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Plant Fatty Acids Beneficial to Human Health Are Enhanced by Atmospheric CO2 Enrichment
Reference
Hoshida, H., Ohira, T., Minematsu, A., Akada, R. and Nishizawa, Y.  2005.  Accumulation of eicosapentaenoic acid in Nannochloropsis sp. in response to elevated CO2 concentrations.  Journal of Applied Phycology 17: 29-34.

Background
The authors say that "eicosapentaenoic acid (EPA), a polyunsaturated [n-3] fatty acid, plays an important role in human health," noting that "the possible uses of EPA in the prevention of cardiovascular diseases (e.g. atherosclerosis, thrombogenesis) and to inhibit tumor growth and inflammation have been reported (Dyerberg et al., 1978; Hirai et al., 1989; Kinsella et al., 1990; Sanders, 1993)."  They also note that "Nitsan et al. (1999) showed that supplementing the diet of hens with Nannochloropsis sp. ["a unicellular marine alga containing a large quantity of EPA"] led to an increased content of n-3 fatty acids in the egg yolk, indicating an additional role in enhancing the nutritional value of eggs."  Likewise, they indicate that "feeding Nannochloropsis sp. to rats caused a significant increase of the content of n-3 polyunsaturated fatty acids (Sukenik et al., 1994)," suggesting it may play an "important role as the source for n-3 polyunsaturated fatty acids in human nutrition."

With respect to the potential impact of the ongoing rise in the air's CO2 concentration on the EPA contents of plants, the authors note that EPA is mainly contained in thylakoid membranes (Sukenik et al., 1989; Hodgson et al., 1991), and that prior experiments have demonstrated that "the amount of stroma thylakoid membrane increased in several plants under elevated CO2 concentrations (Griffin et al., 2001)."  They also report that "in Synechococcus lividus, reduction and synthesis of thylakoid membrane occurred by CO2 deprivation and elevation, respectively (Miller and Holt, 1977)," and that "in Chlorella vulgaris, altering the ambient CO2 concentration varied fatty acid composition (Tsuzuki et al., 1990)."  In addition, they say that "the effect of CO2 on fatty acid composition and/or fatty acid content was reported in algae and higher plants (Tsuzuki et al., 1990; Sergeenko et al., 2000; He et al., 1996; Radunz et al., 2000)," and that "increased EPA production caused by elevated CO2 concentration was reported in P. tricornutum (Yongmanitchai and Ward, 1991)."

What was done
To investigate the subject for themselves, Hoshida et al. grew Nannochloropsis sp. in batch culture under normal (370 ppm) and elevated (3000 and 20,000 ppm) atmospheric CO2 concentrations.

What was learned
The Japanese scientists report that "maximum EPA production was obtained when 20,000 ppm CO2 was supplied 12 hours prior to the end of the exponential growth," and that "the total EPA production during 4-day cultivation was about twice that obtained with ambient air."

What it means
Omega 3 and other fatty acids that have been demonstrated to have important health-promoting features for humans and animal life have been shown by this study and others to experience enhanced production by plants exposed to elevated atmospheric CO2 concentrations.  Consequently, as the air's CO2 content continues to rise, we can expect this phenomenon to be widely enhanced in both aquatic and terrestrial environments, benefiting much of the biosphere.

References
Dyerberg, J., Bang, H.O., Stoffersen, E., Moncada, S. and Vane, J.R.  1978.  Eicosapentaenoic acid and prevention of thrombosis and atherosclerosis.  Lancet 2: 117-119.

Griffin, K.L., Anderson, O.R., Gastrich, M.D., Lewis, J.D., Lin, G., Schuster, W., Seemann, J.R., Tissue, D.T., Turnbull, M.H. and Whitehead, D.  2001.  Plant growth in elevated CO2 alters mitochondrial number and chloroplast fine structure.  Proceedings of the National Academy of Sciences, USA 98: 2473-2478.

He, P., Radunz, A., Bader, K.P. and Schmid, G.H.  1996.  Quantitative changes of the lipid and fatty acid composition of leaves of Aleurites montana as a consequence of growth under 700 ppm CO2 in the atmosphere.  Zeitschrift fur Naturforscher 51 C: 833-840.

Hirai, A., Terano, T., Tamura, Y. and Yoshida, S.  1989.  Eicosapentaenoic acid and adult diseases in Japan: Epidemiological and clinical aspects.  Journal of Internal Medicine, Supplement 225: 69-75.

Hodgson, P.A., Henderson, R.J., Sargent, J.R. and Leftley, J.W.  1991.  Patterns of variation in the lipid class and fatty acid composition of Nannochloropsis oculata (Eustigmatophyceae) during batch culture. I. The growth cycle.  Journal of Applied Phycology 3: 169-181.

Kinsella, J.E., Lokesh, B. and Stone, R.A.  1990.  Dietary n-3 polyunsaturated fatty acids and amelioration of cardiovascular diseases: Possible mechanisms.  American Journal of Clinical Nutrition 52: 10-28.

Miller L.S. and Holt, S.C.  1977.  Effect of carbon dioxide on pigment and membrane content in Synechococcus lividusArchives Microbiologie 115: 185-198.

Nitsan, Z., Mokady, S. and Sukenik, A.  1999.  Enrichment of poultry products with omega 3 fatty acids by dietary supplementation with the alga Nannochloropsis and mantur oil.  Journal of Agricultural and Food Chemistry 47: 5127-5132.

Radunz, A., Alfermann, K. and Schmid, G.H.  2000.  State of the lipid and fatty acid composition in chloroplasts of Nicotiana tabacum under the influence of an increased CO2 partial pressure of 700 p.p.m.  Biochemical Society Transactions 28: 885-887.

Sanders, T.A.B.  1993.  Marine oils: Metabolic effects and role in human nutrition.  Proceedings of the Nutrition Society 52: 457-472.

Sergeenko, T.V., Muradyan, E.A., Pronina, N.A., Klyachko-Gurvich, G.L., Mishina, I.M. and Tsoglin, L.N.  2000.  The effect of extremely high CO2 concentration on the growth and biochemical composition of microalgae.  Russian Journal of Plant Physiology 47: 632-638.

Sukenik, A., Cameli, Y. and Berner, T.  1989.  Regulation of fatty acid composition by irradiance level in the eustigmatophyte Nannochloropsis sp.  Journal of Phycology 25: 686-692.

Sukenik, A., Takahashi, H. and Mokady, S.  1994.  dietary lipids from marine unicellular algae enhance the amount of liver and blood omega-3 fatty acids in rats.  Annals of Nutrition and Metabolism 38: 85-96.

Tsuzuki, M., Ohnuma, E., Sato, N., Takaku, T. And Kawaguchi, A.  1990.  Effects of CO2 concentration during growth on fatty acid composition in microalgae.  Plant Physiology 93: 851-856.

Watanabe, T.  1993.  Importance of docosahexaenoic acid in marine larval fish.  Journal of the World Aquaculture Society 24: 152-161.

Yongmanitchai, W. and Ward, O.P.  1991.  Growth of and omega-3 fatty acid production by Phaeodactylum tricornutum under different culture conditions.  Applied Environmental Microbiology 57: 419-425.

Reviewed 19 October 2005