Examining the relationships between blubber steroid hormones and persistent organic pollutants in common bottlenose dolphins

Toxicogenomic assessment of hydroxylated metabolites of PBDEs on cetaceans: An in vitro study

Despite their ban, polybrominated diphenyl ethers (PBDEs) are frequently detected in various environmental compartments including marine and coastal ecosystems due to their persistence, bio-accumulative, high production volumes, and widespread use. One of the major concerns from PBDEs is the transformation products, such as hydroxylated polybrominated diphenyl ethers (OH-BDEs), which are more bioactive than the parent compounds. For example, 6-hydroxy-2,2',4',4-tetrabromodiphenyl ether (6-OH-BDE-47) is a typical metabolite of PBDEs and cause endocrine system disruption, developmental toxicity, and neurotoxicity in different species. Despite being widely detected in marine environments, investigations on the toxicological mechanisms of 6-OH-BDE-47 in cetaceans remain scarce. High concentrations of PBDEs accumulate in cetaceans due to the long lifespan and large fat reserve. The accumulated PBDEs have become the major source of OH-BDEs in cetaceans. We exposed immortalized fibroblast cell lines from the skin of pygmy killer whales (PKW-LWHT) and Indo-Pacific finless porpoises (FP-LWHT) to 6-OH-BDE-47 and analyzed changes in cellular function using transcriptomic data, along with enzymatic activity. Exposure to the body-relevant body burdens of 6-OH-BDE-47 (250 and 500 ng mL-1) significantly decreased cell viability. Differentially expressed genes in FP-LWHT exposed to 6-OH-BDE-47 were primarily enriched in the pathways associated with steroid metabolism. Total cholesterol was decreased by 6-OH-BDE-47, whereas low-density lipoprotein cholesterol and triglyceride levels were significantly increased in FP-LWHT cells. In contrast, glycolysis was the main enriched function of differentially expressed genes in PKW-LWHT cells exposed to 6-OH-BDE-47, and the enzyme activity of phosphofructokinase and hexokinase was upregulated. Thus, even though the cell viability of both cell lines from these two species was significantly suppressed by 6-OH-BDE-47, the cellular response or affected cellular function was different between the Pygmy killer whale and the Indo-Pacific Finless Porpoise, suggesting a diverse response towards OH-BDEs exposure.

Do dietary exposures to multi-class endocrine disrupting chemicals translate into health risks for Gangetic dolphins? An assessment and way forward

Dietary exposure risks of 39 multi-class Endocrine Disrupting Chemicals (EDCs) to the threatened Gangetic dolphins (Platanista gangetica) were investigated in a conservation-priority segment of the Ganga River. Elevated EDCs bioaccumulation was observed across prey fish species, with di(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DnBP) significantly contributing to the EDC burden. The concentrations of persistent organochlorines in prey revealed a shift from dioxin-like polychlorinated biphenyls (PCBs) to non-dioxin-like PCBs. The prevalence of regulated p,p' DDT (Dichlorodiphenyltrichloroethane) and γ-HCH (Lindane) residues suggests regional non-compliance with regulatory standards. The concentration of some EDCs is dependent on the habitat, foraging behavior, trophic level and fish growth. The potential drivers of EDCs contamination in catchment includes agriculture, vehicular emissions, poor solid waste management, textile industry, and high tourist influx. Risk quotients (RQs) based on toxicity reference value were generally below 1, while the RQ derived from the reference dose highlighted a high risk to Gangetic dolphins from DEHP, DDT, DnBP, arsenic, PCBs, mercury, and cadmium, emphasizing the need for their prioritization within monitoring programs. The study also proposes a monitoring framework to provide guidance on monitoring and assessment of chemical contamination in Gangetic dolphin and habitats.

Multiple-component covalent organic frameworks for simultaneous extraction and determination of multitarget pollutants in sea foods

