This image shows the lower shore of Belle Greve Bay after ormer (abalone) gatherers have turned over boulders looking for the elusive mollusc. All the pale boulders have been overturned and left upended. Many marine biologists visiting Guernsey from the UK have commented on the damage done to the shore by shore gatherers not returning boulders back to their original position after turning them over to look for the ormer. The tops of the boulders are covered by algae and particularly the pink crustose coralline algae, which issues pheromones which attract settling ormer, Haliotis tuberculata, larvae. The base of boulders are covered in many sessile invertebrate species including spirorbid tubeworms, bryozoan colonies, and ascidian colonies. When boulders and cobbles are turned over and not returned to their original position the algae that were growing on the top die and the invertebrate colonies from the base of the rock die too. The boulder quickly becomes colonised by opportunistic green algae and gradually over time and through succession a more complex community of species adheres to the boulders. If the boulders are turned over too often and the shore suffers too much disturbance macroscopic species diversity deceases. There is a hypothesis that intermediate disturbance allows for the greatest species diversity.
File No. BG 210307 30-890
Copyright©RLLord
fishinfo@guernsey.net
Boulders turned over BG 210307 30-890

This image shows the lower shore of Belle Greve Bay after ormer (abalone) gatherers have turned over boulders looking for the elusive mollusc. All the pale boulders have been overturned and left upended. Many marine biologists visiting Guernsey from the UK have commented on the damage done to the shore by shore gatherers not returning boulders back to their original position after turning them over to look for the ormer. The tops of the boulders are covered by algae and particularly the pink crustose coralline algae, which issues pheromones which attract settling ormer, Haliotis tuberculata, larvae. The base of boulders are covered in many sessile invertebrate species including spirorbid tubeworms, bryozoan colonies, and ascidian colonies. When boulders and cobbles are turned over and not returned to their original position the algae that were growing on the top die and the invertebrate colonies from the base of the rock die too. The boulder quickly becomes colonised by opportunistic green algae and gradually over time and through succession a more complex community of species adheres to the boulders. If the boulders are turned over too often and the shore suffers too much disturbance macroscopic species diversity deceases. There is a hypothesis that intermediate disturbance allows for the greatest species diversity.
File No. BG 210307 30-890
Copyright©RLLord
fishinfo@guernsey.net
Boulders turned over BG 210307 30-890