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
Natural population growth on Future Population Growth in Regional Australia. Australian Geographer, 46(1), 91-111. doi:10.1080/00049182.2014.986786 Natural population growth Natural population increase (in contrast to total population increase) happens as people are born (in contrast to immigration) into a country, and decrease as people die (in contrast to emigrate). Rates of population growth, usually expressed as a percentage, vary greatly. The immigrating population has increased by a huge margin in the past few years. Due to this rising trend of migration it is important that we look into how migration has affected the population, and the trends that follow with it. The countries that