Sue-Ann Watson

Who I am

I was born near London in England, quite far from the sea and even further from coral reefs. But I’ve always loved being in, on and by the ocean. I studied biology at the University of Nottingham to gain a broad background in biological sciences and by my second year I knew I wanted to focus on the ocean and become a marine biologist. After finishing my undergraduate degree, I moved to Southampton on the south coast of England where I studied for a Master’s degree in oceanography at the National Oceanography Centre, with a special research project on deep-sea biology. Fascinated by the secrets of the ocean, I gained a place on a research ship to investigate the unknown deep-sea creatures of the Indian Ocean. It was a real privilege to be a part of new scientific discoveries and to encounter species of the deep that no-one had ever seen before, such as giant purple sea cucumbers. I continued at Southampton for my doctorate degree, and also teamed up with the British Antarctic Survey. My research focus moved from the deep oceans to the shallow seas, as I investigated patterns in shellfish evolution from the polar oceans to the tropics. I became particularly interested in studies that would help us understand the effects of global change on marine organisms, so I could help conserve marine ecosystems and ensure their continuance into the future in our rapidly changing world. I am really fortunate to have explored a range of marine habitats around the world and to have worked with many different people along the way.

Where I work

Queensland, where I now work, is home to Australia’s Great Barrier Reef. More than 2,300 kilometres long, this is the world’s largest coral reef system and it comprises over 2,900 reefs covering about 344,400 square kilometres of the Coral Sea. I am based at the Australian Research Council Centre of Excellence for Coral Reef Studies and College of Marine and Environmental Sciences at James Cook University in Townsville, near the middle section of the reef. Field work takes me to research stations such as the Australian Museum’s centre on Lizard Island and James Cook University’s station on Orpheus Island, and I also conduct field surveys on the reef. However, I also spend a lot of time at the aquarium that we have at James Cook University in Townsville. It contains 1.3 million litres of sea water – enough to fill half an Olympic-size swimming pool – and covers 2.2 hectares of space. This is where most of my giant clam and global change research projects are conducted.

What I do

Giant clams are iconic species on coral reefs. The largest giant clam, Tridacna gigas, is the biggest bivalve (two-shelled) animal in the world and can grow up to 1.3 metres long and weigh up to 500 kilograms. Giant clams are the most harvested invertebrate among Pacific Island communities and provide a vital protein source to millions of people. However, the illegal fishing of giant clams in the Indo-Pacific leads to losses of about 300,000 of them per year. These animals are consequently at risk of being overexploited and populations of most giant clam species are in decline. Some species are now extinct in parts of their former range. As a result, all giant clam species are protected under the Convention of International Trade in Endangered Species of Wild Fauna and Flora (CITES) and are listed on the IUCN Red List of Threatened Species^TM. Four giant clam species (Tridacna derasa, T. gigas, T. rosewateri and T. tevoroa) are listed as Vulnerable, which means they face a ‘high risk of extinction in the wild’. But now giant clams also face other threats. I started working on ocean acidification in 2009, when I began to study the effects on marine animals of rising carbon dioxide levels and the consequent acidification of the ocean. Since the Industrial Revolution 250 years ago, we’ve been burning fossil fuels that emit carbon dioxide and other greenhouse gases into our atmosphere. The oceans are in balance with the atmosphere and take up about a third of all this carbon dioxide. However, in the ocean carbon dioxide reacts with water to form an acid. Oceans are already 30% more acidic than they were 250 years ago; if we continue the current trajectory of emissions, they will be 150% more acidic by the end of this century. In addition, this rate of change is so rapid (currently 100 times faster than anything oceans have seen in the past 650,000 years) that we don’t know if animals can adapt fast enough. So now giant clams face not only local pressures such as overexploitation, but also global change, including the acidification and warming of the oceans. Currently, little is known about the effects of global change on giant clams and this knowledge gap limits the capacity to mitigate any impacts. Marine animals like clams, snails, urchins and corals have a large limestone shell or skeleton, but the extra acidity in the oceans hinders shell formation. Giant clams are special, but they may also be particularly vulnerable to global change because as well as having a large limestone shell (up to 230 kilograms) to make, they are very long-lived (up to about 63 years) and take a long time to reach maturity (up to 10 years). These factors could mean that their capacity to adapt to environmental change is diminished compared to that of short-lived, fast-maturing species. My research has found that ocean acidification and ocean warming reduce growth and survival in giant clams. But giant clams are also solar-powered animals. Like corals, they have symbiotic algae within their tissues that provide energy from sunlight – and this means that global change could bring hope for the survival of giant clams. Cloudy, turbid water and sedimentation, which result from activities such as dredging, can reduce light availability. Preserving the quality of water, and its clarity in particular, could be important in providing adequate light for giant clams. Information about giant clams’ light requirements will help managers to improve the resilience of these coral reef icons in a changing ocean and help mitigate the effects of environmental change on them.