A team involving scientists from the Oceans Institute at The University of Western Australia has devised a unique way of studying the effects of ocean warming on marine life.
The researchers developed a series of electrical ‘hot plates' that can heat up the surrounding water and simulate ocean warming in the immediate vicinity.
The team found that such artificially heated water in the Swan River resulted in greater amounts of marine organisms growing on the warmed plates. This included twice the normal amount of a fast-growing species of sea squirt (Didemnum perlucidum) that can out-compete other species and foul ship's hulls and coastal structures.
The team includes researchers from the Oceans Institute and the School of Plant Biology at UWA, the Australian Institute of Marine Science, and the Natural Environment Research Council in the UK.
The effects of ocean warming are not fully understood. Over the past month, satellite data has revealed that the waters of the Leeuwin Current off WA's coast are three degrees higher than the same time last year and, in a separate discovery, ocean warming is believed to be the cause of coral bleaching at Ningaloo Reef.
"Significant warming has been observed in every ocean, yet our ability to predict the consequences of oceanic warming on marine biodiversity remains poor," said lead researcher Dr Daniel Smale of the Oceans Institute.
"Experiments have been severely limited because, until now, it has not been possible to manipulate seawater temperature in a consistent manner across a range of marine habitats.
"We have developed a tool that can be used to warm the seabed and surrounding seawater to levels that are similar to those encountered during heat waves.
"Our experiments to date have been conducted in the Swan River in Western Australia, where the temperature on hot plates was raised by 1°C for more than a month, and significant ecological responses were observed."
The research involved deploying the ‘hot plate' system in the river at a depth of five metres.
The plates were heated electrically to examine the effect of warming on the settlement and growth of important non-mobile marine organisms, such as seaweeds, sponges and corals.
Dr Smale said the system could be used in any aquatic habitat and could assist researchers investigating marine habitats such as the Abrolhos Islands and Ningaloo, as well as research involving bio-fouling (or marine growths) on ships' hulls and other sea structures.
"These experiments could provide insights into the role of sea water warming on early life stages of marine organisms from within the habitats they live," he said.
"For example, important information on how coral larvae settle and grow during warmer conditions could be obtained."
The results of the group's experiment involving the higher growth rates of Didemnum perlucidum could also have wider effects.
The genus Didemnum includes several invasive species that can cause severe problems by fouling the hulls of vessels and structures such as pipelines and rigs. Some species are also pests for aquaculture operations, such as mussel farming.
"Overall, we observed more fouling on the ‘hot plates' in our experiments, an observation that could have major implications for the multi-billion dollar anti-fouling industry," he said.
Co-investigator Dr Thomas Wernberg, a post-doctoral fellow at UWA and the Australian Institute of Marine Science, said more research was needed into the effects of ocean warming on coastal ecosystems and bio-fouling. He said that the team is seeking further funding to undertake research in Cockburn Sound and elsewhere.
"We're looking to conduct more research on the role of short-term warming on a range of marine organisms in real habitats," Dr Wernberg said.
"This will include research on important habitat formers, such as kelps and corals, and on fouling organisms, which impact coastal structures with economic consequences."
The group's peer-reviewed research paper is available online at the PloS ONE website.
Dr Daniel Smale (UWA Oceans Institute) (+61 8) 6488 2219 / (+61 4) 66 576 587
Janine MacDonald (UWA Public Affairs) (+61 8) 6488 5563 / (+61 4) 32 637 716