Ingestion of 15N2-labelled Trichodesmium spp. and ammonium regeneration by the harpacticoid copepod Macrosetella gracilis

O’Neil, Judith M.; Metzler, P M; Glibert, Patricia M.

doi:10.1007/bf00350763

Cited by 72 publications

(84 citation statements)

References 39 publications

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“…Actually, each of the two species is able 340 to prevail in the open ocean. It is T. erythraeum in the Coral Sea and T. thiebautii in the Caribbean 341 Sea (O'Neil et al, 1996 ), T. thiebautii in the Kuroshio area (Saino and Hattori, 1980) and the 342 Atlantic (Carpenter et al, 2004), but T. erythaeum in the north Indian Ocean (Capone et al, 1998). 343…”

Section: Trichodesmium Population Characteristics 299mentioning

confidence: 99%

Population dynamics and environmental conditions affecting Trichodesmium spp. (filamentous cyanobacteria) blooms in the south–west lagoon of New Caledonia

Rodier

Borgne²

2008

Journal of Experimental Marine Biology and Ecology

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Abstract. The present description of Trichodesmium spp. population dynamics and associated 1 environmental variables is the first one using a very short sampling interval (2-3 days). Such a 2 strategy allows a fine description of changes involving the population density and characteristics. It 3 also lends itself to interpreting those changes from past environmental conditions. During the two 4 surveys, 2 and 5 month-long, T. erythraeum dominated the Trichodesmium population, with 5 temporary occurrence of T. thiebautii and five blooms could be described. These events appeared at 6 temperatures > 24°C and followed, in all cases, nitrate, soluble reactive phosphorus and chlorophyll 7 a enrichments, with a 3-7 day time lag. Low wind speed (< 4m s -1 ) was not a prerequisite for 8Trichodesmium bloom developments as long as temperatures exceeded 26°C. As abundance 9 increased during the bloom, so did the number of filaments (trichomes) in colonies and their 10 buoyancy, leading to a clear positive biomass gradient from the bottom to the surface. A simple 11 model, using variable growth rates, showed trichome ascent would be responsible for 87-99% of 12 concentrations at 0.5m, with Trichodesmium net growth rates ranging from 0.11 to 0.38 d -1 . Finally, 13 rapid trichome density declines could be ascribed to nutrient depletion and massive surface death 14 following ascent. 15 16 17

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Section: Trichodesmium Population Characteristics 299mentioning

confidence: 99%

Population dynamics and environmental conditions affecting Trichodesmium spp. (filamentous cyanobacteria) blooms in the south–west lagoon of New Caledonia

Rodier

Borgne²

2008

Journal of Experimental Marine Biology and Ecology

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“…Trichodesmium are rarely found in sediment traps and are positively buoyant (Walsby, 1992) and so sinking appears to be a minor loss term compared with cell Published by Copernicus GmbH on behalf of the European Geosciences Union. 38 M. R. Mulholland: Fate of N and C from N 2 fixation lysis (Ohki, 1999;Hewson et al, 2004), extracellular release (Capone et al, 1994;Glibert and Bronk, 1994;Mulholland et al, 2004a), and grazing (O'Neil et al, 1996;O'Neil, 1999), each of which are discussed below. These observations suggest that material produced by diazotrophs may be primarily recycled in the surface ocean, unless there is another, as-yet unidentified pathway to export surface N fluxes due to diazotrophy to depth.…”

Section: Introductionmentioning

confidence: 99%

The fate of nitrogen fixed by diazotrophs in the ocean

2007

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Abstract. While we now know that N 2 fixation is a significant source of new nitrogen (N) in the marine environment, little is known about the fate of this N (and associated C), despite the importance of diazotrophs to global carbon and nutrient cycles. Specifically, does N fixed during N 2 fixation fuel autotrophic or heterotrophic growth and thus facilitate carbon (C) export from the euphotic zone, or does it contribute primarily to bacterial productivity and respiration in the euphotic zone? For Trichodesmium, the diazotroph we know the most about, the transfer of recently fixed N 2 (and C) appears to be primarily through dissolved pools. The release of N varies among and within populations and as a result of the changing physiological state of cells and populations. The net result of trophic transfers appears to depend on the co-occurring organisms and the complexity of the colonizing community. In order to understand the impact of diazotrophy on carbon flow and export in marine systems, we need a better understanding of the trophic flow of elements in Trichodesmium-dominated communities and other diazotrophic communities under various defined physiological states. Nitrogen and carbon fixation rates themselves vary by orders of magnitude within and among studies of Trichodesmium, highlighting the difficulty in extrapolating global rates of N 2 fixation from direct measurements. Because the stoichiometry of N 2 and C fixation does not appear to be in balance with that of particles, and the relationship between C and N 2 fixation rates is also variable, it is equally difficult to derive global rates of one from the other. This paper seeks to synthesize what is known about the fate of diazotrophic production in the environment. A better understanding of the physiology and physiological ecology of Trichodesmium and other marine diazotrophs is necessary to quantify and predict the effects of increased or decreased diazotrophy in the context of the carbon cycle and global change.

