Factors Limiting The Productivity Of Aquatic Habitats
SUNLIGHT:
- Sunlight penetration rapidly diminishes as it passes down the column of water. The depth to which light penetrates a lake determines the extent of plant distribution.
DISSOLVED OXYGEN:
- In aquatic ecosystems oxygen is dissolved in water, where its concentration varies constantly depending on factors that influence the input and output of oxygen in water.
- In fresh water the average concentration of dissolved oxygen is 0.0010 per cent (also expressed as 10 parts per million or 10 ppm) by weight, which is 150 times lower than the concentration of oxygen in an equivalent volume of air.
- Oxygen enters the aquatic ecosystem through the air water interface and by the photosynthetic activities of aquatic plants. Therefore, the quantity of dissolved oxygen present in an ecosystem depends on the rate at which the aforesaid two processes occur.
- Dissolved oxygen escapes the water body through air water interface and through respiration of organisms (fish, decomposers, zooplanktons, etc.)
- The amount of dissolved oxygen retained in water is also influenced by temperature. Oxygen is less soluble in warm water. Warm water also enhances decomposer activity.
- Therefore, increasing the temperature of a water body increases the rate at which oxygen is depleted from water.
- When the dissolved oxygen level falls below 3-5 ppm, many aquatic organisms are likely to die.
TRANSPARENCY:
- Transparency affects the extent of light penetration. Suspended particulate matters such as clay, silt, phytoplankton, etc. make the water turbid.
- Consequently it limits the extent of light penetration and the photosynthetic activity in a significant way
TEMPERATURE:
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The water temperature changes less rapidly than the temperature of air because water has a considerably higher specific heat than air, i.e. larger amounts of heat energy must be added to or taken away from water to raise or lower its temperature.
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Since water temperatures are less subject to change, the aquatic organisms have narrow temperature tolerance limit.
• As a result, even small changes in water temperature are a great threat to the survival of aquatic organisms when compared to the changes in air temperatures in the terrestrial organisms.