Ozone Depletion: Ultraviolet Radiation and Phytoplankton Biology in Antarctic Waters

TLDR

The springtime stratospheric ozone layer over Antarctica is thinning by up to 50 %, allowing more UVB radiation to reach the Southern Ocean surface. The study investigates whether the increased UVB irradiance penetrating the marginal ice zone’s near‑surface waters will harm phytoplankton communities and alter Antarctic marine ecosystem dynamics. A 6‑week 1990 Icecolors cruise found that ozone depletion raised UVB‑to‑total irradiance ratios and UVB inhibition of photosynthesis, reducing primary production by 6–12 % and demonstrating that ozone‑dependent spectral shifts affect phytoplankton photoinhibition, photoreactivation, photoprotection, and photosynthesis.

Abstract

The springtime stratospheric ozone (O 3 ) layer over the Antarctic is thinning by as much as 50 percent, resulting in increased midultraviolet (UVB) radiation reaching the surface of the Southern Ocean. There is concern that phytoplankton communities confined to near-surface waters of the marginal ice zone will be harmed by increased UVB irradiance penetrating the ocean surface, thereby altering the dynamics of Antarctic marine ecosystems. Results from a 6-week cruise (Icecolors) in the marginal ice zone of the Bellingshausen Sea in austral spring of 1990 indicated that as the O 3 layer thinned: (i) sea surface- and depth-dependent ratios of UVB irradiance (280 to 320 nanometers) to total irradiance (280 to 700 nanometers) increased and (ii) UVB inhibition of photosynthesis increased. These and other Icecolors findings suggest that O 3 -dependent shifts of in-water spectral irradiances alter the balance of spectrally dependent phytoplankton processes, including photoinhibition, photoreactivation, photoprotection, and photosynthesis. A minimum 6 to 12 percent reduction in primary production associated with O 3 depletion was estimated for the duration of the cruise.