Giant clams: turning up the heat

The overall aim of this project is to prevent future extinction of giant clams by determining and understanding the impacts of climate change over the next 50 to 100 years on these long-lived species while there is still time to employ effective management practices and conservation solutions.

Giant clams are the most harvested invertebrates among Pacific island communities and serve as a vital source of protein for millions of people. Several species are now extinct due to overexploitation. With oceans now 30% more acidic than they were 250 years ago, there is a lack of adaptive management response to protect these key megafauna.
Determining any potential for light to ameliorate the negative effects of global change on giant clams through their relationship with symbiotic algae will help managers build resilience of giant clam species in a changing ocean and help mitigate the effects of environmental change on these coral reef icons.

Absorbing a third of all human carbon dioxide (CO₂) emissions, our oceans will become 150% more acidic than 250 years ago by the end of this century. Our oceans are now changing 100 times faster than at any time in the past 650,000 years and the process of ocean acidification is one of the primary climate change concerns for marine life, with demonstrated negative impacts on calcareous species. Rising temperatures are also detrimental to marine organisms, particularly in the tropics where warming can cause bleaching of symbiotic algae in giant clams.
Giant clams are the largest shelled bivalves on the planet and may be particularly vulnerable to climate change as they have a large shell to calcify (up to 230 kilograms), are very long lived (up to 70 years) and take a long time to reach maturity (up to 12 years). Starting in 2012, I have undertaken the first research into the effects of climate change on giant clams. I was awarded an Ian Potter Small Science Grant in 2012 for a pioneering research project to determine the effects of warming and ocean acidification on giant clam survival and growth.

The aims and objectives of this project are to:

• Determine effects of ocean acidification, warming and light on giant clam survival, linear growth and mass.
• Determine effects of ocean acidification, warming and light on the shell mass, calcification rate and shell structure of the giant clam in collaboration with other scientists from US/UK.
• Determine effects of climate change and light on giant clam metabolism and photosynthesis with zooxanthellae.
• Determine effects of climate change and light on giant clam activity levels and byssal attachment.
• Generation of adaptation and resilience-building plans for the management of wild populations of giant clams on coral reefs into the future, and generation of adaptation guidelines for best practice management of giant clam nurseries and hatcheries for population conservation.