Reconnaissance of 17ß -Estradiol, 11-Ketotestosterone, Vitellogenin,
and Gonad Histopathology in Common Carp of United States Streams:
Potential for Contaminant-Induced Endocrine Disruption
By Steven L. Goodbred, Robert J. Gilliom, Timothy S. Gross, Nancy P. Denslow,
Wade L. Bryant, and Trenton R. Schoeb
U.S. Geological Survey Open-File Report 96-627
SUMMARY
Reconnaissance assessment of sex steroid hormones in carp from United States
streams indicates that fish in some streams within all regions studied may be
experiencing some degree of endocrine disruption. Primary lines of evidence
for the occurrence of endocrine disruption are the significant site-to-site
differences in biomarkers within regions and the presence of significant
correlations between bio-markers and contaminants. Gonad histopathology,
however, showed that only one fish out of 438 had an abnormality that
could be associated with sex-steroid hormone levels. Specific findings are
summarized below:
- For 23 streams and 2 impoundments studied in five major regions of the
United States, mean levels of 17ß-estradiol and 11-ketotestosterone in
common carp spanned 2 orders of magnitude for each sex during recrudescence.
- There were no significant (a=0.05) differences between regions in sex
steroid hormones for males, but females from the Northern Midcontinent and
the Southern Midcontinent were significantly different from other regions in
one or both hormones.
- Within most regions, there were significant differences between sites in
one or both sex steroid hormones for both sexes.
- The ratio of 17ß-estradiol to 11-ketotestosterone
(E22/11-KT) also had significant differences between sites in most
regions for both male and female carp.
- Vitellogenin showed some differences between sites for females in the
Northeast, the Mississippi River Basin, and the West.
- The gonad conditions of most males and females were similar for all sites
and regions, indicated similar stages of sexual maturation, and showed only one
abnormality in 438 fish.
- Total organochlorine pesticides and PCBs in tissues (lipid normalized) and
phenols, PAHs, and phthalates in bed sediment (organic carbon normalized) each
spanned at least two orders of magnitude among sites. Mean total dissolved
pesticides in water varied within a factor of 10. There were significant
correlations between PCBs and organochlorine pesticides, PCBs and PAHs, PAHs
and phthalates, and phthalates and phenols.
- Of 15 correlations between biomarkers and contaminants that had p values
less than 0.25 (males and females), 14 were negative.
- For male carp: (1) 17ß-estradiol had a significant (a=0.05) negative
correlation with total organochlorine pesticides; (2) 11-ketotestosterone had a
significant negative correlation with phenols; and (3) E22/11-KT
ratio had a significant negative correlation with total dissolved pesticides.
- For female carp: (1) 11-ketotestosterone had a significant positive
correlation with dissolved pesticides; and (2) E2/11-KT ratio had a
significant negative correlation with dissolved pesticides.
- The strongest patterns common to both males and females are: (1) negative
correlations between the E2/11-KT ratio and dissolved pesticides,
and (2) negative correlations between phenols and both 17ß-estradiol
and 11-ketotestosterone.
- Notable differences between males and females are: (1) the significant
negative correlation between 17ß-estradiol and organochlorine pesticides
shown in males and not in females, and (2) the significant positive correlation
between 11-ketotestosterone and dissolved pesticides shown in females and not
in males.
More information is needed in several areas to evaluate whether endocrine
disruption is actually occurring in fish of some streams, what may be its
cause, and whether there are biological effects on individuals or populations.
A distinct shift in study design will be required from the "one sample from
many sites" approach of the reconnaissance, to the "intensive study of a few
sites" approach for more detailed study. A paired site approach is suggested
for further investigation, with one "contaminated" site and one "reference site"
located in the regions with the clearest evidence of endocrine disruption.
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