Gross community production and metabolic balance in the South Pacific Gyre, using a non intrusive bio-optical method

Abstract. The very clear waters of the South Pacific Gyre likely constitute an end-member of oligotrophic conditions which remain essentially unknown with respect to its impact on carbon fixation and exportation. We describe a non-intrusive bio-optical method to quantify the various terms of a production budget (Gross community production, community losses, net community production) in this area. This method is based on the analysis of the diel cycle in Particulate Organic Carbon (POC), derived from high frequency measurements of the particle attenuation coefficient cp. We report very high integrated rates of Gross Community Production within the euphotic layer (average of 846±484 mg C m−2 d−1 for 17 stations) that are far above any rates determined using incubation techniques for such areas. Furthermore we show that the daily production of POC is essentially balanced by the losses so that the system cannot be considered as net heterotrophic. Our results thus agree well with geochemical methods, but not with incubation studies based on oxygen methods. We stress to the important role of deep layers, below the euphotic layer, in contributing to carbon fixation when incident irradiance at the ocean surface is high (absence of cloud coverage). These deep layers, not considered up to know, might fuel part of the heterotrophic processes in the upper layer, including through dissolved organic carbon. We further demonstrate that, in these extremely clear and stratified waters, integrated gross community production is proportional to the POC content and surface irradiance via an efficiency index ψ GCP*, the water column cross section for Gross Community Production. We finally discuss our results in the context of the role of oligotrophic gyre in the global carbon budget and of the possibility of using optical proxies from space for the development of growth community rather than primary production global models.

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Gross community production and metabolic balance in the South Pacific Gyre, using a non intrusive bio-optical method

Biogeosciences Discussions ◽

10.5194/bgd-4-3089-2007 ◽

2007 ◽

Vol 4 (5) ◽

pp. 3089-3121 ◽

Cited By ~ 13

Author(s):

H. Claustre ◽

Y. Huot ◽

I. Obernosterer ◽

B. Gentili ◽

D. Tailliez ◽

...

Keyword(s):

Organic Carbon ◽

Optical Method ◽

Carbon Fixation ◽

South Pacific ◽

The South ◽

Euphotic Layer ◽

Deep Layers ◽

South Pacific Gyre ◽

Community Production

Abstract. The very clear waters of the South Pacific Gyre likely constitute an end-member of oligotrophic conditions which remain essentially unknown with respect to its impact on carbon fixation and exportation. We describe a non-intrusive bio-optical method to quantify the various terms of a production budget (Gross Community Production, community losses, net community production) in this area. This method is based on the analysis of the diel cycle in Particulate Organic Carbon (POC), derived from high frequency measurements of the particle attenuation coefficient cp. We report very high integrated rates of Gross Community Production within the euphotic layer (average of 846±484 mg C m−2 d−1 for 17 stations) that are far above any rates determined using incubation techniques for such areas. Furthermore we show that the daily production of POC is essentially balanced by the losses so that the system cannot be considered as net heterotoph. Our results thus agree well with geochemical methods, but not with incubation studies based on oxygen methods. We stress to the important role of deep layers, below the euphotic layer, in contributing to carbon fixation when incident irradiance at the ocean surface is high (absence of cloud coverage). These deep layers, not considered up to now, might fuel a part of the heterotrophic processes in the upper layer, in particular through dissolved organic carbon release. We further demonstrate that, in these extremely clear and stratified waters, integrated Gross Community Production is proportional to the POC content and surface irradiance via an efficiency index ψGCP*, the water column cross section for Gross Community Production. We finally discuss our results in the context of the role of oligotrophic gyre in global carbon budget and of the possibility of using optical proxy from space for the development of gross community rather than primary production global models.

