The cattle manure affects the river ecosystem differently than manure hippos. As shown by a study conducted in Kenya, the excrement of cows consist of smaller particles and contain more nitrogen and phosphorus, which contributes to accelerated growth of microorganisms and algae. As a result, when concentrations of hippos come cow herd, freshwater ecosystems are also affected. The results of the analysis published in the journal Proceedings of the Royal Society B: Biological Sciences.
The well-being of many ecosystems depend on large herbivorous mammals. They not only form the landscape, regulating the growth of plants, but also to maintain the flow of nutrients and energy between pastures and fresh water. For example, the common hippopotamus (Hippopotamus amphíbius) feed on land, and then rest and defecate in the water. Hippo dung is a food source for bacteria, invertebrates and fish, and also changes the chemical composition of water.
Unfortunately, in most regions of the world to replace wild mammals have come cattle. Africa is no exception: on the banks of the local rivers and lakes outside of reserves and national parks is easier to see the cow herd, and not the accumulation of hippos. It is believed that such changes are harmful to freshwater ecosystems, however, clarity in this matter.
A team of specialists led by Frank Masese (Frank O. Masese) from Adoratskogo University decided to find out how to replace hippos to cows affect the flow of nutrients between land and water. The object of their study was the stretch of the Mara river in Kenya’s Masai Mara and the surrounding area. In the reserve lives of four thousand of hippos and in the surrounding buffer zone — 250,000 heads of cattle.
First, scientists compared the chemical composition and particle size of manure produced by cows and hippos. It turned out that the cattle manure is composed of smaller particles, 13 percent richer in nitrogen and 69 percent of phosphorus. It also increased the concentration of minerals, such as calcium, iron, potassium and magnesium.
Then, the team has removed several sections of the river and conducted a series of experiments whose aim was to understand how the ecosystem is affected by the inflow of manure hippos and cows in different proportions. As expected by researchers, the excrement of livestock have contributed to the more rapid growth of microorganisms and algae, on surfaces and in the water column. This was due not only to its chemical and physical properties. The fact that larger fragments of manure hippos sink to the bottom, blocking access to light and reducing the rate of growth of photosynthetic organisms. On the contrary, cow dung disintegrates into small particles that float in water and do not prevent sunlight to reach the bottom. The result is primary production of the ecosystem is increasing.
The results show that the replacement of hippos cows can radically change freshwater ecosystem. The authors note that this has implications not only for areas where wild ungulates comes cattle. The difference in the response of aquatic communities on the dung of various herbivores should be considered in large-scale projects, which involves the replacement of extinct megafauna modern counterparts.
The river Mara, which conducted the study, known as an important point on the path of the annual migrations of large herbivores. To learn more about this amazing natural phenomenon is possible from our material, “Us — darkness, and the darkness, and the darkness”. We have collected the most interesting photos taken during the great migration.
Sergey Knee High