Geography Reference
In-Depth Information
Table 3.2
Emissions of nitrous gases for selected countries.
undertaken as part of two major initiatives: the
Palaeoecological Investigation of Recent Lake
Acidification (PIRLA) in Canada and the USA;
and the Surface Waters Acidification Programme
(SWAP) in the UK, Norway and Sweden. The
results from these projects have revealed the degree
and timing of anthropogenic acidification and
have shown it to be a serious and widespread
problem.
Much of the PIRLA and SWAP research
exploits the sensitivity of species of diatoms
(unicellular algae that are the basis of food chains
in many freshwater and marine environments) to
pH and their widespread occurrence in lake
sediments. The pH tolerances of the species
recovered as fossils from lake sediments are known
from studies of their living equivalents; thus the
construction of lake acidification histories is
possible based on diatom-inferred pH
reconstructions. Acidification has not only
influenced primary producers such as the diatoms
but has also affected the species composition of
other organisms at all trophic levels. The remains
of some of these organisms, such as cladocera
(microscopic animals occurring in fresh water) and
chrysophytes (planktonic algae with an outer
