Trace element concentrations and tissue distribution in cetaceans from different ecological groups in Chinese waters

As long-lived marine predators occupying high trophic levels, cetaceans can serve as important bioindicators for assessing trace element (TE) contamination in marine ecosystems. In this study, concentrations of 12 TEs (As, Ba, Cd, Co, Cu, Li, Mn, Pb, Rb, Se, Sr, and Zn) were measured in liver and muscle tissues of six stranded cetacean species from the Fujian coast, China. Tissue-, species-, and ecological group-related differences in accumulation patterns were compared, and temporal changes of TEs in Indo-Pacific humpback dolphins from Xiamen Bay were further assessed. Most TEs occurred at higher concentrations in liver than muscle, indicating liver is a key storage tissue. Species-specific accumulation patterns were also observed, particularly in Blainville's beaked whales, which differed significantly from finless porpoises and Indo-Pacific humpback dolphins and showed higher Cd and Se concentrations. Differences in elemental composition were observed among ecological groups, suggesting that habitat use and prey composition may influence exposure sources and accumulation patterns. Due to limited samples, no statistically significant temporal trends were detected in Indo-Pacific humpback dolphins. However, fitted curves and historical comparisons indicated that Cd, Pb, Zn, and Cu decreased at relatively low levels, whereas Co may warrant further attention. This study provides baseline data for TE contamination in cetaceans from the Fujian coast and supports the utility of cetaceans with different ecological strategies in monitoring TE contamination. Opportunistic stranded samples result in limited, uneven sample sizes across species and tissues; interspecific and ecological group differences require validation with larger balanced datasets in future.