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Posted by Mercedes McKay on Wednesday, 18 November 1998, at 5:57 p.m., in response to Re: Wierd CO2 Readings, posted by Sophia from Fremont Intermediate on Monday, 16 November 1998, at 3:01 p.m.
Hi Sophia,
Thanks for sending me the additional information. A couple of things seem interesting about your data and observations. First, you said you found many macroinvertebrates which leads me to think that there are a number of organisms in your water that breathe in O2 and breathe out CO2 - so you may want to think about your theory a little more. However, I agree, it does seem very unusual that your readings for CO2 were 0 ppm when you would expect even a small concentration of CO2. C02 in the water can come from these macroinvertebrate or even from C02 in the atmosphere that dissolves in the water. It is very unusual not to find ANY in the water. This makes me wonder whether your C02 test kit was working properly.
I would recommend checking the C02 test again but I would do it on a water sample that you definitely know has C02 in it. This water sample could be from an aquarium or even a cup of water that you use a straw to blow bubbles in for a couple of minutes. Since humans exhale C02, if you blow bubbles into the water, you will be adding C02 to the water. You could then test the water sample and if it still shows as 0 ppm, then you would know that your test kit was faulty.
I also found it interesting that your dissolved oxygen levels were fairly high. High dissolved oxygen levels usually are an indicator of a healthy aquatic ecosystem, where you would find lots of fish and a variety of aquatic organisms including macroinvertebrate that are intolerant of pollution. Since you didn't notice any fish and only identified macroinvertebrate that were tolerant to pollution, I would say that the oil spill has definitely impacted your lake. It is hard for lakes to recover from an oil spill because bacteria in the water can't break down the oil and also because the water is very slow moving and can't purify itself easily.
You have picked a very interesting lake to test. There is a lot to think about! Let me know if you test you C02 kit out - I would like to know the results. Perhaps someone else involved in the project has some additional suggestions. Comments anyone???
Mercedes