Researchers at the Centre for Sustainable Aquatic Research, Swansea University show how zooplankton is vulnerable to ocean acidification

Zooplankton storyZooplankton may not be coping as well as previously thought to higher levels of acidity in seawater. Ocean acidification has been described as “the other CO2 problem”. Like its better-known counterpart, climate change, it is caused by rising levels of carbon dioxide in the atmosphere.

The team, based at the Centre for Sustainable Aquatic Research (CSAR) at Swansea University, and working with colleagues at Plymouth Marine Laboratory, studied a common species of zooplankton, the copepod Acartia tonsa.

Previously, research by others, based largely on adult females, has suggested that copepods are not affected by ocean acidification. However, the Swansea team, looking at all stages of the life cycle – from eggs through to adulthood – reveal that this is not so. They examined how the creatures reacted to different levels of CO2 in seawater: from present-day levels to higher concentrations based on different projections for the future.

The researchers found that mortality rates increased across all ages in response to higher levels of CO2. Young zooplankton were the most vulnerable, with a threefold increase in mortality when exposed to “near-future” levels of CO2. Fertility was also affected by rising CO2.

Gemma Cripps, PhD researcher at CSAR and lead author of the paper, said:

"Our results show how important it is to look at all stages of the life cycle. Previous research, which has largely focused only on adult females, risked underestimating the effects of ocean acidification on zooplankton. Zooplankton are the foundation of the whole food chain in the ocean, for example as a crucial food source for fish such as cod and herring. Without zooplankton, life in the sea would not be as we know it.

Our research will help provide a better picture of how these tiny but vital creatures are responding to changes in our oceans."