Biogeochemical Controls on the Redox Evolution of Earth`s Oceans and Atmosphere
"The redox state of Earth’s atmosphere has undergone a dramatic shift over geologic time from reducing to strongly oxidizing, and this shift has been coupled with changes in ocean redox structure and the size and activity of Earth’s biosphere. Delineating this evolutionary trajectory remains a major problem in Earth system science. Significant insights have emerged through the application of redox-sensitive geochemical systems. Existing and emerging biogeochemical modeling tools are pushing the limits of the quantitative constraints on ocean–atmosphere[...]"
Authors: Christopher T. Reinhard et al.
Rapid transfer of oxygen to the deep ocean mediated by bubbles
"The concentration of oxygen exerts major controls on life in the ocean, and its distribution in the ocean and atmosphere carries information about biological productivity, transports of mass and heat, ocean deoxygenation and global carbon sinks. Our understanding of processes underlying oxygen distributions, their key features and variability is often lacking. Here we investigate the magnitude, variability and uncertainty of the air–sea flux of oxygen, carbon dioxide and atmospheric potential oxygen over an annual cycle in the Labrador Sea. We demonstrate that two-thirds of the annual oxygen uptake occurs over only 40 days in winter and is associated with a bubble-mediated component[...]"
Source: Nature Geoscience
Authors: D. Atamanchuk et al.
Benthic fluxes of oxygen and heat from a seasonally hypoxic region of Saanich Inlet fjord observed by eddy covariance
"Benthic habitats within fjords are predominantly insulated from the high energy physical dynamics of open coastlines. As a result, fjords may have atypical mass and heat transfer rates at the seafloor. This study presents aquatic eddy covariance (EC) measurements made continuously from late May 2013 through December 2013, in Saanich Inlet fjord, British Columbia, to assess areal-averaged benthic fluxes of dissolved oxygen and heat, and their relationships to bottom boundary layer dynamics and water properties. The measurements were achieved by the connection of a system of underwater EC sensors to Ocean Network Canada's Victoria Experimental Network Under the Sea (VENUS) observatory that has a primary seafloor node[...]"
Source: Science Direct
Authors: Clare E. Reimers et al.
Factors controlling plankton community production, export flux, and particulate matter stoichiometry in the coastal upwelling system off Peru
"Eastern boundary upwelling systems (EBUS) are among the most productive marine ecosystems on Earth. The production of organic material is fueled by upwelling of nutrient-rich deep waters and high incident light at the sea surface. However, biotic and abiotic factors can modify surface production and related biogeochemical processes. Determining these factors is important because EBUS are considered hotspots of climate change, and reliable predictions of their future functioning requires understanding of the mechanisms driving the biogeochemical cycles therein. In this field experiment, we used in situ mesocosms as tools to improve our mechanistic understanding of processes controlling organic matter cycling in the coastal Peruvian upwelling system.[...]"
Authors: Lennart Thomas Bach et al.
Recovery from multi-millennial natural costal hypoxia in the Stockholm Archipelago, Baltic Sea, terminated by modern human activity
"Enhanced nutrient input and warming have led to the development of low oxygen (hypoxia) in coastal waters globally. For many coastal areas, insight into redox conditions prior to human impact is lacking. Here, we reconstructed bottom water redox conditions and sea surface temperatures (SSTs) for the coastal Stockholm Archipelago over the past 3000 yr. Elevated sedimentary concentrations of molybdenum indicate (seasonal) hypoxia between 1000 b.c.e. and 1500 c.e. Biomarker[...]"
Source: Association for the Sciences of Limnology and Oceanography
Authors: Niels A. G. M. van Helmond et al.
Potential effects of deep seabed mining on pelagic and benthopelagic biota
"Environmental concerns were raised from the very onset of discussions concerning the extraction of metalliferous ores from the deep sea, but most studies have targeted the expected impacts on the benthic communities only. The first section of this study compiles possible impacts of deep seabed mining activities on pelagic organisms. Several processes of mining-related activities were identified that can potentially affect the pelagic environment. Some of these processes will assumedly have only minor effects on the pelagic and benthopelagic communities, for example substrate removal and deposition of material.[...]"
Source: Science Direct
Authors: Bernd Christiansen et al.
Benthic fluxes of oxygen and nutrients under the influence of macrobenthic fauna on the periphery of the intermittently hypoxic zone in the Baltic Sea
"Understanding the role of benthic organisms in marine sediments is becoming increasingly important with the growing problem of eutrophication of marine ecosystems around the world, including the Baltic Sea. Therefore, we have conducted a series of incubation experiments on sediment cores collected from sites characterized by varying oxygen conditions and measured the influx (uptake by sediment) of oxygen as well as the sediment–water exchange of phosphate, ammonia and silicate.[...]"
Source: Science Direct
Authors: Halina Kendzierska et al.
Biogeochemistry and hydrography shape microbial community assembly and activity in the eastern topical North Pacific Ocean oxygen minimum zone
"Oceanic oxygen minimum zones (OMZs) play a pivotal role in biogeochemical cycles due to extensive microbial activity. How OMZ microbial communities assemble and respond to environmental variation is therefore essential to understanding OMZ functioning and ocean biogeochemistry. