Resistência microbiana à radiação Ultravioleta C (UVC – 254nm) e suas relações com a geoquímica sedimentar, em ambiente lacustre nos Andes Central (Lago Parón - Peru)

Abstract

Microorganisms are present everywhere on the planet, including in environments where survival requires high adaptability, such as the cryosphere. The Peruvian Andes, located in the tropical zone of South America, have significant importance for the continent's climate, as well as socioeconomic conditions for high mountain residents. In order to identify the presence of microorganisms and their relationship with the thaw in the modern era in this lake, sediments from Lake Parón were collected in October 2016, for subsequent subsampling every centimeter and microbiological analysis through cultivation in solid medium R2A, in concentrations of 10 and 100%, and incubated at 5 and 25 ºC, of each layer. Investigation of extremophiles in resistance to UVC radiation was applied at exposure times 5, 15, 30, 60, 120, 300 and 600 seconds, in cultures of each layer. Sedimentary geochemical research was carried out in the elemental analysis of C and N and isotopic analysis of δC13 and δN15, in addition to the magnetic susceptibility. The chronology was also established through the identification of Pb210. The results indicated that the analyzed core comprises the approximate period of 160 years of information that demonstrated, through sedimentary geochemistry and magnetic susceptibility, that the glaciers attached to Lake Parón suffered variations in their extension due to the local climate, anthropic actions and drastic recent events that caused great dynamics in the retreat and advance of the glaciers, varying the water volume of the lake. In the last 30 years there is a record of continuous retreat of these glaciers. The microbiological findings indicated the presence of psychrophiles and psychrotolerants, with a diversity similar to that found in research carried out in other regions of the terrestrial cryosphere. Counts of CFUs resistant to UVC exposure times were observed at all times and with microorganisms morphologically identified as bacteria, fungi and algae found in other surveys at glacial sites. The association of UVC-resistant microbes and geochemical parameters showed a high relationship with the environmental changes and climatic variations that the Lake Parón region has suffered in the last 160 years, including the events of loss of ice mass, with consequent variation in the lake level. The sediment had geological characteristics that determined UV-resistant microbial biodiversity, depending on glacier dynamics, cloud cover and availability of organic matter, in addition to the reflections of climatic events, such as the small ice age and the EL Niño phenomenon.