Inversion models, in the context of oceanography, relate the observed ocean color to the concentrations of the different biogeochemical components present in the water of the ocean. However, building accurate inversion models can be quite complex due to the many factors that can influence the observed ocean color, such as variations in the composition or the optical properties of biogeochemical products. Here we assess the feasibility of the inversion approach, by implementing the three-stream light inversion model in a one-dimensional water column configuration, represented at the BOUSSOLE site in the northwestern Mediterranean Sea. Moreover, we provide a comprehensive sensitivity analysis of the model's skill by perturbing the parameters of the bio-optical properties and phytoplankton physiology. Analysis of the inversion indicates that the model is able to reconstruct the variability of the optical constituents. Results indicate that chlorophyll-a and coloured dissolved organic matter play a major role in light modulation. The sensitivity analysis shows that the parameterization of the ratio of chlorophyll-a to carbon is important for the performance of the inversion model. A coherent inversion model, as presented, can be used as an observational operator to assimilate remote sensing reflectance.

Satellites sensors provide useful data at different temporal and spatial scales to reconstruct the variability of marine ecosystems. Ocean color sensors in Earth orbit allow the derivation of spectral water leaving radiance and inference of physical and biogeochemical properties of the water masses 1 . In simple terms, the color of the sea is related to dissolved and particulate matter present in the water that for most of the ocean are of biological origin. In recent years, suitable algorithms have been developed to estimate the biogeochemical state of the oceans from measured radiance 2 . In particular, the derivation of water biogeochemical properties can be formulated in terms of the inversion of a forward problem. Mathematically, the so-called forward description resolves light propagation according to the properties of the medium in which the light propagates; the corresponding mathematical framework is well established 3 . In parallel, the inversion algorithms use the available information about the light field to retrieve the Inherent Optical Properties (IOPs) of the medium in which the light propagates. The major optical constituents of seawater in open oceans are phytoplankton, chromophoric dissolved organic matter (CDOM), and non algal particles (NAP) such as organic and mineral particles, bacteria, viruses and air bubbles. These biogeochemical components are important indicators of the ecosystem trophic regime and carbon pool formation 4 and are among the most common products derived from inversion algorithms 2 . In addition, these indicators are extremely useful to validate surface dynamics of coupled hydrodynamic biogeochemical ocean models, by comparing the distribution of satellite-derived biogeochemical products with corresponding distributions derived from model simulations 5 .

Traditionally, biogeochemical models used a simple Beer-Lambert formulation to describe photosynthetically available radiation (PAR) propagation along the water column, i.e. the downwelling irradiance integrated over visible wavelengths (from 400 to 700 nm) that decays exponentially due to attenuation. In recent years, a