Cold-Water Corals

Antarctic coral Balanophyllia malouensis, photo by Dann Blackwood, USGS

So what is a cold-water coral and how are they different from regular corals? If you break it down to the basics there are two types of coral on this planet - one type of coral that has a symbiotic algae present in its tissue (zooxanthellae) that photosynthesizes, and one type that doesn't. The corals you have probably heard about and snorkeled or SCUBA dived around are likely those that have the symbiotic algae. These corals are limited in where they can grow, because these algae need warm waters and lots of sunlight to be able to photosynthesize, so you tend to only find them in warm tropical waters such as the Great Barrier Reef or Indonesia. As the algae photosynthesize, they give energy to the coral they live inside, so that coral can grow fast.

The corals this lab works with are different, they don't have this symbiotic algae, and so can live, quite literally, anywhere. These corals can live in complete darkness and cold waters, can be found in the deepest depths of the oceans, caves and temperate fjords and even in polar waters. Cold-water corals get all of their energy from the food they eat, rather than photosynthesis, so they grow much slower, some even live up to thousands of years.

As we learn more about the deep-sea we're beginning to realise that these corals are not only found everywhere in every ocean, but they also can host whole ecosystems, just like their shallow water counterparts. Like in shallow water too, these corals are threatened by man's activities, only in the deep-sea it's harder for everyone to see it happening. Bottom trawling has by far the biggest impact on cold-water corals, literally tearing them from the sea bed and bringing them to the surface. Climate change too is likely to affect corals at the deepest depths of the oceans - these corals thrive in frigid temperatures and water that is a less basic (so more acid) than regular seawater - so any changes in these through global warming and ocean acidification is going to have affects. We don't know how bad those affects will be, but there are lots of scientists out there trying to find out, including those from this laboratory!