Biology Lab write up
maaz_kadri
Lab11-PrelabDiscussion_DRAFT.ppt*
Lab #11 –
Ecotoxicology
Prelab Discussion
Today’s Lab Objectives
- 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 salinity.
- 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.
In Today’s Lab
Review of Ecosystem Basics
- Ecosystem:
- All of the interacting organisms (populations) and abiotic factors that occur in a particular place at a given time
- Components of an Ecosystem:
- Abiotic - nonliving components
- e.g. Sunlight, temperature, precipitation, soil/water chemistry
- Biotic - all the living things that affect an organism in its environment
- e.g. Organisms
Example of an Ecosystem
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Looking at the image below…
how would you define pollution?
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What is pollution?
- Definition –
- unnatural by-products of human activities accumulating in the environment at levels that are harmful to living organism.
- Sources of pollution vary
- Some specific types of pollution:
- Acid
- Organic
- Thermal
- Pharmaceutical
- Salinity
Acid Pollution
- Definition:
sulfur and nitrogen oxides react with air in the atmosphere (and potentially the terrestrially via run-off) to form sulfuric and nitric acids which will reenter the environment via rain.
- Acid pollution is extremely detrimental to all organisms (auto- or heterotrophic) in the environment
- Acid Rain is a prime example of Acid Pollution.
- Rainwater with a pH <5.6 = acidic.
- Side effect of air pollution from industry.
Basic Example of the
Creation of Acid Pollution
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Organic Pollution
- Definition:
compounds that are resistant to environmental degradation
Examples: Pesticides, fertilizers, detergents, sewage, farm run-off
- Organic pollutants can
- Be persistent in the environment for a long period of time
- They accumulate in human/animal tissues and magnify in food chains.
- a.k.a. They have significant impacts on human health and the environment as a whole.
- Are capable of long-range transport
- Can provide large quantities of of organic compounds and limiting nutrients, which act as substrates (food) for microorganisms, are released into water sources (algal blooms)
Examples of Organic Pollution
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Eutrophication
- The process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates.
- These typically promote excessive growth of algae.
- Algae die, decompose, increase organic material…therefore resulting in oxygen depletion.
The Process of Eutrophication
Bioaccumulation
accumulation of a chemical at a rate greater than that at which the substance is lost
obtained from external environment or food
Biomagnification
When accumulation of a chemical in an organism exceeds the background concentration of the substance in its diet
occurs at higher tropic level
Toxin Accumulation in Organisms
Add image
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Salt Pollution
- Salinity is a measurement of the concentration of dissolved salts in the water
- The salinity levels of our fresh water is increasing in many areas due to salt compounds used to remove snow and ice from roads.
- Increased salinity can also come from discharges from salt mines
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Ecotoxicology
- Ecotoxicology is the study of the effects of toxic chemicals on biological organisms and ecosystems.
- Multi-step process:
- The entry, distribution and fate of pollutants within the environment
- The entry and fate of pollutants in living (biota) organisms within an ecosystem
- The harmful effects of the chemical pollutants on the constituents (biotic & abiotic) of ecosystems (which include humans).
Understanding Ecotoxicology
- At organism level:
- Acute toxicity causing mortality (a.k.a. die right away)
- Chronically accumulation may cause death (a.k.a. die later)
- Impairment
- physiology & morphology
- behavioral effects
- Measurable biochemical changes
Ecotoxicology involves assessment of the impacts of contaminants at the organism level
- In species / population structure:
appearance/disappearance of an indicator species
number of individuals of a species
biomass of a species
presence or absence of a species
Ecotoxicology involves assessment of changes at the population level
Ecotoxicology involves assessment of changes at the ecosystem level
- changes in community/ecosystem structure
biomass & abundance
species diversity
food web complexity
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What is a bioassay?
- Definition – type of scientific study
- Typically conducted to measure the effects of a substance on a living organism.
- Essential in the development of new drugs and in monitoring environmental pollutants.
- Both are procedures by which the potency or nature of a substance is estimated by studying its effects on living matter.
What is an indicator organism?
- Definition:
- Indicator Organism: basic monitoring tool used to measure both changes in environmental water quality and conditions.
- Example:
- Daphnia – freshwater flea = EPA certified bio indicator organism
- Provides evidence of the presence of absence of a pathogenic organism that survives under similar physical, chemical and nutrient conditions.
Lethal Concentration
- In ecotoxicology, we report the lethal concentration, LC50 of a toxin, radiation, or pathogen
- This is the concentration required to kill half the indivudals of a tested population after a specified test duration.
- LC50 figures are frequently used as a general indicator of a substance's acute toxicity.
