Highlights
• We deploy identical populations of sea urchin embryos in lab and field ocean acidification scenarios.
• Acidification had opposite effects on larval growth in the lab and in the field.
• Results of ocean acidification lab studies may not necessarily scale to field conditions.
Abstract
Understanding the extent to which laboratory findings of low pH on marine organisms can be extrapolated to the natural environment is key towards making better projections on the impacts of global change on marine ecosystems. We simultaneously exposed larvae of the sea urchin Arbacia lixula to ocean acidification in laboratory and natural CO2 vents and assessed the arm growth response as a proxy of net calcification. Populations of embryos were simultaneously placed at both control and volcanic CO2 vent sites in Ischia (Italy), with a parallel group maintained in the laboratory in control and low pH treatments corresponding to the mean pH levels of the field sites. As expected, larvae grown at constant low pH (pHT 7.8) in the laboratory exhibited reduced arm growth, but counter to expectations, the larvae that developed at the low pH vent site (pHT 7.33–7.99) had the longest arms. The larvae at the control field site (pHT 7.87–7.99) grew at a similar rate to laboratory controls. Salinity, temperature, oxygen and flow regimes were comparable between control and vent sites; however, chlorophyll a levels and particulate organic carbon were higher at the vent site than at the control field site. Thus, increased food availability may have modulated the effects of low pH, creating an opposite calcification response in the laboratory and the field. Divergent responses of the same larval populations developing in laboratory and field environments show the importance of considering larval phenotypic plasticity and complex interactions between decreased pH, food availability and larval responses.
Foo S. A., Koweek D. A., Munari M., Gambi M. C., Byrne M. & Caldeira K., in press. Responses of sea urchin larvae to field and laboratory acidification. Science of The Total Environment. Article.
