How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic


Doubling Atmospheric Ozone and CO2 Concentrations: Effects on Silver Birch Tree Growth
Reference
Riikonen, J., Lindsberg, M.-M., Holopainen, T., Oksanen, E., Lappi, J., Peltonen, P. and Vapaavuori, E.  2004.  Silver birch and climate change: variable growth and carbon allocation responses to elevated concentrations of carbon dioxide and ozone.  Tree Physiology 24: 1227-1237.

What was done
The authors grew two clones of seven-year-old silver birch (Betula pendula Roth) saplings out-of-doors in open-top chambers (OTCs) maintained at ambient and twice-ambient ozone (O3) concentrations and ambient and twice-ambient CO2 concentrations for a total of three years, after which the trees were destructively harvested.

What was learned
Riikonen et al. report that "the negative effects of elevated O3 were found mainly in ambient CO2, not in elevated CO2."  In fact, whereas doubling the air's O3 concentration decreased total biomass production by 13% across both clones, simultaneously doubling the air's CO2 concentration increased total biomass production by 30%, thereby more than compensating for the deleterious consequences of doubling the atmospheric ozone concentration.

In commenting on this ameliorating effect of elevated CO2, the team of Finnish scientists says it "may be associated with either increased detoxification capacity as a consequence of higher carbohydrate concentrations in leaves grown in elevated CO2, or decreased stomatal conductance and thus decreasing O3 uptake in elevated CO2 conditions (e.g., Rao et al., 1995)."  They also note that "the ameliorating effect of elevated CO2 is in accordance with the results of single-season OTC and growth chamber studies on small saplings of various deciduous tree species (Mortensen 1995; Volin and Reich, 1996; Dickson et al., 1998; Loats and Rebbeck, 1999) and long-term open-field and OTC studies with aspen and yellow-poplar (Percy et al., 2002; Rebbeck and Scherzer, 2002)."

What it means
As ozone concentrations continue to rise at a rapid rate, we can be thankful the air's CO2 concentration is rising right along with them.  Were this not so, both managed (agro) and natural ecosystems would be in a world of hurt.

References
Dickson, R.E., Coleman, M.D., Riemenschneider, D.E., Isebrands, J.G., Hogan, G.D. and Karnosky, D.F.  1998.  Growth of five hybrid poplar genotypes exposed to interacting elevated [CO2] and [O3].  Canadian Journal of Forest Research 28: 1706-1716.

Loats, K.V. and Rebbeck, J.  1999.  Interactive effects of ozone and elevated carbon dioxide on the growth and physiology of black cherry, green ash, and yellow-poplar seedlings.  Environmental Pollution 106: 237-248.

Mortensen, L.M.  1995.  Effects of carbon dioxide concentration on biomass production and partitioning in Betula pubescens Ehrh. seedlings at different ozone and temperature regimes.  Environmental Pollution 87: 337-343.

Percy, K.E., Awmack, C.S., Lindroth, R.L., Kubiske, M.E., Kopper, B.J., Isebrands, J.G., Pregitzer, K.S., Hendrey, G.R., Dickson, R.E., Zak, D.R., Oksanen, E., Sober, J., Harrington, R. and Karnosky, D.F.  2002.  Altered performance of forest pests enriched by CO2 and O3Nature 420: 403-407.

Rao, M.V., Hale, B.A. and Ormrod, D.P.  1995.  Amelioration of ozone-induced oxidative damage in wheat plants grown under high carbon dioxide.  Plant Physiology 109: 421-432.

Rebbeck, J. and Scherzer, A.J.  2002.  Growth responses of yellow-poplar (Liriodendron tulipifera L.) exposed to 5 years of [O3] alone or combined with elevated [CO2].  Plant, Cell and Environment 25: 1527-1537.

Reviewed 26 January 2005