I'm new to calculating GPP/CR from diel oxygen curves, and have been getting negative GPPs and I am trying to figure out what this means. I know one large source of error is the reaeration coefficient. I understand there are lots of opinions about estimating reaeration coefficients- we cannot afford to do injection tests. So, I have been getting the coefficients by looking at the slope between DO deficit and DO change per hour at night based off our understanding of Heffernan and Cohen 2010/Owens 1974. The resulting coefficients are reasonable- 5 to 20 day-1. But, continuing the one-station calculations results in negative GPPs. I have noticed that, despite having a clear diel curve, our streams are almost consistently undersaturated in DO- would that be the reason I am getting negative GPPs? I am looking for advice on interpretation or different methods to try!
Hi,
To best answer the question, you need to give more information, what is the model that you used for the calculations? what is the method you used for calculating the reaeration coefficient? also did you use one station or two stations.
Karoline
If you have a negative coefficient (probably due to low DO), you will have negative GPP. I'd recommend the following two articles:
https://www.researchgate.net/publication/277541474_Effects_of_Timber_Harvesting_with_Best_Management_Practices_on_Ecosystem_Metabolism_of_a_Low_Gradient_Stream_on_the_United_States_Gulf_Coastal_Plain
https://www.researchgate.net/publication/304580059_A_Deterministic_Model_for_Predicting_Hourly_Dissolved_Oxygen_Change_Development_and_Application_to_a_Shallow_Eutrophic_Lake?_iepl%5BviewId%5D=9VGHJ0VPTsptUz2gV5s0oJad&_iepl%5BprofilePublicationItemVariant%5D=default&_iepl%5Bcontexts%5D%5B0%5D=prfpi&_iepl%5BtargetEntityId%5D=PB%3A304580059&_iepl%5BinteractionType%5D=publicationTitle
Article Effects of Timber Harvesting with Best Management Practices ...
Article A Deterministic Model for Predicting Hourly Dissolved Oxygen...
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