scholarly journals Reconstructing past variations in environmental conditions and paleoproductivity over the last  ∼ 8000 years off north-central Chile (30° S)

2020 ◽  
Vol 17 (22) ◽  
pp. 5763-5785
Author(s):  
Práxedes Muñoz ◽  
Lorena Rebolledo ◽  
Laurent Dezileau ◽  
Antonio Maldonado ◽  
Christoph Mayr ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Productivity ◽  
Environmental Conditions ◽  
Time Interval ◽  
Coastal Zones ◽  
Moisture Index ◽  
Subtropical Anticyclone ◽  
North Central ◽  
The North ◽  
Lower Productivity

Abstract. The aim of this project was to establish past variations in the main oceanographic and climatic features of a transitional semiarid ecosystem on the north-central Chilean coast. We analyzed recent sedimentary records retrieved from two bays, Guanaqueros and Tongoy (30∘ S), for geochemical and biological analyses, including the following: sensitive redox trace elements, biogenic opal, total organic carbon (TOC), diatoms and stable isotopes of organic carbon and nitrogen. Three remarkable periods were established with different environmental conditions and productivities: (1) > 6600 cal BP, (2) 4500–1800 cal BP and (3) 140 cal BP to the present (2015 CE). The first period was characterized by a remarkably higher productivity (higher diatom abundances and opal) in which large fluxes of organic compounds were also inferred from the accumulation of elements, such as Ba, Ca, Ni, Cd and P, in the sediments. Meanwhile, significantly reduced conditions at the bottom of the bays were suggested based on the large accumulation of Mo, Re and U, showing a peak at 6600 cal BP, when sulfidic conditions could have been present. According to the pollen moisture index (PMI), this was also identified as the driest interval. These conditions should be associated with an intensification of the Southern Pacific Subtropical Anticyclone (SPSA) and stronger southerly western winds, emulating La Niña-like conditions, as has been described for the SE Pacific during the early Holocene and part of the mid-Holocene. During most of the second period, lower productivity was observed; however, a small increase was identified between 3400 and 4000 cal BP, although lower amounts of diatom (valves g−1) and nutrient-type metal accumulations were evident. Anoxic conditions at the bottom of the bays changed to an almost stable suboxic condition during this time interval. The third period was marked by intense oxygenation after 1800 cal BP, as observed by a drastic change in the accumulation of U, Mo and Re. This was followed by a return to more reduced conditions over the past 2 centuries, characterized by a small productivity rise after ∼140 cal BP, as suggested by the opal accumulations. Overall, lower primary productivity, lower reduced conditions at the bottom and higher-humidity conditions were established after 6600 cal BP to the present. We suggest that the oxygenation might be associated with a weak effect from the oxygen minimum zone over the shelf and intensified El Niño activity, introducing oxygenated waters to the coastal zones through the propagation of equatorial waves and establishment of conditions that reduced the primary productivity from the mid-Holocene toward the beginning of the modern era.

Effect of straw amendment modes on soil organic carbon, nitrogen sequestration and crop yield on the North‐Central Plain of China

2019 ◽  
Vol 35 (3) ◽  
pp. 511-525 ◽  
Author(s):  
Huili Zhao ◽  
Peng Ning ◽  
Yanlong Chen ◽  
Jifei Liu ◽  
Shar A. Ghaffar ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Crop Yield ◽  
North Central ◽  
Central Plain ◽  
The North ◽  
Nitrogen Sequestration ◽  
Straw Amendment

Impacts of Oyster Reef Restoration on Primary Productivity and Nutrient Dynamics in Tidal Creeks of the North Central Gulf of Mexico

2010 ◽  
Vol 33 (6) ◽  
pp. 1355-1364 ◽  
Author(s):  
Rochelle Plutchak ◽  
Kelly Major ◽  
Just Cebrian ◽  
C. Drew Foster ◽  
Mary-Elizabeth C. Miller ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Primary Productivity ◽  
Nutrient Dynamics ◽  
Oyster Reef ◽  
Tidal Creeks ◽  
North Central ◽  
Reef Restoration ◽  
The North

scholarly journals Reconstructing past variations in environmental conditions and paleoproductivity over the last ~ 8000 years off Central Chile (30° S)

