VIVO_1-2013-en

Pond environments10 Part 5 by Dr. Bodo Schnell Atmospheric air contains approximately 21% oxygen which is mainly being produced by plants. It dissolves in water fairly well, and thus makes animal life possible. A part of the dissolved oxygen is directly formed by plants living in the water, another part is taken up from the air via the surface. Oxygen I t is well known that oxygen is essential for the respi- ration of all animals, and fish are no exception. Good oxygen supply is therefore important. The oxygen requirements of different pond fish differs depending on their natural habitat. Fish from warm, slowly flowing or standing water require considerably less oxygen than species from cool or rapidly flowing water. Besides respiration, oxygen ensures oxidative breakdown of organic waste matter such as waste, dead plant parts, leaves that have fallen into the pond etc. This breakdown is mainly carried out by bacteria, fungi and other microorganisms. These organisms uti- lize waste as nutrients and convert them into mainly harmless breakdown products. The oxygen require- ment depends on the species, number and size of the fish, on feeding, presence of other pollutants as well as on the water temperature. Live processes are quicker in warm water, however the saturation concentration becomes lower at the same time. Careful monitoring and, if required, additional oxygen supply are therefore particularly important during summer. Insufficient oxygen supply is dangerous: Due to the above mentioned breakdown processes, it may happen that not enough oxygen is left for respiration. Furthermore, pollutant breakdown also takes place in case of oxygen deficiency (anoxic breakdown). How- ever, dangerous, toxic and foul-smelling breakdown processed are being formed during this process – this is called rotting. This must by all means be avoided in ponds. Leaves that have fallen into the pond must be removed immediately as to avoid oxygen deficiencies arising from their decomposition. Considering good pond hygiene that largely reduces problems and dis- ease outbreaks, good oxygen supply is therefore indis- pensable. ©Vima–shutterstock.com Indispensable for healthy life in a pond

VIVO_1-2013-en

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