GROWTH AND CARBON CONTENT OF THREE DIFFERENT‐SIZED DIAZOTROPHIC CYANOBACTERIA OBSERVED IN THE SUBTROPICAL NORTH PACIFIC<sup>1</sup>

SamplingIn order to compare the commonly used 15 N 2 tracer addition method to measure N 2 fixation 1 with the addition of 15 N 2 -enriched water as suggested by Mohr et al. (2010) 2 , seawater was sampled on two cruises in the Atlantic Ocean, the first on board R/V Meteor (M80/1) on a longitudinal transect (23°W) between 15°N and 5°S, the second on board R/V Polarstern (ANT-XXVI/1) on a transect between 54°N and 54°S (Bremerhaven, Germany to Punta Arenas, Chile). In total 39 triplicate incubations were conducted with both methods in parallel. On the M80/1 cruise, seawater was sampled at 11 stations from the surface (bucket), 20 m depth and the chlorophyll maximum (CTD rosette sampler) at 7:00 in the morning, whereas on the ANT-XXVI/1 cruise, seawater was sampled at 6 stations at 16:00 from the ship's clean seawater supply which is installed at 11 m depth (keel of the ship). IncubationsSeawater samples were filled headspace-free (bubble addition method) or with a 100-150 ml headspace (dissolved method) into 4.5 L polycarbonate bottles and closed with Teflon ® -coated butyl rubber septum caps. To determine N 2 fixation rates with the bubble-addition method, a 4.5 mL 15 N 2 gas bubble (Sigma-Aldrich, ≥98 atom%) was injected through the septa into each of triplicate bottles (yielding a theoretical enrichment of ~12 atom% assuming a rapid isotopic equilibration between the added 15 N 2 gas and the ambient dissolved N 2 of the water sample). After injection, bottles were gently inverted one hundred times. For comparison of N 2 fixation rates, we added 15 N 2 -enriched seawater to a second set of triplicate bottles (dissolution method). In detail, the preparation of the 15 N 2 -enriched seawater was started by degassing filtered seawater (0.2 µm filtered, Durapore) using a membrane flowthrough system (Mini-Module, Membrana) in which the seawater flowed on the inside of the membrane and a vacuum (-960 mbar, water jet pump) was applied to the outer side of the membrane. The seawater flow rate was about 400 -500 mL min -1 and seawater was recirculated for the first 10-15 min of the degassing step. Degassed seawater was then filled directly from the flow-through system into evacuated gas-tight 3L Tedlar® bags without a headspace. Addition of 15 N 2 gas was dependent on the amount of seawater in the Tedlar® bag and was added at a ratio of 10 ml 15 N 2 per 1L seawater. The volume of degassed seawater in SUPPLEMENTARY INFORMATION

show abstract

“…Crocosphaera were ~2 days in our incubations, which is comparable to published growth rates 29 . The different levels of 15 …”

Section: Supplementary Online Materials and Figuressupporting

confidence: 89%

Doubling of marine dinitrogen-fixation rates based on direct measurements

Großkopf

Mohr

Baustian

et al. 2012

Nature

292

319

View full text Add to dashboard Cite

show abstract

“…Additionally, Breitbarth et al (2008) find saturation of Trichodesmium IMS101 growth rates at 180 mmol quanta m 22 s 21 (albeit growth was not monitored at irradiances between 50 and 180 mmol quanta m 22 s 21 ). Neither Breitbarth et al (2008) nor Goebel et al (2008) observed photoinhibition within the range of light intensities used in our study (125-500 mmol quanta m 22 s 21 ). Based on these values for growth saturation, each of the light levels used herein is assumed to be sufficient to achieve maximal growth rates.…”

Section: Methodsmentioning

confidence: 45%

“…The light levels used herein (. 125 mmol quanta m 22 s 21 ), the saturation parameters for growth reported by Goebel et al (2008;73 6 29 mmol quanta m 22 s 21 ) and Breitbarth et al (2008), and the statistically similar C fixation rates observed for cultures with similar prior nutritional history indicate that these experiments were all maintained at saturating irradiances. Thus, we can conclude that Trichodesmium IMS101 in well-lit, DIP-deficient conditions can sustain growth rates similar to those achieved with DIP alone via the hydrolysis of P bound in G6P, AMP, MPn, and 2-AEP.…”

Section: Resultsmentioning

confidence: 58%

“…Experiments II and III were grown under a 12 : 12 light : dark (LD) cycle with fixed irradiances of 125 and 325 mmol quanta m 22 s 21 , respectively (Table 1). Goebel et al (2008) report the light saturation parameter of the growth vs. irradiance curve for Trichodesmium IMS101 to be 73 6 29 mmol quanta m 22 s 21 . Additionally, Breitbarth et al (2008) find saturation of Trichodesmium IMS101 growth rates at 180 mmol quanta m 22 s 21 (albeit growth was not monitored at irradiances between 50 and 180 mmol quanta m 22 s 21 ).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Phosphonate metabolism by Trichodesmium IMS101 and the production of greenhouse gases

