More than 2,000 common bottlenose dolphins (Tursiops truncatus) inhabit the Barataria Bay Estuarine System in Louisiana, USA, a highly productive estuary with variable salinity driven by natural and ...man-made processes. It was unclear whether dolphins that are long-term residents to specific areas within the basin move in response to fluctuations in salinity, which at times can decline to 0 parts per thousand in portions of the basin. In June 2017, we conducted health assessments and deployed satellite telemetry tags on dolphins in the northern portions of the Barataria Bay Estuarine System Stock area (9 females; 4 males). We analyzed their fine-scale movements relative to modeled salinity trends compared to dolphins tagged near the barrier islands (higher salinity environments) from 2011 to 2017 (37 females; 21 males). Even though we observed different movement patterns among individual dolphins, we found no evidence that tagged dolphins moved coincident with changes in salinity. One tagged dolphin spent at least 35 consecutive days, and 75 days in total, in salinity under 5 parts per thousand. Health assessments took place early in a seasonal period of decreased salinity. Nonetheless, we found an increased prevalence of skin lesions, as well as abnormalities in serum biochemical markers and urine:serum osmolality ratios for dolphins sampled in lower salinity areas. This study provides essential information on the likely behavioral responses of dolphins to changes in salinity (e.g., severe storms or from the proposed Mid-Barataria Sediment Diversion project) and on physiological markers to inform the timing and severity of impacts from low salinity exposure.
After the Deepwater Horizon (DWH) oil spill began in April 2010, studies were initiated on northern Gulf of Mexico common bottlenose dolphins (Tursiops truncatus) in Mississippi Sound (MSS) to ...determine density, abundance, and survival, during and after the oil spill, and to compare these results to previous research in this region. Seasonal boat-based photo-identification surveys (2010-2012) were conducted in a section of MSS to estimate dolphin density and survival, and satellite-linked telemetry (2013) was used to determine ranging patterns. Telemetry suggested two different ranging patterns in MSS: (1) inshore waters with seasonal movements into mid-MSS, and (2) around the barrier islands exclusively. Based upon these data, dolphin density was estimated in two strata (Inshore and Island) using a spatially-explicit robust-design capture-recapture model. Inshore and Island density varied between 0.77-1.61 dolphins km-2 (Formula: see text = 1.42, 95% CI: 1.28-1.53) and 3.32-5.74 dolphins km-2 (Formula: see text = 4.43, 95% CI: 2.70-5.63), respectively. The estimated annual survival rate for dolphins with distinctive fins was very low in the year following the spill, 0.73 (95% CI: 0.67-0.78), and consistent with the occurrence of a large scale cetacean unusual mortality event that was in part attributed to the DWH oil spill. Fluctuations in density were not as large or seasonally consistent as previously reported. Total abundance for MSS extrapolated from density results ranged from 4,610 in July 2011 to 3,046 in January 2012 (Formula: see text = 3,469, 95% CI: 3,113-3,725).
Following the 2010
Deepwater Horizon
disaster and subsequent unusual mortality event, adverse health impacts have been reported in bottlenose dolphins in Barataria Bay, LA including impaired stress ...response and reproductive, pulmonary, cardiac, and immune function. These conditions were primarily diagnosed through hands-on veterinary examinations and analysis of standard diagnostic panels. In human and veterinary medicine, gene expression profiling has been used to identify molecular mechanisms underlying toxic responses and disease states. Identification of molecular markers of exposure or disease may enable earlier detection of health effects or allow for health evaluation when the use of specialized methodologies is not feasible. To date this powerful tool has not been applied to augment the veterinary data collected concurrently during dolphin health assessments. This study examined transcriptomic profiles of blood from 76 dolphins sampled in health assessments during 2013–2018 in the waters near Barataria Bay, LA and Sarasota Bay, FL. Gene expression was analyzed in conjunction with the substantial suite of health data collected using principal component analysis, differential expression testing, over-representation analysis, and weighted gene co-expression network analysis. Broadly, transcript profiles of Barataria Bay dolphins indicated a shift in immune response, cytoskeletal alterations, and mitochondrial dysfunction, most pronounced in dolphins likely exposed to
Deepwater Horizon
oiling. While gene expression profiles in Barataria Bay dolphins were altered compared to Sarasota Bay for all years, profiles from 2013 exhibited the greatest alteration in gene expression. Differentially expressed transcripts included genes involved in immunity, inflammation, reproductive failure, and lung or cardiac dysfunction, all of which have been documented in dolphins from Barataria Bay following the
Deepwater Horizon
oil spill. The genes and pathways identified in this study may, with additional research and validation, prove useful as molecular markers of exposure or disease to assist wildlife veterinarians in evaluating the health of dolphins and other cetaceans.
