Seasonal dynamics of lipophilic marine algal toxins in water body and sediment environments of nearshore mariculture areas in northern China

Lipophilic marine algal toxins (LMATs) pose risks to mariculture industries and human health. This study investigated the seasonal variation of LMATs in water and sediment environments at nearshore mariculture sites in China, in order to facilitate the prevention of LMAT contamination. Eight LMATs, including okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-2 (PTX2), gymnodimine, 13-desmethyl spirolide C, yessotoxin, homo-yessotoxin, and azaspiracid-2 and two derivatives-PTX2 Seco Acid and 7-epi-PTX-2 Seco Acid-were identified across various environmental samples. OA, DTX1, and PTX2 were dominant in Sishili Bay and Rongcheng Nearshore Bays. The composition and concentration of LMATs showed significant seasonal variation in both water and sediments. The total LMAT concentrations (∑LMATs) ranged from 4.20 ng/L to 107.62 ng/L in surface and bottom seawater, 2.01 ng/L to 120.58 ng/L in sediment porewater (mean 27.42 ng/L), and 17.04-490.87 ng/kg in sediments (mean 198.62 ng/kg). In water, LMAT diversity was higher in spring and summer, whereas concentrations peaked in summer and declined in winter. Conversely, ∑LMATs in sediments and porewater displayed a reciprocal seasonal pattern, implying dynamic exchange at the sediment-porewater interface. These findings highlight the seasonal dynamics of LMATs in mariculture sites, providing essential data for evaluating contamination risks during breeding cycle.