The Importance of Dissimilatory Nitrate Reduction to Ammonium (DNRA) in the Nitrogen Cycle of Coastal Ecosystems
TL;DR: The Oceanography 26, no. 3 (2013): 124-131, doi:10.5670/oceanog.2013.54.1 as discussed by the authors, was published by The Oceanography Society.
Abstract: Author Posting. © The Oceanography Society, 2013. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 26, no. 3 (2013): 124–131, doi:10.5670/oceanog.2013.54.
Citations
More filters
TL;DR: A significant shift in the microbiome of those fed 10% microplastics is found with significant decreases in the relative abundance of the families Rhizobiaceae, Xanthobacteraceae and Isosphaeraceae, which contain key microbes that contribute to nitrogen cycling and organic matter decomposition.
240 citations
Cites background from "The Importance of Dissimilatory Nit..."
...This is an important process that removes reactive N from the ecosystem (Giblin et al., 2013)....
[...]
TL;DR: This research was supported by the NASA postdoctoral program (EES), the NSF Graduate Research Fellowship Program (MAK), the Agouron Institute (MCK, RB) and theNSF FESD program (grant number 1338810, subcontract to RB).
240 citations
TL;DR: A fallout plume of hydrocarbons from the Macondo Well contaminating the ocean floor over an area of 3,200 km2 is identified, suggesting the oil initially was suspended in deep waters and then settled to the underlying sea floor, and implicates accelerated settling as an important fate for suspended oil.
Abstract: The sinking of the Deepwater Horizon in the Gulf of Mexico led to uncontrolled emission of oil to the ocean, with an official government estimate of ∼ 5.0 million barrels released. Among the pressing uncertainties surrounding this event is the fate of ∼ 2 million barrels of submerged oil thought to have been trapped in deep-ocean intrusion layers at depths of ∼ 1,000-1,300 m. Here we use chemical distributions of hydrocarbons in >3,000 sediment samples from 534 locations to describe a footprint of oil deposited on the deep-ocean floor. Using a recalcitrant biomarker of crude oil, 17α(H),21β(H)-hopane (hopane), we have identified a 3,200-km(2) region around the Macondo Well contaminated by ∼ 1.8 ± 1.0 × 10(6) g of excess hopane. Based on spatial, chemical, oceanographic, and mass balance considerations, we calculate that this contamination represents 4-31% of the oil sequestered in the deep ocean. The pattern of contamination points to deep-ocean intrusion layers as the source and is most consistent with dual modes of deposition: a "bathtub ring" formed from an oil-rich layer of water impinging laterally upon the continental slope (at a depth of ∼ 900-1,300 m) and a higher-flux "fallout plume" where suspended oil particles sank to underlying sediment (at a depth of ∼ 1,300-1,700 m). We also suggest that a significant quantity of oil was deposited on the ocean floor outside this area but so far has evaded detection because of its heterogeneous spatial distribution.
231 citations
TL;DR: In this paper, a manipulation experiment was conducted to determine the influence of organic C and NO3− loading on partitioning of sediment thin discs in large aquarium tanks with filtered, N2/CO2 sparged seawater to maintain O2 limited conditions.
163 citations
TL;DR: A meta-analysis of experimental soil salinization effects on 19 variables related to N pools, cycling processes and fluxes in coastal ecosystems improves the understanding of the responses of ecosystem N cycling to soil Salinization, identifies knowledge gaps and highlights the urgent need for studies on the effects of soilSalinization on coastal agro-ecosystem and microbial N immobilization.