The oil spill resulting from the explosion of the Deepwater Horizon drilling platform initiated immediate concern for marine wildlife, including common bottlenose dolphins in sensitive coastal ...habitats. To evaluate potential sublethal effects on dolphins, health assessments were conducted in Barataria Bay, Louisiana, an area that received heavy and prolonged oiling, and in a reference site, Sarasota Bay, Florida, where oil was not observed. Dolphins were temporarily captured, received a veterinary examination, and were then released. Dolphins sampled in Barataria Bay showed evidence of hypoadrenocorticism, consistent with adrenal toxicity as previously reported for laboratory mammals exposed to oil. Barataria Bay dolphins were 5 times more likely to have moderate–severe lung disease, generally characterized by significant alveolar interstitial syndrome, lung masses, and pulmonary consolidation. Of 29 dolphins evaluated from Barataria Bay, 48% were given a guarded or worse prognosis, and 17% were considered poor or grave, indicating that they were not expected to survive. Disease conditions in Barataria Bay dolphins were significantly greater in prevalence and severity than those in Sarasota Bay dolphins, as well as those previously reported in other wild dolphin populations. Many disease conditions observed in Barataria Bay dolphins are uncommon but consistent with petroleum hydrocarbon exposure and toxicity.
Odontocete cetaceans bioaccumulate high concentrations of endocrine disrupting persistent organic pollutants (POPs), including dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyltrichloroethylene ...(DDE), and dichlorodiphenyldichloroethane (DDD) – collectively DDTs – but few studies have explored DDTs-mediated endocrine disruption in cetaceans. Herein, we use remotely collected blubber biopsies from common bottlenose dolphins (Tursiops truncatus) inhabiting a site with high localized DDTs contamination to study the relationships between DDTs exposure and steroid hormone homeostasis in cetaceans. We quantified blubber steroid hormone concentrations by liquid chromatography-tandem mass spectrometry and blubber POP concentrations by gas chromatography-mass spectrometry. We detected six steroid hormones in blubber, including progesterone (P4), 17-hydroxyprogesterone (17OHP4), androstenedione (AE), testosterone (T), cortisol (F), and cortisone (E). Sampled dolphins (n = 62) exhibited exposure to DDT, DDE, DDD, chlordanes (CHLDs), mirex, dieldrin, hexachlorobenzene, polychlorinated biphenyls (PCBs), and brominated diphenyl ethers (BDEs). Using principal components analysis (PCA), we determined that blubber DDTs primarily loaded to the first principal component (PC1) explaining 81.6% of the total variance in POP exposure, while the remaining POPs primarily loaded to the PC2 (10.4% of variance). PC1 scores were negatively correlated with blubber T in males and blubber F in females, suggesting that exposure to DDTs impacted androgen and corticosteroid homeostasis. These conclusions were further supported by observed negative correlations between T and o,p’-DDE, o,p’-DDD, and p,p’-DDD in males sampled in the fall, and between F and the six individual DDTs and ∑6DDTs in females. Overall, these results suggest that POP-mediated endocrine disruption may have occurred in this stock of dolphins, which could negatively impact their health and fitness. However, this study relied on uncontrolled incidental exposures, making it impossible to establish a causal relationship between DDTs exposure and endocrine effects. Importantly, this study demonstrates that remotely collected blubber biopsies are a useful matrix for studying endocrine disruption in marine mammals.
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•First study of DDTs-mediated endocrine disruption in common bottlenose dolphins•Organochlorine pesticide exposure linked to disrupted testosterone and cortisol homeostasis•Remote blubber biopsies are useful for studying marine mammal endocrine disruption
Bottlenose dolphins in Florida, USA continue to be exposed to the banned pesticide DDT and may be exhibiting impaired endocrine (hormone) health as a result.
