scholarly journals Redox-Controlled Ammonium Storage and Overturn in Ediacaran Oceans

2021 ◽  
Vol 9 ◽  
Author(s):  
Christian Hallmann ◽  
Emmanuelle Grosjean ◽  
Nathan D. Shapiro ◽  
Yuichiro Kashiyama ◽  
Yoshito Chikaraishi ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Surface Waters ◽  
Primary Productivity ◽  
Environmental Conditions ◽  
Ammonium Assimilation ◽  
Early Cambrian ◽  
Anoxygenic Phototrophs ◽  
Molecular Speciation ◽  
Variable Regime ◽  
Chlorophyll Derivatives

As a key nutrient, nitrogen can limit primary productivity and carbon cycle dynamics, but also evolutionary progress. Given strong redox-dependency of its molecular speciation, environmental conditions can control nitrogen localization and bioavailability. This particularly applies to periods in Earth history with strong and frequent redox fluctuations, such as the Neoproterozoic. We here report on chlorophyll-derived porphyrins and maleimides in Ediacaran sediments from Oman. Exceptionally light δ15N values (< –10‰) in maleimides derived from anoxygenic phototrophs point towards ammonium assimilation at the chemocline, whereas the isotopic offset between kerogens and chlorophyll-derivatives indicates a variable regime of cyanobacterial and eukaryotic primary production in surface waters. Biomarker and maleimide mass balance considerations imply shallow euxinia during the terminal Ediacaran and a stronger contribution of anoxygenic phototrophs to primary productivity, possibly as a consequence of nutrient ‘lockup’ in a large anoxic ammonium reservoir. Synchronous δ13C and δ15N anomalies at the Ediacaran–Cambrian boundary may reflect one in a series of overturn events, mixing ammonium and isotopically-light DIC into oxic surface waters. By modulating access to nitrogen, environmental redox conditions may have periodically affected Ediacaran primary productivity, carbon cycle perturbations, and possibly played a role in the timing of the metazoan radiation across the terminal Ediacaran and early Cambrian.

scholarly journals Predicting photosynthesis and transpiration responses to ozone: decoupling modeled photosynthesis and stomatal conductance

2012 ◽  
Vol 9 (8) ◽  
pp. 3113-3130 ◽  
Author(s):  
D. Lombardozzi ◽  
S. Levis ◽  
G. Bonan ◽  
J. P. Sparks
Keyword(s):  
Carbon Dioxide ◽  
Stomatal Conductance ◽  
Primary Productivity ◽  
Environmental Conditions ◽  
Water Exchange ◽  
Global Scale ◽  
Community Land Model ◽  
Climate Regulation ◽  
The Tropics ◽  
Tulip Poplar

Abstract. Plants exchange greenhouse gases carbon dioxide and water with the atmosphere through the processes of photosynthesis and transpiration, making them essential in climate regulation. Carbon dioxide and water exchange are typically coupled through the control of stomatal conductance, and the parameterization in many models often predict conductance based on photosynthesis values. Some environmental conditions, like exposure to high ozone (O3) concentrations, alter photosynthesis independent of stomatal conductance, so models that couple these processes cannot accurately predict both. The goals of this study were to test direct and indirect photosynthesis and stomatal conductance modifications based on O3 damage to tulip poplar (Liriodendron tulipifera) in a coupled Farquhar/Ball-Berry model. The same modifications were then tested in the Community Land Model (CLM) to determine the impacts on gross primary productivity (GPP) and transpiration at a constant O3 concentration of 100 parts per billion (ppb). Modifying the Vcmax parameter and directly modifying stomatal conductance best predicts photosynthesis and stomatal conductance responses to chronic O3 over a range of environmental conditions. On a global scale, directly modifying conductance reduces the effect of O3 on both transpiration and GPP compared to indirectly modifying conductance, particularly in the tropics. The results of this study suggest that independently modifying stomatal conductance can improve the ability of models to predict hydrologic cycling, and therefore improve future climate predictions.

scholarly journals FITOPLANKTON DAN SIKLUS KARBON GLOBAL

OSEANA ◽  
2019 ◽  
Vol 44 (2) ◽  
pp. 35-48
Author(s):  
Mochamad Ramdhan Firdaus ◽  
Lady Ayu Sri Wijayanti
Keyword(s):  
Carbon Cycle ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Sedimentary Rocks ◽  
Global Carbon Cycle ◽  
Biological Pump ◽  
Large Role ◽  
The World ◽  
Pump Mechanism ◽  
Global Carbon

PHYTOPLANKTON AND GLOBAL CARBON CYCLE. Scientists around the world believe that phytoplankton, although microscopic, have a large role in the global carbon cycle. Various research results show that the net primary productivity of all phytoplankton in the sea is almost as large as the net primary productivity of all plants on land. Phytoplankton through the process of photosynthesis absorbs 40-50 PgC / year from the atmosphere. Also, phytoplankton is known to be responsible for transporting carbon from the atmosphere to the seafloor through the carbon biological pump mechanism. Phytoplankton from the coccolithophores group is known to play a role in the sequestration of carbon on the seabed through the carbonate pump mechanism. The mechanism is capable of sequestering carbon for thousands of years on the seabed in the form of sedimentary rocks (limestone).

