Substrata of any origin where ≥ 80% of the substratum surface is hard (i.e. acoustically or optically hard and/or stable enough through time to be able to maintain a reef ecosystem of some form).
Substrata of any origin where ≥ 80% of the substratum surface is hard (i.e. acoustically or optically hard and/or stable enough through time to be able to maintain a reef ecosystem of some form).