Inshore common bottlenose dolphins (Tursiops truncatus) are exposed to a broad spectrum of natural and anthropogenic stressors. In response to these stressors, the mammalian adrenal gland releases ...hormones such as cortisol and aldosterone to maintain physiological and biochemical homeostasis. Consequently, adrenal gland dysfunction results in disruption of hormone secretion and an inappropriate stress response. Our objective herein was to develop diagnostic reference intervals (RIs) for adrenal hormones commonly associated with the stress response (i.e., cortisol, aldosterone) that account for the influence of intrinsic (e.g., age, sex) and extrinsic (e.g., time) factors. Ultimately, these reference intervals will be used to gauge an individual's response to chase-capture stress and could indicate adrenal abnormalities. Linear mixed models (LMMs) were used to evaluate demographic and sampling factors contributing to differences in serum cortisol and aldosterone concentrations among bottlenose dolphins sampled in Sarasota Bay, Florida, USA (2000-2012). Serum cortisol concentrations were significantly associated with elapsed time from initial stimulation to sample collection (p<0.05), and RIs were constructed using nonparametric methods based on elapsed sampling time for dolphins sampled in less than 30 minutes following net deployment (95% RI: 0.91-4.21 µg/dL) and following biological sampling aboard a research vessel (95% RI: 2.32-6.68 µg/dL). To examine the applicability of the pre-sampling cortisol RI across multiple estuarine stocks, data from three additional southeast U.S. sites were compared, revealing that all of the dolphins sampled from the other sites (N = 34) had cortisol concentrations within the 95th percentile RI. Significant associations between serum concentrations of aldosterone and variables reported in previous studies (i.e., age, elapsed sampling time) were not observed in the current project (p<0.05). Also, approximately 16% of Sarasota Bay bottlenose dolphin aldosterone concentrations were below the assay's detection limit (11 pg/mL), thus hindering the ability to derive 95th percentile RIs. Serum aldosterone concentrations from animals sampled at the three additional sites were compared to the detection limit, and the proportion of animals with low aldosterone concentrations was not significantly different than an expected prevalence of 16%. Although this study relied upon long-term, free-ranging bottlenose dolphin health data from a single site, the objective RIs can be used for future evaluation of adrenal function among individuals sampled during capture-release health assessments.
Common bottlenose dolphins (Tursiops truncatus), including those impacted by the 2010 Deepwater Horizon (DWH) oil spill, inhabit the coastal and estuarine waters of the northern Gulf of Mexico (GoM). ...In response to the spill, dolphin health assessments conducted in Barataria Bay, Louisiana – a site that experienced heavy and prolonged oiling – uncovered a high prevalence of health abnormalities and individuals in poor body condition. Although the health effects observed were suggestive of petroleum toxicity, a lack of pre-spill information regarding dolphin health raises the possibility that other environmental factors may have contributed to the adverse health of dolphins in this oil-impacted area. To assess how exposure to other environmental pollutants may affect the health of northern GoM dolphin populations impacted by the DWH oil spill, a suite of 69 persistent organic pollutants (POPs), including PCBs, PBDEs and organochlorine pesticides, was determined in blood and a subset of blubber samples collected during health assessments of 145 bottlenose dolphins at three GoM sites: two oil impacted sites - Barataria Bay, LA (BB), and Mississippi Sound, MS (MS) and an unimpacted reference site - Sarasota Bay, FL (SB). Overall, levels of POPs at all three sites appeared comparable or lower than concentrations previously reported for coastal bottlenose dolphin populations outside of the northern GoM. POP levels measured in BB dolphins were also comparable or lower than those measured at the unimpacted reference site (SB) within the northern GoM. Additionally, the relationship between blubber and blood contaminant levels in a smaller subset of BB and SB suggests that BB animals were not experiencing elevated blood-contaminant concentrations as a result of their poor body condition. Cumulatively, these results suggest that background levels of POPs measured are unlikely to produce the health abnormalities previously reported for BB dolphins.
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•Health concerns were identified in dolphins after the Deepwater Horizon oil spill.•The role of POPs in the adverse health state of oil-impacted dolphins is unknown.•POPs were measured in dolphins at unoiled and oil-impacted Gulf of Mexico sites.•Dolphins at oiled sites had POP levels comparable to healthy dolphin populations.•POPs are unlikely contributing to the adverse health of dolphins at oiled sites.
