Water Chemistry Water Quality in Aquaculture

Transcription

1 Water Chemistry Water Quality in Aquaculture

2 Water Chemistry Water Quality in Aquaculture Maintaining Water Quality Depends on: Understanding Water Chemistry Adequate Supply of Suitable Quality Water Ability to Modify Existing Conditions

3 Water Chemistry Water Quality in Aquaculture Your Animals Live in Water Where you Cannot See Them Touch Them or Inspect Them Often You Can Only See Touch & Inspect the Water Therefore in Aquaculture, You Should Manage Your Water Giving your Stocks a Healthy Environment to Grow In

4 Carp Water Quality Values Temperature C Dissolved O 2 mg/ml 5.00 ph 6-9 Suspended Solids mg/l 25 BOD mg/o 2 /l 6.00 NH + 4 mg/l 0.20 NO - 3 mg/l 6.00 Zn +2 mg/l 0.10

5 Measure Turbidity or Suspended Solids Secchi Disc

6 Diurnal Pond O 2 Changes Daylight Gains Diss O 2 EXTREMES Plankton Photosynthesis 5-20 mg/l Diffusion 1-5 Totals 6-25 Losses at Night Diss O 2 MEANS Plankton Respiration 4.32 mg/l Fish Respiration 1.08 Benthic Respiration 0.73 Diffusion 2.11 Totals 8.24 Pond area = 1 hectare with 3.2 tons catfish per hectare Temperature constant at 28 C, Diss O 2 at dawn 15 mg/l

7 Pond Organisms Can Alter Water Chemistry 1. Nitrogen Cycle Controlled by Bacterioplankton 2. Oxygen Cycle - Photosynthesis Replenishes Respiration Consumes 3. Water Chemistry is Subject to: Both Diurnal and Seasonal Changes As Are Organisms

8 Temperature I Every Organism Has an Optimal Temperature Range Temp Tolerance Range and Intolerable Extremes In Commercial Aquaculture it is Rare to Have Optimal Temperatures Year-Round Since Water Expensive to Heat or Chill, Manage Culture Regime Not the Temperature Temperature Measured with Various Thermometers

9 Focus on Stocks When: Temperature II Temperatures are in Optimal Range When Temp is Outside Optimal Range Manage Their Feed Harvest Before Temp Becomes Intolerable and Can Cause Disease or Mortality Exchange Water When-Ever Necessary.

10 Temperature III It is Not Economical to Change Temp of Large Volumes of Water In Closed Recirculating Systems with Greenhouses Can Possibly Extend Growth to Two Seasons.

11 Temperature IV Temperatures Affects Ammonia Toxicity Higher The Temperature NH 3 More Toxic Temperature Affects Oxygen Dissolution Higher Temperature, Lower Oxygen Concentration Rapid Temperature Changes Stress Stock Kill Biological Filters.

12 ph I ph Levels Determined with ph Sensitive Electrodes ph is a Measure of the Acidity or Basicity of Water ph is the Negative Logarithm (10) of the Molar Concentration of Dissolved Hydronium Ions (H 3 O + ) Respiratory CO 2 + H 2 O H 2 CO 3 Carbonic Acid That Acidifies Water Rapid Shifts in ph are as Stressful to Stocks as Extreme ph Levels For these Reasons Manipulating ph has Advantages in Aquaculture.

13 ph II ph can be Raised on Moist Bottoms to Kill Unwanted Organisms using Ca(OH) 2 Slaked Lime ph can be Lowered Using a Weak Acid in Ponds to Reduce Toxicity of NH 3.

