Wednesday, July 7, 2010

Rising CO2 may lead Nemo to change, not to danger

Summary for Policy Makers: Change is not necessarily a bad thing. 
Nemo in more danger from probing researchers than from rising CO2. 

ABC HEADLINE: Katherine Nightingale posts a report for ABC Science with the rather cute but worrying headline "Rising CO2 may lead Nemo to danger".
ABC REPORTED:  The report describes the results of research published in the Proceedings of the National Academy of Sciences journal under the title "Replenishment of fish populations is threatened by ocean acidification ". This study looks at fish behaviour under CO2 levels higher than present and provides some alarming conclusions.
The ABC report includes the following statements:
"Previous research indicates that as carbon dioxide (CO2) levels in the atmosphere climb the surface water of the oceans could become more acidic."
"As part of the study, the researchers put clownfish and damselfish larvae into seawater equivalent to that which would be found if the atmosphere contained 700 ppm and 850 ppm of CO2 - levels that could be reached by the end of the century."
The report concludes: "Professor Geoffrey Jones, also of JCU and the ARC Centre of Excellence for Coral Reef Studies, said the research took the level of concern about the effects of climate change on coral reef fish "to a whole new level". "Without drastic action to cut emissions, all we can do is hope that fish will be able to adapt," Mr Jones said. "However, given that the rate of CO2 increase is unprecedented, there are no grounds for optimism."

1. Factual error: Claims that oceans are becoming "more acidic" are incorrect. The correct terminology for a reduction of pH for an alkaline solution is "less alkaline". Once pH has passed below 7 a solution is said to be acidic at which point the term "more acidic" may be considered appropriate. Use of the term "more acidic" is factually incorrect, misleading and deliberately sensationalist.
2. Lack of inquiry: Fish have flourished over a wide range of environmental conditions with varying salinity, ocean pH, temperature and CO2 levels. They came to prominence in the oceans during the Devonian period  (416-359Ma) during which time estimated CO2 levels ranged between 4000 and 1000 ppm. It appears ABC's reporter did not seek to ask researchers any questions around this point - ie. Fish have thrived under vastly different environmental conditions in the past, why won't they continue to do so in the future?
The published paper includes the following statements of interest:

"This life-history transition (from planktonic larval phase to adult) is usually associated with high rates of mortality and can be a period of strong" selection." 
"Even a slight survival advantage could lead to rapid selection given that a large proportion of all fish larvae that settle to coral reefs are consumed by predators within the first few days. (our emphaisis)
ABC's reporter failed to probe these aspects of the study in any detail. We provide the following line of questioning to assist:
"The basis of your experiment was to take fish genetically adapted to water with current levels of CO2, and drop them into water with more CO2 and observe their behaviour.
Given that any changes in CO2 content will be gradual and will likely occur over a 100 or so generations of the fish observed, why won't the fish population in question simply respond to the selective pressures that would rapidly weed out individuals less adapted to higher CO2 concentrations,  leaving a population of adapted Nemos thriving under higher CO2 levels? Your results show a small proportion of the population shows no behavioural change under elevated CO2 conditions?  Isn't it true that rapid natural selection means this small population will expand to fill in the gaps left by those fish more affected by increasing CO2?  This notion is supported by statements in your paper (Even a slight survival advantage could lead to rapid selection). Isn't your lack of optimism about Nemo's future contradicted by your own statements regarding rapid selection pressure? It appears likely that the fish will in fact successfully adapt to the changing environment.

The affect of CO2 on predator populations was not studied. Is it possible that the same degradation  in olfactory ability may similarly affect predators, and if so would this reduction in predator ability balance the similar changes in the prey species, leaving no net change in predator/prey balance?

You indicate in your paper that "Settlement-stage larvae that had been exposed to elevated CO2 (700 and 850 ppm) were more active, ventured farther away from shelter, and were less responsive to threats (i.e., were behaviorally bolder) than controls."
Might "bolder" individuals be more adept at feeding that less bold individuals? And if so might this actually have positive consequences? In the absence of factual evidence is it fair to say you are second guessing evolution.
Your paper concludes with the statement: "Our results show that even moderate increases in CO2 concentrations dissolved in the ocean are likely to have significant impacts on the sustainability of fish populations by altering individual behavior and increasing mortality at critical life-history transitions."

Your paper demonstrates changes in fish behaviour possibly linked to changes in CO2 content. It provides no evidence for impacts on the sustainability of fish populations. In fact don't your conclusions about the impact on sustainability ignore the positive effects of rapid natural selection pressures, that on face value suggest there should actually be great optimism in Nemo's ability to successfully adapt to future changes in CO2.

OUTCOME: 20/8/2010
Thank you for your email regarding the article 'Rising CO2 may lead Nemo to danger', published on the ABC News and ABC Science websites on 7 July. I am sorry for the delay in responding to you.

I understand you believe this article contained a factual error and the staff responsible for it were not questioning enough. In light of your concerns, Audience & Consumer Affairs has assessed the article against sections 5.2.2(c) and (f) of the ABC's Editorial Policies (

I note your view that the statement "Previous research indicates that as carbon dioxide (CO2) levels in the atmosphere climb the surface water of the oceans could become more acidic" was incorrect, misleading and sensationalist. On review, Audience & Consumer Affairs does not agree with this assessment. A decrease in the ocean's pH level signifies increased acidity, regardless of the fact that the pH remains above 7. We are satisfied that the statement was accurate and in context, in accordance with section 5.2.2(c) of the Editorial Policies.

I also note the range of issues you believe the staff responsible for the article should have questioned the researchers about. Editorial judgements about which aspects of a study to ask researchers about are based on news values. ABC Innovation has advised that in its view, the issues concerning the evolution of fish which you believe should have been raised with the researchers were not relevant and were not the focus of the study the article reported on.

In particular, it is important to recognise that the research was not a study of whether fish can survive under different environmental conditions; obviously, as you point out, they have done so in past. Rather, the study focused on whether contemporary fish (clownfish and damselfish in particular) have the capacity for adaptation of behavioural responses if the carbon dioxide concentration in their environment increases rapidly, and therefore whether ocean acidification poses a threat to the sustainability of fish populations.

Audience & Consumer Affairs considers that research on the possible impacts of rising carbon dioxide levels is an issue affecting society and individuals, and ABC Innovation's decision to report on the study and interview its lead author, Professor Philip Munday, as well as Professor David Booth and Professor Geoffrey Jones, was consistent with section 5.2.2(f) of the Editorial Policies. On the basis of the content of the study and the article, it is clear that the staff responsible for the article asked pertinent questions of the interviewees. On review, Audience & Consumer Affairs is satisfied that the requirements of section 5.2.2(f) of the Editorial Policies were met.

Nonetheless, please be assured that your comments have been noted and conveyed to relevant staff in ABC Innovation so that they are aware of your concerns about the article and your suggested lines of questioning.

Thank you for taking the time to write.

Yours sincerely
ABC Audience & Consumer Affairs
COMMENT: Nemo appears to be in more danger from probing researchers than from rising CO2 levels. Rapid natural selection will help Nemo adapt to a more carbonated future.

Update: perhaps Nemo is on fluoxetine? Swim away from the light little fishy!

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