Abstract:
Concentrations of total Aluminium (Al) and Iron (Fe) were determined in Lake
Loskop over a period of four month in 2009 in samples of phytobenthos,
phytoplankton, macroinvertebrates, amphibians and fish. The highest concentrations
of Al and Fe were measured in the filamentous algae Spirogyra fluviatilis (Hillse) and
Spirogyra adanata (Kütz), (Al = 18,997.5 mg kg-1 dry weight; Fe = 22,054.2 mg kg-1
dry weight) in the riverine zone of the lake with a near-neutral water average pH of
7.3. However, a negative correlation exists between the Al and Fe concentrations
measured in the filamentous algae in comparison to the corresponding concentrations
of these elements in the water column of the riverine zone. The Al concentrations in
the macroinvertebrate families collected ranged from 140.6 to 385.7 mg kg-1 dry
weight, with the highest values measured for Al and Fe in the family Gomphidae
(385.7 mg kg-1 dry weight and 1,710.0 mg kg-1 dry weight, respectively) in
comparison to other macroinvertebrate families sampled. Al and Fe concentrations (2,580 mg kg-1 dry weight and 10,697 mg kg-1 dry weight) in the stomach contents of
adult Oreochromis mossambicus fishes were much higher in comparison with adult
Micropterus salmoides fishes (98.5 mg kg-1 dry weight and 439.6 mg kg-1 dry
weight), respectively. In all cases of dissected fish species either white or yellow body
fat was observed, thus in none of the samples both type of body fat occurred
simultaneously The concentrations of total Al and Fe in the different organs of
Oreochromis mossambicus was along a mean sequence of intestine > yellow body fat
> brain > gills > liver > heart > white body fat, while the mean sequence of total Al
and Fe in Micropterus salmoides was: intestine > gills > liver > heart > brain > white
body fat. From the levels of Al detected in the yellow body fat of the studied fish
species Oreochromis mossambicus, we suggest that this phenomenon may be related
to the feeding habits of this species. Furthermore, the intake of certain species of
phytobenthos by Oreochromis mossambicus could have played a role in the
bioaccumulation of Al in the food chain and the possible development of pansteatitis
in predators at higher trophic levels.