14 Hardness Hardness is the Concentration of Multivalent Cations Such as Ca 2+ and Mg 2+ in the Water Unless You are Growing Invertebrates Or Marine Animals in Saline Waters Hardness Irrelevant Water Hardness Not an Issue Unless it s Lower Than 20 ppm as CaCO 3. Using Lime to Increase Alkalinity Also Increases Hardness

15 Alkalinity Defined Alkalinity A T is Equal to Stoichiometric Sum of Bases in Solution Ability to Neutralize H + In Practice: Alkalinity Mostly Carbonate CO 3-2 ion Common Components of Alkalinity Include: BO 3-3 CO 3-2, HCO 3-, NH 3, NO 3-, OH -, PO 4-3, SiO 4-4 Conjugate Bases of Some Organic Acids & S -2 Alkalinity is Incorrectly used Interchangeably with Basicity

16 Alkalinity I How Much Acid or Base Can you Add Without Changing the ph? Alkalinity is the Property That Stops Large Rapid Changes in ph Farmers Generally Use Lime to Increase Alkalinity In Their Ponds Not All Lime is Equal Know the Neutralizing Value CaCO 3 = 100%

17 Alkalinity II Liming increases Orthophosphate in water. Liming increases CO 2 in water thus helping increase photosynthesis. Liming helps increase microbial activity in soils by stabilizing ph, thus helping in recycling of nutrients. Liming clears water by removing humic acids. All this on top of increasing alkalinity.

18 Alkalinity III A Person Cannot Over-Lime Liming is Only Economical in Ponds with Low Water Exchange or in Closed Recirculating Systems Ground Water Usually High Alkalinity Compared to Surface Water Alkalinity Decreases with Increased productivity Liming Makes NH 3 More Toxic Because ph Increases Dissolution Not the Same for All Limes Cold Water Dissolves Lime Better

19 Nitrogen Compounds Ammonia NH 3 Ammonium NH + 4 Nitrite NO -2 2 Nitrate NO - 3 Nitrogen N 2 In Aquaculture, Nitrogenous Compounds Come Mainly from Proteins in the Feed and From Dead Organisms

20 Nitrogen Cycle Nitrification: The Biological Oxidation of Ammonia (NH 3 ) with Oxygen to Nitrite (NO 2-2 ) and its Further Oxidation to Nitrate (NO 3- ) Feed Protein Digestion Deamination NH 3 NH 3 Bacterial Nitrification NO 2-2 NO 3 - NO 3 - Anaerobic Denitrification N 2

21 Bacteria & Nitrogen Cycle Organic Matter NH 3 (Ammonia is Toxic) with ph Rxn: NH 3 + H + NH + 4 (Ammonium is Non-Toxic) Nitrosomonas Nitrifying bacterium - Chemoautotroph Rxn: 4NH 3 + 7O 2 4NO H 2 O Oxidation of NH 3 into Nitrite Which is Also Toxic) Nitrobacter Another Nitrifying Chemoautotroph Rxn: 2NO O 2 2NO 3 - (Nitrate Non-Toxic)

22 Nitrogenous Compounds III NH 3 is More Toxic than NH 4 + Low ph Favors NH 4 + If Low Oxygen & High NH 3 Change Water Before You Aerate. Aeration Removes CO 2 Raises ph And Makes NH 3 from NH 4 + Ammonia is More Toxic.

23 Nitrogenous Compounds IV NH 3 Rarely a Problem in Flow-Through Systems In Ponds, Productivity Uses Ammonia as Fertilizer In Recirculating Systems, Those that Treat Their Filter as Living Organism Rarely Have Problems Problems Arise when Filter Maintenance is Forgotten

24 Nitrogenous Compounds V % NH 3 Relationship Between ph & NH 3

25 % Free Ammonia: NH + 4 NH 3 + H + As a Function of ph and Temperature ph

26 Nitrogenous Compounds VI Nitrite Causes Brown Blood Disease in Catfish Chloride Counteracts Dissolved Nitrite In Salt Water, Nitrite is Rarely a Problem In FW Systems, Addition of NaCl Up to 2 ppt is Usually Beneficial NaCl Also Slows Down or Kills Parasites and Fights Off-Flavor Causing Cyanobacteria

27 Nitrogenous Compounds VII Nitrate Concentration Detected by Nitrate Sensitive Electrodes Nitrate Not Toxic Except in Very High Concentrations Concentrations >120 ppm Frequently Reached in Recirculating Systems Employ Water Exchange Systems to Keep Nitrate Within Acceptable Limits

