Assessing the impact of human activities on Ecosystems 2 -Water Quality Lesson 12 September 13th, 2010

Assessing water Quality Water is essential to all life. Protecting water quality is essential for sustainable ecosystems. Many aspects of water are used to assess its quality

Aquatic Organisms Healthy aquatic ecosystems are full of organisms. These include: Fish, large pants, invertebrates, plankton, bacteria, and viruses. Sometimes, the types and quantities of species present in the water can indicate that the water is unsafe.

Aquatic Organisms Indicator organisms include certain insects and insect larvae, shrimp, clams, and worms. Different organisms prefer different conditions. For example, some organisms can survive in polluted water, while others cannot.

Oxygen -Aquatic organisms need the oxygen gas that is dissolved in the water. Dissolved oxygen measurements give the level of oxygen present in water. -If levels of oxygen drop below a certain level, fewer organisms are able to live in that body of water.

Oxygen

Biological oxygen demand (BOD) Measures how quickly oxygen is used up by micro-organisms in a given body of water BOD is an effective test for certain types of water pollution. Polluted water can promote the growth of some micro- organisms, which feed off the pollution. These organisms use up oxygen, which means oxygen is removed from the water at a high rate

BOD

Acidity Most aquatic organisms prefer a neutral environment. As it increases, the diversity of plants and animals decreases. Most fish die if the water’s pH falls to 4.5.

Phosphorus and Nitrogen Fertilizers are applied to fields and gardens to supply plants with nutrients, such as the elements nitrogen and phosphorus. Water dissolves the fertilizer to provide nutrients to the plants Runoff from fields and gardens runs into streams causing algae to grow rapidly.

Phosphorus and Nitrogen Eutrophication is the addition of nutrients to an aquatic ecosystem causing increased growth of plants such as algae. As the algae dies and decomposes, oxygen is depleted from the water. The resulting low amount of oxygen in the water may cause fish and other animals to die.

Phosphorus and Nitrogen

Heavy Metals Some kinds of metals cause illness even in small amounts Heavy metals have a density of 5 g/mL or higher. Hg, Cu, Pb, Cd.

Heavy Metals Sources of heavy metals Batteries (Cd, Pb), compact fluorescent light bulbs (CFLs) (Hg) all coal-fired power plants, incinerators, and steel mills emit mercury from their smokestacks, because mercury is found naturally in coal. Mercury in the atmosphere usually settles in water.

Heavy metals Algae absorb very tiny amounts of mercury from the water and builds up in their tissues. Bioaccumulation - The gradual build-up of a substance in an organism’s body In a process called biomagnification, the mercury becomes more and more concentrated in each link in the food chain as one animal eats many contaminated animals

Heavy Metals Many predatory fish, including some salmon and trout, have high levels of mercury and should not eaten by humans and other animals. Health problems caused by heavy metals include: kidney and lung disease, immune system disorders, cancer, sterility in men, and infertility in women.

Bioaccumulation

Pesticides chemicals that kill unwanted organisms Some pesticides last a long time in the environment long-lasting pesticides can also biomagnify Example: DDT – accumulated in peregrine falcons and made their egg shells weak. Modern pesticides are designed to last one growing season and then break down into less harmful substances.

Homework / MSIP Read 52-57 Finish the Worksheet and hand in.