Environmental Engineering Reference
In-Depth Information
Studies in other species soon identifi ed eggshell thinning as the primary lesion
causing hatching failure. DDE was shown to cause eggshell thinning in numerous
declining species, including the osprey. Anderson and Hickey (
1972
) reported 21%
shell thinning in osprey eggs collected in Connecticut, New Jersey and Maryland
in 1957.
Johnson et al. (
1975
) reported 17% shell thinning in osprey eggs taken in Idaho
in 1972 and 1973. Total DDT in eggs averaged 10.3 ppm. Hatching success was
impaired. No fi sh residue measures were made. The general lack of use of DDT in
the nesting grounds led the authors to suggest that exposure to DDT had occurred
primarily during migration or at wintering grounds in Central America.
By 1973, fi sh residues, egg residues, eggshell thinning and hatching success
appeared to be the critical determinants of the effect produced by DDE on osprey
reproduction. All four parameters are highly correlated in declining species with
exposures suffi cient to cause eggshell thinning in excess of 10%. Mechanistic studies
suggested that DDE acts directly on the transport, formation and/or deposition of
calcium carbonate in the shell gland (e.g., see Risebrough et al.
1969
).
Wiemeyer et al. (
1975
) evaluated known factors impacting reproduction in East
Coast ospreys. The study period was 1968-1969. An egg exchange between nests in
Maryland and Connecticut revealed that Connecticut eggs had lower hatching success
than Maryland eggs, whether they remained in Connecticut or were moved to nests in
Maryland. In contrast, Maryland eggs had higher hatching success than Connecticut
eggs, whether they remained in Maryland or were moved to nests in Connecticut.
The problem appeared to be the egg and not the parents or the setting. This fi nding is
consistent with the direct effect that DDE has on the shell gland to produce thinner
shelled eggs that were more susceptible to breakage, and therefore lower hatching
success. DDE levels were higher in the fi sh diet of the osprey in some breeding areas
than others, explaining the differential productivity along the East Coast.
Fish collected in Connecticut waters contained an average total DDT residue of
2.0 ppm. Fish collected in Maryland averaged 0.2 ppm total DDT. Fish scraps from
osprey nests in Connecticut averaged 1.0 ppm, whereas one eel scrap from a nest in
Maryland had 0.1 ppm total DDT. Fish scraps were judged to be very slightly dehy-
drated. Henderson et al. (
1971
) reported total DDT residues for 1969 in fi sh of
0.68 ppm for the Susquehanna River and 0.60 for the Potomac River. Both rivers fl ow
into the Chesapeake Bay. Sampling locations on both rivers were in Maryland.
Total DDT in Connecticut osprey eggs collected in 1968-1969 was 10.3 ppm.
This residue level compares with 10.9 ppm in 1964. Egg residues of total DDT from
Maryland averaged 3.1 ppm. Eggshell thinning averaged 15% in Connecticut eggs
and 12% in Maryland eggs. Only two eggs hatched out of 25 eggs studied in
Connecticut. Fifteen eggs hatched out of 38 eggs studied in Maryland. Dieldrin may
have contributed to hatching failure in Connecticut. Lethal concentrations of dieldrin
were measured in a dead adult osprey found near the Connecticut River in 1967.
Crude estimates of biomagnifi cation from fi sh to egg were 10.9/(2.0 or 1.0) = 5.4-10.9
for Connecticut and 3.1/(0.68-0.1) = 4.6-31 for Maryland.
In a 1972 study done on an offshore island along the Gulf coast of Florida, Szaro
(
1978
) reported an average of 0.11 ppm total DDT in fi sh (lipid basis converted to
fresh weight assuming 5% lipid), an average of only 0.43 ppm total DDT in eggs, a 9%
Search WWH ::
Custom Search