Holocenic proxies of sedimentary organic matter and the evolution of Lake Arari-Amazon Region

Four sediment cores were sampled from Lake Arari, located on Marajo Island at the mouth of the Amazon River. The island's vegetation cover is composed mainly of Amazon coastal forest, herbaceous and varzea vegetation. The integration of data on sedimentary structures, pollen, carbon and nitrogen isotope records, C/N ratios and radiocarbon ages allowed the identification of changes in vegetation and the sources of organic matter accumulated in the lake during the Holocene. The data indicate a relatively high flow energy, marine water influence and the presence of mangroves during the lagoon phase between 8990 and 8690 cal yr B.P. and 2310-2230 cal yr B.P. Between 2310 and 2230 cal yr B.P. and similar to 1000 cal yr B.P., the flow energy decreased and the mangroves were replaced by herbaceous vegetation following the decline in marine influence, likely due to the increase in freshwater river discharge. During the last 1000 years, Lake Arari was established in association with the expansion of herbaceous vegetation and the dominance of freshwater algae. (C) 2011 Elsevier BM. All rights reserved.

Genome Sequence of Exiguobacterium antarcticum B7, Isolated from a Biofilm in Ginger Lake, King George Island, Antarctica

Exiguobacterium antarcticum is a psychotropic bacterium isolated for the first time from microbial mats of Lake Fryxell in Antarctica. Many organisms of the genus Exiguobacterium are extremophiles and have properties of biotechnological interest, e. g., the capacity to adapt to cold, which make this genus a target for discovering new enzymes, such as lipases and proteases, in addition to improving our understanding of the mechanisms of adaptation and survival at low temperatures. This study presents the genome of E. antarcticum B7, isolated from a biofilm sample of Ginger Lake on King George Island, Antarctic peninsula.

A 2400-year record of trace metal loading in lake sediments of Lagoa Vermelha, southeastern Brazil

Sediments of the Lagoa Vermelha (Red Lake), situated in the Ribeira Valley, southeastern Brazil, are made of a homogeneous, organic-rich, black clay with no visible sedimentary structures. The inorganic geochemical record (Al, As, Ba, Br, Co,Cs, Cr, Fe, Mn, Ni, Rb, Sc, Sb, V, Zn, Hg and Pb) of the lake sediments was analyzed in a core spanning 2430 years. The largest temporal changes in trace metal contents occurred approximately within the last 180 years. Recent sediments were found to be enriched in Pb, Zn, Hg, Ni, Mn, Br and Sb (more than 2-fold increase with respect to the "natural background level"). The enhanced accumulation of Br, Sb, and Mn was attributed to biogeochemical processes and diagenesis. On the other hand, the anomalous concentrations of Pb, Zn, Hg and Ni were attributed to pollution. As Lagoa Vermelha is located in a relatively pristine area, far removed from direct contamination sources, the increased metal contents of surface sediments most likely resulted from atmospheric fallout. Stable Pb isotopes provided additional evidence for anthropogenic contamination. The shift of Pb-206/Pb-207 ratios toward decreasing values in the increasingly younger sediments is consistent with an increasing contribution of airborne anthropogenic lead. In the uppermost sediments (0-10 cm), the lowest values of the Pb-206/Pb-207 ratios may reflect the influence of the less radiogenic Pb from the Ribeira Valley District ores (Pb-206/Pb-207 between 1.04 and 1.10), emitted during the last 50 years. (C) 2011 Elsevier Ltd. All rights reserved.

Effects of trophic levels (chlorophyll and phosphorous content) in three different water bodies (urban lake, reservoir and aquaculture facility) on gill morphology of Nile tilapia (Oreochromis niloticus)

Histological and ultrastructural analyses of gills were observed in Nile tilapia collected from three different waterbodies in southeast Brazil: an urban lake in a park in the city of São Paulo, a reservoir in a rural city, and a commercial aquaculture facility. These aterbodies were analyzed and classified as hypereutrophic, eutrophic, and supereutrophic, respectively, with 310.00, 94.00, 28.00 of phosphate (PO2_ 4 lg L _1) and 65.49, 24.95, 12.83 of chlorophyll (lg L _1). A significant difference in the histological alterations index (HAI) was observed only in fish from the urban lake, with the presence of cell hypertrophy, hyperplasia, aneurism, and other alterations. When compared to the other groups, a large quantity of rodlet cells was also observed in the urban group. These results demonstrate the correlation of eutrophic states of water with gill morphology. Also discussed is the premise that large amounts of organic material dissolved in water can alter the morphology of the fish gills