Persistent organic pollutants (POPs), such as perfluoroalkyl and polyfluoroalkyl substances (PFASs), polychlorinated biphenyls (PCBs), and bisphenols (BPs), have been raising global concerns due to their toxic effects on environment and human health. The monitoring of residues of POPs in seafood is crucial for assessing the accumulation of these contaminants in the study area and mitigating potential risks to human health. However, the diversity and complexity of POPs in seafood present significant challenges for their simultaneous detection. Here, a novel multi-component fluoro-functionalized covalent organic framework (OH-F-COF) was designed as SPE adsorbent for simultaneous extraction POPs. On this basis, the recognition and adsorption mechanisms were investigated by molecular simulation. Due to multiple interactions and large specific surface area, OH-F-COF displayed satisfactory coextraction performance for PFASs, PCBs, and BPs. Under optimized conditions, the OH-F-COF sorbent was employed in a strategy of simultaneous extraction and stepwise elution (SESE), in combination with HPLC-MS/MS and GC-MS method, to effectively determined POPs in seafood collected from coastal areas of China. The method obtained low detection limits for BPs (0.0037 -0.0089 ng/g), PFASs (0.0038 -0.0207 ng/g), and PCBs (0.2308 -0.2499 ng/g), respectively. This approach provided new research ideas for analyzing and controlling multitarget POPs in seafood. ENVIRONMENTAL IMPLICATIONS: Persistent organic pollutants (POPs), such as perfluoroalkyl and polyfluoroalkyl substances (PFASs), polychlorinated biphenyls (PCBs), and bisphenols (BPs), have caused serious hazards to human health and ecosystems. Hence, there is a need to develop a quantitative method that can rapidly detect POPs in environmental and food samples. Herein, a novel multi-component fluorine-functionalized covalent organic skeletons (OH-F-COF) were prepared at room temperature, and served as adsorbent for POPs. The SESE-SPE strategy combined with chromatographic techniques was used to achieve a rapid detection of POPs in sea foods from the coastal provinces of China. This method provides a valuable tool for analyzing POPs in environmental and food samples.

Endocrine-Disrupting Chemical Exposure Induces Adverse Effects on the Population Dynamics of the Indo-Pacific Humpback Dolphin

Cetaceans play a pivotal role in maintaining the ecological equilibrium of ocean ecosystems. However, their populations are under global threat from environmental contaminants. Various high levels of endocrine-disrupting chemicals (EDCs) have been detected in cetaceans from the South China Sea, such as the Indo-Pacific humpback dolphins in the Pearl River Estuary (PRE), suggesting potential health risks, while the impacts of endocrine disruptors on the dolphin population remain unclear. This study aims to synthesize the population dynamics of the humpback dolphins in the PRE and their profiles of EDC contaminants from 2005 to 2019, investigating the potential role of EDCs in the population dynamics of humpback dolphins. Our comprehensive analysis indicates a sustained decline in the PRE humpback dolphin population, posing a significant risk of extinction. Variations in sex hormones induced by EDC exposure could potentially impact birth rates, further contributing to the population decline. Anthropogenic activities consistently emerge as the most significant stressor, ranking highest in importance. Conventional EDCs demonstrate more pronounced impacts on the population compared to emerging compounds. Among the conventional pollutants, DDTs take precedence, followed by zinc and chromium. The most impactful emerging EDCs are identified as alkylphenols. Notably, as the profile of EDCs changes, the significance of conventional pollutants may give way to emerging EDCs, presenting a continued challenge to the viability of the humpback dolphin population.

Organohalogen compounds in a hotspot for chemical pollution: Assessment in free-ranging Atlantic spotted dolphins (Stenella frontalis)

The assessment of chemical pollution in free-ranging living mammals is viable using remote biopsies and portrays a comprehensive scenario of environmental health. The Southwestern Atlantic Ocean holds incredible biodiversity, but it is under the constant and invisible threat of persistent organic pollutants (POPs) of anthropogenic origin, such as pesticides, brominated flame retardants, and industrial-use compounds (e.g., PCBs). Thus, this study aimed to assess the bioaccumulation of POPs (PCBs, DDTs, HCB, mirex and PBDEs) and natural organobromine compounds (MeO-BDEs) using gas-chromatography coupled to mass spectrometry in biopsy samples of Atlantic spotted dolphins (Stenella frontalis, n = 20) that inhabit and forage both inside and in adjacent areas to degraded (Guanabara Bay) and conserved (Ilha Grande Bay) coastal bays in the Southeastern Brazil. Among the studied compounds, PCBs were predominant in the contamination profile with median concentration of 97.0 μg.g-1 lipid weight (lw), followed by the sum of the p,p' isomers of DDT, DDD, and DDE of 11.0 μg.g-1 lw, the brominated flame retardants PBDEs of 1.6 μg.g-1 lw, and the other organochlorine pesticides mirex of 0.78 μg.g-1 lw, and HCB of 0.049 μg.g-1 lw. The MeO-BDEs were detected with a median concentration of 22.8 μg.g-1 lw. 85 % of the Atlantic spotted dolphins analyzed in this study presented PCB concentration that exceeded even the less conservative threshold limits for adverse health effects (41 μg.g-1 lw). This study shows that despite the conservation status of preserved bays, cetacean species foraging in these locations are still under increased threat. Hence chemical pollution demands local and global efforts to be mitigated.

