How does rising atmospheric CO2 affect marine organisms?

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Response of Tropical Vines to Elevated CO2 in Deep Shade
Granados, J. and Korner, C.  2002.  In deep shade, elevated CO2 increases the vigor of tropical climbing plants.  Global Change Biology 8: 1109-1117.

What was done
Three tropical understory vines (Gonolobus cteniophorus, Ceratophytum tetragonolobum and Thinouia tomocarpa) were grown for seven months in controlled environment chambers maintained at atmospheric CO2 concentrations of 280, 420, 560 and 700 ppm in combination with low and high light intensities to study the interactive effects of these two parameters on growth in these three understory species.

What was learned
Plant biomass increased with atmospheric CO2 concentration from 280 to 560 ppm in all three vines, and continued to increase up to 700 ppm in all species but Gonolobus, which is the fastest growing of the three species.  On average, plant biomass was 61% greater at high light than it was at low light.  However, the greatest CO2-induced growth responses in each species occurred in the low light environment.  Increasing the atmospheric CO2 concentration from 280 to 420 ppm increased Gonolobus plant biomass by 86 and 32% in low and high light environments, respectively, Ceratophytum plant biomass by 249 and 24% in low and high light environments, respectively, and Thinouia plant biomass by 65% in low light, while it actually decreased plant biomass by 1% in the high light environment.

What it means
As the atmospheric CO2 concentration continues to rise, these three tropical vines will likely exhibit enhanced biomass production, in spite of the low light conditions that generally prevail in their understory environment.  In fact, the present paper demonstrates that the greatest relative CO2-induced growth response in these species occurs under low, rather than under high, light intensities.  This paper also shows that more rapidly growing species such as Gonolobus are not necessarily more responsive to atmospheric CO2 enrichment than slower growing species such as Ceratophytum.

Reviewed 15 January 2003