Water Quality and Disease

1
Water Quality and Disease

• Dr. Craig Kasper
• Aquaculture Disease Processes
• FAS 2253C

2
Aquatic Environment

• Water quality and quantity is one of the most
  important factors to maintain fish health.
• Inadequate water quality causes more losses than
  any other problem!
• Factors that influence water quality/quantity
• Feed rates
• Feed types
• Flow rates
• Tanks/containers (flow dynamics)
• Temperature

3
Water Quality

• Daily or weekly tests

• Semi-annually or annually

4
Daily or Weekly

• Dissolved oxygen
• Nitrogen compounds
• ammonia
• nitrite
• nitrates
• pH
• Alkalinity
• Hardness

• Carbon Dioxide
• Temperature
• Hydrogen sulfide
• Total suspended solids
• Chlorine

5
Dissolved Oxygen

• Importance
• highest cause of mortality
• Solubility
• variables
• Safe levels

6
Dissolved Oxygen

• Uptake influenced by condition of gills
• healthy gills, uptake easy
• damaged, oxygen uptake impaired

7
Oxygen Requirements

• Dependent on temperature
• Dependent on demands of organisms
• baseline 02 measure
• sessile normal
• feeding elevated
• active elevated
• stressed? elevated
• CO2 elevated depressed

8
Nitrogen Compounds

• Types
• dissolved gas
• ammonia
• ionized
• un-ionized
• nitrite
• nitrate

9
Ammonia

• Ammonia
• NH3, NH4
• Two forms
• unionized NH3
• ionized (NH4)
• pH a concern when dealing with exposure
• Chronic exposure (un-ionized form)

10
Nitrogen Equillibria NH3/NH4

• ammonia (NH3) is toxic to fish/inverts
• pH affects proportion of NH3/NH4
• as pH increases, NH3 increases
• calculation example TAN 1.5 mg/L, 26oC, pH
  8.6
• answer 0.30 mg NH3/L

Affect of pH/temp on NH3/NH4 equillibria (next
slide)
11
Nitrogen Equillibria NH3/NH4

• ammonia (NH3) is toxic to fish/inverts
• pH affects proportion of NH3/NH4
• as pH increases, NH3 increases
• calculation example TAN 1.5 mg/L, 26oC, pH
  8.6
• answer 0.35 mg NH3/L

Affect of pH/temp on NH3/NH4 equillibria
12
Ammonia Prob. How do I fix it?

• Lower pH below 7.0 (why?)
• -25 - 50 water change
• -Use chemical to neutralize ammonia (zeolite)
• -Discontinue or reduce feeding
• -NH3 gt1 ppm treat immediately!

13
Ammonia Toxicity
14
Nitrite

• Nitrite (NO2-)
• Secondary product of nitrification
• Nitrite levels greater than 0.05 to 0.06 mg/L
  can be toxic!
• 10 times stronger than the toxic threshold for
  unionized ammonia
• Decreasing pH increases the harmful effects.

15
Nitrite

• Brown blood disease (p. 67 in Noga)
• (Methemoglobinemia)-new-tank syndrome
• Blood appears dark in color
• Due to excessive presence of methemoglobin
• Treatment
• Flushing with fresh water
• Add nitrifying bacteria
• Salt! Recommend 101 ratio
• Hypertrophy and hyperplasia in the gill lamellae
• Lesions/hemorrhaging in thymus

16
Nitrite (NO3-) Toxicity
17
Nitrate

• Nitrate (NO3-) is the final breakdown product in
  the oxidation of ammonia
• Not as toxic to aquatics
• Similar symptoms to nitrite toxicity, but values
  must be much higher.

18
Nitrate Toxicity
19
Nitrification Good or bad?

• Requires 3 moles oxygen to convert one mole of
  ammonia to nitrate
• Nitrification is an acidifying reaction

20
Relationships
21
pH

• Measure of the hydrogen ion concentration
• 1-14 scale
• less than 7 acidic
• greater than 7 basic
• Safe range
• 6.5-9

22
Carbon Dioxide (CO2)
CH2O (food) O2 ? CO2 H2O

• Sources
• Surface
• Wells
• carboniferous rock
• Removal
• degassing
• buffers
• calcium carbonate
• sodium bicarbonate

23
Alkalinity

• Alkalinity is the capacity of water to buffer
  against wide pH changes.
• Acceptable range 20-300 mg/L

