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

Competition, Illumination, and the Struggle for Survival of Coral Spat (#56)

Blake D Ramsby 1 , Flore Emonnot 1 , Florita Flores 1 , Soren Schipper 2 , Guillermo Diaz-Pulido 2 , Muhammad A Abdul Wahab 1 , Andrea Severati 1 , Andrew P Negri 1
  1. Australian Institute of Marine Science, Townsville MC, QUEENSLAND, Australia
  2. School of Environment and Science, Coastal and Marine Research Centre and Australian Rivers Institute, Griffith University, Brisbane, Queensland, Australia

Seeding reefs with sexually propagated corals bred in aquaculture is a promising restoration intervention. However, early coral recruits (spat) are vulnerable to overgrowth by benthic algae and maximizing their survival is important for coral restoration. We investigated the optimal light quality and intensity for spat survival with and without benthic algal communities used to induce larval settlement. Firstly, Acropora kenti larvae were settled with benthic algae and then exposed to two light spectra (blue and a full spectrum) at four intensities (5­­­­–160 µmol m-2 s-1) over 12 weeks. Survival was higher by 50% at 5 versus 60 µmol and there was little effect of light intensity on spat size. Secondly, A. spathulata were settled without benthic algae and exposed to 5 or 50 µmol over 12 weeks. When competitors were absent, there was little effect of light intensity on survival and spat grew faster at higher light intensity. These results indicate that competition with macroalgae, here primarily crustose coralline algae, can limit the yield and size of spat produced in aquaculture. Moreover, there is substantial tradeoff when raising coral spat under low light, which limits competitive algae and reduces costs, but leads to smaller spat compared to higher intensity.