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A Zooplankton's Response to Ocean Acidification and Warming

Paper Reviewed
Winder, M., Bouquet, J.-M., Bermúdez, J.R., Berger, S.A., Hansen, T., Brandes, J., Sazhin, A.F., Nejstgaard, J.C., Båmstedt, U., Jakobsen, H.H., Dutz, J., Frischer, M.E., Troedsson, C. and Thompson, E.M. 2017. Increased appendicularian zooplankton alter carbon cycling under warmer more acidified ocean conditions. Limnology and Oceanography 62: 1541-1551.

Appendicularia are a type of zooplankton that play an important role in the cycling of organic carbon from the surface to deep waters of the ocean. They are also important to the ocean food web, helping to maintain the productivity of marine systems by transferring necessary energy and nutrients from primary producers to large predators such as fish. Surprisingly, however, in the words of Winder et al. (2017), very little is known with regard to "how the abundance and frequency of occurrence of these organisms are affected as a consequence of climate change."

Seeking to provide some knowledge in this area, Winder et al. designed a mesocosm experiment to examine the impact of increased temperature and ocean acidification on the biomass, production and carbon cycling of the appendicularian Oikopleura dioica. In doing so, they subjected O. dioica to experimental manipulations of low temperature (12°C) and low pCO2 (pH of 8.02), low temperature (12°C) and high pCO2 (pH of 7.7) or high temperature (14.6°C) and high pCO2 (pH of 8.02), with or without appendicularian addition, for a period of 17 days, further noting that at the beginning of the experiment, nutrients were added to induce a phytoplankton bloom.

In describing their findings, the fourteen researchers report that "total appendicularian abundance increased approximately 10 fold at high temperature compared to ambient conditions of the respective treatments during the postbloom period." In contrast, O. dioica "was not affected by high pCO2." Winder et al. additionally report that "the effect of appendicularians on carbon cycling was also apparent," writing that "these organisms remove dissolved organic carbon, bacteria and small-sized particles with their filter-feeding houses, resulting in increased carbon removal from the water column." And commenting on this latter finding, they acknowledge that "this is an important component of the biological pump and may contribute to CO2 removal from the atmosphere, mitigating anthropogenic increase in greenhouse gases."

Posted 15 November 2017