Bicarbonate CO2 H2O ? H HCO3-
Carbonate HCO3- ? H CO3-
Effects of calcite lime
CaCO3 CO2 H2O ? Ca2 2HCO3-
Dolomite CaMg(CO3)2 yields 4HCO3-
24
Hardness

• Hardness is the measure of divalent cations
• Ca 2, Mg 2, Mn 2
• Calcium is used for bone and exoskeleton
  formation and absorbed across gills
• Soft water molt problems, bone deformities
• Suggest gt 50 ppm
• Hardness is used as an indicator of alkalinity
  but hardness is not a measure of alkalinity
• Magnesium or calcium sulfate increases hardness
  but has no affect on alkalinity

25
Hydrogen Sulfide (p. 225-226, Noga)

• Source
• Well water
• Ponds
• Anerobic conditions of benthos
• Under net-pens
• Extremely toxic to fish
• Removal
• Aeration
• Raise pH
• Lower temp.
• Add Potassium Permanganate (freshwater only!)

26
Total Solids

• Types
• suspended
• settleable
• Sources
• runoff
• uneaten food
• feces

• Safe levels
• less than 1,000 mg/L
• Removal
• filtration
• settling chambers

27
Suspended Solids

• Potential problems
• Light?
• Turbidity?
• Gills?
• Reduce oxygen transport
• 80 - 100 ppm TSS reasonable for salmonids

28
Chlorine

• Disinfectant
• Cl2 (Chlorine gas choramine-T)
• HClO (hypochlorous ion) (bleach)
• Safe levels
• less than 0.03 mg/L
• Removal
• Aeration
• Chemical (Sodium Thiosulfate, 200 mg/L available
  chlorine is neutralized by 1.5 g sodium
  thiosulfate)
• Sunlight
• Chlorine reacts with water to form strong acid

29
Chlorine toxicity

• Acid is more toxic than hypochlorite ion
• Destroys epidermal surfaces gills
• Toxicity depends on temp, DO, free chlorine
  present, presence other pollutants
• Residual chlorine (free plus chloramine)0.2 -
  0.3 ppm kills fish rapidly (ornamentals 0.09
  ppm!!)
• Chlorine and nitrogenous organics chloramines
  that are very toxic

30
Temperature

• Effects
• Alters metabolism
• Effects pathogens
• Changes gas solubility
• Fish Categories
• warmwater
• coolwater
• coldwater

31
Heavy Metal Contaminants

• Heavy metals - Cd, Cu, Zn, Hg, must be all lt .1
  mg/L.
• Old plumbing systems are problematic (Cu2, Zn
  alloys)
• Soft water makes a difference in toxicity of
  metals (increases uptake)
• Most can be removed by using activated carbon
  filters!

32
Dissolved Gasses

• Problem gasses
• Oxgen?
• maintain less than 110
• Problem sources
• Wells
• Leaky pipes
• Solved by using degassing
• columns

33
Characteristics of gas bubble disease

• Bubbles under skin (cracklesjust like diving)
• and other soft tissuesfins, tail, mouth
• Gas emboli in vascular system death
• Similar to bends or decompression sickness

34
Spill vs. no spill management of Columbia River

• History - Excess water removed used to be a big
  problem.
• Rough guidelines for negative responseClean
  Water Act says 110 is standardwhat difference
  between 110 and 120?
• Lethal Leves for salmonids
• 103 104 yolk sac and fingerlings
• 105- 113 older fingerlings and yearlings
• 118 adults

35
Columbia River

• In 1960s in Columbia River,
• Adults
• Exophthalmia
• bubbles in skin and mouth
• hemorrhaged eyes later cause blindness - impair
  spawning
• External symptoms disappear rapidly after death
• Changed water use and flip lips
• 1990s high spill head burns in salmon

36
Does Compensation Occur?

• One meter depth about 10 reduction in gas
  saturation.
• Late 1970s fish were deeper than 1.5 m in 110
  saturation.
• Fish were using shallower water in normal
  saturation.
• Fish ladders require fish to come to surface or
  near surface.

37
Questions/uncertainty

• Behavioral Compensation? Does it occur?
• Migration pathways for Adult salmon
• Migration pathways for juvenile salmon
• How good are flip lips?
• Voluntary vs non-voluntary spill issues?
• Immediate vs delayed mortality?
• Predisposition to other invasions?