Moussab/ORKG-training-evaluation-set huggingface dataset:
Research field: Oceanography
Title: Ocean carbon cycling in the Indian Ocean: 1. Spatiotemporal variability of inorganic carbon and air-sea CO2gas exchange: INDIAN OCEAN CARBON CYCLE, 1
Abstract: The spatiotemporal variability of upper ocean inorganic carbon parameters and air‐sea CO2 exchange in the Indian Ocean was examined using inorganic carbon data collected as part of the World Ocean Circulation Experiment (WOCE) cruises in 1995. Multiple linear regression methods were used to interpolate and extrapolate the temporally and geographically limited inorganic carbon data set to the entire Indian Ocean basin using other climatological hydrographic and biogeochemical data. The spatiotemporal distributions of total carbon dioxide (TCO2), alkalinity, and seawater pCO2 were evaluated for the Indian Ocean and regions of interest including the Arabian Sea, Bay of Bengal, and 10°N–35°S zones. The Indian Ocean was a net source of CO2 to the atmosphere, and a net sea‐to‐air CO2 flux of +237 ± 132 Tg C yr−1 (+0.24 Pg C yr−1) was estimated. Regionally, the Arabian Sea, Bay of Bengal, and 10°N–10°S zones were perennial sources of CO2 to the atmosphere. In the 10°S–35°S zone, the CO2 sink or source status of the surface ocean shifts seasonally, although the region is a net oceanic sink of atmospheric CO2.
Extracted statement — Region of data collection: Indian Ocean
Research field: Oceanography
Title: Relative influence of nitrogen and phosphorous availability on phytoplankton physiology and productivity in the oligotrophic sub-tropical North Atlantic Ocean
Abstract: Nutrient addition bioassay experiments were performed in the low‐nutrient, low‐chlorophyll oligotrophic subtropical North Atlantic Ocean to investigate the influence of nitrogen (N), phosphorus (P), and/or iron (Fe) on phytoplankton physiology and the limitation of primary productivity or picophytoplankton biomass. Additions of N alone resulted in 1.5‐2 fold increases in primary productivity and chlorophyll after 48 h, with larger (~threefold) increases observed for the addition of P in combination with N (NP). Measurements of cellular chlorophyll contents permitted evaluation of the physiological response of the photosynthetic apparatus to N and P additions in three picophytoplankton groups. In both Prochlorococcus and the picoeukaryotes, cellular chlorophyll increased by similar amounts in N and NP treatments relative to all other treatments, suggesting that pigment synthesis was N limited. In contrast, the increase of cellular chlorophyll was greater in NP than in N treatments in Synechococcus, suggestive of NP co‐limitation. Relative increases in cellular nucleic acid were also only observed in Synechococcus for NP treatments, indicating co‐limitation of net nucleic acid synthesis. A lack of response to relief of nutrient stress for the efficiency of photosystem II photochemistry, Fv :Fm, suggests that the low nutrient supply to this region resulted in a condition of balanced nutrient limited growth, rather than starvation. N thus appears to be the proximal (i.e. direct physiological) limiting nutrient in the oligotrophic sub‐tropical North Atlantic. In addition, some major picophytoplankton groups, as well as overall autotrophic community biomass, appears to be co‐limited by N and P.
Extracted statement — Region of data collection: North Atlantic Ocean
Research field: Oceanography
Title: Environmental controls on the seasonal carbon dioxide fluxes in the northeastern Indian Ocean
Abstract: Total carbon dioxide (TCO 2) and computations of partial pressure of carbon dioxide (pCO 2) had been examined in Northerneastern region of Indian Ocean. It exhibit seasonal and spatial variability. North-south gradients in the pCO 2 levels were closely related to gradients in salinity caused by fresh water discharge received from rivers. Eddies observed in this region helped to elevate the nutrients availability and the biological controls by increasing the productivity. These phenomena elevated the carbon dioxide draw down during the fair seasons. Seasonal fluxes estimated from local wind speed and air-sea carbon dioxide difference indicate that during southwest monsoon, the northeastern Indian Ocean acts as a strong sink of carbon dioxide (-20.04 mmol m –2 d -1 ). Also during fall intermonsoon the area acts as a weak sink of carbon dioxide (-4.69 mmol m –2 d -1 ). During winter monsoon, this region behaves as a weak carbon dioxide source with an average sea to air flux of 4.77 mmol m -2 d -1 . In the northern region, salinity levels in the surface level are high during winter compared to the other two seasons. Northeastern Indian Ocean shows significant intraseasonal variability in carbon dioxide fluxes that are mediated by eddies which provide carbon dioxide and nutrients from the subsurface waters to the mixed layer.
