CONICET | Buscador de Institutos y Recursos Humanos

The decrease in the pH of the oceans is one of the consequences of the release of CO2 (carbon dioxide) into theatmosphere by human activities. In estuaries, the magnitude to which pH will change and how the organismsthat inhabit these environments would be affected is today relatively poorly known. We evaluated, by twolaboratory experiments, whether the low pH affects early stages of the semi-terrestrial crab Neohelice granulata,an estuarine and ecosystem engineer species. Firstly, embryos and the spawning larvae were exposed to acidifiedseawater (ambient pH: 7.9 and 8, respectively; 7.5 and 6.9); secondly, ovigerous females were collected from thefield and freshly hatched larvae were cultured under these pHs. We found a slight delay in the development timeof embryos exposed to pH 6.9 but no difference in those reared under intermedial pH (7.5) with respect to thecontrol and 6.9. We also found a reduction in egg volume and eye size exposed at pH 7.5 but with a recovery tonormal size later in development. Heartbeats did not vary with pH. A delay in the duration of the intermoltperiod was observed for both larvae zoea I (ZI) and II (ZII) exposed to pH 6.9 in the first experiment, and only inZI under this pH in the second one. Differences in body morphometry were found in the zoeas analyzed in thefirst experiment but not for the second. Measurements of changes in oxygen concentration conducted in thesecond experiment showed a reduction in the consumption of all zoeae stages when exposed to both low pHs.Mortality of larvae remained constant across treatments. Although it was found that the early stages of thisspecies would be slightly/moderately affected by potential future scenarios of pH decrease, we cannot rule outmajor impacts at the population level, which requires further experiments to be carried out.

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