scholarly journals Investigation of the abundance, distribution and composition of microplastics at coastal upwelling sites in the Atlantic Ocean

2016 ◽  
Author(s):  
La Daana K Kanhai ◽  
Rick Officer ◽  
Ian O'Connor ◽  
Richard C Thompson
Keyword(s):  
Atlantic Ocean ◽  
Surface Waters ◽  
Primary Productivity ◽  
Null Hypothesis ◽  
Latitudinal Gradient ◽  
Coastal Upwelling ◽  
Abundance Distribution ◽  
Significant Difference ◽  
Benguela Upwelling ◽  
Canary Upwelling

Microplastics are an issue of international concern due to the fact that these substances may potentially threaten biota by (i) causing physical harm, (ii) transporting persistent, bioaccumulating and toxic (PBT) substances and, (iii) leaching plastic additives. Within the world’s oceans, areas which experience coastal upwelling are biota rich due to their high levels of primary productivity. The assessment of microplastic presence in areas which experience coastal upwelling is vital as it will indicate whether microplastics are an issue of concern in areas which support key biological resources. The null hypothesis of the present study is that microplastic abundance will be lower in areas where there is upwelling. As such, the present study aims to investigate whether microplastic abundance in upwelled areas in the Atlantic Ocean is significantly different from non-upwelled areas. Based on an opportunistic voyage aboard the RV Polarstern, microplastics will be sampled in sub-surface waters along a diverse latitudinal gradient in the Atlantic Ocean i.e. from Bremerhaven (Germany) to Cape Town (South Africa). Based on the proposed route, it will be possible to determine microplastic levels at two areas of coastal upwelling in the Atlantic Ocean (i) Canary Upwelling Ecosystem (CUE) and (ii) Benguela Upwelling Ecosystem (BUE). The results will then be analysed to determine whether there was a statistically significant difference between ‘upwelled areas’ and ‘non-upwelled areas’.

Carbon: Chlorophyll Ratios and Net Primary Productivity of Subarctic Pacific Surface Waters Derived From Autonomous Shipboard Sensors

2018 ◽  
Vol 32 (2) ◽  
pp. 267-288 ◽  
Author(s):  
William J. Burt ◽  
Toby K. Westberry ◽  
Michael J. Behrenfeld ◽  
Chen Zeng ◽  
Robert W. Izett ◽  
...  
Keyword(s):  
Surface Waters ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Subarctic Pacific

scholarly journals Rapid ocean acidification and protracted Earth system recovery followed the end-Cretaceous Chicxulub impact

2019 ◽  
Vol 116 (45) ◽  
pp. 22500-22504 ◽  
Author(s):  
Michael J. Henehan ◽  
Andy Ridgwell ◽  
Ellen Thomas ◽  
Shuang Zhang ◽  
Laia Alegret ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Ocean Acidification ◽  
Carbon Isotope ◽  
Primary Productivity ◽  
Deep Sea ◽  
Mass Extinction ◽  
System Modeling ◽  
Earth System ◽  
Ph Gradients ◽  
Chicxulub Impact

Mass extinction at the Cretaceous–Paleogene (K-Pg) boundary coincides with the Chicxulub bolide impact and also falls within the broader time frame of Deccan trap emplacement. Critically, though, empirical evidence as to how either of these factors could have driven observed extinction patterns and carbon cycle perturbations is still lacking. Here, using boron isotopes in foraminifera, we document a geologically rapid surface-ocean pH drop following the Chicxulub impact, supporting impact-induced ocean acidification as a mechanism for ecological collapse in the marine realm. Subsequently, surface water pH rebounded sharply with the extinction of marine calcifiers and the associated imbalance in the global carbon cycle. Our reconstructed water-column pH gradients, combined with Earth system modeling, indicate that a partial ∼50% reduction in global marine primary productivity is sufficient to explain observed marine carbon isotope patterns at the K-Pg, due to the underlying action of the solubility pump. While primary productivity recovered within a few tens of thousands of years, inefficiency in carbon export to the deep sea lasted much longer. This phased recovery scenario reconciles competing hypotheses previously put forward to explain the K-Pg carbon isotope records, and explains both spatially variable patterns of change in marine productivity across the event and a lack of extinction at the deep sea floor. In sum, we provide insights into the drivers of the last mass extinction, the recovery of marine carbon cycling in a postextinction world, and the way in which marine life imprints its isotopic signal onto the geological record.

scholarly journals Aquatic and terrestrial cyanobacteria produce methane

2020 ◽  
Vol 6 (3) ◽  
pp. eaax5343 ◽  
Author(s):  
M. Bižić ◽  
T. Klintzsch ◽  
D. Ionescu ◽  
M. Y. Hindiyeh ◽  
M. Günthel ◽  
...  
Keyword(s):  
Surface Waters ◽  
Primary Productivity ◽  
Methane Production ◽  
Isotope Labeling ◽  
Cyanobacterial Blooms ◽  
Oxygenic Photosynthesis ◽  
Strictly Anaerobic ◽  
Terrestrial Cyanobacteria ◽  
Methane Budget ◽  
Terrestrial Environments

