Intense ultraviolet perturbations on aquatic primary producers

TL;DR

This study models the impact of gamma ray burst-induced ultraviolet flashes on aquatic phytoplankton, suggesting significant potential reductions in primary productivity that could influence Earth's biological history.

Contribution

It provides a quantitative assessment of UV flash effects from gamma ray bursts on oceanic phytoplankton, highlighting potential ecological impacts.

Findings

UV flash could reduce phytoplankton biomass by about 10% globally.

Sensitive species could experience up to 25% biomass reduction.

The effects depend on DNA repair capabilities and environmental conditions.

Abstract

During the last decade, the hypothesis that one or more biodiversity drops in the Phanerozoic eon, evident in the geological record, might have been caused by the most powerful kind of stellar explosion so far known (Gamma Ray Bursts) has been discussed in several works. These stellar explosions could have left an imprint in the biological evolution on Earth and in other habitable planets. In this work we calculate the short-term lethality that a GRB would produce in the aquatic primary producers on Earth. This effect on life appears as a result of ultraviolet (UV) re-transmission in the atmosphere of a fraction of the gamma energy, resulting in an intense UV flash capable of penetrating ~ tens of meters in the water column in the ocean. We focus on the action of the UV flash on phytoplankton, as they are the main contributors to global aquatic primary productivity. Our results suggest that the UV flash could cause an hemispheric reduction of phytoplankton biomass in the upper mixed layer of the World Ocean of around 10%, but this figure can reach up to 25 % for radiation-sensitive picoplankton species, and/or in conditions in which DNA repair mechanisms are inhibited.