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Literary Histories

10.1093/oso/9780199679775.003.0038 ◽

2018 ◽

Author(s):

Eva-Marie Kröller

Keyword(s):

New Zealand ◽

Collective Identity ◽

Literary History ◽

English Language ◽

South Pacific ◽

The South ◽

Cultural Elite ◽

Historical Methodology ◽

Literary Histories

This chapter discusses national literary histories in Australia, Canada, New Zealand, and the South Pacific and summarises the book's main findings regarding the construction and revision of narratives of national identity since 1950. In colonial and postcolonial cultures, literary history is often based on a paradox that says much about their evolving sense of collective identity, but perhaps even more about the strains within it. The chapter considers the complications typical of postcolonial literary history by focusing on the conflict between collective celebration and its refutation. It examines three issues relating to the histories of English-language fiction in Australia, Canada, New Zealand, and the South Pacific: problems of chronology and beginnings, with a special emphasis on Indigenous peoples; the role of the cultural elite and the history wars in the Australian context; and the influence of postcolonial networks on historical methodology.

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Distribution of inorganic and organic nutrients in the South Pacific Ocean − evidence for long-term accumulation of organic matter in nitrogen-depleted waters

Biogeosciences ◽

10.5194/bg-5-281-2008 ◽

2008 ◽

Vol 5 (2) ◽

pp. 281-298 ◽

Cited By ~ 83

Author(s):

P. Raimbault ◽

N. Garcia ◽

F. Cerutti

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Dissolved Organic Matter ◽

Dissolved Organic Carbon ◽

Chlorophyll A ◽

Organic Phosphorus ◽

South Pacific ◽

Nutrient Concentrations ◽

The South ◽

Photic Layer

Abstract. During the BIOSOPE cruise the RV Atalante was dedicated to study the biogeochemical properties in the South Pacific between the Marquesas Islands (141° W–8° S) and the Chilean upwelling (73° W–34° S). Over the 8000 km covered by the cruise, several different trophic situations were encountered, in particular strong oligotrophic conditions in the South Pacific Gyre (SPG, between 123° W and 101° W). In this isolated region, nitrate was undetectable between the surface and 160–180 m and only trace quantities (<20 nmoles l−1) of regenerated nitrogen (nitrite and ammonium) were detected, even in the subsurface maximum. Integrated nitrate over the photic layer, which reached 165 m, was close to zero. Despite this severe nitrogen-depletion, phosphate was always present in significant concentrations (≈0.1 μmoles l−1), while silicic acid was maintained at low but classical oceanic levels (≈1 μmoles l−1). In contrast, the Marquesas region (MAR) to the west and Chilean upwelling (UPW) to the east were characterized by high nutrient concentrations, one hundred to one thousand fold higher than in the SPG. The distribution of surface chlorophyll reflected the nitrate gradient, the lowest concentrations (0.023 nmoles l−1) being measured at the centre of the SPG, where integrated value throughout the photic layer was very low (≈ 10 mg m−2). However, due to the relatively high concentrations of chlorophyll-a encountered in the DCM (0.2 μg l−1), chlorophyll-a concentrations throughout the photic layer were less variable than nitrate concentrations (by a factor 2 to 5). In contrast to chlorophyll-a, integrated particulate organic matter (POM) remained more or less constant along the study area (500 mmoles m−2, 60 mmoles m−2 and 3.5 mmoles m−2 for particulate organic carbon, particulate organic nitrogen and particulate organic phosphorus, respectively), with the exception of the upwelling, where values were two fold higher. The residence time of particulate carbon in the surface water was only 4–5 days in the upwelling, but up to 30 days in the SPG, where light isotopic δ15N signal noted in the suspended POM suggests that N2-fixation provides a dominant supply of nitrogen to phytoplankton. The most striking feature was the large accumulation of dissolved organic matter (DOM) in the SPG compared to the surrounding waters, in particular dissolved organic carbon (DOC) where concentrations were at levels rarely measured in oceanic waters (>100 μmoles l−1). Due to this large pool of DOM in the SPG photic layer, integrated values followed a converse geographical pattern to that of inorganic nutrients with a large accumulation in the centre of the SPG. Whereas suspended particulate matter in the mixed layer had a C/N ratio largely conforming to the Redfield stochiometry (C/N≈6.6), marked deviations were observed in this excess DOM (C/N≈16 to 23). The marked geographical trend suggests that a net in situ source exists, mainly due to biological processes. Thus, in spite of strong nitrate-depletion leading to low chlorophyll biomass, the closed ecosystem of the SPG can accumulate large amounts of C-rich dissolved organic matter. The implications of this finding are examined, the conclusion being that, due to weak lateral advection, the biologically produced dissolved organic carbon can be accumulated and stored in the photic layer for very long periods. In spite of the lack of seasonal vertical mixing, a significant part of new production (up to 34%), which was mainly supported by dinitrogen fixation, can be exported to deep waters by turbulent diffusion in terms of DOC. The diffusive rate estimated in the SPG (134 μmolesC m−2 d−1), was quite equivalent to the particles flux measured by sediments traps.