2018 ◽  
Author(s):  
Práxedes Muñoz ◽  
Lorena Rebolledo ◽  
Laurent Dezileau ◽  
Antonio Maldonado ◽  
Christoph Mayr ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Productivity ◽  
El Niño ◽  
Arid Zone ◽  
El Nino ◽  
Southern Oscillation ◽  
Coastal Zones ◽  
Winter Climate ◽  
Continuous Increase ◽  
Semi Arid

Abstract. This study aims at establishing past variations of the main oceanographic and climatic features in the Central Chilean coast, using recent sedimentary records of a transitional semi-arid ecosystem susceptible to environmental forcing conditions. Coquimbo (30° S) region is characterized by dry summers and short rainfall periods during winter. The relatively wet-winter climate results from the interactions between the southern westerly winds and the South Pacific Anticyclone (SPA); in summer, the SPA moves southwards while in winter it returns to the north, allowing the passage of storm fronts. This semi-arid zone is strongly affected by variations associated with El Niño-Southern Oscillation (ENSO), caused by seasonal latitudinal changes in the SPA that produce high variability and precipitation in Chilean mid-latitudes. Sediment cores were retrieved in two bays, Guanaqueros and Tongoy, for geochemical analyses including: sensitive redox trace elements, biogenic opal, total organic carbon (TOC), diatoms, stable isotopes of organic carbon and nitrogen. The results suggest a main dry phase of high primary productivity concomitant with high fluxes of organic compounds to the bottom and suboxic-anoxic conditions in the sediments. This period reached a maximum at cal BC ~ 4500, followed by a continuous increase in wet conditions, low primary productivity and a more oxygenated environment towards the present, being remarkably stronger in the last 2000 years. We suggest that this might be associated with greater El Niño frequencies or similar conditions that increase precipitation, concomitantly with the introduction of oxygenated waters to coastal zones by the propagation of equatorial origin waves.

scholarly journals 14C activity of dissolved organic carbon fractions in the north-central Pacific and Sargasso Sea

Nature ◽  
1992 ◽  
Vol 357 (6380) ◽  
pp. 667-670 ◽  
Author(s):  
James E. Bauer ◽  
Peter M. Williams ◽  
Ellen R. M. Druffel
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Sargasso Sea ◽  
Central Pacific ◽  
North Central ◽  
Carbon Fractions ◽  
The North ◽  
Organic Carbon Fractions

scholarly journals "OAE 3" – regional Atlantic organic carbon burial during the Coniacian–Santonian

2012 ◽  
Vol 8 (5) ◽  
pp. 1447-1455 ◽  
Author(s):  
M. Wagreich
Keyword(s):  
Organic Carbon ◽  
Temporal Distribution ◽  
Black Shales ◽  
Time Interval ◽  
Temporal And Spatial Distribution ◽  
Oceanic Anoxic Event ◽  
The North ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Anoxic Event

Abstract. The Coniacian–Santonian time interval is the inferred time of oceanic anoxic event 3 (OAE 3), the last of the Cretaceous OAEs. A detailed look on the temporal and spatial distribution of organic-rich deposits attributed to OAE 3 suggests that black shale occurrences are restricted to the equatorial to mid-latitudinal Atlantic and adjacent basins, shelves and epicontinental seas like parts of the Caribbean, the Maracaibo Basin and the Western Interior Basin, and are largely absent in the Tethys, the North Atlantic, the southern South Atlantic, and the Pacific. Here, oxic bottom waters prevailed as indicated by the widespread occurrence of red deep-marine CORBs (Cretaceous Oceanic Red Beds). Widespread CORB sedimentation started during the Turonian after Oceanic Anoxic Event 2 (OAE 2) except in the Atlantic realm where organic-rich strata continue up to the Santonian. The temporal distribution of black shales attributed to OAE 3 indicates that organic-rich strata do not define a single and distinct short-time event, but are distributed over a longer time span and occur in different basins during different times. This suggests intermittent and regional anoxic conditions from the Coniacian to the Santonian. A comparison of time-correlated high-resolution δ13C curves for this interval indicates several minor positive excursions of up to 0.5‰, probably as a result of massive organic carbon burial cycles in the Atlantic. Regional wind-induced upwelling and restricted deep basins may have contributed to the development of anoxia during a time interval of widespread oxic conditions, thus highlighting the regional character of inferred OAE 3 as regional Atlantic event(s).

