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Arsenic (As) is the most common toxic substance in the environment, ranking first on the superfund list of hazardous substances, that has created worldwide human health problems. Arsenic is widely distributed in all organisms, and total As concentrations in marine fish are higher than those in freshwater fish. In this study, we investigated the trophic transfer, transformation, and bioavailability of As in three carnivorous marine fish (seabass Lateolabrax japonicus, seabream Acanthopagrus schlegeli and grunt Terapon jarbua) and herbivorous rabbitfish Siganus fuscescens. We demonstracted that different diets had significant effects on As bioavailability and bioaccumulation in marine fish. The bioavailabilty of AsB was higher than that of inorganic As. Inorganic As in both fish was difficult to be transmitted along the food chain, due to their biotransformation in the fish tissue rather than direct accumulation. While AsB was more assimilated than inorganic As, possibly because AsB passed more easily through the apical membrances of the cells of the digestive organs, and was the final storage form of As in the fish tissues. Inorganic As was the main As species in the marine macroalgae, and organic As (mainly arsenobetaine AsB) was the main As species in the marine animals, which resulted in higher As accumulation in seabass than in rabbitfish. At the same time, we found that As occurred biomagnification along the food chain in Daya bay. The TMF were 1.05, 2.30 in the summer and winter, respectively, also mainly because the different diets. The different diets had important influences on the bioaccumulation and trophic transfer potential of As in marine fish. AsB in the diets was more easily transferred and assimilated than inorganic As, and the accumulation of AsB was attributed more to biotransformation than to trophic transfer. Therefore, AsB contributed to the As accumulation in these marine fish.