How does rising atmospheric CO2 affect marine organisms?

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Effects of Short-Term Atmospheric CO2 Enrichment on Melon
Mavrogianopoulos, G.N., Spanakis, J. and Tsikalas, P.  1999.  Effect of carbon dioxide enrichment and salinity on photosynthesis and yield in melon.  Scientia Horticulturae 79: 51-63.

What was done
Parnon melons (Cucumis melo) were grown in greenhouses subjected to atmospheric CO2 concentrations of 400, 800, and 1200 ppm for the first five hours of each day and were irrigated with nutrient solutions containing 0, 25, and 50 mM NaCl to determine the interactive effects of elevated CO2 and salinity on plant growth and yield.

What was learned
Exposure to atmospheric CO2 concentrations of 800 and 1200 ppm CO2 increased net photosynthetic rates by a respective average of 75 and 120%, regardless of salinity, relative to rates measured at 400 ppm CO2.  In addition, atmospheric CO2 enrichment partially reversed the negative effects of salinity on shoot growth, leaf growth, and leaf chlorophyll content.  Although melon yield significantly increased with atmospheric CO2 enrichment at all salinity levels, the greatest CO2-induced enhancement was observed at the lowest salinity concentration.

What it means
As the CO2 content of the air continues to rise, it is likely that melon plants will display significant increases in photosynthesis, even if soil salinity levels are higher than optimal for melon production.  With more carbohydrates being produced during photosynthesis, it is also likely that melon yields will increase, regardless of soil salinity.  Thus, in areas where agricultural soils or water supplies are moderately saline, the aerial fertilization effect induced by the rising atmospheric CO2 concentration will provide a beneficial impact on melon growth and yield.

Reviewed 15 November 1999