Environmental Engineering Reference
In-Depth Information
2. The extremely high
DDT concentrations reported in the 1970s may have been
associated with reproductive problems in California Sea Lions.
3. The decline in
ʣ
DDT residues in California sea lions was so dramatic because
their breeding area in southern California was much less contaminated with
DDT residues than in 1970.
ʣ
However, O'Shea and Brownell (
1996
) took issue with the latter statement,
which they considered to be based primarily upon circumstantial evidence. For
instance, they suggested that the original sample sizes (7 and 12) were too limited
to draw such sweeping conclusions. In addition, they noted a paucity of experimen-
tal evidence demonstrating an impact of DDT and/or it metabolites on sea lion
reproduction. In addition, O'Shea and Brownell (
1996
) noted that California sea
lion populations have historically fl uctuated, declining in the late 1800s and early
1900s, and increasing in the 1960s. Therefore, while they do not necessarily dis-
count the observations of Lieberg-Clark et al. (
1995
), their overall contention was
that to-date there was insuffi cient evidence to draw such conclusions.
In
1997
, Hayteas and Duffi eld reported the
p
,
p
-DDE concentrations from the
blubber of some fi ve California sea lions (in addition to harbor seals, above) col-
lected off the Oregon coast to have a geometric mean of 8.1 ppm (range,
3.2-15.4 ppm);
p
,
p
′
-DDT levels were again not reported as they were negligible in
all samples. They again concluded that animals with higher residue levels may have
migrated from California. In addition, and most importantly, their p,p
′
-DDE value
was in the same range as that of the Lieberg-Clark et al. (
1995
) study, providing
further confi rmation of the dramatic decline in residues reported by them.
More recently, Kajiwara et al. (
2001
) reported the concentrations of organochlo-
rine insecticides (based on lipid weight) in some 15 stranded California sea lions
collected between 1991 and 1997; in blubber, the geometric mean DDT concentra-
tion was 209 ppm (range, 13-2,900 ppm), while in liver it averaged 142 ppm (range,
12-970 ppm). Their results contrasted with those of Lieberg-Clark et al. (
1995
) for
animals collected during an overlapping time period; however, the Lieberg-Clark
et al. (
1995
) data were reported on a wet sample weight basis.
Connolly and Glaser (
2002
) reported the accumulation of
p
,
p
′
-DDE in female
California sea lions resident to the California Channel Islands. High concentrations
of DDT and its degradation products emanating from the Whites Point outfall con-
taminated the sediments and aquatic life of the Palos Verdes shelf and Santa Monica
Bay. Fish contaminated by these DDT wastes were suspected of serving as vectors
in transferring residues to the sea lion population. However, they determined that
p
,
p
′
-DDE residues in the blubber of female premature parturient sea lions from San
Miguel Island declined from a mean of 944 ppm in 1970 to 40 in 1991, while those
from full-term parturient females also declined during the same time period (from
109 to 10 ppm). Both declines, approximately a full order of magnitude, were simi-
lar to that reported by Lieberg-Clark et al. (
1995
) and mirror the declines observed
in sediments and mussels. In addition, Connolly and Glaser (
2002
) noted that
reduced concentrations in full-term parturient females were most likely infl uenced
by lactation.
′
Search WWH ::
Custom Search