Long-term retention of paralytic shellfish toxins in a Pacific Arctic bivalve population

Massive and highly toxic blooms of the dinoflagellate Alexandrium catenella have raised widespread concern about ecosystem health and food security in Pacific Arctic waters. The paralytic shellfish toxins (PSTs) produced by this species are now detected widely throughout the regional food web, yet persistence of these toxins within the ecosystem following a bloom has remained largely uncharacterized. In this study, we evaluated toxin retention in the bivalve species Macoma calcarea, a key member of the Pacific Arctic benthic community which is consumed by marine mammals and seabirds. Over three years (2022-2024), high performance liquid chromatography (HPLC) was used to measure PST content of Macoma collected from the southern Chukchi Sea, as well as two cohorts maintained under long-term (∼1 year) laboratory depuration conditions. Results from these analyses revealed that Macoma retain PSTs for over a year following bloom exposure, allowing this species to serve as a long-term reservoir for phycotoxins in the Pacific Arctic food web. The relative toxin profiles of Macoma changed significantly over time and were distinctly different from the algal population, indicative of biotransformation and/or differential retention. Moving forward, continued investigation of toxin dynamics in Arctic taxa will be essential in assessing risks related to bloom events in Pacific Arctic waters.