Accumulation of Chemical Elements in the Dominant Species of Copepods in the Ob Estuary and the Adjacent Shelf of the Kara Sea

Studies were carried out in the Ob River estuary and at the adjacent shelf of the Kara Sea. The concentrations of organic carbon, lipids, major elements (Na, Mg, P, S, K, and Ca), trace elements (Li, Be, B, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Mo, Ag, Cd, Sb, Cs, Ba, Hg, Tl, Pb, Bi, Th, and U), and rare-earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) were determined in the dominant species of mesozooplankton (Senecella siberica, Limnocalanus macrurus, and Calanus spp.). The similarities and differences are shown for the chemical compositions of the specimens. Calanus spp. are characterized by a large Li accumulation with concentrations similar to 350 times higher than those in S. siberica and L. macrurus. The total accumulation of chemical elements per unit volume is higher in L. macrurus than in S. siberica and Calanus spp., amounting to 6.63, 0.69, and 0.41 mg, respectively. The intensity of biological accumulation and the spatial disposition of the area of maximum accumulation of elements in the zooplankton community within the boundaries of the Ob River estuary depend on the hydrophysical conditions. Postmortem variations in the concentrations of chemical elements in dead L. macrurus are characterized by a multidirectional nature. The revealed distinctions of the chemical compositions in live and dead L. macrurus represent the features of lifetime and postmortem concentrations of elements.