Environmental Engineering Reference
In-Depth Information
Figure 4.9
The impact of
acid rain on aquatic
organisms
Source:
Compiled from data
in Israelson (1987); Baker
and Schofield (1985);
LaBastille (1981); Ontario:
Ministry of the Environment
(1980)
(Mason 1990). Aluminium also kills a variety of
invertebrates, but the progressive concentration
of the metal through food chains and food webs
ensures that higher level organisms such as fish
are particularly vulnerable, and it is possible that
fish kills previously attributed to high acidity
were, in fact, the result of aluminium poisoning
(Park 1987). The mobilization of heavy metals
by leaching may also help to reduce fish
populations indirectly by killing the insects and
microscopic aquatic organisms on which the fish
feed. Birds such as herons, ospreys and
kingfishers, which feed on the fish, and those such
as ducks and other waterfowl, which depend
upon molluscs and aquatic insects for their food,
also feel the effects of this disruption of the food
chain (Howard and Perley 1991).
The fish are particularly vulnerable during the
annual spring flush of highly acidic water into
the lakes and streams. This is a well-documented
phenomenon which causes stress to all organisms
in the aquatic environment (Park 1987). All of
the areas presently affected by acid rain receive
a proportion of their total precipitation in the
form of snow. The acids falling in the snow during
the winter accumulate on land and on the frozen