The Potential Impact of Agricultural Management and Climate Change on Soil Organic Carbon of the North Central Region of the United States

Ecosystems ◽  
2006 ◽  
Vol 9 (5) ◽  
pp. 816-827 ◽  
Author(s):  
Peter R. Grace ◽  
Manuel Colunga-Garcia ◽  
Stuart H. Gage ◽  
G. Philip Robertson ◽  
Gene R. Safir
Keyword(s):  
Climate Change ◽  
United States ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Central Region ◽  
The United States ◽  
North Central Region ◽  
North Central ◽  
The North ◽  
Potential Impact

Isotopic stratigraphy suggests Neoproterozoic ages and Laurentian ancestry for high-grade marbles from the North-Central Norwegian Caledonides

2002 ◽  
Vol 139 (4) ◽  
pp. 375-393 ◽  
Author(s):  
V. A. MELEZHIK ◽  
M. GOROKHOV ◽  
A. E. FALLICK ◽  
D. ROBERTS ◽  
A. B. KUZNETSOV ◽  
...  
Keyword(s):  
Late Ordovician ◽  
Time Interval ◽  
Low Grade ◽  
High Grade ◽  
North Central ◽  
The North ◽  
Strontium Isotope Stratigraphy ◽  
Dolomite Marble ◽  
Isotope Stratigraphy ◽  
Norwegian Caledonides

Carbon and strontium isotope stratigraphy has been applied to constrain the depositional ages of high-grade marble sequences in the Ofoten district of the North-Central Norwegian Caledonides. Two marble formations hosted by diverse schists from the Bogen Group, all previously correlated over long distances with a Late Ordovician–Early Silurian, low-grade, fossiliferous succession, have been studied for carbon, oxygen and strontium isotopes. The least altered 87Sr/86Sr ratios ranging between 0.7062 and 0.7068, and the best preserved δ13C values falling between +5.0 and +6.5‰ obtained from two marble formations, are consistent with a seawater composition in the time interval 700–600 Ma. The results obtained do not support the previously proposed correlation of the Bogen Group with an Ordovician–Silurian lithostratigraphic succession further north. The apparent depositional ages suggest that the tectonostratigraphic succession studied is inverted and that the tectonostratigraphy of the region requires revision. The Neoproterozoic depositional ages combined with the palaeogeographic position of Baltica imply that carbonates were initially accumulated in seas on a continental shelf, probably Laurentia, and were tectonically transported onto Baltica during Early Silurian, Scandian collision, at c. 425 Ma. Prospecting for new dolomite marble deposits of the Hekkelstrand type and carbonate-hosted manganese–iron ores should be restricted to 700–600 Ma sequences in the Uppermost Allochthon of the Norwegian Caledonides.

scholarly journals PRODUCTIVIDAD PRIMARIA EN LAGUNA LARGA, CAYO COCO, CUBA

2011 ◽  
Vol 3 ◽  
pp. 31 ◽  
Author(s):  
Mayrene Guimarais Bermejo ◽  
Roberto González de Zayas
Keyword(s):  
Primary Production ◽  
Primary Productivity ◽  
Net Primary Production ◽  
Ruppia Maritima ◽  
Halodule Wrightii ◽  
Phytoplankton Productivity ◽  
North Central ◽  
Net Production ◽  
The North ◽  
Total Productivity