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Redefining the Subsurface Biosphere: Characterization of Fungi Isolated From Energy-Limited Marine Deep Subsurface Sediment

Frontiers in Fungal Biology ◽

10.3389/ffunb.2021.727543 ◽

2021 ◽

Vol 2 ◽

Author(s):

Brandi Kiel Reese ◽

Morgan S. Sobol ◽

Marshall Wayne Bowles ◽

Kai-Uwe Hinrichs

Keyword(s):

Organic Carbon ◽

Growth Parameters ◽

Carbon Sources ◽

South Pacific ◽

Physical Growth ◽

Energy Budgets ◽

Deep Subsurface ◽

Fungal Populations ◽

South Pacific Gyre

The characterization of metabolically active fungal isolates within the deep marine subsurface will alter current ecosystem models and living biomass estimates that are limited to bacterial and archaeal populations. Although marine fungi have been studied for over fifty years, a detailed description of fungal populations within the deep subsurface is lacking. Fungi possess metabolic pathways capable of utilizing previously considered non-bioavailable energy reserves. Therefore, metabolically active fungi would occupy a unique niche within subsurface ecosystems, with the potential to provide an organic carbon source for heterotrophic prokaryotic populations from the transformation of non-bioavailable energy into substrates, as well as from the fungal necromass itself. These organic carbon sources are not currently being considered in subsurface energy budgets. Sediments from South Pacific Gyre subsurface, one of the most energy-limited environments on Earth, were collected during the Integrated Ocean Drilling Program Expedition 329. Anoxic and oxic sediment slurry enrichments using fresh sediment were used to isolate multiple fungal strains in media types that varied in organic carbon substrates and concentration. Metabolically active and dormant fungal populations were also determined from nucleic acids extracted from in situ cryopreserved South Pacific Gyre sediments. For further characterization of physical growth parameters, two isolates were chosen based on their representation of the whole South Pacific Gyre fungal community. Results from this study show that fungi have adapted to be metabolically active and key community members in South Pacific Gyre sediments and potentially within global biogeochemical cycles.

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A description of late and transformation stages of larvae of the Diaphus ostenfeldi in the western periphery of the South Pacific Gyre

Fishery Bulletin ◽

10.7755/fb.118.4.1 ◽

2020 ◽

Vol 118 (4) ◽

pp. 319-323

Author(s):

Sergei A. Evseenko ◽

Yana Yu. Bolshakova

Keyword(s):

South Pacific ◽

The South ◽

South Pacific Gyre

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The role of air-sea coupling on the simulation of intraseasonal rainfall variability over the South Pacific in ECHAM5-SIT

10.5194/egusphere-egu21-12770 ◽

2021 ◽

Author(s):

Sunil Kumar Pariyar ◽

Noel Keenlyside ◽

Wan-Ling Tseng

Keyword(s):

