Biological Weighting Function for the Inhibition of Phytoplankton Photosynthesis by Ultraviolet Radiation

TLDR

The severe depletion of stratospheric ozone over Antarctica has heightened concerns about the biological impacts of UVB radiation (280–320 nm). The authors measured phytoplankton photosynthesis across a range of irradiances and fitted the data to an analytical model to derive a spectral biological weighting function for predicting ozone‑depletion effects on aquatic photosynthesis. UVA (320–400 nm) significantly inhibits photosynthesis in a marine diatom and dinoflagellate, with UVB causing even greater inhibition; the model predicts the Antarctic ozone hole could reduce near‑surface photosynthesis by 12–15 % but less at depth, and the experimental system enables routine estimation of spectral weightings.

Abstract

Severe reduction of stratospheric ozone over Antarctica has focused increasing concern on the biological effects of ultraviolet-B (UVB) radiation (280 to 320 nanometers). Measurements of photosynthesis from an experimental system, in which phytoplankton are exposed to a broad range of irradiance treatments, are fit to an analytical model to provide the spectral biological weighting function that can be used to predict the short-term effects of ozone depletion on aquatic photosynthesis. Results show that UVA (320 to 400 nanometers) significantly inhibits the photosynthesis of a marine diatom and a dinoflagellate, and that the effects of UVB are even more severe. Application of the model suggests that the Antarctic ozone hole might reduce near-surface photosynthesis by 12 to 15 percent, but less so at depth. The experimental system makes possible routine estimation of spectral weightings for natural phytoplankton.