Sealed Mesocosm (Ex)

IB Practical 5: Setting up a sealed mesocosm to try to establish sustainability

Read page 212 in the Oxford textbook and page 183 in the Pearson textbook.

Understanding nutrient cycling

Essential idea: sustainable ecosystems need a continuous supply of energy, but in a closed ecosystem, nutrients are recycled. The practical activity is meant to ensure that the researcher controls the loss of matter from the system. The two most common approaches to this would be a sealed terrarium or a Winogradsky column.

In a closed ecosystem light energy can enter and heat energy can escape but matter must cycle to sustain life inside. Different mesocosms can be exposed to different light levels and the impact on the systems can be compared.

Mesocosm poster: experimental design

Design: make a detailed drawing the mesocosm that you would build. Pay attention to the relative sizes of each biotic and abiotic component. All components of of the mesocosm should be correctly labeled.
Materials: state the biotic and abiotic factors that you would include in your mesocosm. Consider significant factors that may affect the ecosystem and provide specific quantities of each factor (carefully consider light intensity). Name each living organism with their scientific name (binomial nomenclature). Identify the the trophic level and role of each biotic factor in the functioning of the mesocosm ecosystem, providing as much detail as possible. Show evidence of your background information research. The background information provided for the investigation must be entirely appropriate and relevant to enhance the understanding of the context of the investigation.
Experimental data. Describe the quantitative and the qualitative data that you would collect during the course of the mesocosm experiment.
Predict the changes in the mesocosm after 3 days, 10 days, and 25 days. Include a clear statement of what you predict will occur in the mesocosm along with an explanation of why you have made those predictions. Present a careful predicted analysis of the change over time in your mesocosm.

Your drawing and all of the required information above must fit on an A3 paper (back and front is OK).

Virtual Mesocosm Lab

Use this simulation to understand what are the elements of a sustainable ecosystem.

Ideas

Mesocosms have been used in research to test the effects of herbicides and other pesticides, to evaluate climate change effects and for many other purposes. Aquatic mesocosms seem particularly common.

Using the bottles above it is possible to design a long term investigation.

Here are some ideas.

Make identical mesocosms and put them in positions with varying conditions,
1. Increasing light levels. Is there an optimum light level?
2. Increasing temperatures. If there is more condensation - like rain clouds do the plants grow better?
3. Movement, tip or shake the bottles to see the effect of water movement.
4. Connect a data logger to a mesocosm, or build the mesocosm in the data logger chamber.
Make a range of mesocosms and change one component as an independent variable.
1. Put increasing amounts of plant material in, and record the longevity of the mesocosm
2. Add more and more water to each mesocosm, is there a minimum amount needed.
3. Add more species of plant, or more species of animals.
4. Add some rotting compost to the soil. Watch to see the emergence of fruit flies or the presence of maggots
5. Connect the water section to the plant section with string, or a piece of wood.
6. Mix seeds with the soil, with different amounts in each bottle.
7. Add an increasing amount of sediment / sand into the water.
Measurement that may be possible
1. Test the water for pH or nitrates at the beginning and the end of the experiment.
2. Measure the mass of plants at the beginning and end.
3. Count the leaves, or the number of animals.

Rubric_Mesocosm.pdf

Make your own ecosystem

A great way to learn about and study ecosystems is to make your own. Have a look at the videos and resources here.

PROBLEM SOLVING IDEAS

YOUR SELF-CONTAINED BIOSPHERE

Winogradsky columns

Great video of an experiment with Winogradsky columns with different starting contents. A timelapse camera is used to record the columns for over 20 days. In the video, 1 second equals 1 day with pictures every three hours. Two columns received added sulfur (in the form of an egg yolk) to promote the growth of microorganisms that participate in the sulfur biogeochemical cycle. For example, purple sulfur bacteria are phototrophs that use sulfide as an electron source instead of water (thus they do not produce oxygen). If you use marine sediment and water then you don't need to add sulfur. See here.