An algal mat is a layer of usually filamentous algae on marine or fresh water soft bottoms.

What happens is that the corals are a symbiosis, and they have these little algal cells that live inside them.

So, as climate change proceeds, smaller incremental rises in nutrient levels and drops in fish stocks will flip coral reefs to algal states.

Many coral reefs that were once home to a rich diversity of fish, for example, have become algal or turf ecosystems with very few fish.

These two thresholds interact the more nutrients there are, the less fishing is needed to flip the system into the algal state and the fewer fish there are, the less nutrients are needed.

This is just a simple list of some of the types of poisons that come out of these harmful algal blooms shellfish poisoning,fish ciguatera, diarrheic shellfish poisoning you don't want to know about that neurotoxic shellfish poisoning, paralytic shellfish poisoning.

So you have this little algal forest, and in the size of a laptop you can find more than 100 species of algae, mostly microscopic fit hundreds of species of little animals that then feed the fish, so that the system recovers.