Evidence is accumulating to challenge the paradigm that biogenic methanogenesis, considered a strictly anaerobic process, is exclusive to archaea. We demonstrate that cyanobacteria living in marine, freshwater, and terrestrial environments produce methane at substantial rates under light, dark, oxic, and anoxic conditions, linking methane production with light-driven primary productivity in a globally relevant and ancient group of photoautotrophs. Methane production, attributed to cyanobacteria using stable isotope labeling techniques, was enhanced during oxygenic photosynthesis. We suggest that the formation of methane by cyanobacteria contributes to methane accumulation in oxygen-saturated marine and limnic surface waters. In these environments, frequent cyanobacterial blooms are predicted to further increase because of global warming potentially having a direct positive feedback on climate change. We conclude that this newly identified source contributes to the current natural methane budget and most likely has been producing methane since cyanobacteria first evolved on Earth.

I.B.P. studies on montane grassland and moorlands

1976 ◽  
Vol 274 (934) ◽  
pp. 295-314 ◽  
Keyword(s):  
Primary Productivity ◽  
Environmental Conditions ◽  
Ecosystem Functioning ◽  
Secondary Production ◽  
Dry Matter ◽  
Dwarf Shrub ◽  
South Georgia ◽  
Blanket Bog ◽  
Herbivore Consumption

The aim of the grassland and moorland studies was to measure primary and secondary production and to describe the main pathways of dry matter and nutrients within these ecosystems. The strategy was to make detailed studies on two main sites (Snowdonia and Moor House N.N.R. in the northern Pennines) with a limited number of supporting studies. The examination of the few sites in the U.K. must be seen as part of a series of sites within the International Grassland and Tundra Biomes. They are thus replicates and the series allows examination of trends in productivity related to environmental conditions. The Bi-Polar Botanical Project, with sites in Greenland and South Georgia, supported by the U.K., is part of the international series. The Snowdonia project covered a range of sites but concentrated on a sheep-grazed Agrostis-Festuca sward at 460 m. At Moor House attention focused on blanket bog sites dominated by Calluna, Eriophorum and Sphagnum at about 600 m with supporting studies on dwarf shrub communities ranging from 1100 m in the Cairngorm Mountains to 60 m in Dorset. Comparisons are made of three estimates of primary productivity, of herbivore consumption with production, and decomposer populations with process rates. These results are briefly reviewed in the context of the international range of sites; they allow us to distinguish broad patterns of ecosystem functioning.

Equilibrium analysis of carbon pools and fluxes of forest biomes in the former Soviet Union

1993 ◽  
Vol 23 (1) ◽  
pp. 81-88 ◽  
Author(s):  
Tatyana P. Kolchugina ◽  
Ted S. Vinson
Keyword(s):  
Soviet Union ◽  
Carbon Cycle ◽  
Primary Productivity ◽  
Boreal Forests ◽  
Former Soviet Union ◽  
Net Primary Productivity ◽  
Terrestrial Ecosystems ◽  
Carbon Pool ◽  
Equilibrium Analysis ◽  
Terrestrial Carbon

Natural processes in ocean and terrestrial ecosystems together with human activities have caused a measurable increase in the atmospheric concentration of CO2. It is predicted that an increase in the concentration of CO2 will cause the Earth's temperatures to rise and will accelerate rates of plant respiration and the decay of organic matter, disrupting the equilibrium of the terrestrial carbon cycle. Forests are an important component of the biosphere, and sequestration of carbon in boreal forests may represent one of the few realistic alternatives to ameliorate changes in atmospheric chemistry. The former Soviet Union has the greatest expanse of boreal forests in the world; however, the role of Soviet forests in the terrestrial carbon cycle is not fully understood because the carbon budget of the Soviet forest sector has not been established. In recognition of the need to determine the role of Soviet forests in the global carbon cycle, the carbon budget of forest biomes in the former Soviet Union was assessed based on an equilibrium analysis of carbon cycle pools and fluxes. Net primary productivity was used to identify the rate of carbon turnover in the forest biomes. Net primary productivity was estimated at 4360 Mt of carbon, the vegetation carbon pool was estimated at 110 255 Mt, the litter carbon pool was estimated at 17 525 Mt, and the soil carbon pool was estimated at 319 100 Mt. Net primary productivity of Soviet forest biomes exceeded industrial CO2 emissions in the former Soviet Union by a factor of four and represented approximately 7% of the global terrestrial carbon turnover. Carbon stores in the phytomass and soils of forest biomes of the former Soviet Union represented 16% of the carbon concentrated in the biomass and soils of the world's terrestrial ecosystems. All carbon pools of Soviet forest biomes represented approximately one-seventh of the world's terrestrial carbon pool.

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