Interview with Sea Life II: The Battle for Space on a Coral Reef

Coral on the Mesoamerican Reef
You know folks, it’s a war zone down here. This is Polly Polyp, reporting live from the front lines, the scene of the greatest action on the coral reef. If there is one thing that I have heard from the mouth of every person who snorkels above a coral reef it is how full reefs appear, and that is exactly the case. Each and every square inch is covered with somebody’s house: an encrusting hard coral, the base of a soft coral, a patch of algae, you name it. This leads me to our largest problem in reef living… open space or unoccupied substratum.

The only friends you have down here are the fellow polyps in your particular hard coral (as we learned in Sealife 1, each coral is made up of many individual polyps). So, you can forget about that nice looking brain coral growing alongside of you. He’s only eyeing your substrate, just waiting for his chance to move in, encrust over you, and eventually smother you. Then, there are the soft corals – the ones that look like bushes underwater - who are cheaters in my book. They grow faster than we hard corals do, they only have to defend the small reef area around their base, and they shade us from the sun. Since hard corals need access to sunlight, and we grow SO slowly, we have to be mighty in our defensive strategies.

Coral on the Mesoamerican Reef
We have only one form of ammunition, and it is in the form of tiny filaments we extend from our stomachs. When these filaments encounter any living tissue, we begin immediate digestion. This allows us to kill the portion of any coral colony or algae that comes in contact with our coral. These digestion-battles between hard corals are very slow in progress. However, through decades of warfare and subsequent adaptation, each species of hard coral has developed its own ‘perfect’ spot on the reef.

Some have become more ‘shade tolerant’ and occupy lower, less competitive areas of the reef, while others have developed longer filaments that make them even more dangerous in battle so they can occupy the top of the reef. Whatever the result, space is still our most prized possession down here. Take a closer look at the borders between corals the next time you swim by a coral reef. You just might be able to see some action!


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