Killer algae

From left to right: Caulerpa peltata, Caulerpa racemosa and Hypnea pannosa collected and photographed at Ningaloo Reef by Fred Gurgel.
Image: Fred Gurgel


23 May 2010
To the untrained eye, it looks like a bunch of grapes, but the University of Adelaide's Dr Carlos Frederico "Fred" Gurgel knows this alga could be a killer.
"Caulerpa racemosa belongs to the same genus as Caulerpa taxifolia, which is one of the top 100 invasive hence ecologically-aggressive species in the world," Dr Gurgel says.
"There are several different varieties of Caulerpa racemosa – the morphology varies widely, and wildly – and one of these varieties has now being introduced in Adelaide, in South Australia, as well, which suggests that this genus, more than others, is prone to producing species with ecologically-negative impacts," he says.
"Caulerpa taxifolia introduced populations grow very fast. They smother temperate reefs and displace the local species, other algae and animals, everything. The end result is a mono-culture: fields of Caulerpa and almost nothing else. "
Dr Gurgel has been awarded a significant Australian Research Council grant to study Caulerpa. He will compile a DNA barcode database of the approximately 30 Caulerpa species found in Australia plus species from other countries so that any new introductions can be identified promptly and before populations become invasive.
The project will also simulate, in the laboratory in aquaria systems, scenarios of climate change in the marine environment in order to test the effects of differing values of temperature, salinity, acidity, light and nutrients on the these algae.
"We want to pinpoint exactly which physical conditions weaken the plant the most, use models to predict when those environmental conditions will occur, and implement eradication mechanisms to coincide with those conditions. This will provide us with the information to help us eradicate the invasive species more effectively and therefore also more cheaply," he says.
The project will also track the origin of the invasive populations in Australia using techniques of biogeography and population genetics.
"Australia is probably the richest place for species in this genus," Dr Gurgel explains.
"The species in the tropics are native. It is only when they are introduced into temperate, cold waters in New South Wales and South Australia that they become invasive, but as yet we don't understand how they are spreading to these areas," he says.