1) What is it and why is it important to measure?

Chlorophyll-a is a green pigment that is found in most plants. 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.