Assessing Water Quality

1a. If an aquatic ecosystem is full of organisms, does that indicate a healthy or an unhealthy ecosystem? Increased biodiversity (many different types of living things) generally means a healthy ecosystem. If there is too many of one species (e.g. bacteria) that can be a sign of an unhealthy ecosystem

Aquatic biodiversity

1b. List the different types of living things that may be found in an aquatic ecosystem. Bacteria, insects and insect larvae, plankton, shrimp, clams and other shellfish, worms, amphibians, birds, fish, plants.

1c. What types of organisms can be measured to indicate that a water system is unsafe? Explain. Certain bacteria can cause serious health problems if present in large enough numbers (e.g. E. Coli). The presence or absence of some organisms can indicate that water is polluted. Indicator species include insect larvae, insects, shrimp, clams and worms. Some can live in polluted water, while others cannot.

Aquatic indicator species

2. How much oxygen must be dissolved in water in order to maintain a healthy, biologically diverse aquatic ecosystem? 8 mg/L of dissolved oxygen

2b. Define biological oxygen demand Biological Oxygen Demand – how quickly oxygen is used up by micro-organisms in a given body of water.

2c. How can b.o.d. be used to measure water pollution? Polluted water promotes the growth of some micro-organisms. They use up oxygen, which means that oxygen is used at a fast rate, which drives down the amount of dissolved oxygen available to other aquatic organisms

2d. Provide the b.o.d. for a healthy biologically diverse aquatic ecosystem. 8 – 20 mg/L

3. What happens to the diversity of living things in an aquatic ecosystem when the water becomes too acidic? Aquatic organisms prefer neutral environments. When acidity increases, biodiversity decreases.

4a. What is the main source of phosphorus and nitrogen pollution in aquatic ecosystems? Run-off of water from fields that have received fertilizers are the main source.

4b. Define eutrophication Eutrophication is the addition of nutrients to an aquatic ecosystems causing increased growth of plants such as algae.

4c. Outline the steps that result in eutrophication Nitrogen and phosphorus in surface run-off enters lake. Nutrients fertilize aquatic plants on the surface. Surface aquatic plants increase. Less light can penetrate the plants below the surface, so these plants die Decomposers fed on the dead plants, depleting the dissolved oxygen in the water Animals die from lack of oxygen Lake can only support surface aquatic plants and decomposers.

1999 algae bloom in the James River arm of Table Rock Lake (Missouri DNR photo)

5a. List some types of heavy metals that commonly pollute aquatic ecosystems and explain how they get into water. Heavy metals: mercury, copper, lead, cadmium Sources: batteries, compact fluorescent light bulbs, released from coal-fired power plants (mercury), incinerators and smoke stacks of steel mills

5b. What is the difference between bioaccumulation and biomagnification? Bioaccumulation is the build up of toxins in the body of an individual over time. It is generally due to repeated exposures. Biomagnification is the build up of toxins in individuals in a food chain. It results in the top consumers consuming and retaining the largest amounts of the toxin in their bodies.

6a. Explain the benefits of using DDT and the negative effects that the use of DDT had on the environment. Benefits – killed unwanted organisms , particularly mosquitoes in areas impacted greatly by malaria Negative effects – bioaccumulated and biomagnified to toxic levels in peregrine falcons and eagles, making eggshells so thin that few eggs hatched, and causing populations of these species to decline