unsustainable industrial vacuuming of the last fish. In 1994, $124 billion was spent trying to catch $70 billion worth of fish.

Increasingly, fish reach the market with high concentrations of harmful bacteria and toxic chemicals. Consumer's Union reports that fish are the biggest source of polychlorinated biphenyls (PCBs) in humans. Fish are also significant accumulators of mercury, lead and pesticides. The risk of oil spills is ever-present, threatening an assault against which already heavily-stressed marine ecosystems are ever more vulnerable.

Global warming is a fact. Oceanic warming means sea-level rise and the "drowning" of estuaries and coastal wetlands, where most commercially valuable fish are reared. It means stress and even death to the algae upon which corals depend for life.

Around the planet, coral reefs are rapidly deteriorating. Reef-based food chains are crucial in many island nations of the Caribbean, Pacific and Indian oceans. Yet in 93 out of 100 countries in which they are found, corals are damaged. When not dynamited for fish and trinkets, they are suffocated by sediment when the rain forests and mangroves that function as natural filters of runoff are razed for cropland.

This is more than a local issue. With perhaps more than a million species, coral reefs are the rain forests of the sea, a fount of marine biological diversity.

In Puget Sound, rocky reef habitats and nearshore eelgrass beds play the same role. These, too, have been sorely diminished by the cumulative impact of human disturbance.

When pollution, overfishing and destruction of their vital spawning habitats lead to crashing herring populations, we shouldn't be surprised that chinook salmon, who feed on herring, are in big trouble, too.

Loss of oceanic biodiversity means loss of genetic diversity. Losing species is like removing rivets from the airplane in which we are flying. As in any Boeing airplane, nature has some built-in redundancy. Not all species are needed to keep it going. But just as passengers don't know which rivets are the important ones, we do not know which species can be lost without endangering our own life-support system.

The North Pacific and its once amazingly productive estuaries, including Puget Sound, are hardly immune from the vastly destructive impact we humans are having upon the life of the seas. Here salmon are already on the endangered species list.

Many marine fish that spend their entire lives in Puget Sound, such as herring, cod and rockfish, are in shocking population declines that will put them on that list, too.

Puget Sound's famous orcas -- the killer whales -- are so laced with PCBs (built-up from their salmon and seal-rich diet) that they are now the most chemically contaminated mammals on the planet, putting their immune, neurological and hormone systems at risk. Puget Sound's shoreline habitats, the nursery for many species, are being decimated by an insidious process of one more dock, one more bulkhead all the while ignoring the deadly cumulative impact.

When I look to the ocean or the Sound, like most people I see the beauty of light on the water, but I am also aware that my actions on land affect what goes on beneath the surface.

The oceans are not as vastly productive as they once were. Nor are nearshore marine habitats anywhere near as healthy as their surface beauty might suggest.

The oceans and their fragile reefs and estuaries have real biological limits, and we have reached them. Out of sight is no longer out of mind.

Jean-Michel Cousteau is president of the Ocean Futures Society, a nonprofit organization that provides the global community with a forum for exploring issues affecting the ocean, its inhabitants and habitats. Online at www.oceanfutures.org

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