Environmental Engineering Reference
In-Depth Information
Figure 8.3.
The red waters of Psyche Bend Lagoon attest to the impact of recent (2004)
acidification of the lagoon following its sacrifice in a broader management programme
(Photo: Peter Gell).
See colour plate section
.
several months in 2004. Return water from intensive irrigation agriculture
had carried sulphate salts to the wetland which were stored in the lake's
sediments. Regulation, again to ensure supply for irrigators, ensured perman-
ency of a seasonally inundated wetland reducing the sulphate-rich sediments
to a sulphidic state. Exposure to oxygen through 2004 released sulphuric acid
and iron, and presumably aluminium, from the sediments into the shallow
waters releasing an iron-red stain (
Fig. 8.3
). The remnant native fish popula-
tions were lost. This slide to ecological collapse was readily observable through
wetland recent monitoring as noted above (Gell et al.
2002
). Other sites, not
quite so well-monitored, have also become acid through the same process.
The preliminary, coarse resolution record from Martin's Bend Lagoon (
Fig. 8.4
),
discovered to be acid during sediment coring, shows that the recent acid
condition is indeed unprecedented. The acidophilous diatom taxa in the genus
Pinnularia are confined to the uppermost sediments and are not found in other
records across the region.
Synthesis
Multiple drivers and symptoms
Lowland systems aggregate the sediments, nutrients, metals and salts derived
from the impact of humans on landscapes up-catchment as well as those
derived nearby. Catchment disturbance enables the more rapid release of
