Marisia - Maros Megyei Múzeum Évkönyve 32/1. (2012)

Zoology

Gabriela GRIGORAS, Marcela ROSCA--------------------------ll----------------2___

Tab. 5: Some of the minerals required by plants and their function (Walstad, 1999)

Element Nutrient form Major function in plant

Carbon COz, HC03 Structural component of all organic compounds

Calcium Ca2t Emzyme activator, intracellular „secondary messenger”, essential for cell

__________________________________membrane permeability and cell wall structure.__________________________

Iron Fe2*, Fe3* Component of enzymes for electron transport and other oxidation-reduction

reactions.

Potassium K+ Enzyme activator, charge balance.

Nitrogen NH3, NHy, NŐJ-, Component of proteins, nucleic acids etc.

______________NO;__________________________________________________________________________________

Phosphorus P043_ Component of ATP, NADP, nucleic acids, membrane phospholipids.

Iron and magnesium deficiency induces leaves discoloration (chlorosis).

Bacterial processes. Nitrogen flow and nitrification. There are several microbiological processes that occur in aquatic ecosystems.

The aquarium is an artificial environment where we apply various methods and techniques and the bacterial metabolism depends on specific nutrients storage and it places between certain limits. But the beneficial action of these processes — that cannot all be assessed by usual methods - observes as the physical, biological and chemical balance stabilizes.

Heterotrophic bacteria met into an aquarium closed system use the organic matter as energy source while the chemoautotrophic bacteria use the inorganic substance. The most of the organisms use the oxygen to accept electron for their respiration.

Among the microbiological processes that occur in natural aquatic ecosystems (hydrogen sulfide or methane oxidizing, aerobe and anaerobe decomposition, anaerobe reducing of manganese, iron or sulphate ions, denitrification etc) two of them have a significantly development into an aquarium artificial ecosystem: aerobe decomposition of organic matter and nitrification.

Nitrification reactions are a part of aquatic natural nitrogen flow:

oxigén oxigén

NH4+—---------------- N02-------------------------NO/

Nitrosomonas sp 1 Nitrobacter sp i

The toxic ammonia is transformed into a less toxic nitrate ion under the presence of bacteria and aerobe environment. The biological external filter is special built to fix the nitrification bacteria. Bu also the plants have a significant contribution to biological filtration of water, they take up the ammonium first and then the nitrate. Ammonium and nitrite levels decreased after the aquarium system start up as the ecological balance stabilizes.

The fig. 11 and 12 show the dynamics of ammonium and nitrite concentrations during the experiments. The ammonium level tends to 0 while the nitrite remains in water (even traces, at safe level for fish and invertebrates) that proves an imbalance between nitrification bacteria populations from the external filter probably caused by variable supplying of nutrients that are used by other competing biological processes or removed by maintenance operations, absolutely necessary to control organic matter, allelochemicals or nitrate level.

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