Paralytic Shellfish Toxin Congener Profiles in Three Species of Bivalve Molluscs from Resurrection Bay, Alaska, 2021 and 2022
Description
This study assessed PST concentrations and congener profiles in three bivalve species, blue mussels (Mytilus trossulus), softshell clams (Mya arenaria), and cockles (Clinocardium nuttallii), collected from Afognak Beach in Resurrection Bay, Alaska, an important subsistence and recreational harvest site. From spring through fall of 2021 and 2022 bi-weekly sampling events of blue mussels (n = 32), softshell clams (n = 32), and cockles (n = 25) were collected and analyzed using high-performance liquid chromatography post-column oxidation to quantify PST congener profiles and assess potential risks to harvesters. Results showed measurable toxin concentrations in 50% blue mussel samples, 8.3% softshell clam samples, and 0% cockle samples. Across the full study period, the median PST concentration in blue mussels (1.98 µg STX-eq 100 g⁻¹) was significantly higher than in soft-shell clams and cockles (both medians were below the method detection limit). PST profiles were dominated by GTX4 and GTX5, although blue mussels exhibited an interannual shift characterized by increased GTX1 contribution in 2022. All samples tested below the FDA regulatory limit of 80 µg STX-eq 100 g-1. These findings establish a baseline for PST risk in Resurrection Bay and highlight the importance of ongoing monitoring to ensure safe shellfish harvests in a changing climate.