28 Oxygen I Oxygen Measured by O 2 Sensitive Electrode Oxygen Problems Start with Source Water Ground Water Frequently Low in O 2 High in CO 2 Coming From the Ground Surface Water Quality Function of Source, Depth Productivity, Season & Temperature Any O 2 Problems Increase as Growing Season Progresses

29 Oxygen II Oxygen Issues in Aquaculture Include: Majority of O 2 Uptake Due to Bacteria & Plankton Not Organisms being Raised The Volume of Feed Introduced to Pond Affects O 2 Uptake Most At Low O 2 Fish Feed Less Means More Available Nutrient for Bacteria to Use

30 Oxygen III Aeration Calculated Based on Amount of Food Being Added Daily to Pond For 30 35% Protein Feed, 1 HP Aeration Needed for Every 16 Kg of Daily Feed Input to Keep O 2 > 3 mg/l In Ponds O 2 Produced in the Day and Taken Up at Night Best Time to Measure O 2 is at 8:00 & 10:00 pm Velocity of Decline in O2 Indicative of Potential Problems In Low Oxygen.

31 Aeration

32 Oxygen IV Oxygen Management Affects Other Variables Aeration Removes CO 2, Rapidly Raising ph (NH 4 + NH 3 + H + ) Aeration Speeds Evaporation Cooling the Water Aeration Mixes Water Destroying Any Thermocline

33 Warms the Water Light Affects Photosynthesis O 2 & ph Light Mainly Affects O 2 in Ponds On Cloudy Days Check DO Frequently if Water Color is Dark Green to Brown Too Much Light Penetration Bottom Macrophytes Grow Affecting Stock Feeding & Behavior

34 Particulates & BOD BOD Measure of Organic Pollution in Water Particulates Can Irritate Gills Particulates Can Affect Feeding of Small Stock Particulates Will Affect Light Penetration Organic Particulates Consume O 2 Particulates Affect Effluent Quality

35 Salinity I Affects Stock Osmoregulation Affects O 2 Solubility Affects Parasite Viability Affects Filter Rigor Affects Degree of Rain Effects

36 Environmental Factor Salinity

37 Salinity II Many Add Salt to Fight Brown Blood Disease or Parasites. Rapid Addition of Salt can Kill your Filter and Stress your Fish Many Try to Grow Marine Organisms Inland in Low Salinity Well Water Although Salinity May be Adequate the Kind of Salt is Not

38 Feed I The Biggest Input you Add to Your Pond is Feed Feed Affects NH 3, O 2, Particulates, ph & Indirectly Photosynthesis Feed is Expensive Don t Add More Than Necessary of an Expensive Detrimental Chemical like Food to Your Ponds

39 Feed II Feed That is Not Nutritionally Complete is a Waste Buy Good Feed Regardless of Price Rather Than Cheap Feed That is Inadequate Choose the Feed Formulated for Your Species The Protein, Fat & Energy Content of Feed are Important, So are Their Components

40 Feed III A Nutritionally Inappropriate Feed is Just an Expensive Fertilizer that will Spoil Water Quality Even If the Feed Formulation is Good If It is Not Stable in Water It is Useless Even the Best Feed can Spoil if Not Stored Properly Spoiled Feed can be Used as Fertilizer for Your Orchard But do Not Feed It to Your Stock

41 Fertilizer I Used Only in Pond Aquaculture Helps Productivity in Ponds Promotes Growth of Good Phytoplankton Instead of Detrimental Organisms Improves Feed Conversion Rates Dangerous Can Promote High ph Shifts Too Much Applied Rapidly Can be Toxic to Stock

42 Fertilizer II Normal Fertilizers are Nitrogen, Phosphorus Potassium N-P-K P a Problem Because its Removed by Bottom Sediments Fertilizer Should be Mixed with Water Then Dispersed Over All of the Pond In a Biosecure Facility - Chemical Fertilizer is Required Manure Unacceptable

43 Fertilizer III Fertilizers Perform Better in Waters with High Alkalinity If you Lime After you Fertilize Problems May Arise Phosphorus Might Have Migrated into Sediments Always Lime First Wait a Couple of Days Then Fertilize