Coral interactions more complex than ever suspected. Dr Tracy Ainsworth's research is changing our understanding of the life of the tiny coral animals that built Australia's iconic Great Barrier Reef.

Her work comes at a critical time for the future of coral reefs-threatened by a warming ocean and by coral bleaching.

Just three years out from her PhD and now at James Cook University, Tracy has already demonstrated that the interactions between corals, their communities and their environment are far more intricate and subtle than we ever imagined.

She has shown, for instance, that bacteria as well as algae play a significant role in the life of the coral and in how it responds to changing temperatures. She has also found that coral bleaching is a far more complex process than previously thought.

And she's done so by applying skills in modern cell biology which she picked up working in neuroscience laboratories.

Her achievements have won her a $20,000 L'Oréal Australia For Women in Science Fellowship which she will use to study the low light, deep water reefs that underlie tropical surface reefs at depths of 100 metres or more.

Coral calling

Tracy has always been a beach girl. "I love oceans and beaches and reefs."

Growing up on the beaches of New South Wales, she has spent almost her entire life playing, learning, studying and working by the sea.

Now she is giving something back-her research is changing how we understand and manage coral reefs.

When she moved to James Cook University in Townsville to study marine biology, Tracy first worked on prawns and aquaculture. But she became increasingly interested in how marine creatures cope with stress and disease and came to admire coral.
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"This small, simple animal builds large and beautiful structures that attract life and create a rich ecosystem. And the world's reefs are also important to the human communities who live near them: for food, for protection and for tourism," she says.

In surface reefs, the coral polyps-relatives of jellyfish and anemones-that construct the reef's limestone scaffolding form a symbiotic relationship with single-celled algae called dinoflagellates. In return for sugars from their photosynthesis, the colourful algae gain a home. Bleaching indicates the algae have left home.

Coral home for bacteria too.

But the reef also supports communities of bacteria living in a mucous coating which the polyps secrete to protect themselves from wave action and the scouring of sand and sediments. The mucous is an ideal home for bacteria, and an environment the polyps can manipulate to their advantage by means of nutrients and inhibitors. And the bacteria themselves provide another layer of protection, producing chemical defences against less benign infective bacteria and microbes that can cause disease. The interaction with these bacteria seems to be important for corals.

In deciding to study the coral bacteria, however, Tracy realised she needed the skills and sophisticated tools of modern cell biology. So she went south, to Brisbane and worked as a research assistant in two different neurobiology laboratories, acquiring the techniques of modern molecular biology and genomic research.

Armed with these skills, she returned to the reef and to the Australian Research Council Centre of Excellence for Reef Studies at James Cook University to investigate the diversity of the bacterial communities by sequencing the species involved and using fluorescent tags to pick them out with a confocal microscope. That allowed her to study what happened to the bacterial communities in times of stress, such as when water temperature began to rise.

Conventional wisdom held that symbiotic algae began to abandon their coral at a threshold temperature of about 32°C, leading to bleaching. But Tracy found things were much more complex, and the coral more sensitive. "Coral begins to respond at temperatures much lower than the bleaching threshold. For instance, at temperatures below 30°C you start seeing programmed cell death in the coral polyps, and the symbiotic relationships with the bacteria and algae begin to break down."

She will use the Fellowship to study the low light, deep water reefs that underlie tropical surface reefs at depths of 100 metres or more.

This is a world far removed from the bright, colourful, sunlit environment we associate with coral. It's a place with little or no photosynthesis to provide the energy for reef construction and maintenance. But the biological communities there are still diverse, and still include algae. They may even serve as refuges from which devastated shallow reefs can repopulate.

"The low light environment is really very different. These are large reef structures and we know very little about how they function."

Tracy has taken her techniques and analyses to reefs in different environments worldwide. During a six-month stint at Tel Aviv and Haifa universities in Israel, she was able to show that the annual summer coral bleaching in the Mediterranean was not due to disease and infective bacteria, as had been supposed. In fact, no bacteria were involved. She has also worked on reefs in Hawaii, and the extremely hot and saline Red Sea.

"The fact that there is so much diversity in the ocean gives us hope for the future. But such diversity doesn't change the need for us to minimise our impact. It highlights the importance of protecting it."

Fortunately, her seaside work environment is one to which she has no hesitation in taking her two-year-old daughter and, when it arrives soon, her second child. One suspects another generation of beach children is being launched.