People pose the greatest threat to this delicate marine ecosystem

EVERYBODY'S heard about the value of rainforests.

How they house countless undiscovered creatures, foods, plants and medicines - maybe even the cure for cancer.

The same can be said of coral reefs.

Only 2 percent of the world's oceans houses coral reefs, but in that small area teems a staggering diversity of life. And the coral reefs of Hawaii are home for the majority of coral found in U.S. waters.

Hawaii's reefs are home to more than 40 species of reef-building coral and more than 5,000 marine species. One in four of Hawaii's reef plants and animals are found nowhere else in the world.

The most pristine reefs are in the uninhabited and protected Northwestern Hawaiian Islands. The decline of reef ecosystems in the main Hawaiian Islands shows clearly that, as in the rainforest, the biggest threat to the coral reef's delicate web of life is - humans.

Scientific research conducted in Hawaii has made clear that:

» Overfishing upsets the natural balance among reef inhabitants.

» Marine debris, discarded fishing nets and anchors damage coral.

» Dirt and pollution from land development can weaken or kill coral.

» Fertilizer runoff and sewage can cause overgrowth of algae, particularly aggressive, non-native species that kill coral and compete with native limu.

» Careless divers, snorkelers and boaters can damage the reef.

» Global warming is raising sea temperatures and contributing to coral bleaching - the die-off of the symbiotic algae that live inside many coral animals.

» Observations of coral disease are increasing.

"In Hawaii, more than 1.2 million people live within three miles of living coral reef," Dave Gulko, a state Division of Aquatic Resources coral reef scientist. "On Oahu, Maui and at Kailua-Kona, you have some of the largest human populations so near major coral in the Pacific, if not the world," he said.

Coral reefs provide food and habitat for many fish and invertebrates. They buffer the islands from storms and create the break for our famous waves.

A majority of island residents spend time on Hawaii's reefs, beaches and nearshore waters, according to a survey by the Hawaii Coral Reef Initiative Research Program.

Survey respondents from 1,600 households said they are worried about the increasing pressure on beach and reef areas from development, pollution and overfishing. Some mentioned that Hawaii would be just like the mainland if it weren't for the reef and beach areas.

"My husband, a lot of times he'll leave work early to just surf, especially if he's having a bad day. He comes out of the water and feels rejuvenated. He's able to push all that stress away just being there," one respondent said.

Respondents said they want stricter enforcement of existing rules to protect Hawaii's reefs, new rules as needed and restricting activities at biologically important areas.

Earlier research by the University of Hawaii-based research program estimated that Hawaii's reefs generate $364 million a year. But the full value of their worth can't be calculated.

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BASIC LIFE CYCLE OF CORAL

Most coral can reproduce both sexually and asexually. Asexual reproduction comes from budding, when an individual coral branches out to form a new animal, or when a piece of coral breaks off and starts to grow on its own. In both cases, the new animal is genetically identical to the original. Here's how coral reproduces sexually:

Depending on the species, eggs and sperm may come from separate male and female coral animals, or from hermaphrodictic animals that produce both eggs and sperm. Eggs are buoyant and fertilization often occurs in surface waters.

A fertilized egg has a larval stage, during which it is free-swimming. The free-swimming coral larvae are called planula.

The planula finds a suitable place to attach itself to a firm surface and grow into a polyp. Many eggs, sperm and larvae are eaten by other marine life before they get to this stage.

A young coral colony may grow by asexual budding for years before spawning. Mature coral spawn - releasing eggs and sperm - at precise times of the day or night and seasons of the year that are specific to its species. Many coral seem to time their spawning by phases of the moon. If eggs and sperm weren't released into the ocean at the same time, they would have little chance of finding each other.

Polyps secrete calcium carbonate, which creates the stony skeleton of the coral colony.

CORAL POLYP

An individual coral animal is called a polyp. Each live polyp sits in a cup-like depression called a calyx. Polyps, which close up look like tiny anemones, form the outer living layer of a coral colony.

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DOS AND DON'TS TO PROTECT THE CORAL

» Do enjoy live coral in the ocean. But don't touch it, rub against it, walk on it or drop anchor on it. Whether hundreds of years old or just getting established, the living part of coral is on its outer surface - the very portion of it that people are most likely to disturb. Research shows that being stepped on nine times can kill a coral.

» Do clean your boat hull regularly. Many of the aquatic invasive species in Hawaii, which can overgrow and harm native species, hitched a ride here from faraway ports on boat hulls or in ballast water. That's also how they get from one place to another in-state. Cleaning boating equipment (including anchors, chains and ladders) and dive gear keeps the damage from spreading. Be sure to dispose of what you clean off in a rubbish bin.

>> Do observe fishing regulations. Take only what you need; comply with rules about when and where to fish; and obey the size limits. The rules are designed to allow fish to reproduce.

» Do get involved in waterfront cleanups and ocean monitoring. Every piece of trash removed from a beach is a piece that won't be back in the ocean with the next storm. And trained volunteers who participate in periodic surveys of reef life help scientists track the health of coral reef ecosystems.

» Don't take coral home. State law prohibits the breaking, damaging or taking any stony coral from Hawaii waters, including reef and mushroom corals. It's also illegal to sell any stony coral native to the Hawaiian Islands. First violations are subject to a fine of up to $1,000 and/or 30 days in jail, plus up to $1,000 per specimen taken illegally. Penalties increase for subsequent violations.

» Don't dump aquarium water. No aquarium water or creatures should go into streams, storm drains or the ocean. Flush water down a toilet and bury the rest.

» Don't leave fishing equipment in the ocean. Abandoned fishing lines and nets can entangle and kill marine mammals, sea turtles and fish. These "ghost nets" and debris can also damage coral reefs.