Glucocorticoid hormones in relation to environmental exposure to bisphenols and multiclass pesticides among middle aged-women: Results from hair analysis

Bisphenols and pesticides have been shown to alter circulating glucocorticoids levels in animals, but there is limited human data. Moreover, measurements from biological fluids may not be able to reflect long-term status of non-persistent pollutants and glucocorticoids due to the high variability in their levels. Using hair analysis, we examined the associations between glucocorticoid hormones and environmental exposure to multi-class organic pollutants among a healthy female population aged 25-45 years old. Concentrations of four glucocorticoids, four polychlorinated biphenyl congeners (PCBs), seven polybrominated diphenyl ether congeners (PBDEs), two bisphenols and 140 pesticides and their metabolites were measured in hair samples collected from 196 Chinese women living in urban areas. Due to the low detection frequency of some pollutants, associations were explored only on 54 pollutants, i.e. PCB 180, bisphenol A, bisphenol S and 51 pesticides and their metabolites. Using stability-based Lasso regression, there were associations of cortisol, tetrahydrocortisol, cortisone, and tetrahydrocortisone with 14, 10, 13 and 17 biomarkers of exposure to pollutants, respectively, with bisphenol S, p,p'-dichlorodiphenyldichloroethylene, diethyl phosphate, 3,5,6-trichloro-2-pyridinol, thiamethoxam, imidacloprid, fipronil, tebuconazole, trifluralin, pyraclostrobin and 1-(3,4-dichlorophenyl)-3-methylurea being associated with at least three of the four hormones. There were also associations between cortisone/cortisol molar ratio and pollutants, namely dimethyl phosphate, 3-methyl-4-nitrophenol, carbofuran, λ-cyhalothrin, permethrin, fipronil, flusilazole, prometryn and fenuron. Some of these relationships were confirmed by single-pollutant linear regression analyses. Overall, our results suggest that background level of exposure to bisphenols and currently used pesticides may interfere with the glucocorticoid homeostasis in healthy women.

Variations in thyroid hormone levels in endangered St. Lawrence Estuary belugas: Potential linkage with stress and organohalogen contaminant exposure

The St. Lawrence Estuary (SLE) beluga (Delphinapterus leucas) population is highly exposed to an array of contaminants that were identified as one of the causes to the non-recovery of this endangered and declining population. In the last decade, an increasing number of parturition-associated complications and calf mortality has been reported in this population. It was suggested that elevated exposure to organohalogens (e.g., the halogenated flame retardants polybrominated diphenyl ethers [PBDEs]) and stress could play a role in this phenomenon by perturbing thyroid hormones. The objective of this study was to investigate the impact of concentrations of organohalogen contaminants and stress (cortisol levels) on thyroid hormone variations in adult male and female SLE belugas. Because plasma could not be collected in SLE belugas for ethical reasons, skin biopsy (n = 40) was used as a less-invasive alternative matrix to determine organohalogens (PBDEs and other halogenated flame retardants, polychlorinated biphenyls, and organochlorine pesticides), cortisol, and thyroid hormones (triiodothyronine [T3] and thyroxine [T4]), and their metabolites reverse T3 and 3,5-diiodothyronine [3,5-T2]). Cortisol and thyroid hormones were analyzed by ultra-performance liquid chromatography-multiple reactions monitoring mass spectrometry (UPLC-MRM/MS). This method was compared using skin and plasma samples obtained from Arctic belugas. Comparisons of linear models showed that cortisol was a weak predictor for T4, rT3 and 3,5-T2. Specifically, there was a weak significant negative association between T4 and cortisol levels. Moreover, in male SLE belugas, a weak significant positive association was found between T3 and Σ34PBDE concentrations in skin. Our findings suggest that stress (i.e., elevated skin cortisol levels) along with organohalogen exposure (mainly PBDEs) may be associated with thyroid hormone level perturbations in skin of cetaceans.

Combined effects of organochlorine pesticides on type 2 diabetes mellitus: Insights from endocrine disrupting effects of hormones

Association between organochlorine pesticides (OCPs) exposure and type 2 diabetes mellitus (T2DM) remains contradictory, and the evidence is mostly focused on a single exposure. Here, we assessed the associations between individual and combined OCPs exposure and T2DM, and explored the underlying mechanism of sex hormones and the methylation levels of sex hormone receptors in above associations. A case-control study with 1812 participants was performed. Gas chromatography mass spectrometry, liquid chromatography-tandem mass spectrometry, and pyrosequencing were used to measure plasma OCPs, serum sex hormones, and whole blood methylation levels of sex hormone receptors, respectively. Generalized linear models were used to analyze the relationships between OCPs, sex hormones, the methylation levels of sex hormone receptors, and T2DM. Quantile based g-computation (QGC) and Bayesian Kernel Machine Regression (BKMR) were employed to assess the combined OCPs exposure. The roles of sex hormones and the methylation levels of their receptors were evaluated by moderating mediation models. After adjusting for covariates, each unit (2.718 ng/ml) increase in p,p'-DDE was associated with a higher risk of T2DM in males (odds ratio (OR) and 95% confidence interval (CI): 1.066 (1.023, 1.112)). QGC and BKMR showed a positive combined effect in the associations of OCPs mixtures on T2DM among premenopausal females, and positive effects but not statistically significant among males and postmenopausal females. p,p'-DDE was the largest contributor for the positive associations. Furthermore, testosterone mediated 21.149% of the associations of p,p'-DDE with T2DM moderated by the androgen receptor methylation (ARm) located in CpG island 1. Individual and mixtures of OCPs exposure were positively linked to elevated risk of T2DM. Testosterone and ARm may participate in the related processes of OCPs with T2DM, providing new insights into the adverse endocrine effects caused by OCPs and specific pathways for the etiology and control of diabetes.

