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bright colours tend to indicate that hard coral are not very healthy
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date: 29/9/2009
Author:Nick Brennan
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Weather: Sunny
Wind: South West/ South East 10/15 knots
Water Temp: 23°C
Water Visibility: 20m+
Sea State: Calm
Conditions were stunning all around the island today. Wind was minimal and the snorkeling was terrific.
Guests venturing out to the Lighthouse to snorkel and came across literally dozens of turtles. They are so active at the moment and they are guaranteed to put a smile on anyone’s face. The scissortail fusilier were schooling in a ridiculous abundance feeding on the plankton at the lighthouse bommies. Guests loved that when they stayed perfectly still the fish would completely surround them making a swirling mass of colour.
After a long morning in the water guests came on a guided reef walk. A host of invertebrate species were found including the Blue Linckia Seastar. After taking some sensational postcard perfect photos guests learnt that sea stars evert their stomach out of their mouth to feed. A bit further out on the reef the children discovered a New Caledonian Seastar. The guests were lucky enough to see this seastar feeding with its big orange belly hanging out. The other creature guests enjoyed seeing was the Diadema Sea Urchin with its very long, needle point spines protruding from a crevice. Also on the walk guests were shown a few small patches of stressed out coral. It came as news to a lot of people that bright colours tend to indicate that hard coral are not very healthy. Hard corals don’t like a lot of things including: too much sunlight, too many nutrients, temperatures above 31°C or below 19°C, too many suspended sediments. If corals even slightly get pushed outside their comfort zone they expel the microscopic algae that lives in its tissue into the water column. The microscopic algae, called zooxanthallae, provides the coral with up to 90% of their energy and without zooxanthallae the coral will quickly die. When the coral has expelled its zooxanthallae the animal pigment becomes visible which is often a very bright colour and when the animal dies all that is left is the white skeleton - this is what is known as coral bleaching.
In the evening guests came on a climate change trail walk and learnt how global warming and an increase in greenhouse emissions are likely to affect Lady Elliot Island. The walk was great fun with the kids helping to locate signs and turnoffs that took everybody through the bush and through thousands of thousands of birds. Guests learnt lots of interesting facts but perhaps the one that surprised them the most is that some corals have slowed their growth by 14% since 1990. The reason for this is the increase in atmospheric carbon dioxide over the last century has made the worlds oceans slightly more acidic. Calcium dissolves in acid so this means that animals that produce calcium skeletons have a harder time doing it. So not only is the reef getting destroyed by warmer water, but it is having a harder time growing back! It was a big wake up call to everybody on the walk, over the last days they have realized how special coral reefs are and we are sure they will do their best to help overt this enormous crisis by simple measures such as turning off the light switch.
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bleached coral - jenni
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