Bioaccumulation and metabolic impact of environmental PFAS residue on wild-caught urban wetland tiger snakes (Notechis scutatus).

PFAS contamination of urban waters is widespread but understanding the biological impact of its accumulation is limited to humans and common ecotoxicological model organisms. Here, we combine PFAS exposure and bioaccumulation patterns with whole organism responses and omics-based ecosurveillance methods to investigate the potential impacts of PFAS on a top predator of wetlands, the tiger snake (Notechis scutatus). Tiger snakes (18 male and 17 female) were collected from four wetlands with varying PFAS chemical profiles and concentrations in Perth, Western Australia. Tiger snake livers were tested for 28 known PFAS compounds, and Σ28PFAS in liver tissues ranged between 322 ± 193 µg/kg at the most contaminated site to 1.31 ± 0.86 µg/kg at the least contaminated site. The dominant PFAS compound detected in liver tissues was PFOS. Lower body condition was associated with higher liver PFAS, and male snakes showed signs of high bioaccumulation whereas females showed signs of maternal offloading. Biochemical profiles of snake muscle, fat (adipose tissue), and gonads were analysed using a combination of liquid chromatography triple quadrupole (QqQ) and quadrupole time-of-flight (QToF) mass spectrometry methodologies. Elevated PFAS was associated with enriched energy production and maintenance pathways in the muscle, and had weak associations with energy-related lipids in the fat tissue, and lipids associated with cellular genesis and spermatogenesis in the gonads. These findings demonstrate the bioavailability of urban wetland PFAS in higher-order reptilian predators and suggest a negative impact on snake health and metabolic processes. This research expands on omics-based ecosurveillance tools for informing mechanistic toxicology and contributes to our understanding of the impact of PFAS residue on wildlife health to improve risk management and regulation.

Snake scales record environmental metal(loid) contamination.

Wetland snakes, as top predators, are becoming globally recognised as bioindicators of wetland contamination. Livers are the traditional test organ for contaminant exposure in organisms, but research is moving towards a preference for non-lethal tissue sampling. Snake scales can be used as an indicator of exposure, as many metals bind to the keratin. We used laser ablation with inductively coupled plasma-atomic emission spectroscopy and mass spectrometry (LA-ICP-MS) to quantify the concentrations of 19 metals and metalloids (collectively referred to 'metals' hereafter) in Western tiger snake (Notechis scutatus occidentalis) scales from four wetlands along an urban gradient, and compared them to concentrations measured in captive tiger snake scales. We conducted repeat measures to determine the concentration accuracy of each metal using LA-ICP-MS. Concentrations in wild Western tiger snake scales were significantly higher than in reference tiger snake scales for most metals analysed, suggesting accumulation from environmental exposure. We compared the scale concentrations to sediment concentrations of sampled wetlands, and found inter-site differences between mean concentrations of metals in scales parallel patterns recorded from sediment. Four metals (Mn, As, Se, Sb) had strong positive correlations with liver tissue contents suggesting scale concentrations can be used to infer internal concentrations. By screening for a larger suite of metals than we could using traditional digestive methods, we identified additional metals (Ti, V, Sr, Cs, Tl, Th, U) that may be accumulating to levels of concern in tiger snakes in Perth, Western Australia. This research has progressed the use of LA-ICP-MS for quantifying a suite of metals available in snake scales, and highlights the significance of using wetland snake scales as a non-lethal indicator of environmental contamination.

Toxic time bombs: Frequent detection of anticoagulant rodenticides in urban reptiles at multiple trophic levels.

Anticoagulant rodenticides (ARs) are regularly used around the world to control pest mammals. Second-generation anticoagulant rodenticides (SGARs) are highly persistent in biological tissue and have a high potential for bioaccumulation and biomagnification. Consequently, exposure and poisoning of non-target organisms has been frequently documented, especially in countries with unregulated AR sales and usage. Most of this research has focussed on rodent-predators, usually raptors and predatory mammals, although exposure has also been documented in invertebrates and insectivorous fauna. Few studies have explored non-target exposure in reptiles, despite species sharing similar trophic positions and dietary preferences to other exposed fauna. We tested three abundant urban reptile species in Perth, Western Australia that differ in diet and trophic tiers for multiple AR exposure, the dugite Pseudonaja affinis (rodent-predator), the bobtail Tiliqua rugosa (omnivore) and the tiger snake Notechis scutatus occidentalis (frog-predator). We found frequent exposure in all three species (91% in dugites, 60% in bobtails and 45% in tiger snakes). Mean combined liver concentrations of ARs of exposed individuals were 0.178 mg/kg in dugites, 0.040 mg/kg in bobtails and 0.009 mg/kg in tiger snakes. High exposure frequency and liver concentration was expected for the dugite. Exposure in the other species is more surprising and implies widespread AR contamination of the food web. We discuss the likelihood of global AR exposure of urban reptiles, highlight the potential for reptiles to be important vectors of ARs in the food web and highlight implications for humans consuming wild reptiles.

The Broad-Scale Analysis of Metals, Trace Elements, Organochlorine Pesticides and Polycyclic Aromatic Hydrocarbons in Wetlands Along an Urban Gradient, and the Use of a High Trophic Snake as a Bioindicator.

Wetlands and their biodiversity are constantly threatened by contaminant pollution from urbanisation. Despite evidence suggesting that snakes are good bioindicators of environmental health, the bioaccumulation of contaminants in reptiles is poorly researched in Australia. We conducted the first broad-scale analysis of 17 metals and trace elements, 21 organochlorine pesticides, and 14 polycyclic aromatic hydrocarbons in the sediments (4 samples per site, December 2018) from four wetlands along an urban gradient in Perth, Western Australia, and from the livers (5 livers per site, February-April 2019) of western tiger snakes Notechis scutatus occidentalis captured at those sites. All 17 metals and trace elements were detected in the sediments of wetlands as well as 16 in the livers of tiger snakes. Arsenic, Cu, Hg, Pb, Se, and Zn were at concentrations exceeding government trigger values in at least one sediment sample. Two organochlorine pesticides and six of seven polycyclic aromatic hydrocarbons were detected in the sediments of a single wetland, all exceeding government trigger values, but were not detected in tiger snakes. Metals and trace elements were generally in higher concentration in sediments and snake livers from more heavily urbanised wetlands. The least urbanised site had some higher concentrations of metals and trace elements, possibly due to agriculture contaminated groundwater. Concentrations of nine metals and trace elements in snake livers were statistically different between sites. Arsenic, Cd, Co, Hg, Mo, Sb, and Se near paralleled the pattern of contamination measured in the wetland sediments; this supports the use of high trophic wetland snakes, such as tiger snakes, as bioindicators of wetland contamination. Contamination sources and impacts on these wetland ecosystems and tiger snakes are discussed herein.