Standard Presentation Australian Marine Sciences Association 2026 Conference

From Rare to Recurrent: Implications of Increasing Noctiluca scintillans Blooms (139620)

Claire H Davies 1 , Gustaaf Hallegraeff 2 , Andrew Bissett 1 , Frank Coman 3 , Ruth S Eriksen 1 4 , Sahan A Jayasinghe 1 , Felicity R McEnnulty 1 , Anita Slotwinski 3 , Mark Tonks 3 , Julian Uribe-Palomino 3 , Jodie van de Kamp 1 , Matthew C Smith 1 , Anthony J Richardson 5 6
  1. CSIRO, Hobart, TASMANIA, Australia
  2. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
  3. CSIRO, Queensland Biosciences Precinct, St Lucia, Queensland, Australia
  4. Australian Antarctic Program Partnership, Institute of Marine and Antarctic Studies , Hobart, Tasmania, Australia
  5. Centre for Biodiversity and Conservation Science , University of Queensland, Brisbane, Queensland, Australia
  6. School of the Environment, University of Queensland, St Lucia, Queensland, Australia

The heterotrophic dinoflagellate Noctiluca scintillans has increased its geographic range in Australian waters over recent decades. Once rarely observed, bioluminescent displays are now frequent events in southeast Australia and Tasmania. Long‑term data (2008-2026) from the Integrated Marine Observing System (IMOS) National Reference Stations and Australian Continuous Plankton Recorder Survey, combined with historical observations, reveal some regional increases in abundance, and strong latitudinal and seasonal patterns. The timing of blooms is closely linked to temperature, with frequent blooms in autumn and winter in tropical Australia, in spring in the subtropics, and in summer in temperate waters. Climate‑driven ocean warming, combined with sustained prey availability, have enabled Noctiluca to persist year‑round in temperate regions and hence expand its distribution. Other mechanisms could also have contributed to this expansion, including coastal eutrophication, transport via ship ballast water, and the increased southward warm‑core eddy activity associated with the East Australian Current. Although impacts on copepod abundance appear limited, the increasing frequency and intensity of Noctiluca blooms may have important ecological and socio‑economic implications. Whilst not considered a harmful algal bloom species, extreme abundances can disrupt pelagic food webs, elevate ammonia concentrations, reduce oxygen availability, and pose risks to finfish aquaculture, shellfish quality, tourism, and fisheries. Continued monitoring is therefore essential.