442
behavior (Lutcavage et al. 1995). They are continuously exposed by resurfacing to
breathe (Milton et al. 2003), and pelagic juveniles are susceptible to floating tar
accumulations in ocean convergence zones due to indiscriminate feeding patterns
(Witherington 2002; Lutcavage et al. 1997).
In laboratory studies, juvenile loggerheads were adversely affected by short-term
exposures to oil in almost all aspects of physiology (e.g., respiration, diving patterns, energy metabolism, salt gland function, oxygen transport, blood chemistry,
and red and white blood cell count) (Lutcavage et al. 1995; Lutz et al. 1986). In sea
turtles, oil clings to eyes and nares and causes skin to slough off leaving inflamed
soft skin exposed to infection (Lutcavage et al. 1995). Skin lesions and necrosis
were observed in leatherback oil exposure studies, and skin returned to normal
appearance approximately 1 month after the turtles were removed from oil
(Lutcavage et al. 1995). Following the Ixtoc 1 oil spill, necropsied sea turtles were
found to have to ingested large amounts of oil, with indications that the ingestion
was eventually lethal (Hall et al. 1983). Effects of oil ingestion in loggerheads dying
from oil exposure in the Canary Islands include esophageal impaction, necrotizing
dermatitis and gastroenteritis, and necrotizing hepatitis (Camacho et al. 2013).
During the DWH spill, live oiled turtles admitted for rehabilitation exhibited
abnormalities including relatively severe metabolic and osmoregulatory derangements resulting from a combination of stress, exertion, exhaustion, and dehydration
related to oiling, capture and transport (Stacy et al. 2017). Mortalities were examined for evidence of internal exposure to polycyclic aromatic hydrocarbons (PAHs)
and dispersant component dioctyl sodium sulfosuccinate (DOSS) (Ylitalo et al.
2017). Visibly oiled turtles had higher concentrations of PAH than unoiled turtles,
which may suggest low-level exposure from other sources, and DOSS levels were
below the limit of quantitation in almost all samples (Ylitalo et al. 2017).
Transect searches conducted in convergence zones during rescue operations following the DWH spill documented 937 oceanic juvenile Kemp’s ridley, green, loggerhead, and hawksbill turtles in the spill area, and 81% of those captured were
visibly oiled (McDonald et al. 2017). Based on these observations, turtle density
calculations, and spatial extent of the oil, the total number of pelagic-stage sea turtles exposed to DWH oil was estimated at 402,000, with 54,800 of these heavily
oiled, although the majority of the dead turtles were believed to be unobserved and
therefore unaccounted for in these estimates (McDonald et al. 2017). Researchers
estimated an overall mortality of 30% for oceanic turtles within the footprint of the
spill in addition to those presumed dead from heavy oiling (Mitchelmore et al.
2017). Dependence on floating Sargassum for shelter and food in convergence
zones where oil and tar accumulate makes surface-pelagic turtles particularly vulnerable to ingesting oil and tar (Witherington 2002; Witherington et al. 2012).
Stranding data indicated that sea turtle stranding rates were at record levels in 2010
and 2011, increasing as much as 5× after the spill (NMFS data).
Kemp’s ridley’s principal foraging habitat is in the northern GOM (Seney and
Landry Jr 2008; Shaver et al. 2013). Stable isotope analyses conducted on nesting
Kemp’s showed that 51.5% of turtles sampled had evidence of oil exposure (Reich
et al. 2017), indicating that the primary foraging grounds in the northern GOM were
K. E. Frasier et al.
behavior (Lutcavage et al. 1995). They are continuously exposed by resurfacing to
breathe (Milton et al. 2003), and pelagic juveniles are susceptible to floating tar
accumulations in ocean convergence zones due to indiscriminate feeding patterns
(Witherington 2002; Lutcavage et al. 1997).
In laboratory studies, juvenile loggerheads were adversely affected by short-term
exposures to oil in almost all aspects of physiology (e.g., respiration, diving patterns, energy metabolism, salt gland function, oxygen transport, blood chemistry,
and red and white blood cell count) (Lutcavage et al. 1995; Lutz et al. 1986). In sea
turtles, oil clings to eyes and nares and causes skin to slough off leaving inflamed
soft skin exposed to infection (Lutcavage et al. 1995). Skin lesions and necrosis
were observed in leatherback oil exposure studies, and skin returned to normal
appearance approximately 1 month after the turtles were removed from oil
(Lutcavage et al. 1995). Following the Ixtoc 1 oil spill, necropsied sea turtles were
found to have to ingested large amounts of oil, with indications that the ingestion
was eventually lethal (Hall et al. 1983). Effects of oil ingestion in loggerheads dying
from oil exposure in the Canary Islands include esophageal impaction, necrotizing
dermatitis and gastroenteritis, and necrotizing hepatitis (Camacho et al. 2013).
During the DWH spill, live oiled turtles admitted for rehabilitation exhibited
abnormalities including relatively severe metabolic and osmoregulatory derangements resulting from a combination of stress, exertion, exhaustion, and dehydration
related to oiling, capture and transport (Stacy et al. 2017). Mortalities were examined for evidence of internal exposure to polycyclic aromatic hydrocarbons (PAHs)
and dispersant component dioctyl sodium sulfosuccinate (DOSS) (Ylitalo et al.
2017). Visibly oiled turtles had higher concentrations of PAH than unoiled turtles,
which may suggest low-level exposure from other sources, and DOSS levels were
below the limit of quantitation in almost all samples (Ylitalo et al. 2017).
Transect searches conducted in convergence zones during rescue operations following the DWH spill documented 937 oceanic juvenile Kemp’s ridley, green, loggerhead, and hawksbill turtles in the spill area, and 81% of those captured were
visibly oiled (McDonald et al. 2017). Based on these observations, turtle density
calculations, and spatial extent of the oil, the total number of pelagic-stage sea turtles exposed to DWH oil was estimated at 402,000, with 54,800 of these heavily
oiled, although the majority of the dead turtles were believed to be unobserved and
therefore unaccounted for in these estimates (McDonald et al. 2017). Researchers
estimated an overall mortality of 30% for oceanic turtles within the footprint of the
spill in addition to those presumed dead from heavy oiling (Mitchelmore et al.
2017). Dependence on floating Sargassum for shelter and food in convergence
zones where oil and tar accumulate makes surface-pelagic turtles particularly vulnerable to ingesting oil and tar (Witherington 2002; Witherington et al. 2012).
Stranding data indicated that sea turtle stranding rates were at record levels in 2010
and 2011, increasing as much as 5× after the spill (NMFS data).
Kemp’s ridley’s principal foraging habitat is in the northern GOM (Seney and
Landry Jr 2008; Shaver et al. 2013). Stable isotope analyses conducted on nesting
Kemp’s showed that 51.5% of turtles sampled had evidence of oil exposure (Reich
et al. 2017), indicating that the primary foraging grounds in the northern GOM were
K. E. Frasier et al.