Giant clams: turning up the heat

  • Other species
Years funded
  • 2014
  • Archived
Project type
  • Research

Giant clams can weigh up to 300 kilograms. Sue-Ann is trying to predict how they will fare as our oceans become more acidic in a warming world, creating a hostile environment for animals that have calcium carbonate shells.

Giant clams: turning up the heat

Sue-Ann Watson

Project leader
About the project leader
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...
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Project details

Giant clams and climate change: ocean acidification and global warming research for conservation and management

Key objective

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.

Why is this important

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.

Aims & objectives

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.