AQUACULTURE

Effects of pH Levels on Aquatic organisms

Very high ( greater than 9.5) or very low (less than 4.5) pH values are unsuitable for most aquatic organisms. Young fish and immature stages of aquatic insects are extremely sensitive to pH levels below 5 and may die at these low pH values. High pH levels (9-14) can harm fish by denaturing cellular membranes.

Changes in pH can also affect aquatic life indirectly by altering other aspects of water chemistry. Low pH levels accelerate the release of metals from rocks or sediments in the stream. These metals can affect a fish’s metabolism and the fish’s ability to take water in through the gills, and can kill fish fry.

The term "pH" was originally derived from the French term "pouvoir hydrogène," in English, this means "hydrogen power." The term pH is always written with a lower case p and an upper case H. (Colorado.us)

Testing pH
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, Student at BCC Aquaculture Center, testing hard water level.

High pH Levels Effect
At high pH (>9) most ammonium in water is converted to toxic ammonia (NH3), which can kill fish. Moreover, cyanobacterial toxins can also significantly influence fish populations. (lepo.it.da.ut.ee)

Testing pH
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High pH level.

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Water samples indicate a high pH level when tested, in this case could be adjusted by straining water through peat. The instructor at BCC compared it to "tea," which is dark, but safe for fish. Added to the aquarium, the pH level was brought down within a safe range.
Testing pH
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pH level lowered significantly after water exposure to peat moss.

Fish kill at low pH in a Norwegian river
Zoological Laboratory, University of Bergen, 5000 Bergen, Norway.
THE decline in freshwater fish populations in parts of southern Norway is associated with increasing acidity in rivers and lakes1. The salmon has been eliminated from many rivers, and hundreds of lakes have lost their trout populations. The chief cause of increased acidity is acid precipitation which is the product of the emission, oxidation and long-distance transport of air pollutants, particularly sulphur dioxide2,3. Similar observations of acid rain and the disappearance of freshwater fish populations have been made in the United States, Canada and Sweden4-6. (Nature.com)

The Acid Test: Is Your Pond pH Too Low?
News from Texas A&M University, 3/24/2006, R. Burns
Winter months are an ideal time to adjust pH and alkalinity because the treatment, usually an application of agricultural lime, takes time to have an effect," Higginbotham said. "Depending upon weather conditions, the fineness of lime used and the method of application, the time delay may be from a few days to as much as a month."
Alkalinity relates to the "buffering capacity" of water, its capacity to reduce fluctuations in pH, he said.
Pond water pH becomes low – acidic – primarily because local soils are acidic. But not all soils are acidic; not all ponds need liming. The best way to know for certain is to have a simple water test done to determine both alkalinity and pH, Higginbotham said. But generally, acid soils and consequently acid pond water are problems confined to East Texas.
"The further east of I-35 you go, and the further north of I-10, the higher the likelihood you need to lime your pond," he said. "Another way to determine if you might need to lime is if there's an agricultural liming service in your area. If not, then you probably don't need to lime your pond."
Water pH and alkalinity must be correct for pond fertility programs to work. In such a program, fertilizers containing nitrogen, phosphorus and potassium are added to encourage the growth of microscopic plants called phytoplankton. Microscopic animals called zooplankton feed on the phytoplankton, Higginbotham said.
And many forage fish, including bluegill, feed on the zooplankton. Game fish, such as largemouth bass, feed on the bluegill. The result of a properly managed fertility program is better fishing, and since the phytoplankton absorb wastes, better recreational use of the pond overall. Proper liming can improve phosphorus availability and enhance the health of the pond.
But even without a fertility program, liming can make the critical difference to fish health, particularly where soils are highly acidic such as East Texas, Higginbotham said. Low pH values are usually coupled with low alkalinity.
"Total alkalinity below 20 parts per million can result in large swings in daily pH values, which can stress fish," he said. "And a pH below 5.0 approaches the 'acid death point' for many fish species." (Continued... USDA)

Fish kills resulting from low pH (acidic water) are even less common than chemical kills. Usually pH kills occur when heavy rains wash tannin (an acidic substance found in leaves) from wooded areas. Low pH can be increased easily by applying agricultural limestone. The amount of lime required can be determined by sending samples of the mud from the pond bottom to the NCDA Soil Analysis Laboratory for analysis. (See the earlier section on liming procedures.) Contact your county Agricultural Extension Service office for assistance in sending soil samples. (NCSU)

Testing pH
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Five drops of pH indicator fluid dropped into 5ml test tube turns to green coloration indicating a high pH level in water.

Testing pH
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Matching up the coloration on color card. Each color represents a whole number down the scale, ranging from 9.0 to 5.0

Testing pH
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Deep blue coloration indicates a very high pH level in the water.

Testing pH
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Performing one of the tests, includes a 5 ml test tube of water, and drops of the solution.

