Abstract
Ocean acidification (OA) may potentially modify the responses of aquatic organisms to other environmental stressors including metals. In this study, we investigated the effects of near-future OA (pCO2 1000 μatm) and mercury (Hg) on the development and reproduction of marine copepod Tigriopus japonicus under multigenerational life-cycle exposure. Metal accumulation as well as seven life history traits (survival rate, sex ratio, developmental time from nauplius to copepodite, developmental time from nauplius to adult, number of clutches, number of nauplii/clutch and fecundity) was quantified for each generation. Hg exposure alone evidently suppressed the number of nauplii/clutch, whereas single OA exposure negligibly affected the seven traits of copepods. However, OA exposure significantly alleviated the Hg inhibitory effects on number of nauplii/clutch and fecundity, which could be explained by the reduced Hg accumulation under OA. Such combined exposure also significantly shortened the development time. Thus, in contrast to earlier findings for other toxic metals, this study demonstrated that OA potentially mitigated the Hg toxicity to some important life traits in marine copepods during multigenerational exposure.
Highlights
Ocean acidification (OA) caused by absorption of increasing anthropogenic CO2, with a continuous decline in pH1 is widely regarded as a major threat to global marine biodiversity
Compared with Hg treatment alone, the combined OA and Hg exposure decreased the total Hg (T-Hg) concentrations by 52, 73, 75, and 83%, respectively, for F0, F1, F2, and F3. These results strongly suggested that CO2 acidified seawater reduced the Hg accumulation in the copepods during multigenerational exposure
The calculated dry-weight concentration factors (DCFs) of Hg in the copepods were 42.1–125.6 L/kg under the single Hg exposure, which was 1–2 orders of magnitude lower than those in other copepods measured in earlier works[38, 39], highlighting the species-specificity for metal bioaccumulation
Summary
Ocean acidification (OA) caused by absorption of increasing anthropogenic CO2, with a continuous decline in pH1 is widely regarded as a major threat to global marine biodiversity. We used the harpacticoid copepod Tigriopus japonicus as a model species given its ease of culture, rapid life cycle and pedigree in ecotoxicological studies including the OA impacting assessments[32,33,34,35]. This copepod inhabits tide pools on rocky shores along the coasts in the Western Pacific including Japan, South Korea, and China[36], and it may have suffered from multi-stresses (e.g., OA and Hg pollution) due to human activities. Seven important life history traits, i.e., survival rate, sex ratio (F/M), developmental time from nauplius to copepodite, developmental time from nauplius to adult, number of clutches, number of nauplii/clutch and fecundity, as well as Hg accumulation, were measured for each generation
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