Extracted statement — Region of data collection: Northeastern Indian Ocean
Research field: Oceanography
Title: Sea–air CO&lt;sub&gt;2&lt;/sub&gt; fluxes in the Indian Ocean between 1990 and 2009
Abstract: <jats:p>Abstract. The Indian Ocean (44° S–30° N) plays an important role in the global carbon cycle, yet it remains one of the most poorly sampled ocean regions. Several approaches have been used to estimate net sea–air CO2 fluxes in this region: interpolated observations, ocean biogeochemical models, atmospheric and ocean inversions. As part of the RECCAP (REgional Carbon Cycle Assessment and Processes) project, we combine these different approaches to quantify and assess the magnitude and variability in Indian Ocean sea–air CO2 fluxes between 1990 and 2009. Using all of the models and inversions, the median annual mean sea–air CO2 uptake of −0.37 ± 0.06 PgC yr−1 is consistent with the −0.24 ± 0.12 PgC yr−1 calculated from observations. The fluxes from the southern Indian Ocean (18–44° S; −0.43 ± 0.07 PgC yr−1 are similar in magnitude to the annual uptake for the entire Indian Ocean. All models capture the observed pattern of fluxes in the Indian Ocean with the following exceptions: underestimation of upwelling fluxes in the northwestern region (off Oman and Somalia), overestimation in the northeastern region (Bay of Bengal) and underestimation of the CO2 sink in the subtropical convergence zone. These differences were mainly driven by lack of atmospheric CO2 data in atmospheric inversions, and poor simulation of monsoonal currents and freshwater discharge in ocean biogeochemical models. Overall, the models and inversions do capture the phase of the observed seasonality for the entire Indian Ocean but overestimate the magnitude. The predicted sea–air CO2 fluxes by ocean biogeochemical models (OBGMs) respond to seasonal variability with strong phase lags with reference to climatological CO2 flux, whereas the atmospheric inversions predicted an order of magnitude higher seasonal flux than OBGMs. The simulated interannual variability by the OBGMs is weaker than that found by atmospheric inversions. Prediction of such weak interannual variability in CO2 fluxes by atmospheric inversions was mainly caused by a lack of atmospheric data in the Indian Ocean. The OBGM models suggest a small strengthening of the sink over the period 1990–2009 of −0.01 PgC decade−1. This is inconsistent with the observations in the southwestern Indian Ocean that shows the growth rate of oceanic pCO2 was faster than the observed atmospheric CO2 growth, a finding attributed to the trend of the Southern Annular Mode (SAM) during the 1990s.
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Extracted statement — Method: Ocean biogeochemical models
Research field: Oceanography
Title: Sea–air CO&lt;sub&gt;2&lt;/sub&gt; fluxes in the Indian Ocean between 1990 and 2009
Abstract: <jats:p>Abstract. The Indian Ocean (44° S–30° N) plays an important role in the global carbon cycle, yet it remains one of the most poorly sampled ocean regions. Several approaches have been used to estimate net sea–air CO2 fluxes in this region: interpolated observations, ocean biogeochemical models, atmospheric and ocean inversions. As part of the RECCAP (REgional Carbon Cycle Assessment and Processes) project, we combine these different approaches to quantify and assess the magnitude and variability in Indian Ocean sea–air CO2 fluxes between 1990 and 2009. Using all of the models and inversions, the median annual mean sea–air CO2 uptake of −0.37 ± 0.06 PgC yr−1 is consistent with the −0.24 ± 0.12 PgC yr−1 calculated from observations. The fluxes from the southern Indian Ocean (18–44° S; −0.43 ± 0.07 PgC yr−1 are similar in magnitude to the annual uptake for the entire Indian Ocean. All models capture the observed pattern of fluxes in the Indian Ocean with the following exceptions: underestimation of upwelling fluxes in the northwestern region (off Oman and Somalia), overestimation in the northeastern region (Bay of Bengal) and underestimation of the CO2 sink in the subtropical convergence zone. These differences were mainly driven by lack of atmospheric CO2 data in atmospheric inversions, and poor simulation of monsoonal currents and freshwater discharge in ocean biogeochemical models. Overall, the models and inversions do capture the phase of the observed seasonality for the entire Indian Ocean but overestimate the magnitude. The predicted sea–air CO2 fluxes by ocean biogeochemical models (OBGMs) respond to seasonal variability with strong phase lags with reference to climatological CO2 flux, whereas the atmospheric inversions predicted an order of magnitude higher seasonal flux than OBGMs. The simulated interannual variability by the OBGMs is weaker than that found by atmospheric inversions. Prediction of such weak interannual variability in CO2 fluxes by atmospheric inversions was mainly caused by a lack of atmospheric data in the Indian Ocean. The OBGM models suggest a small strengthening of the sink over the period 1990–2009 of −0.01 PgC decade−1. This is inconsistent with the observations in the southwestern Indian Ocean that shows the growth rate of oceanic pCO2 was faster than the observed atmospheric CO2 growth, a finding attributed to the trend of the Southern Annular Mode (SAM) during the 1990s.
