scholarly journals Modeling the impact ofTrichodesmiumand nitrogen fixation in the Atlantic Ocean

2004 ◽  
Vol 109 (C6) ◽  
Author(s):  
Victoria J. Coles
Keyword(s):  
Nitrogen Fixation ◽  
Atlantic Ocean ◽  
The Impact

scholarly journals Influence of the Amazon River on dissolved and intra-cellular metal concentrations in <i>Trichodesmium</i> colonies along the western boundary of the sub-tropical North Atlantic Ocean

2011 ◽  
Vol 8 (1) ◽  
pp. 217-225 ◽  
Author(s):  
A. Tovar-Sanchez ◽  
S. A. Sañudo-Wilhelmy
Keyword(s):  
Nitrogen Fixation ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Amazon River ◽  
Physical Parameters ◽  
Metal Concentrations ◽  
Field Samples ◽  
Metal Composition ◽  
The Impact

Abstract. Despite the ecological importance of Trichodesmium spp. for the global oceanic nitrogen budget, there is limited information on their trace metal composition in field samples. We report dissolved (<0.22 μm) metal concentrations measured in surface waters (Ag, Cd, Co, Cu, Fe, Mo, Ni, P, Pb and V) and in the total and the intracellular pool (Ag, Al, Cd, Co, Cu, Fe, Mn, Mo, Ni, P, Pb, V) of Trichodesmium populations collected in the western subtropical North Atlantic Ocean (April–May 2003) within the influence of the Amazon River plume. Dissolved element distributions were strongly influenced by the River discharge, with concentrations of some elements varying directly (i.e. Cd, Mo and V) or inversely (Ag, Co, Cu, Fe, Ni, P and Pb) with surface salinity. Intracellular metal values to phosphorous ratios (mol:mol) for Cd, Co, Cu, Fe, Mn, Mo, Ni and V ranged from 9.0 × 10−6 for Cd to 4.4 × 10−2 for Fe. Although total metal composition was significantly correlated with the intracellular content in the Trichodesmium colonies for some elements (e.g., Co, Cu, V), metal pools in the phytoplankton did not co-vary with the dissolved metal concentrations, suggesting that water column measurements may not be good predictors of the intracellular metal concentrations. The impact of physical parameters and bioactive elements on biological processes such as nitrogen fixation, carbon drawdown and biomass production in Trichodesmium colonies was explored by using a principal component analysis test (PCA). The analysis indicated that the biological drawdown of dissolved inorganic carbon (DIC) by Trichodesmium seems to be influenced by the internal content of Fe, Co, Cd, and Cu, while nitrogen fixation seems more influenced by mixed layer depth and dissolved Fe and Ni concentrations.

scholarly journals Modeling the impact of iron and phosphorus limitations on nitrogen fixation in the Atlantic Ocean

2006 ◽  
Vol 3 (5) ◽  
pp. 1391-1451 ◽  
Author(s):  
V. J. Coles ◽  
R. R. Hood
Keyword(s):  
Nitrogen Fixation ◽  
Atlantic Ocean ◽  
N2 Fixation ◽  
Iron Concentration ◽  
Near Surface ◽  
Dissolved Iron ◽  
Dynamic Representation ◽  
The Impact ◽  
Nitrogen Phosphorus ◽  
Do So

Abstract. The overarching goal of this study is to simulate subsurface N* (sensu, Gruber and Sarmiento, 1997) anomaly patterns in the North Atlantic Ocean and determine the basin wide rates of N2 fixation that are required to do so. We present results from an Atlantic implementation of a coupled physical-biogeochemical model that includes an explicit, dynamic representation of N2 fixation with light, nitrogen, phosphorus and iron limitations, and variable stoichiometric ratios. The model is able to reproduce nitrogen, phosphorus and iron concentration variability to first order. The latter is achieved by incorporating iron deposition directly into the model's detritus compartment which allows the model to reproduce sharp near surface gradients in dissolved iron concentration off the west coast of Africa and deep dissolved iron concentrations that have been observed in recent observational studies. The model can reproduce the large scale N* anomaly patterns but requires relatively high rates of surface nitrogen fixation to do so (1.8×1012 moles N yr−1 from 10° N–30° N, 3.4×1012 moles N yr

scholarly journals Modeling the impact of iron and phosphorus limitations on nitrogen fixation in the Atlantic Ocean

2007 ◽  
Vol 4 (4) ◽  
pp. 455-479 ◽  
Author(s):  
V. J. Coles ◽  
R. R. Hood
Keyword(s):  
Nitrogen Fixation ◽  
Atlantic Ocean ◽  
N2 Fixation ◽  
Iron Concentration ◽  
Fixation Rate ◽  
Near Surface ◽  
Dissolved Iron ◽  
The Impact ◽  
Nitrogen Phosphorus ◽  
Do So

