Since there are only 3 sampling day (T1, T5 and T10), how do we calculate the growth rate using chl a biomass? Is it okay to use chl a instead of cell density?
not only "okay", it is your only option, even if you have a good regression equation, allowing you to calculate biomass or cell numbers, because chlorophylls are your primary data. so, you may calculate growth rates between times T0, T1, T5 and T10 (is day 1 the day of inoculum or the day after the culture was started? in the second case you may calculate growth rates between T0 and T1 (possibly lag phase), T1 and T5 (this probably represents exponential growth), and between T5 and T10 (slow growth to possibly stationary), while your regression will serve to estimate biomass and cell numbers with their confidence limits
Thanks for the quick reply. My mistake because I did not take the initial inoculation. Does that mean my data is still viable? Or do you suggest for the next experiment I have to take the initial inoculation?
you should always take the initial concentration (cells, chlorophyll, biomass, whatever you are interested in). As to your data, all data are viable. you only will miss the initial valu, which, depending on the species and strain, as well as on the age and condition of your inoculum, could have been part of the lag phase or the whole lag phase or even, provided yor inoculum was fully viable, part or all the exponebtial phase,
This you will learn growing your alga a few times, so that you will be confident about its growth characteristics. One observation though. the interval between samples seems too long. I would advise every day, at least until you are confident with thatparticular alga. if it seem too much work or too much material (filters, acetone and so on), take at least optical density readings,
write back if some doubts remain. take care
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