scholarly journals Regional impacts of iron-light colimitation in a global biogeochemical model

2009 ◽  
Vol 6 (4) ◽  
pp. 7517-7564 ◽  
Author(s):  
E. D. Galbraith ◽  
A. Gnanadesikan ◽  
J. P. Dunne ◽  
M. R. Hiscock
Keyword(s):  
Photosynthetic Efficiency ◽  
Light Harvesting ◽  
Field Studies ◽  
Iron Limitation ◽  
Light Limitation ◽  
Biogeochemical Model ◽  
Regional Impacts ◽  
Small Phytoplankton ◽  
Cellular Machinery ◽  
Ocean Environment

Abstract. Laboratory and field studies have revealed that iron has multiple roles in phytoplankton physiology, with particular importance for light-harvesting cellular machinery. However, although iron-limitation is explicitly included in numerous biogeochemical/ecosystem models, its implementation varies, and its effect on the efficiency of light harvesting is often ignored. Given the complexity of the ocean environment, it is difficult to predict the consequences of applying different iron limitation schemes. Here we explore the interaction of iron and nutrient cycles using a new, streamlined model of ocean biogeochemistry. Building on previously published parameterizations of photoadaptation and export production, the Biogeochemistry with Light Iron Nutrients and Gasses (BLING) model is constructed with only three explicit tracers but including macronutrient and micronutrient limitation, light limitation, and an implicit treatment of community structure. The structural simplicity of this computationally inexpensive model allows us to clearly isolate the global effects of iron availability on maximum light-saturated photosynthesis rates from those of photosynthetic efficiency. We find that the effect on light-saturated photosynthesis rates is dominant, negating the importance of photosynthetic efficiency in most regions, especially the cold waters of the Southern Ocean. The primary exceptions to this occur in iron-rich regions of the Northern Hemisphere, where high light-saturated photosynthesis rates cause photosynthetic efficiency to play a more important role. Additionally, we speculate that the small phytoplankton dominating iron-limited regions tend to have relatively high photosynthetic efficiency, such that iron-limitation has less of a deleterious effect on growth rates than would be expected from short-term iron addition experiments.

scholarly journals Regional impacts of iron-light colimitation in a global biogeochemical model

2010 ◽  
Vol 7 (3) ◽  
pp. 1043-1064 ◽  
Author(s):  
E. D. Galbraith ◽  
A. Gnanadesikan ◽  
J. P. Dunne ◽  
M. R. Hiscock
Keyword(s):  
General Circulation ◽  
Photosynthetic Efficiency ◽  
Light Harvesting ◽  
Circulation Model ◽  
Field Studies ◽  
Ocean General Circulation Model ◽  
Iron Limitation ◽  
Light Limitation ◽  
Biogeochemical Model ◽  
Ocean Environment

Abstract. Laboratory and field studies have revealed that iron has multiple roles in phytoplankton physiology, with particular importance for light-harvesting cellular machinery. However, although iron-limitation is explicitly included in numerous biogeochemical/ecosystem models, its implementation varies, and its effect on the efficiency of light harvesting is often ignored. Given the complexity of the ocean environment, it is difficult to predict the consequences of applying different iron limitation schemes. Here we explore the interaction of iron and nutrient cycles in an ocean general circulation model using a new, streamlined model of ocean biogeochemistry. Building on previously published parameterizations of photoadaptation and export production, the Biogeochemistry with Light Iron Nutrients and Gasses (BLING) model is constructed with only four explicit tracers but including macronutrient and micronutrient limitation, light limitation, and an implicit treatment of community structure. The structural simplicity of this computationally-inexpensive model allows us to clearly isolate the global effect that iron availability has on maximum light-saturated photosynthesis rates vs. the effect iron has on photosynthetic efficiency. We find that the effect on light-saturated photosynthesis rates is dominant, negating the importance of photosynthetic efficiency in most regions, especially the cold waters of the Southern Ocean. The primary exceptions to this occur in iron-rich regions of the Northern Hemisphere, where high light-saturated photosynthesis rates allow photosynthetic efficiency to play a more important role. In other words, the ability to efficiently harvest photons has little effect in regions where light-saturated growth rates are low. Additionally, we speculate that the phytoplankton cells dominating iron-limited regions tend to have relatively high photosynthetic efficiency, due to reduced packaging effects. If this speculation is correct, it would imply that natural communities of iron-stressed phytoplankton may tend to harvest photons more efficiently than would be inferred from iron-limitation experiments with other phytoplankton. We suggest that iron limitation of photosynthetic efficiency has a relatively small impact on global biogeochemistry, though it is expected to impact the seasonal cycle of plankton as well as the vertical structure of primary production.

