Ocean acidification (OA) directly impacts marine calcifying organisms including ecologically and commercially important shellfish species such as Arctica islandica (A. islandica). To test whether documented growth resilience of A. islandica to OA is a general response across ages and populations or a function of adaptation to local habitat, we cultured juvenile and adult clams collected from an environment with little pH variation under four pH levels (7.5, 7.7, 7.9, and 8.1) for three months and integrated our understanding with relevant literature. The average shell growth over the experiment among all (69) individuals was 57 ± 55 μm, and there were no statistically significant differences in growth among pH treatments, including the control treatment, despite the general growth rate differences between juveniles and adults. Our results show that A. islandica can maintain its shell growth even in aragonite undersaturated (Ω < 1) conditions (0.65 and 0.83 for pH 7.5 and 7.7 treatments, respectively), supporting the hypothesis that resistance to OA conditions is likely a generalized response across populations. Although the present results show A. islandica can maintain their shell growth under short-term OA, long-term impacts of OA on A. islandica shell growth and other physical parameters including shell density and microstructure are still needed to better assess the sustainability of A. islandica in a more acidified future and to provide guidance on managing this important shellfish stock.

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2022) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2023-03-29.