International research team discovers marine animals can cope with ocean acidification through epigenetic changes

The increasing amount of carbon dioxide (CO₂) released into the atmosphere from human activities, such as vehicle emissions and power generation, has resulted in a continuous rise in the volume of CO₂ absorbed by the ocean. Carbon dioxide dissolved in the ocean further reacts with seawater to form carbonic acid, which leads to ocean acidification. 

Ocean acidification has many implications for marine species. One of these negative effects is making the building and maintenance of shells difficult for shellfish. It is also considered a threat to coral reef formation. Acidification also affects other ecological processes of some non-calcified invertebrates and reef fish. Many scientists raise grave concerns about these challenges and devote their efforts towards understanding and predicting the impact of ocean acidification on marine ecosystems. However, most of these research works focus only on the immediate impact of acidification on marine species without looking into its transgenerational and long-term effects.

Recently, an international research team including a scholar from FLASS made a breakthrough in this research area. By investigating intergenerational changes in the DNA methylation patterns of copepods in response to elevated CO₂, the research team discovered that while the fertility and sex ratio of copepods were adversely affected by acidification in their first and second generations (F0 and F1), these negative effects were significantly restored in their third generation (F2). This suggests that copepods have a self-repairing ability, enabling them to adapt to environmental changes.

Professor Rudolf Wu Shiu-sun, Advisor (Environmental Science) of the Department of Science and Environmental Studies, is a member of the research team. He is responsible for unearthing the relationships between phenotypic and epigenetic changes among marine organisms, and their relevant environmental implications. He said, “The ‘self-repairing mechanism’ of copepods is the outcome of epigenetic changes (i.e. DNA methylation) in specific regions of genes associated with reproductive resilience.”

The environmental scientist further pointed out that most environmental studies nowadays focus only on the immediate impact of ocean acidification, without looking into its long-term, transgenerational effects. He said, “This study indicates that the epigenetic mechanisms induced may also occur in other species, thus providing a new perspective for future scientific research.”

The international research team, made up of seven scholars from South Korea, mainland China, Hong Kong, and the US, spent two years studying the reproduction of marine species in an acidified environment. Findings by the team that revealed copepods can adapt to ocean acidification by epigenetic changes is considered a major breakthrough in environmental research. The related research paper was recently published in the prestigious academic journal, Nature Climate Change.

Research findings about the adaptative ability of copepods through epigenetic changes suggests that there might be an overstatement about the vulnerabilities of marine species among scientists. That said, Professor Wu still stressed that ocean acidification is irreversible and has detrimental effects on many marine animals such as coral, urchins and shellfish, and that such damage to the marine ecosystem is beyond repair.

“When scientists in different places are conducting a wide range of research to better understand the environmental impacts of ocean acidification, governments around the world should take collective action to reduce carbon emissions in an effort to save the Earth,” Professor Wu said.