Environmental Engineering Reference
In-Depth Information
Seawater
0.000 002
Sediment
0.005-0.16
Plant plankton
(= phytoplankton)
8
Marine mammals 160
Animal plankton
(= zooplankton)
10
Invertebrates
5-11
PCB concentration in milligrams per litre
or milligrams per kilogram of fat
Sea birds 110
Fishes
1-37
Figure 1.3 Biomagnification of contaminants up the food web (© Walther-Maria Scheid,
Berlin, Germany, for World Ocean Review 2010)
ocean far from any source of mercury. It is recommended that
people (particularly pregnant women and young children) not
eat a lot of these fish. Chlorinated pesticides, PCBs, and dioxin
also undergo biomagnification, but metals other than methyl-
mercury do not do so.
The sex of a fish may affect how much of a contaminant
it accumulates. Egg yolk is a fat-rich substance that can store
large quantities of organic contaminants, and some females
put large amounts of these fat-soluble chemicals into eggs,
reducing the levels in their bodies. This maternal transfer of
contaminants is found in egg-laying birds and reptiles as well
as fishes. While it is a good for the females to reduce their own
pollutant level, it certainly does not benefit the offspring to
start out their lives already loaded with toxic chemicals.
What is toxicity?
A toxic substance is one that harms living things at low
concentrations. (Almost anything can be harmful if there is
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