POPs in long-finned pilot whales mass stranded in Iceland as a proxy for their physiological condition

Long-finned pilot whales (Globicephala melas) are the most frequently stranded cetaceans in the world; however, the predominant drivers of these events are poorly understood. In this study the levels of persistent organic pollutants from pilot whales stranded in North-east Iceland were quantified and compared to historical data and physical parameters to investigate whether contaminant load may have influenced the physiological state of stranded individuals, how these loads fluctuate with sex and age group, and if this is consistent with the literature. Historical comparison was also carried out to discern how pollutant contamination has changed throughout the past few decades. DDE, transnonachlor and PCB-153 were the top three pollutants respectively. The accumulation of POPs was greater on average in immature individuals than adults, whilst among adults, males had higher concentration than females. Moreover, despite an indication of decreasing POP loads throughout the years, knowledge of harmful thresholds remains exceedingly limited.

Cetaceans as bio-indicators revealed the increased risks of triclosan exposure and associated thyroid hormone disruption during the COVID-19 pandemic

The global surge in disinfection practices from the COVID-19 response has raised concerns about the marine exposure to the hazardous ingredients in disinfectant products, including triclosan (TCS) and triclocarban (TCC). However, there are very limited studies on the response of marine TCS and TCC (TCs) loading to the COVID-19 pandemic. Here we used cetaceans as bio-indicators for a long-term retrospective analysis of TCs loading to the South China Sea (SCS) between 2004 and 2022. Hepatic TCs was 100% detected in all nine cetacean species (n = 120). Interestingly, TCS concentrations decreased in Indo-Pacific humpback dolphins (IPHD) before the pandemic from 2010 to 2017. However, after 2019, TCS concentrations in IPHD significantly increased several-fold. Similarly, post-pandemic TCS concentrations in Indo-Pacific finless porpoises (IPFP) and two fish species were significantly higher than pre-pandemic levels. There were significant relationships between thyroid hormones (THs) and TCs in IPHD and IPFP, suggesting that increased TCs may worsen the interference of THs homeostasis and nutritional conditions in cetaceans. These findings demonstrate the profound impact of the surging use of TCs-containing products from the COVID-19 response on marine ecosystems.

Hormonal biomarkers provide insights into the reproductive biology and pollutants-associated health hazards of endangered dolphins

Contaminants are known to contribute to the reproductive health hazards of wildlife, but pollutants-associated detrimental impacts on the endangered Indo-Pacific humpback dolphins (Sousa chinensis, IPHD) are largely unknown due to a lack of reproductive parameters. Here we validated and applied blubber progesterone and testosterone as reproductive biomarkers to assess reproductive parameters of IPHD (n = 72). The gender-specific progesterone concentrations and progesterone/testosterone (P/T) supported progesterone and testosterone as valid biomarkers in identifying the genders of IPHD. Significant month-to-month variations of two hormones indicated a seasonal reproduction, in accordance with the observation of photo-identification approach, further supporting testosterone and progesterone as ideal reproductive biomarkers. Progesterone and testosterone concentrations showed significant differences between Lingding Bay and West-four region, possibly due to chronically geographic-specific pollutants differences. The significant relationships between sex hormones and multiple contaminants suggested that contaminants contribute to the disruption of testosterone and progesterone homeostasis. The best explanatory models between pollutants and hormones suggested that dichlorodiphenyltrichloroethanes (DDTs), lead (Pb) and selenium (Se) were the major risk factors jeopardizing the reproductive health of IPHD. This is the first study on the relationship between pollutant exposure and reproductive hormones in IPHD and represents a substantial advance in understanding the detrimental reproductive impacts of pollutants on endangered cetaceans.

