Speed Presentation 2024 Australian Marine Sciences Association Annual Meeting combined with NZMSS

Barrens Rock (#213)

Michael J Kingsford 1 , Maria Byrne 2
  1. Marine Biology and Aquaculture, College of Science and Engineering, James Cook University, Townsville, QLD, Australia
  2. Marine and Developmental Biology, , The University of Sydney, Sydney, NSW, Australia

Abstract: Temperate reefs of New South Wales are dominated by two habitats, kelp forest and urchin grazed barrens.  The dominant habitat-forming alga, that characterizes kelp forest, is Ecklonia radiata. Centrostephanus rodgersii is native to NSW. Further, it is recognised as the most influential determiner of barrens habitat, due to  their grazing activity that results in the appearance of a ‘barren’ habitat that is devoid of macro algae.  An increase in numbers of C. rodgersii in Tasmania and resultant changes in habitat, particularly the loss of laminarian algae, has resulted in the vilification of urchins.  Here we argue that a mosaic of habitats, including both barrens and kelp forest is critical to the health of temperate reefs.  Many species of fishes abound in barrens that do not frequent Ecklonia forest.  Further, many species (e.g. labrids) use both habitats, foraging and or hiding in both.  Both habitats provide a complementary platter of food to predators.   Amphipods reach up to 50 per 100g in kelp  and the large gastropod Turbo varies between 1 and 10 per m2, with low numbers in barrens (< 0.5 per m2).  In contrast, barrens support greater numbers of  large and small gastropods providing an important food resource.