The Organochlorine Insecticides - Organic Pollutants: An Ecotoxicological Perspective - page 108

1990, total DDT residues of <230 mg/kg were reported for this species (Kannan et al.
1993; O'Shea and Aguilar 2001), producing further evidence of the continuing high
level of pollution in this inland sea. In a study conducted in 1995, total DDT residues
(very largely p,p ′-DDE) were determined in marine organisms from the Barents Sea,
near Svalbard in the Arctic (Borga, Gabrielsen, and Skaare 2001). Again, marked
biomagnification was evident in residues, expressed as micrograms per gram in lipid
with movement up the food chain, as indicated in the following table. Whole samples
of fish and excised livers of birds were submitted for analysis.

Biomagnification factors
for total ddt
(cf. trophic levels 2/3)

trophic level organisms

2/3 Crustaceans 1

4 Cod ( Gadus morhua )

× 2

Guillemots ( Uria lomvia and Cepphus grylle ) × 47

Kittiwake ( Rissa tridactyla ) × 82

5 Glaucous gull ( Larus hyperboreus )

× 2300

Once again, fish-eating species—the two guillemots and the kittiwake—in trophic
level 4 show considerable biomagnification of residue in comparison with the inverte-
brates of levels 2 and 3. Most strikingly, though, the ultimate predator in trophic level
5, the glaucous gull, shows a biomagnification factor of 2300! It is suggested that
this may be related to the fact that these predators feed upon fauna associated with
ice. The mean value for total DDT levels in the livers of glaucous gulls, expressed as
micrograms per gram in lipid, was 42. In a later study of organochlorine residues in
arctic seabirds (Borga et al. 2007), p,p ′-DDE remained a dominant residue in birds
occupying positions in higher trophic levels, these species including little auk ( Alle
alle ) as well as the two species of guillemot and kittiwake mentioned here. The dif-
ferential biomagnification of organochlorine residues was examined in these species
and related to factors such as diet, habitat, and metabolic capacity.
Finally, an investigation of total DDT levels in seal ( Phoca sibirica ) from Lake
Baikal, Russia (the largest lake in the world), during the 1990s showed substantial
levels with evidence of strong biomagnification in this aquatic food chain (Lebedev
et al. 1998).
p,p ′-DDE can also undergo bioaccumulation in terrestrial food chains. Studies
with earthworms and slugs indicate that there can be a bioconcentration of total
DDT residues ( p,p ′-DDT + p,p ′-DDE + p,p ′-DDD) relative to soil levels of one- to
fourfold by earthworms, and above this by slugs (Bailey et al. 1974; Edwards 1973).
When DDT was still widely used in orchards in Britain, blackbirds ( Turdus merula)
and song thrushes ( Turdus philomelis ) that had been found dead contained very
high levels of DDT residues in comparison with those in the earthworms they ate.
Some results from a study on one orchard sprayed with DDT are given in Table 5.4.
Interpretation of field data involving such small numbers of individual specimens
needs to be done with caution. However, the principal source of DDT residues for
the two Turdus species appears to have been earthworms and other invertebrates
(including slugs and snails). The birds found dead were probably poisoned by DDT