The relation of mixed-layer net community production to phytoplankton community composition in the Southern Ocean

Abstract. Southern Ocean organic carbon export plays an important role in the global carbon cycle, yet its basin-scale climatology and variability are uncertain due to limited coverage of in situ observations. In this study, a neural network approach based on the self-organizing map (SOM) is adopted to construct weekly gridded (1° × 1°) maps of organic carbon export for the Southern Ocean from 1998 to 2009. The SOM is trained with in situ measurements of O2 / Ar-derived net community production (NCP) that are tightly linked to the carbon export in the mixed layer on timescales of one to two weeks and with six potential NCP predictors: photosynthetically available radiation (PAR), particulate organic carbon (POC), chlorophyll (Chl), sea surface temperature (SST), sea surface height (SSH), and mixed layer depth (MLD). This nonparametric approach is based entirely on the observed statistical relationships between NCP and the predictors and, therefore, is strongly constrained by observations. A thorough cross-validation yields three retained NCP predictors, Chl, PAR, and MLD. Our constructed NCP is further validated by good agreement with previously published, independent in situ derived NCP of weekly or longer temporal resolution through real-time and climatological comparisons at various sampling sites. The resulting November–March NCP climatology reveals a pronounced zonal band of high NCP roughly following the Subtropical Front in the Atlantic, Indian, and western Pacific sectors, and turns southeastward shortly after the dateline. Other regions of elevated NCP include the upwelling zones off Chile and Namibia, the Patagonian Shelf, the Antarctic coast, and areas surrounding the Islands of Kerguelen, South Georgia, and Crozet. This basin-scale NCP climatology closely resembles that of the satellite POC field and observed air–sea CO2 flux. The long-term mean area-integrated NCP south of 50° S from our dataset, 17.9 mmol C m−2 d−1, falls within the range of 8.3 to 24 mmol C m−2 d−1 from other model estimates. A broad agreement is found in the basin-wide NCP climatology among various models but with significant spatial variations, particularly in the Patagonian Shelf. Our approach provides a comprehensive view of the Southern Ocean NCP climatology and a potential opportunity to further investigate interannual and intraseasonal variability.

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Phytoplankton community composition and photosynthetic physiology in the Australian sector of the Southern Ocean during the austral summer of 2010/2011

Polar Biology ◽

10.1007/s00300-014-1542-6 ◽

2014 ◽

Vol 37 (11) ◽

pp. 1563-1578 ◽

Cited By ~ 7

Author(s):

Shintaro Takao ◽

Toru Hirawake ◽

Gen Hashida ◽

Hiroshi Sasaki ◽

Hiroshi Hattori ◽

...

Keyword(s):

Southern Ocean ◽

Community Composition ◽

Phytoplankton Community ◽

Austral Summer ◽

Phytoplankton Community Composition ◽

Photosynthetic Physiology

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Variations of net primary productivity and phytoplankton community composition in the Indian sector of the Southern Ocean as estimated from ocean color remote sensing data

Biogeosciences ◽

10.5194/bg-9-3875-2012 ◽

2012 ◽

Vol 9 (10) ◽

pp. 3875-3890 ◽

Cited By ~ 13

Author(s):

S. Takao ◽

T. Hirawake ◽

S. W. Wright ◽

K. Suzuki

Keyword(s):

Southern Ocean ◽

Community Composition ◽

Primary Productivity ◽

Phytoplankton Community ◽

Net Primary Productivity ◽

Austral Summer ◽

Remote Sensing Data ◽

The Past ◽

Phytoplankton Community Composition ◽

Indian Sector

Abstract. Phytoplankton population dynamics play an important role in biogeochemical cycles in the Southern Ocean during austral summer. Recent environmental changes such as a rise in sea surface temperature (SST) are likely to impact on net primary productivity (NPP) and phytoplankton community composition. However, their spatiotemporal relationships are still unclear in the Southern Ocean. Here we assessed the relationships between NPP, dominant phytoplankton groups, and SST in the Indian sector of the Southern Ocean over the past decade (1997–2007) using satellite remote sensing data. As a result, we found a statistically significant reduction in NPP in the polar frontal zone over the past decade during austral summer. Moreover, the decrease in NPP positively correlated with the dominance of diatoms (Kendall's rank correlation τ = 0.60) estimated by a phytoplankton community composition model, but not correlated with SST. In the seasonal ice zone, NPP correlated with not only the dominance of diatoms positively (τ = 0.56), but also the dominance of haptophytes (τ = −0.54) and SST (τ = −0.54) negatively. Our results suggested that summer NPP values were strongly affected by the phytoplankton community composition in the Indian sector of the Southern Ocean.

