Investigating gene expression plasticity in pacific oyster (Magallana gigas) larvae subjected to ocean acidification conditions

Authors: YEATS, MARK - Oregon State University; HAINEY, MACKENNA - Oregon State University; LANGDON, CHRIS - Oregon State University; Calla, Bernarda

Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: 3/6/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Reduced pH in ocean waters affects early oyster development. We sought to understand the mechanisms by which lower pH levels affect Pacific oysters. Developing Pacific oyster embryos were subjected to acidified or ambient seawater for 35 days post fertilization. These larvae were assessed for growth and their tissues were analyzed to identify genes that are expressed differentially between those two conditions.

Technical Abstract: In the Anthropocene, human activities have resulted in ocean acidification (OA), prompting the need for new management approaches for commercial production of some marine species, including oysters. On the U. S. Pacific coast, seasonal upwelling of deep, acidified seawater forces oyster hatcheries into buffering of incoming seawater to mitigate larval production losses. In this study, we sought to quantify and evaluate changes in gene expression across early developmental stages in larvae of the widely cultivated Pacific oyster, Magallana gigas (quondam Crassostrea gigas) when exposed to OA conditions. Larvae used in this study were hatchery produced from broodstock oysters that had been exposed to both OA conditions as larvae and heat stress as adults over the period 2019-2023. A control group consisted of sibs from the same stressed pooled families that had not been exposed to OA or heat stress conditions. The fastest growing individuals from both the stressed and non-stressed parental groups were selected for spawning. Developing embryos and larvae from these two parental groups were then exposed to either OA (7.5-7.6 pH) or ambient seawater conditions (8.0-8.1 pH) until 35-days post fertilization (dpf). We found that shell growth was negatively affected by the OA treatment regardless of parental source. At 10 dpf, progeny of stressed parents grew larger relative to offspring produced from non-stressed parents; however, less progeny from stressed parents successfully developed into spat (juveniles) at 35 dpf under both rearing conditions. Sequence libraries were prepared from larvae produced from each parental and seawater treatment group across different developmental stages following exposure to OA or ambient seawater conditions, using Illumina paired-end mRNA-seq. Transcriptome analysis was used to investigate plasticity in gene expression to OA across developmental stages of larval M. gigas up to 10-days post fertilization. The results of this study could lead to the development of sensitive molecular tools to monitor the responses of Pacific oyster larvae to OA stress under both hatchery and field conditions.