Testing pH
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Fellow BCC student performing chemical hard water test.

Testing pH
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, Fellow BCC student tests pH levels, and works with special breeding project involving Guppies.

Testing pH
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Aquariums containing student projects to raise, breed and grow fish.

Testing pH
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Lab area.

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One of the fish tanks.

BCC Aquaculture Hatchery

Hatchery
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Hatchery. Several large troughs are kept with aeration in the water at all times, and contain small fish.

Hatchery
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Hatchery troughs.

Hatchery
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Fish and eels occupy these large containers, as part of on-going experiments with different forms of aquatic organisms.

Related

  • Effects of pH levels
  • Interpreting Pond Water Quality
  • Ammonia, Temperature and pH

    Ammonia 1
    Ruth Francis-Floyd and Craig Watson2

    Introduction
    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. When feed is eaten by fish it is metabolized into the energy, nutrients, and proteins used for survival and growth. As with all animals, there is waste produced by these normal metabolic processes. Ammonia is the principal waste product excreted by fish. In trace amounts, ammonia is odorless and colorless, so the only way for an aquaculturist to know if it is there is to test the water.
    Of all the water quality parameters which affect fish, ammonia is the most important after oxygen, especially in intensive systems. In small amounts, ammonia causes stress and gill damage. Fish exposed to low levels of ammonia over time are more susceptible to bacterial infections, have poor growth and will not tolerate routine handling as well as they should. Ammonia is a killer when present in higher concentrations, and many unexplained production losses have been caused by ammonia.
    In water, ammonia occurs in two forms, which together are called the Total Ammonia Nitrogen, or TAN. Chemically, these two forms are represented as NH4+ and NH3. NH4+ is called Ionized Ammonia because it has a positive electrical charge, and NH3 is called Unionized Ammonia since it has no charge. This is important to know, since NH3, unionized ammonia (abbreviated as UIA), is the form which is toxic to fish. Water temperature and pH will effect which form of ammonia is predominant at any given time in an aquatic system.

    The Nitrogen Cycle
    In aquaculture, a mechanism called The Nitrogen Cycle eliminates ammonia from the water. As ammonia is excreted, it is converted to another compound called Nitrite (NO2). Nitrite is also toxic to fish and is discussed in a separate publication. This change from ammonia to nitrite is accomplished by bacteria called Nitrosomonas. Another group of bacteria, called Nitrobacter, convert nitrite to Nitrate (NH3). Nitrate is not toxic to fish except at extremely high levels, and can be considered harmless. Nitrate is used by plants, including algae, for food. This constant change from ammonia to nitrite to nitrate is called the nitrogen cycle.
    In ponds this process takes place in the surface layers of the mud, but in tanks or aquaria, a special place has to be provided for the bacteria to live and flourish. This is called a biological filter, or biofilter. For further information on biofilters, see Florida Cooperative Service Extension publication FA-12, Principles of Water Recirculation and Filtration in Aquaculture.
    One important point to mention about the nitrogen cycle, is that both groups of nitrifying bacteria need oxygen to function. If oxygen levels are not sufficient, the process can break down, and you will start seeing levels of ammonia and nitrite rise in the system.
    Ammonia Testing
    Everyone involved in aquaculture should invest in a water quality test kit. A good water quality management program will result in fewer fish disease problems, better growth and less use of chemical treatments. The cost of a water quality test kit will pay for itself many times over, both in numbers of fish saved, and increased production.
    Most commercial ammonia test kits measure the Total Ammonia Nitrogen (TAN). As mentioned before, it is the fraction of the TAN which is in the unionized ammonia (UIA) form which is toxic. This fraction can be determined from the TAN, if you also test the temperature and pH of the water. At high temperatures and high pH, there is more UIA. Therefore, a good ammonia test kit would include a TAN test, a pH test, and a thermometer.
    Ammonia

    Acid seas threaten to make British shellfish extinct
    Sunday 12 March 2006, From Plymouth Marine Laboratory
    SHELLFISH, crabs, lobsters and a host of other familiar species could become extinct around Britain and Europe because our seas are becoming steadily more acidic.
    An official report is to warn that carbon dioxide generated by human activity, already linked to climate change, is also sharply altering the chemistry of the oceans. The gas forms carbonic acid when it dissolves into sea water.
    Some species, such as corals and certain plankton, are so sensitive to the rising acidity that they could be in rapid decline within decades. Others, such as crabs, mussels and lobsters, are more resistant, but they too will be in danger by the end of the century. All the affected organisms build their shells or skeletons from calcium carbonate, a mineral they extract from sea water but which is attacked by carbonic acid.
    (pml.ac.uk) and Ammonia, an alkali, would increase the pH whereas the oceans are becoming slowly more acidic (lower pH) because the additional CO2 we are dumping into the atmosphere is dissolving in the water, giving carbonic acid: (Carbonic Acid)

     

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