Paper Reviewed
Almen, A.-K., Vehmaa, A., Brutemark, A. and Engstrom-Ost, J. 2014. Coping with climate change? Copepods experience drastic variations in their physiochemical environment on a diurnal basis. Journal of Experimental Marine Biology and Ecology 460: 120-128.

Almen et al., 2014 write as background for their work that "copepods are the most abundant zooplankton, constituting an important food source for fish in the Baltic Sea," while noting that any negative effects climate change might possibly have on them can thus have "far reaching consequences" for the ecosystems in which they are found. Therefore, explaining that "copepods perform diel vertical migration to avoid predators," as documented by Vuorinen et al. (1983), during which they experience "highly fluctuating conditions in their physicochemical environment, i.e., pH, temperature, salinity, oxygen, light and chlorophyll a concentrations," they studied the vertical profiles of an array of some of these environmental variables along with the vertical distribution of common copepods in a shallow coastal area of the Baltic Sea, sampling once a month - in June, July and August - every sixth hour during a 24-hour period.

This work revealed, in the words of the four Finlanders, that copepods regularly experience "a change in pH of more than 0.5 units and 5°C change in temperature" in each of their daily migrations; and they thus remark that "coastal copepods are experiencing a range of variation in their physicochemical environment that is equal to or larger than the predicted climate change for the year 2100." Similar conclusions have been reached by Pedersen et al. (2013) in regard to another North Atlantic copepod and by Lewis et al. (2013) and Hildebrandt et al. (2014) in regard to two Arctic copepods. Hence, it would appear that Earth's copepods, wherever they are found, should be able to withstand whatever degree of ocean acidification and warming might possibly be experienced in the planet's future.

References
Hildebrandt, N., Niehoff, B. and Sartoris, F.J. 2014. Long-term effects of elevated CO2 and temperature on the Arctic calanoid copepods Calanus glacialis and C. hyperboreus. Marine Pollution Bulletin 80: 59-70.

Lewis, C.N., Brown, K.A., Edwards, L.A., Cooper, G. and Findlay, H.S. 2013. Sensitivity to ocean acidification parallels natural pCO2 gradients experienced by Arctic copepods under winter sea ice. Proceedings of the National Academy of Sciences USA 110: 10.1073/pnas.131516210.

Pedersen, S.A., Hansen, B.H., Altin, D. and Olsen, A.J. 2013. Medium-term exposure of the North Atlantic copepod Calanus finmarchicus (Gunnerus, 1770) to CO2-acidified seawater: effects on survival and development. Biogeosciences 10: 7481-7491.

Vuorinen, I., Rajasilta, M. and Salo, J. 1983. Selective predation and habitat shift in a copepod species - support for the predation hypothesis. Oecologia 59: 62-64.