White

Karl

Björkman

et al. 2010

Limnology & Oceanography

View full text Add to dashboard Cite

Herein we present the results of a series of laboratory experiments conducted to delineate the relationship between dissolved organic phosphorus (DOP) utilization and organic matter production by the model diazotroph Trichodesmium IMS101. The rate and ratio of Trichodesmium carbon (C) and nitrogen (N) production driven by phosphorus (P) derived from select phosphonates and P monoesters were not found to be significantly different than growth rates based on dissolved inorganic phosphorus (DIP). Conversely, despite the observed similarities in C and N fixation rates between parallel DIP and DOP incubations, cultures grown solely on methylphosphonate (MPn) had reduced maximal P content per unit chlorophyll a or C relative to cultures grown on P monoesters or DIP. So while Trichodesmium IMS101 appears to be able to maintain similar rates of growth on DIP and select DOP substrates, the P uptake efficiency and, hence, the P content per cell is greater for growth on DIP or tested P monoesters relative to growth on the phosphonate MPn. The primary conclusion arising from these results is that neither the observation of P monoester hydrolysis nor highly P-deficient organic matter or expression of phosphonate hydrolyzing genes can be interpreted to indicate P limitation of C or N fixation of Trichodesmium spp. under light-saturated, DIP-deficient conditions.

show abstract

“…So far, three groups of unicellular diazotrophic cyanobacteria (UCYN) have been reported in the literature, UCYN-A, B, and C (Zehr et al, 2001;Foster et al, 2007). While UCYN-B and C are nanoplanktonic cells (2 to 10 µm) closely affiliated to the cultivated strains Crocosphaera watsonii and Cyanothece sp., respectively (Church et al, 2005a;Foster et al, 2007), UCYN-A are of picoplanktonic size (0.7-1.5 µm, Biegala and Raimbault, 2008;Goebel et al, 2008) and so far uncultivated. In addition to being freeliving, UCYN have also been suggested to produce mucilage, to attach to inert particles or to live in association with planktonic eukaryotes (Biegala and Raimbault, 2008;Bonnet et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Intriguing diversity among diazotrophic picoplankton along a Mediterranean transect: a dominance of rhizobia

2011

View full text Add to dashboard Cite

Abstract. The Mediterranean Sea is one of the most oligotrophic marine areas on earth where nitrogen fixation has formally believed to play an important role in carbon and nitrogen fluxes. Although this view is under debate, the diazotrophs responsible for this activity have still not been investigated in the open sea. In this study, we characterised the surface distribution and species richness of unicellular and filamentous diazotrophs across the Mediterranean Sea by combining microscopic counts with size fractionated in situ hybridization (TSA-FISH), and 16S rDNA and nifH genes phylogenies. These genetic analyses were possible owing to the development of a new PCR protocol adapted to scarce microorganisms that can detect as few as 1 cell ml −1 in cultures. Low concentrations of diazotrophic cyanobacteria were detected and this community was dominated at 99.9% by picoplankton hybridized to the Nitro821 probe, specific for unicellular diazotrophic cyanobacteria (UCYN). Among filamentous cyanobacteria only 0.02 filament ml −1 of Richelia were detected in the eastern basin, while small (0.7-1.5 µm) and large (2.5-3.2 µm) Nitro821-targeted cells were recovered at all stations with a mean concentration of 3.5 cell ml −1 . The affiliation of the small Nitro821-targeted cells to UCYN-A was confirmed by 16S and nifH phylogenies in the western Mediterranean Sea. In the central and the eastern Mediterranean Sea no 16S rDNA and nifH sequence from UCYN was obtained as cells concentration were close to, or below PCR detection limit. Bradyrhizobium sequences dominated nifH clone libraries from picoplanktonic size fractions. A few sequences of γ -proteobacteria were also detected in the central Mediterranean Sea. While low phosphate and iron concentrations could explain the absence of Trichodesmium sp., the factors that prevent the developCorrespondence to: I. C. Biegala (biegala@univmed.fr) ment of UCYN-B and C remain unknown. We also propose that the dominating picoplankters probably developed specific strategies, such as associations with protists or particles, and/or photosynthetic activity, to acquire carbon for sustaining diazotrophy.

show abstract

GROWTH AND CARBON CONTENT OF THREE DIFFERENT‐SIZED DIAZOTROPHIC CYANOBACTERIA OBSERVED IN THE SUBTROPICAL NORTH PACIFIC¹

Cited by 74 publications

References 63 publications

Doubling of marine dinitrogen-fixation rates based on direct measurements

Doubling of marine dinitrogen-fixation rates based on direct measurements

Phosphonate metabolism by Trichodesmium IMS101 and the production of greenhouse gases

Intriguing diversity among diazotrophic picoplankton along a Mediterranean transect: a dominance of rhizobia

Contact Info

Product

Resources

About

GROWTH AND CARBON CONTENT OF THREE DIFFERENT‐SIZED DIAZOTROPHIC CYANOBACTERIA OBSERVED IN THE SUBTROPICAL NORTH PACIFIC1

Cited by 74 publications

References 63 publications

Doubling of marine dinitrogen-fixation rates based on direct measurements

Doubling of marine dinitrogen-fixation rates based on direct measurements

Phosphonate metabolism by Trichodesmium IMS101 and the production of greenhouse gases

Intriguing diversity among diazotrophic picoplankton along a Mediterranean transect: a dominance of rhizobia

Contact Info

Product

Resources

About

GROWTH AND CARBON CONTENT OF THREE DIFFERENT‐SIZED DIAZOTROPHIC CYANOBACTERIA OBSERVED IN THE SUBTROPICAL NORTH PACIFIC¹