Eutrophication die, the bacterial degradation of their biomass consumes the oxygen in the water, thereby creating the state of hypoxia. According to Ullmann's Encyclopedia, "the primary limiting factor for eutrophication is phosphate." The availability of phosphorus generally promotes excessive plant growth and decay, favouring simple algae and plankton over other more complicated plants, and causes a severe reduction in water quality. Phosphorus is a necessary nutrient for plants to live, and is the limiting factor for plant growth in many freshwater ecosystems. Phosphate adheres tightly to soil, so it is mainly transported by erosion. Once translocated to lakes, the extraction of
Natural population growth 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 are to be looked into are Denmark, Finland, Iceland, Norway and Sweden.