Discovering the secrets of the sea | Stephanie Gardner

about the storyteller

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Dr. Stephanie Gardner is a marine biologist, coral reef researcher, and woman in STEM. Being at the center of climate change science, Stephanie sees the impact in real ways every day.

Here's a little bit about her passion, her work, and her life in the ocean. You can also follow her envious adventures and research on Instagram @stephggardner.


Editor's note: Stephanie uses British English in her story, meaning you'll see 's' in place of 'z' and other variants. Don't freak out, this is a culture difference and it's a good thing. She was also kind enough to include references to for validation and further reading.


I’m sure many of you have heard about the global mass coral bleaching event we recently experienced between 2015-2017, which caused 93% of the Great Barrier Reef to turn white (Hughes et al. 2017). Not only is this statistic alarming, but we also experienced the first consecutive years of bleaching events ever recorded. It is hard to understand or contextualise this devastation and the wider impact of this event without seeing it first-hand.

Scleractinian or ‘reef-building’ corals comprise of a symbiosis between the animal host and the dinoflagellate algae, known as Symbiodinium sp. This relationship exists because the host provides protection, living space and nutrients (up to 95%), while the algae provides oxygen, food (such as glucose and amino acids) and eliminates carbon dioxide through photosynthesis.

An aerial view of my experimental set up at Heron Island Research Station, showing two different species of corals to be used in a thermal stress experiment.

An aerial view of my experimental set up at Heron Island Research Station, showing two different species of corals to be used in a thermal stress experiment.

Corals require particular conditions to exist, and any alteration in these (such as increased seawater temperatures) can lead to coral bleaching which is characterised by the expulsion of algal symbiont from the coral host, giving the noticeable white or bleached colour. If the environmental conditions return to normal, the host can be repopulated with the algal symbiont and ‘recover’ from bleaching. However, if these conditions remain for an extended period of time, the coral host can starve and eventually this leads to death.

Why should we worry about losing coral reef ecosystems? Reef building corals, are major contributors to the structure of tropical marine ecosystems worldwide and are responsible for the three-dimensional framework of coral reefs.

They are known for their high biological diversity and productivity and are often referred to as the ‘rainforests of the sea’. They also provide a home for ¼ of all marine species – considerable given they are they are estimated to cover less than 0.1% of the ocean’s surface area.

Globally, many people depend upon the reef for their livelihood and over 1/3 of the world’s population live within 100km of the ocean. Coral reefs represent crucial sources of income and resources. The Great Barrier Reef is worth $56 billion to Australia’s economy - valued at more than 12 Sydney Opera Houses (Deloitte Access Economics (2017)), providing more than 64,000 jobs nationally.

So how come not all corals bleach with warmer seawater? How do corals protect themselves from coral bleaching? That’s where my research and interests are. Not unlike humans, corals also produce and use antioxidants to help protect themselves by neutralising damaging reactive oxygen species. One of the causes of coral bleaching may stem from a build-up of these free radicals, which overwhelms the corals antioxidant abilities, a process commonly referred to as ‘oxidative stress’.

Two coral species that were fragmented into smaller parts; the pink corals are Stylophora pistillata and the yellow are Acropora millepora – both common in the Indo-Pacific region.

Two coral species that were fragmented into smaller parts; the pink corals are Stylophora pistillata and the yellow are Acropora millepora – both common in the Indo-Pacific region.

No doubt you’re familiar with the health food and beauty industries promoting the use of and eating foods rich in antioxidants such as vitamin C and E, coenzyme Q10 and beta-carotene. All the more reason to induldge in chocolate which is full of antioxidants. One compound that has been shown to have an antioxidant function in corals is a sulphur compound called dimethylsulphoniopropionate – or DMSP for short.

DMSP plays a key role in marine biogeochemical and ecological processes. It contributes to the global sulphur cycle and is involved in the transfer of sulphur through the marine food web. Globally, more then 1 billion tonnes are produced by marine photosynthetic organisms per year.

A fraction of this DMSP is then broken down into dimethylsulphide (DMS) which then diffuses into the atmosphere. Here, it is oxidised to form aerosol particles which increases the formation of clouds, potentially influencing local and regional climate. Cool, huh? You know the smell of low tide? Or the smell of seaweed? Or maybe even the smell of air exposed corals? This ‘smell of the sea’ is DMSP.

A technique used to estimate the health of a coral where a pulse of light is used to provide a fast assessment of the overall photosynthetic state.

A technique used to estimate the health of a coral where a pulse of light is used to provide a fast assessment of the overall photosynthetic state.

During my PhD, I investigated the antioxidant role of DMSP in coral reef systems under physiolgical stress. My ultimate goal was to determine whether DMSP plays a role in protecting the coral host from oxidative stress once a threshold of stress has been reached within the coral.

To do this, I spent months on an isolated island (at Heron Island Research Station) in the southern Great Barrier Reef surrounded by coral; conducting field work, collecting data and running experiments. It wasn’t all fun and games – my work needed to be processed and analysed in the laboratory which consisted of hours upon hours, late nights, working overtime and running and re-running experiments. But I would not have it any other way.

You know you’re going to have a good day when you get dressed for work in a wetsuit – not a business suit. I legitimately have the best job in the world.


References:

Deloitte Access Economics (2017) At what price? The economic, social and icon value of the Great Barrier Reef. In: O’Mahony J, Simes R, Redhill D, Heaton K, Atkinson C, Hayward E, Nguyen M (eds), Brisbane, Australia

Hughes TP, Kerry JT, Álvarez-Noriega M, Álvarez-Romero JG, Anderson KD, Baird AH, Babcock RC, Beger M, Bellwood DR, Berkelmans R, et al. (2017) Global warming and recurrent mass bleaching of corals. Nature. 543:373-377

Photos provided courtesy of Dr Matthew Nitschke.