Effects of ocean acidification on trace element accumulation in the early-life stages of squid Loligo vulgaris

Abstract

The anthropogenic release of carbon dioxide (CO 2) into the atmosphere leads to an increase in the CO 2 partial pressure ( pCO 2) in the ocean, which may reach 950 μatm by the end of the 21st century. The resulting hypercapnia (high pCO 2) and decreasing pH (“ocean acidification”) are expected to have appreciable effects on water-breathing organisms, especially on their early-life stages. For organisms like squid that lay their eggs in coastal areas where the embryo and then paralarva are also exposed to metal contamination, there is a need for information on how ocean acidification may influence trace element bioaccumulation during their development. In this study, we investigated the effects of enhanced levels of pCO 2 (380, 850 and 1500 μatm corresponding to pH T of 8.1, 7.85 and 7.60) on the accumulation of dissolved 110mAg, 109Cd, 57Co, 203Hg, 54Mn and 65Zn radiotracers in the whole egg strand and in the different compartments of the egg of Loligo vulgaris during the embryonic development and also in hatchlings during their first days of paralarval life. Retention properties of the eggshell for 110mAg, 203Hg and 65Zn were affected by the pCO 2 treatments. In the embryo, increasing seawater pCO 2 enhanced the uptake of both 110mAg and 65Zn while 203Hg showed a minimum concentration factor (CF) at the intermediate pCO 2. 65Zn incorporation in statoliths also increased with increasing pCO 2. Conversely, uptake of 109Cd and 54Mn in the embryo decreased as a function of increasing pCO 2. Only the accumulation of 57Co in embryos was not affected by increasing pCO 2. In paralarvae, the CF of 110mAg increased with increasing pCO 2, whereas the 57Co CF was reduced at the highest pCO 2 and 203Hg showed a maximal uptake rate at the intermediate pCO 2. 54Mn and 65Zn accumulation in paralarvae were not significantly modified by hypercapnic conditions. Our results suggest a combined effect of pH on the adsorption and protective properties of the eggshell and of hypercapnia on the metabolism of embryo and paralarvae, both causing changes to the accumulation of metals in the tissues of L. vulgaris.