Role of Dissolved Oxygen in

Role of Dissolved Oxygen (DO) concentration in Aquaculture with special reference on shrimp farming : 

Role of Dissolved Oxygen (DO) concentration in Aquaculture with special reference on shrimp farming Sachin O. Khairnar Ph.D Scholar (Aquaculture Ecology) Ocean University of China, Qingdao

Introduction : 

Introduction The oxygen contained in water is termed “dissolved oxygen”. The amount of oxygen dissolved in water at a certain time, expressed in ppm or mg/L. oxygen gas dissolved in water. It is essential to the organisms living in aquatic environment. DO levels are considered a most imp indicator of a water body's ability to support desirable aquatic life. The availabilty of DO frequently limits the activities and growth of aquatic animals. FISH/SHRIMP

Slide 3: 

although oxygen is rather abundant in the atm (21%), it is only slightly soluble in water (6 mg/L is not much) the oxygen content in aquatic environment varies much more than in air if dissolved oxygen is in pond ecosytem is consistently low animals will not eat or grow well and will be susceptible to infectious disease. if concentration falls to very low levels, animal may die. Therefore, managing the DO content of the water in a culture system is of critical importance (1) keep the animals alive (2) to increase the production capacity of the system.

Sources of Dissolved Oxygen : 

Sources of Dissolved Oxygen major producer of D.O. in ponds is primary productivity (up to 80%), diffusion is low (<3%) incoming water can often be deficient depending upon source water conditions major consumers: primary productivity, aquatic species (density dependent), COD diel fluctuation indirect relationships (algae, secchi)

Oxygen Solubility Curve : 

Oxygen Solubility Curve Solubility decreases with increased temp/sal

Daily fluctuation in surface dissolved oxygen concentration in a shrimp pond : 

Daily fluctuation in surface dissolved oxygen concentration in a shrimp pond Graphical presentation of fluctuaton of DO in shrimp farming

Effects of DO on fish/shrimp : 

Effects of DO on fish/shrimp What might be considered minimal levels of maintenance of D.O.? hard to determine due to compounding effects (can’t standardize conditions) major factor: exposure time for most species: long-term: 1.5 mg/L medium term: 1.0 mg/L short-term: 0.3 mg/L

Determination of DO by chemical method : 

Determination of DO by chemical method 1. Accurate 2. Water samples can be held for a period of time before measurements 3. Time consuming with multiple measurements Dissolved Oxygen Kit

Determination of DO by Electronic method : 

Determination of DO by Electronic method Accurate Multiple measurements are done quickly Need to calibrate meter Electronic DO meter

Dissolved Oxygen in Aquaculture Ponds : 

Dissolved Oxygen in Aquaculture Ponds The major difference between aquaculture ponds and other surface waters is that the biomass of bacteria, plants and animals is much greater in aquaculture ponds. Biological processes tends to dominate the dissolved oxygen budget of aquaculture ponds High biological activity in some aquaculture ponds can lead to pronounced daily cycles in concentration of dissolved oxygen To avoid the declination of dissolved oxygen aerators are used.

Factors affecting DO (Dissolved Oxygen) concentrations : 

Factors affecting DO (Dissolved Oxygen) concentrations Air-water gas transfer Sediment oxygen uptake Animal respiration Photosynthesis and plant respiration

Air-water Oxygen transfer : 

Air-water Oxygen transfer Relation with Atmospheric pressure What happens when water is at equilibrium with atmospheric oxygen? What then if water is undersaturated? What if water is supersaturated? The greater the degree of undersaturation or supersaturation,the faster oxygen will enter or leave the film. What when water is undisturbed?

Slide 13: 

Air-water oxygen transfer dominates dissolved oxygen budgets when water temperatures are low. Under windy conditions, rates of air-water oxygen transfer increase greatly. What happens when aerators are used?

Sediment Oxygen Uptake : 

Sediment Oxygen Uptake Sediment oxygen uptake results from oxygen consumed in various chemical reactions and in respiration of mud-dwelling organisms Respiratory oxygen use includes oxygen used in the aerobic decomposition of organic matter by heterotrophic bacteria oxygen used in the oxidation of reduced inorganic substancesby autotropic bacteria (such as oxygen consumed in the oxidation of ammonia to nitrate by nitrifying bacteria),

Slide 15: 

Most of the total sediment oxygen uptake in aquaculture ponds results from biological processes Sediment oxygen uptake is somewhat difficult to measure accurately and values differ greatly from pond to pond and with location within individual ponds. Measured rates of Oxygen uptake by aquaculture pond sediments range from less than 50 to over 500 mg oxygen/㎡ of sediment surface per hour.

Animal respiration : 

Animal respiration Oxygen consumed by fish and crustaceans under culture conditions depends upon 1. size and species 2. water temperature 3. activity 4. time after feeding 5. ambient dissolvd oxygen conc.C6H12O6 + 6O2  6CO2 + 6H2O + heat energy

Photosynthesis and Plant Respiration : 

Photosynthesis and Plant Respiration Plankton metabolism is the major component affecting dissolved oxygen Phytoplankton Photosynthesis is the largest source of oxygen Phytoplankton Respiration is the largest sink for oxygen Difference between daily basis and High standing crop

Regulatory measures of dissolved oxygen in shrimp farming (It means what to do when DO drops ?) : 

Regulatory measures of dissolved oxygen in shrimp farming (It means what to do when DO drops ?) Water exchange add aerators aeraton time apply H2O2, CaO2 Reduce feed by 50-70% or cancel meal check pond bottom add vit C to feed apply Probiotic

THANK YOU : 

THANK YOU