Distribution, partitioning, and seasonal variation of lipophilic marine algal toxins in aquatic environments of a typical semi-closed mariculture bay

Lipophilic marine algal toxins (LMATs) pose a potential threat to the health of marine shellfish consumers and marine breeding industries. In this study, LMATs in dissolved phases (DP) and particulate phases (PP) in the seawater of Jiaozhou Bay were accurately determined over four seasons to understand their composition, level, phase partitioning, spatiotemporal variation, and potential sources in aquatic environments of a typical semi-closed mariculture bay. Various LMATs, such as okadaic acid (OA), dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2), gymnodimine (GYM), 13-desmethyl spirolide C (SPX1), pectenotoxin-2 (PTX2), pectenotoxin-2 seco acid (PTX2 SA), and pectenotoxin-11 (PTX11), were detected in DP and PP; of these, OA and PTX2 were the dominant LMATs in DP and PP, respectively. The average proportion of ΣLMATs in DP (97.5%) was significantly higher than that in PP (2.5%), which indicates that LMATs are predominantly partitioned into DP. The total concentrations of LMATs in DP ranged from 4.16 ng/L to 23.19 ng/L (mean, 13.35 ng/L) over four seasons. The highest levels of LMATs in DP and PP were found in summer (mean, 16.71 ng/L) and spring, respectively, while the maximum variety of LMATs was found in autumn. This result suggests that seasonal changes could influence the composition, concentration, and phase partitioning of LMATs in aquatic environments of a coastal semi-closed mariculture bay. ΣLMAT concentrations were higher in the western region than in the eastern region of the bay, where shellfish may have a greater risk of exposure. Dinophysis acuminata, Dinophysis fortii, and Prorocentrum minimum were the potential sources of LMATs in the aquaculture seawater. Overall, various LMATs occurred in the semi-closed mariculture bay, and the persistence and bioavailability of these toxins in aquaculture seawater should be determined in future research.