Microbial life in Bourlyashchy, the hottest thermal pool of Uzon Caldera, Kamchatka.

Bourlyashchy is the largest and hottest pool in the Uzon Caldera, located in the territory of Kronotsky Nature Reserve, Kamchatka, Russia, with sediment surface temperatures at the margins ranging from 86 to 97 °C, and pH from 6.0 to 7.0. The microbial communities of the pool water and sediments were studied comprehensively from 2005 to 2014. Radioisotopic tracer studies revealed the processes of inorganic carbon assimilation, sulfate reduction, lithotrophic methanogenesis and potentially very active process of acetate oxidation to CO2. The total number of microbial cells in water was different in different years ranging from 5.2 to 7.0 × 10(6); in sediments, it changed from year to year between 6.3 × 10(6) and 1.75 × 10(8), increasing with a decrease in temperature. FISH with Archaea- and Bacteria-specific probes showed that the share of Bacteria differed with year, changing from 34 to 71%. According to 16S rRNA gene pyrosequencing data, lithoautotrophs (Aquificales and Thermoproteales) predominated in water samples, while in sediments they shared the niche with organotrophic Crenarchaeota, Korarchaeota, and bacteria of the genus Caldimicrobium (phylum Thermodesulfobacteria). The majority of organisms in water belonged to cultivated orders of prokaryotes; the only large uncultured group was that representing a novel order in class Thermoprotei. In sediments, unclassified Aquificeae comprised a significant part of the bacterial population. Thus, we showed that the hottest of the terrestrial hot pools studied contains numerous and active microbial populations where Bacteria represent a significant part of the microbial community, and planktonic and sediment populations differ in both composition and function.

Otolith delta 18O record of mid-Holocene sea surface temperatures in Peru.

Peruvian sea catfish (Galeichthys peruvianus) sagittal otoliths preserve a record of modern and mid-Holocene sea surface temperatures (SSTs). Oxygen isotope profiles in otoliths excavated from Ostra [6010 +/- 90 years before the present (yr B.P.); 8 degrees 55'S] indicate that summer SSTs were approximately 3 degrees C warmer than those of the present. Siches otoliths (6450 +/- 110 yr B.P.; 4 degrees 40'S) recorded mean annual temperatures approximately 3 degrees to 4 degrees C warmer than were measured under modern conditions. Trophic level and population diversity and equitability data from these faunal assemblages and other Peruvian archaeological sites support the isotope interpretations and suggest that upwelling of the Peru-Chile current intensified after approximately 5000 yr B.P.