Standard Presentation (15 mins) Australian Marine Sciences Association 2022

Microhabitat selection in sponges and their interactions with other benthic organisms on a coral reef (#97)

SAUL S. GONZALEZ MURCIA 1 , Merrick M. Ekins 2 , Thomas T. Bridge 3 , Christopher C. Battershill 4 , Geoffrey G. Jones 5
  1. Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia
  2. Invertebrates Collection, Queensland Museum, Brisbane, Queensland, Australia
  3. Invertebrates Collection, Queensland Museum, Townsville, Queensland, Australia
  4. Environmental Research Institute, Division of Health, Engineering, Computing and Science, University of Waikato, Hamilton, Waikato, New Zealand
  5. College of Science and Engineering, James Cook University, Townsville, Queensland, Australia

Microhabitat choices and contact interactions among sedentary organisms can be a major determinant of benthic communities on coral reefs. Sponge substratum choices and interactions with other benthic organisms are poorly understood. We quantified sponge substratum preferences and interactions along depth (5,10 and 15m), landward and seaward exposures, and reef aspect on coastal coral reefs in Kimbe Bay, Papua New Guinea. A high proportion (55%) of sponge colonies occurred on calcium carbonate rock, and coral rubble (9%) even though these represented a small proportion of the available substratum (10% and 4% respectively). We recorded 30,413 interactions of sponges with the 8 major benthic taxa. Sponges primarily interacted with corals (~35%), algae (~30%) and crustose coralline algae (CCA) (~26%) that represented ~46%, ~21% and ~11% of the substratum cover respectively. Stand-off was the most common interaction type with 72% (21,968). When overgrowth occurred, sponges were winners over corals (92%), CCA (81%) and macroalgae (64%). Thus, sponges avoid other biological substrata by preferentially settling on CaC rock, but when they do encounter algae and corals, they frequently overgrow their space competitors.