Effect of Carbonate Chemistry Alteration on the Early Embryonic Development of the Pacific Oyster (Crassostrea gigas)

Abstract

Ocean acidification, due to anthropogenic CO2 absorption by the ocean, may have profound impacts on marine biota. Calcareous organisms are expected to be particularly sensitive due to the decreasing availability of carbonate ions driven by decreasing pH levels. Recently, some studies focused on the early life stages of mollusks that are supposedly more sensitive to environmental disturbances than adult stages. Although these studies have shown decreased growth rates and increased proportions of abnormal development under low pH conditions, they did not allow attribution to pH induced changes in physiology or changes due to a decrease in aragonite saturation state. This study aims to assess the impact of several carbonate-system perturbations on the growth of Pacific oyster (Crassostrea gigas) larvae during the first 3 days of development (until shelled D-veliger larvae). Seawater with five different chemistries was obtained by separately manipulating pH, total alkalinity and aragonite saturation state (calcium addition). Results showed that the developmental success and growth rates were not directly affected by changes in pH or aragonite saturation state but were highly correlated with the availability of carbonate ions. In contrast to previous studies, both developmental success into viable D-shaped larvae and growth rates were not significantly altered as long as carbonate ion concentrations were above aragonite saturation levels, but they strongly decreased below saturation levels. These results suggest that the mechanisms used by these organisms to regulate calcification rates are not efficient enough to compensate for the low availability of carbonate ions under corrosive conditions.

Reconsidering the role of carbonate ion concentration in calcification by marine organisms

“…9 and 12). This is illustrated with data from three publications where the influence of different carbonate-chemistry parameters on calcification rates was disentangled (Schneider and Erez, 2006;Gazeau et al, 2011;Keul et al, 2013;Fig. 2).…”

“…For further details on the model setup, please refer to the original description by Taucher and Oschlies (2011). (Gazeau et al, 2011). Panels (c, d): size-normalized weight (SNW) of the foraminifer Ammonia sp.…”

“…Calcification related measurements and corresponding DIC, TA, T , S, and nutrient data of experiments with different species (Schneider and Erez, 2006;Gazeau et al, 2011;Keul et al, 2013, Fig. 2) were downloaded from the PAN-GAEA data server (www.pangaea.de).…”

“…HCO − 3 is dominant and has a relatively stable concentration in this entire pH range, while [CO 2− 3 ] is highly variable. In the habitat of a temperate coralline alga, for example, typical diurnal pH fluctuations can range from ∼ 8.4 at day to ∼ 7.6 at night (Cornwall et al, 2013 de Putron et al, 2011;Gazeau et al, 2011;Keul et al, 2013;Waldbusser et al, 2014 Eqs. 9 and 12).…”

“…Several physiological studies with different calcifying taxa have addressed these questions by setting up experiments where the influence of individual carbonate system parameters could be studied in isolation. Some of these studies found the best correlations of calcification rates with [CO 2− 3 ] and CaCO 3 (e.g., Schneider and Erez, 2006;Gazeau et al, 2011;de Putron et al, 2011;Keul et al, 2013;Waldbusser et al, 2014), while others highlighted the importance of [HCO − 3 ] (e.g., Buitenhuis et al, 1999;Jury et al, 2010). Still others found that the response is not controlled by a single carbonate system parameter, but by the interplay of two or more.…”