Science Buddies: "Ask an Expert"

I am doing a science fair project on bioremediation of oil in freshwater habitats.
My project is determining which bioremediation agent, MicroBlaze, DualZorb, or S200 OilGone, would be less toxic to small freshwater ecosystems.
I plan on having plastic tubs with water and aquatic plants (elodea), with and without oil. I will add the bioremediation agents separately to a tub and then measure the ph, dissolved oxygen and the TDS of each for a total of 5 days. The bioremediation agents are combinations of nutrients and bacteria, so the addition of the agents will have some affect on the water quality and the plant respiration. I am studying the effect on small freshwater systems, such as lakes and ponds, because they have less flow than saltwater and therefore, are prone to the detrimental effects of the agents.
I'm just wondering if I need to have specific types of bins (I currently have small bins that are 2 liter) and do i need to simulate water flow? And if so, how do I without affecting the dissolved oxygen levels? For example, if I use a air stone or air pump to simulate water flow, wouldn't that affect the dissolved oxygen levels?? Would just stirring the bins be sufficient?
Thanks!

This sounds like a very interesting project! To be honest, I don't know the specific answer to your question.

However I googled "do air stones affect dissolved oxygen' and came up with this website http://www.quickgrow.com/gardening_articles/index.html. It's geared towards people who do indoor gardening, but I think two of the articles might be helpful for you: 1-Oxygenation, Air Pumps, Nutrient Uptake and Temperatures and 2-Dissolved Oxygen Levels. The other articles there might be of interest to you as well.

Something else you could think about and depending on your budget and project time, you could consider using an air stone as an additional variable.

Good luck and let us know if you have more questions!
Nikki

Hi jneidha!

This sounds like a super interesting project. I just want to offer a couple of suggestions of things to keep in mind.

Freshwater systems (such as lakes) do have some natural water flow, which leads to mixing of the different water layers (oxygen rich upper layer, oxygen poor lower layers). One of the most important things about this mixing of the different layers of freshwater systems is that it prevents hypoxia from occurring, which are low levels of dissolved oxygen throughout the water column.

Now, I say this because of your concern with adding an air stone/oxygen for mixing the containers. If you leave the containers without any air flow or mixing, you could end up with water with low dissolved oxygen. Your Elodea will undergo respiration and release oxygen, but if your bioremediation agents contain bacteria/nutrients, they could consume a high level of oxygen in the water and leave it hypoxic over time.If you do end up adding air stones/oxygen to each container, I would recommend that you have at least one container without oxygen flow as a control.

Also, make sure that you keep a close watch on the temperature of each container, because dissolved oxygen concentration is significantly impacted by temperature.

Good luck with your project!