How does rising atmospheric CO2 affect marine organisms?

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Interactive Effects of CO2 and Temperature on Cotton
Reddy, K.R., Robana, R.R., Hodges, H.F., Liu, X.J. and McKinion, J.M. 1998. Interactions of CO2 enrichment and temperature on cotton growth and leaf characteristics. Environmental and Experimental Botany 39: 117-129.

What was done
The authors grew cotton plants at 350 and 700 ppm atmospheric CO2 in environmental growth chambers known as SPAR units. Twenty-four days after germination, they initiated temperature treatments ranging from 20 to 40C to study the interactive effects of these two variables on leaf and whole plant growth characteristics.

What was learned
Elevated CO2 enhanced individual leaf area by 20%, while it increased whole plant leaf area by an average of 47% across all temperature treatments. CO2-enriched leaves also had greater specific densities (mass per unit area) than leaves grown at ambient CO2, which can be attributed to the greater amounts of nonstructural carbohydrates they contained. As a result, plants grown in elevated CO2 had 31 to 78% more biomass than plants grown at ambient CO2. Atmospheric CO2 enrichment additionally increased the number of fruiting sites per plant at all temperatures; but most fruit aborted, regardless of CO2 concentration, at temperatures greater than 30C.

What it means
Cotton should grow more vigorously as the amount of CO2 in the air continues to climb. Leaves will likely be larger, thereby giving plants greater photosynthetic surface area to produce more carbohydrates to facilitate growth. With more atmospheric CO2, greater numbers of branches and fruiting sites will likely develop as well, which should ultimately provide for the production of more lint for making cloth and textile products.

Reviewed 1 November 1998