Se determinó la productividad primaria en Laguna Larga, ubicada en la costa norte y central de Cayo Coco. La producción primaria del fitoplancton y la biomasa del macrofitobentos fueron medidas durante el 2008-2009 en dos sectores de la laguna. La producción primaria neta acuática del sector este fue de 4.32 ± 3.59 g C m-2 día-1 y en el sector oeste fue de 0.71 ± 0.41 g C m-2 día-1. Ambos sectores, atendiendo a la relación producción/respiración anual, fueron autotróficos para el oxígeno e hipertróficos para el carbono. Entre las especies más productivas del macrofitobentos estuvieron: Cladophoropsis sp., Halodule wrightii, Cladophora sp. y Ruppia maritima. La alta producción neta acuática registrada en el sector este, con respecto al oeste, se debe a la contribución del macrofitobentos a la productividad total. El fitoplancton en el sector este exhibió baja productividad (0.12 ± 0.07 g C m-2 día-1) con respecto al oeste (0.71 ± 0.41 g C m-2 día-1), lo que puede deberse a la competencia del macrofitobentos por los nutrientes.ABSTRACT Phytoplankton primary productivity and macrophyte biomass were determined during 2008-2009 for Laguna Larga, located on the north-central coast of Cayo Coco, Cuba. Aquatic net primary production was measured in two different sectors of the lagoon resulting in 4.32 ± 3.59 g C m-2 d-1 and 0.71 ± 0.41 g C m-2 d-1 in the eastern and western part, respectively. In regard to the annual production to respiration ratio, both sections showed autotrophic and hypertrophic levels for the oxygen and carbon metabolisms. The most productive species were Cladophoropsis sp., Halodule wrightii, Cladophora sp. and Ruppia maritima. Aquatic net production recorded for the eastern lobe was higher than the western lobe because of the macrophytobenthos contribution to total productivity. On the contrary, phytoplankton productivity in the eastern part was lower (0.12 ± 0.07 g C m-2 d-1) than the western lobe (0.71 ± 0.41 g C m-2 d-1), probably due to the macrophyte competition for nutrients.

scholarly journals Ecological Water Stress under Projected Climate Change across Hydroclimate Gradients in the North-Central United States

2019 ◽  
Vol 58 (9) ◽  
pp. 2103-2114 ◽  
Author(s):  
Arjun Adhikari ◽  
Andrew J. Hansen ◽  
Imtiaz Rangwala
Keyword(s):  
United States ◽  
Water Balance ◽  
Potential Evapotranspiration ◽  
Climate Projections ◽  
Moisture Index ◽  
Entire Study ◽  
North Central ◽  
The North ◽  
Central United States ◽  
High Emission

AbstractWater balance influences the distribution, abundance, and diversity of plant species across Earth’s terrestrial system. In this study, we examine changes in the water balance and, consequently, the dryland extent across eight ecoregions of the north-central United States by quantifying changes in the growing season (May–September) moisture index (MI) by 2071–99, relative to 1980–2005, under three high-resolution (~4 km) downscaled climate projections (CNRM-CM5, CCSM4, and IPSL-CM5A-MR) of high-emission scenarios (RCP8.5). We find that all ecoregions are projected to become drier as based on significant decreases in MI, except four ecoregions under CNRM-CM5, which projects relatively more moderate warming and much greater increases in precipitation relative to the other two projections. The mean projected MI across the entire study area changes by from +4% to −33%. The proportion of dryland (MI < 0.65) is projected to increase under all projections, but more significantly under the warmer and drier projections represented by CCSM4 and IPSL-CM5A-MR; these two projections also show the largest spatial increases in the arid (33%–53%) and hyperarid (135%–180%) dryland classes and the greatest decrease in the dry subhumid (from −56% to −88%) dryland class. Among the ecoregions, those in the semiarid class have the highest increase in potential evapotranspiration, those in the nondryland and dry subhumid class have the largest decrease in MI, and those in the dry subhumid class have the greatest increase in dryland extent. These changes are expected to have important implications for agriculture, ecological function, biodiversity, vegetation dynamics, and hydrological budget.

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