How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Effects of Elevated CO2 and Water Stress on Red Oak
Tomlinson, P.T. and Anderson, P.D.  1998.  Ontogeny affects response of northern red oak seedlings to elevated CO2 and water stress.  II.  Recent photosynthate distribution and growth.  New Phytologist 140: 493-504.

What was done
The authors grew northern red oak seedlings in controlled environment chambers for 8 to 11 weeks at atmospheric CO2 concentrations of 400, 530, and 700 ppm.  In addition, seedlings were repeatedly subjected to well-watered or water-stressed conditions to study the interactive effects of elevated CO2 and water stress on photosynthesis and growth.

What was learned
Elevated CO2 generally offset the negative effects of water stress on seedling growth; and root development was favored under these interactive conditions.  This phenomenon helped negate the deleterious effects of water stress in CO2-enriched seedlings (grown at 700 ppm) and allowed them to produce just as much biomass as well-watered seedlings grown at 400 ppm CO2.

What it means
As the CO2 content of the air continues to rise, red oak seedlings will accrue a degree of physiological protection that will likely offset any negative growth effects associated with mild water stress.  CO2-induced increases in photosynthetic rates, coupled with increases in sink strength of roots, should allow seedlings to increase their drought tolerance by establishing more extensive root systems.  Although red oak seedlings in the Lake States area of the USA already exist in their most xeric ranges and experience regeneration problems, the authors concluded that "a predicted future climate scenario of double atmospheric concentrations of CO2 and mild water stress would not affect the growth-related aspects of current regeneration problems."

Reviewed 15 May 1999