Abstract: Salinity intrusion caused by land subsidence resulting from increasing groundwater abstraction, decreasing river sediment loads and increasing sea level because of climate change has caused widespread soil salinization in coastal ecosystems. Soil salinization may greatly alter nitrogen (N) cycling in coastal ecosystems. However, a comprehensive understanding of the effects of soil salinization on ecosystem N pools, cycling processes and fluxes is not available for coastal ecosystems. Therefore, we compiled data from 551 observations from 21 peer-reviewed papers and conducted a meta-analysis of experimental soil salinization effects on 19 variables related to N pools, cycling processes and fluxes in coastal ecosystems. Our results showed that the effects of soil salinization varied across different ecosystem types and salinity levels. Soil salinization increased plant N content (18%), soil NH4+ (12%) and soil total N (210%), although it decreased soil NO3− (2%) and soil microbial biomass N (74%). Increasing soil salinity stimulated soil N2O fluxes as well as hydrological NH4+ and NO2− fluxes more than threefold, although it decreased the hydrological dissolved organic nitrogen (DON) flux (59%). Soil salinization also increased the net N mineralization by 70%, although salinization effects were not observed on the net nitrification, denitrification and dissimilatory nitrate reduction to ammonium in this meta-analysis. Overall, this meta-analysis improves our understanding of the responses of ecosystem N cycling to soil salinization, identifies knowledge gaps and highlights the urgent need for studies on the effects of soil salinization on coastal agro-ecosystem and microbial N immobilization. Additional increases in knowledge are critical for designing sustainable adaptation measures to the predicted intrusion of salinity intrusion so that the productivity of coastal agro-ecosystems can be maintained or improved and the N losses and pollution of the natural environment can be minimized.
134 citations
References
More filters
TL;DR: Humans must modify their behavior or risk causing irreversible changes to life on Earth, as the damage done by humans to the nitrogen economy of the planet will persist for decades, possibly centuries, if active intervention and careful management strategies are not initiated.
Abstract: Atmospheric reactions and slow geological processes controlled Earth's earliest nitrogen cycle, and by ~2.7 billion years ago, a linked suite of microbial processes evolved to form the modern nitrogen cycle with robust natural feedbacks and controls. Over the past century, however, the development of new agricultural practices to satisfy a growing global demand for food has drastically disrupted the nitrogen cycle. This has led to extensive eutrophication of fresh waters and coastal zones as well as increased inventories of the potent greenhouse gas nitrous oxide (N(2)O). Microbial processes will ultimately restore balance to the nitrogen cycle, but the damage done by humans to the nitrogen economy of the planet will persist for decades, possibly centuries, if active intervention and careful management strategies are not initiated.
1,882 citations
TL;DR: The removal of nitrogen in aquatic ecosystems is of great interest because excessive nitrate in groundwater and surface water is a growing problem and is linked to eutrophication and harmful algal blooms, especially in coastal marine waters.
Abstract: The removal of nitrogen (N) in aquatic ecosystems is of great interest because excessive nitrate in groundwater and surface water is a growing problem. High nitrate loading degrades water quality and is linked to eutrophication and harmful algal blooms, especially in coastal marine waters. Past research on nitrate removal processes has emphasized plant or microbial uptake (assimilation) or respiratory denitrification by bacteria. The increasing application of stable isotopes and other tracer techniques to the study of nitrate removal has yielded a growing body of evidence for alternative, microbially mediated processes of nitrate transformation. These include dissimilatory (the reduction of nitrogen into other inorganic compounds, coupled to energy producing processes) reduction of nitrate to ammonium (DNRA), chemoautotrophic denitrification via sulfur or iron oxidation, and anaerobic ammonium oxidation (anammox), as well as abiotic nitrate removal processes. Here, we review evidence for the importance of...
954 citations
TL;DR: It is suggested that organic carbon is more important than oxygen status in determining denitrifying enzyme content of habitats, and Michaelis-Menten theoretical models suggest the conditions required to achieve changes in partitioning between the two fates of nitrate.
Abstract: Organisms with the denitrification capacity are widely distributed and in high density in nature. It is not well understood why they are so successful. A survey of denitrifying enzyme content of various habitats is presented which indicates a role of carbon and oxygen, but not nitrate, in affecting denitrifier populations. It is suggested that organic carbon is more important than oxygen status in determining denitrifying enzyme content of habitats. In low oxygen environments, denitrifiers compete with organisms that dissimilate nitrate to ammonium, a process which conserves nitrogen. The energetic and kinetic parameters that affect this competition are evaluated. The latter is examined using Michaelis-Menten theoretical models by varying Vmax, Km, and So (substrate concentration) for the two competing populations. The outcome predicted by these models is presented and discussed in relation to previous data on population densities and Km values for representatives of these competing groups. These models suggest the conditions required to achieve changes in partitioning between the two fates of nitrate. These considerations are important if one is to be able to evaluate and successfully “manage” the fate of nitrate in any habitat.
