The fluorescence line height and maximum chlorophyll index algorithms exploit the height of the measurement in a certain spectral band above a baseline, which passes through two other spectral bands.
The best known algorithm is the fluorescence line height, where the phytoplankton chlorophyll fluorescence at 680.5 nm is measured and its height above a baseline through the measurements at 664nm and 708nm is calculated.
This is used as an indicator for the biological activity of the phytoplankton.
Also, other band combinations provide important indices, e.g. such as the maximum chlorophyll index (bands 680.5, 708 and 753nm), which can be applied, for example, to MERIS L1b measurements which can indicate red tides.