Enhanced Biological Photosynthetic Efficiency Using Light-Harvesting Engineering with Dual-Emissive Carbon Dots

2018 ◽  
Vol 28 (44) ◽  
pp. 1804004 ◽  
Author(s):  
Wei Li ◽  
Shuangshuang Wu ◽  
Haoran Zhang ◽  
Xuejie Zhang ◽  
Jianle Zhuang ◽  
...  
Keyword(s):  
Carbon Dots ◽  
Photosynthetic Efficiency ◽  
Light Harvesting

scholarly journals Mechanisms of northern North Atlantic biomass variability

2018 ◽  
Vol 15 (20) ◽  
pp. 6049-6066 ◽  
Author(s):  
Galen A. McKinley ◽  
Alexis L. Ritzer ◽  
Nicole S. Lovenduski
Keyword(s):  
North Atlantic ◽  
North Atlantic Ocean ◽  
Light Availability ◽  
Light Limitation ◽  
Climate Indices ◽  
Biogeochemical Model ◽  
Full Time ◽  
Subpolar Gyre ◽  
Phosphate Supply ◽  
Biomass Variability

Abstract. In the North Atlantic Ocean north of 40∘ N, intense biological productivity occurs to form the base of a highly productive marine food web. SeaWiFS satellite observations indicate trends of biomass in this region over 1998–2007. Significant biomass increases occur in the northwest subpolar gyre and there are simultaneous significant declines to the east of 30–35∘ W. These short-term changes, attributable to internal variability, offer an opportunity to explore the mechanisms of the coupled physical–biogeochemical system. We use a regional biogeochemical model that captures the observed changes for this exploration. Biomass increases in the northwest are due to a weakening of the subpolar gyre and associated shoaling of mixed layers that relieves light limitation. Biomass declines to the east of 30–35∘ W are due to reduced horizontal convergence of phosphate. This reduced convergence is attributable to declines in vertical phosphate supply in the regions of deepest winter mixing that lie to the west of 30–35∘ W. Over the full time frame of the model experiment, 1949–2009, variability of both horizontal and vertical phosphate supply drive variability in biomass on the northeastern flank of the subtropical gyre. In the northeast subpolar gyre horizontal fluxes drive biomass variability for both time frames. Though physically driven changes in nutrient supply or light availability are the ultimate drivers of biomass changes, clear mechanistic links between biomass and standard physical variables or climate indices remain largely elusive.

scholarly journals Mechanisms controlling primary and new production in a global ecosystem model – Part II: The role of the upper ocean short-term periodic and episodic mixing events

Ocean Science ◽  
2006 ◽  
Vol 2 (2) ◽  
pp. 267-279 ◽  
Author(s):  
E. E. Popova ◽  
A. C. Coward ◽  
G. A. Nurser ◽  
B. de Cuevas ◽  
T. R. Anderson
Keyword(s):  
Primary Production ◽  
Diurnal Cycle ◽  
Ecosystem Dynamics ◽  
Light Limitation ◽  
Biogeochemical Model ◽  
Late Winter ◽  
Short Term ◽  
New Production ◽  
Storm Activity ◽  
Diurnal Variability

Abstract. The use of 6 h, daily, weekly and monthly atmospheric forcing resulted in dramatically different predictions of plankton productivity in a global 3-D coupled physical-biogeochemical model. Resolving the diurnal cycle of atmospheric variability by use of 6 h forcing, and hence also diurnal variability in UML depth, produced the largest difference, reducing predicted global primary and new production by 25% and 10% respectively relative to that predicted with daily and weekly forcing. This decrease varied regionally, being a 30% reduction in equatorial areas primarily because of increased light limitation resulting from deepening of the mixed layer overnight as well as enhanced storm activity, and 25% at moderate and high latitudes primarily due to increased grazing pressure resulting from late winter stratification events. Mini-blooms of phytoplankton and zooplankton occur in the model during these events, leading to zooplankton populations being sufficiently well developed to suppress the progress of phytoplankton blooms. A 10% increase in primary production was predicted in the peripheries of the oligotrophic gyres due to increased storm-induced nutrient supply end enhanced winter production during the short term stratification events that are resolved in the run forced by 6 h meteorological fields. By resolving the diurnal cycle, model performance was significantly improved with respect to several common problems: underestimated primary production in the oligotrophic gyres; overestimated primary production in the Southern Ocean; overestimated magnitude of the spring bloom in the subarctic Pacific Ocean, and overestimated primary production in equatorial areas. The result of using 6 h forcing on predicted ecosystem dynamics was profound, the effects persisting far beyond the hourly timescale, and having major consequences for predicted global and new production on an annual basis.

