| 英文摘要: | Anthropogenic CO2 is a major driver of present environmental change in most ecosystems1, and the related ocean acidification is threatening marine biota2. With increasing pCO2, calcification rates of several species decrease3, although cases of upregulation are observed4. Here, we show that biological control over mineralization relates to species abundance along a natural pH gradient. As pCO2 increased, the mineralogy of a scleractinian coral (Balanophyllia europaea) and a mollusc (Vermetus triqueter) did not change. In contrast, two calcifying algae (Padina pavonica and Acetabularia acetabulum) reduced and changed mineralization with increasing pCO2, from aragonite to the less soluble calcium sulphates and whewellite, respectively. As pCO2 increased, the coral and mollusc abundance was severely reduced, with both species disappearing at pH < 7.8. Conversely, the two calcifying and a non-calcifying algae (Lobophora variegata) showed less severe or no reductions with increasing pCO2, and were all found at the lowest pH site. The mineralization response to decreasing pH suggests a link with the degree of control over the biomineralization process by the organism, as only species with lower control managed to thrive in the lowest pH. Several studies on the influence of pH on crystallography and texture of calcified regions are ex situ, short-term experiments on isolated organisms5, providing important information, but unrepresentative of natural ecosystems and failing to assess long-term effects6. There is a great need for long-term analyses on ocean acidification effects on marine ecosystems acclimated to high pCO2, as found around CO2 vents. Vents are not perfect predictors of future oceans, owing to pH variability, proximity of unaffected populations, and co-varying environmental parameters7. However, vents acidify sea water on sufficiently large temporal and spatial scales to integrate ecosystem processes6, acting as ‘natural laboratories’. In Papua New Guinea vents, reductions in coral diversity, recruitment and abundance, and shifts in competitive interactions, are found8. In Mediterranean vents, decreased diversity, biomass, trophic complexity and abundance in many calcifying and non-calcifying organisms, and increases in macroalgae and seagrasses, are observed7, 9, 10. We assessed, along a natural pH gradient, the effect of pCO2 on the mineralization and abundances of the aragonitic scleractinian B. europaea, the aragonitic tube-forming gastropod V. triqueter, the brown alga P. pavonica, which deposits aragonite on the thalli surface, the green alga A. acetabulum, whose cups’ outer surfaces are calcified with aragonite and a small amount of whewellite (calcium oxalate), and the non-mineralized brown alga L. variegata. The mineralization is biologically controlled in V. triqueter (that is, mineral is deposited in confined nucleation sites under complete biological control with minimal environmental effects), biologically induced in P. pavonica and A. acetabulum (that is, it is strongly affected by the environment with minimal biological control), whereas B. europaea may represent an intermediate and still controversial situation11. We aimed to assess changes in the mineralization and abundance of species along a pCO2 gradient in relation to their control over biomineralization. Mean pH, CO2, saturation of calcite (Ωcalc), and of aragonite (Ωarag) differed among Sites (Kruskal–Wallis test/analysis of variance, p < 0.001). The median pH values were 8.1 (Site 1), 7.9 (Site 2), 7.8 (Site 3) and 7.7 (Site 4), with increasing variability towards Site 4 (Fig. 1 and Supplementary Fig. 1 and Table 1).
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