Observations
- Impact of pollutants on freshwater ecosystems is not always straightforward
- Changes in the surrounding ecosystems with seasons and anthropogenic disturbances are not all predictable
- Identifying the pollutant can help with predictions of community and population changes
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Observations
- Look at the pictures on the following slides
- Flasks were set up with ~400 mL of the same pond water
- Pollutants (the same as in the Daphnia bioassay) were added
- Flasks were allowed to sit undisturbed for 5 days
- Consider the questions …
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Pollutants added to pond water
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Why does the fertilizer runoff sample have so much more algae present?
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Note the color differences in the algae.
What do you think that indicates?
Remember – algae are photosynthetic unicellular plants!
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Acid Rain
No runoff
Daphnia Bioassay - Setup
- Test species
- Daphnia pulex
- Daphnia magna
- Synthetic Freshwater* (EPA Standard)
- Selenastrum capricornutum (green algae food for Daphnia)
- Pollutants
- sodium phosphate (organic pollution) – 3 levels
- hydrogen chloride and sodium hydroxide (pH pollution) – 3 levels
- potassium chloride (salt pollution) – 3 levels
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Pollutant Treatment Levels
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| Pollutant | Treatment Level 1 | Treatment Level 2 | Treatment Level 3 |
| Organic (Na3PO4) | 0% | 0.01% | 0.04% |
| pH (HCl and NaOH) | 4 | 7 | 10 |
| Salt (KCl) | 0% | 0.01% | 0.04% |
Setup Procedure
- Sort Daphnia selecting individuals of similar age
- In a 30 mL scintillation vial, add Daphnia to 20 mL of synthetic freshwater + treatment level
- 9 Daphnia per treatment level (unless otherwise noted)
- Feed Daphnia 0.5 mL Selenastrum algae food every 24 hours
- Count and record Daphnia survival every 24 hours for 7 days
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Typical Setup – Sorting Daphnia
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Daphnia in Treatments
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Daphnia in Treatments
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Three Daphnia magna in a 0% KCl treatment vial
DAPHNIA SURVIVAL
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Daphnia pulex – Organic
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Note: an acute test of 1% and 4% Na3PO4 showed 0% survival at 24 hours
| Trt Level | Day 0 | Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6 | Day 7 |
| 0% Na3PO4 | 9 | 9 | 9 | 9 | 9 | 9 | 8 | 8 |
| 0.01% Na3PO4 | 9 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| 0.04% Na3PO4 | 9 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Daphnia pulex – Salt
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Note: an acute test of 1% and 4% KCl showed 0% survival at 24 hours
| Trt Level | Day 0 | Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6 | Day 7 |
| 0% KCl | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 |
| 0.01% KCl | 9 | 4 | 3 | 3 | 3 | 3 | 3 | 2 |
| 0.04% KCl | 9 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Daphnia pulex - pH
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| Trt Level | Day 0 | Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6 | Day 7 |
| pH 4 | 9 | 9 | 9 | 7 | 7 | 7 | 7 | 7 |
| pH 7 | 9 | 9 | 9 | 9 | 9 | 9 | 8 | 8 |
| pH 10 | 9 | 8 | 8 | 8 | 8 | 8 | 8 | 8 |
Daphnia magna – Organic
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Note: an acute test of 1% and 4% Na3PO4 showed 0% survival at 24 hours
| Trt Level | Day 0 | Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6 | Day 7 |
| 0% Na3PO4 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 |
| 0.01% Na3PO4 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 |
| 0.04% Na3PO4 | 9 | 9 | 6 | 2 | 2 | 1 | 1 | 1 |
Daphnia magna – Salt
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Note: an acute test of 1% and 4% KCl showed 0% survival at 24 hours
| Trt Level | Day 0 | Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6 | Day 7 |
| 0% KCl | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 |
| 0.01% KCl | 9 | 5 | 2 | 2 | 2 | 2 | 2 | 2 |
| 0.04% KCl | 9 | 2 | 2 | 0 | 0 | 0 | 0 | 0 |
Daphnia magna - pH
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NOTE: there are 6 Daphnia magna per treatment for pH
| Trt Level | Day 0 | Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6 | Day 7 |
| pH 4 | 6 | 5 | 5 | 5 | 5 | 5 | 5 | 5 |
| pH 7 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| pH 10 | 6 | 6 | 6 | 5 | 5 | 5 | 5 | 5 |
How do you plot these data?
- Calculate the percent survival at the end of the experiment for each species in each treatment
- End survival count / initial count * 100
- Plot the concentrations of your treatment on the X-axis, and your survivals on the Y-axis
- In your report you will plot two species on each graph – and there will only be two lines on the graph (one for each species)
- You can estimate LC50 from this curve
- See the example on the next slide
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Example LC50 Plot
Trial N=5
kj N=9
S. Connelly and K. Walling, RIT
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Writing your lab report
- Please see the Lab Report Assignment for details on what the report should include!
- This lab report is due by 11:59 pm on Monday, April 27th in the assignment dropbox on MyCourses
- Don’t forget to complete Quiz # 9: Population Ecology by 11:59 pm on Sunday, April 26th
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