Name: ___________________________ General Biology II Lab

LAB #11: Ecotoxicology Lab Report


 To apply your knowledge of ecosystems, population ecology, and ecotoxicology to a case study of the impact of pollution on Daphnia populations and what that might indicate for ecosystems as a whole.

· To learn more about the sources and impacts of pollutants on the dynamics of aquatic ecosystems, particularly the impacts of organic pollution, acid pollution, and salt pollution.

· To learn more about the use of indicator species and to understand why Daphnia are used as such a species.

· Understand what lethal dose/concentration means and how it is specific for each pollutant type.

· To practice using credible sources on (at least 2 peer-reviewed) to support your arguments.

· Synthesize this information into a final lab report.

The Scenario

You have been hired as a summer research assistant for the New York State Department of Environmental Conservation (DEC). A former research assistant left some data from a past project that was never analyzed. Your supervisor wants you to analyze the data and write a report on your interpretations of the data. You have been provided the data and images in the Prelab PowerPoint. It is your job to statistically analyze the data, research ecotoxicology, the role of indicator species, and sources of population in freshwater systems, and to compile this in to a report for your supervisor.

You know that this former research assistant was comparing the survival of Daphnia in three different types of pollutants that are commonly found in the environment: organic pollution, pH pollution, and salt pollution. The former assistant set up bioassays of various concentrations of each type of pollution using specific chemicals to represent environmental pollution: sodium phosphate (organic pollution), hydrogen chloride and sodium hydroxide (pH pollution), and potassium chloride (salt pollution). You know that these chemicals are representatives of pollutants in the environment but you do not know what potential sources of these chemicals in nature would be. This is something you will have to research. Where is organic pollution, pH pollution, and salt pollution commonly found in nature – and what is the potential source of the pollutants? No, you should not assume that someone dumped the chemicals directly in a pond on purpose.

Daphnia are freshwater microcrustaceans. In the research assistant’s notebook, you found that they used Daphnia pulex and Daphnia magna. You assume that the species must be important, but at first you are not sure why Daphnia were even used. After a little research you learned that Daphnia are sensitive to the effects of pollution and are considered an indicator species. You note that indicator species, or bioindicators, are animals or plants that are used to infer conditions in a given habitat, and their presence / absence can be compared across ecosystems to understand the health of the environment. With a little more digging, you find that the Environmental Protection Agency has published protocols that describe methods of using Daphnia species to monitor toxic substances in water (EPA 2008).

Now that you understand what an indicator species is, you need to figure out why the research assistant used two different species of Daphnia – Daphnia pulex and Daphnia magna. You will need to do a little research to better understand the life-history of each species. In addition to comparing physical differences, think about the differences in habitats, diet, predators, and how they differ in terms of sensitivities to pollution. You also may want to consider why it is a good idea to compare two different species of Daphnia.

Your supervisor tells you that you will need to determine the lethal concentration of each pollutant type for each species of Daphnia. You know from your General Biology Lab course that the median lethal concentration is the concentration of a toxin, radiation, or pathogen is the dose required to kill half the members of a tested population after a specified test durationThis can be abbreviated as LC50 (abbreviation for “lethal concentration, 50%”).

Your job is to analyze the Daphnia data and determine the LC50 for each pollutant type and each species. Your supervisor would like this written up as a final lab report with graphs and background information on why these pollutants would have been found in the environment (i.e. what would be a source of this type of pollutant?). Your supervisor would also like you to suggest possible recommendations for reducing the presence of these pollutants in the natural environment.

The Assignment

Synthesize the data to create a lab report. Your lab report should include the following:

1. Introduction Section

This will provide background on the topic of pollution and the use of Daphnia as an indicator species. You should define each type of pollution and you should incorporate a suggestion of a source for each of the three types of pollutants discussed in this experiment (organic, pH, and salt). This should also include a brief comparison of the two species of Daphnia (habitats where they are typically found and relative sensitivities to pollution).

2. Results Section

In the results section, you need to present the data that was provided to you from the research assistants notebook. This is not a discussion or interpretation of the data, but simply a presentation of the data with only limited text to support that presentation. What is important for the reader to look at in your data? You have been given survival data of the two Daphnia species over 7 days for the three pollutants. You need to analyze those data and determine what the percent survival is of each species at each concentration of pollutant. You should include these percent survival data in a clearly written text paragraph at the beginning of your results section.

Now, using the percent survival data that you calculated, you will produce three graphs and one table for this report. To report the ecotoxicology data, you should make three LC50 graphs in ExcelTM or other data graphing program, which will highlight the survival of the Daphnia for all three types of pollutions tested (organic, pH, and salt). Please note, the two species of Daphnia should be graphed on the same graph for comparison for each pollutant type. For example, one of your graphs should represent the organic pollution data on which you plot concentration on the x-axis (% Na3PO4), survival on the y-axis (as a percentage at Day 7), and the survival of each species of Daphnia as the plot lines. Do not forget these graphs are figures and need titles and figure legends (below the figure!).

Now use your three graphs to determine the LC50 for each species and each pollutantMake one table of LC50 values for each pollutant and each species of Daphnia that you have calculated from your graphs. By generating a clear table here, properly formatted and including a table title and description (above the table!), your discussion / conclusion will be easier to formulate.

3. Conclusions section

A. Interpretation of Daphnia data:

i. In this section you will interpret your results for the Daphnia. Using your data that you presented in the results section, and your reliable research (peer-reviewed scientific articles), discuss whether or not the results recorded by the former research assistant make sense to you. Does anything seem strange to you in the data interpretation – or does the data match what you found in the literature? Explain why and present your interpretation of why any differences might have been observed.

ii. Based on what you know about Daphnia as an indicator species, discuss the implications of these types of pollutants on aquatic ecosystems.

B. Proposed Solutions:

i. You should also think about what can be done to mitigate the impacts of these types of pollutants on natural environments. Propose specific solutions for each type of pollutant and be sure to back up your claims with referenced examples.

4. References

You will also need to have a reference section with at least five sources (two of these sources must be peer-reviewed…ALL of the sources should be credible; Format with APA formatting and be sure to include in-text citations with an (author last name, date) format ( .

Formatting and Submission

1. Paper formatting

2-3 pages, 1.5 spaced, 1” margins, 12 pt. font

2. File submission:

· File should be submitted as a PDF file to the designated Assignment Folder on MyCourses by 11:59 pm on Monday, April 27, 2020.

i. Your submission files must be named and uploaded as follows: Last name_First name_lab section

ii. Late Submissions: Late assignments will be accepted only in the Assignment Folder on MyCourses up to 5 days late (no later than May 2, 2020). All late submission will be penalized 10% per day.

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