Ocean Acidification and Echinoderms

Many of us discuss “the other carbon dioxide problem,” ocean acidification in our classes. A new study in the journal Ecotoxicology, S. Dupont, et. al., Impact of Near-Future Ocean Acidification on Echinoderms, 19 Ecotoxicology 449-462 (2010) (subscription required) does an excellent job of parsing out both some of the serious potential impacts of OA on ocean ecosystems (with a focus on the phylum echinodermata, which includes sea urchins, brittlestars, sea stars and feather stars), as well as the high levels of uncertainty that exist in making such assessments at this point. The article would be appropriate particularly for graduate students, especially in a more science oriented course with a policy component.

The key take-aways from the study include the following:

  1. For many ocean species, ocean acidification’s most serious impacts may occur in early development stages. For example, one study concluded that a slight decrease of 0.2 units of pH resulted in 100% mortality in only 8 days due to larval malformations;
  2. Ocean acidification impacts could be very species-specific, even among closely related species. For example, one study revealed that two sea urchin species showed opposite responses when exposed to acidic conditions over the course of 60 days, with one species showing a 50% decrease in calcification rates, while another showed a 4.5x increase;
  3. There may be some serious ecosystem implications if certain echinoderm species are threatened by ocean acidification in the future. For example, the study concluded that the brittlestar species Ophiothrix fragilis will be eradicated by declining pH. The species is a keystone species in many coastal ecosystems in the eastern Atlantic; thus, its disappearance could result in major changes in many key benthic and pelagic ecosystems in the region;
  4. Unlike the case of temperature impacts on ocean ecosystems, where some species will be able to avoid adverse consequences by migrating, acidification is likely to occur worldwide, affording species few avenues of escape;
  5. There are many gaps in our understanding of the potential impacts of OA; the future research agenda needs to include longer-term studies, the impacts of synergetic stressors on ocean species, and impacts of OA in different life stages.

Ocean acidification is always an interesting topic in a climate change course. It leads to questions about whether we need a carbon-specific target under the UNFCCC within the “basket approach,” and whether geoengineering proposals are fatally flawed because they fail to address this issue (or in the case of Ocean Iron Fertilization, may actually exacerbate the problem; see my post from a couple of days ago in this context).

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