Paper Reviewed
Horn, H.G., Boersma, M., Garzke, J., Loder, M.G.J., Sommer, U. and Aberle, N. 2016. Effects of high CO2 and warming on a Baltic Sea microzooplankton community. ICES Journal of Marine Science 73: 772-782.

In the words of Horn et al. (2016), "global warming and ocean acidification are among the most important stressors for aquatic ecosystems." And they state that "to investigate their direct and indirect effects on a near-natural plankton community," they set up several mesocosms in a full-factorial design to study the effects of warming and high CO2 concentrations on a Baltic Sea autumn plankton community, focusing on the impacts they subsequently observed on the community's microzooplankton or MZP.

So what did the six German scientists learn from their study? Overall, they say their experiment demonstrated that "Kiel Fjord and especially MZP communities are not expected to be directly affected by a high pCO2 in the future," most likely due to "a high tolerance of MZP species to average pCO2 levels of 700 ppm," citing Thomsen et al. (2010), and while further noting that "most ecologically important groups in the Baltic Sea foodweb seem to be rather tolerant to acidification," citing Havenhand (2012), and additionally noting that "there was no indication of changes in phytoplankton food quality in terms of stoichiometry due to high CO2" as described by Paul et al. (2015).

In concluding, therefore, Horn et al. say that their results, augmented by those of others who they cite, "indicate that global warming affects MZP plankton communities in terms of higher total biomass, increased growth rates, and earlier autumn bloom timing," which could, in turn, "lead to changes in trophic dynamics due to a tighter coupling of phytoplankton and MZP," which they say is "likely to enhance energy transfer efficiency to higher trophic levels," as has also been described by Aberle et al. (2015).

References
Aberle, N., Malzahn, A.M., Lewandowska, A.M. and Sommer, U. 2015. Some like it hot: the protozooplankton-copepod link in a warming ocean. Marine Ecology Progress Series 519: 103-113.

Havenhand, J.N. 2012. How will ocean acidification affect Baltic Sea ecosystems? An assessment of plausible impacts on key functional groups. Ambio 41: 637-644.

Paul, C., Matthiessen, B. and Sommer, U. 2015. Warming, but not enhanced CO2 concentration, quantitatively and qualitatively affects phytoplankton biomass. Marine Ecology Progress Series 528: 39-51.

Thomsen, J., Gutowska, M.A., Saphorster, J., Heinemann, A., Trubenbach, K., Fietzke, J., Hiebenthal, C., Eisenhauer, A., Kortzinger, A., Wahl, M. and Melzner, F. 2010. Calcifying invertebrates succeed in a naturally CO2-rich coastal habitat but are threatened by high levels of future acidification, Biogeosciences 7: 3879-3891.