Nitrogen fixation within the water column associated with two hypoxic basins in the Southern California Bight

Hamersley, M. Robert; Turk, Kendra A.; Leinweber, A.; Gruber, Nicolas; Zehr, Jonathan P.; Gunderson, Troy; Capone, Douglas G.

doi:10.3354/ame01494

Cited by 125 publications

(161 citation statements)

References 46 publications

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“…The population in this study was dominated by one nifH phylotype that has been detected in several oceans, including the Atlantic (Langlois et al, 2005), South China Sea (Moisander et al, 2008;Bombar et al, 2011), North Pacific (Church et al, 2005) and Red Sea (Foster et al, 2009). Additional closely related phylotypes were detected in this study, in the North Pacific (Fong et al, 2008), Arabian Sea (Bird et al, 2005), Mediterranean Sea (Man-Aharonovich et al, 2007) and Southern California Bight (Hamersley et al, 2011). The presence of nifH sequences as PCR reagent contaminants has been reported (Zehr et al, 2003a;Bostrom et al, 2007), and frequently the same groups within alphaproteobacteria have been reported as contaminants.…”

Section: Diversitymentioning

confidence: 79%

“…Similarly to this study, a study in the Southern California Bight (Hamersley et al, 2011) suggested primarily a surface association for g-24774A11, while the phylotype was detected down to 300 m in the Arabian Sea (Bird et al, 2005). Surface-associated groups such as g-24774A11 could supplement their energy from light directly through rhodopsin or bacteriochlorophyll-based metabolisms.…”

Section: Abundance Of G-24774a11mentioning

confidence: 89%

“…The most significant N 2 -fixing microorganisms in the ocean are thought to be the cyanobacteria Trichodesmium (Capone et al, 1997), symbiotic and free-living unicellular cyanobacteria (UCYN, including Crocosphaera) Montoya et al, 2004), and filamentous symbionts (of the order Nostocales) that associate with diatoms (Villareal, 1994;Carpenter et al, 1999). Molecular surveys from various marine environments have also recovered a high diversity of nifH genes that cluster with non-cyanobacterial bacteria (Zehr et al, 2003b) in surface waters and even below the epipelagic zone in the open ocean (Langlois et al, 2005;Hewson et al, 2007;Hamersley et al, 2011;Halm et al, 2012). The diazotrophic bacteria that have been obtained from open ocean epipelagic seawater cluster with a wide range of bacterial groups, including alpha-, beta-, gamma-and deltaproteobacteria and Firmicutes (Zehr et al, , 2003b.…”

Section: Introductionmentioning

confidence: 99%

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Gammaproteobacterial diazotrophs and nifH gene expression in surface waters of the South Pacific Ocean

et al. 2014

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In addition to the cyanobacterial N2-fixers (diazotrophs), there is a high nifH gene diversity of non-cyanobacterial groups present in marine environments, yet quantitative information about these groups is scarce. N2 fixation potential (nifH gene expression), diversity and distributions of the uncultivated diazotroph phylotype γ-24774A11, a putative gammaproteobacterium, were investigated in the western South Pacific Ocean. γ-24774A11 gene copies correlated positively with diazotrophic cyanobacteria, temperature, dissolved organic carbon and ambient O2 saturation, and negatively with depth, chlorophyll a and nutrients, suggesting that carbon supply, access to light or inhibitory effects of DIN may control γ-24774A11 abundances. Maximum nifH gene-copy abundance was 2 × 104 l−1, two orders of magnitude less than that for diazotrophic cyanobacteria, while the median γ-24774A11 abundance, 8 × 102 l−1, was greater than that for the UCYN-A cyanobacteria, suggesting a more homogeneous distribution in surface waters. The abundance of nifH transcripts by γ-24774A11 was greater during the night than during the day, and the transcripts generally ranged from 0–7%, but were up to 26% of all nifH transcripts at each station. The ubiquitous presence and low variability of γ-24774A11 abundances across tropical and subtropical oceans, combined with the consistent nifH expression reported in this study, suggest that γ-24774A11 could be one of the most important heterotrophic (or photoheterotrophic) diazotrophs and may need to be considered in future N budget estimates and models.

