I want to compare each communities' respiration (as measured in-situ in benthic chambers), per gram organic biomass. The problem is that biomass is order of magnitude different between communities and variations in biomass are much larger than variations in respiration between communities.
i.e. when subtracting a number by a large value = small value; when subtracting a small value = large value.
If I could, I would have done a controlled lab experiment using the same amount of biomass from each community and get rid of that artifact.
My question is:
Can I transform the biomass values in order to minimize variation between communities and - artifact? I don't care much about the actual values - I would just like to compare between them (which respires the most/least per gram organic biomass?)
also, which transformation should be used?: respiration is measured by the change in DIC concentration over time in side incubation chambers.
I expect that production of DIC over time will increase with increasing organic biomass inside the chamber, however I'm not sure how these variables behave. I expect it not to be linear. Possibly logarithmic, however I can't really do a manipulative experiment to check that.
Is anyone familiar with a study that used this kind of normalization using transformed data? Who can I cite?
Thanks!
I do not understand well your question. Why do you subtract values? The property of the community and the values that you should compare, in my opinion, should be ratios: for example, Production/Biomass or, as in your case, Respiration/Biomass. This ratio should be quite in the same range of values (independently of the total biomass of each community) and will depend of how much accelerated will be the metabolism of the community (depending on the temperature and stress). I am not expert in the topic, but in general terms Production/biomass will be a good indicator of the stage in the succession of the community. However, respiration/biomass is probably more independent of succession and more related to the stress level, latitude and temperature.
I'm also having a difficult time understanding the exact issue...I would have thought that you just standardize respiration rates by algal biomass, then biomass (alone) is accounted for. How are you measuring respiration? Via direct measurement of DIC, only? By comparing DIC levels to O2 evolution in light & dark?
There will, of course, be DIC in the seawater before the plant uses/respires it. How will you tell what proportion of the DIC is independent of the seaweeds/invertebrates (e.g. those will be respiring CO2...but some of this CO2 will be naturally converted into HCO3- via equilibrium 'rules' with those two DIC sources and pH).
Sorry, not overly helpful at the moment. :)
