Does a reef result from life processes?

Answer 1

Yes, if it is an organic reef. However, contrary to the other answer, reefs are built by many liviing organisms, not just corals (cnidarians), and most coral reefs have a large number of other organisms that contribute significantly to building the reef. Modern coral reefs are composed of 40-80% coral, with the other primary component being calcareous algae. In some instances calcareous algae compose almost all of the reef. Many other organisms inhabit the reef and contribute to its build-up such as bryozoans, encrusting molluscs, and even microbes which often cement particles together. Other types of organisms do build reefs too. Oysters build reefs in some modern oceans.
http://www.sms.si.edu/IRLspec/Oyster_reef.htm

In geologic history organic reefs have been built by a much more varied group of organisms. In the Cretaceous large bivalves known as rudists built reefs. In the Permian large reefs such as the Guadelupe Escarpment where Carlsbad Caverns is located were built by bryozoans, calcisponges, and microbes. In the Pennsylvanian algal colonies known as phylloid algae built bioherms that resembled reefs. In the Devonian stromatoporoids built reefs, and archaeocyathids build reefs way back in the Cambrian.

However, not all reefs are organic. Many reefs, also called shoals, are simply shallow rock or piles of sediment that rise nearly to the surface of the ocean.

Answer 2

Reefs are made today by cnidarians, we call them corals.
But reefs were first build by bacterial mats called stromatolites.
Then came mollusks (rudists) as main builders.
Then came corals.
So, yes reefs have always been a result of living processes.

Answer 3

Coral Reefs are actually huge colonies of microscopic organisms. They can flourish or die out just like anything else.

Answer 4

of course