Cetaceans as Bioindicators to Assess Alkylphenol Exposure and Hormone-Disrupting Effects in the South China Sea

Alkylphenols (APs) represent one of the highest exposure levels among endocrine disrupting chemicals (EDCs) in the South China Sea (SCS) due to their extensive use as plastic additives. The concerns about EDCs, including APs, have been reiterated since the surge in plastic waste from the COVID-19 response, but far less is known about the response of AP loadings in the SCS to emerging public policies and activities, including the COVID-19 pandemic. Here, we used cetaceans as bioindicators for monitoring two major APs, 4-nonylphenol (4-NP) and 4-tert-octylphenol (4-t-OP), in nine stranded cetacean species (n = 110) in the SCS between 2004 and 2021. Prior to the COVID-19, APs loads showed decreasing temporal trends for finless porpoises and humpback dolphins, most likely due to China's restrictions on AP use or a shift in dominant prey species. Unexpectedly, AP loads continued to decline after the COVID-19 outbreak, probably due to a temporal-lag response of marine AP fluxes to the pandemic. The health risk assessments based on hormone biomarkers and toxicity thresholds suggest the potential adverse effects of APs on cetaceans, while recent declines in APs, though limited, may mitigate the detrimental impacts.

Bisphenol A alternatives continuously contribute to the endocrine disruption in cetaceans

The bans on bisphenol A (BPA) have facilitated the widespread use of BPA alternatives and shifted environmental contamination profiles of bisphenols (BPs). However, the continued reports of toxicities of emerging BPA alternatives have raised questions about whether the shifting profiles are contributed to mitigate BPs-mediated endocrine-disruption effects (EDEs). Cetaceans are commonly used as the ideal sentinel species for monitoring marine pollutants of concern and determining potential health effects, but far less is known about BP loads and BPs-mediated EDEs in cetaceans. Here we measured the hepatic concentrations of six BPs in eight stranded cetacean species (n = 41) in the South China Sea, between 2007 and 2020. The large-bodied whales generally showed higher ∑BPs concentrations than the small-bodied dolphins. In Indo-Pacific finless porpoises (Neophocaena phocaenoides) (n = 33), BPA concentrations first increased (2007-2014) and then decreased (2014-2020), while ∑BP_Alternatives concentrations increased from 2007 to 2020. It appears that the alternatives gradually replaced BPA, probably due to the BPA-related bans in China. In order to examine the hormone disruption of BPA and its alternatives in finless porpoises, five blubber hormones (cortisol, progesterone, testosterone, triiodothyronine and tetraiodothyronine), which are proven to be validated endocrine biomarkers, were measured in 21 samples. Tetraiodothyronine, testosterone, and cortisol were significantly and positively correlated with BPA and its alternatives, suggesting that the interference of endocrine hormone homeostasis may continue to occur despite the changes of BP profiles in finless porpoises. This is the first investigation of the relationship between hormone and BP concentrations in cetaceans and represents a substantial advance in understanding BPs-mediated endocrine effects on cetaceans.

Franciscana dolphins, Pontoporia blainvillei, as environmental sentinels of the world's largest mining disaster: Temporal trends for organohalogen compounds and their consequences for an endangered population

On November 5th, 2015, the Fundão dam collapsed in Minas Gerais, southeastern Brazil, releasing millions of cubic meters of mud containing mining residue into the Doce River. Two weeks later, the mud arrived to the marine environment, triggering changes in franciscana dolphin habitat, Pontoporia blainvillei, from Franciscana Management Area Ia. This is an isolated population of the most endangered cetacean species in the South Atlantic Ocean. Organohalogen compounds (OHCs) may pose a threat to this endangered population because of their endocrine disrupting properties. Hence, this study sought to determine if there were differences in the bioaccumulation profile of OHC (PCBs, DDTs, Mirex, HCB, HCHs, PBDEs, PBEB, HBBZ and MeO-BDEs) in franciscana dolphins before and after dam collapse and to build a temporal trend. Blubber of 33 stranded individuals was collected in Espírito Santo state for organohalogen assessment between 2003 and 2019. Differences were found between franciscana dolphins collected prior to and after the disaster. Additionally, significant temporal trends for organochlorine pesticides and natural and anthropogenic organobromine were detected. The increase in pesticide concentrations after 2015 is suggestive of their reavailability in the environment. The decline in organobromine over time could be due to their debromination in the marine environment and alterations in the composition of their natural producers. PCBs remained stable during the period of the study. Our findings show an increase in endocrine disruptor concentrations, which is of great concern for this endangered population.

