What the Great Barrier Reef is made of [Australia]
Intro: When given the opportunity… or when in Rome… actually, I don’t think either of these really work too well, but what I’m trying to do is segway into my blog post about my stop-over in Cairn, Queensland, Australia; gateway the Great Barrier Reef!
Having come via New South Wales and a month at my research field site in Papua New Guinea (a post saved for another time!), I had to stop-over in Cairns on my return. Being a student of earth and ocean sciences, I have a love for the oceans and am fascinated by marine life and processes. I’ve wanted to do my scuba diving certification and dive the Great Barrier Reef (GBR), thus, I took the opportunity to delay my flight-layover and check out the fish and coral on a 5 day live-a-board boat with ProDive PADI from Cairns.
Being underwater is like immersing yourself into a different world, and what a better place to do it than the Great Barrier Reef; one of the 7 Natural Wonders of the World. Not only is it home to over 2000 species of fish, sharks, turtles and jellies, but it includes over 600 types of coral, which is going to the highlight of this post. While not as popular or well photographed as the stunning fish, the corals of the GBR are the lifeline, and as a geologist it’s also cool to see one of the most common rock types in the making; limestone.
Science Spiel: Reefs and Future Rocks along the Great Barrier (Oceanography, Biology, Geology)
As I mentioned in the intro, corals really are the lifeline to the GBR, and in fact, they are living creatures themselves. Each coral is a collection of tiny coral polyps; little jellyfish (sort of). There are many different varieties of coral, but they can be classified as two main types; hard and soft coral. Hard corals are by far the most common, and they come in a variety of spectacular types, which are named quite appropriately I think, as obvious by the photos. These include branching coral (the fastest growing coral, including the common staghorn, finger and needle forms), boulder coral (honeycomb, brain) plate/table coral, cabbage/lettuce coral (elephant ear), and more!
The main structure of coral is formed from each polyps as they secrete calcium carbonate (CaCO3) from the surrounding seawater and use this to form the coral’s skeleton. This is how reefs build up to form great masses, and what’s even neater is that the calcium carbonate skeleton forms rocks called limestone; one of the most common rock types found in the geological record. What’s so important about limestone is that even when you see rocks that are millions of years old and on the peaks of mountains thousands of kilometres from the ocean, if they are made of limestone then it is likely that they originally formed in an environment much like the Great Barrier Reef we see today.
Because of their calcium carbonate skeletons corals are very sensitive to their environment, specifically changes in temperature and acidity. Even small changes to slightly more acidic conditions (lower pH) will cause enough damage to dissolve a coral’s CaCO3 skeleton. An indication of early environmental stress, possibly from corals becoming too hot, is bleaching (a response when corals shed their colourful algae and appear bleached). Unfortunately, due to climate change the average sea surface temperature is likely to continue to increase to up to 1 to 3 degree warmer than at present in the next 100 years, which, along with the increased CO2 in the atmosphere and rising sea level, will decrease coral’s small habitable zones (Great Barrier Reef Outlook Report, 2009).
The Great Barrier Reef is one of the most biodiverse and therefore complex natural systems on earth. It is massive, close to 350,000 km2, and yet incredibly fragile. I would encourage anyone to take the opportunity (when in Rome!) to check out the reef, as it really lives up to its title of one of the 7 Natural Wonders of the World. If you keep your eyes open and curiosity engaged you will learn a lot and appreciated this unique underwater environment all the more. A good way to educate yourself is to read up ahead of time on the reef, or even easier, check out some local educational presentations like Reef Teach in Cairns. Scuba diving and/or snorkeling is a fantastic way to see the GBR, but as I would also recommend keenly, try not to be too distracted by the fish and check of the living future rocks in the making (i.e., amazing corals that surround you)!
…that being said, I will end this post with some non-coral focused photos below because I’m a hypocrite, cheers!
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