Mesocosm lab PDF

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Mesocosm lab...

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Mesocosm Lab Objective: To create, design, and monitor a mesocosm that is able to sustain life (monitored for a period of 4 weeks). Materials The Bottles 4 2L plastic bottles Scissors Permanent marker Large rubber band Plastic saran wrap Data collection table (notebook or digital) ● Camera ● ● ● ● ● ●

Ingredients Mud Shovel and bucket (to carry mud) Water (from mud source or tap) Pitcher or small plastic bottle (to carry water) ● Spoon and 2 mixing bowls ● 4 egg yolks (raw/hard boiled) ● Newspaper clippings, shredded ● ● ● ●

Procedure 1. Empty and rinse the 4 2L bottles. Peel off the labels. Cut off the curved top. These will serve as terrariums and will be the foundation of the ecosystem you are looking to create. 2. Draw 2 short lines on the bottle: one about a quarter from the bottom of the bottle and one about a quarter from the top of the bottle. 3. Dig up mud (which is full of microbes) and fill the bucket with enough mud to fill the 4 bottles to about ¾ full. 4. Remove rocks, twigs, and other solid matter. 5. Collect water from the mud source. Fill the bottle. 6. Cut the newspaper clippings into tiny rectangles. This provides carbon for the microbes. 7. Put the mud into a large mixing bowl and add water until the consistency becomes that of a milkshake. 8. Transfer ¼ of the mud into the medium mixing bowl. Stir in the yolk. 9. Spoon the mixture into the 4 2L bottles, filling to the first line that you drew. 10. In 3 of the bottles, add in a handful of newspaper shreddings and mix. The one that only has the yolk will be testing the impact of nutrients on the growth of bacteria. 11. Tap the bottles to remove any air pockets and allow the mud to settle to the bottom. 12. Spoon the regular mud mixture into all 4 2L bottles up to the second drawn line. Gently tap again to remove air pockets.

13. Top all bottles with your remaining pond water, leaving about an inch from the top empty. 14. Cover the bottles with plastic saran wrap and secure them with a rubber band. 15. Keep the bottle with only egg, as well as one of the other bottles, in an area that receives sunlight throughout the day. These bottles will be testing the impact of nutrients on the ecosystem. 16. Keep one bottle under a lamp, making sure that the lamp is constantly turned on. Let others know about your experiment and ask them not to tamper with it. 17. Keep the last bottle in a cupboard, where no light appears. These two bottles will be testing the impact of light. 18. Over the next 4 weeks, watch for various color layers to form as microbes separate into their natural habitats. 19. Once a week, on the same day at the same time, take note on your observations on any changes that occur, including colour, movement or thickening of sediment, and differences between each bottle. Results

2 weeks into the experiment, this is one of the bottles that tested for sunlight. It was placed under a lamp for the entire period of time and was given the same nutrients as the other one in its group testing sunlight impact on bacterial growth. This bottle had the most dramatic growth, as the cyanobacteria on top was thriving and became greener and greener over the course of the experiment. However, there were no other layers that became prominent.

Top Left: 2 weeks into the experiment, this is one of the two bottles testing for nutrients. It was left where sunlight could reach it and the mixture included both newspaper and egg. There was some cyanobacteria growing at the top, where oxygen levels are highest. The microbes that grew here use oxygen and not sulphur. There was evidence of non-sulphur bacteria (purple, orange, red, brown in the middle), as well as sulphur reducing bacteria (black at the bottom). The layers, however, were difficult to distinguish between and the line was quite blurred. Top Right: 2 weeks into the experiment, this was the other bottle testing for nutrients. It was placed in the same place, but the mixture contained only egg and no newspaper. There was no cyanobacteria on top (green) but there was non-sulphur bacteria in the middle and sulphur reducing bacteria at the bottom. This is where sulphur levels are highest. The separation between layers was difficult to distinguish due to human error, which will be discussed in the conclusion. Bottom Left: 2 weeks into the experiment, this was one of the two bottles testing for sunlight availability. This one was left in the cupboard, where no sunlight could reach it. It had the same nutrients (newspaper and egg) as the other one in its group. There was no evidence of bacterial growth.

Conclusion This experiment was conducted with an abundance of errors that skewed the results. While combining the ingredients, we ended up mixing both the regular mud and the mud mixture together rather than leaving them separate. This is because when we collected the mud, we did not use a bucket to carry enough mud for the 4 bottles, but instead we filled them with the regular mud ¾ of the way. Due to first mistake, we failed to create the milkshake like consistency that the methodology calls for and we were not successful in creating the “layers” in the bottle. This could have created massive problems that did not allow the bacteria to grow and thrive. Over the course of the 4 weeks, we noticed that our mesocosm was not making nearly as much progress as other groups’ and the only one that underwent a very prominent change was the bottle positioned under the lamp, most likely due to the abundance of heat provided; this is the perfect condition for bacteria to grow in. The plastic bottles did not work as well as sealed glass jars would have. The choice of transparent bottles was good because it allowed sunlight to penetrate it, but overtime, the bottles began to expand and the rubber bands slipped off, and thus the bottles were not properly sealed. This means that each bottle was likely exposed to more or less oxygen than its counterparts, which could have been avoided by using sealed glass jars. It is then difficult for us to conclude whether it is the oxygen, nutrients, or availability of light that allowed/did not allow the mesocosm to sustain itself. Our observation times were not consistent, meaning that is it difficult for us to understand the rate at which our bacteria grew and the rate of

change. Next time the experiment is conducted, we should be observing the mesocosms consistently, noting down the date and time at which each observation was made. It would also be helpful to start the experiment earlier to give the bacteria more time to change, giving us more data to analyze. While this lab was not quite successful in the sense of properly carrying it out, we were still able to produce some results, while also acknowledging our mistakes to amend in the coming labs. These mistakes would be incredibly important to take into account if we were to conduct this experiment again, as it had a massive impact on the results. The experiment did yield some results, with the bottle placed under the lamp and the bottle with both eggs and newspaper nutrients being the most effective in its respective group. The bottle under the lamp produced a vast abundance of cyanobacteria, despite not having other layers. This was most likely due to human flaw and if we were able to conduct the experiment properly next time, the layers would probably be more distinguishable. The bottle with both eggs and newspaper did grow some cyanobacteria, but it also did not have much distinction between layers. The other two in both the fields did not show much bacterial growth at all. With this, we have concluded that sunlight and nutrient availability have a significant impact on bacterial growth. The two that received little to none of either of the two ended up having no drastic change in bacterial growth....