Marine organisms are exposed to a wide range of potentially hazardous substances, from natural and/or anthropogenic sources. Organisms in polluted sediments may accumulate high amounts of chemical contaminants and transfer these up the food chain. For a chemical to bioaccumulate, it needs to be bioavailable for accumulation. This study aimed to assess whether digestive fluids from the subsurface feeding polychaete Arenicola marina would affect the bioavailability of sediment-bound PAHs, and compare natural to artificial gut fluids.
Arenicola gut fluid, a BSA solution, an artificial gut fluid and seawater were incubated for 4 hours with two contaminated sediments and control sediment. The supernatants were then analyzed for 19 different PAHs using GC-MS. The solutions were also analyzed for protein content, lipase- and protease activity and surfactant properties. The results showed that the Arenicola gut fluid led to a small increase in the bioavailability of sediment-bound PAHs, and that the artificial gut fluids had a much greater effect on increasing the bioavailability of PAHs than Arenicola gut fluid. This may be partly due to a high Arenicola gut natural content of PAHs. The results also showed that the enzyme activity seemed to have little effect on the bioavailability of the PAHs, while the protein and bile salt content appeared to have a greater impact on the ability of the test solutions to increase the bioavailability of sediment-bound PAHs. The high bioavailability of some of the PAHs such as naphthalene and acenaphthylene may be attributed to their volatility in combination with the ability of the test solutions to increase their bioavailability. The results showed that one may be at risk of overestimating the bioavailability of gut fluids when using artificial gut fluids as a surrogate for real gut fluids when performing bioavailability tests.