Crucial in photosynthesis, it absorbs solar energy and allows its transformation into chemical energy. In the Oceans, the presence of chlorophyll is essentially due to phytoplankton. Marine phytoplankton plays a key role in the global climate system. Understanding its spatio-temporal variability by using chlorophyll-a concentration is an important goal of the present day oceanography. Consequently, chlorophyll-a concentration is an important proxy which is routinely measured in the Ocean and is also considered as a “core” parameter of global physical-biological oceanic models.

2) How is it measured ?

Several methods exist to determine the oceanic chlorophyll-a concentration :

> In situ (sensor): radiometry, fluorometry, spectrophotometry
> In vitro (in the lab), on discrete samples: HPLC analysis, spectrophotometry, fluorometry.
>  Space-based (satellite sensor): Ocean Color Radiometry, fluorometry

3) Where is more information available?

Xing et al. (2011). Combined processing and mutual interpretation of radiometry and fluorimetry from autonomous profiling Bio-Argo Floats. Cholorophyll a retrieval. Journal of Geophysical Research, doi:10.1029/2010JC006899. (pdf)

IOCCG (2011). Bio-Optical Sensors on Argo Floats. Claustre, H. (ed.), Reports of the International Ocean-Colour Coordinating Group, No. 11, IOCCG, Darthmouth, Canada.

O'Reilly, J.E., Maritorena, S., Siegel, D.A., O’Brien, M.C., Toole, D., Mitchell, B.G., et al. (2000). Ocean color chlorophyll a algorithms for SeaWiFS, OC2, and OC4: version 4. SeaWiFS postlaunch calibration and validation analyses, Part 3, NASA/TM 206892, Vol. 11, 9-23.

O'Reilly, J.E., Maritorena, S., Mitchell, B.G., Siegel, D.A., Carder, K.L., Garver, S.A., et al. (1998). Ocean color algorithms for SeaWiFS. Journal of Geophysical Research, 103, 24937-24953.

Jeffrey, S.W., Mantoura, R.F.C. & Wright, S.W. (eds, 1997). Phytoplankton pigments in oceanography. Monographs on oceanographic methodology, UNESCO, Paris.