Researchers from Korea Maritime & Ocean University, in Busan, South Korea revealed that exposure to higher levels of benzo[α]pyrene (BaP) slowed immune response in bay scallops and lowered their capacity to deal with oxidative stress and DNA damage.
BaP is a carcinogenic polycyclic aromatic hydrocarbon (PAH), and one of the most common pollutants released into the sea. They are formed by incomplete combustion of organic matter, including wood and fossil fuels. They are not water soluble, but attach to fine silt at the ocean bottom, where they may be consumed by shellfish.
PAHs disrupt a variety of biologic systems in marine creatures, including energy metabolism, growth, genetics, and reproduction. Exposure to these compounds causes toxicity not only in marine organisms, but also in humans who consume these organisms. Although the immunotoxicity of PAHs has been extensively studied in mammals and fish, its influence on shellfish has not been adequately investigated.
To fill this knowledge gap, a group of researchers. including Korea Maritime and Ocean University Professor Cheol Young Choi, evaluated the toxicological effects of BaP – a known carcinogen on bay scallops. The resulting paper was made available online on 27 April, and subsequently published in Fish and Shellfish Immunology in May.
The researchers exposed the scallops to seawater containing four different concentrations of BaP – 0.5, 1.0, 10, and 50 micrograms per liter – for 72 hours, then measured five different parameters in these scallops to analyze the organisms’ stress and immune system responses.
The study found except for the lowest exposure group, the proteins indicating immune response rose considerably with time in each group for 6 to 24 hours before declining. At 72 hours, the highest exposure group had indicators showing excess stress.
From the observations, the researchers concluded that BaP dampens the immune response of scallops and decreases their capacity to respond to oxidative stress, infection, inflammation, and tissue damage.
The research is highly relevant to Japan’s scallop industry, which harvests thousands of metric tons of the species each year. Aomori, Japan, for example, produced a record 67,000 MT of scallops in 2019, and the species represents one of the most valuable seafood exports from Japan.
Image courtesy of the Korea Maritime & Ocean University