Sprol

In Australia, summer has officially ended, but not without leaving its mark. Queensland and New South Wales saw their hottest summer on record in 2006. As a result of the hot weather, the temperature of the ocean has risen.

One might be tempted to think that’s a good thing. After all, who wouldn’t enjoy a leisurely swim in bathtub-warm water? But there is a significant downside to the hot weather in this particular part of the globe, one that both tourists and natives alike will find hard to warm up to: the beautiful coral reefs that give the region’s Great Barrier Reef its fame, and its beauty, are losing their color.


The Great Barrier Reef from the air. Photo: charlton_b

It’s a fairly straightforward process: when the weather gets warmer, the ocean water heats up. Among other causes, it is this unusually hot water which causes the vibrant colors to, physically, leave the coral.

This is because the color is due to the presence of zooxanthellae, tiny algae that live in healthy coral. Under cooler temperatures, these algae thrive in their symbiotic relationship with their coral hosts. But when the temperature rises, these sensitive life forms literally can’t take the heat.

Close up of coral polyps, one of which has bleached. Photo: amell

When the water temperatures reach a certain point, the zooxanthellae are expelled from the coral, leaving a white, or bleached coral where there once was vibrant color. This not only leaves the coral bereft of its spectacular beauty, but causes a reduction in nutrients that would normally be created via photosynthesis.

In addition to diminishing the colorful nature of the reef’s coral gardens, which have historically made the Great Barrier Reef a prime destination for tourists, warming ocean waters have other deleterious effects. When the temperature of ocean water gets too high, it causes a decrease in the phytoplankton that grows in the top layer of the ocean. This is particularly problematic because phytoplankton are the “foundation of the marine food chain.” When they decrease in volume, the fish that live on them must eat less or go elsewhere.

The reason warmer temperatures cause a decrease in phytoplankton has to do with a mineral we are all familiar with: iron. It takes a certain amount of iron to feed the phytoplankton. But, when ocean waters become too warm, the colder water that typically pulls the iron up into the surface of the water (referred to as “upwelling”) does not occur. This prevents the phytoplankton from getting the iron they need, causing them to die off; which, in turn, leaves too little food for the fish that feed on it. Too little fish food, leads to fewer fish, which leads to fewer birds (who feed on fish) and so on.

It’s an endless chain of cause and effect. And it’s not just a theory. In 2002, 50 percent of the seabird chicks hatched on Heron Island, which is located in the southern part of the Great Barrier Reef, starved to death because there were not enough fish to feed them.

While many of the consequences of warming ocean waters are known, one can’t help but wonder what additional, and as yet unknown, dangers may await us if the current global warming trend continues. With over 1500 species of marine animals living in the Great Barrier Reef, which covers over 2000 km of the northeastern Australian coast, there’s a lot to keep track of. But one thing is certain: if we suffer a significant loss of one life form, we are pretty much guaranteed the death, relocation, or perhaps even mutation, of another.

For this reason scientists at NASA are studying the Great Barrier Reef with increased intensity, now that climate change is upon us. Gene Carl Feldman of the Ocean Biology Processing Group put it this way: “Coral, which can only live within a very narrow range of environmental conditions, are extremely sensitive to small shifts in the environment. Like the ‘canary in the coalmine,’ coral can provide an early warning of potentially dangerous things to come.”

In order to process such environmental changes more closely, NASA has installed an instrument known as a Moderate Resolution Imaging Spectroradiometer (MODIS). The MODIS system allows NASA to gather data from the region, via satellite, and make that data available for internet access within hours of the satellite’s passing over the area. This gives scientists an extraordinary “real time” view of what’s happening in the region.

Yet, despite the state-of-the-art data collection equipment NASA is using to transmit information across the globe, it appears that any real response to this troubling trend is in the future. While a recent editorial in the New York Times hailed the addition of two forms of Caribbean coral to the endangered species list (elkhorn and staghorn), the article failed to mention how labeling their destruction as bad will actually prevent the conditions that are destroying them.

If careless scuba divers, poachers and toxic waste were the sole contributors to the problem, the solution might be simpler. But the reality is that unless we control global warming, the main cause of coral bleaching will remain unchecked. And if that continues for long, we may not be able to predict the exact nature of the consequences that will follow, but there is little question that they will be tragic, indeed.