The coral reefs in the waters surrounding Cayman are dying, and it is algae that is killing them, some marine experts say.

There is a delicate symbiotic relationship between coral and algae: The coral feeds the algae, and the algae uses sunlight to produce carbohydrates and fats that the corals consume. The reef ecosystem provides food, and it lures tourism that is geared to underwater adventure in and around the reefs.

When the sea temperatures reach heated levels, the corals expel the algae, essentially starving themselves. The corals turn a bright white or lighter shade, something that is referred to as ‘coral bleaching.’ If there are too many nutrients in the water, often caused by large deposits of waste from humans that acts like a fertiliser, the algae overtake everything in the area, including corals.

Thomas Goreau, president of the Global Coral Reef Alliance, a nonprofit organisation for coral reef protection and sustainable management, believes that the overabundance of nutrients in the water caused by sewage and waste runoff causes algae overgrowth that leads to fewer fish in the areas - known as the ‘bottom up’ theory.

“Every place I dived in Grand Cayman, there was an overgrowth of algae,” Mr. Goreau said.  “Cayman believes that they are a top diving place in the world, so they don’t do much to change.”

He said that decisions regarding coral reefs around Cayman are made on economic and marketing grounds, rather than on the health of the reefs.

“(Cayman) is politically under a ministry who are for development at all costs,” he said.  “Cayman does have a nutrient problem, and like most places, they tend to be in denial.”

Unlike the majority of marine biologists who blame over-fishing for fewer fish in and around the dying coral reefs and overgrowth zones of algae - known as the ‘top down’ theory - Mr. Goreau stands by the bottom-up theory.

“... in the ‘80s down in the Florida Keys, a green ring formed around the island from septic tanks overflowing when the rain hit, and flooding occurred. In general, there’s excess nitrogen in the water, and if you put phosphorus in the water - wham, you get massive algae overgrowth,” said Mr. Goreau, who is also coordinator of the UN Commission on Sustainable Development Partnership in New Technologies for Small Island Developing States.

Referring to another common theory - climate change - Ray Hayes, a professor at Howard University and an expert on ocean warming and coral reefs, says climate change by itself cannot be blamed.

He said the accumulation of introduced waste from humans and other sources in conjunction with warmer water temperatures has led to the algae overgrowth.  New coral diseases also contribute to death of coral.

“Nutrient enrichment from fertilizer can lead to more nutrients in the sea,” he said. “Sewage needs to be treated to a tertiary level before it’s released.”

Mr. Hayes points to overpopulation and resulting septic overload, and high human density as agents of algae overgrowth.

Although Cayman has one of the oldest sets of marine protection laws, according to Mr. Hayes, there is more to be done in Cayman to protect the coral.

“I like to think of coral reefs as giving a feeling of satisfaction and recreation that supports human health,” he said, adding that coral reefs are an attractive resource that provide information and education on marine ecosystems.

The reefs are also important to human beings’ survival, as well as the survival of entire islands like the Cayman Islands.

Coral reefs protect the shoreline from erosion and it builds new sand for the beaches -- the beaches could be lost over time.  These are indirect effects on humans.

One of the direct effects of dying coral from waste nutrients is that the algae overgrowth and blooms of algae can create toxins in the water that could potentially kill fish and humans.

“The nutrients coming from the waste and sewage can also cause skin irritations and ear infections from the pathogens in the water,” Mr. Goreau said.

“The disconnect comes with the idea that people think that the reefs will somehow be there forever, that they’re inexhaustible,” said Tim Austin of the Cayman Islands Department of Environment, which has been monitoring coral reefs here for 14 years.

But there are some things that the average person who’s concerned about coral survival and clean waters can do.

“Homeowners can look for proper sewage treatment, and removal of waste and garbage,” Mr. Hayes said.  “Septic systems need to be checked and drained regularly to prevent overflow.  The government has responsibility as well.”

Mr. Hayes said that marine laws should be observed and enforced.

“It’s important for the public to be alert and aware.  If they see something that doesn’t look right, tell the authorities,” he said.  “The Department of Environment can’t be everywhere.  But there’s no reason the public should be violating these laws.”

The algae growth is reaching a point where decisions by the public, marine experts and government must be made to act decisively to save the coral reefs or lose them forever.

“When I see algae overgrowth, you know it’s very late in the day,” Mr. Goreau said.

“Fundamentally, the reefs around Cayman are instrumental in the quality of life that we enjoy on this island,” said Mr. Austin, who is assistant director of research and assessment of the DoE and oversees the department’s diverse marine and terrestrial research and conservation programmes on all three Cayman islands..

“They provide the fish, the calm water, the beaches, the protection from waves, the diving resources. And that does not take into account the ecosystems services that they provide, the biological diversity.”