scholarly journals Mixed layer depth dominates over upwelling in regulating the seasonality of ecosystem functioning in the Peruvian Upwelling System

2021 ◽  
Author(s):  
Tianfei Xue ◽  
Ivy Frenger ◽  
A. E. Friederike Prowe ◽  
Yonss Saranga José ◽  
Andreas Oschlies
Keyword(s):  
Ocean Circulation ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Marine Ecosystem ◽  
Phase Relationship ◽  
Light Limitation ◽  
Biogeochemical Model ◽  
Upwelling System ◽  
Mixed Layers ◽  
Chlorophyll Concentrations

Abstract. The Peruvian Upwelling System hosts an extremely high productive marine ecosystem. Observations show that the Peruvian Upwelling System is the only Eastern Boundary Upwelling Systems (EBUS) with an out-of-phase relationship of seasonal surface chlorophyll concentrations and upwelling intensity. This "seasonal paradox" triggers the questions: (1) what is the uniqueness of the Peruvian Upwelling System compared with other EBUS that leads to the out of phase relationship; (2) how does this uniqueness lead to low phytoplankton biomass in austral winter despite strong upwelling and ample nutrients? Using observational climatologies for four EBUS we diagnose that the Peruvian Upwelling System is unique in that intense upwelling coincides with deep mixed layers. We then apply a coupled regional ocean circulation-biogeochemical model (CROCO-BioEBUS) to assess how the interplay between mixed layer and upwelling is regulating the seasonality of surface chlorophyll in the Peruvian Upwelling System. The model recreates the "seasonal paradox" within 200 km off the Peruvian coast. We confirm previous findings that deep mixed layers, which cause vertical dilution and stronger light limitation, mostly drive the diametrical seasonality of chlorophyll relative to upwelling. In contrast to previous studies, reduced phytoplankton growth due to enhanced upwelling of cold waters and lateral advection are second-order drivers of low surface chlorophyll concentrations. This impact of deep mixed layers and upwelling propagates up the ecosystem, from primary production to export efficiency. Our findings emphasize the crucial role of the interplay of the mixed layer and upwelling and suggest that surface chlorophyll may increase along with a weakened seasonal paradox in response to shoaling mixed layers under climate change.

scholarly journals Mechanisms of northern North Atlantic biomass variability

2018 ◽  
Author(s):  
Galen A. McKinley ◽  
Alexis L. Ritzer ◽  
Nicole S. Lovenduski
Keyword(s):  
North Atlantic ◽  
Light Availability ◽  
Light Limitation ◽  
Climate Indices ◽  
Biogeochemical Model ◽  
Subpolar Gyre ◽  
The North ◽  
Phosphate Supply ◽  
The North Atlantic ◽  
Biomass Variability

Abstract. In the North Atlantic Ocean north of 40° N, intense biological productivity occurs to form the base of a highly productive marine food web. SeaWiFS satellite observations indicate trends of biomass in this region over 1998–2007. Significant biomass increases occur in the northwest subpolar gyre and there are simultaneous significant declines to the east of 30–35° W. In this study, we use a regional biogeochemical model of the North Atlantic that captures the observed trends to determine their mechanistic drivers. Biomass increases in the northwest are due to a weakening of the subpolar gyre and associated shoaling of mixed layers that relieves light limitation. Biomass declines to the east of 30–35° W are due to reduced horizontal convergence of phosphate. This reduced convergence is attributable to declines in vertical phosphate supply in the regions of deepest winter mixing that lie to the west of 30–35° W. Over the full timeframe of the model experiment, 1949–2009, variability of both horizontal and vertical phosphate supply drive variability in biomass on the northeastern flank of the subtropical gyre. In the northeast subpolar gyre horizontal fluxes drive biomass variability for both timeframes. Though physically-driven changes in nutrient supply or light availability are the ultimate drivers of biomass changes, clear mechanistic links between biomass and standard physical variables or climate indices remain largely elusive.

