Factors affecting mercury accumulation and toxicological risk in bottlenose dolphins (Tursiops sp.) within a mercury hotspot.
Article
Paz, Valeria, Barcia, Laura Garcia, Kiszka, Jeremy J et al. (2026). Factors affecting mercury accumulation and toxicological risk in bottlenose dolphins (Tursiops sp.) within a mercury hotspot.
. Environmental Research, 311(Pt 1), 126068. 10.1016/j.envres.2026.126068
Paz, Valeria, Barcia, Laura Garcia, Kiszka, Jeremy J et al. (2026). Factors affecting mercury accumulation and toxicological risk in bottlenose dolphins (Tursiops sp.) within a mercury hotspot.
. Environmental Research, 311(Pt 1), 126068. 10.1016/j.envres.2026.126068
Mercury (Hg) accumulation in marine ecosystems is a global concern, yet its toxicity can be mitigated by selenium (Se). Despite this important antagonistic relationship, Hg:Se dynamics remain poorly understood in free-ranging cetaceans, which serve as valuable sentinels of ecosystem contamination due to their long lifespans and high trophic positions. We quantified total Hg (THg), methylmercury (MeHg) and Se accumulation in skin tissues of bottlenose dolphins (Tursiops sp.) across sex, estimated age, and sampling locations in the Florida Coastal Everglades, South Florida, USA - a mercury hotspot. We also explored how THg and Se concentrations varied with dolphin trophic ecology inferred by δ13C and δ15N values and spatiotemporal variation in THg and Se concentrations of potential prey. THg and Se were positively correlated with δ15N values, indicating an effect of relative trophic level. Also, individuals feeding more heavily in estuarine and freshwater food webs (inferred from δ13C values of dolphins and prey) exhibited higher THg accumulation, which matched spatial patterns of THg concentrations. Methylmercury comprised the majority of THg in the subset analyzed (78-100%), consistent with THg reflecting the biomagnifying fraction of mercury. Between 55.0% and 68.5% of 89 dolphins exceeded the species-specific estimated threshold for THg-associated liver disease risk. However, all dolphins exhibited Se concentrations high enough to potentially counteract Hg toxicity. Future research should clarify how interactions of Hg and Se influence dolphin health to better assess individual- and population-level consequences of high Hg in coastal Everglades food webs and potential influences of increased freshwater flow expected with ongoing ecosystem restoration.
