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Tuesday, January 19, 2021

Invisible hitchhikers alert scientists to ocean changes

A University of Newcastle researcher has helped to uncover new information about marine microbes from the Great Barrier Reef.

Dr Mark Brown was part of a research team that found the East Australian Current (EAC) was carrying the invisible hitchhikers, which take the form of bacteria, fungi, algae and plankton, down to Tasmania for the first time in history.

The organisms are small in size but large in impact. They make up around 98% of the ocean’s biomass and control the supply of some nutrients vital to all life.

These microbes are responsible for controlling the ocean’s health and producing around half of the oxygen we breathe.

The research team, which included representatives from Queensland University of Technology (QUT), University of Technology (UTS) Sydney, Macquarie University and the CSIRO, put together a paper on the impacts of this environmental shift.

Dr Brown said the EAC was an important part of the ocean’s ecosystem.

“The EAC plays host to millions of microbes and other tropical organisms hitching a ride down the coast,” he said.

“These including both tiny plants capable of photosynthesis, known as phytoplankton, as well as microbes that consume the carbon these plants produce.”

Over 60 years, the EAC has experienced a 350 kilometre southerly expansion of its warm water flows into the Tasman Sea.

Dr Brown added that the current was becoming stronger and travelling further south than ever before, which would have major consequences.

“More strength and intensity in the EAC means more north-based flora and fauna infiltrating temperate seas, impacting the environment they’re displacing,” he said.

“This has a ricochet effect on the broader ecosystem.”

Research has shown that these changes have led to sea surface temperatures warming at nearly four times the global ocean average.

An aerial view of Queensland’s Great Barrier Reef.

This has resulted in increased marine heatwaves, making the iconic eastern coastline a ‘climate change hotspot’.

In 2018, Dr Brown and colleagues established an unprecedented microbial baseline in Australian oceans to measure the effects of climate change and human activities.

With this new information about the EAC environment, the team hopes to continue its work to map other important ocean currents and their impacts.

“This is the first time microbes have been used as indicators of ocean currents, and we hope it will become a permanent feature in EAC research,” Dr Brown said.

“Whilst we can’t easily implement strategies to manage microbes because of their small size and enormous abundance, it’s important when looking at future predictions of climate change and the ecosystem to understand the impact of microbes as part of a bigger picture.”

For more information, you can read Dr Brown and colleagues’ full paper here.