The Reproduction of a Key Arctic Copepod in Low-pH Seawater

Prefacing their work, Weydmann et al. (2012) write that the Arctic copepod Calanus glacialis "can comprise up to 70-80% of the zooplankton biomass in Arctic shelf seas (Blachowiak-Samolyk et al., 2008; Conover, 1988; Hirche and Mumm, 1992), and is a key herbivore (Mumm et al., 1998; Soreide et al., 2008; Tande, 1991) as well as an important prey item for other zooplankton species (Falk-Petersen et al., 2002, 2004), fish (Fortier et al., 2001), and seabirds (Karnovsky et al., 2003; Weslawski et al., 1999; Wojczulanis et al., 2006)." And, therefore, they say that "testing the potential impacts of ocean acidification on C. glacialis reproduction is vital," which is just what the authors set out to do in this study. More specifically, they investigated "how the reduction of sea surface pH from present day levels (pH 8.2) to a realistic model-based level of pH 7.6, and to an extreme level of pH 6.9, would affect the egg production and hatching success of C. glacialis under controlled laboratory conditions," where "reduced pH seawater was prepared by bubbling compressed CO₂ through filtered seawater, until the appropriate level of pH was reached." So what did their experiment reveal?

The four researchers report that "CO₂-induced seawater acidification had no significant effect on C. glacialis egg production," and that a reduction in pH to 6.9 only delayed hatching at what they called that "extreme level of pH." They also state there was no significant effect "on the survival of adult females," which observation, in their words, "is in agreement with previous studies on other copepod species," citing Mayor et al. (2007) and Kurihara and Ishimatsu (2008).

In reference to their several findings, Weydmann et al. state that their results are "in agreement with previous studies on other copepod species and would indicate that copepods, as a group, may be well equipped to deal with the chemical changes associated with ocean acidification."

Additional References
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Conover, R.J. 1988. Comparative life histories in the genera Calanus and Neocalanus in high latitudes of the northern hemisphere. Hydrobiologia 167/168: 127-142.

Falk-Petersen, S., Dahl, T.M., Scott, C.L., Sargent, J.R., Gulliksen, B., Kwasniewski, S., Hop, H. and Millar, R.M. 2002. Lipid biomarkers and trophic linkages between ctenophores and copepods in Svalbard waters. Marine Ecology Progress Series 227: 187-194.

Falk-Petersen, S., Haug, T., Nilssen, K.T., Wold, A. and Dahl, T.M. 2004. Lipids and trophic linkages in harp seal (Phoca groenlandica) from the Eastern Barents Sea. Polar Research 23: 43-50.

Fortier, M., Fortier, L., Hattori, H., Saito, H. and Legendre, L. 2001. Visual predators and the diel vertical migration of copepods under Arctic sea ice during the midnight sun. Journal of Plankton Research 23: 1263-1278.

Hirche, H.J. and Mumm, N. 1992. Distribution of dominant copepods in the Nansen Basin, Arctic Ocean, in summer. Deep Sea Research 39: 485-505.

Karnovsky, N.J., Weslawski, J.M., Kwasniewski, S., Walkusz, W. and Beszczynska-Moeller, A. 2003. Foraging behavior of little auks in heterogeneous environment. Marine Ecology Progress Series 253: 289-303.

Kurihara, H. and Ishimatsu, A. 2008. Effects of high CO₂ seawater on the copepod Acartic tsuensis. Marine Pollution Bulletin 56: 1086-1090.

Mayor, D.J., Matthews, C., Cook, K., Zuur, A.F. and Hay, S. 2007. CO₂-induced acidification affects hatching success in Calanus finmarchicus. Marine Ecology Progress Series 350: 91-97.

Mumm, N., Auel, H., Hanssen, H., Hagen, W., Richter, C. and Hirche, H.J. 1998. Breaking the ice: large-scale distribution of mesozooplankton after a decade of Arctic and trans-polar cruises. Polar Biology 20: 189-197.

Soreide, J., Falk-Petersen, S., Nost, H.E., Hop, H., Carroll, M.L., Hobson, K. and Blachowiak-Samolyk, K. 2008. Seasonal feeding strategies of Calanus in the high-Arctic Svalbard region. Deep Sea Research Part II 55: 2225-2244.

Tande, K.S. 1991. Calanus in North Norwegian fjords and in the Barents Sea. Polar Research 10: 389-407.

Weslawski, J.M., Koszteyn, J., Kwasniewski, S., Stempniewicz, L. and Malinga, M. 1999. Summer food resources of the little auk, Alle alle (L.) in the European Arctic seas. Polish Polar Research 20: 387-403.

Wojczulanis,K., Jakubas, D., Walkusz, W. and Wennerberg, L. 2006. Differences in food delivered to chicks by males and females of Litle Auks (Alle alle) on south Spitsbergen. Journal of Ornithology 147: 543-548.