Oxygen minimum zones are distinguished by characteristic distributions of the inorganic nitrogen compounds nitrate, nitrite, and nitrous oxide. Although many of the reactions that produce and consume these compounds are known, the mechanisms by which characteristic features, such as the secondary nitrite maximum and the subsurface nitrous oxide maximum, are maintained are not clear. Oxygen...
The eastern tropical North Pacific (ETNP) harbours the largest of the oceans’ three major oxygen minimum zones and is further characterized by what appears to be the largest open-ocean accumulation of methane, with peak concentrations located in the anoxic core. Benthic methanogenesis is a major methane source in the ETNP OMZ but it remains unknown to which extent methane is cycled within the...
Nitrogen (N) is an essential nutrient that limits productivity in large parts of the world ocean. While denitrification and anammox are the major processes responsible for the removal of this nutrient from the oceans, input occurs mainly through nitrogen fixation. Estimates of marine N budgets suggest that losses exceed inputs, while models imply that nitrogen fixation should be enhanced in...
Oceanic N2O emissions to the atmosphere represent up to 35 % of the global natural sources, and oxygen minimum zones (OMZs) are the major sites for net N2O production. In order to understand what controls net N2O fluxes, and whether the magnitude of N2O production might change in response to global climate and environmental change, it is necessary to determine the factors that influence the...
Within oxygen minimum zones (OMZs) microbial biogeochemical cycling is adapted to limited availability of oxygen (O2). Earlier studies suggested higher efficiency of carbon export in those regions due to reduced microbial degradation activity. However, previous findings on the effect of O2 on microbial activity are ambiguous and compared to nitrogen cycling little is known about microbial...
Foraminifera are a group of amoeboid protists commonly found in various marine habitats. Several benthic foraminiferal species are known to store nitrate and use it for complete denitrification, a unique energy metabolism among eukaryotes. This property and their high density in sediments of oxygen-depleted zones, pinpoint them as important players in the oceanic nitrogen cycle. Recent...
Stable isotopes (14,15N, 16,18O) of dissolved inorganic nitrogen (N) were measured in sediment porewaters and benthic flux chambers across the Peruvian oxygen minimum zone (OMZ) from 74 to 1000 m water depth. Sediments at all locations were net consumers of bottom water NO3-. In waters shallower than 400 m, this sink was largely attributed to dissimilatory nitrate reduction to ammonium (DNRA)...
The eastern tropical South Pacific Ocean (ETSP) contains one of the largest oxygen minimum zones (OMZ) in the world, with a pronounced impact on nutrient cycling and stoichiometry in the region. Low oxygen concentrations support nitrogen loss and release of sedimentary phosphorus, leading to inorganic macronutrient nitrogen to phosphorus ratios (N:P) in upwelled waters well below the Redfield...
The Black Sea has a characteristic “suboxic” transition zone at the interface between the oxic and anoxic water layers that is known as an important site of element transformations. However, the interaction between the biogeochemical structure of the water column and the depth zonation of microbial activities is not yet understood. We used high-resolution chemical profiling together with an...
Sulfur (S) is a major element on Earth. It is also a bioessential element for all living organisms. The transformation and mobilization of sulfur in biosphere, lithosphere, atmosphere, and hydrosphere constitute the Earth's S cycle, which are mainly driven by microorganisms. Sulfur oxidation is a major process in the cycling of S that involves diverse redox reactions. Diverse marine bacteria...
Oxygen minimum zones (OMZs) may expand in the future with important consequence on biogeochemical cycles. In well-oxygenated waters, temperature and plankton community structure are known as the main factors affecting the magnitude of the biological carbon pump, an ecosystem service that buffers the atmospheric CO2 concentration. In oxygen deficient waters, observations suggest that the...
Oxygen minimum zones (OMZs) are regions of the ocean where the depletion of oxygen leads to favorable conditions for microbial nitrogen (N) loss processes. Although OMZs make up less than 1% of the global ocean (oxygen $< 20~\mu M$), they host 20-40% of global oceanic N-loss through the processes of denitrification and anammox. Recent studies indicate that marine snow aggregates play a vital...
The oxygen minimum zone (OMZ) in deep water column of the oceans is over hundreds of years old and receive constant supply of organic matter from water above, but oxygen does not reach anoxia. Bacterial respiration is largely responsible for oxygen consumption in the OMZ and hence, any process that limits bacterial abundance and respiration contributes to the variation of OMZ. We hypothesize...