How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic


Growth of Komatsuna and Radish in Japan: CO2 vs. O3
Reference
Yonekura, T., Kihira, A., Shimada, T., Miwa, M., Aruzate, A., Izuta, T. and Ogawa, K. 2005. Impacts of O3 and CO2 enrichment on growth of Komatsuna (Brassica campestris) and radish (Raphanus sativus). Phyton 45: 229-235.

What was done
The authors grew individual komatsuna (Brassica campestris cv. Rakuten) and radish (Raphanus sativus cv. Akamaru) plants from seed (one to a pot) in 1.4-L pots filled with "black soil" within controlled-climate chambers for 30 days in air of one of four different daylight O3 concentrations - 0-5 (charcoal-filtered), 60, 90 or 120 ppb - after which they destructively harvested the plants and determined their final dry weights.

What was learned
In the case of komatsuna (Japanese mustard spinach), where the edible portion of the vegetable is produced aboveground, the mean aboveground dry weights of the plants at the end of their 30-day growth cycle were 0.76, 0.63, 0.53 and 0.39 g in the 0-5, 60, 90 and 120 ppb O3 treatments, respectively, when grown in ambient air of 380 ppm CO2. When grown in air of 760 ppm CO2, however, aboveground weights for the same set of O3 concentrations were 1.19, 1.10, 0.98 and 0.85 g, which represent CO2-induced growth enhancements of 57%, 75%, 85% and 118%. Also of note is the fact that the doubling of the air's CO2 concentration more than compensated for the negative impact caused by the highest of the four O3 concentrations in ambient-CO2 air, turning what would have been a 49% O3-induced yield loss (from 0.76 to 0.39 g) into a 12% CO2-induced yield gain (from 0.76 to 0.85 g).

In the case of radish, where the edible portion of the vegetable is produced belowground, the mean belowground dry weights of the plants at the end of their 30-day growth cycle were 0.63, 0.59, 0.39 and 0.36 g in the 0-5, 60, 90 and 120 ppb O3 treatments, respectively, when grown in ambient air of 380 ppm CO2. When grown in air of 760 ppm CO2, however, belowground weights for the same set of O3 concentrations were 1.45, 1.34, 1.15 and 0.88 g, which represent CO2-induced growth enhancements of 132%, 127%, 195% and 144%. Also of note is the fact that the doubling of the air's CO2 concentration more than compensated for the negative impact caused by the highest of the four O3 concentrations in ambient-CO2 air, turning what would have been a 43% O3-induced yield loss (from 0.63 to 0.36 g) into a 40% CO2-induced yield gain (from 0.63 to 0.88 g).

What it means
In light of the continuing increases in atmospheric O3 concentrations being monitored in Japan, plus the significant vegetable yield reductions caused by this phenomenon, it is important that the air's CO2 content be allowed to maintain its upward course until this true atmospheric pollutant (anthropogenic-produced ozone) can be more effectively controlled.

Reviewed 25 July 2007