physical and chemical characteristics of limnetic environment
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Physical and chemical characteristics of limnetic environmentTRANSCRIPT
Physical and Chemical Characteristics of Limnetic
Environment
Physical and Chemical Characteristics of Limnetic
Environment
Prepared byJitendra Kumar
Department of Fisheries Resource Management)
College of Fisheries, Mangalore
Prepared byJitendra Kumar
Department of Fisheries Resource Management)
College of Fisheries, Mangalore
• Physical and chemical characteristics of water in which aquaculture is to be plasticized is of prime importance in deciding the suitability of the water body for successful culture.
• These characteristics would differ depending on the type of water body.
• i.e. pond, tank, lake, man-made impoundment, running water or coastal water body chosen for culture.
Temperature
Solar radiation is the source of heat for all water bodies• Temperature Changes in Small Water Bodies
• Fish Pond Temperature
Stratification of water in a natural water body (lake). Formation of horizontal water current and shearing plane in upper portion (epilimnion) is shown
• Water Conditions And Depth
referred to the temperature change with depth and thermal stratification. Closely related to this are the changes in pressure, density, viscosity, buoyancy etc.
• Pressure• Density
Light,
The term light was restricted to this visible portion of the radiation spectrum .The visible light extends from about 4000 to 7000 angstrom (1 angstrom (Ao) = 10-8cm).
Turbidity
• Turbidity is a condition of water resulting from the presence of suspended matters
• (1) Settling suspended matters • (2) Non-settling suspended matters
Secchi disc, a metal painted black and white as shown, attached to a graduated chain for lowering in the water
• Yellow - due to clayey turbidity• - also water overlying a clean sandy area
• Bright-green - water over algae-covered depression• Brown - abundance of diatoms
• As fish culturists we have to be familiar with ‘greening’ of water due to algal bloom and
• The reddish-brown colour of blooms of dinoflagellates
Colour
• The importance of chemical factors, is owing to their lethal and sublethal effects on culturable organisms, and also owing to their effect on biological productivity,
• i.e. productivity of the organism in the food chain.
• This aspect is discussed separately under ‘Biological Productivity’.
CHEMICAL FEATURES
DISSOLVED OXYGEN
CARBON DIOXIDE
pH
HARDNESS
ALKALINITY
CONDUCTIVITY/SALINITY
NUTRIENT LEVELS
• Dissolved Oxygen
• The concentration of dissolved gases in water is of prime importance in considering the quality of water along with the other physico-chemical characteristics
an aquaculture pond.Oxygen levels within the bottom layer of the pond can drop to lethal levels especially for bottom dwelling culture animals such as freshwater crayfish.
Carbon Dioxide, pH, alkalinity and hardness
• These aspects of water chemistry are closely linked together.
• All these have great bearing on the quality of water and these help determine the productivity of the water body.
• We shall first take up CO2 in water.
Carbon dioxide
• Carbon dioxide content in air is only 0.03%, but it is highly soluble in water unlike oxygen.
• CO2 stays in free (dissolved) or bound form (bicarbonate and carbonate) in water depending on the pH of the water.
• CO2 + H2O H⇌ 2CO3 H⇌ + + HCO-3 H⇌ + + CO=
3
pH
• pH is defined as a negative decimal logarithm of the hydrogen ion activity in a solution.
Diurnal fluctuations of pH will occur due to the amount of aquatic life within a pond. With higher algae concentrations, more CO2 is removed from the system and hence pH levels will rise. The reverse will occur at night when more CO2 is produced therefore leading to a drop in pH levels.
[email protected] change in pH in fish pond with moderate and low alkalinity waters
[email protected]• pH limit of biological activities in fish
Alkalinity & Hardness
• Alkalinity and hardness are closely related, since calcium and magnesium
• Which cause most of the hardness of waters• Generally associated with carbonate minerals • Which are the principal sources of alkalinity.
An optimum alkalinity level within the pond will prevent extreme diurnal pH fluctuations.
References • Odum, E.P.(1983), Basic ecology, Liminiting factors and the
physical environment, pp 221-284.• Jhingran, V.G. (1991), Fish and Fisheries of India, Fish
culture in fresh water pond, Ecology, pp 273-328.• http://www.fao.org/docrep/field/003/AC174E/
AC174E00.htm#TOC• http://en.wikipedia.org/wiki/Algaculture• http://www.fao.org/docrep/field/003/AC174E/AC174E00.htm• Waters, Boyd (1998),Acceptable Concentration Ranges for
Dissolve Inorganic Substances in Aquaculture Pond, Water Quality for Pond Aquaculture
(http :// www.neospark.comimagesWaterqua.pdf)
