Читать книгу Fundamentals of Aquatic Veterinary Medicine - Группа авторов - Страница 42

In aquaculture, the nitrogen cycle eliminates ammonia from the water column by bioconversion to nitrite and then nitrate. Nitrate is used by plants, including algae, as a nutrient. This constant change from ammonia to nitrite to nitrate is called the nitrogen cycle (Figure 1.1). In ponds, this process takes place in the surface layers of the mud, but in tanks or aquaria, a special place is provided for the bacteria to live and flourish. This is called a biological filter, or biofilter. One important point to mention about the nitrogen cycle is that both groups of nitrifying bacteria need oxygen to function. If oxygen levels are insufficient, the process can slow down and the levels of ammonia and nitrite will rise in the system.

Figure 1.1 The nitrogen cycle (Francis‐Floyd, 2003).

Source: image on the right courtesy of Gillian Taylor.