Along the US West Coast, climate change is intensifying and prolonging the upwelling of low-pH seawater, which is particularly harmful to calcifying organisms like shellfish. Commercial oyster hatcheries, such as the Whiskey Creek Shellfish Hatchery, Netarts Bay, Oregon, have faced reduced oyster seed production during periods of coastal upwelling of seawater with low aragonite saturation states (Ωarag).
This presentation describes a multi-generational experiment investigating OA effects on Pacific oyster (Crassostrea gigas) larvae. These larvae were produced from stressed or non-stressed parental broodstock and reared in the Hatfield Ultra Larval Density System (HUDLS) that provides consistent flow-through culture conditions (Figure 1). Stressed parental broodstock had been subjected to hatchery OA stress as larvae and heat stress as adults at an intertidal field site. Non-stressed parental broodstock had been reared under normal hatchery conditions as larvae and at a subtidal field site as adults. The fastest-growing parental oysters were genotyped from each group, and unrelated individuals crossed to produce two groups of larvae that were reared in either acidified (7.5-7.6 pHt) or normal (8.0-8.1 pHt) seawater in the HUDLS.
We found an adverse effect of OA on shell growth at 1-day and 10-day post-fertilization (dpf), regardless of parental stress exposure; furthermore, 10-dpf larvae from stressed parents reared in acidified conditions were significantly larger than those from non-stressed parents. A higher proportion of larvae from non-stressed versus stressed parents were retained (a measure of viability) at all stages and treatments, with significant differences observed under OA conditions. The larvae from stressed parents exhibited significantly lower metamorphic success, resulting in lower spat yields from stressed parents under all seawater conditions at 35 days post-fertilization (dpf).
These results indicate that parental stress during larval (OA) and adult (heat) stages adversely affected the production of offspring.