OXYGEN AND CARBON DIOXIDE

2126 WD

Aquaculture can be defined as the high-density production of fish, shellfish and plant forms in a controlled environment. Stocking rates for high-density aquaculture are typically thousand fold greater than wild environments. Modern fish culturists employ both open and close systems to raise fish. Open systems, such as, the raceways are characterized by rapid turnover of water. Closed systems are commonplace in pond culture. Closed aquaculture systems do not have rapid turnover of water, but do not have a high surface to volume ratio facilitating exchange of gases, nutrients, energy etc. with the surroundings. Water quality for aquaculturists refers to the quality of water that enables successful propagation of the desired organisms.

Physico-chemical parameters of water include: 1. Alkalinity

Alkalinity relates to the capacity of the water to accept protons and is a measure of the water’s buffering capacity. There are no direct effects of alkalinity on fish and shellfish, however, it is an important parameter due to its indirect effects, including the protection of aquatic organisms from major changes in pH. In low alkalinity waters, where CO2 and dissolved carbonates are at low concentrations, photosynthesis may be inhibited, thus restricting phytoplankton growth. Levels above 175 mg CaCO3/L reduces natural food production in ponds which, in turn, leads to a decrease in optimal production. Salt water is slightly alkaline and has a strong buffering capacity so alkalinity is not usually of concern for most seawater and brackish water aquaculturists.

2. Biochemical oxygen demand ( and COD)