General Circulation ◽

Rainfall Variability ◽

Intraseasonal Variability ◽

Phase Relationship ◽

Coupled Model ◽

South Pacific ◽

South Pacific Convergence Zone ◽

The South ◽

The Impact

We investigate the impact of air-sea coupling on the simulation of the intraseasonal variability of rainfall over the South Pacific using the ECHAM5 atmospheric general circulation model coupled with Snow-Ice-Thermocline (SIT) ocean model. We compare the fully coupled simulation with two uncoupled simulations forced with sea surface temperature (SST) climatology and daily SST from the coupled model. The intraseasonal rainfall variability over the South Pacific Convergence Zone (SPCZ) is reduced by 17% in the uncoupled model forced with SST climatology and increased by 8% in the uncoupled simulation forced with daily SST. The coupled model best simulates the key characteristics of the two intraseasonal rainfall modes of variability in the South Pacific, as identified by an Empirical Orthogonal Function (EOF) analysis. The spatial structure of the two EOF modes in all three simulations is very similar, suggesting these modes are independent of air-sea coupling and primarily generated by the dynamics of the atmosphere. The southeastward propagation of rainfall anomalies associated with two leading rainfall modes in the South Pacific depends upon the eastward propagating Madden-Julian Oscillation (MJO) signals over the Indian Ocean and western Pacific. Air-sea interaction seems crucial for such propagation as both eastward and southeastward propagations substantially reduced in the uncoupled model forced with SST climatology. Prescribing daily SST from the coupled model improves the simulation of both eastward and southeastward propagations in the uncoupled model forced with daily SST, showing the role of SST variability on the propagation of the intraseasonal variability, but the periodicity differs from the coupled model. The change in the periodicity is attributed to a weaker SST-rainfall relationship that shifts from SST leading rainfall to a nearly in-phase relationship in the uncoupled model forced with daily SST.

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Volume distribution for particles between 3.5 to 2000 μm in the upper 200 m region of the South Pacific Gyre

Biogeosciences ◽

10.5194/bg-5-299-2008 ◽

2008 ◽

Vol 5 (2) ◽

pp. 299-310 ◽

Cited By ~ 28

Author(s):

L. Stemmann ◽

D. Eloire ◽

A. Sciandra ◽

G. A. Jackson ◽

L. Guidi ◽

...

Keyword(s):

Weight Ratio ◽

South Pacific ◽

Dry Weight ◽

Volume Distribution ◽

The South ◽

Size Spectra ◽

Marquesas Islands ◽

Large Particles ◽

Living Organisms ◽

South Pacific Gyre

Abstract. The French JGOFS BIOSOPE cruise crossed the South Pacific Gyre (SPG) on a transect between the Marquesas Islands and the Chilean coast on a 7500 km transect (8° S–34° S and 8° W–72° W). The number and volume distributions of small (3.5100 μm) were analysed combining two instruments, the HIAC/Royco Counter (for the small particles) and the Underwater Video Profiler (UVP, for the large particles). For the HIAC analysis, samples were collected from 12 L CTD Rosette bottles and immediately analysed on board while the UVP provided an estimate of in situ particle concentrations and size in a continuous profile. Out of 76 continuous UVP and 117 discrete HIAC vertical profiles, 25 had both sets of measurements, mostly at a site close to the Marquesas Islands (site MAR) and one in the center of the gyre (site GYR). At GYR, the particle number spectra from few μm to few mm were fit with power relationships having slopes close to −4. At MAR, the high abundance of large objects, probably living organisms, created a shift in the full size spectra of particles such that a single slope was not appropriate. The small particle pool at both sites showed a diel pattern while the large did not, implying that the movement of mass toward the large particles does not take place at daily scale in the SPG area. Despite the relatively simple nature of the number spectra, the volume spectra were more variable because what were small deviations from the straight line in a log-log plot were large variations in the volume estimates. In addition, the mass estimates from the size spectra are very sensitive to crucial parameters such as the fractal dimension and the POC/Dry Weight ratio. Using consistent values for these parameters, we show that the volume of large particles can equal the volume of the smaller particles. However the proportion of material in large particles decreased from the mesotrophic conditions at the border of the SPG to the ultra-oligotrophy of the center in the upper 200 m depth. We expect large particles to play a major role in the trophic interaction in the upper waters of the South Pacific Gyre.

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