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Extracted statement — Method: Ocean inversions
Research field: Oceanography
Title: Evidence for efficient regenerated production and dinitrogen fixation in nitrogen-deficient waters of the South Pacific Ocean: impact on new and export production estimates
Abstract: Abstract. One of the major objectives of the BIOSOPE cruise, carried out on the R/V Atalante from October-November 2004 in the South Pacific Ocean, was to establish productivity rates along a zonal section traversing the oligotrophic South Pacific Gyre (SPG). These results were then compared to measurements obtained from the nutrient – replete waters in the Chilean upwelling and around the Marquesas Islands. A dual 13C/15N isotope technique was used to estimate the carbon fixation rates, inorganic nitrogen uptake (including dinitrogen fixation), ammonium (NH4) and nitrate (NO3) regeneration and release of dissolved organic nitrogen (DON). The SPG exhibited the lowest primary production rates (0.15 g C m−2 d−1), while rates were 7 to 20 times higher around the Marquesas Islands and in the Chilean upwelling, respectively. In the very low productive area of the SPG, most of the primary production was sustained by active regeneration processes that fuelled up to 95% of the biological nitrogen demand. Nitrification was active in the surface layer and often balanced the biological demand for nitrate, especially in the SPG. The percentage of nitrogen released as DON represented a large proportion of the inorganic nitrogen uptake (13–15% in average), reaching 26–41% in the SPG, where DON production played a major role in nitrogen cycling. Dinitrogen fixation was detectable over the whole study area; even in the Chilean upwelling, where rates as high as 3 nmoles l−1 d−1 were measured. In these nutrient-replete waters new production was very high (0.69±0.49 g C m−2 d−1) and essentially sustained by nitrate levels. In the SPG, dinitrogen fixation, although occurring at much lower daily rates (≈1–2 nmoles l−1 d−1), sustained up to 100% of the new production (0.008±0.007 g C m−2 d−1) which was two orders of magnitude lower than that measured in the upwelling. The annual N2-fixation of the South Pacific is estimated to 21×1012g, of which 1.34×1012g is for the SPG only. Even if our "snapshot" estimates of N2-fixation rates were lower than that expected from a recent ocean circulation model, these data confirm that the N-deficiency South Pacific Ocean would provide an ideal ecological niche for the proliferation of N2-fixers which are not yet identified.
