5 A Celtic Sea/ Bay of Biscay 



Patrick M. Holligan 



Marine Biological Association 

 Plymouth, United Kingdom 



and 



Michel Viollier 



Station d'Oc6anologie et de Biologic Marine 

 Roscoff, France 



Each year during the early summer, extensive patches of water giving 

 high reflectance of visible light are observed along the outer shelf margin 

 between 45° and 60° N. Observations taken at sea in 1982 established that 

 these are caused by coccolithophores; phytoplankton with external plates 

 or coccoliths of calcite, which become dominant after the main spring 

 diatom bloom has declined. These organisms, particularly the widespread 

 temperate species Emiliania huxleyi, are of particular importance in the 

 biogenic sedimentation of carbon (as calcite) in the oceans. The reflectance 

 of light by the coccoliths must be taken into account in the development of 

 accurate atmospheric correction and chlorophyll algorithms for the 

 processing of remotely sensed ocean color data. 



75 



