In Situ Ammonium Profiling Using Solid-Contact Ion-Selective Electrodes in Eutrophic Lakes
A promising profiling setup for in situ measurements in lakes with potentiometric solid-contact ion-selective electrodes (SC-ISEs) and a data processing method for sensor calibration and drift correction are presented. The profiling setup consists of a logging system, which is equipped with a syringe sampler and sensors for the measurement of standard parameters including temperature, conductivity, oxygen and photosynthetically active radiation (PAR). The setup was expanded with SC-ISEs in galvanically separated amplifiers. The potential for high-resolution profiling is investigated by deploying the setup in the eutrophic Lake Rotsee (Lucerne, Switzerland), using two different designs of am…
Methanotrophy under Versatile Conditions in the Water Column of the Ferruginous Meromictic Lake La Cruz (Spain)
Lakes represent a considerable natural source of methane to the atmosphere compared to their small global surface area. Methanotrophs in sediments and in the water column largely control methane fluxes from these systems, yet the diversity, electron accepting capacity, and nutrient requirements of these microorganisms have only been partially identified. Here, we investigated the role of electron acceptors alternative to oxygen and sulfate in microbial methane oxidation at the oxycline and in anoxic waters of the ferruginous meromictic Lake La Cruz, Spain. Active methane turnover in a zone extending well below the oxycline was evidenced by stable carbon isotope-based rate measurements. We o…