Short Talk (7,5 mins) Australian Marine Sciences Association 2022

The effects of a spatial turbidity gradient on Acropora tenuis in Exmouth Gulf, Western Australia (#99)

Adi Zweifler 1 , Nicola Browne 2 , Oren Levy 3 , Renae Hovey 4 , Mick O'leary 1
  1. School of Earth Sciences and the Oceans Institute, University Of Western Australia, Crawley, WA, Australia
  2. Curtin University, Bentley, WA, Australia
  3. The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel
  4. School of Biological Sciences and the Oceans Institute, University Of Western Australia, Crawley, WA, Australia

Western Australia coral reefs have been comparatively undisturbed compared to the Great Barrier Reef, but over the last 10 years increased frequency of cyclonic and bleaching events have had a considerable negative impact on ecosystem stability. The coral reefs of Exmouth Gulf, located adjacent to Ningaloo Reef, are also exposed to high and variable turbidity events and elevated SSTs. Yet, coral communities appear stable through time supporting the growing evidence that coral reefs situated in naturally turbid waters are less prone to bleaching than their clear-water counterparts. To investigate the potential of these reefs to function as coral refugia or recruitment source, we monitored coral physiology properties and analyzed stable isotopes of Acropora tenuis across a turbidity gradient from Ningaloo to Exmouth Gulf. As expected, we found an increase in δ13C values moving from turbid to clear-water environment suggesting increased autotrophy levels, however, higher δ15N values were also found with the same trend, implying higher heterotrophy in the clear-water environment compared to the turbid. This latter finding goes against the broader consensus of higher heterotrophic levels in turbid reefs proposing that corals at Exmouth Gulf possess other traits enabling their survival in chronic marginal environmental conditions.