nitrogenous compounds, metal toxicity, pesticides problem in aquaculture and aquarium

1. Water quality problems in fish
Nitrogen components and metal toxicity
By
Abisha.S.J
MFT160085

2. Nitrogen components

3. Ammonia
•Ammonia is a major metabolic waste product from fish.
•It is excreted across the gill membranes and in the urine.
•The primary source of ammonia in aquaculture systems is
fish feed.
Ammonia exist in 2 forms
Ammonium ions
Free Ammonia

4. Water temperature ↑ Ammonia ↑
PH ↑ Ammonia ↑
But
Salinity ↑ Ammonia ↓
Ammonia is more toxic at low DO
Major sources
Excretory product of fish
Decomposition of organic
wastes
In aquaria ammonia toxicity is
through inadequate biofiltration

5. Lowest lethal limit of toxicity for fish – 0.2-0.5 mg/l of free
ammonia
Maximum level of ammonia that fish can tolerate is 0.01-
0.02 mg/l

6. Toxicity of Ammonia depends on
Species of fish
Exposure to level of free Ammonia
Period of exposure
Any previous acclimatization effects
Exposed Fish
•Changes in blood chemistry
Ex- Raised pH
Osmoregulatory problems
Respiratory difficulties

7. Physiological effects
Disturbs Osmoregulatory system by increasing Fish
permeability
In FW fish - increases Urine flow
In MW fish - increases Drinking rate
Respiration is affected
Ammonia attack and destroy mucus of gills and cause
them to swell up
This stimulate hyperplasia.

8. At high levels – Ammonia acutely lethal to fish
Destroys epithelium of skin and gut causing hemorrhage
Affects fish’s CNS causing
Excitability and
abnormal swimming
Exposure to Chronic – sub lethal levels
Results in Growth suppression

9. Control measures
In emergency situations
Ammonia quickly reduced by
 Partial water exchange
 Addition of Zeolite
 Transfer of fish to ammonia free water

10. Long term measures
Improving biofiltration
Reducing SD
Removing other sources of ammonia by reducing
the level of organic wastes

11. Nitrite
Less toxic than ammonia
Nitrite toxicity influenced by environment factors
Water hardness reduces nitrite toxicity
It occurs when there is inadequate biofiltration

12. Fish Exposed to Nitrite
Gills absorbs NO2
Enters the blood
Within blood oxidises the respiratory pigment (Hg) into
methemoglobin
Methemoglobin is less efficient in carrying Oxygen to tissues

14. Lethal level -10-20mg /lit
Lethal toxicity varies with species
Eg- Guppies can tolerate upto 100mg/Lit
Discus -0.5mg/lit can cause disease
Nitrite poisoning causes
Listlessness
Anorexia
Pigmentation of liver, spleen,
kidney

15. Behavioural symptoms
 Increased Gill beat rate
Piping at the water surface
It could cause Cardiac arrest
Chronic exposure to sub lethal nitrite levels
Linked with ↑ susceptibility to bacterial infections
Fish has brown
blood and brown
gills

16. Control measures
By partial water exchange
By improving biofiltration
(to allow greater colonisation of Nitrobacter)
Addition of NaCl at 100 mg/l to water reduces nitrite
toxicity in case of cyprinids
Hard water reduces nitrite toxicity

17. Nitrate
End product of bacteria- mediated nitrification under
aerobic condition.
More toxic in salt water than fresh water.
It has Lowest limit of lethal toxicity of 50-300mg/lit

18. General information about nitrogen component problems in
aquaria
New tank syndrome- due to that the filter has not fully matured
High Ammonia and nitrite indicates that the filter is overloaded
 either the fish population is too large
 filter bed is too small
Overfeeding also cause this overloading effect

19. Another cause is excessive cleaning of filter medium
High Ammonia and nitrite indicates that the filter bacteria
have been inhibited or destroyed by some type of toxins
Bacterial filter toxins takeup in the form of insecticides
pesticide- methylene blue and some antibiotics also have
same effect

20. Heavy metals
Small quantity of such heavy metals are needed for
fish.
Eg- Zinc is the component of enzymes.
When present in high concentration these heavy
metals are toxic to fish
4 common metals are studied
Copper
Cadmium
Mercury
Zinc

21. The most common metal pollution in freshwater comes from mining
companies. They usually use an acid mine drainage system to
release heavy metals from ores, because metals are very soluble
in an acid solution.

23. Metals in water can exist as several chemical forms depends
on the water hardness,pH value, temperature & dissolved
substances in water
Eg- Cu is more soluble in soft water (exist as highly toxic as
free Cu) while in hard water it forms calcium carbonate.
This calcium carbonate precipitates out and less toxic to fish.

25. Diagnosing lethal doses of heavy metals is extremely difficult.
Most metals damage the blood,internal organs & gill damage
Copper and Zinc causes- Respiratory stress by damaging gill
lamellae.
Cadmium is linked with vertebral damage in common minnows
Water chemistry influences metal toxicity.
Hardness reduces Heavy metal toxicity of copper.
Iron and lead should never be present in levels above 0.03mg/l
Cu levels should be half that 0.015mg/l

26. Pesticides
Water supply companies add insecticides to the water
to kill any pests such as Water lice.
These insecticides may take the form of pyrethrin
or permethrin.

27. Susceptibility to pyrethrin and permethrin depends upon
sp.
Killifishes- die within 48hrs at level of 74µg/lit
Trout – die within 48hrs at level within low as 2.5-6µg/lit
Harmful directly or indirectly.
Most are non specific poisons
Eg-organophosphate inhibits
cholinesterase activity in
vertebrates

28. In affected animals
 normal nerve functions are grossly disturbed
Results in death due to asphyxiation
These chemicals are biologically active for only a few days. So
the effects are acute poisonings or fish kills
Simillarly pesticides at low concentration can severely affect
the aquatic ecosystem by killing the invertebrates