Linking Functional Genes and Satellite-derived Optical Signatures of Marine Autotrophic Biodiversity

Species composition of phytoplankton modulates the spectral characteristics of the underwater light field by absorbing visible light, which determines ocean colour, which is now routinely captured by satellite remote sensing. The emergence of ocean colour depends on the absorption spectra of phytoplankton, which depends on their taxonomy, pigment composition within cells and cell size. At the molecular level, the physiological features are controlled by phytoplankton genetics. Ocean colour can operationally provide estimates of phytoplankton biomass in terms of chlorophyll concentration and, through recent advanced algorithm developments, can provide quantitative information on chlorophyll and carbon fractions in different phytoplankton size classes or functional types. But it has not yet been possible to link the underlying phytoplankton genetics to the emergence of ocean colour captured by satellites. We will present some recent developments to establish this link by simultaneously employing (1) a satellite bio-optical algorithm that uses optical fingerprints of phytoplankton such as light absorption to estimate phytoplankton cell size, size structure, and phytoplankton carbon from ocean colour and (2) a functional gene microarray containing archetype probes based on functional genes of phytoplankton (encoding enzymes involved in critical metabolic functions such as carbon and nitrogen assimilation). Applying these methods to phytoplankton assemblages sampled during the North Atlantic Bloom experiment cruise, we will show how the genes encoding the enzyme RuBisCO (rbcL) and derived phytoplankton genetic diversity link to satellite-derived phytoplankton carbon and phytoplankton size spectrum. Results will be discussed in the context of how the two independent approaches can further be combined to better characterize the biodiversity of phytoplankton at a high resolution, and understand the emergence of phytoplankton community structure, on a global scale.