Biogenic nitrogen gas production at the oxic–anoxic interface in the Cariaco Basin, Venezuela

Montes, Enrique; Altabet, Mark A.; Karger, F.; Scranton, Mary I.; Thunell, Robert C.; Benitez-Nelson, Claudia R.; Lorenzoni, Laura; Astor, Yrene

doi:10.5194/bg-10-267-2013

Cited by 17 publications

(11 citation statements)

References 48 publications

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“…Below the oxic zone, nitrate is presumably used as a terminal electron acceptor by heterotrophic and/or lithotrophic prokaryotes (Rodriguez‐Mora et al, ; Scranton et al, ), fueling complete denitrification to N 2 (Montes et al, ) and/or partial denitrification to intermediates such as nitrite. Since nitrite rarely accumulates below 150 m (Figure S10), any produced nitrite appears to be re‐oxidized to nitrate, further reduced by denitrifiers, or used to anaerobically oxidize ammonium (anammox).…”

Section: Resultsmentioning

confidence: 99%

Microbial metabolite fluxes in a model marine anoxic ecosystem

et al. 2019

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Permanently anoxic regions in the ocean are widespread and exhibit unique microbial metabolic activity exerting substantial influence on global elemental cycles and climate. Reconstructing microbial metabolic activity rates in these regions has been challenging, due to the technical difficulty of direct rate measurements. In Cariaco Basin, which is the largest permanently anoxic marine basin and an important model system for geobiology, long‐term monitoring has yielded time series for the concentrations of biologically important compounds; however, the underlying metabolite fluxes remain poorly quantified. Here, we present a computational approach for reconstructing vertical fluxes and in situ net production/consumption rates from chemical concentration data, based on a 1‐dimensional time‐dependent diffusive transport model that includes adaptive penalization of overfitting. We use this approach to estimate spatiotemporally resolved fluxes of oxygen, nitrate, hydrogen sulfide, ammonium, methane, and phosphate within the sub‐euphotic Cariaco Basin water column (depths 150–900 m, years 2001–2014) and to identify hotspots of microbial chemolithotrophic activity. Predictions of the fitted models are in excellent agreement with the data and substantially expand our knowledge of the geobiology in Cariaco Basin. In particular, we find that the diffusivity, and consequently fluxes of major reductants such as hydrogen sulfide, and methane, is about two orders of magnitude greater than previously estimated, thus resolving a long‐standing apparent conundrum between electron donor fluxes and measured dark carbon assimilation rates.

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Section: Resultsmentioning

confidence: 99%

Microbial metabolite fluxes in a model marine anoxic ecosystem

et al. 2019

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“…Oxygen profiles showed depletion of dissolved oxygen below the plume. Remineralization of materials sinking from surface plumes has been shown to contribute to the low dissolved oxygen and high dissolved nitrate concentrations observed in Subtropical Underwater (SUW) entering the Caribbean Sea (Montes et al ., ,b). The SUW is likely strongly imprinted by the processes of remineralization of materials raining down through the water column from the Amazon River plume.…”

Section: Discussionmentioning

confidence: 99%

Amazon River water in the northeastern Caribbean Sea and its effect on larval reef fish assemblages during April 2009

Johns

Muhling

Perez

et al. 2014

Fisheries Oceanography

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During April to June 2009, a large bolus of Amazon River water impacted the northeastern Caribbean Sea. Shipboard observations collected near Saba Bank, the U.S. and British Virgin Islands, and the Anegada Passage showed low surface salinity (35.76 ± 0.05 Practical Salinity Unit (PSU)), elevated surface temperature (26.77 ± 0.14°C), high chlorophyll‐a (1.26 ± 0.21 mg m−3) and high dissolved oxygen (4.90 ± 0.06 mL L−1) in a 20‐ to 30‐m thick surface layer in the riverine plume. The water was ~1°C warmer, 1 PSU fresher, 0.3 mL L−1 higher in oxygen and 1.2 mg m−3 higher in chlorophyll‐a than Atlantic Ocean waters to the north, with Caribbean surface waters showing intermediate values. Plankton net tows obtained in the upper 100 m of the water column revealed larval fish assemblages within the plume that were significantly different from those of the surrounding waters and from those encountered in the area in previous years. The plume waters contained higher concentrations of mesopelagic fish larvae from the families Myctophidae and Nomeidae, which as adults typically inhabit offshore, deep water habitats. Concentrations of larvae from inshore and reef‐associated families such as Scaridae, Serranidae, Labridae and Clupeidae were lower than those found outside the plume in similar shallow areas, particularly in near‐surface waters. An event like the one observed in 2009 had not been documented in at least the past 30 yr, and yet it was followed by another similarly extreme event in 2010. The ecological implications, including any long‐term consequences of such recent extreme events, are important and merit further study.

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“…Denitrification dominates in this depth range as nitrate is converted to N 2 (Thunell et al, 2004;Montes et al, 2013 et al, 1963). there is the best long-term data set for the Cariaco Basin, going back to the early work of Richards and colleagues (Richards and Vaccaro, 1956;Richards, 1975 Scranton et al, 2001).…”

Section: Nutrient R Atiosmentioning

confidence: 99%