Poster Australian Marine Sciences Association 2022

Decadal trends in surface elevation and tree growth in mangroves of Moreton Bay, Queensland, Australia (#504)

Vicki Bennion 1 , John Dwyer 1 , Catherine E Lovelock 1
  1. School of Biological Sciences, The University of Queensland, St Lucia, QLD, Australia

Mangroves provide important ecosystem services including coastal erosion, soil carbon sequestration and habitat provision. Their persistence with sea-level rise depends upon their capacity to increase their soil surface elevation at a rate comparable to relative sea-level rise. Both sediment and organic matter contribute to gains in soil surface elevation, but their importance may vary with climate over long time scales. Here we analyse variation in surface elevation, surface accretion and mangrove tree growth over 15-years in Moreton Bay, Queensland, that spans variation in the El Nino/La Nina (ENSO) cycle which strongly influences rainfall and sea level in the region. Piecewise structural equation models were used to assess the effects of biotic and environmental factors on annual surface elevation increments identifying variance with intertidal position, a site trend consistent over 15 years. While surface accretion and tree growth were both positively influenced by rainfall, surface elevation was not, and thus high levels of compaction of the soil profile in these years is inferred. Therefore, climate variations affect mangrove tree growth, but surface elevation trends were influenced by variation in environment. Further research into tipping points with extreme La Nina events will help clarify the future of mangroves within Moreton Bay.