Bio-optical data and ocean colour
The colour of the ocean as “seen” from a satellite is related to the light absorbed and scattered by substances and organisms in the water. Once of the most important parameters that influences the colour of the ocean is phytoplankton, tiny plants which contain the green pigment, chlorophyll. Although microscopic, phytoplankton grow in such numbers that they can change the colour of the ocean to such a degree that it can be seen from space. Satellites measurements can then be used to estimate the number and types of plankton from how the light is scattered.
Phytoplankton are an important component of the oceanic carbon cycle. Yet, due to methodological constraints, the carbon biomass of phytoplankton is poorly characterised. To address this limitation, AMT scientists have explored the bio-optical relationship between in situ measurements of the particle backscattering coefficient at 470 nm, bbp(470), and the phytoplankton carbon concentration for cells with diameter less than 20μm (Cf). A significant relationship was found between bbp(470) and Cf for Atlantic oceanic waters with chlorophyll-a concentrations less than 0.4 mg m-3 (or bbp(470) < 0.003 m-1). This relationship could be used to estimate Cf from data collected by in situ autonomous platforms and from remote sensing of ocean colour.
The results of recent research (Martinez-Vicente et al.) demonstrated (for the first time from in situ data) a relationship between the phytoplankton carbon (derived from AMT flow cytometry) and how the light is scattered in a backward direction (optical backscattering; Figure 1 and Figure 2).
Martinez-Vicente V., Dall’Olmo G., Tarran G., Boss E. and Sathyendranath S., Optical backscattering is correlated with phytoplankton carbon across the Atlantic Ocean. (2013), Geophysical Research Letters. DOI: 10.1002/grl.50252
Dr Victor Martinez-Vicente