<p>Light is an important regulator of photo-chemical and photo-biological processes in coastal areas. However, understanding how the atmosphere-ocean interaction drives changes in the amount of light entering coastal waters and how changes in the underwater light environment influence the biological characteristic of coastal water can be challenging due to the complex oceanographic dynamic of these areas. Here, we empirically describe the seasonal relationships between meteorological and oceanographic variables over a three year period and quantify the effect light have on the productivity of a coastal area off the Otago coast, New Zealand, through the application of an oceanographic-biological model. The model quantifies changes in the production-biomass ratio (PP / B) (i.e. rate of production of organic matter from phytoplankton produced per unit of total organic biomass) using measurements of the underwater attenuation coefficient, particulate organic carbon, chlorophyll-a and sea temperature. The sensitivity of the model to input data was estimated by comparing the PP / B ratio predicted from Chl a concentrations derived from field measurements of the attenuation coefficients of PAR light <em>K<sub>d </sub></em>(<em>m</em><sup>−1</sup>) and Chl a concentrations derived from remote sensing data of <em>K<sub>d </sub></em>(<em>m</em><sup>−1</sup>). The results presented here indicate a mild increment in solar radiation partially driven by increased wind speeds and reduction of cloud cover, ultimately producing small increments in the amount of solar radiation penetrating the water column, especially during summer. The model formulated, predict important seasonal shifts in the PP/B ratio. These shifts are driven by the rate at which light decays and likely modulated by the frequency of wind speeds that favour increments of the thermoclines depth and an increment of sea surface temperatures in the area.</p>