561 citations
TL;DR: In this article, the authors focus on one type of biotic feedback that influences eu- trophication patterns in coastal bays, and discuss the 2 aspects of plant-mediated nutrient cycling as eutrophica- tion induces a shift in primary producer dominance.
Abstract: Nutrient loading to coastal bay ecosystems is of a similar magnitude as that to deeper, river-fed estuar- ies, yet our understanding of the eutrophication process in these shallow systems lags far behind. In this synthesis, we focus on one type of biotic feedback that influences eu- trophication patterns in coastal bays—the important role of primary producers in the 'coastal filter'. We discuss the 2 aspects of plant-mediated nutrient cycling as eutrophica- tion induces a shift in primary producer dominance: (1) the fate of nutrients bound in plant biomass, and (2) the effects of primary producers on biogeochemical processes that in- fluence nutrient retention. We suggest the following gen- eralizations as eutrophication proceeds in coastal bays: (1) Long-term retention of recalcitrant dissolved and particu- late organic matter will decline as seagrasses are replaced by algae with less refractory material. (2) Benthic grazers buffer the early effects of nutrient enrichment, but con- sumption rates will decline as physico-chemical conditions stress consumer populations. (3) Mass transport of plant- bound nutrients will increase because attached perennial macrophytes will be replaced by unattached ephemeral algae that move with the water. (4) Denitrification will be an unimportant sink for N because primary producers typically outcompete bacteria for available N, and parti- tioning of nitrate reduction will shift to dissimilatory nitrate reduction to ammonium in later stages of eutrophication. In tropical/subtropical systems dominated by carbonate sediments, eutrophication will likely result in a positive feedback where increased sulfate reduction and sulfide accumulation in sediments will decrease P adsorption to Fe and enhance the release of P to the overlying water.
520 citations
TL;DR: It is demonstrated that diverse microbial taxa possess divergent nos clusters with genes that are related yet evolutionarily distinct from the typical nos genes of denitirifers, and that nondenitrifying populations with a broad range of metabolisms and habitats are potentially significant contributors to N2O consumption.
Abstract: Agricultural and industrial practices more than doubled the intrinsic rate of terrestrial N fixation over the past century with drastic consequences, including increased atmospheric nitrous oxide (N2O) concentrations. N2O is a potent greenhouse gas and contributor to ozone layer destruction, and its release from fixed N is almost entirely controlled by microbial activities. Mitigation of N2O emissions to the atmosphere has been attributed exclusively to denitrifiers possessing NosZ, the enzyme system catalyzing N2O to N2 reduction. We demonstrate that diverse microbial taxa possess divergent nos clusters with genes that are related yet evolutionarily distinct from the typical nos genes of denitirifers. nos clusters with atypical nosZ occur in Bacteria and Archaea that denitrify (44% of genomes), do not possess other denitrification genes (56%), or perform dissimilatory nitrate reduction to ammonium (DNRA; (31%). Experiments with the DNRA soil bacterium Anaeromyxobacter dehalogenans demonstrated that the atypical NosZ is an effective N2O reductase, and PCR-based surveys suggested that atypical nosZ are abundant in terrestrial environments. Bioinformatic analyses revealed that atypical nos clusters possess distinctive regulatory and functional components (e.g., Sec vs. Tat secretion pathway in typical nos), and that previous nosZ-targeted PCR primers do not capture the atypical nosZ diversity. Collectively, our results suggest that nondenitrifying populations with a broad range of metabolisms and habitats are potentially significant contributors to N2O consumption. Apparently, a large, previously unrecognized group of environmental nosZ has not been accounted for, and characterizing their contributions to N2O consumption will advance understanding of the ecological controls on N2O emissions and lead to refined greenhouse gas flux models.
498 citations