Environmental Engineering Reference
In-Depth Information
overview of the basic principles is given below. The parameters mentioned have been
divided into two main categories: Critical and important parameters.
2.1 Critical water quality parameters
The critical parameters are very important in the aquacultural system. They are
temperature, pH, dissolved oxygen (DO) and ammonia. They must be measure daily, or in
the case of intensive systems, all day long. They do influence the physical properties and
chemical composition of the water, and thereafter its correct management can improve the
overall fish performance (health and growth). In the other hand, if they are not properly
attended, the consequences can be serious, varying from poor growth rates, stress, and
death.
2.1.1 Temperature
Temperature is probably the most important physical variable on aquatic ecology. It affects
directly the metabolism of all living organisms. As a consequence, temperature set the
growth, development and reproduction rates in biological species in biological species. This
fact is very useful in aquaculture: because fish do not expend energy on corporal
temperature regulation, they can assimilate almost the food nutrients into muscular tissue
(Soto-Zarazúa et al., 2011). As results of an adequate temperature condition, the biomass
production and final yield of the fish farm can increase.
It is important to remark the influence of temperature in fish respiration rate. A rise of
temperature causes more oxygen consumption in bacteria, algae and fish (Boyd, 1998).
Because respiration implies carbon dioxide release and energy consumption, the gas balance
can be dangerous for fish. If there are enough inorganic nutrients in the water, the algae
biomass can increase to considerable levels. Even some algae species can double its biomass
in only 3.5 hours (Brennan & Owende, 2010). Then, the elevated rates of nutrient
assimilation will produce significant impacts on the water quality.
In other hand, a higher temperature produces higher metabolic rates. The increment in fish
metabolism enhances the protein breakdown. As a consequence, the release of NH 3 by fish
will be high, too. The resulting combination of high temperatures with NH 3 high
concentration is very a toxic environment (Eshchar et al., 2006).
Finally, if the exposure to high temperatures is very long, the structure of the proteins
begins to break, causing fish death.
2.1.2 pH
The pH is a measure of acidity and basicity inside an aqueous solution. It indicates the
concentration of hydrogen ions on water. When pH is below 7 the solution is considered
acid, and when is above 7 is named basic or alkaline. Distilled water has a pH of 7. pH can
be defined as the negative logarithm of the molar concentration of hydrogen ions on water.
In mathematical notation, pH is described as
=log 1
[ ] =−log[ ]
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