‘Red tide’ algal blooms (Noctiluca scintillans)
Southeast Australia has been identified by scientists as a
climate change hotspot due to the southern penetration of the East Australian Current. As a result,
algal blooms may become more common as Tasmania’s coastal waters experience prolonged marine heatwave conditions (persistent or continual above average ocean temperatures).
Algal blooms are a natural occurrence, and are sometimes called red or pink tides because the blooms can turn the water red. Not all algal blooms are harmful, with many species acting as a major source of energy for animals in the marine food web. Harmful algal blooms (HABs) form when colonies of tiny organisms grow and reproduce at a rapid rate.
The most common cause of red tides in Tasmanian waters is the marine dinoflagellate Noctiluca scintillans, which can cause bioluminescent light displays at night. Noctiluca has also been linked to numerous bioluminescent displays in South Australia and New South Wales.
Noctiluca scintillans ‘red tide’ bloom off the coast of Bruny Island (Source: Mike Santek)
There are currently no available scientific studies linking Tasmanian aquaculture with an increased prevalence of Noctiluca scintillans blooms or red tide events. Scientific studies investigating and mapping the range of expansion of Noctiluca scintillans have not directly attributed aquaculture operations as contributing mechanisms (see Further Reading and References sections).
Noctiluca is
not regarded as toxic to humans, but it is recommended to swim in clean, clear water. If you can see foamy or abnormally coloured water it could be an algal bloom, which may cause skin irritation upon contact. See the Department of Health for human health advice on algae in Tasmanian recreational waters.
References
Johnson, C. R., Banks, S. C., Barrett, N. S., Cazassus, F., Dunstan, P. K., Edgar, G. J., Frusher, S. D., Gardner, C., Haddon, M., Helidoniotis, F. & Hill, K. L. (2011). Climate change cascades: Shifts in oceanography, species' ranges and subtidal marine community dynamics in eastern Tasmania.
Journal of Experimental Marine Biology and Ecology, 400(1-2), 17-32.
McLeod, D. J., Hallegraeff, G. M., Hosie, G. W., & Richardson, A. J. (2012). Climate-driven range expansion of the red-tide dinoflagellate Noctiluca scintillans into the Southern Ocean. Journal of Plankton Research, 34(4), 332-337.
Ridgway, K. R. (2007). Long‐term trend and decadal variability of the southward penetration of the East Australian Current. Geophysical Research Letters, 34(13).