pollution

• a major problem with the use of fertilizers occurs when they are washed of the land by rainwater into rivers and lakes. this leaching causes an increase in the levels of minerals such as nitrates and phosphates in the water. this is a process called eutrophication
• What is eutrophication?

  Excessive nutrient enrichment in water bodies
• How do fertilizers contribute to eutrophication?

  They flush excessive nutrients into rivers and lakes
• What happens to aquatic plants when nutrients load up?

  They flourish, leading to algae growth
• What is the effect of algae blooms on sunlight?

  They prevent sunlight from reaching other plants
• What occurs to plants when sunlight is blocked by algae blooms?

  Plants die and oxygen levels deplete
• How does decomposition affect oxygen levels in water?

  It uses up more oxygen, further depleting it
• What happens when oxygen levels reach a critical low in an ecosystem?

  No life is possible; organisms die
• What is the final outcome of eutrophication on aquatic life?

  Fish and other organisms die due to low oxygen
• pesticides used by farmers to kill weeds or insects may also be washed or blown into streams and rivers. this may reduce the number of insects or plants in the streams and rivers
• the level of pollution in air or water can be indicated by the species living their. this is known as an indicator species
• data obtained using indicator species will only show if an areas is polluted or not.
• indicator species cannot measure pollution levels - only chemic analysis using electronic meters and laboratory tests can
• some fresh water animals (generally invertebrates) are very sensitive to oxygen levels
• if these sensitive animals are found in a river it shows that the river is clean.
• however, some animals are adapted for surviving in polluted conditions. presence or these species indicated there is a high level of water pollution