The danger of H2S on the pond Ecosystem
H2S (hydrogen sulfide) is a toxic gas that is colorless, flammable and smelly like a rotten egg. H2S emerges from biological activity when bacteria deflated organic substances in a state without oxygen (anaerobic), such as in swamps and sewage drains. H2S is formed from the process of decomposition of organic substances by bacteria. Therefore, H2S is found in oil and gas, gutters, flooded water, such as marshes and also formed in other industrial processes and biological processes.Characteristics of H2S:
- Highly toxic and deadly
- Colorless
- Heavier than air so it tends to gather and dwell on low areas
- can be burned with blue flames and the result of combustion (sulfur dioxide gas – SO2) is also a toxic gas
- Highly corrosive, resulting in rust in certain metals
- at low concentrations, it smells like a rotten egg and can paralyze the senses of human smell
In short, H2S is formed from:
Residual or exiles from the process of decomposition of organic materials, such as the rest of the feed, carcass/fish and plankton that are located at the base of the pond. The sulfate reduction process (SO42) by the sulfur-reducing bacteria group. H2S is generally toxic to most bacteria, but there is a group of certain bacteria that can use H2S as a source of energy growth. Photosynthetic anoxygenic bacteria (BFA) such as Rhodobacter, Rhodopseudomonas, Rhodospirillum, and others as well as chemolitotrof bacteria will oxidize H2S into sulfite (SO32-) and subsequent sulfites are converted into sulfates (SO42) that are not Toxic.
Because of its formation without oxygen, he H2S will only be found in the mud base of the pond/near the border between the mud and pond water surfaces. If water and mud at the base of the pond are piqued due to water currents, activities siphon or when the animal eats above the mud, then it is likely that H2S will contact with shrimp/fish and cause the condition of H2S poisoning. If you smell a foul egg when the deposition at the base of the pond is dismantled, it is an indication of anaerobic conditions and the presence of H2S gas. Practically, if we are able to smell the rotten egg from the mud of the pond, then it is worth approximately 0.0047 ppm. The concentration of H2S is ideal to be in a pond is 0 (zero).
The threat of H2S for aquatic animals is damage to gills, stress, and death. If the animal is exposed to H2S in medium and long periods of time, symptoms that may arise are reduced appetite, slow growth, increased vulnerability to the attack of other diseases and parasites, until the occurrence of Increased mortality.
The existence of H2S in ponds is influenced by pH, temperature and DO levels. The highest toxicity of H2S is at pH < 6.5. Shrimp farms generally have a pH range of 7 – 9, but we should be wary if at any time there is a decrease in pH caused by algae respiration especially in the early morning. Contrary to pH, the toxicity of H2S increases in high temperatures and conversely, high DO will lower the toxicity of H2S because the presence of oxygen can turn H2S into non-toxic forms of ions.
It is worth remembering that the H2S formation process is part of the Sulfur cycle that will continue to occur in the pond. The best way to overcome H2S is to prevent the accumulation of toxic gases in the base of the pond, namely by adding the probiotic Bacillus subtilis that serves as the decomposition of organic matter, as well as thiobacillus. These bacteria work by means of the oxidation-reduction reaction system on sulfur compounds. Some of Thio species are recommended for the prevention of H2S:
- Thiobacillus denitrificans
Serves to neutralize H2S and Nitrit through denitrification reaction
- Thiobacillus Ferooxidans
- Thiobacillus thiooxidans
- Thiobacillus Novellus
