Part II An introduction to the limnology of Hartbeespoort Dam with special reference to the effect of industrial and domestic pollution

Conclusions

• 1. Hartbeespoort Dam is eutrophic with a low transparency — a condition which has developed during the past 25 years.

• 2. Is is monomictic with complete circulation during the winter months, often resulting in low dissolved oxygen concentrations throughout the dam.

• 3. The nutrient component of the water is obtained directly from the Jukskei-Crocodiel River and to a lesser degree from the Magalies River.

• 4. Rises in pH in the epilimnion were mainly caused by the photosynthetic activity of the algae in the presence of moderately basic water.

• 5. The bottom sediments in the deeper portion of the dam underwent rapid anaerobiasis after the establishment of a thermocline and oxyclinic in summer.

• 6. The density of the fauna in the bottom sediments decreases rapidly with the establishment of the hypolimnion.

• 7. The sediments are rich in iron and during summer there was an increase in the ferrous component. The soluble and acid soluble phosphorous increases in the hypolimnion after a winter minimum.

• 8. Silica content is comparable with productive water masses in other parts of the world.

• 9. The faunal associations are typical of other moderately basic and highly productive waters in the same geographical region of South Africa.