Sewage treatment to the environment can lead to a buildup of nutrients, called eutrophication, which can in turn encourage the overgrowth of weeds, algae, and cyanobacteria (blue-green algae). This may cause an algal bloom, a rapid growth in the population of algae. The algae numbers are unsustainable and eventually most of them die. The decomposition of the algae by bacteria uses up so much of the oxygen in the water that most or all of the animals die, which creates more organic matter for the bacteria to decompose. In addition to causing deoxygenation, some algal species produce toxins that contaminate drinking water
Plant to plant communication via mycorrhizal networks can transfer various infochemicals is that they have been show to transfer molecules such as lipids, carbohydrates and amino acids. Thus, transfer of infochemicals via mycorrhizal networks can act to influence plant behavior. There are three main types of infochemicals shown to act as response inducing signals or cues by plants in mycorrhizal networks, as evidenced by increased effects on plant behavior: allelochemicals, defensive chemicals and nutrients. Allelopathy is the process by which plants produce secondary metabolites known as allelochemicals, which can interfere with the development of other plants or organisms. Allelochemicals can affect nutrient uptake, photosynthesis and growth; furthermore,