Blubber and serum cortisol concentrations as indicators of the stress response and overall health status in striped dolphins

The impacts of environmental changes and anthropogenic threats in marine mammals are a growing concern for their conservation. In recent years, efforts have been directed to understand how marine mammals cope with stressors and to assess and validate stress biomarkers, mainly levels of glucocorticoid hormones (e.g. cortisol) in certain body tissues. The aims of this study were to assess the impact of different causes of stranding (chronically affected and bycaught striped dolphins) on cortisol concentrations in serum and in blubber; and to evaluate the association between cortisol levels in these tissues. Blubber and blood samples were collected from striped dolphins (n = 42) stranded on the Mediterranean coast between 2012 and 2018. Cortisol concentrations were measured by using enzyme immunoassay. A high correlation was found between circulating and blubber cortisol concentrations (R² = 0.85, p < 0.01). Necropsies and pathological studies concluded that a third of the dolphins were bycaught in fishing nets and released by fishermen (Bycaught animals group), while the other two thirds were euthanized, or died, due to a disease or chronic condition (e.g. calves separated from the mother or animals infected with dolphin morbillivirus or Brucella ceti) that impeded survival (Chronically affected animals group). Cortisol concentrations (mean ± SD) were six times higher in chronically affected animals (35.3 ± 23 ng cortisol/g blubber and 6.63 ± 3.22 μg cortisol/dl serum) compared to those bycaught in fishing nets (6.2 ± 4.3 ng cortisol/g blubber and 1.15 ± 1.51 μg cortisol/dl serum). Results suggests that serum and blubber cortisol concentrations can contribute in inferring the overall health and welfare of free-ranging cetaceans. However, further research is required to understand better the kinetics of blubber cortisol incorporation and removal, the factors involved in these processes, and the local conversion of cortisol in the blubber.

A Correlational Analysis of Phthalate Exposure and Thyroid Hormone Levels in Common Bottlenose Dolphins (Tursiops truncatus) from Sarasota Bay, Florida (2010-2019)

Phthalates are chemical esters used to enhance desirable properties of plastics, personal care, and cleaning products. Phthalates have shown ubiquitous environmental contamination due to their abundant use and propensity to leach from products to which they are added. Following exposure, phthalates are rapidly metabolized and excreted through urine. Common bottlenose dolphins (Tursiops truncatus) sampled from Sarasota Bay, Florida, have demonstrated prevalent di(2-ethylhexyl) phthalate (DEHP) exposure indicated by detectable urinary mono(2-ethylhexyl) phthalate (MEHP) concentrations. Widespread exposure is concerning due to evidence of endocrine disruption from human and laboratory studies. To better understand how phthalate exposure may impact dolphin health, correlations between relevant hormone levels and detectable urinary MEHP concentrations were examined. Hormone concentrations measured via blood serum samples included triiodothyronine (T3), total thyroxine (T4), and free thyroxine (FT4). Urinary MEHP concentrations were detected in 56% of sampled individuals (n = 50; mean = 8.13 ng/mL; s.d. = 15.99 ng/mL). Adult female and male FT4 was significantly correlated with urinary MEHP concentrations (adult female Kendall's tau = 0.36, p = 0.04; adult male Kendall's tau = 0.42, p = 0.02). Evidence from this study suggests DEHP exposure may be impacting thyroid hormone homeostasis. Cumulative effects of other stressors and resultant endocrine impacts are unknown. Further research is warranted to understand potential health implications associated with this relationship.

Blubber Cortisol-Based Approach to Explore the Endocrine Responses of Indo-Pacific Humpback Dolphins (Sousa chinensis) to Diet Shifts and Contaminant Exposure

The detrimental effects of contaminant exposure and changes in the availability of food resources are still of concern for Indo-Pacific humpback dolphins (Sousa chinensis) of the Pearl River Estuary (PRE). Here, we validated and applied a blubber cortisol biomarker approach to assess the physiological responses of PRE dolphins to various pollutants and diet changes during 2008-2018 (n = 70). For calves, generalized additive models (GAMs) revealed that cortisol levels varied significantly by month and were positively correlated with the body length, owing to significant maternal transfer of hormones. The significantly positive correlation between length-adjusted cortisol levels in calf and the annual calf mortality ratios suggested that during years of high calf mortality, these animals were highly stressed before they die. For noncalves, blubber cortisol levels in diseased animals were significantly higher than those in "healthy" ones. Chromium (Cr) and dichlorodiphenyltrichloroethanes displayed a significant and positive relationship with blubber cortisol levels, suggesting that contaminant-mediated endocrine disruption effects may have occurred in noncalves. The GAMs indicated a decreasing trend of noncalf's blubber cortisol levels over an 11-year span, which can be explained by their declining contaminant accumulation levels due to a significant dietary shift from eating highly contaminated fishes to less polluted ones.

