Corals and Ocean Indicators

As we have seen in past blog posts, corals are extremely sensitive to changes in sea temperature, salinity and acid levels. This is normally seen as a negative, however there is an upside. The coral can be used as an indicator as to areas affected by climate change. The reason that they are so good at being ocean health indicators is that they are found worldwide, especially in the tropics, which are particularly susceptible to climate change. When there has been an increase in the ocean temperature, the corals will show this through bleaching. This is because when temperatures get too high, the bacteria that gives coral its colour will leave the coral as it cannot stand the temperature. The more bleaching that has taken place, the higher the relative temperature of the ocean will have become. Corals will show an increase in acidification by a reduction in calcium carbonate in the skeletons of the corals. The more CO2 that is dissolved into the ocean, the lower the amount of calcium carbonate corals will have. There is an inverse relationship. There are some issues with using coral to find out about ocean water quality. For example, changes in coral reefs may not represent global changes, and may just show local variations, and don't show the bigger picture. The good thing about them is that they are so well monitored that any changes that occur are usually observed and recorded on a large scale.

So we can see that corals can be used to determine ocean health, but what other methods can be used to evaluate the health of oceans?

One such method of determining ocean health could be by examining diatoms. These can be used to show water quality. This is because only certain diatom species will live in certain conditions. So if they are found in an area, then you can establish what the conditions in the ocean when the diatoms were alive. The sudden disappearance of a species will tell us something has changed.Diatoms are useful for this as they are extremely abundant, have large distribution and have a vast number of

species, which means they are easily identifiable. This means that diatoms are extremely useful at

telling us about ocean changes. They aren't quite as specific as corals at identifying changes, but used in conjuncture with corals they could be extremely useful.

An example of a diatom, which like zooxanthallae is microscopic.

Other indicator species can be used to show ocean quality. This can be invertebrate species such as caddis flys and nymphs that can be found in certain conditions. These invertebrate indicator species can be harder to sample than coral for example, as they require collection and are harder to count.

I think that coral are a fantastic indicator of climate change. The sensitivity to a variety of different factors means that they provide excellent detail to explain what is happening to the oceans. Used in conjecture with invertebrate indicators and diatoms, a clear picture of the oceans can be determined.