Abstract. The overarching goal of this study is to simulate subsurface N* (sensu, Gruber and Sarmiento, 1997; GS97) anomaly patterns in the North Atlantic Ocean and determine the basin wide rates of N2-fixation that are required to do so. We present results from a new Atlantic implementation of a coupled physical-biogeochemical model that includes an explicit, dynamic representation of N2-fixation with light, nitrogen, phosphorus and iron limitations, and variable stoichiometric ratios. The model is able to reproduce nitrogen, phosphorus and iron concentration variability to first order. The latter is achieved by incorporating iron deposition directly into the model's detrital iron compartment which allows the model to reproduce sharp near surface gradients in dissolved iron concentration off the west coast of Africa and deep dissolved iron concentrations that have been observed in recent observational studies. The model can reproduce the large scale N* anomaly patterns but requires relatively high rates of surface nitrogen fixation to do so (1.8×1012 moles N yr−1 from 10° N–30° N, 3.4×1012 moles N yr−1 from 25° S–65° N). In the model the surface nitrogen fixation rate patterns are not co-located with subsurface gradients in N*. Rather, the fixed nitrogen is advected away from its source prior to generating a subsurface N* anomaly. Changes in the phosphorus remineralization rate (relative to nitrogen) linearly determine the surface nitrogen fixation rate because they change the degree of phosphorus limitation, which is the dominant limitation in the Atlantic in the model. Phosphorus remineralization rate must be increased by about a factor of 2 (relative to nitrogen) in order to generate subsurface N* anomalies that are comparable to the observations. We conclude that N2-fixation rate estimates for the Atlantic (and globally) may need to be revised upward, which will help resolve imbalances in the global nitrogen budget suggested by Codispoti et al. (2001) and Codispoti (2007).

scholarly journals Influence of the Amazon River on dissolved and intra-cellular metal concentrations in <i>Trichodesmium</i> colonies along the western boundary of the sub-tropical North Atlantic Ocean

2010 ◽  
Vol 7 (4) ◽  
pp. 6523-6543 ◽  
Author(s):  
A. Tovar-Sanchez ◽  
S. A. Sañudo-Wilhelmy
Keyword(s):  
Nitrogen Fixation ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Amazon River ◽  
Physical Parameters ◽  
Metal Concentrations ◽  
Field Samples ◽  
Metal Composition ◽  
The Impact

Abstract. Despite the ecological importance of Trichodesmium spp. for the global oceanic nitrogen budget, there is limited information on their trace metal composition in field samples. We report dissolved (<0.22 μm) metal concentrations measured in surface waters (Ag, Cd, Co, Cu, Fe, Mo, Ni, P, Pb and V) and in the total and the intracellular pool (Ag, Al, Cd, Co, Cu, Fe, Mn, Mo, Ni, P, Pb, V) of Trichodesmium populations collected in the western subtropical North Atlantic Ocean (April–May 2003) within the influence of the Amazon River plume. Dissolved element distributions were strongly influenced by the River discharge, with concentrations of some elements varying directly (i.e. Cd, Mo and V) or inversely (Ag, Co, Cu, Fe, Ni, P and Pb) with surface salinity. Intracellular metal values to phosphorous ratios (mol:mol) for Cd, Co, Cu, Fe, Mn, Mo, Ni and V ranged from 9.0×10−6 for Cd to 4.4×10−2 for Fe. Although total metal composition was significantly correlated with the intracellular content in the Trichodesmium colonies for some elements (e.g., Co, Cu, V), metal pools in the phytoplankton did not co-vary with the dissolved metal concentrations, suggesting that water column measurements may not be good predictors of the intracellular metal concentrations. The impact of physical parameters and bioactive elements on biological processes in Trichodesmium such as nitrogen fixation, carbon drawdown and biomass production was explored by using a principal component analysis test (PCA). The analysis indicates that the biological drawdown of dissolved inorganic carbon (DIC) by Trichodesmium seems to be influenced by the internal content of Fe, Co, Cd, Cu and Mn, while nitrogen fixation seems more influenced by the internal concentration of Mo, Ni and V and by the dissolved phosphorous concentrations.

scholarly journals Chemical aging of atmospheric mineral dust during transatlantic transport

2016 ◽  
Author(s):  
Mohamed Abdelkader ◽  
Swen Metzger ◽  
Benedikt Steil ◽  
Klaus Klingmüller ◽  
Holger Tost ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Direct Effect ◽  
Dust Particles ◽  
Hygroscopic Growth ◽  
Aging Effects ◽  
Particle Sedimentation ◽  
Inter Tropical Convergence Zone ◽  
Dust Transport ◽  
Dust Fraction ◽  
The Impact

