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The Biology of Sea Turtles, Vol. II
immunosuppressant. PCB immunosuppression results in higher sensitivities of
experimental animals to a wide variety of infectious agents, including bacteria
(endotoxin), protozoa, and viruses (De Guise et al., 1998). Lahvis et al. (1995)
found a direct correlation between suppressed immunological function in vitro and
PCB load in bottlenose dolphins, whereas the PCB-linked impairment of immune
function likely contributed to the recent mass mortalities in European harbor seals
resulting from morbillivirus infections (Ross, 2000).
Similar patterns of accumulation, if not actual concentrations, are possible in
some sea turtle species when compared to marine mammals because similar diets
can lead to similar tissue lipid compositions (Guitart et al., 1999). In sea turtles,
fibropapilloma is more prevalent in green turtles captured near densely populated,
industrial regions than in animals from sparsely populated areas (Adnyana et al.,
1997), although no correlation was detected between organochlorine, PCB, or organophosphate levels and green turtle fibropapilloma disease (GTFP) (Aguirre et al.,
1994). However, the potential for chronic pollutants to decrease immune function
either directly or indirectly (by increasing overall stress) could have significant
impacts on sea turtle populations, because how they deal with physical stress (infection or trauma) is affected by environmental stress, and stress in general most likely
depresses the turtle immune system (George, 1997).
In general, chronic illnesses, mass mortalities, and epidemics are being reported
across a wide spectrum of taxonomic groups in increasing numbers, with novel
occurrences of pathogens, invasive species, and illnesses affecting wildlife globally.
Such disturbances impact multiple components of marine ecosystems, disrupt both
functional and structural relationships between species, and affect the ability of
ecosystems to recover from natural or anthropogenic perturbations (Sherman, 2000).
6.3.2.2.2 Endocrine Disruption
Hormone disrupters are insidious but high-impact disturbers of population fitness.
It is now well established that some organopesticides released into the environment
act as endocrine-disrupting contaminants, functioning as hormone agonists or antagonists to disrupt hormone synthesis, action, and/or metabolism. Laboratory studies
provide strong evidence of organopesticides’ causing endocrine disruption at environmentally realistic exposure levels (Vos et al., 2000). In the aquatic environment,
effects have been observed in mammals, birds, reptiles, fish, and mollusks. Alligators
living in environments contaminated with endocrine disrupters, for example, have
suffered population declines because of the developmental and endocrine abnormalities effected by these contaminants on eggs, juveniles, and adults (Guillette, 2000).
Endocrine-disrupting contaminants have also adversely affected a variety of fish
species in freshwater systems, estuaries, and coastal areas, whereas marine invertebrates (snails and whelks) have suffered population declines in some areas because
of the masculinization of females (Vos et al., 2000).
PCBs, which are widespread, low-level environmental contaminants, are
strongly implicated as endocrine disrupters. There is evidence that PCBs are capable
of disrupting reproductive and endocrine function in a variety of taxonomic groups,
in addition to producing other adverse health effects such as immune suppression
and teratogenicity. Bergeron et al. (1994) demonstrated that the estrogenic effect of
1123 book.book Page 172 Monday, November 11, 2002 11:11 AM
The Biology of Sea Turtles, Vol. II
immunosuppressant. PCB immunosuppression results in higher sensitivities of
experimental animals to a wide variety of infectious agents, including bacteria
(endotoxin), protozoa, and viruses (De Guise et al., 1998). Lahvis et al. (1995)
found a direct correlation between suppressed immunological function in vitro and
PCB load in bottlenose dolphins, whereas the PCB-linked impairment of immune
function likely contributed to the recent mass mortalities in European harbor seals
resulting from morbillivirus infections (Ross, 2000).
Similar patterns of accumulation, if not actual concentrations, are possible in
some sea turtle species when compared to marine mammals because similar diets
can lead to similar tissue lipid compositions (Guitart et al., 1999). In sea turtles,
fibropapilloma is more prevalent in green turtles captured near densely populated,
industrial regions than in animals from sparsely populated areas (Adnyana et al.,
1997), although no correlation was detected between organochlorine, PCB, or organophosphate levels and green turtle fibropapilloma disease (GTFP) (Aguirre et al.,
1994). However, the potential for chronic pollutants to decrease immune function
either directly or indirectly (by increasing overall stress) could have significant
impacts on sea turtle populations, because how they deal with physical stress (infection or trauma) is affected by environmental stress, and stress in general most likely
depresses the turtle immune system (George, 1997).
In general, chronic illnesses, mass mortalities, and epidemics are being reported
across a wide spectrum of taxonomic groups in increasing numbers, with novel
occurrences of pathogens, invasive species, and illnesses affecting wildlife globally.
Such disturbances impact multiple components of marine ecosystems, disrupt both
functional and structural relationships between species, and affect the ability of
ecosystems to recover from natural or anthropogenic perturbations (Sherman, 2000).
6.3.2.2.2 Endocrine Disruption
Hormone disrupters are insidious but high-impact disturbers of population fitness.
It is now well established that some organopesticides released into the environment
act as endocrine-disrupting contaminants, functioning as hormone agonists or antagonists to disrupt hormone synthesis, action, and/or metabolism. Laboratory studies
provide strong evidence of organopesticides’ causing endocrine disruption at environmentally realistic exposure levels (Vos et al., 2000). In the aquatic environment,
effects have been observed in mammals, birds, reptiles, fish, and mollusks. Alligators
living in environments contaminated with endocrine disrupters, for example, have
suffered population declines because of the developmental and endocrine abnormalities effected by these contaminants on eggs, juveniles, and adults (Guillette, 2000).
Endocrine-disrupting contaminants have also adversely affected a variety of fish
species in freshwater systems, estuaries, and coastal areas, whereas marine invertebrates (snails and whelks) have suffered population declines in some areas because
of the masculinization of females (Vos et al., 2000).
PCBs, which are widespread, low-level environmental contaminants, are
strongly implicated as endocrine disrupters. There is evidence that PCBs are capable
of disrupting reproductive and endocrine function in a variety of taxonomic groups,
in addition to producing other adverse health effects such as immune suppression
and teratogenicity. Bergeron et al. (1994) demonstrated that the estrogenic effect of
1123 book.book Page 172 Monday, November 11, 2002 11:11 AM