Environmental Engineering Reference
In-Depth Information
PCBs, pesticides, and other chemicals. The reactions have two
steps. Phase I reactions hydrolyze or oxidize the molecule in
order to make it more water soluble. Phase II reactions involve
combining the product of phase I with a substance that makes
it less bioactive and more readily excreted. Sometimes, prod-
ucts of phase I are more toxic than the original pollutant.
Highly chlorinated compounds are metabolized very
slowly, so they tend to accumulate. Lesser chlorinated com-
pounds can be more rapidly metabolized and eliminated.
Organophosphorus pesticides can also be oxidized by the
MFO system.
Which marine organisms are good sentinels for
bioaccumulation and biomagnification of chemicals?
Sedentary bivalve mollusks like mussels are often used for
monitoring pollutants in local areas. They tend to be relatively
low on the food web and not accumulate very high levels. In
the oceans, mammals such as seals and cetaceans are useful
sentinels for pollution. Their blubber accumulates high levels
and can be sampled without harming the animal. Seabirds
are also useful, and can be cheaper and easier to sample. They
range widely across oceans, feeding as they move, but return
every year to breed in the same location. In a seabird colony
biologists can sample blood, feathers, oils, and biopsies, which
can provide information on pollution at different spatial and
time scales. Bird eggs, rich in lipids (fats), are excellent accu-
mulators of fat-soluble chlorinated organic chemicals that
are of most concern. Birds with different feeding habits can
be sampled—for example, cormorants that forage mainly on
fish in near-shore environments, auks that feed on smaller
fish and zooplankton on the continental shelf, and pelagic
seabirds such as storm petrels that range offshore, feeding on
zooplankton and larval fishes. They all return to breed in colo-
nies, where they can be sampled for contaminants and tagged
for tracking. Seabird egg monitoring documented the decline
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