Dataset Information

High rates of denitrification and nitrous oxide emission in arid biological soil crusts from the Sultanate of Oman.

ABSTRACT: Using a combination of process rate determination, microsensor profiling and molecular techniques, we demonstrated that denitrification, and not anaerobic ammonium oxidation (anammox), is the major nitrogen loss process in biological soil crusts from Oman. Potential denitrification rates were 584±101 and 58±20 ?mol N m(-2) h(-1) for cyanobacterial and lichen crust, respectively. Complete denitrification to N2 was further confirmed by an (15)NO3(-) tracer experiment with intact crust pieces that proceeded at rates of 103±19 and 27±8 ?mol N m(-2) h(-1) for cyanobacterial and lichen crust, respectively. Strikingly, N2O gas was emitted at very high potential rates of 387±143 and 31±6 ?mol N m(-2) h(-1) from the cyanobacterial and lichen crust, respectively, with N2O accounting for 53-66% of the total emission of nitrogenous gases. Microsensor measurements revealed that N2O was produced in the anoxic layer and thus apparently originated from incomplete denitrification. Using quantitative PCR, denitrification genes were detected in both the crusts and were expressed either in comparable (nirS) or slightly higher (narG) numbers in the cyanobacterial crusts. Although 99% of the nirS sequences in the cyanobacterial crust were affiliated to an uncultured denitrifying bacterium, 94% of these sequences were most closely affiliated to Paracoccus denitrificans in the lichen crust. Sequences of nosZ gene formed a distinct cluster that did not branch with known denitrifying bacteria. Our results demonstrate that nitrogen loss via denitrification is a dominant process in crusts from Oman, which leads to N2O gas emission and potentially reduces desert soil fertility.

SUBMITTER: Abed RM

PROVIDER: S-EPMC3749496 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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High rates of denitrification and nitrous oxide emission in arid biological soil crusts from the Sultanate of Oman.

Abed Raeid M M RM Lam Phyllis P de Beer Dirk D Stief Peter P

The ISME journal 20130411 9

Using a combination of process rate determination, microsensor profiling and molecular techniques, we demonstrated that denitrification, and not anaerobic ammonium oxidation (anammox), is the major nitrogen loss process in biological soil crusts from Oman. Potential denitrification rates were 584±101 and 58±20 μmol N m(-2) h(-1) for cyanobacterial and lichen crust, respectively. Complete denitrification to N2 was further confirmed by an (15)NO3(-) tracer experiment with intact crust pieces that ...[more]

PMID: 23575368

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Project description:Previous studies have documented the capacity of European earthworms belonging to the family Lumbricidae to emit the greenhouse gas nitrous oxide (N(2)O), an activity attributed primarily to the activation of ingested soil denitrifiers. To extend the information base to earthworms in the Southern Hemisphere, four species of earthworms in New Zealand were examined for gut-associated denitrification. Lumbricus rubellus and Aporrectodea rosea (introduced species of Lumbricidae) emitted N(2)O, whereas emission of N(2)O by Octolasion cyaneum (an introduced species of Lumbricidae) and emission of N(2)O by Octochaetus multiporus (a native species of Megascolecidae) were variable and negligible, respectively. Exposing earthworms to nitrite or nitrate and acetylene significantly increased the amount of N(2)O emitted, implicating denitrification as the primary source of N(2)O and indicating that earthworms emitted dinitrogen (N(2)) in addition to N(2)O. The alimentary canal displayed a high capacity to produce N(2)O when it was supplemented with nitrite, and alimentary canal contents contained large amounts of carbohydrates and organic acids indicative of fermentation (e.g., succinate, acetate, and formate) that could serve as sources of reductant for denitrification. nosZ encodes a portion of the terminal oxidoreductase used in denitrification. The nosZ sequences detected in the alimentary canals of L. rubellus and O. multiporus were similar to those retrieved from soil and were distantly related to sequences of uncultured soil bacteria and genera common in soils (i.e., Bradyrhizobium, Azospirillum, Rhodopseudomonas, Rhodospirillum, Pseudomonas, Oligotropha, and Sinorhizobium). These findings (i) suggest that the capacity to emit N(2)O and N(2) is a general trait of earthworms and not geographically restricted, (ii) indicate that species belonging to different earthworm families (i.e., Megascolecidae and Lumbricidae) may not have equal capacities to emit N(2)O, and (iii) also corroborate previous findings that link this capacity to denitrification in the alimentary canal.

Dataset Information

High rates of denitrification and nitrous oxide emission in arid biological soil crusts from the Sultanate of Oman.

Publications

High rates of denitrification and nitrous oxide emission in arid biological soil crusts from the Sultanate of Oman.

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