“…It was the largest marine oil spill in United States history and at its maximum extent covered an area of 40,000 km 2 which impacted vast swathes of oceanic, coastal, and estuarine waters from the Texas-Louisiana border to the central Florida Panhandle [ 1 – 4 ]. Studies were initiated to assess the impacts of the DWH oil spill on a wide range of plant and animal species, including cetaceans, as part of a Natural Resources Damage Assessment (NRDA) under the Oil Pollution Act of 1990 [ 3 , 5 ]. Cetaceans in the northern GoM inhabit oceanic (>200 m deep; 20 species), outer continental shelf (20–200 m deep; 2–3 species), and coastal (0–20 m deep; 1 species) waters as well as bays, sounds, and estuaries (BSEs; 1 species) [ 6 ].…”
Section: Introductionmentioning
confidence: 99%
“…Cetaceans in the northern GoM inhabit oceanic (>200 m deep; 20 species), outer continental shelf (20–200 m deep; 2–3 species), and coastal (0–20 m deep; 1 species) waters as well as bays, sounds, and estuaries (BSEs; 1 species) [ 6 ]. In many of these habitats, including BSE waters, cetaceans encountered DWH oil and potentially inhaled, directly aspirated, or ingested the oil or its toxic components [ 5 , 7 ].…”
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 ( = 1.42, 95% CI: 1.28–1.53) and 3.32–5.74 dolphins km−2 ( = 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 ( = 3,469, 95% CI: 3,113–3,725).
“…It was the largest marine oil spill in United States history and at its maximum extent covered an area of 40,000 km 2 which impacted vast swathes of oceanic, coastal, and estuarine waters from the Texas-Louisiana border to the central Florida Panhandle [ 1 – 4 ]. Studies were initiated to assess the impacts of the DWH oil spill on a wide range of plant and animal species, including cetaceans, as part of a Natural Resources Damage Assessment (NRDA) under the Oil Pollution Act of 1990 [ 3 , 5 ]. Cetaceans in the northern GoM inhabit oceanic (>200 m deep; 20 species), outer continental shelf (20–200 m deep; 2–3 species), and coastal (0–20 m deep; 1 species) waters as well as bays, sounds, and estuaries (BSEs; 1 species) [ 6 ].…”
Section: Introductionmentioning
confidence: 99%
“…Cetaceans in the northern GoM inhabit oceanic (>200 m deep; 20 species), outer continental shelf (20–200 m deep; 2–3 species), and coastal (0–20 m deep; 1 species) waters as well as bays, sounds, and estuaries (BSEs; 1 species) [ 6 ]. In many of these habitats, including BSE waters, cetaceans encountered DWH oil and potentially inhaled, directly aspirated, or ingested the oil or its toxic components [ 5 , 7 ].…”
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 ( = 1.42, 95% CI: 1.28–1.53) and 3.32–5.74 dolphins km−2 ( = 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 ( = 3,469, 95% CI: 3,113–3,725).
“…In 2010, the largest marine oil spill in the history of the U.S., the Deepwater Horizon oil spill (DWH), occurred in the northern Gulf of Mexico (GoM). Subsequently a multidisciplinary approach for evaluating the impacts upon cetaceans was undertaken (71,72). Bottlenose dolphins were the focal cetacean species examined due to the accessibility of dolphins in shallow coastal and estuarine waters, and the heavy oiling in some of those same nearshore areas.…”
Section: Petroleum Toxicitymentioning
confidence: 99%
“…Determining a causal link for the multiple pathologies observed post DWH oil exposure has been via a diagnosis of exclusion; concluding the toxic effects of the oil spill as the primary differential to both the observed pathologies and the increased dolphin mortality (71,75). Other differential diagnoses that were the potential causes of previous GoM UMEs were also ruled out including biotoxins (79), POPs (68), and infectious disease (45,73,80,81).…”
Section: Petroleum Toxicitymentioning
confidence: 99%
“…Utilizing a multidisciplinary approach to combine clinical veterinary knowledge with epidemiological analyses and population modeling enables long-term forecasting of population trajectories (36). In UMEs, modeling to estimate mortality based on the number of stranded carcasses can provide insight into the immediate losses to the population (71,(123)(124)(125). However, integration of available health information and veterinary interpretation of sublethal, chronic conditions, which are likely to influence long-term survival and reproductive potential, can provide a more accurate interpretation of the likely long-term impacts on the population (36).…”
Section: Multidisciplinary Approaches For Assessing Population Healthmentioning
The common bottlenose dolphin (Tursiops truncatus) is a global marine mammal species for which some populations, due to their coastal accessibility, have been monitored diligently by scientists for decades. Health assessment examinations have developed a comprehensive knowledge base of dolphin biology, population structure, and environmental or anthropogenic stressors affecting their dynamics. Bottlenose dolphin health assessments initially started as stock assessments prior to acquisition. Over the last four decades, health assessments have evolved into essential conservation management tools of free-ranging dolphin populations. Baseline data enable comparison of stressors between geographic locations and associated changes in individual and population health status. In addition, long-term monitoring provides opportunities for insights into population shifts over time, with retrospective application of novel diagnostic tests on archived samples. Expanding scientific knowledge enables effective long-term conservation management strategies by facilitating informed decision making and improving social understanding of the anthropogenic effects. The ability to use bottlenose dolphins as a model for studying marine mammal health has been pivotal in our understanding of anthropogenic effects on multiple marine mammal species. Future studies aim to build on current knowledge to influence management decisions and species conservation. This paper reviews the historical approaches to dolphin health assessments, present day achievements, and development of future conservation goals.
Population structure of highly mobile marine organisms can be complex and difficult to study, but it is important to understand how populations partition themselves within their environment for accurate assessment of both natural and anthropogenic impacts and successful management. The 2010 Deepwater Horizon oil spill negatively impacted common bottlenose dolphins (Tursiops truncatus) within Mississippi Sound and the surrounding north central Gulf of Mexico (GOMx); however, little was known about their underlying population structure in these waters. Thus, it was unclear how many demographically independent populations were affected by the spill.
Common bottlenose dolphin samples were collected throughout inshore waters of Mississippi Sound and coastal waters of the north‐central GOMx. Mitochondrial DNA control region sequence data and 19 nuclear microsatellite loci were analysed to determine how many populations are present and characterize their range throughout these waters.
Bayesian clustering and migration analyses identified two genetically distinct and demographically independent populations: one predominantly inhabiting Mississippi Sound and adjacent coastal waters, and a second population extending generally from offshore of Mobile Bay, Alabama, east along the Florida Panhandle. Neither of these populations align with the currently delineated management stocks previously used to estimate impacts from the oil spill on common bottlenose dolphins in this portion of the GOMx.
These results suggest that revisions may be necessary so that management stocks accurately represent the demographically independent populations present in these waters. Furthermore, better comprehension of underlying population structure will enhance impact assessments on common bottlenose dolphins and provide more appropriate baseline data to support future restoration and conservation objectives.
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