The Effects of Aragonite Saturation State on Hatchery-Reared Larvae of the Greenshell Mussel Perna canaliculus.

The major cultured mussel species Perna canaliculus is now supported by hatchery production, providing the opportunity to explore and optimize environmental parameters to enhance production. Other cultured bivalve larvae have demonstrated performance that is directly correlated to the aragonite saturation state (Ω_ar) of their tank water, with low or undersaturated water being detrimental and artificially elevated Ω_ar enhancing productivity. Trials were, therefore, designed to specifically explore Ω_ar sensitivity in preveliger (0–2 days old, prodissoconch I = "PD1″) and veliger (2–21 days old, prodissoconch II = "PD2″) stages of P. canaliculus separately. For the PD1 experiment, commercial incubation tanks (control Ω_ar 1.9) were modified to target Ω_ar 0.5 or 0.8 by elevating pCO₂, or 2.9, 4.5, and ∼7 by the addition of sodium carbonate. In the control environment, 72.8% ± 2.9% of fertilized eggs formed viable "D" veligers within two days; an increased yield of 82.6% ± 3.8% in Ω_ar 4.5 was found to be nonsignificant. In comparison, only 12.7% of the Ω_ar ∼7 and <1% of the Ω_ar 0.5 and 0.8 eggs attained the veliger stage, with the remaining underdeveloped or malformed. By 2 days postfertilization, reactive oxygen species were significantly elevated in the undersaturated treatments, whereas DNA damage, lipid hydroperoxides, and protein carbonyls were significantly higher in the Ω_ar 0.5 and ∼7 treatments. Antioxidant enzyme levels were significantly lower in these extreme treatments, whereas Ω_ar 4.5 larvae showed elevated superoxide dismutase, glutathione reductase, and peroxidase levels. Carry-over effects persisted when veligers were transferred to control conditions, with no net recruitment from undersaturated Ω_ar, 29.4% of eggs surviving to pediveliger under control conditions, compared with 33.2% following Ω_ar 4.5 exposure or 1.9% from Ω_ar ∼7. In the PD2 veliger trial, linear shell growth halved in undersaturated water, but was unaffected by elevation of Ω_ar. Mortality rate was consistent across all treatments, suggesting relative resilience to different Ω_ar. It is recommended that hatcheries trial Ω_ar 4–4.5 enrichment in preveliger incubation water to improve yield and minimize oxidative stress. Preveliger stages present a potential survival bottleneck, and focused research exploring sensitivity to near-future ocean acidification is, therefore, needed. [ABSTRACT FROM AUTHOR]