Marine Phycotoxins in a Benthic-Dominated Subtropical Food Web: Occurrence, Bioaccumulation and Trophic Transfer

Marine phycotoxins (MPs) produced by harmful algal species cause thousands of seafood poisoning cases worldwide each year, yet their bioaccumulation and trophic transfer remain poorly characterized. We investigated the occurrence, bioaccumulation, and trophic transfer of nine MPs spanning both hydrophilic and lipophilic classes in a benthic-dominated subtropical marine food web. Cyclic imine toxins were frequently detected in marine organisms, with gymnodimine-A (GYM-A) showing the highest detection frequency (64.0%). Among the analyzed MPs, domoic acid (DA) showed the highest concentration, reaching 6.80 ng/g wet weight (ww) in fish. Mean total concentrations of the nine MPs were 1.42 ng/g ww in fish, 0.99 ng/g ww in crustaceans, and 0.62 ng/g ww in cephalopods. Dinophysistoxin-1 (DTX1) showed strong bioaccumulation, with a bioaccumulation factor (BAF) of 5071 in Cynoglossus puncticeps. Average biota-sediment accumulation factors (BSAFs) for DTX1, dinophysistoxin-2 (DTX2), and okadaic acid (OA) were 15.92, 5.79, and 5.28, respectively, indicating substantial sediment-associated uptake. DTX2 also showed trophic magnification, with a trophic magnification factor (TMF) of 1.90. Estimated hazard quotients (HQs) for all MPs were below 1, suggesting negligible health risks from local seafood consumption. These results demonstrate that both sediment uptake and food-web transfer contribute to phycotoxin accumulation in subtropical marine organisms.