Distribution of trace element concentrations in invertebrate species collected from Tokyo Bay, Japan

Three bivalves, Cyclina sinensis (n=6), Crassostrea gigas (n=7), and Mactra veneriformis (n=6), and three crustaceans, Hemigrapsus penicillatus (n=5), Macrophthalmus japonicus (n=5), and Pyrhila pisum (n=5), were collected at Haneda in June 2019. In July 2019, M. veneriformis (n=5) and M. japonicus (n=3) were collected at Kasai. Concentrations of 34 trace elements were analyzed in muscles and internal organs: Li, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Mo, Cd, In, Sn, Sb, Cs, Ba, La, Ce, Gd, Pt, Tl, Pb, and Bi. C. sinensis and M. veneriformis accumulate elements higher in internal organs than muscles. But C. gigas indicates a different accumulation from other bivalves. The strength of hypoxia tolerance may be related to the difference in element distribution among the tissues because C. gigas is exposed to air at low tide, but the other bivalves are not. Moreover, C. sinensis and M. veneriformis accumulated the elements abundant in sediment such as rare earth elements. However, C. gigas accumulated different elements from other bivalves: Cu, Zn, Cd, and Pb. The effect of habitat, in or above the sediment, seemed related to the accumulated element composition. While crustaceans accumulated elements higher in the hepatopancreas than in muscles. In crustaceans, detritus-eating or carnivorous feeding may have affected the accumulated element composition. Most elements, except Mg, K, Ca, and Sr, in the hepatopancreas of H. penicillatus and M. japonicus had higher concentrations than in P. pisum. The detritus-eating in crustaceans was likely to result in accumulating elements with microplastics as one of their origins, e.g., Al, Mn, Co, Cu, Ba, and Pb. Moreover, all invertebrates in Haneda accumulated higher concentrations of Zn than in other studies—likely due to industrial wastes and tires disposed of in Haneda. Additionally, most high-toxicity element concentrations in Kasai were at similar or higher levels than in Haneda. Thallium was only detected in Kasai and was higher than in other studies. Thus, different trace element distributions were suggested among sites in Tokyo Bay.