The Impacts of Alkaline pH on Aquatic Environments

Alkalis are bases which readily dissolve in water, and a certain degree of alkalinity in a body of water is not only natural, but necessary. When the amount of alkali in a body of water causes the pH level to rise significantly above a neutral 7.0 pH, however, damage will begin to occur to the organisms in the body of water. A sufficiently high level of alkalinity will cause not only the death of aquatic life, but will intensify other toxic substances present in the water.

Improved Health Of Freshwater Aquatic Plants

• According to a study performed in 2009 at a shallow Central European soda lake, freshwater aquatic plants thrive on an alkalinity well above a neutral pH of 7 (most bodies of freshwater have a pH between 6 and 8). Levels of alkalinity below a pH of 6 actually induce fairly substantial plant mass degradation. Within a month of exposure to low alkalinity, the aquatic plants being studied had lost a third of their mass.

  An overly alkaline body of water with a pH over 9 will, however, fairly quickly kill existing plant life, and slow the development of new plant life.

Physical Damage In Fish

• While an alkali-deficient body of water with a pH level less than 6 becomes acidic, and therefore inhospitable to plant and marine life, an unusually high pH level over 9 can wipe out adult fish populations and retard the development of newly hatched fish. The telltale symptoms of overly alkaline water, in regards to fish, will be damage to the eyes, skin, and gills of the fish, including the loss of "shine" to the scales of the fish.

Increased Toxicity Of Other Present Elements

• One unusual aspect of alkali in water is that, at high levels, they increase the toxicity of surrounding substances in the water. An example given by Lenntech, a manufacturer of water treatment systems, is that of ammonia: At a pH of 8, ammonia's toxicity is 10 times greater than when the water medium it resides in has a pH of 7.