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“…Direct grazing on Trichodesmium spp. has been demonstrated for the harpacticoid copepods Macrosetella gracilis, Miracia efferata, and Oculosetella gracilis in the Caribbean (O'Neil et al, 1996;O'Neil and Roman, 1994) and Acartia tonsa in the North Atlantic (Guo and Tester, 1994). In the North Atlantic, stable isotope measured zooplankton DDN uptake suggested enhanced uptake when DDA abundance was higher than Trichodesmium spp., though the actual DDN uptake pathways could not be determined (Montoya et al, 2002).…”

mentioning

confidence: 96%

“…It is generally considered that the majority of Trichodesmium DDN reaches the food web through the release of dissolved N (Capone et al, 1994;Glibert and Bronk, 1994;Bronk, 2001, 2004) which is taken up by heterotrophic and autotrophic microbes (Bonnet et al, 2016a), and which are subsequently consumed by the zooplankton (Capone et al, 1997;O'Neil and Roman, 1992). Dissolved N is released through a combination of endogenous and exogenous processes, including viral lysis (Hewson et al, 2004), zooplankton sloppy feeding (O'Neil et al, 1996), or programmed cell death (Berman-Frank et al, 2004). Recent research has demonstrated that UCYN can release similar amounts of dissolved N to Trichodesmium (Berthelot et al, 2015a).…”

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confidence: 99%

Contribution and pathways of diazotroph-derived nitrogen to zooplankton during the VAHINE mesocosm experiment in the oligotrophic New Caledonia lagoon

et al. 2016

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Abstract. In oligotrophic tropical and subtropical oceans, where strong stratification can limit the replenishment of surface nitrate, dinitrogen (N 2 ) fixation by diazotrophs can represent a significant source of nitrogen (N) for primary production. The VAHINE (VAriability of vertical and tropHIc transfer of fixed N 2 in the south-wEst Pacific) experiment was designed to examine the fate of diazotroph-derived nitrogen (DDN) in such ecosystems. In austral summer 2013, three large (∼ 50 m 3 ) in situ mesocosms were deployed for 23 days in the New Caledonia lagoon, an ecosystem that typifies the low-nutrient, low-chlorophyll environment, to stimulate diazotroph production. The zooplankton component of the study aimed to measure the incorporation of DDN into zooplankton biomass, and assess the role of direct diazotroph grazing by zooplankton as a DDN uptake pathway. Inside the mesocosms, the diatom-diazotroph association (DDA) het-1 predominated during days 5-15 while the unicellular diazotrophic cyanobacteria UCYN-C predominated during days 15-23. A Trichodesmium bloom was observed in the lagoon (outside the mesocosms) towards the end of the experiment. The zooplankton community was dominated by copepods (63 % of total abundance) for the duration of the experiment. Using two-source N isotope mixing models we estimated a mean ∼ 28 % contribution of DDN to zooplankton nitrogen biomass at the start of the experiment, indicating that the natural summer peak of N 2 fixation in the lagoon was already contributing significantly to the zooplankton. Stimulation of N 2 fixation in the mesocosms corresponded with a generally low-level enhancement of DDN contribution to zooplankton nitrogen biomass, but with a peak of ∼ 73 % in mesocosm 1 following the UCYN-C bloom. qPCR analysis targeting four of the common diazotroph groups present in the mesocosms (Trichodesmium, het-1, het-2, UCYN-C) demonstrated that all four were ingested by copepod grazers, and that their abundance in copepod stomachs generally corresponded with their in situ abundance. 15 N 2 labelled grazing experiments therefore provided evidence for direct ingestion and assimilation of UCYN-C-derived N by the zooplankton, but not for het-1 and Trichodesmium, supporting an important role of secondary pathways of DDN to the zooplankton for the latter groups, i.e. DDN contributions to the dissolved N pool and uptake by nondiazotrophs. This study appears to provide the first evidence of direct UCYN-C grazing by zooplankton, and indicates that UCYN-C-derived N contributesPublished by Copernicus Publications on behalf of the European Geosciences Union.

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Ingestion of 15N2-labelled Trichodesmium spp. and ammonium regeneration by the harpacticoid copepod Macrosetella gracilis

Cited by 72 publications

References 39 publications

Population dynamics and environmental conditions affecting Trichodesmium spp. (filamentous cyanobacteria) blooms in the south–west lagoon of New Caledonia

Population dynamics and environmental conditions affecting Trichodesmium spp. (filamentous cyanobacteria) blooms in the south–west lagoon of New Caledonia

The fate of nitrogen fixed by diazotrophs in the ocean

Contribution and pathways of diazotroph-derived nitrogen to zooplankton during the VAHINE mesocosm experiment in the oligotrophic New Caledonia lagoon

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