Long-Term Consequences of High Polychlorinated Biphenyl Exposure: Projected Decline of Delphinid Populations in a Hotspot for Chemical Pollution

Rough-toothed dolphins, Steno bredanensis, are closely associated with coastal waters in the Southwestern Atlantic Ocean, increasing the exposure to multiple stressors, such as chemical pollution. Persistent organic pollutants (POPs) are known to affect the health of cetacean species. To comprehend the potential impacts of POPs on populations' viability, it is necessary to distinguish populations and predict their risk of long-term exposure. Blubbers of rough-toothed dolphins (n = 28) collected along the southeastern (SE) and southern (S) Brazilian coast were screened for polychlorinated biphenyls (PCBs) and pesticides in a gas chromatograph coupled to a mass spectrometer. Based on the contamination profile, a discriminant function analysis separated the rough-toothed dolphins into three ecological populations: two coastal and one offshore. POP concentrations were the highest reported for the species worldwide and highest among the delphinids in Brazilian waters, reaching 647.9 μg g^-1 lw for PCBs. The SE population presented 212.9 ± 163.0, S population presented 101.0 ± 96.7, and OCS/S population presented 183.3 ± 85.3 μg g^-1 lw (mean ± SD) of PCBs. The potential risk of effects triggered by elevated PCB concentrations was assessed in an individual-based model. A risk of severe decline in population size is projected for the three populations in the next 100 years, especially in SE Brazil, varying between 67 and 99%.

Preliminary Evaluation of Potential Impacts Associated with Small Cetacean Remote Biopsy Sampling by Controlled Testing on Stranded Common Bottlenose Dolphins (Tursiops truncatus)

To explore the potential macroscopic tissue effects of select remote biopsy tools to common bottlenose dolphins (Tursiops truncatus), carcasses were darted and their traumatic effects on the anatomy in target and non-target areas of the body were described. In total, 87 samples were collected (target area, n = 19; non-target area, n = 68) within standardized grid partitions from five carcasses of sub-adult to adult age classes with a range of body condition scores. We broadly classified impacts penetrating completely through the blubber into muscle or deeper internal tissues as over-penetrations (n = 51/87, 59%). For samples collected in the defined target area, there was a low number of over-penetrations (n = 5/51; 10%). However, for samples collected in the defined, non-target areas, a much higher number of over-penetrations occurred (n = 45/51 88%). A visual examination of some samples indicated that sample length and appearance may not be reliable guides to assess the penetration depth of the wounds. These preliminary results suggest samples collected in non-targeted areas could pose much higher risk to the individual. We encourage other researchers considering the use of remote biopsy tools to conduct similar assessments prior to field sampling to better understand the potential consequences of misplaced samples with a view towards continually improving remote biopsy tools and techniques for the benefit of cetacean welfare.

Skin distress associated with xenobiotics exposure: An epigenetic study in the Mediterranean fin whale (Balaenoptera physalus)

The phenotypic plasticity of many organisms is mediated in part by epigenetics, the heritable changes in gene activity that occur without any alterations to DNA sequence. A major mechanism in epigenetics is the DNA methylation (DNAm). Hypo- and hyper-methylation are generalized responses to control gene expression however recent studies have demonstrated that classes of contaminants could mark specific DNAm signatures, that could usefully signal prior environmental exposure. We collected skin and blubber from 6 free-ranging fin whale (Balaenoptera physalus) individuals sampled as a part of a previous published study in the northern Mediterranean Sea. Genomic DNA extracted from the skin of the fin whales and levels of contaminants measured in the blubber of the same individuals were used for DNAm profiling through reduced representation bisulfite sequencing (RRBS). We tested the hypothesis that differences in the methylation patterns could be related to environmental exposure to contaminants and load in the whale tissues. The aims of this study were to determine the DNAm profiles of the methylation contexts (CpGs and non-CpGs) of differently contaminated groups using the RRBS, and to identify potential contaminant exposure related genes. Amount and proportion of methylcytosines in CpG and non-CpG regions (CHH and CHG) was very similar across the 6 samples. The proportion of methylcytosines sites in CpG was n = 32,682, the highest among all the sequence contexts (n = 3216 in CHH; n = 1743 in CHG). The majority of the methylcytosine occurred in the intron regions, followed by exon and promoter regions in CpG, CHH and CHG. Gene Ontology results indicated that DNAm affected genes that take place in cell differentiation and function in cutaneous, vascular and nervous systems. The identification of cellular response pathways allows a better understanding of the organism biological reaction to a specific environmental challenge and the development of sensitive tools based on the predictive responses. Eco-epigenetics analyses have an extraordinary potential to address growing issues on pollution biomonitoring, ecotoxicity assessment, conservation and management planning.

Mass spectrometry-based determination of lipids and small molecules composing adipose tissue with a focus on brown adipose tissue

Adipose tissue has been the subject of research for a very long time. Many studies perform a comprehensive analysis of different types of adipose tissue with an emphasis on brown adipose tissue. Mass spectrometry-based approaches are particularly useful in the exploration not only of the metabolic composition of adipose tissue but also its function. In the presented review, a complex and critical overview of publications devoted to the analysis of adipose tissue by means of mass spectrometry was performed. Detailed investigation of analytical aspects related to either untargeted or targeted analysis of adipose tissue was performed, leading to the formation of a collection of hints at the available analytical methods. Moreover, a profound analysis of the metabolic composition of brown adipose tissue was performed. Brown adipose tissue metabolome was characterized on structural and functional levels, providing information about its exact metabolic composition but also connecting these molecules and placing them into biochemical pathways. All our work resulted in a very broad picture of the analysis of adipose tissue, starting from the analytical aspects and finishing on the current knowledge about its composition.