Abstract. Transatlantic dust transport has many implications for the atmosphere, ocean and climate. We present a modeling study on the impact of the key processes (dust emissions flux, convection and dust aging parameterizations) that control the transatlantic dust transport. Typically, the Inter-Tropical Convergence Zone (ITCZ) acts as a barrier for the meridional dust transport. To characterize the dust outflow over the Atlantic Ocean, we address two regional phenomena: (i) dust interactions with the ITCZ (DIZ) and (ii) the adjacent dust transport over the Atlantic Ocean (DTA). In the DTA zone, the dust loading shows a steep and linear gradient westward over the Atlantic Ocean where particle sedimentation is the dominant removal process, whereas in the DIZ zone cloud interactions and wet deposition predominate. To study the different impacts of aging, we present two case studies that exclude condensation and coagulation, and include dust aging at various levels of complexity. For dust aging, we consider the uptake of inorganic acids on the surface of mineral particles that form salt compounds. Calcium, used as a proxy for the overall chemically reactive dust fraction, drives the dust-related neutralization reactions leading to higher dust aerosol optical depth (AOD). The aged dust particles are transferred to the soluble aerosol modes in the model and are mixed with other species that originate from anthropogenic and natural sources. The neutralization products (salts) take up water vapor from the atmosphere and increase the dust AOD under subsaturated conditions. We define the "direct effect of dust aging" to refer to the increase in AOD as a result of hygroscopic growth. On the other hand, the aged dust is more efficiently removed (wet and dry) because of the increase in particle size and hygroscopicity. This more efficient removal reduces the dust AOD over the DIZ zone. We define this as the "indirect effect of dust aging", complementary to the direct effect that is dominant in the DTA zone. Distinction of the two aging effects helps develop insight into the regional importance of dust–air-pollution interactions.

The impact of mesoscale eddies on the phytoplankton community in the South Atlantic Ocean: HPLC-CHEMTAX approach

2019 ◽  
Vol 144 ◽  
pp. 154-165 ◽  
Author(s):  
Andréa da Consolação de Oliveira Carvalho ◽  
Carlos Rafael B. Mendes ◽  
Rodrigo Kerr ◽  
José Luiz Lima de Azevedo ◽  
Felippe Galdino ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Phytoplankton Community ◽  
Mesoscale Eddies ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
The South ◽  
The Impact

scholarly journals How can effect the synergy of climate change, soil units and vegetation groups the potential global distribution of plants up to 2300: a modelling study for prediction of potential global distribution and migration of the N<sub>2</sub> fixing species <i>Alnus</i> spp.

2015 ◽  
Vol 12 (1) ◽  
pp. 815-864
Author(s):  
A. Sakalli
Keyword(s):  
Climate Change ◽  
Nitrogen Fixation ◽  
Global Distribution ◽  
Plant Distribution ◽  
Climate Change Scenarios ◽  
Climate System Model ◽  
Current Time ◽  
Soil Units ◽  
And Migration ◽  
The Impact

Abstract. Plant migration is a well known adaptation strategy of plant groups or species with evidence from historical to present observation and monitoring studies. Importance of N2-fixing plants has increased in last decades. Alnus (alder) is an important plant group because of its nitrogen fixation ability. Alders are generally distributed in humid locations of boreal, temperate and tropical climate zones, where the nitrogen fixation is an important nitrogen source for other plants. To model the nitrogen fixation by alder, data about the global distribution of alder is absolutely required. In this study a new method and model are presented to predict the distribution of N2-fixing genus on global scale and its migration in the future by using climate change scenarios. Three linear functions were defined for the determination of climate niche of alders. The distribution and migration model (Alnus-Distribution-Model (ADM)) was improved with the aid of the soil units from FAO-Unesco Soil Database, and vegetation types from Schmithüsen's biogeographical atlas. The model was also developed to predict the impact of climate change on alder distribution by using climate data from experiments performed by the Community Climate System Model version 4 (CCSM4) including the representative concentration pathways (RCPs) mitigation scenarios, and extensions of the scenarios beyond 2100 to 2300. The model covered basic approaches to understand the combine effect of climate, soil and vegetation on plant distribution and migration in the current time and future.

Long-term ventilation changes of Subpolar Mode Waters in the North Atlantic Ocean and its impact on the oxygen distribution

2021 ◽  
Author(s):  
Ilaria Stendardo ◽  
Bruno Buongiorno Nardelli ◽  
Sara Durante
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Horizontal Resolution ◽  
Late Winter ◽  
Mode Water ◽  
Mode Waters ◽  
The North ◽  
The North Atlantic ◽  
The Impact

&lt;p&gt;In the subpolar North Atlantic Ocean, Subpolar Mode Waters (SPMWs) are formed during late winter convection following the cyclonic circulation of the subpolar gyre. SPMWs participate in the upper flow of the Atlantic overturning circulation (AMOC) and provide much of the water that is eventually transformed into several components of the North Atlantic deep water (NADW), the cold, deep part of the AMOC. In a warming climate, an increase in upper ocean stratification is expected to lead to a reduced ventilation and a loss of oxygen. Thus, understanding how mode waters are affected by ventilation changes will help us to better understand the variability in the AMOC. In particular, we would like to address how the volume occupied by SPMWs has varied over the last decades due to ventilation changes, and what are the aspects driving the subpolar mode water formation, their interannual variations as well as the impact of the variability in the mixing and subduction and vertical dynamics on ocean deoxygenation. For this purpose, we use two observation-based 3D products from Copernicus Marine Service (CMEMS), the ARMOR3D and the OMEGA3D datasets. The first consists of 3D temperature and salinity fields, from the surface to 1500 m depth, available weekly over a regular grid at 1/4&amp;#176; horizontal resolution from 1993 to present. The second consists of observation-based quasi-geostrophic vertical and horizontal ocean currents with the same temporal and spatial resolution as ARMOR3D.&lt;/p&gt;

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