How does rising atmospheric CO2 affect marine organisms?

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Spinach for Space Travel
Proietti, S., Moscatello, S., Giacomelli, G.A. and Battistelli, A. 2013. Influence of the interaction between light intensity and CO2 concentration on productivity and quality of spinach (Spinacia oleracea L.) grown in fully controlled environment. Advances in Space Research 52: 1193-1200.

The authors write that "life support in space would require plant growing units with a fully controlled environment where plants would recycle oxygen (O2), carbon dioxide (CO2), water and nutrients and produce food for the crew," citing Rygalov (1996), Sadler and Giacomelli (2002), Davies et al. (2003) and Sychev et al. (2008), while further noting that "high quality food would be particularly valuable under the stressful conditions of space travel for physiological and psychological reasons," citing Perchonok and Bourland (2002).

What was done
Focusing on both the quantity and quality aspects of such food production, Proietti et al. grew spinach (Spinacia oleracea L.) plants from seed at a density of eight seeds per each of several 1-L pots filled with perlite and placed in controlled-environment chambers where the young plants were grown at two different levels of light intensity (photosynthetic photon flux density of 200 and 800 Ámol/m2/sec) and two different levels of atmospheric CO2 concentration (360 and 800 ppm), and where they were also irrigated with a full-strength nutrient solution twice a week for five full weeks after the expansion of the young plants' cotyledons.

What was learned
In response to the experimental increase in light intensity, plant fresh weights rose by 104%, while plant dry weights rose by 141%; and in response to the increase in atmospheric CO2 concentration, plant fresh weights rose by 64%, while plant dry weights rose by 66%. In terms of the food quality of the spinach plants, the four researchers found that "growth under high CO2 and high light conditions strongly enhanced the organoleptic quality of spinach [i.e., its taste, color, odor or feel], particularly if eaten as raw salad." And, based on other of their findings, they concluded that "environmental factors (light and CO2) can be efficiently controlled to increase beneficial (ascorbic acid) but not detrimental (oxalic acid) metabolites."

What it means
Maybe a manned mission to Mars may not be that far-fetched after all. But even if it is, we will still be benefited, here on earth, as the air's CO2 content continues to rise ... especially if we're spinach eaters.

Davies, F.T., He, C., Lacey, R.E. and Ngo, Q. 2003. Growing plants for NASA - Challenges in lunar and Martian agriculture. Combined Proceedings - International Plant Propagators' Society 53: 59-64.

Perchonok, M. and Bourland, C. 2002. NASA food systems: past, present and future. Nutrition 18: 913-920.

Rygalov, V.Ye. 1996. Cultivation of plants in space: their contribution to stabilizing atmospheric composition in closed ecological systems. Advances in Space Research 18: (4/5)165-(4/5)176.

Sadler, P.D. and Giacomelli, G.A. 2002. Mars inflatable greenhouse analog. Life Support and Biosphere Science 8: 115-123.

Sychev, V.N., Levinskikh, M.A. and Podolsky, I.G. 2008. Biological component of life support systems for a crew in long-duration space expeditions. Acta Astronaut 63: 1119-1125.

Reviewed 27 November 2013