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
Carnivorous plant or digestion of prey. Only one trait needs to have evolved that fits this adaptive requirement, as many current carnivorous plant genera lack some of the above-mentioned attributes. The second requirement is the ability to absorb nutrients from dead prey and gain a fitness advantage from the integration of these derived nutrients (mostly amino acids and ammonium ions) either through increased growth or pollen and/or seed production. However, plants that may opportunistically utilize nutrients from dead animals without specifically seeking and capturing fauna are excluded from the carnivorous definition. The second requirement also differentiates carnivory from defensive plant characteristics that