Background
The authors write that "dwarf shrub berries are particularly valued by the human populations at Northern Latitudes as an autumn harvest, but are also consumed by a wide range of animals (Anderson, 1985)." From a human perspective, they say the fruit of these shrubs contain high concentrations of flavonoids and anthocyanins (Heinonen et al., 1998; Faria et al., 2005; Heinonen, 2007), which can scavenge cancer-causing free-radicals (Martin-Aragon et al., 1998; Taruscio et al., 2004) and reduce the oxidative stress caused by these compounds in animals (Johnson and Felton, 2001)." And as one example of the latter benefit, they indicate that "there is already laboratory evidence suggesting that the consumption of Vaccinium myrtillus berry flavonoids by small mammals can increase the antioxidant capacity of their blood plasma which could promote their fitness," citing Talavera et al. (2006).

What was done
In an open-top chamber study conducted at the Abisko Scientific Research Station in Northern Sweden, Gwynn-Jones et al. assessed the impact of atmospheric CO2 enrichment (600 vs. 360-386 ppm) on the berry quality of both Vaccinium myrtillus and Empetrum hermaphroditum in the final year (2009) of a 17-year experiment.

What was learned
Calculating as best we can from the ten researchers' graphically-presented results, it appears that the mean concentration of quercetin glycosides in V. myrtillus was increased by approximately 46% by the approximate mean CO2 concentration increase of 227 ppm. In E. hermaphroditum, on the other hand, syringetin glycoside concentrations were increased by about 36% by the extra CO2, while five anthocyanins had their concentrations increased as follows: delphinidin-3-hexoside by about 51%, cyanidin-3-hexoside by about 49%, petunidin-3-hexoside by about 48%, malvidin-3-pentoside by about 46% and malvidin-3-hexoside by about 59%.

What it means
In light of their several findings and their implications for humans, Gwynn-Jones et al. say that "consumers of E. hermaphroditum may gain higher antioxidant intake at elevated CO2," while adding that "some European bird species show preferential feeding towards berries with higher antioxidant contents (Catoni et al., 2008), which could have important implications for the palatability and, therefore, seed dispersal of these species."

References
Anderson, M. 1985. The Saami reindeer-breeders of Norwegian Lapland. American Scientist 73: 524-532.

Catoni, C., Schaefer, H.M. and Peters, A. 2008. Fruit for health: The effect of flavonoids on humoral immune response and food selection in a frugivorous bird. Functional Ecology 22: 649-654.

Faria, A., Oliveira, J., Neves, P., Gameiro, P., Santos-Buelga, C., De Freitas, V. and Mateus, N. 2005. Anti-oxidant properties of prepared blueberry. Journal of Agricultural and Food Chemistry 53: 6896-6902.

Heinonen, M. 2007. Antioxidant activity and antimicrobial effect of berry phenolics - a Finnish perspective. Molecular Nutrition and Food Research 51: 684-691.

Heinonen, I.M., Meyer, A.S. and Frankel, E.N. 1998. Antioxidant activity of berry phenolics on human low-density lipoprotein and liposome oxidation. Journal of Agricultural and Food Chemistry 46: 4107-4112.

Johnson, K.S. and Felton, G.W. 2001. Plant phenolics as dietary antioxidants for herbivorous insects: A test with genetically modified tobacco. Journal of Chemical Ecology 27: 2579-2597.

Martin-Aragon, S., Basabe, B., Benedi, J.M. and Villar, A.M. 1998. Anti-oxidant action of Vaccinium myrtillus L. Phytotherapy Research 12: 104-106.

Talavera, S., Felgines, C., Texier, O., Besson, C., Mazur, A., Lamaison, J.L. and Remesy, C. 2006. Bioavailability of a bilberry anthocyanin extract and its impact on plasma antioxidant capacity in rats. Journal of the Science of Food and Agriculture 86: 90-97.

Taruscio, T.G., Barney, D.L. and Exon, J. 2004. Content and profile of flavanoid and phenolic acid compounds in conjunction with the antioxidant capacity for a variety of northwest Vaccinium berries. Journal of Agricultural and Food Chemistry 52: 3169-3176.