Increasing
human activities are altering marine ecosystems, which
may have ramifications for predator feeding ecology and, thus, the
degree of contaminant exposure. We conducted the first investigation
of spatiotemporal trends for nine alternative halogenated flame retardants
(AHFRs) and their relations with dietary variations in 128 humpback
dolphins that were stranded along the northern South China Sea during
2003–2020. We detected the highest levels of seven major AHFRs
in humpback dolphins compared with the results reported in cetaceans
globally, indicating high AHFR contamination in coastal regions of
South China. Dolphins that were stranded near urban regions generally
contained higher AHFR concentrations than those that were stranded
near rural areas, mirroring the environmental trends of AHFRs occurring
in this area. Model-generated diet estimates suggested that humpback
dolphins have reduced their consumption of high trophic-level prey
in recent years, likely attributable to overfishing-induced prey decline
in this region. After adjusting AHFR concentrations due to diet changes,
the temporal trends of AHFR contamination in humpback dolphins were
only slightly altered. Our results suggest that increasing discharges
of AHFRs into the South China Sea during the 2000s and 2010s may have
had a greater influence on AHFR trends in humpback dolphins than dietary
shifts.
Marine mammals often accumulate high levels of environmental
contaminants,
even those that are globally regulated regarding usage, raising concerns
about their health status. Here, we conducted the first investigation
of tissue distribution, spatiotemporal trends, and potential risks
of six organotin compounds (OTs) in Indo-Pacific humpback dolphins
(n = 101) from the northern South China Sea during
2003–2021. We detected the highest level of hepatic triphenyltin
in these humpback dolphins compared with the results reported in cetaceans
globally, and the liver accumulated the highest OT concentrations
than other analyzed tissues. Despite the downward trend of butyltins
in humpback dolphins after the global ban on the use of OTs as antifouling
paints, levels of phenyltins have continued to increase over the past
20 years, suggesting that the other applications of phenyltins in
South China remain prevalent. In vitro and in vivo analyses revealed
that tissue-relevant doses of OTs could induce agonistic effects on
the dolphin peroxisome proliferator-activated receptor γ as
a master regulator of lipid homeostasis and altered the dolphin fatty
acid profiles. Our results highlight the lipid-disrupting effects
of current OT exposure in humpback dolphins and emphasize the need
for further efforts to eliminate OT contamination in South China.
The potential risks of per-and polyfluoroalkyl substance (PFAS) accumulation in nearshore dolphins are not well understood. Here, transcriptional activities of 12 PFAS on peroxisome proliferator-activated receptors (PPAR-α, -β/δ, and -γ) in Indo-Pacific humpback dolphins (Sousa chinensis) were evaluated. All PFAS activated scPPAR-α in a dose-dependent manner. PFHpA exhibited the highest induction equivalency factors (IEFs). The order of IEFs for other PFAS was as follows: PFOA > PFNA > PFHxA > PFPeA > PFHxS > PFBA > PFOS > PFBuS ≈ PFDA ≫ PFUnDA and PFDoDA (not activated). The total induction equivalents (∑IEQs, 5537 ng/g wet weight) indicated that more attention should be paid to investigating contamination levels in dolphins, especially in PFOS (82.8% contribution to the ∑IEQs). The scPPAR-β/δ and -γ were not affected by any PFAS, except for PFOS, PFNA, and PFDA. Furthermore, PFNA and PFDA could induce higher PPARβ/δ and PPAR-γ-mediated transcriptional activities than PFOA. Compared to human beings, PFAS might be more potent PPAR-α activators in humpback dolphins, suggesting that the dolphins may be more susceptible to the adverse effects of PFAS. Our results may be instructive for understanding the impacts of PFAS on marine mammal health due to the identical PPAR ligand-binding domain.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.