Contiguous Low Oxygen Waters between the Continental Shelf Hypoxia Zone and Nearshore Coastal Waters of Louisiana, USA: Interpreting 30 Years of Profiling Data and Three-Dimensional Ecosystem Modeling

2021 ◽  
Vol 55 (8) ◽  
pp. 4709-4719
Author(s):  
Brandon M. Jarvis ◽  
Richard M. Greene ◽  
Yongshan Wan ◽  
John C. Lehrter ◽  
Lisa L. Lowe ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Coastal Waters ◽  
Three Dimensional ◽  
Ecosystem Modeling ◽  
Low Oxygen

scholarly journals Haemoglobin polymorphisms affect the oxygen-binding properties in Atlantic cod populations

2008 ◽  
Vol 276 (1658) ◽  
pp. 833-841 ◽  
Author(s):  
Øivind Andersen ◽  
Ola Frang Wetten ◽  
Maria Cristina De Rosa ◽  
Carl Andre ◽  
Cristiana Carelli Alinovi ◽  
...  
Keyword(s):  
Evolutionary Biology ◽  
Quaternary Structure ◽  
Atlantic Cod ◽  
Three Dimensional ◽  
Oxygen Affinity ◽  
Oxygen Binding ◽  
Low Oxygen ◽  
Binding Properties ◽  
Important Species ◽  
The North

A major challenge in evolutionary biology is to identify the genes underlying adaptation. The oxygen-transporting haemoglobins directly link external conditions with metabolic needs and therefore represent a unique system for studying environmental effects on molecular evolution. We have discovered two haemoglobin polymorphisms in Atlantic cod populations inhabiting varying temperature and oxygen regimes in the North Atlantic. Three-dimensional modelling of the tetrameric haemoglobin structure demonstrated that the two amino acid replacements Met55β 1 Val and Lys62β 1 Ala are located at crucial positions of the α 1 β 1 subunit interface and haem pocket, respectively. The replacements are proposed to affect the oxygen-binding properties by modifying the haemoglobin quaternary structure and electrostatic feature. Intriguingly, the same molecular mechanism for facilitating oxygen binding is found in avian species adapted to high altitudes, illustrating convergent evolution in water- and air-breathing vertebrates to reduction in environmental oxygen availability. Cod populations inhabiting the cold Arctic waters and the low-oxygen Baltic Sea seem well adapted to these conditions by possessing the high oxygen affinity Val55–Ala62 haplotype, while the temperature-insensitive Met55–Lys62 haplotype predominates in the southern populations. The distinct distributions of the functionally different haemoglobin variants indicate that the present biogeography of this ecologically and economically important species might be seriously affected by global warming.

scholarly journals Challenges associated with modeling low-oxygen waters in Chesapeake Bay: a multiple model comparison

2016 ◽  
Vol 13 (7) ◽  
pp. 2011-2028 ◽  
Author(s):  
Isaac D. Irby ◽  
Marjorie A. M. Friedrichs ◽  
Carl T. Friedrichs ◽  
Aaron J. Bever ◽  
Raleigh R. Hood ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Chesapeake Bay ◽  
Mixed Layer ◽  
Model Comparison ◽  
Three Dimensional ◽  
Surface Mixed Layer ◽  
Multiple Model ◽  
Low Oxygen ◽  
Mixing Depth ◽  
Biogeochemical Models

Abstract. As three-dimensional (3-D) aquatic ecosystem models are used more frequently for operational water quality forecasts and ecological management decisions, it is important to understand the relative strengths and limitations of existing 3-D models of varying spatial resolution and biogeochemical complexity. To this end, 2-year simulations of the Chesapeake Bay from eight hydrodynamic-oxygen models have been statistically compared to each other and to historical monitoring data. Results show that although models have difficulty resolving the variables typically thought to be the main drivers of dissolved oxygen variability (stratification, nutrients, and chlorophyll), all eight models have significant skill in reproducing the mean and seasonal variability of dissolved oxygen. In addition, models with constant net respiration rates independent of nutrient supply and temperature reproduced observed dissolved oxygen concentrations about as well as much more complex, nutrient-dependent biogeochemical models. This finding has significant ramifications for short-term hypoxia forecasts in the Chesapeake Bay, which may be possible with very simple oxygen parameterizations, in contrast to the more complex full biogeochemical models required for scenario-based forecasting. However, models have difficulty simulating correct density and oxygen mixed layer depths, which are important ecologically in terms of habitat compression. Observations indicate a much stronger correlation between the depths of the top of the pycnocline and oxycline than between their maximum vertical gradients, highlighting the importance of the mixing depth in defining the region of aerobic habitat in the Chesapeake Bay when low-oxygen bottom waters are present. Improvement in hypoxia simulations will thus depend more on the ability of models to reproduce the correct mean and variability of the depth of the physically driven surface mixed layer than the precise magnitude of the vertical density gradient.

scholarly journals Proton Pumping and Non-Pumping Terminal Respiratory Oxidases: Active Sites Intermediates of These Molecular Machines and Their Derivatives

2021 ◽  
Vol 22 (19) ◽  
pp. 10852
Author(s):  
Sergey A. Siletsky ◽  
Vitaliy B. Borisov
Keyword(s):  
Active Sites ◽  
Three Dimensional ◽  
Molecular Machines ◽  
Proton Pumping ◽  
Stress Reactions ◽  
Low Oxygen ◽  
Functional Studies ◽  
Wide Range ◽  
Regulatory Cascades ◽  
Respiratory Oxidases

Terminal respiratory oxidases are highly efficient molecular machines. These most important bioenergetic membrane enzymes transform the energy of chemical bonds released during the transfer of electrons along the respiratory chains of eukaryotes and prokaryotes from cytochromes or quinols to molecular oxygen into a transmembrane proton gradient. They participate in regulatory cascades and physiological anti-stress reactions in multicellular organisms. They also allow microorganisms to adapt to low-oxygen conditions, survive in chemically aggressive environments and acquire antibiotic resistance. To date, three-dimensional structures with atomic resolution of members of all major groups of terminal respiratory oxidases, heme-copper oxidases, and bd-type cytochromes, have been obtained. These groups of enzymes have different origins and a wide range of functional significance in cells. At the same time, all of them are united by a catalytic reaction of four-electron reduction in oxygen into water which proceeds without the formation and release of potentially dangerous ROS from active sites. The review analyzes recent structural and functional studies of oxygen reduction intermediates in the active sites of terminal respiratory oxidases, the features of catalytic cycles, and the properties of the active sites of these enzymes.

Fronts and shelf-circulation models

1981 ◽  
Vol 302 (1472) ◽  
pp. 597-604 ◽  
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Continental Shelf ◽  
Satellite Imagery ◽  
Three Dimensional ◽  
Shelf Circulation ◽  
Eddy Formation ◽  
Coastal Front

Satellite imagery shows that fronts and frontal eddies are widespread on the northwest European continental shelf. The implications for the numerical modelling of transports (for example, of pollutants) are discussed. A brief review of some models of shelf circulation is given. It is argued that to include fronts in models of shelf circulation requires a better understanding of dynamics on the frontal scale. A three-dimensional numerical model of eddy formation in a coastal front is then presented that reproduces many of the observed features.

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