Enzymes and Nitrogen Cycling

Berges, John A.; Mulholland, Margaret R.

doi:10.1016/b978-0-12-372522-6.00032-3

Cited by 47 publications

(36 citation statements)

References 314 publications

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“…Similar to DIN and specifically NH 4 + (Glibert et al 1995), labile DON compounds can turn over rapidly in natural waters (Fuhrman 1990 [DFAA]; Lomas et al 2002 [urea]; Mulholland et al, 2009 [peptides]) and a fraction of the DON pool in aquatic systems appears bioavailable to phytoplankton (Berman and Bronk 2003;Bronk 2002). Many larger organic compounds that are present in treated effluents (Pehlivanoglu-Mantas and Sedlak 2006) can also be taken up by microbes after first rendering HMW compounds into low molecular weight compounds through a variety of extracellular enzyme reactions (Berg et al 2003;Berges and M. R. Mulholland, 2008;Pantoja et al 1997). However, there is also a large fraction of DON that is degraded over longer timescales or is refractory (Berman and Bronk 2003;Bronk 2002;Kirchman et al 1993).…”

Section: Discussionmentioning

confidence: 98%

The Bioavailability of Effluent-derived Organic Nitrogen along an Estuarine Salinity Gradient

Filippino

Mulholland

Bernhardt

et al. 2010

Estuaries and Coasts

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Total maximum daily loads for nitrogen (N) are currently being established for the Chesapeake Bay watershed. While we know inorganic N is bioavailable in the environment and therefore its input contributes to cultural eutrophication, the bioavailability of organic N is unclear. Using bioassay experiments, we examined the impact of effluent-derived organic nitrogen (EON) from wastewater treatment plants on natural water samples collected along an estuarine/salinity gradient within the lower Chesapeake Bay watershed. All of the inorganic N and between 31% and 96% of the EON was removed during biotic bioassays within the first 2 days. Further, there was substantial abiotic reactivity of effluent N when it was added to natural water samples. Results demonstrate that organic and inorganic N in effluent is removed to support the growth of microbial communities. These are the first results aimed at assessing the reactivity of EON in natural waters along an estuarine/salinity gradient.

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Section: Discussionmentioning

confidence: 98%

The Bioavailability of Effluent-derived Organic Nitrogen along an Estuarine Salinity Gradient

Filippino

Mulholland

Bernhardt

et al. 2010

Estuaries and Coasts

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“…Theoretically it could also occur through facilitated diffusion but it is unlikely that the concentrations outside the cell would be high enough (mM) to create a concentration gradient into the cell. For compounds greater than ~1 kDa, direct uptake cannot occur and phytoplankton must use other mechanisms often involving enzymes (reviewed in Berges and Mulholland, 2008;Lewitus and Subba Rao, 2006). Proteolytic enzymes break down HMW compounds into their LMW constituent molecules, which are more accessible to the cell.…”

Section: Enzymatic Decompositionmentioning

confidence: 99%

Dynamics of Dissolved Organic Nitrogen

Sipler¹,

Bronk²

2015

Biogeochemistry of Marine Dissolved Organic Matter

117

128

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“…Phytoplankton are also capable of utilizing low molecular weight DON moieties such as urea [Bronk et al, 2007], providing a third potential sink for surface accumulated DON. However, much of the DON found in open ocean surface waters occurs as larger, complex organic molecules with amide functional groups [McCarthy et al, 1997;Aluwihare et al, 2005] that are thought to be largely unavailable to photoautotrophs, instead requiring extracellular breakdown by microbes to release N [Berges and Mulholland, 2008]. Thus, alternative surface ocean sinks for DON not tested in our incubation experiments are considered unlikely to contribute significantly to DON removal in the euphotic zone. )…”

Section: The Fate Of Don Within Ocean Subtropical Gyres and Related Umentioning

confidence: 99%

Dissolved organic nitrogen in the global surface ocean: Distribution and fate

Letscher

Hansell

Carlson

et al. 2013

Global Biogeochemical Cycles

119

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The allochthonous supply of dissolved organic nitrogen (DON) from gyre margins into the interior of the ocean's oligotrophic subtropical gyres potentially provides an important source of new N to gyre surface waters, thus sustaining export production. This process requires that a fraction of the transported DON be available to euphotic zone photoautotroph communities via mineralization. In this study, we investigated the biological and physical controls on the distribution and fate of DON within global ocean surface waters. Inputs of nitrate to the euphotic zone at upwelling zones fuel net accumulation of a DON pool that appears to resist rapid microbial remineralization, allowing subsequent advective transport into the subtropical gyres. Zonal gradients in DON concentrations across these gyres imply a DON sink in the surface layer. Assessment of the physical dynamics of gyre circulation and winter mixing revealed a pathway for DON removal from the mixed layer via vertical transport to the deep euphotic zone, which establishes the observed zonal gradients. Incubation experiments from the Florida Straits indicated surface‐accumulated DON was largely resistant (over a few months) to utilization by the extant surface bacterioplankton community. In contrast, this same material was remineralized three times more rapidly when exposed to upper mesopelagic bacterioplankton. These results suggest the primary fate of surface DON to be removal via vertical mixing and subsequent mineralization below the mixed layer, implying a limited role for direct DON support of gyre export production from the surface layer. DON may contribute to export production at the eastern edges of the subtropical gyres, but only after its mineralization within the deep euphotic zone.

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Enzymes and Nitrogen Cycling

Cited by 47 publications

References 314 publications

The Bioavailability of Effluent-derived Organic Nitrogen along an Estuarine Salinity Gradient

The Bioavailability of Effluent-derived Organic Nitrogen along an Estuarine Salinity Gradient

Dynamics of Dissolved Organic Nitrogen

Dissolved organic nitrogen in the global surface ocean: Distribution and fate

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