Colonising biota was assessed following the collection of one crate from each site (Poole Harbour or Hamble Harbour) at 3-, 6- and 12-month intervals and transported to the lab the same day (24 replicates of each mortar mix). High resolution photographs were taken of each block side (Sony A7R3 CDC camera, Sony FE 24-70mm zoom lens). The percentage cover and numeric counts of organisms was visually estimated to species level wherever possible, while biota from the block ends and textured face was discounted.