- Summarize the results of the carbon consumption experiment. I put a stock photo of a confused old lady in front of a computer because that’s how I feel trying to manage all the data in my mind. It’s hard to put into words what’s going on in an excel spreadsheet. Overall, the results between the sunny mesocosm and the forested pre-leaf fall were what I was expecting: that the two sources of carbon were consumed at similar rates. I was surprised to see that not a lot was going on in the James River, I thought we would see a higher rate of consumption there than we did. Still, the forested mesocosm had the highest average DOC consumed out of the three and it makes me excited to get to compare the post leaf down to them.
- Were your hypotheses supported or refuted? H1: There will be a greater loss of DOC in the forested post-leaf fall than the forested pre-leaf fall due to the fresh source of allochthonous carbon. Not sure yet! H2: There will be a moderate loss of DOC in the Sunny mesocosm due to a labile source of autochthonous carbon. I’m not sure if this one is supported or refuted, we might need to amend how it is written. But yes, the sunny shows more DOC consumed than the river and slightly less than the forested pre-leaf fall, I guess that is moderate or average. H3: The rate of consumption of DOC in the James River sample will be less than the forested mesocosms due to the natural system size and a mixture of both sources of carbon present in the sample. This one is supported by our results; the forested mesocosm pre-leaf fall had a much higher average DOC consumption. I’ve found some great studies on carbon in river systems that we can use in our paper to talk about the transport and settling of carbon.
- Explain the broader implications of these results. These results show that allochthonous sources and autochthonous sources are equally labile because there was no significant difference in DOC consumption between the sunny mesocosm and forested pre-leaf fall. However, the differences between the sunny and the river and the forested and the river show that systems can differ in bacteria and other organisms and this can make them cycle carbon differently. Like stated in our paper, the difference between the river and the forested mesocosm pre-leaf fall may be because of the transport of allochthonous carbon in the river system (Schlesinger and Melack, 1981). The James River may also have anthropogenic sources of carbon in it from agriculture or industry around Richmond, which our mesocosms wouldn’t (Billet et. al 1993). Based on these results, inland waters should be studied more because their carbon consumption differs, and if we want to know more about the transport and flux of carbon in inland waters we need to look at each system closer.
- How can you expand on this particular study in the future? In the future, I would expand our study by looking more at the James River. It would be interesting to compare bacteria in the mesocosms to the river. Rivers are such an important link in the carbon cycle. And the export of carbon for a river is correlated with its size, and watershed size (Schlesinger and Melack, 1981). I think looking closer at the James in a future study would be interesting because of the agriculture in Virginia that plays into its DOC amount, the James has a huge watershed and stretches across Virginia, and because the James is a part of the very large watershed that flows into the Chesapeake. The River Continuum Concept is also important when looking that the James, because where we sampled the river isn’t as narrow and the allochthonous sources aren’t dominating the space. Also, around Richmond the James does not have as many smaller streams and rivers feeding into it with their carbon. I think it would be really cool to design a study that looks at all the different stages of the James (or where it changes order) and what’s going on with the carbon in each area, in order to see how DOC levels and consumption might change with order or channel width. That would be my idea. To continue on seeing the difference in DOC consumption at the Rice Center, I would use all three mesocosms that are set up for more data.
Billet, M.F.; Cresser, M.S.; and D. Hope. 1993. A Review of the Export of Carbon in River Water: Fluxes and Processes. Environmental Pollution 84: 301-324.
Schlesinger, William H. and John M. Melack. 1981. Transport of Organic Carbon in the World’s Rivers. Tellus Series A: Dynamic Meteorology and Oceanography. 33(2): 172-187.