Preprints
https://doi.org/10.5194/os-2021-99
https://doi.org/10.5194/os-2021-99

  03 Nov 2021

03 Nov 2021

Review status: this preprint is currently under review for the journal OS.

Modelling the influence of light on the biological characteristics of coastal waters

Paulo Felipe Lagos1, Amandine Sabadel2, and Miles Lamare1 Paulo Felipe Lagos et al.
  • 1Department of Marine Science, University of Otago, 310 Castle Street, Dunedin, New Zealand
  • 2Department of Zoology, University of Otago, 310 Castle Street, Dunedin, New Zealand

Abstract. 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 Kd (m−1) and Chl a concentrations derived from remote sensing data of Kd (m−1). 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.

Paulo Felipe Lagos et al.

Status: open (until 08 Jan 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on os-2021-99', Jochen Wollschlaeger, 02 Dec 2021 reply

Paulo Felipe Lagos et al.

Paulo Felipe Lagos et al.

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Short summary
This study describes seasonal atmosphere-oceanographic trends over a three year period for an optically complex coastal area off the Otago coast, New Zealand, aiming to characterise the atmosphere-ocean connection and understand its influence on the penetration of light in the water column. Furthermore, a quantitative model based on satellite data and in situ measurements of how light decreases with depth is used to predict seasonal changes in the productivity of the area.