Abstract
Ocean acidification (OA) is usually thought to change the speciation of trace metals and increase the concentration of free metal ions, hence elevating metal bioavailability. In this study, embryos of the oysterCrassostrea angulataand abaloneHaliotis discus hannaiwere cultured under 4 pCO2conditions (400, 800, 1500 and 2000 µatm) with Cu and Zn added. Fertilization rate was measured 2 h post-fertilization (hpf), while larval deformation and larval shell length were measured 24 hpf. Our results show that OA can alleviate Cu and Zn inhibition ofC. angulatafertilization by 86.1 and 26.4% respectively, and Zn inhibition ofH. discus hannaifertilization by 43.7%. However, OA enhanced the inhibitory effect of Cu on fertilization ofH. discus hannaiby 34.7%. OA enhanced the toxic effect of Cu on larval normality ofC. angulataby 22.0% and the effect of Cu and Zn on larval normality ofH. discus hannaiby 71.4 and 37.2%, respectively. OA also enhanced the inhibitory effects of Cu and Zn on larval calcification inH. discus hannaiby 8.8 and 8.6%, respectively. However, OA did not change the effect of Cu on the calcification ofC. angulatalarvae. OA decreased Zn inhibition of oyster larval calcification from 3.1 to 1.5%. Based on our results, the toxic effects of metal on early development of molluscs are not always increased by rising pCO2and differ across developmental stages, egg structure and species. This complexity suggests that caution should be taken when carrying out multiple environmental stressor tests on molluscan embryos.
Highlights
Carbon dioxide (CO2) discharged by anthropogenic activities has caused a sharp increase in atmospheric CO2
There was an interaction between ocean acidification (OA) and the effect of Cu on fertilization of H. discus hannai (2-way ANOVA, F15,72 = 6.3, p < 0.001; Table 2)
Inhibition of fertilization under high-pCO2 conditions occurs in different marine invertebrates (Morita et al 2010, Moulin et al 2011, Reuter et al 2011, Barros et al 2013, Foo et al 2014)
Summary
Carbon dioxide (CO2) discharged by anthropogenic activities has caused a sharp increase in atmospheric CO2. In addition to OA, trace metals are another environmental threat, and toxicity of trace metals to marine molluscan embryos and larvae has been studied in oysters Crassostrea virginica (Calabrese et al 1977), mussels Mytilus edulis (Johnson 1988) and abalone Haliotis rubra (Gorski & Nugegoda 2006). In contrast to predictions that OA would increase the toxicity of some trace metals (Millero et al 2009), the results of these studies showed complex responses of marine organisms to the combined influence of OA and trace metals. The combined effects of OA and trace metals (Cu and Zn) on embryos and larvae of oysters C. angulata and abalone H. discus hannai were studied to test whether OA could aggravate trace metal toxicity in molluscs. CO2-enriched air was bubbled into 0.22 μm filtered seawater (FSW) to
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