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Echinometra Sea Urchins Thriving on CO2 from Volcanic Vents

Paper Reviewed
Uthicke, S., Ebert, T., Liddy, M., Johansson, C., Fabricius, K.E. and Lamare, M. 2016. Echinometra sea urchins acclimatized to elevated pCO2 at volcanic vents outperform those under present-day pCO2 conditions. Global Change Biology 22: 2451-2461

So how did Uthicke et al. (2016) learn what is implied by the title of their paper? As they go on to describe it, they studied "an Echinometra species on natural volcanic CO2 vents in Papua New Guinea, where they are CO2-acclimated and also subjected to secondary ecological changes from elevated CO2," and where they additionally experienced "large daily variations in pH (>1 unit) and pCO2 (>2000 ppm) and average pH values (pHT 7.73)," which values, they make a point of noting, are "much below those expected under the most pessimistic future emission scenarios."

So how did the six scientists learn what they say they learned? They state that they measured the growth history of the sea urchins "over a 17-month period using tetracycline tagging of the calcareous feeding lanterns." This effort revealed that (1) "average-sized urchins grew more than twice as fast at the vent compared with those at an adjacent control site," and that they (2) "assumed larger sizes at the vent compared to the control site and two other sites at another reef near-by." In addition, they report that there were (3-5) "no differences in mortality, respiration, or degree of test calcification between urchins from the vent and control populations."

In light of these several findings, the Australian, New Zealand and U.S. researchers felt safe in stating that the sea urchins "did not only persist but actually 'thrived' under extreme conditions." And why was this so? Uthicke et al. opine that it was because (6) "increased algal productivity under increased pCO2 provided more food at the vent, resulting in higher growth rates." And in light of this likelihood, they conclude their paper by stating that the processes they studied "are best identified in natural settings ... where ecosystems and individuals are exposed throughout their life to conditions similar to those in future oceans."

Posted 17 January 2017