Net community production and metabolic balance at the oligotrophic ocean site, station ALOHA

Abstract. Oxygen microprobes were used to estimate Community Respiration (R), Net Community Production (NCP) and Gross Primary Production (GPP) in coastal seawater samples. Using this highly stable and reproducible technique to measure oxygen change during alternating dark and light periods, we show that respiration in the light could account for up to 640% of respiration in the dark. The light enhanced dark respiration can remain elevated for several hours following a 12 h period of illumination. Not including Rlight into calculations of production leads to an underestimation of GPP, which can reach up to 650% in net heterotrophic systems. The production: respiration (P:R) ratio is in turn affected by the higher respiration rates and by the underestimation of GPP. While the integration of Rlight into the calculation of P:R ratio does not change the metabolic balance of the system, it decreases the observed tendency, thus net autotrophic systems become less autotrophic and net heterotrophic systems become less heterotrophic. As a consequence, we propose that efforts have to be focused on the estimation and the integration of Rlight into the determination of GPP and R for a better understanding of the aquatic carbon cycle.

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Artificial Upwelling in Singular and Recurring Mode: Consequences for Net Community Production and Metabolic Balance

Frontiers in Marine Science ◽

10.3389/fmars.2021.743105 ◽

2022 ◽

Vol 8 ◽

Author(s):

Joaquin Ortiz ◽

Javier Arístegui ◽

Jan Taucher ◽

Ulf Riebesell

Keyword(s):

Deep Water ◽

Large Scale ◽

Phytoplankton Community ◽

Metabolic Balance ◽

Net Community Production ◽

Marine Fishery ◽

Local Responses ◽

Water Pulse ◽

Community Production

Artificial upwelling of nutrient-rich waters and the corresponding boost in primary productivity harbor the potential to enhance marine fishery yields and strengthen the biological pump for sequestration of atmospheric CO2. There is increasing urgency to understand this technology as a “ocean-based solution” for counteracting two major challenges of the 21st century—climate change and overfishing. Yet, little is known about the actual efficacy and/or possible side effects of artificial upwelling. We conducted a large-scale off-shore mesocosm study (∼44 m3) in the oligotrophic waters of the Canary Islands to identify the community-level effects of artificial upwelling on a natural oligotrophic plankton community. Four upwelling intensities were simulated (approx. 1.5/3/5.7/10 μmol L–1 of nitrate plus phosphate and silicate) via two different upwelling modes (a singular deep-water pulse vs. recurring supply every 4 days) for 37 days. Here we present results on the response of net community production (NCP), metabolic balance and phytoplankton community composition (<250 μm). Higher upwelling intensities yielded higher cumulative NCP. Following upwelling onset, the phytoplankton community became dominated by diatoms in all treatments, but other taxa such as Coccolithophores increased later in the experiment. The magnitude of effects on the metabolic balance scaled with the amount of added deep water, leading to (i) a balanced to net-heterotrophic system in the singular and (ii) a net-autotrophic system in the recurring upwelling treatments. Accordingly, the mode in which nutrients are supplied to an oligotrophic system plays a crucial role in the ecosystem response, with recurring upwelling leading to higher long-term positive NCP than singular upwelling. These results highlight the importance of empirically measured local responses to upwelling such as community structure and metabolism, with major implications for the potential employment of artificial upwelling as an ocean-based solution to generate (primary) production.

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Control of net community production by microbial community respiration at Station ALOHA

Journal of Marine Systems ◽

10.1016/j.jmarsys.2018.03.007 ◽

2018 ◽

Vol 184 ◽

pp. 28-35

Author(s):

Sandra Martínez-García ◽

Robert R. Bidigare ◽

Daniela A. del Valle ◽

Laurie W. Juranek ◽

David P. Nicholson ◽

...

Keyword(s):

Microbial Community ◽

Community Respiration ◽

Net Community Production ◽

Station Aloha ◽

Community Production

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Satellite estimates of net community production based on O2/Ar observations and comparison to other estimates

Global Biogeochemical Cycles ◽

10.1002/2015gb005314 ◽

2016 ◽

Vol 30 (5) ◽

pp. 735-752 ◽

Cited By ~ 19

Author(s):

Zuchuan Li ◽

Nicolas Cassar

Keyword(s):

Net Community Production ◽

Community Production

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Linking Southern Ocean mixed‐layer dynamics to net community production on various timescales

Journal of Geophysical Research Oceans ◽

10.1029/2021jc017537 ◽

2021 ◽

Author(s):

Zuchuan Li ◽

M. Susan Lozier ◽

Nicolas Cassar

Keyword(s):

