Helping corals survive

A powerful tool is being developed to help decision-makers address declining marine water quality caused by sediments from land-based run-off.

“Healthy corals provide shelter for different creatures and are a nursery for most commercially harvested fish,” said Christopher Brunner, an AIMS@JCU, Science and Engineering, and ARC Centre of Excellence for Coral Reef Studies PhD student.

“They are sensitive against rising temperatures and ocean acidification – the two major consequences of climate change. However, it is rather difficult to control those.”

Christopher is identifying coral survival thresholds for varying levels of sediment pollution, such as in areas of intensive river run-off and dredging works.

“The main reason I’ve concentrated my research on sediments is because you can control it,” he said. “Most of the sediment that goes into the Reef is created by practices such as farming or dredging.”

According to the Australian Great Barrier Reef Marine Park Authority, sediment pollution is one of the most significant threats to the long-term health and resilience of the Great Barrier Reef alongside climate change, coastal development, and the remaining impacts of commercial fishing.

Land-based run-off can include sediments, nutrients such as nitrogen and phosphorus, and pesticides.

“Funded by the National Environmental Science Program, I am running experiments at the Australian Institute of Marine Science’s National Sea Simulator – exposing corals to different climate conditions expected for 2050 and 2100, and different sediment and light concentrations,” Christopher said.

Three-month-old corals 24 hours after sediment deposition. Image: Christopher Brunner

“Fine sediments can travel up to 80 kilometres in the water column, which is particularly harmful for corals after climate stress and/or when they are still young, especially because most coral species are only reproducing once per year.

“Only by performing multi-stressor experiments can the formative stress limits be identified.”

Located just outside of Townsville, the National Sea Simulator is a world-class marine research facility containing more than 30 seawater processing tanks and capable of pumping in excess of 3 million litres of seawater a day.

It allows scientists to conduct cutting-edge research not previously possible in Australia by providing fine control over environmental variables including light, temperature, acidity/pCO2, salinity, sedimentation and contaminants.

“Later in my PhD, I will be doing a lot of modelling based on putting all of the experiments’ outcomes together, along with what is going on in the Reef now, to get a better picture for risk mapping,” Christopher said.

“This data will be available for authorities so that water quality guidelines can be developed, which will improve the sustainable protection of our vulnerable and valuable Great Barrier Reef.”

Originally from Germany, Christopher’s Masters in Marine Biology took him to China, Antarctica and Australia where he studied interactions of sediments and corals growing along depth gradients before being awarded a prestigious AIMS@JCU scholarship and enrolling at JCU for his PhD.

“My entire studies have focused on sediment and how it impacts different organisms, deep water corals, cold water corals, and now tropical corals,” Christopher said.

“Stopping climate change is extremely difficult since many local, global and economic factors are involved.

“However, by improving the general water quality of the reefs, corals and organisms depending on their shelter will have better survival chances in the future.”

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