Organic matter processing by heterotrophic bacterioplankton in a large tropical river: Relating elemental composition and potential carbon mineralization.

River hydrology shapes the sources, concentration, and stoichiometry of organic matter within drainage basins. However, our understanding of how the microbes process dissolved organic matter (DOM) and recycle nutrients in tropical rivers needs to be improved. This study explores the relationships between elemental DOM composition (carbon/nitrogen/phosphorus: C/N/P), C and N uptake, and C mineralization by autochthonous bacterioplankton in the Usumacinta River, one of the most important fluvial systems in Mexico.

Anoxic nitrification with carbon-based materials as terminal electron acceptors.

This study investigates the potential of humic substances (HS) and graphene oxide (GO), as extracellular electron acceptors (EEA) for nitrification, aiming to explore alternatives to sustain this process in wastewater treatment systems. Experimental results demonstrate the conversion of ammonium to nitrate (up to 87 % of conversion) coupled to the reduction of either HS or GO by anaerobic consortia. Electron balance confirmed the contribution of HS and GO to ammonium oxidation.

Abiotic processes control carbon dioxide dynamics in temperate karst lakes.

Inland waters are crucial in the carbon cycle, contributing significantly to the global CO fluxes. Carbonate lakes may act as both sources and sinks of CO depending on the interactions between the amount of dissolved inorganic carbon (DIC) inputs, lake metabolisms, and geochemical processes. It is often difficult to distinguish the dominant mechanisms driving CO dynamics and their effects on CO emissions.

Anaerobic ammonium oxidation linked to sulfate and ferric iron reduction fuels nitrogen loss in marine sediments.

Availability of fixed nitrogen is a pivotal driver on primary productivity in the oceans, thus the identification of key processes triggering nitrogen losses from these ecosystems is of major importance as they affect ecosystems function and consequently global biogeochemical cycles. Denitrification and anaerobic ammonium oxidation coupled to nitrite reduction (Anammox) are the only identified marine sinks for fixed nitrogen. The present study provides evidence indicating that anaerobic ammonium oxidation coupled to the reduction of sulfate, the most abundant electron acceptor present in the oceans, prevails in marine sediments.

Inferring the relative resilience of alternative states.

Ecological systems may occur in alternative states that differ in ecological structures, functions and processes. Resilience is the measure of disturbance an ecological system can absorb before changing states. However, how the intrinsic structures and processes of systems that characterize their states affects their resilience remains unclear.

Eutrophication and sedimentation patterns in complete exploitation of water resources scenarios: an example from Northwestern semi-arid Mexico.

Water requirements to supply human needs lead water stakeholders to store more water during surplus periods to fulfil the demand during--not only--scarcity periods. At the reservoirs, mostly those in semi-arid regions, water level then fluctuates extremely between rises and downward during one single year. Besides of water management implications, changes on physical, chemical and biological dynamics of these drawdown and refilling are little known yet.

Does seston size structure reflect fish-mediated effects on water quality in a degraded semiarid wetland?

This study evaluates whether the size structure of seston (the sum of living and nonliving particles in the water column) reflects the effects of fish on wetland water quality. Using enclosures, we measured water quality and zooplankton community structure in the presence and absence of two fish species with distinct foraging strategies [benthivorous carp (Cyprinus carpio) and planktivorous mosquitofish (Gambusia holbrooki)]. Seston collected from the enclosures was counted and sized automatically with a Coulter counter, and the size structure in the range of 1-60 microm was modelled using the underlying Pareto distribution of particles.