How does rising atmospheric CO2 affect marine organisms?

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Effects of Elevated CO2 and Warming on Arctic Calanoid Copepods
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.

Calanoid copepods are a type of zooplankton that feeds on phytoplankton and are themselves the food of higher trophic levels. And "a striking life history trait of Arctic Calanus species," in the words of the authors, "is that they spend the winter at greater depth in a resting state (diapause)," which they say "is close to the in situ temperature during winter," which can drop as low as 0°C.

What was done
In an effort to go where no one had gone before - at least in terms of studying the long-term effects of both high CO2 levels and temperatures on Arctic calanoid copepods - Hildebrandt et al. say they "incubated late copepodites and females of two dominant Arctic species, Calanus glacialis and Calanus hyperboreus, at 0°C and at 390 and 3000 ľatm pCO2 for several months in fall/winter 2010," while in an attempt "to detect synergistic effects," they say that in 2011 "C. hyperboreus females were kept at different pCO2 and temperatures (0, 5, 10°C)."

What was learned
The three German researchers indicate that their experiments - which were conducted over several months with repeated measurements, including several aspects of the animals' ecology and physiology - demonstrated that the sub-adult and adult life stages of the Arctic Calanus species they studied "were robust to pCO2 even above future levels of ocean acidification," with the "only synergistic effects of pCO2 and temperature on body mass of C. hyperboreus females found at 5°C."

What it means
In light of what they observed in the laboratory, Hildebrandt et al. conclude that Arctic calanoid copepods "can tolerate pCO2 predicted for a future ocean." But they caution that in combination with increasing temperatures they could possibly experience some form of negative repercussion, but one that would not be fatal.

Reviewed 23 July 2014