Androstenedione and testosterone but not progesterone are potential biomarkers of pregnancy in Humpback Whales (Megaptera novaeangliae) approaching parturition

The blubber steroid hormone profiles of 52 female humpback whales migrating along the east coast of Australia were investigated for seasonal endocrine changes associated with reproduction. Individuals were randomly sampled during two stages of the annual migration: before reaching the breeding grounds (northward migration; June/July), and after departing from the breeding grounds (southward migration; September/October). Assignment of reproductive status of the sampled individuals was based on season, single-hormone ranks and multi-variate analysis of the hormonal profiles. High concentrations of progesterone (>19 ng/g, wet weight), recognised as an indicator of pregnancy in this species, were only detected in one sample. However, the androgens, testosterone and androstenedione were measured in unusually high concentrations (1.6-12 and 7.8-40 ng/g wet weight, respectively) in 36% of the females approaching the breeding grounds. The absence of a strong accompanying progesterone signal in these animals raises the possibility of progesterone withdrawal prior to parturition. As seen with other cetacean species, testosterone and androstenedione could be markers of near-term pregnancy in humpback whales. Confirmation of these androgens as alternate biomarkers of near-term pregnancy would carry implications for improved monitoring of the annual fecundity of humpback whales via non-lethal and minimally invasive methods.

Blubber steroid hormone profiles as indicators of physiological state in free-ranging common bottlenose dolphins (Tursiops truncatus)

Blubber has been proposed as a possible alternative to blood in the assessment of endocrine physiology in marine mammals because it can be collected via remote biopsy, which removes some of the confounding variables and logistical constraints associated with blood collection. To date, few studies have directly assessed the relationships between circulating versus blubber steroid hormone profiles in marine mammals, and these studies have been limited to a small subset of steroid hormones, which collectively limit the current utility of blubber steroid hormone measurements. In this study, we used liquid-chromatography tandem-mass spectrometry (LC-MS/MS) to screen for 16 steroid hormones in matched blood and blubber samples from free-ranging common bottlenose dolphins (Tursiops truncatus). Seven steroid hormones were detected and quantified, including two progestogens, two androgens, and three corticosteroids. Using principal components analysis (PCA), we explored relationships between hormones in both matrices and three physiological states: sexual maturity, pregnancy, and acute stress response. Plasma and blubber testosterone and its precursors, 17-hydroxyprogesterone and androstenedione, loaded to the first principal component (PC1), and PC1 scores were higher in mature males. Plasma and blubber progesterone loaded to PC2, and pregnant/probable pregnant females had significantly higher PC2 scores. Pregnant females also had higher PC1 scores than other females, suggesting differences in androgen profiles between these groups. There was disagreement between plasma and blubber corticosteroid profiles, as indicated by their loading to different PCs; plasma corticosteroids loaded to PC3 and blubber corticosteroids to PC4. PC3 scores were significantly predicted by elapsed time to blood collection (i.e., time between initiating the capture process and blood collection), while elapsed time to blubber collection significantly predicted PC4 scores, indicating that corticosteroid profiles shift in both tissues during acute stress. Corticosteroid profiles were not related to demographic group, site-month, body mass index, water temperature, or time spent outside of the water on the processing boat. Overall, these results demonstrate that blubber steroid hormone profiles reflect changes in endocrine function that occur over broad temporal scales.

Remote blubber sampling paired with liquid chromatography tandem mass spectrometry for steroidal endocrinology in free-ranging bottlenose dolphins (Tursiops truncatus)

Liquid chromatography tandem mass spectrometry allows for the measurement of steroid hormone suites in the blubber of marine mammals. By combining this technology with minimally invasive techniques such as remote biopsy, endocrine profiles can be assessed, allowing for studies of hormonal profile variation over time. In this study, we explored associations among different steroidogenic pathways and seasonal differences in blubber hormone profiles of free-ranging common bottlenose dolphins along the coast of South Carolina, USA. Male dolphins experience a peak in testosterone, androstenedione, progesterone, and 17-hydroxyprogesterone in the spring, likely related to an upregulation of the androgen steroidogenic pathway during mating season. We also observed increased cortisol concentrations during summer compared to winter. Among females, there was an increase in androstenedione with elevated progesterone concentrations indicative of pregnancy, highlighting another potential endocrine marker for pregnancy in free-ranging dolphins. This work emphasizes the importance of selecting the appropriate season for studies on endocrine status to effectively uncover physiological variation or disruption in free-ranging cetaceans.