This study focsed on both the physical conditions and the micro organisms of the water in relation to the extent of hippo activity. Although seven substances were tested for, focus was on organic compounds essential for plant and animal growth and health. The organic compounds included nitrates, amonia, and phosphates. It is hypothesized that in area of heavy hippo activity there will be an increase in the levels of these nutrients, thus creating a more favorable environment for many species in the aquatic ecosystem.

In nature nitrogen occurs in many forms, including nitrate, nitrite, ammonia and organic nitrogen. Total nitrogen, "Kjeldahl nitrogen", refers to the total of organic nitrogen and ammonia nitrate.(2) Nitrogen is required for the formation of amino acids, and is therefore essential for life. Although nitrogen composes 79% of the earth's atmosphere, it must be converted from the gaseous phase into nitrates and nitrites through the process of nitrification. This process is carried out by nitrogen fixing bacteria, blue green alage, lichens, and epiphytes. Ammonia is mainly produced by the hydrolysis of ureas and the breaking down of nitrogen containing compounds but is also created when nitrate is reduced under anaerobic conditions. Ammonia is usually found in natural waters in concentrations less than 10 ug/l, however in areas of intense agriculture or high amounts of degrading biomass, ammonia levels may be elevated. Another compound tested for in this study was nitrate. Generally only traces of nitrate are present in surface waters, but underground sources often contain high concentrations of nitrates. Many photosynthetic autotrophs rely on nitrates, and thus nitrates are considered a limiting nutrient.

Phosphorus occurs in the form of phosphate which may be orthophosphate, condensed phosphates, and organically bound phosphates. (2) Phosphorus has been identified as a primary nutrient and is essentail for the survival of aquatic plant and animal life, however, it is a limited resouce in most aquatic systems. In most natural fresh water, the phosphorus to nitrogen ratio is 1:23 (8) Phosphorus has its reservoir in bedrock and is made available to organisms when erosion releases the small particles of phosphorus into the environment. For this reason, the recycling of phosphorus in the ecosystem is important, and animal waste is one pathway phosphorus can utilize to remain in the system. A surplus of phosphorus often results in a sudden flourish of life and plant growth, which in turn utilize the oxygen in the water, thereby reducing its ability to support life.

In addition to amonia, phosphates and nitrates, the levels of potassium were tested. Potassium is classified as an alkali metal, and due to its extremely reactive nature, it is rarely found in an uncombined form. Potassium is a vital constituent of plant and animal tissues and is an important element in nature. Potassium affects the ionic balance of cells and is an important factor in the protein synthesis and carbohydrate metabolism.(6)

The levels of calcium, magnesium and sodium were also determined. These elements are usually found in low amounts in fresh water, however, a high level of any of these substances could indicate an upset in the natural balance of the aquatic system. Calcium and magnesium together are expressed as the total hardness and recorded as carbonate mg/l. Calcium is a vital element for creatures such as snails and mollusks, and these animals can not be found in an aquatic system that contains less than 20 mg/l.(6) Calcium also affects the permeability of membranes and is necessary for both formation of cell walls and an activator for several enzymes.(6) Magnesium is crucial for carbohydrate metabolism, nucleic acid synthesis, and in ATP reactions 6). Sodium occurs naturally and creates a saline taste in water. In the Kalahari system, which is primarily a sand velt, water has been found with a salinity three times the concentration of ocean water. As hippos stir the river bed sediment, excess sodium may be released and so sodium concentraions were measured.

Total dissolved solids and electrical conductivity were also tested. Electrical conductivity is the ability of water to carry an electrical current, and this property increases with temperature, concentration of dissolved solids and substances such as sodium.

Turbidity describes the clarity of water and is determined by recording the percentage of light that is scattered by the suspended particles when a beam of light is shone through the sample. In areas of higher aquatic life the researcher suspected that turbidity may increase due to the surplus particles in the water, thus areas of higher hippo concentration may have a higher turbidity.

The pH of water was tested at each location. pH usually lies in the range of 4-9 for freshwater, however tends to be slightly basic due to the presence of carbonates and bicarbonates. The pH is greatly affected by the carbonate-bicarbonate-carbon dioxide equlibrium with in the water.

Plankton and micro organisms are valuable indicators of the health of an aquatic system. Plankton are small organisms that are unable to resist the natural flow of the current and form the base of the food chain. When water conditions are favorable they flourish, and algae blooms often result under eutrophic conditions. Due to their short life cycles they respond rapidly to subtle fluctuations in the environment, and a variation in their population may be an indication of a disturbance with in the ecosystem's natural balance. Plankton are classified as either zooplankton (protozoans, rotifers, cladocerans, copepods, small crustaceans, worms, larva, dinoflagellates, and foraminifera), or phytoplankton (bacteria, microscopic fungi and algea such as diatoms, golden algae, green algae and blue-green algae). The zooplankton are very high in protein and are important nutrient generators, however they have the ability to absorb and release toxins. These toxins are then moved upward through the trophic levels and become increasingly concentrated and hence more harmful at the next level. Phytoplankton are the primary producers in aquatic systems and carry out photosynthesis. "Water quality affects the abundance, species composition and diversity, stability, productivity, and physiological condition of indigenous populations of aquatic organisms. Therefore, and expression of the nature and health of the aquatic communities is an expression of the quality of water."(3) It is hypothesised that in areas of intense hippo activity there are additional nutrients, thus the plankton density will be greater than when compared to areas of no hippo activity.