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Impacts of hypoxic events surpass those of future ocean warming and acidification

Abstract.

"Over the past decades, three major challenges to marine life have emerged as a consequence of anthropogenic emissions: ocean warming, acidification and oxygen loss. While most experimental research has targeted the first two stressors, the last remains comparatively neglected. Here, we implemented sequential hierarchical mixed-model meta-analyses (721 control–treatment comparisons) to compare the impacts of oxygen conditions associated with the current and continuously intensifying hypoxic[...]"

 

Source: Nature Ecology and Evolution
Authors: Eduardo Sampaio et al.
DOI: https://doi.org/10.1038/s41559-020-01370-3

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Methane oxidation in the waters of a humics-rich boreal lake stimulated by photosynthesis, nitrite, Fe(III) and humics

Abstract.

"Small boreal lakes are known to contribute significantly to global methane emissions. Lake Lovojärvi is a eutrophic lake in Southern Finland with bottom water methane concentrations up to 2 mM. However, the surface water concentration, and thus the diffusive emission potential, was low (< 0.5 μM). We studied the biogeochemical processes involved in methane removal by chemical profiling and through incubation experiments. δ13C-CH4 profiling of the water column revealed methane-oxidation hotspots just below the oxycline and within the anoxic water column. In incubation experiments involving the addition of light and/or oxygen, methane oxidation rates in the anoxic hypolimnion were enhanced 3-fold, suggesting a major role for photosynthetically fueled aerobic methane oxidation. A distinct peak in methane concentration was observed at the chlorophyll a maximum[...]"

Source: Biogeoscience
Authors: Sigrid van Grinsven et al.
DOI: https://doi.org/10.5194/bg-2021-3

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Around one third of current Arctic Ocean primary production sustained by rivers and coastal erosion

Abstract.
 

"Net primary production (NPP) is the foundation of the oceans’ ecosystems and the fisheries they support. In the Arctic Ocean, NPP is controlled by a complex interplay of light and nutrients supplied by upwelling as well as lateral inflows from adjacent oceans and land. But so far, the role of the input from land by rivers and coastal erosion has not been given much attention. Here, by upscaling observations from the six largest rivers and using measured coastal erosion rates, we construct a pan-Arctic[...]"

Source: Nature Communications
Authors: Jens Terhaar et al.
DOI: https://doi.org/10.1038/s41467-020-20470-z

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The rise of angiosperms strengthened fire feedbacks and improved the regulation of atmospheric oxygen

Abstract.

"The source of oxygen to Earth’s atmosphere is organic carbon burial, whilst the main sink is oxidative weathering of fossil carbon. However, this sink is to insensitive to counteract oxygen rising above its current level of about 21%. Biogeochemical models suggest that wildfires provide an additional regulatory feedback mechanism. However, none have considered how the evolution of different plant groups through time have interacted with this feedback. The Cretaceous Period[...]"

 

Source: Nature Geoscience
Authors: Claire M. Belcher et al.
DOI: https://doi.org/10.1038/s41467-020-20772-2

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Status and trends of Arctic Ocean environmental change and its impacts on marine biogeochemistry: Findings from the ArCS project

Abstract.

"Ocean observation research theme under ArCS project, “Theme 4: Observational research on Arctic Ocean environmental changes”, aimed to elucidate the status and trends of ongoing Arctic Ocean environmental changes and to evaluate their impacts on Arctic marine ecosystem and the global climate system. For these purposes, we conducted field observations, mooring observations, laboratory experiments, numerical modeling, and international collaborative research focusing on the Pacific Arctic[...]"

 

Source: Science Direct
Authors: Takashi Kikuchi et al.
DOI: https://doi.org/10.1016/j.polar.2021.100639

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Assimilating synthetic Biogeochemical-Argo and ocean colour observations into a global ocean model to inform observing system design

Abstract.

