This page will help you tell the difference between what live vs dead coral looks like. With rising ocean temperatures, damage from tourism, and overfishing, it's estimated that 25%-50% of the world's corals reefs are already dead, up to 75% have suffered bleaching events, with the remainder at risk. Finding a live healthy coral reef is actually becoming rare.
Many people have their first snorkeling experience at popular tourist locations like Hanauma Bay, Oahu in Hawaii, or Trunk Bay in St. John. Since most of the coral at these locations is dead many new snorkelers may not realize what they are missing, or what live vs dead coral looks like.
Coral is like the forest of the sea, except it is not a plant, it is a colony of animals (called polyps).
These little animals live in a symbiotic relationship with algae, and they build tiny calcium stone houses for themselves. And all of these houses get stacked on top of each other and form larger structures like apartment buildings or termite hills. These can take many different shapes that might look like hard rock boulders, or branches. They can also form flexible structures that can move with the currents of water. In the closeup picture above you can see the structure of their calcium houses. The animals are withdrawn inside. Many corals only come out at night to feed, although there are many exceptions.
For example the first picture below is a leather coral (partially bleached), and the animals are retracted inside. The next picture shows the animals out feeding.
Here is an excellent article that explains coral animals.
It's sometimes hard to think of corals as animals, but they are. They often feed on zooplankton that they pull inside and digest in stomachs. Aquarium owners often feed their corals with brine shrimp.
Check out the pictures below. These are just a few samples of some common corals that can be seen in the Pacific and Atlantic oceans.
Look at the color and shape. Old dead corals will be broken down, and lack a healthy color, and are sometimes covered in algae.
that have been bleached from rising ocean temperatures turn white when the symbiotic algae leaves the coral. In some rare circumstances these may recover if the algae returns.
Dead Or Dying Elkhorn Coral
Healthy Elkhorn Coral
Dead, Dying Or Damaged Brain Coral
Healthy Brain Coral
Unhealthy Or Dead Sea Fan Corals
Only the center purple fan looks relatively healthy in the picture below. Soft corals like these also have tiny polyps that feed on microorganisms in the water.
Healthy Fan Coral
Dead Or Unhealthy Staghorn Coral
Healthy Staghorn Coral
Dead/Bleached Table Coral
Healthy Table Coral & Some Bleached
Unhealthy/Bleached Boulder Coral
Healthy Boulder Coral
Healthy & Unhealthy Cauliflower Coral Side By Side
Algae Sometimes Takes Over A Dead Reef
If a coral reef is damaged and dies, often the reef becomes covered in algae like in the picture below.
Corals clean the oceans, provide habitat, and are food to countless other species. And we are seeing a global mass extinction on a scale that is terrifying for not only ocean health, but human fisheries. Without coral reefs, human jobs and food sources are rapidly declining.
So the next time you are out snorkeling, and see some beautiful fish, like in the pictures below, make sure and look behind at the corals, and take note of its condition. The corals are 95% dead in these pictures. Without corals, you can expect the oceans entire ecosystem to be stressed and declining.
Helping prevent the continued destruction of coral reefs is pretty easy on a personal level at least
Caribbean Fish, Creatures & Corals ID Books