Environmental determinants of aerobic methane oxidation in a tropical river network.

Aerobic methane oxidation (MOX) significantly reduces methane (CH) emissions from inland water bodies and is, therefore, an important determinant of global CH budget. Yet, the magnitude and controls of MOX rates in rivers - a quantitatively significant natural source of atmospheric CH - are poorly constrained. Here, we conducted a series of incubation experiments to understand the magnitude and environmental controls of MOX rates in tropical fluvial systems.

Land use drivers of riverine methane dynamics in a tropical river basin, India.

Rivers are globally significant natural sources of atmospheric methane (CH). However, the effect of land use changes on riverine CH dynamics, particularly in tropical zones, remain ambiguous, yet important to predict and anticipate the present and future contribution of rivers to the global CH budget. The present study examines the magnitude and drivers of riverine CH concentration and emission in the tropical Krishna River (KR) basin, India.

Magnitude and Drivers of Oxic Methane Production in Small Temperate Lakes.

Methanogenesis is traditionally considered as a strictly anaerobic process. Recent evidence suggests instead that the ubiquitous methane (CH) oversaturation found in freshwater lakes is sustained, at least partially, by methanogenesis in oxic conditions. Although this paradigm shift is rapidly gaining acceptance, the magnitude and regulation of oxic CH production (OMP) have remained ambiguous.

The role of methanotrophy in the microbial carbon metabolism of temperate lakes.

Previous stable isotope and biomarker evidence has indicated that methanotrophy is an important pathway in the microbial loop of freshwater ecosystems, despite the low cell abundance of methane-oxidizing bacteria (MOB) and the low methane concentrations relative to the more abundant dissolved organic carbon (DOC). However, quantitative estimations of the relative contribution of methanotrophy to the microbial carbon metabolism of lakes are scarce, and the mechanism allowing methanotrophy to be of comparable importance to DOC-consuming heterotrophy remained elusive. Using incubation experiments, microscopy, and multiple water column profiles in six temperate lakes, we show that MOB play a much larger role than their abundances alone suggest because of their larger cell size and higher specific activity.

Coupling of stable carbon isotopic signature of methane and ebullitive fluxes in northern temperate lakes.

Stable isotopic analysis is a popular method to understand the mechanisms sustaining methane (CH) emissions in various aquatic environments. Yet, the general lack of concurrent measurements of isotopes and fluxes impedes our ability to establish a connection between the variation in the rates of CH emission and isotopic signature. Here, we examine the magnitude of CH ebullition (bubbling) and stable carbon isotopic signature (δC-CH) of bubble CH in four northern temperate lakes and evaluate the in-lake processes shaping their variability.

Niche separation within aerobic methanotrophic bacteria across lakes and its link to methane oxidation rates.

Lake methane (CH ) emissions are largely controlled by aerobic methane-oxidizing bacteria (MOB) which mostly belong to the classes Alpha- and Gammaproteobacteria (Alpha- and Gamma-MOB). Despite the known metabolic and ecological differences between the two MOB groups, their main environmental drivers and their relative contribution to CH oxidation rates across lakes remain unknown. Here, we quantified the two MOB groups through CARD-FISH along the water column of six temperate lakes and during incubations in which we measured ambient CH oxidation rates.

Short-term variability of water quality and its implications on phytoplankton production in a tropical estuary (Cochin backwaters-India).

Changes in the phytoplankton biomass (chlorophyll a), production rate, and species composition were studied over two seasons using the time series measurements in the northern limb of the Cochin estuary in relation to the prevailing hydrological conditions. The present study showed the significant seasonal variation in water temperature (F=69.4, P<0.