Iron Stimulation of Photosynthesis and Nitrogen Fixation in Anabaena 7120 and Trichodesmium (Cyanophyceae)

Rueter, John G.

doi:10.1111/j.1529-8817.1988.tb00084.x

Cited by 77 publications

(55 citation statements)

References 32 publications

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“…It is possible that colonies were seasonally limited in an essential nutrient s u c h as iron (Martin & Fitzwater 1988). Trichodesmium h a s a high iron requirement since this e l e m e n t is n e e d e d for synthesis of nitrog e n a s e (Rueter 1988, Rueter e t al. 1992).…”

Section: Discussionmentioning

confidence: 99%

The marine planktonic cyanobacteria Trichodesmium spp.: photosynthetic rate measurements in the SW Atlantic Ocean

Carpenter¹,

Roenneberg²

1995

Mar. Ecol. Prog. Ser.

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Rates of photosynthesis of the diazotrophic marine cyanobacteria Trichodesmium spp.were measured with an O2 electrode on 4 cruises to the Bahama Islands and the eastern Caribbean Sea.These phytoplankters had a relatively high light requirement, with Ik (irradiance saturation parameter) values ranging from 142 to 295 pm01 m-2 S-' photon flux and a compensation irradiance of between 96 and 134 pm01 m-? S-' Thus the compensation depth for Trichodesmium spp. is usually between about 70 and 85 m in the study area. Trichodesmium spp. had a high dark respiration rate, and this is the major cause of the high compensation irradiance. Because Tn'chodesmium spp, have gas ves~cles, they are buoyant, and the population maxima are typically found at 15 m, approximately 50 % of I, (incident surface irradiance). Thus for most of the day they almost always receive saturating irradiances. The mean P, , , , , values were 44.7 (January-February 1992), 8.29 (September 1992), and 6.45 (SeptemberOctober 1992) mg O2 m g -' chl a h-'. A calibration with 14C gave a very low photosynthetlc quotlent (PQ) whlch averaged 0.46 and 0.61 on 2 cruises. This could have been because of 0, consumption from high RUBISCO oxygenase activity, and this may play a role in protection of nitrogenase from oxygen deactivation. Based on a mean PQ of 0.53, Trichodesmium spp. carbon turnover times for the 3 cruises were 0.93, 7.8, and 6.13 d, thus indicating relatively rapid growth rates for the population.

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Section: Discussionmentioning

confidence: 99%

The marine planktonic cyanobacteria Trichodesmium spp.: photosynthetic rate measurements in the SW Atlantic Ocean

Carpenter¹,

Roenneberg²

1995

Mar. Ecol. Prog. Ser.

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“…It has been suggested that N 2 fixation by marine diazotrophs including Trichodesmium in these regions often is limited by Fe availability (9,44,45). According to our results, as the ocean acidifies, the dual effects of decreasing pH on Fe availability and on N 2 fixation by Trichodesmium may act synergistically to result in a sizable decline in new N input to oligotrophic waters, given that this organism is estimated to contribute a large fraction of contemporary oceanic N 2 fixation (7).…”

Section: Discussionmentioning

confidence: 99%

Ocean acidification slows nitrogen fixation and growth in the dominant diazotroph Trichodesmium under low-iron conditions