"A set of observing system simulation experiments was performed. This assessed the impact on global ocean biogeochemical reanalyses of assimilating chlorophyll from remotely sensed ocean colour and in situ observations of chlorophyll, nitrate, oxygen, and pH from a proposed array of Biogeochemical-Argo (BGC-Argo) floats. Two potential BGC-Argo array distributions were tested: one for which biogeochemical sensors are placed on all current Argo floats and one for which biogeochemical sensors are placed on a quarter of current Argo floats. Assimilating BGC-Argo data greatly improved model results throughout the water column[...]"

 

Source: Biogeosciences
Authors: David Ford et al.
DOI: https://doi.org/10.5194/bg-18-509-2021

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A Lagrangian study of the contribution of the Canary coastal upwelling to the nitrogen budget of the open North Atlantic

Abstract.

"The Canary Current System (CanCS) is a major eastern boundary upwelling system (EBUS), known for its high nearshore productivity and for sustaining a large fishery. It is also an important but not well quantified source of nitrogen to the adjacent oligotrophic subtropical gyre of the North Atlantic. Here, we use a Lagrangian modeling approach to quantify this offshore transport and investigate its timescales, reach and contribution to the fueling of productivity in the offshore regions. In our Lagrangian model, we release nearly 10 million particles off the northwestern African coast and then track all those that enter the nearshore region and upwell along the coast between 14 and 35∘ N. We then follow them as they are transported offshore, also tracking the biogeochemical[...]"

 

Source: Biogeosciences
Authors: Derara Hailegeorgis et al.
DOI: https://doi.org/10.5194/bg-18-303-2021

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The role of environmental factors in the long-term evolution of the marine biological pump

Absract.

"The biological pump—the transfer of atmospheric carbon dioxide to the ocean interior and marine sediments as organic carbon—plays a critical role in regulating the long-term carbon cycle, atmospheric composition and climate. Despite its centrality in the Earth system, the response of the biological pump to biotic innovation and climatic fluctuations through most stages of Earth’s history has been largely conjectural. Here we use a mechanistic model of the biological carbon pump to revisit the factors controlling[...]"

 

Source: Nature Geoscience
Authors: Mojtaba Fakhraee et al.
DOI: https://doi.org/10.1038/s41561-020-00660-6

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Glacial deep ocean deoxygenation driven by biologically mediated air–sea disequilibrium

Abstract.

"Deep ocean deoxygenation inferred from proxies has been used to support the hypothesis that a lower atmospheric carbon dioxide during glacial times was due to an increase in the strength of the ocean’s biological pump. This relies on the assumption that surface ocean oxygen (O2) is equilibrated with the atmosphere such that any O2 deficiency observed in deep waters is a result of organic matter respiration, which consumes O2 and produces dissolved inorganic carbon. However, this assumption has been shown to be imperfect because of disequilibrium. Here we used an Earth system[...]"

 

Source: Nature Geoscience 
Authors: Ellen Cliff et al.
DOI: https://doi.org/10.1038/s41561-020-00667-z

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Increased carbon capture by a silicate-treated forested watershed affected by acid deposition

Abstract.

"Meeting internationally agreed-upon climate targets requires carbon dioxide removal (CDR) strategies coupled with an urgent phase-down of fossil fuel emissions. However, the efficacy and wider impacts of CDR are poorly understood. Enhanced rock weathering (ERW) is a land-based CDR strategy requiring large-scale field trials. Here we show that a low 3.44 t ha−1 wollastonite treatment in an 11.8 ha acid-rain-impacted forested watershed in New Hampshire, USA, led to cumulative carbon capture by carbonic acid weathering of 0.025–0.13 t CO2 ha−1 over 15 years. Despite a 0.8–2.4 t CO2 ha−1 logistical carbon penalty from mining, grinding, transportation[...]"

 

Source: Biogeosciences
Authors: Lyla L. Taylor et al.
DOI: https://doi.org/10.5194/bg-18-169-2021

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