#1.With the use of examples, describe the difference between biodegradable and non-biodegradable substances.

Transcription

1 EXERCISE #6 LESSON SIX - ANSWERS #1.With the use of examples, describe the difference between biodegradable and non-biodegradable substances. Biodegradable substances such as dead plants, dead animals, and sewage naturally break down over time in the environment. Non-biodegradable substances such as DDT, mercury, glass and some plastics persist in the environment over long periods of time. 1

2 #2. Refer back to the Lake Winnipeg food web in Lesson 2 (page 10). Toxins are released into Lake Winnipeg and are absorbed by the algae and passed up the food chain. A) As a person who lives on fish caught in Lake Winnipeg, which fish should you eat? B) Which fish should you avoid? Why? The fish that are eaten should be ones that are not part of the food chain involving algae. In this food web, it would be safe to eat walleye and sturgeon. Secondly, fish that are part of a food chain with algae in it but are low in the chain would have less of the toxin accumulated in them. These would be catfish rather than whitefish or northern pike. Thirdly, if you were to catch only northern pike which are near the top of the chain, smaller, younger fish would contain less toxin than older fish which have been accumulating the toxin over a longer period of time. #3. What are some of the possible dangers of eating a lot of fish that contain high levels of mercury? People develop serious disorders of the brain and nervous system if they consume mercury. Symptoms of mercury poisoning include tremors, dizziness, joint stiffness and pain, as well as memory loss and mental decline. People may even die from mercury poisoning after eating contaminated fish. 2

3 EXERCISE #7 LESSON SEVEN - ANSWERS #1. How does the consumption of mercury affect humans? People develop serious disorders of the brain and nervous system if they consume mercury. Symptoms of mercury poisoning include tremors, dizziness, joint stiffness and pain, as well as memory loss and mental decline. People may even die from mercury poisoning after eating contaminated fish. 3

4 #2. What are the causes of increased mercury levels in fish found in some of Manitoba s lakes and rivers? Mercury contamination was attributed mainly to discharges from some pulp and paper mills prior to the 1970 s. Increased mercury levels were also discovered in fish from lakes flooded by the Churchill River hydroelectric dams in northern Manitoba during the late 1970s and early 1980s. In the newly flooded land, bacteria altered the form of naturally occurring mercury, making it more readily takenup by fish and other aquatic organisms #3. Predict the economic impact of mercury contamination on Manitoba s fishing and tourism industries Mercury contamination led to the closure of commercial fishing on the Saskatchewan River in Manitoba, including Cedar Lake. Communities would have been severely impacted when fishery workers lost their jobs. Tourism may also be affected as fish consumption guidelines limit the amount of fish one should eat from certain bodies of water. Fishing lodges, outfitters and guides may have seen a decline in their business. 4

5 #4. How can you reduce the risk of mercury poisoning to you and others? Limit your use of pesticides as much as possible. Follow the label instructions carefully and dispose of used containers in a safe manner. Do not flush chemicals down sinks or storm drains. Take unwanted or unused chemicals to a hazardous waste disposal facility. When fishing in Manitoba, refer to the sport fish consumption guide to determine which species are restricted for eating due to mercury. Those fish not recommended for consumption should be released unharmed. 5