Importance of the diazotrophs as a source of new nitrogen in the ocean

LaRoche, Julie; Breitbarth, Eike

doi:10.1016/j.seares.2004.05.005

Cited by 245 publications

(267 citation statements)

References 131 publications

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“…The m max measured by Goebel et al (in revision) and used to parameterize growth rates of Trichodesmium in this study was more than double the rates reported in the literature review of LaRoche and Breitbarth (2005) and that recorded by Breitbarth et al (2007). However, the Goebel et al (in revision) rates for both Trichodesmium and Crocosphaera agreed with those of Tuit et al (2004).…”

Section: Discussionsupporting

confidence: 52%

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Modeled contributions of three types of diazotrophs to nitrogen fixation at Station ALOHA

et al. 2007

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A diagnostic model based on biomass and growth was used to assess the relative contributions of filamentous nonheterocystous Trichodesmium and unicellular cyanobacteria, termed Groups A and B, to nitrogen fixation at the North Pacific Station ALOHA over a 2-year period. Average (and 95% confidence interval, CI) annual rates of modeled monthly values for Trichodesmium, Group B and Group A were 92 (52), 14 (4) and 12 (8) mmol N per m 2 per year, respectively. The fractional contribution to modeled instantaneous nitrogen fixation by each diazotroph fluctuated on interannual, seasonal and shorter time scales. Trichodesmium fixed substantially more nitrogen in year 1 (162) than year 2 (12). Group B fixed almost two times more nitrogen in year 1 (17) than year 2 (9). In contrast, Group A fixed two times more nitrogen in year 2 (16) than year 1 (8). When including uncertainties in our estimates using the bootstrap approach, the range of unicellular nitrogen fixation extended from 10% to 68% of the total annual rate of nitrogen fixation for all three diazotrophs. Furthermore, on a seasonal basis, the model demonstrated that unicellular diazotrophs fixed the majority (51%-97%) of nitrogen during winter and spring, whereas Trichodesmium dominated nitrogen fixation during summer and autumn (60%-96%). Sensitivity of the modeled rates to some parameters suggests that this unique attempt to quantify relative rates of nitrogen fixation by different diazotrophs may need to be reevaluated as additional information on cell size, variability in biomass and C:N, and growth characteristics of the different cyanobacterial diazotrophs become available.

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Section: Discussionsupporting

confidence: 52%

“…LaRoche and Breitbarth (2005) reported Trichodesmium molar C:N ratios ranged between 4.7 and 7.3, averaging 6.3. This range encompassed C:N ratio measurements of natural (5.6-7.3; Carpenter et al, 2004 and 6.6;see Orcutt et al, 2001) and cultivated (6.27s.d.…”

Section: Carbon Content a Volumetric Carbon Content Formentioning

confidence: 98%

Modeled contributions of three types of diazotrophs to nitrogen fixation at Station ALOHA

et al. 2007

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“…8d) were similar to the C : Fe ratios reported for L. majuscula in other studies in Deception Bay: 99.4 in 1999-2000(Watkinson et al 2005) and 131-148 in 2005). All these values were within the range or slightly higher than the C : Fe ratios for the marine diazotrophs cyanoabacterium Trichodesmuim (commonly C : Fe ratios between 20-125 in culture) (La Roche and Breitbarth 2005). However, L. majuscula in Eastern Moreton Bay had much higher C : Fe ratios (252-262) than the L. majuscula from Deception Bay (which is geographically closer to iron and organic sources than Eastern Moreton Bay) and more within the range recorded for nondiazotrophs such as diatoms (143-1000) (Sunda and Huntsman 1997).…”

Section: Tissue Nutrient Content and Changesmentioning

confidence: 58%

Mapping the distribution, biomass and tissue nutrient levels of a marine benthic cyanobacteria bloom (Lyngbya majuscula)

Ahern

Ahern²,

Savige³

et al. 2007

Mar. Freshwater Res.

