Chemistry Reference
In-Depth Information
either
p,p
′-DDT or
p,p
′-DDD and underwent strong biomagnification with transfer
along food chains.
Studies on the marine ecosystem of the Farne Islands in 1962-1964 showed that
p,p
′-DDE reached concentrations over 1000-fold higher in fish-eating birds at the
top of the food chain than those present in macrophytes at the bottom of the food
chain (Figure 5.3). Fish-eating shag (
Phalocrocorax aristotelis)
contained residues
some 50-fold higher than those in its main prey species, the sand eel (
Ammodytes
lanceolatus
). The sand eel was evidently the principal source of
p,p
′-DDE for the
shag, so there had apparently been very efficient bioaccumulation over a consider-
able period (Robinson et al. 1967a). However, as explained in Chapter 4, it should
be borne in mind that the biomagnification of highly lipophilic chemicals along the
entire aquatic food chain is a consequence not only of bioaccumulation through the
different stages of the food chain, but also of bioconcentration of chemicals present
in ambient water. For example, aquatic invertebrates of lower trophic levels acquire
much of their residue burden of lipophilic compounds such as
p,p
′-DDE by direct
uptake from ambient water (see Chapter 4).
In a study of marine food chains in the Pacific Ocean during the 1980s, biocon-
centration factors of the order of 10,000-fold for total DDT residues (very largely
p,p
′-DDE) were reported when comparing levels in zooplankton with those in ambi-
ent water (Tanabe and Tatsukawa 1992). Striking levels of biomagnification were
evident in the higher levels of the food chain. Thus, in comparison with residues
in zooplankton, mycotophid (
Diaphus suborbitalis
) and squid (
Todarodes pacificus)
)
contained residues some tenfold greater, and striped dolphin (
Stenella coerolea alba
),
several 100-fold greater. Total DDT residues of <50 mg/kg wet weight of blubber were
reported for the striped dolphin. In a later study conducted in the Mediterranean in
HEOD
(dieldrin)
DDE
10.0
1.0
0.1
0.01
0.001
123
Trophic Levels
45
12345
fIgure 5.3
Organochlorine insecticides in the Farne Island ecosystem. From Walker et
al. (2000). Trophic levels: (1) serrated wrack, oar weed; (2) sea urchin, mussel, limpet; (3)
lobster, shore crab, herring, sand eel; (4) cod, whiting, shag, eider duck, herring gull; (5)
cormorant, gannet, grey seal.
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