Southern Ocean ◽

Mixed Layer ◽

Ocean Mixed Layer ◽

Net Community Production ◽

Community Production

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Benthic buffers and boosters of ocean acidification on coral reefs

Biogeosciences ◽

10.5194/bg-10-4897-2013 ◽

2013 ◽

Vol 10 (7) ◽

pp. 4897-4909 ◽

Cited By ~ 45

Author(s):

K. R. N. Anthony ◽

G. Diaz-Pulido ◽

N. Verlinden ◽

B. Tilbrook ◽

A. J. Andersson

Keyword(s):

Ocean Acidification ◽

Benthic Communities ◽

Time Of Day ◽

High Flow ◽

Net Community Production ◽

Reef Environment ◽

Saturation State ◽

Low Co2 ◽

Coral Reef Environment ◽

Community Production

Abstract. Ocean acidification is a threat to marine ecosystems globally. In shallow-water systems, however, ocean acidification can be masked by benthic carbon fluxes, depending on community composition, seawater residence time, and the magnitude and balance of net community production (NCP) and calcification (NCC). Here, we examine how six benthic groups from a coral reef environment on Heron Reef (Great Barrier Reef, Australia) contribute to changes in the seawater aragonite saturation state (Ωa). Results of flume studies using intact reef habitats (1.2 m by 0.4 m), showed a hierarchy of responses across groups, depending on CO2 level, time of day and water flow. At low CO2 (350–450 μatm), macroalgae (Chnoospora implexa), turfs and sand elevated Ωa of the flume water by around 0.10 to 1.20 h−1 – normalised to contributions from 1 m2 of benthos to a 1 m deep water column. The rate of Ωa increase in these groups was doubled under acidification (560–700 μatm) and high flow (35 compared to 8 cm s−1). In contrast, branching corals (Acropora aspera) increased Ωa by 0.25 h−1 at ambient CO2 (350–450 μatm) during the day, but reduced Ωa under acidification and high flow. Nighttime changes in Ωa by corals were highly negative (0.6–0.8 h−1) and exacerbated by acidification. Calcifying macroalgae (Halimeda spp.) raised Ωa by day (by around 0.13 h−1), but lowered Ωa by a similar or higher amount at night. Analyses of carbon flux contributions from benthic communities with four different compositions to the reef water carbon chemistry across Heron Reef flat and lagoon indicated that the net lowering of Ωa by coral-dominated areas can to some extent be countered by long water-residence times in neighbouring areas dominated by turfs, macroalgae and carbonate sand.

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Seasonal patterns in Arctic planktonic metabolism (Fram Strait – Svalbard region)

Biogeosciences ◽

10.5194/bg-10-1451-2013 ◽

2013 ◽

Vol 10 (3) ◽

pp. 1451-1469 ◽

Cited By ~ 24

Author(s):

R. Vaquer-Sunyer ◽

C. M. Duarte ◽

J. Holding ◽

A. Regaudie-de-Gioux ◽

L. S. García-Corral ◽

...

Keyword(s):

Arctic Ocean ◽

Early Spring ◽

The Arctic ◽

Fram Strait ◽

Metabolic Rates ◽

Net Community Production ◽

Western Sector ◽

The Arctic Ocean ◽

European Arctic ◽

Community Production

Abstract. The metabolism of the Arctic Ocean is marked by extremely pronounced seasonality and spatial heterogeneity associated with light conditions, ice cover, water masses and nutrient availability. Here we report the marine planktonic metabolic rates (net community production, gross primary production and community respiration) along three different seasons of the year, for a total of eight cruises along the western sector of the European Arctic (Fram Strait – Svalbard region) in the Arctic Ocean margin: one at the end of 2006 (fall/winter), two in 2007 (early spring and summer), two in 2008 (early spring and summer), one in 2009 (late spring–early summer), one in 2010 (spring) and one in 2011 (spring). The results show that the metabolism of the western sector of the European Arctic varies throughout the year, depending mostly on the stage of bloom and water temperature. Here we report metabolic rates for the different periods, including the spring bloom, summer and the dark period, increasing considerably the empirical basis of metabolic rates in the Arctic Ocean, and especially in the European Arctic corridor. Additionally, a rough annual metabolic estimate for this area of the Arctic Ocean was calculated, resulting in a net community production of 108 g C m−2 yr−1.

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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 ◽

10.5194/bg-11-3279-2014 ◽

2014 ◽

Vol 11 (12) ◽

pp. 3279-3297 ◽

Cited By ~ 7

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 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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