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Variations of net primary productivity and phytoplankton community composition in the Southern Ocean as estimated from ocean-color remote sensing data

Biogeosciences Discussions ◽

10.5194/bgd-9-4361-2012 ◽

2012 ◽

Vol 9 (4) ◽

pp. 4361-4398 ◽

Cited By ~ 1

Author(s):

S. Takao ◽

T. Hirawake ◽

S. W. Wright ◽

K. Suzuki

Keyword(s):

Remote Sensing ◽

Southern Ocean ◽

Community Composition ◽

Primary Productivity ◽

Phytoplankton Community ◽

Net Primary Productivity ◽

Austral Summer ◽

Remote Sensing Data ◽

The Past ◽

Phytoplankton Community Composition

Abstract. Phytoplankton population dynamics play an important role in biogeochemical cycles in the Southern Ocean during austral summer. Recent environmental changes such as a rise in sea surface temperature (SST) are likely to impact on net primary productivity (NPP) and phytoplankton community composition. However, their spatiotemporal relationships are still unclear in the Southern Ocean. Here we assessed the relationships between NPP, dominant phytoplankton groups, and SST in the Indian sector of the Southern Ocean over the past decade (1997–2007) using satellite remote sensing data. As a result, we found a statistically significant reduction in NPP in the polar frontal zone over the past decade during austral summer. Moreover, the decrease in NPP positively correlated with the dominance of diatoms (Kendall's rank correlation τ = 0.60) estimated by a phytoplankton community composition model, but not correlated with SST. In the seasonal ice zone, NPP correlated with not only the dominance of diatoms positively (τ = 0.56), but also the dominance of haptophytes (τ = −0.54) and SST (τ = −0.54) negatively. Our results suggested that summer NPP values were strongly affected by the phytoplankton community composition in the Southern Ocean.

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Neural network-based estimates of Southern Ocean net community production from in-situ O<sub>2</sub> / Ar and satellite observation: a methodological study

Biogeosciences Discussions ◽

10.5194/bgd-10-16923-2013 ◽

2013 ◽

Vol 10 (10) ◽

pp. 16923-16972 ◽

Cited By ~ 1

Author(s):

C.-H. Chang ◽

N. C. Johnson ◽

N. Cassar

Keyword(s):

Neural Network ◽

Organic Carbon ◽

Southern Ocean ◽

Mixed Layer ◽

Sea Surface ◽

Carbon Export ◽

Net Community Production ◽

Basin Scale ◽

Community Production

Abstract. Southern Ocean organic carbon export plays an important role in the global carbon cycle, yet its basin-scale climatology and variability are uncertain due to limited coverage of in situ observations. In this study, a neural network approach based on the self-organizing map (SOM) is adopted to construct weekly gridded (1° × 1°) maps of organic carbon export for the Southern Ocean from 1998 to 2009. The SOM is trained with in situ measurements of O2 / Ar-derived net community production (NCP) that are tightly linked to the carbon export in the mixed layer on timescales of 1–2 weeks, and six potential NCP predictors: photosynthetically available radiation (PAR), particulate organic carbon (POC), chlorophyll (Chl), sea surface temperature (SST), sea surface height (SSH), and mixed layer depth (MLD). This non-parametric approach is based entirely on the observed statistical relationships between NCP and the predictors, and therefore is strongly constrained by observations. A thorough cross-validation yields three retained NCP predictors, Chl, PAR, and MLD. Our constructed NCP is further validated by good agreement with previously published independent in situ derived NCP of weekly or longer temporal resolution through real-time and climatological comparisons at various sampling sites. The resulting November–March NCP climatology reveals a pronounced zonal band of high NCP roughly following the subtropical front in the Atlantic, Indian and western Pacific sectors, and turns southeastward shortly after the dateline. Other regions of elevated NCP include the upwelling zones off Chile and Namibia, Patagonian Shelf, Antarctic coast, and areas surrounding the Islands of Kerguelen, South Georgia, and Crozet. This basin-scale NCP climatology closely resembles that of the satellite POC field and observed air-sea CO2 flux. The long-term mean area-integrated NCP south of 50° S from our dataset, 14 mmol C m–2 d–1, falls within the range of 8.3–24 mmol C m–2 d–1 from other model estimates. A broad agreement is found in the basin-wide NCP climatology among various models but with significant spatial variations, particularly in the Patagonian Shelf. Our approach provides a comprehensive view of the Southern Ocean NCP climatology and a potential opportunity to further investigate interannual and intraseasonal variability.