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Section: Diversitymentioning

confidence: 79%

Section: Abundance Of G-24774a11mentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Gammaproteobacterial diazotrophs and nifH gene expression in surface waters of the South Pacific Ocean

et al. 2014

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“…Unicellular diazotrophs were also reported at high abundances from coastal lagoons in Australia and New Caledonia Biegala and Raimbault, 2008). An uncultivated g-Proteobacterium g-24774A11, named after a nifH clone recovered from the South China Sea (Moisander et al, 2008), is widespread in tropical oceans (Church et al, 2005a;Hamersley et al, 2011;Turk et al, 2011). g-24774A11 expressed nifH in previous studies (Bird et al, 2005;Church et al, 2005b) and in our study area (Moisander et al, unpublished data) suggesting it is contributing to oceanic N 2 fixation, however its ecophysiology is poorly characterized to date.…”

Section: Introductionmentioning

confidence: 92%

Analogous nutrient limitations in unicellular diazotrophs and Prochlorococcus in the South Pacific Ocean

et al. 2011

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Growth limitation of phytoplankton and unicellular nitrogen (N2) fixers (diazotrophs) were investigated in the oligotrophic Western South Pacific Ocean. Based on change in abundances of nifH or 23S rRNA gene copies during nutrient-enrichment experiments, the factors limiting net growth of the unicellular diazotrophs UCYN-A (Group A), Crocosphaera watsonii, γ-Proteobacterium 24774A11, and the non-diazotrophic picocyanobacterium Prochlorococcus, varied within the region. At the westernmost stations, numbers were enhanced by organic carbon added as simple sugars, a combination of iron and an organic chelator, or iron added with phosphate. At stations nearest the equator, the nutrient-limiting growth was not apparent. Maximum net growth rates for UCYN-A, C. watsonii and γ-24774A11 were 0.19, 0.61 and 0.52 d−1, respectively, which are the first known empirical growth rates reported for the uncultivated UCYN-A and the γ-24774A11. The addition of N enhanced total phytoplankton biomass up to 5-fold, and the non-N2-fixing Synechococcus was among the groups that responded favorably to N addition. Nitrogen was the major nutrient-limiting phytoplankton biomass in the Western South Pacific Ocean, while availability of organic carbon or iron and organic chelator appear to limit abundances of unicellular diazotrophs. Lack of phytoplankton response to nutrient additions in the Pacific warm pool waters suggests diazotroph growth in this area is controlled by different factors than in the higher latitudes, which may partially explain previously observed variability in community composition in the region.

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“…SPOT's surface shows seasonal environmental and biological patterns, relationships between microbial communities and biotic and abiotic parameters, and a prevalence of putative interactions between microbes, all of which likely influence community structure Fuhrman and Steele, 2008;Steele et al, 2011;Needham et al, 2013;Chow et al, 2013Chow et al, , 2014. The physical and chemical environment at SPOT is regularly sampled, and previous work has identified seasonal and other scales of variability in particle flux (Collins et al, 2011), nutrient availability and biogeochemistry (Hamersley et al, 2011) and turnover of water within the San Pedro Basin (Berelson, 1991). This physiochemical and surface-biological information provides a useful background for understanding the temporal dynamics of bacteria throughout the water column.…”

Section: Introductionmentioning

confidence: 99%

Seasonal and interannual variability of the marine bacterioplankton community throughout the water column over ten years

et al. 2014

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Microbial activities that affect global oceanographic and atmospheric processes happen throughout the water column, yet the long-term ecological dynamics of microbes have been studied largely in the euphotic zone and adjacent seasonally mixed depths. We investigated temporal patterns in the community structure of free-living bacteria, by sampling approximately monthly from 5 m, the deep chlorophyll maximum (B15-40 m), 150, 500 and 890 m, in San Pedro Channel (maximum depth 900 m, hypoxic below B500 m), off the coast of Southern California. Community structure and biodiversity (inverse Simpson index) showed seasonal patterns near the surface and bottom of the water column, but not at intermediate depths. Inverse Simpson's index was highest in the winter in surface waters and in the spring at 890 m, and varied interannually at all depths. Biodiversity appeared to be driven partially by exchange of microbes between depths and was highest when communities were changing slowly over time. Meanwhile, communities from the surface through 500 m varied interannually. After accounting for seasonality, several environmental parameters co-varied with community structure at the surface and 890 m, but not at the intermediate depths.Abundant and seasonally variable groups included, at 890 m, Nitrospina, Flavobacteria and Marine Group A. Seasonality at 890 m is likely driven by variability in sinking particles, which originate in surface waters, pass transiently through the middle water column and accumulate on the seafloor where they alter the chemical environment. Seasonal subeuphotic groups are likely those whose ecology is strongly influenced by these particles. This surface-to-bottom, decade-long, study identifies seasonality and interannual variability not only of overall community structure, but also of numerous taxonomic groups and near-species level operational taxonomic units.

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Nitrogen fixation within the water column associated with two hypoxic basins in the Southern California Bight

Cited by 125 publications

References 46 publications

Gammaproteobacterial diazotrophs and nifH gene expression in surface waters of the South Pacific Ocean

Gammaproteobacterial diazotrophs and nifH gene expression in surface waters of the South Pacific Ocean

Analogous nutrient limitations in unicellular diazotrophs and Prochlorococcus in the South Pacific Ocean

Seasonal and interannual variability of the marine bacterioplankton community throughout the water column over ten years

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