The Australian Academy of Science medallist is working to ensure our vulnerable marine environments stay healthy for generations to come.

For Professor Emma Johnston, Sydney harbour is her laboratory and her passion. This underwater world, she says, brings together her childhood love of the ocean, an early fascination with science and the realisation – during her tertiary studies in marine biology – that applied ecology could help her protect the marine ecosystems she so values.

The outcome is an exceptional research career, which includes leading the multidisciplinary Sydney Harbour Research Program at the Sydney Institute of Marine Science, where she works with 35 scientists, along with government and industry, to better understand the threats to Sydney’s prized natural harbour, and helps devise more sustainable management practices.

In parallel, Johnston is actively bridging the gap between research and practice by promoting education and awareness of human impacts on marine systems as a science communicator and by regularly informing public policy as an expert adviser to state and federal government. She’s become a familiar face on TV, presenting Coast Australia on Foxtel’s History Channel. It’s a role that enables her to share with a wide audience the beauty beneath the water’s surface, and the critical role of research in protecting it.

Johnston’s research approach combines ecotoxicology – that is, research into how various toxins affect individual species – with ecology.  The idea is to understand how different species are becoming more vulnerable as their ocean habitats change, resulting from the interaction of multiple stress factors, such as pollution and introduced organisms.

“Ultimately, Australia needs to be able to develop a system of marine estate management that not only preserves existing biodiversity but also the evolutionary potential and integrity of ecosystems as our environment changes.”

Busy harbours, Johnston says, endure the most intense human impacts of any natural system.  Many of the species in Sydney Harbour are introduced, and these more resilient foreign ‘invaders’ have knocked out many indigenous species, particularly as human activity dramatically increases.

It was Johnston who correctly hypothesised and demonstrated that foreign species coming into the harbour were already ‘pre-selected’ as resilient, having survived on chemically treated hulls of ships, and therefore, arrived ready to dominate.

“If you put two species side by side in a clean environment you might predict the native species would be better able to survive – but when you change the environmental conditions with heavy metal contamination, for example, you change the competition,” she says. It’s one of the reasons Sydney’s native lace corals are being displaced by competitors introduced from the Mediterranean.

Recently, Johnston also exposed the emergence of a new, little understood source of widespread contamination: tiny fragments called microplastics that are entering our marine ecosystems.

There’s no doubt, she says, that immediate and medium term challenges to marine environments are unprecedented. At the same time as increased shipping and other human impacts are intensifying localised pressures, rising carbon dioxide levels and warmer temperatures are transforming our ocean systems at the global level.

In 2014, the Australian Academy of Science recognised Johnston’s leadership and her innovative research achievements by awarding her the inaugural Nancy Mills Medal for Women in Science.