Shi

Kranz

Kim

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

111

104

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Dissolution of anthropogenic CO 2 increases the partial pressure of CO 2 (pCO 2 ) and decreases the pH of seawater. The rate of Fe uptake by the dominant N 2 -fixing cyanobacterium Trichodesmium declines as pH decreases in metal-buffered medium. The slower Fe-uptake rate at low pH results from changes in Fe chemistry and not from a physiological response of the organism. Contrary to previous observations in nutrient-replete media, increasing pCO 2 /decreasing pH causes a decrease in the rates of N 2 fixation and growth in Trichodesmium under low-Fe conditions. This result was obtained even though the bioavailability of Fe was maintained at a constant level by increasing the total Fe concentration at low pH. Short-term experiments in which pCO 2 and pH were varied independently showed that the decrease in N 2 fixation is caused by decreasing pH rather than by increasing pCO 2 and corresponds to a lower efficiency of the nitrogenase enzyme. To compensate partially for the loss of N 2 fixation efficiency at low pH, Trichodesmium synthesizes additional nitrogenase. This increase comes partly at the cost of down-regulation of Fe-containing photosynthetic proteins. Our results show that although increasing pCO 2 often is beneficial to photosynthetic marine organisms, the concurrent decreasing pH can affect primary producers negatively. Such negative effects can occur both through chemical mechanisms, such as the bioavailability of key nutrients like Fe, and through biological mechanisms, as shown by the decrease in N 2 fixation in Fe-limited Trichodesmium.climate change | cyanobacteria | iron limitation A bout one-third of the anthropogenic CO 2 released into the atmosphere dissolves into the surface ocean, increasing the partial pressure of CO 2 , pCO 2 , and lowering the pH. This ocean acidification has been shown to have various consequences for marine phytoplankton (1-5). Organisms that invest a large amount of energy in the operation of a carbon-concentrating mechanism (CCM) are expected to be particularly sensitive to changes in pCO 2 . This is the case for marine cyanobacteria, which must elevate the CO 2 concentration at the site of carbon fixation as a result of the poor affinity for CO 2 of their carboxylating enzyme, ribulose bisphosphate carboxylase oxygenase (RubisCO) (6). Of particular interest is the effect of ocean acidification on the N 2 -fixing filamentous cyanobacterium Trichodesmium, which is responsible for a major fraction of all marine N 2 fixation and thus plays a prominent role in the biogeochemical cycling of C and N (7). This bloom-forming diazotroph thrives throughout the oligotrophic tropical and subtropical oceans where P and/or Fe often limit its growth and N 2 fixation (8-10).In the past few years, the effects of ocean acidification on Trichodesmium have been studied extensively in combination with those of other environmental variables, such as temperature, light intensity, and phosphorus limitation. Stimulation of N 2 fixation and growth at elevated pCO 2 has been observed in both la...

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“…Indeed, there is experimental evidence that Fe can regulate Trichodesmium growth and nitrogenase activity. Rueter (1988) found increases in CO 2 and N 2 fixation rates and cellular chlorophyll a content in natural samples of Trichodesmium collected near Barbados when amended with Fe. Similarly, Paerl and others (1994) reported stimulation of growth and nitrogenase activity by Fe in cultures and natural samples of Trichodesmium.…”

Section: Of Marine N 2 Fixationmentioning

confidence: 99%

The conundrum of marine N2 fixation

Mahaffey¹

2005

American Journal of Science

240

231

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On a basin and global scale, iron (Fe) and P are thought to be primary chemical factors limiting N 2 fixation. The climatological and biological forcings, which individually or cumulatively promote diazotroph growth or trigger blooms, are still poorly understood. Improvements in coupled biological-physical and ecosystem models have allowed for the explicit representation of diazotrophs and, in particular, Trichodesmium and thus hold great potential for unraveling the factors that constrain diazotroph distribution and growth.The role of N 2 fixation in both the global N and C cycle, through both the inter-glacial and glacial cycles as well in the present day ocean, remains an open question. The emerging body of data on global rates of denitrification implies that the oceans are losing nitrate rapidly and, if true, either the rates of N 2 fixation are even higher than we currently estimate or, on some time-scale, the total stock of nitrate in the oceans is more variable than expected. Each of these outcomes has direct implications for the air-sea partitioning of CO 2 on climate time-scales. The question remains: does the importance of marine N 2 fixation relative to denitrification oscillate over various timescales in response to climate forcing or is the N cycle in a homeostatic steady state?

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Iron Stimulation of Photosynthesis and Nitrogen Fixation in Anabaena 7120 and Trichodesmium (Cyanophyceae)

Cited by 77 publications

References 32 publications

The marine planktonic cyanobacteria Trichodesmium spp.: photosynthetic rate measurements in the SW Atlantic Ocean

The marine planktonic cyanobacteria Trichodesmium spp.: photosynthetic rate measurements in the SW Atlantic Ocean

Ocean acidification slows nitrogen fixation and growth in the dominant diazotroph Trichodesmium under low-iron conditions

The conundrum of marine N2 fixation

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