Study: How Global Warming Affects Natural Plankton Community

A new study from the GEOMAR Helmholtz Centre for Ocean Research Kiel revealed that rising ocean temperature, ocean acidification, eutrophication and lack of oxygen can negatively affect important plankton organism.

The study, published in the journal PLOS ONE, showed that the rising temperature of waters, combined with ocean acidification, could reduce the abundance of copepods.

Copepods are a group of millimeter-long crustaceans forming about 80 percent of the zooplankton and are important food for fish and their larvae.

For the study, the researchers mimic the future oceans in their lab using the so-called "indoor mesocosms." Natural plankton community from Kiel Fjord was transferred into 12 1400-liter tanks. The tanks were brought to two different temperatures and two different carbon dioxide concentrations to mimic the extent of warming and acidification predicted during the time of the study.

The abundance and body size of various developmental stages of copepods, as well as their fatty acid contents were examined after a month. The researchers noted that rising water temperatures has more significant negative impact to copepods than ocean acidification. They observed that ocean acidification could mitigate some of the adverse reaction by supporting the growth of phytoplankton, which serve as food for copepods, through the additional carbon dioxide dissolved in the water. However, the benefits are not strong enough to produce positive effect.

Furthermore, the researchers observed that the combination of warming temperature and ocean acidification are having a negative effect in the composition of fatty acids in a natural community of copepods.

"This means that the food quality to higher levels of the food web decreases", explained Dr. Jessica Garzke, marine biologist at GEOMAR and first-author of the study, in a press release. "Food webs, which are influenced by the food quality - not by the sheer mass of supplies - would be deteriorated."

The researchers believe that their findings could be the same on other coastal regions similar to Kiel Fjord. They believe that further research, considering environmental factors, is necessary to determine effects of climate change.