Cyanobacteria Boring Limestones in Freshwater Settings-Their Pioneering Role in Sculpturing Pebbles and Carbonate Dissolution.

In freshwater lakes and rivers, cyanobacteria belonging to the family Leptolyngbyaceae bore > 1 mm deep into limestone pebbles by dissolving carbonate at the tip of their 3-8 μm-thick filaments. The abundance of these borings decreases downward while it is so high at the rock surface that micrometric debris is formed. Moreover, the disintegrated material on the pebbles' surface can be easily removed, for instance, when pebbles are grinding against each other due to wave or current action or when insect larvae settle and scratch loosened grains from the surface while constructing their cases.

Tidal control on aerobic methane oxidation and mitigation of methane emissions from coastal mangrove sediments.

Mangrove forests represent important sources of methane, partly thwarting their ecosystem function as an efficient atmospheric carbon dioxide sink. Many studies have focused on the spatial and temporal variability of methane emissions from mangrove ecosystems, yet little is known about the microbial and physical controls on the release of biogenic methane from tidally influenced mangrove sediments. Here, we show that aerobic methane oxidation is a key microbial process that effectively reduces methane emissions from mangrove sediments.

Controls and significance of priming effects in lake sediments.

Warming and eutrophication influence carbon (C) processing in sediments, with implications for the global greenhouse-gas budget. Temperature effects on sedimentary C loss are well understood, but the mechanism of change in turnover through priming with labile organic matter (OM) is not. Evaluating changes in the magnitude of priming as a function of warming, eutrophication, and OM stoichiometry, we incubated sediments with C-labeled fresh organic matter (FOM, algal/cyanobacterial) and simulated future climate scenarios (+4°C and +8°C).

Water column dynamics control nitrite-dependent anaerobic methane oxidation by Candidatus "Methylomirabilis" in stratified lake basins.

We investigated microbial methane oxidation in the water column of two connected but hydrodynamically contrasting basins of Lake Lugano, Switzerland. Both basins accumulate large amounts of methane in the water column below their chemoclines, but methane oxidation efficiently prevents methane from reaching surface waters. Here we show that in the meromictic North Basin water column, a substantial fraction of methane was eliminated through anaerobic methane oxidation (AOM) coupled to nitrite reduction by Candidatus Methylomirabilis.

Multiple Groups of Methanotrophic Bacteria Mediate Methane Oxidation in Anoxic Lake Sediments.

Freshwater lakes represent an important source of the potent greenhouse gas methane (CH) to the atmosphere. Methane emissions are regulated to large parts by aerobic (MOx) and anaerobic (AOM) oxidation of methane, which are important CH sinks in lakes. In contrast to marine benthic environments, our knowledge about the modes of AOM and the related methanotrophic microorganisms in anoxic lake sediments is still rudimentary.