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Abstract. Benthic cyanobacteria blooms, including those of the nitrogen-fixing species Lyngbya majuscula, appear to be becoming more numerous and widespread in marine habitats worldwide, and have negative impacts on the environment and human health. The progression of a L. majuscula bloom in south-east Queensland, Australia was mapped along with intensive biomass and tissue nutrient sampling every 10-14 days over the bloom's 3.5-month duration in summer [2005][2006]. Data-integrated GIS maps illustrated the changes in biomass and tissue nutrient pool of the L. majuscula through different growth phases (incipient, rapid expansion, plateau or peak and decline) of the bloom. At the peak, L. majuscula covered 509 ha and had a mean density of 115 g dw m −2 , with the maximum density recorded 503 g dw m −2 . The highest mean total carbon (29.4% C), nitrogen (3.5% N) and phosphorus (0.143% P) contents in L. majuscula tissue corresponded with the peak in biomass. Three-dimensional modelling calculated that at the peak, the bloom contained 5057 t ww (510 t dw ) of L. majuscula; 150 000 kg C; 18 000 kg N; 720 kg P; and 5200 kg Fe. This information gives an insight into L. majuscula bloom dynamics and ecophysiology and provides quantitative data for models.

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“…The fixation of N 2 is a particularly important source of nitrogen in marine habitats, yet few N 2 -fixing cyanobacteria are found in the oligotrophic open ocean (Howarth et al, 1988;Michaels et al, 1996;Karl et al, 2002;Stal and Zehr, 2008). The free-living bloom-forming filamentous cyanobacterium Trichodesmium (Capone et al, 1997;LaRoche and Breitbarth, 2005) and the heterocystous Richelia symbionts of marine pelagic diatoms (Villareal, 1992;Foster and Zehr, 2006) were believed to be the primary N 2 -fixers (diazotrophs) until the discovery that the unicellular N 2 -fixing cyanobacteria were also generally widespread and important in N 2 -fixation in the open ocean (Zehr et al, 2001;Falcón et al, 2002;Mazard et al, 2004;Montoya et al, 2004;Langlois et al, 2005). One of these unicellular cyanobacterial species, Crocosphaera watsonii strain WH 8501 (C. watsonii), had previously been isolated from tropical waters (Waterbury and Rippka, 1989).…”

Section: Introductionmentioning

confidence: 99%

Genome-wide analysis of diel gene expression in the unicellular N2-fixing cyanobacterium Crocosphaera watsonii WH 8501

et al. 2010

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The unicellular cyanobacterium Crocosphaera watsonii is an important nitrogen fixer in oligotrophic tropical and subtropical oceans. Metabolic, energy and cellular processes in cyanobacteria are regulated by the circadian mechanism, and/or follow the rhythmicity of light-dark cycles. The temporal separation of metabolic processes is especially essential for nitrogen fixation because of inactivation of the nitrogenase by oxygen. Using a microarray approach, we analyzed gene expression in cultures of Crocosphaera watsonii WH 8501 (C. watsonii) over a 24-h period and compared the whole-genome transcription with that in Cyanothece sp. ATCC 51142 (Cyanothece), a unicellular diazotroph that inhabits coastal marine waters. Similar to Cyanothece, regulation at the transcriptional level in C. watsonii was observed for all major metabolic and energy processes including photosynthesis, carbohydrate and amino acid metabolisms, respiration, and nitrogen fixation. Increased transcript abundance for iron acquisition genes by the end of the day appeared to be a general pattern in the unicellular diazotrophs. In contrast, genes for some ABC transporters (for example, phosphorus acquisition), DNA replication, and some genes encoding hypothetical proteins were differentially expressed in C. watsonii only. Overall, C. watsonii showed a higher percentage of genes with light-dark cycling patterns than Cyanothece, which may reflect the habitats preferences of the two cyanobacteria. This study represents the first whole-genome expression profiling in cultivated Crocosphaera, and the results will be useful in determining the basal physiology and ecology of the endemic Crocosphaera populations.

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Importance of the diazotrophs as a source of new nitrogen in the ocean

Cited by 245 publications

References 131 publications

Modeled contributions of three types of diazotrophs to nitrogen fixation at Station ALOHA

Modeled contributions of three types of diazotrophs to nitrogen fixation at Station ALOHA

Mapping the distribution, biomass and tissue nutrient levels of a marine benthic cyanobacteria bloom (Lyngbya majuscula)

Genome-wide analysis of diel gene expression in the unicellular N2-fixing cyanobacterium Crocosphaera watsonii WH 8501

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