A transcriptomic analysis of the response of the arctic pteropod Limacina helicina to carbon dioxide-driven seawater acidification

Abstract

Ocean acidification from the uptake of anthropogenic carbon dioxide (CO₂) is regarded as a critical threat particularly to marine calcifying organisms. The arctic pteropod <em>Limacina helicina </em>may be one of the first polar organisms that are expected to display early sensitivity to ocean acidification, but a molecular approach as a foundation for understanding the effect of ocean acidification on this pteropod has rarely been reported. In this study, we examined the sublethal effects of CO₂-driven seawater acidification at the transcriptome level in L. helicina. cDNAs, treated under control (pH 8.2), high-CO₂ (pH 7.5), and extreme-CO₂ (pH 6.5) conditions, generated a total of 31,999,474 reads, comprising a total of 2,271,962,654 bp, using the Illumina platform. De novo assembly yielded 53,121 transcripts comprising 31.79 Mbp. Among the upregulated genes, 346 (0.7 %) and 655 (1.2 %) genes responded to extreme-level CO₂ (pH6.5) and high-levelCO₂ (pH 7.5), respectively. Also, 76 (0.1 %) transcripts were commonly upregulated in both conditions.Among the downregulated genes, 690 (1.3 %) and 739 (1.4 %) genes were in response to extreme-levelCO₂ and high-level CO₂, respectively. Also, 270 downregulated genes (0.5 %) were affected in both acidic stress conditions. Moreover, 504 transcripts (1 %) of biomineralization-related genes were identified; 16 of these genes showed differential expression in response to acidified seawater. The dataset provides the first comprehensive overview of changes in transcript levels in the arctic pteropod<em> L. helicina</em> in response to increased CO₂, emphasizing the potential impact of future environmental change and ocean acidification on Arctic species with external calcified structure