Extracted statement — Region of data collection: South Pacific Ocean
Research field: Oceanography
Title: Niche partitioning by photosynthetic plankton as a driver of CO2-fixation across the oligotrophic South Pacific Subtropical Ocean
Abstract: Abstract Oligotrophic ocean gyre ecosystems may be expanding due to rising global temperatures [1–5]. Models predicting carbon flow through these changing ecosystems require accurate descriptions of phytoplankton communities and their metabolic activities [6]. We therefore measured distributions and activities of cyanobacteria and small photosynthetic eukaryotes throughout the euphotic zone on a zonal transect through the South Pacific Ocean, focusing on the ultraoligotrophic waters of the South Pacific Gyre (SPG). Bulk rates of CO 2 fixation were low (0.1 µmol C l −1 d −1 ) but pervasive throughout both the surface mixed-layer (upper 150 m), as well as the deep chlorophyll a maximum of the core SPG. Chloroplast 16S rRNA metabarcoding, and single-cell 13 CO 2 uptake experiments demonstrated niche differentiation among the small eukaryotes and picocyanobacteria. Prochlorococcus abundances, activity, and growth were more closely associated with the rims of the gyre. Small, fast-growing, photosynthetic eukaryotes, likely related to the Pelagophyceae, characterized the deep chlorophyll a maximum. In contrast, a slower growing population of photosynthetic eukaryotes, likely comprised of Dictyochophyceae and Chrysophyceae, dominated the mixed layer that contributed 65–88% of the areal CO 2 fixation within the core SPG. Small photosynthetic eukaryotes may thus play an underappreciated role in CO 2 fixation in the surface mixed-layer waters of ultraoligotrophic ecosystems.
Extracted statement — Region of data collection: South Pacific Ocean
Research field: Oceanography
Title: N2 Fixation and New Insights Into Nitrification From the Ice-Edge to the Equator in the South Pacific Ocean
Abstract: Nitrogen (N) is an essential element for life and controls the magnitude of primary productivity in the ocean. In order to describe the microorganisms that catalyze N transformations in surface waters in the South Pacific Ocean, we collected high-resolution biotic and abiotic data along a 7000 km transect, from the Antarctic ice edge to the equator. The transect, conducted between late Austral autumn and early winter 2016, covered major oceanographic features such as the polar front (PF), the subtropical front (STF) and the Pacific equatorial divergence (PED). We measured N2 fixation and nitrification rates and quantified the relative abundances of diazotrophs and nitrifiers in a region where few to no rate measurements are available. Even though N2 fixation rates are usually below detection limits in cold environments, we were able to measure this N pathway at 7/10 stations in the cold and nutrient rich waters near the PF. This result highlights that N2 fixation rates continue to be measured outside the well-known subtropical regions. The majority of the mid to high N2 fixation rates (>∼20 nmol L–1 d–1), however, still occurred in the expected tropical and subtropical regions. High throughput sequence analyses of the dinitrogenase reductase gene (nifH) revealed that the nifH Cluster I dominated the diazotroph diversity throughout the transect. nifH gene richness did not show a latitudinal trend, nor was it significantly correlated with N2 fixation rates. Nitrification rates above the mixed layer in the Southern Ocean ranged between 56 and 1440 nmol L–1 d–1. Our data showed a decoupling between carbon and N assimilation (NO3– and NH4+ assimilation rates) in winter in the South Pacific Ocean. Phytoplankton community structure showed clear changes across the PF, the STF and the PED, defining clear biomes. Overall, these findings provide a better understanding of the ecosystem functionality in the South Pacific Ocean across key oceanographic biomes.
Extracted statement — Region of data collection: South Pacific Ocean
Research field: Oceanography
Title: Linkage Between Dinitrogen Fixation and Primary Production in the Oligotrophic South Pacific Ocean
Abstract: The import of nitrogen via dinitrogen fixation supports primary production, particularly in the oligotrophic ocean; however, to what extent dinitrogen fixation influences primary production, and the role of specific types of diazotrophs, remains poorly understood. We examined the relationship between primary production and dinitrogen fixation together with diazotroph community structure in the oligotrophic western and eastern South Pacific Ocean and found that dinitrogen fixation was higher than nitrate‐based new production. Primary production increased in the middle of the western subtropical region, where the cyanobacterium Trichodesmium dominated the diazotroph community and accounted for up to 7.8% of the phytoplankton community, and the abundance of other phytoplankton taxa (especially Prochlorococcus) was high. These results suggest that regenerated production was enhanced by nitrogen released from Trichodesmium and that carbon fixation by Trichodesmium also contributed significantly to total primary production. Although volumetric dinitrogen fixation was comparable between the western and eastern subtropical regions, primary production in the western waters was more than twice as high as that in the eastern waters, where UCYN‐A1 (photoheterotroph) and heterotrophic bacteria were the dominant diazotrophs. This suggests that dinitrogen fixed by these diazotrophs contributed relatively little to primary production of the wider community, and there was limited carbon fixation by these diazotrophs. Hence, we document how the community composition of diazotrophs in the field can be reflected in how much nitrogen becomes available to the wider phytoplankton community and in how much autotrophic diazotrophs themselves fix carbon and thereby influences the magnitude of local primary production.
