Link between ocean acidification and declining mussels?

Is the ocean already acidic enough to drive out mussels? NPR reported this morning on a new study that attributed falling mussel populations on Tatoosh Island, WA (a famous intertidal ecology site that’s been monitored since the 1960s) to decreasing pH.

Ocean chemistry measured from Tatoosh Island found that the ocean there is becoming acidic 10 times faster than expected, according to a study published in the Proceedings of the National Academy of Sciences. And the study’s author J. Timothy Wootton says the island’s ecosystem is changing rapidly as a result.

During an eight-year period, he says, 10 to 20 percent of the mussels on the island have been replaced by acid-tolerant algae.

It’s based on this PNAS article, which was published online yesterday. The authors use a bunch of fancy multispecies Markov chain models to prove the correlation between declining mussel cover and acidification, but unfortunately I have neither the knowledge (working on it!) or the time today to really delve into it. Anyone out there have an opinion? Paging JEByrnes

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4 Responses to Link between ocean acidification and declining mussels?

  1. jebyrnes says:

    Indeed, the Markov chain approach is pretty solid as a means of temporal forecasting, as Wootton has shown in the past. I’ve always really admired it, and am excited to see its application here. It’s something I admittedly don’t understand well as I haven’t studied it. But, it’s a great way to get at temporal trends.

  2. jebyrnes says:

    N.B. The one critical thing I’ll say here about the model is that it does not use pH as a parameter. Rather, it uses observed transition probabilities to predict dynamics. This was then correlated with changes in pH. The patterns matched, but it does not rule out other causal agents that are correlated with the observed changes in pH.

    Using Pearson correlation coefficients, we probed whether any detected variation in transition patterns was related to pH change by correlating the annual variation in each transition probability with the average annual pH measured in the intervening year.

    Others who know more how this was done, correct me if I’m wrong.

  3. Yes, that was the part I was confused about – there could be any number of reasons that the composition of the rocky intertidal changed. Temperature (maybe correlated with ENSO), bad mussel recruitment, increased predation, human trampling…though it is interesting that they have documented a decrease in pH. (Of course, pH alone does not control the availability of carbonate ions.)

  4. Karen James says:

    I feel indirectly connected to Tatoosh Island. When I was doing my PhD in Seattle, one of my roommates was Mar Wonham, who did her field work out there on invasive mussels. I remember her packing to go on field sessions: waders, tent, serious cold-weather gear, emergency generators, things like that. I was terribly impressed (and still am).
    http://www.math.ualberta.ca/~mwonham/

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