Why do you assume there is a time lag?

Are you working with satellite data or in situ profiles?

I use satellite imagery data from MODIS-AQUA

I thoufh because of the cycle of phytoplankton, we cannot just say that if the Chla is high at one moment, the biomass is high at this one moment. There might be a temporal period of assimilation of phytoplankton by krill and then higher trophic organisms... Or am I thinking wrong?

Well, in your initial question you asked about the estimation of primary productivity from chl-a, and this should be tightly coupled. In fact, you can obtain the product (PP from MODIS-AQUA) here: https://www.science.oregonstate.edu/ocean.productivity/.

However, If you target biomass, which one are you interested in? POC concentration? Zooplankton biomass?

Sorry, I may have been confused, I wanted to assess biomass of krill (Euphausiids), using Chla and/or PP as proxy.

Thanks for the link, I read indeed that the NASA made up an algorithm to astimate PP, but I coulnd not find available data.

Hi Laëtitia, I don't think there is a straightforward empirical relationship. Apart from the time lag you mentioned there will be impacts of the community composition both on the phytoplankton side and on the consumer side (e.g. krill vs. salps vs. copepods), so a food web model of some complexity would be needed. Are you planning to do this from scratch (predict krill from PP) or are you gathering available krill biomass distribution data to try to relate it to the satellite-derived PP (minus some time lag)? By the way, I am not an expert in Southern Ocean ecology, somehow I just ran across your question and was curious :-)

Hi,

I thought that a high Chla i.e. PP level would mean high biomass (with respect to the consumption /growth lag and current displacement) as it is the basis food resource...

I don't neek an exacte estimation of krill biomass, just to determine the areas of greater biomass, and try to relate it to animal foraging activity.

I see... do you know this paper? Article Growth limitation in young Euphusia superba under field conditions

nice, I will have a look, thanks a lot!

This paper is brilliant, thank you very much!!