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Water Quality and Aquaculture. Choose 2 Bodies of water. One that you think has poor water quality One that you think has excellent water quality Why did you choose them. What Factors are Important. Dissolved Oxygen Temperature and Stratification pH Alkalinity Hardness
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Choose 2 Bodies of water • One that you think has poor water quality • One that you think has excellent water quality • Why did you choose them
What Factors are Important • Dissolved Oxygen • Temperature and Stratification • pH • Alkalinity • Hardness • Nitrogen Compounds • Salinity • Carbon Dioxide • Turbidity
Dissolved Oxygen 21% • Why is it import? • Fish respiration • Bacteria respiration • Generally the first limiting factor in aquaculture production • What % of the air is Oxygen? • What % of the water? 0.0008%
Where Does the Oxygen in the Water Come From? • 90% comes from photosynthesis • 6CO2 + 6H2O + energy = C6H12O6 +6O2 • 10% comes from the air water interface • Diffusion • movement from an area of high concentration to an area of low concentration
Where Does the Oxygen Go? • Respiration • Oxidation • C6H12O6 +6O2 --> 6CO2 + 6H2O + energy • Sugar + Oxygen = Carbondioxide + water + energy
Can the water have too much dissolved oxygen? • Yes, it’s called supersaturation • this means that at times the water may contain more than it can physically hold. • Caused by oxygen being added faster than it can be released from the pond • can actually poison fish and other animals in the pond
When might supersaturation occur? • When a pond has a dense algae bloom and there is hot sunny weather. • At the base of a waterfall.
How does the oxygen get depleted? • Excessive oxygen demand • Net loss of oxygen • Algal bloom die-off • Turn over
Photosynthesis by phytoplankton Diffusion Plankton respiration Fish respiration Respiration by organisms in the mud Diffusion 5 to 20 ppm 1 to 5 ppm 5 to 15 ppm 2 to 6 ppm 1 to 3 ppm 1 to 5 ppm Oxygen Gains and Losses Gains Losses
Day 1 am DO of 6 ppm bloom adds 10 ppm windy, diffusion adds 10 ppm Respiration by plants and animals in the mud 9ppm Fish respiration 3ppm Diffusion out of pond 2 ppm 6ppm +10 ppm +10 ppm = 26 ppm - 9 ppm - 3 ppm - 2 ppm = 7 ppm Example budget
Example budget - Day 2 • 7 ppm to start • + 10 ppm photosynthesis • + 1 ppm diffusion - calm day • = 18 ppm available • - 9 ppm respiration of phytoplankton and organisms in the mud • - 3 ppm fish respiration • - 2 ppm diffusion • 4 ppm left on the morning of day 3
What would happen if the weather stayed the same? Get the Aerators Ready
In most cases, a system’s ability to add dissolved oxygen to water will become the first limiting factor in a system’s fish carrying capacity.
Stay in the Zone • The most productive zone in lakes, oceans and other bodies of water is called the • This zone ends at the point where there is less than 1% of the incident light. Euphotic Zone