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Links Between the Phytoplankton Community Composition and Trace Metal Distribution in Summer Surface Waters of the Atlantic Southern Ocean

Frontiers in Marine Science ◽

10.3389/fmars.2019.00295 ◽

2019 ◽

Vol 6 ◽

Cited By ~ 1

Author(s):

Johannes J. Viljoen ◽

Ian Weir ◽

Susanne Fietz ◽

Ryan Cloete ◽

Jean Loock ◽

...

Keyword(s):

Southern Ocean ◽

Trace Metal ◽

Community Composition ◽

Surface Waters ◽

Phytoplankton Community ◽

Metal Distribution ◽

Phytoplankton Community Composition ◽

Trace Metal Distribution

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Effects of phytoplankton community composition and productivity on sea surface pCO2 variations in the Southern Ocean

Deep Sea Research Part I Oceanographic Research Papers ◽

10.1016/j.dsr.2020.103263 ◽

2020 ◽

Vol 160 ◽

pp. 103263

Author(s):

Shintaro Takao ◽

Shin-Ichiro Nakaoka ◽

Fuminori Hashihama ◽

Keishi Shimada ◽

Hisayuki Yoshikawa-Inoue ◽

...

Keyword(s):

Southern Ocean ◽

Community Composition ◽

Phytoplankton Community ◽

Sea Surface ◽

Phytoplankton Community Composition

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Are Bacterio- and Phytoplankton Community Compositions Related in Lakes Differing in Their Cyanobacteria Contribution and Physico-Chemical Properties?

Genes ◽

10.3390/genes12060855 ◽

2021 ◽

Vol 12 (6) ◽

pp. 855

Author(s):

Mikołaj Kokociński ◽

Dariusz Dziga ◽

Adam Antosiak ◽

Janne Soininen

Keyword(s):

Environmental Factors ◽

Community Composition ◽

Phytoplankton Community ◽

Heterotrophic Bacteria ◽

Bacterial Community Composition ◽

Physical Factors ◽

Research Attention ◽

Phytoplankton Community Composition ◽

The Impact ◽

Bacteria Communities

Bacterioplankton community composition has become the center of research attention in recent years. Bacteria associated with toxic cyanobacteria blooms have attracted considerable interest. However, little is known about the environmental factors driving the bacteria community, including the impact of invasive cyanobacteria. Therefore, our aim has been to determine the relationships between heterotrophic bacteria and phytoplankton community composition across 24 Polish lakes with different contributions of cyanobacteria including the invasive species Raphidiopsis raciborskii. This analysis revealed that cyanobacteria were present in 16 lakes, while R. raciborskii occurred in 14 lakes. Our results show that bacteria communities differed between lakes dominated by cyanobacteria and lakes with minor contributions of cyanobacteria but did not differ between lakes with R. raciborskii and other lakes. Physical factors, including water and Secchi depth, were the major drivers of bacteria and phytoplankton community composition. However, in lakes dominated by cyanobacteria, bacterial community composition was also influenced by biotic factors such as the amount of R. raciborskii, chlorophyll-a and total phytoplankton biomass. Thus, our study provides novel evidence on the influence of environmental factors and R. raciborskii on lake bacteria communities.

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