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Tropical lakes experience less thermal convection than temperate lakes and can be stably stratified by temperature gradients alone. Deep tropical lakes are often presumed meromictic, but conditions for sustained meromixis are poorly constrained. Here, we investigate the stratification stability of a deep (200 m) tropical Lake Towuti (Indonesia) and analyze its sensitivity to meteorological and climatic parameters using explora...
Prolonging survival in good health is a fundamental societal goal. However, the leading determinants of disability-free survival in healthy older people have not been well established. Data from ASPREE, a bi-national placebo-controlled trial of aspirin with 4.7 years median follow-up, was analysed. At enrolment, participants were healthy and without prior cardiovascular events, dementia or persistent physical disability. Disab...
In this paper, we outline the need for a coordinated international effort toward the building of an open-access Global Ocean Oxygen Database and ATlas (GO 2 DAT) complying with the FAIR principles (Findable, Accessible, Interoperable, and Reusable). GO 2 DAT will combine data from the coastal and open ocean, as measured by the chemical Winkler titration method or by sensors (e.g., optodes, electrodes) from Eulerian and Lagrang...
Functional redundancy imparts process stability to acidic Fe( II )‐oxidizing microbial reactorsNARA Subscribed
Summary In previous work, lab‐scale reactors designed to study microbial Fe(II) oxidation rates at low pH were found to have stable rates under a wide range of pH and Fe(II) concentrations. Since the stirred reactor environment eliminates many of the temporal and spatial variations that promote high diversity among microbial populations in nature, we were surprised that the reactors supported multiple taxa presumed to be autot...
Summary Ferruginous (Fe‐rich, SO 4 ‐poor) conditions are generally restricted to freshwater sediments on Earth today, but were likely widespread during the Archean and Proterozoic Eons. Lake Towuti, Indonesia, is a large ferruginous lake that likely hosts geochemical processes analogous to those that operated in the ferruginous Archean ocean. The metabolic potential of microbial communities and related biogeochemical cycling u...
We investigated anaerobic nitrogen (N) cycling in the water column of Lake Kivu, a deep meromictic tropical lake in East Africa. Data were collected at one station in the Northern Basin and one in the Southern Basin, during two sampling campaigns (June 2011—dry season, and February 2012—rainy season). Short‐term incubations of sulfide‐free water with 15 N‐labeled substrates revealed high potential denitrification and dissimila...
Chemoautotrophy and anoxygenic photosynthesis within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)NARA Subscribed
We quantified chemoautotrophic and anoxygenic photosynthetic microbial production in the water column of Lake Kivu, a permanently stratified tropical lake situated amidst volcanic activity, and aimed to identify the microorganisms involved in these processes through the analysis of their phospholipid fatty acid (PLFA) content and stable isotope ( 13 C) labelling of PLFA in a set of incubation experiments. Data demonstrate the...
Summary Heterotrophic P roteobacteria and A ctinobacteria were isolated from L ake M atano, I ndonesia, a stratified, ferruginous (iron‐rich), ultra‐oligotrophic lake with phosphate concentrations below 50 nM. Here, we describe the growth of eight strains of heterotrophic bacteria on a variety of soluble and insoluble sources of phosphorus. When transferred to medium without added phosphorus ( P ), the isolates grow slowly, th...
Carbon mineralization and oxygen dynamics in sediments with deep oxygen penetration, Lake SuperiorNARA Subscribed
To understand carbon and oxygen dynamics in sediments with deep oxygen penetration, we investigated eight locations (160–318‐m depth) throughout Lake Superior. Despite the 2–4 weight percent organic carbon content, oxygen penetrated into the sediment by 3.5 to > 12 cm at all locations. Such deep penetration is explained by low sedimentation rates (0.01–0.04 cm yr −1 ), high solubility of oxygen in freshwater, and a shallow (~...
Mixing and its effects on biogeochemistry in the persistently stratified, deep, tropical Lake Matano, IndonesiaNARA Subscribed
In the > 590‐m deep, tropical Lake Matano (Indonesia), stratification is characterized by weak thermal gradients ( K z ) cannot be estimated by conventional methods that rely on time derivatives of temperature distributions. We use and compare several alternative methods: one‐dimensional k ‐ε modeling, three‐dimensional hydrodynamic modeling, correlation with the size of Thorpe instabilities, and correlation with the stability...
We examined the chemical composition of the water column of Lake Matano, Sulawesi Island, Indonesia, to document how the high abundances of Fe (hydr)oxides in tropical soils and minimal seasonal temperature variability affect biogeochemical cycling in lakes. Lake Matano exhibits weak thermal stratification, yet a persistent pycnocline separates an oxic epilimnion from anoxic meta‐ and hypolimnions. The concentration of soluble...
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