scholarly journals Estimating particle export flux from satellite observations: Challenges associated with spatial and temporal decoupling of production and export

2019 ◽  
Vol 77 (2) ◽  
pp. 247-258
Author(s):  
Dennis J. McGillicuddy ◽  
Laure Resplandy ◽  
Marina Lévy
Keyword(s):  
Phytoplankton Biomass ◽  
Net Primary Production ◽  
Field Studies ◽  
Particulate Material ◽  
Biogeochemical Model ◽  
Annual Average ◽  
Export Flux ◽  
Basin Scale ◽  
Particle Export ◽  
Tight Correlation

Recent studies have suggested that accurate predictions of particle export flux can be derived from satellite-based estimates of phytoplankton biomass and net primary production (NPP), combined with models of the food web. We evaluate the performance of this approach using the output of a highresolution, basin-scale coupled physical-biogeochemical model. There is tight correlation between the annual mean export flux simulated by the biogeochemical model and that predicted by the satellitebased algorithm driven by NPP from the model. Although the satellite-based approach performs well on the annual average, there are significant departures during the course of the year, particularly in spring. NPP and export flux can also become decoupled at the mesoscale, when the dynamics of fronts and eddies cause export to be displaced in space and/or time from the productivity event generating the particulate material. These findings have significant implications for the design of field studies aimed at reducing uncertainties in estimates of export flux.

Mercury dynamics in a changing coastal area over industrial and post-industrial phases

2020 ◽  
Author(s):  
Ginevra Rosati ◽  
Cosimo Solidoro ◽  
Donata Melaku Canu
Keyword(s):  
Atmospheric Deposition ◽  
Environmental Changes ◽  
Sediment Resuspension ◽  
Field Studies ◽  
Ecosystem Approach ◽  
Venice Lagoon ◽  
Biogeochemical Model ◽  
Anthropogenic Pressures ◽  
The One ◽  
Post Industrial

<p>The Venice Lagoon (Mediterranean Sea) is a shallow coastal lagoon that have been subjected to several anthropogenic pressures, including significant Hg loadings from industrial activities. Inorganic Hg is methylated to neurotoxic MeHg in lagoon water and sediment, posing the ecosystem wealth at risk.</p><p>Here, we use a biogeochemical model to investigate the long-term dynamics of Hg species in the Venice Lagoon from the pre-industrial period to the post-industrial period (1900-2100), also taking into account environmental changes occurred in the lagoon such as eutrophication, and the increase of sediment resuspension driven by manila clam harvesting.</p><p>Time-variable Hg emissions from industries were estimated from available information about industrial production and technology-dependent emissions factors, while Hg loading species from other sources (river, atmospheric deposition, urban wastes) where estimated through downscaling from global studies, using observations from previous field studies (1970 - 2010) as constraints. The impacts of future trends of Hg atmospheric deposition are explored through scenario analysis. </p><p>Modeled Hg species are in a satisfactory agreement with the available observations. In the current postindustrial phase, Hg<sub>T</sub> in the lagoon waters comes mostly from sediments, while MeHg comes primarily from the watershed.</p><p>We estimate in ∼56 kg y<sup>-1</sup> the HgT export for 2019 to the Adriatic Sea, which includes ∼0.13 kg y<sup>-1</sup> of MeHg. Both Hg and MeHg concentrations are decreasing since outputs slightly exceed inputs. The analysis of Hg and MeHg reservoirs and fluxes reveals the impacts of the changes in environmental conditions on Hg fluxes. On the one hand, eutrophication has enhanced sediment deposition to the seabed, causing a maximum in sediment Hg concentrations when Hg inputs were already declining; on the other hand, the enhanced sediment resuspension due to clam harvesting led to increased Hg fluxes from the sediment to the water, also causing a redistribution of Hg from the central lagoon to the northern and southern areas, as reported by observational studies. These results emphasize the importance of adopting an ecosystem approach when investigating Hg dynamics, considering the different uses of the ecosystem.</p>

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