High Levels of Carbon Dioxide Could Kill Antarctic Krill

Increased levels of carbon dioxide in seawater kill krill embryos, but only if those levels are significantly higher than at present, researchers have found, reports www.megafishnet.com with reference to SeaWeb.

Writing in the journal Biology Letters, So Kawaguchi of the Australian Antarctic Division and colleagues note that one consequence of increased fossil fuel emissions is higher concentrations of carbon dioxide reaching ocean waters. A principal effect of this is decreasing the pH levels of seawater, a process known as ocean acidification.

In an attempt to test the possible consequences of such ocean acidification on the development of krill, the keystone species of the Antarctic marine ecosystem, Kawaguchi and colleagues set up three seawater tanks bubbled with carbon dioxide at the current level of 380 parts per million (ppm) as well as medium (1,000 ppm) and high (2,000 ppm) levels. In each of those tanks, the researchers attempted to grow krill embryos. There was no change in the development of the embryos in the tanks with current and medium levels of carbon dioxide, but in the tanks containing high levels, none of the embryos survived to hatch.

Under few scenarios are carbon dioxide concentrations in Antarctic waters anticipated to reach 2,000 ppm; however, at current rates of emission increases, researchers predict that by 2100, they will reach 1,400 ppm in the depths of the Southern Ocean. Kawaguchi and colleagues write that their study is the beginning of research into the effects of ocean acidification on krill and that further studies will be necessary to identify the exact carbon dioxide concentration "tipping point" as well as the potential impact of ocean acidification on the later stages of the species' life cycle.