Extracted statement — Region of data collection: South Pacific Ocean
Research field: Oceanography
Title: Measurements of nitrogen fixation in the oligotrophic North Pacific Subtropical Gyre using a free-drifting submersible incubation device
Abstract: One challenge in field-based marine microbial ecology is to achieve sufficient spatial resolution to obtain representative information about microbial distributions and biogeochemical processes. The challenges are exacerbated when conducting rate measurements of biological processes due to potential perturbations during sampling and incubation. Here we present the first application of a robotic microlaboratory, the 4 L-submersible incubation device (SID), for conducting in situ measurements of the rates of biological nitrogen (N2) fixation (BNF). The free-drifting autonomous instrument obtains samples from the water column that are incubated in situ after the addition of 15N2 tracer. After each of up to four consecutive incubation experiments, the 4-L sample is filtered and chemically preserved. Measured BNF rates from two deployments of the SID in the oligotrophic North Pacific ranged from 0.8 to 2.8 nmol N L?1 day?1, values comparable with simultaneous rate measurements obtained using traditional conductivity–temperature–depth (CTD)–rosette sampling followed by on-deck or in situ incubation. Future deployments of the SID will help to better resolve spatial variability of oceanic BNF, particularly in areas where recovery of seawater samples by CTD compromises their integrity, e.g. anoxic habitats.
Extracted statement — Method: Submersible incubation device
Research field: Oceanography
Title: Biogeographic drivers of diazotrophs in the western Pacific Ocean
Abstract: The global budget of marine nitrogen (N) is not balanced, with N removal largely exceeding N fixation. One of the major causes of this imbalance is our inadequate understanding of the diversity and distribution of marine N2 fixers (diazotrophs) as well as their contribution to N2 fixation. Here, we performed a large‐scale cross‐system study spanning the South China Sea, Luzon Strait, Philippine Sea, and western tropical Pacific Ocean to compare the biogeography of seven major diazotrophic groups and N2 fixation rates in these ecosystems. Distinct spatial niche differentiation was observed. Trichodesmium was dominant in the South China Sea and western equatorial Pacific, whereas the unicellular cyanobacterium UCYN‐B dominated in the Philippine Sea. Furthermore, contrasting diel patterns of Trichodesmium nifH genes and UCYN‐B nifH gene transcript activity were observed. The heterotrophic diazotroph Gamma A phylotype was widespread throughout the western Pacific Ocean and occupied an ecological niche that overlapped with that of UCYN‐B. Moreover, Gamma A (or other possible unknown/undetected diazotrophs) rather than Trichodesmium and UCYN‐B may have been responsible for the high N2 fixation rates in some samples. Regional biogeochemistry analyses revealed cross‐system variations in N2‐fixing community composition and activity constrained by sea surface temperature, aerosol optical thickness, current velocity, mixed‐layer depth, and chlorophyll a concentration. These factors except for temperature essentially control/reflected iron supply/bioavailability and thus drive diazotroph biogeography. This study highlights biogeographical controls on marine N2 fixers and increases our understanding of global diazotroph biogeography.
Extracted statement — Region of data collection: Western Pacific Ocean
Research field: Operations Research, Systems Engineering and Industrial Engineering
Title: Energy management and optimization: case study of a textile plant in Istanbul, Turkey
Abstract: Purpose This paper aims to present the results of energy management and optimization studies in one Turkish textile factory. In a case study of a print and dye factory in Istanbul, the authors identified energy-sensitive processes and proposed energy management applications. Design/methodology/approach Appropriate energy management methods have been implemented in the factory, and the results were examined in terms of energy efficiency and cost reduction. Findings By applying the methods for fuel distribution optimization, the authors demonstrated that energy costs could be decreased by approximately. Originality/value Energy management is a vital issue for industries particularly in developing countries such as Turkey. Turkey is an energy poor country and imports more than half of its energy to satisfy its increasing domestic demands. An important share of these demands stems from the presence of a strong textile industry that operates throughout the country.
Extracted statement — Type of industry: Textile industry