Changes in the concentration of polycyclic aromatic hydrocarbons in fecal pellets of Marphysa sp. E and reduced mud in the Yoro tidal flat, Japan.

Marphysa sp. E (Annelida, Eunicidae), inhabiting the Yoro tidal flat (inner part of Tokyo Bay, Japan), ingests reduced mud comprising black and high viscosity sediments that contain high levels of polycyclic aromatic hydrocarbons (PAHs); these PAHs are excreted within the fecal pellets. PAH concentration in the fecal pellets rapidly decrease to half its quantity 2 h after its excretion. To investigate their specificity of change, we analyzed the PAHs in fecal pellets and reduced mud using gas chromatography-mass spectrometry. PAH concentration of the fecal pellets was observed to decrease by 46 % in 2 h, whereas that of reduced mud decreased by only 8 % in the same duration. This suggests that the PAH concentration of reduced mud decreases only after passing through the worm's digestive system. These results indicate that Marphysa sp. E contributes to the purification of the tidal flat environment.