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Abstract: During the last decade, the hypothesis that one or more biodiversity drops inthe Phanerozoic eon, evident in the geological record, might have been causedby the most powerful kind of stellar explosion so far known Gamma Ray Burstshas been discussed in several works. These stellar explosions could have leftan 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 inthe aquatic primary producers on Earth. This effect on life appears as a resultof ultraviolet UV re-transmission in the atmosphere of a fraction of thegamma energy, resulting in an intense UV flash capable of penetrating ~ tens ofmeters in the water column in the ocean. We focus on the action of the UV flashon phytoplankton, as they are the main contributors to global aquatic primaryproductivity. Our results suggest that the UV flash could cause an hemisphericreduction of phytoplankton biomass in the upper mixed layer of the World Oceanof around 10%, but this figure can reach up to 25 % for radiation-sensitivepicoplankton species, and-or in conditions in which DNA repair mechanisms areinhibited.

Autor: Mayrene Guimarais, Rolando Cardenas, Jorge Horvath


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