Phthalates are endocrine-disrupting chemicals added to plastics, personal care products, cleaning solutions, and pesticides. Extensive use has led to its exposure to wildlife, including common ...bottlenose dolphins (Tursiops truncatus) from Sarasota Bay, Florida, USA; however, there are gaps in knowledge regarding whether sample timing or geographic location influence exposure. Dolphins were evaluated for temporal and spatial variability in urinary mono(2-ethylhexyl) phthalate (MEHP) detection (2010–2019). Significant fluctuations in detectable MEHP concentrations were found across the dataset. All samples from 2014 and 2015 (n = 12) had detectable MEHP concentrations; thus, data were classified into cohorts to explore the significance of prevalent MEHP detection (“Cohort 1” (n = 10; 2010–2013), “Cohort 2” (2014–2015), and “Cohort 3” (n = 29; 2016–2019)). Compared to Cohorts 1 and 3, Cohort 2 had higher detectable MEHP concentrations (Dunn’s; p = 0.0065 and p = 0.0012, respectively) and a greater proportion of detectable MEHP concentrations (pairwise comparisons using Benjamini–Hochberg adjustments: p = 0.0016 and p = 0.0059, respectively). MEHP detection also varied across spatial scales. Dolphins with detectable MEHP concentrations had ranges primarily within enclosed embayments, while dolphins with nondetectable MEHP concentrations extended into open waters, potentially indicating geographically linked exposure risk. This study suggests that researchers and management agencies should consider a population’s ranging pattern, geographic habitat characteristics, and sample timing when assessing small cetacean health in relation to contaminant exposure.
Skin disease occurs frequently in many cetacean species across the globe; methods to categorize lesions have relied on photo-identification (photo-id), stranding, and by-catch data. The current study ...used photo-id data from four sampling months during 2009 to estimate skin lesion prevalence and type occurring on bottlenose dolphins (Tursiops truncatus) from three sites along the southeast United States coast Sarasota Bay, FL (SSB); near Brunswick and Sapelo Island, GA (BSG); and near Charleston, SC (CHS). The prevalence of lesions was highest among BSG dolphins (P = 0.587) and lowest in SSB (P = 0.380), and the overall prevalence was significantly different among all sites (p<0.0167). Logistic regression modeling revealed a significant reduction in the odds of lesion occurrence for increasing water temperatures (OR = 0.92; 95%CI:0.906-0.938) and a significantly increased odds of lesion occurrence for BSG dolphins (OR = 1.39; 95%CI:1.203-1.614). Approximately one-third of the lesioned dolphins from each site presented with multiple types, and population differences in lesion type occurrence were observed (p<0.05). Lesions on stranded dolphins were sampled to determine the etiology of different lesion types, which included three visually distinct samples positive for herpesvirus. Although generally considered non-fatal, skin disease may be indicative of animal health or exposure to anthropogenic or environmental threats, and photo-id data provide an efficient and cost-effective approach to document the occurrence of skin lesions in free-ranging populations.
Passive acoustics has been used extensively to study bottlenose dolphins; yet very few studies have examined the spatial, temporal, and environmental influences on vocalization types (echolocation, ...burst pulse sounds, and whistles), and few are long‐term and provide high temporal resolution over multiple years. We used data from 2013 to 2018 to establish baseline acoustic patterns for bottlenose dolphins in the May River estuary, South Carolina. We deployed acoustic recorders at six stations during 2013–2014 and three stations during 2015–2018, with locations spanning the entire estuary (headwaters to the mouth). We discovered that acoustic detection of dolphins varied not only spatially, but also yearly, monthly, and tidally. Higher numbers of echolocation bouts, burst pulse sounds, and whistles were detected at the mouth as compared to the headwaters. At the mouth, vocalization detections were greatest in fall and winter for multiple years, and echolocation detection was greatest during falling and low tides. This study provides an example of another tool, long‐term passive acoustics monitoring, to better understand spatial and temporal distribution of dolphins in a typical salt marsh estuary, that can be applied to other ecosystems throughout the southeastern United States and globally.
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