Dead Fish on Rickenbacker Lake
II. The Tutorial Storyboard:
D. Conclusion/Review
1. Testing Your Research Skills
Take a moment to use your favorite search engine to see if you can find out more about the dead fish. Try the following terms:
fish kill lake
You might also look at a couple of the sites that Julie and Mike found:
- Fish Kills: Their Causes and Prevention: http://www.ext.vt.edu/pubs/fisheries/420-252/420-252.html
- Common Causes of Fish Kills: http://www.broward.org/dni04900.htm
- Zoe Kersteen-Tucker. "Healthy Streams and Horsekeeping" http://www.greenfoothills.org/news/2001/05-2001_CleanStreams.html
2. What Julie and Mike Find Out
When Julie and Mike finish gathering information, they can expand their list of possible reasons for the dead fish on Rickenbacker Lake:
- Fish naturally die of old age, parasites, etc. A few dead fish floating on a lake or lake don't necessarily mean serious problems.
- Most fish kills result from natural events - usually too little oxygen in the water (hypoxia), often from algal blooms or overabundance of other aquatic plants.
- Weather may play a part, especially in hot weather when algae or other plants grow rapidly or extended cloudy periods when plants don't produce enough oxygen.
- Humans may influence the frequency and severity of hypoxia by increasing the nutrient levels in the water, particularly in developed areas. Nutrients may come from:
-
- Septic tanks
- Street and yard drainage
- Fertilizers from lawns, golf courses, and farms
- Feedlots and hog operations (manure)
- Fish are susceptible to a variety of poisons:
-
- Pesticide and herbicide runoff
- Industrial or other toxic runoff, including mining waste, gasoline, fuel oil and ammonia
- Deliberate poisoning by an number of means
- Virus or bacteria may attack fish (often in tandem with hypoxia or other events that stress fish)
Two of the newspaper articles mention fish kills from algal blooms in nearby reservoirs some years ago. Julie recalls that they'd experienced over a week very hot weather before they discovered the fish. Maybe it wasn't toxic waste or dynamite after all!
3. The Mystery…Solved!
Mike calls the local Fish & Game hotline and reports their suspicions. A biologist calls back a couple of days later to let them know they were right. The fish was a result of an algal bloom - a natural phenomenon - that occurred without any direct human cause. As they had discovered in their research, algae produce more oxygen than they use during daylight hours. At night during dark hours (and during extended periods of cloudy weather), they stop producing oxygen, but continue to use the oxygen dissolved in water for their respiration. Normally much more oxygen is produced in a period than is used by the algae in the same period.
During blooms, however, the algae populations get so high that the algae use more oxygen than they produce. The combination of an algal respiration and the respiration of the large numbers of fish reduce the dissolved oxygen in the water below the concentration needed for fish to survive.
4. Not Just the Hot Weather…
Humans probably had a hand in this particular fish kill, though - the biologist discovered a nearby stable had been cleaned out shortly beforehand. Unfortunately, some of the wastes were flushed into a small stream leading into Rickenbacker Lake, which gave the algae an extra boost of nutrients. The stable owners would probably be fined if water quality tests showed elevated nitrogen levels.
The biologist thanked Julie and Mike for their detective work and encouraged them to call again if they saw anything suspicious. She noted that even if we do properly manage nutrient input into the streams, blooms might still occur when conditions are right for algal growth contributing to more fish kills.
5. Resources: A Review
Now that we've solved the mystery of the dead fish, we're nearly done, but first, a quick review of resources...
[links to pages for review]
Resources In Acterra Library
- Books
- Periodicals
- Environmental impact reports
- Pamphlets and Newspaper Articles (Clippings files)
- Wildlife and Endangered Species Collection
- Videos
- Backpacking and Trails Collection
- Environmental Volunteers Collection
- Job Binders
Resources Elsewhere
- Internet
- Other Libraries
- Databases
- Informal Sources
- Primary Research
6. Evaluating Information: A Review
…And how to evaluate them.
[links to pages for review]
All Materials
- You may want to consider:
- Author
- Date of Publication
- Publisher
- Journal Title
- Intended Audience
- Bias
- Content
- Reviews
For research on the Web
Remember to think especially carefully about:
- Authority
- Content
- Currency
7. Thanks and Good Luck!
Thank you for taking the time to learn about resources in the Acterra Environmental Library and beyond. Now that you've completed the tutorial, you should be able to research your projects and evaluate your findings more effectively.
If you have any questions, you can look go back through any part of the tutorial (click on OUTLINE) or talk to one of the Acterra librarians. You may also wish to print out the Reference Guides (also available at the reference desk):
[links to PDF files]
Handout # 1: Resources for Environmental Research Available from Acterra Library and Elsewhere
Handout # 2: Types of Information: What Kind of Information Do You Need?
Handout # 3: Evaluating Your Information: All Information is NOT Created Equally
One last thing…
Before you go, please take a moment to fill out the tutorial evaluation [link]. We look forward to helping you find the answers to your environmental questions. Thanks and good luck!
[links]
- Acterra Library Home Page
- Map and Directions
And by the way, if you see an unusually number of dead fish floating on your favorite stream or lake, don't hesitate to call your local Calif. Dept. of Fish & Game hotline. [link]
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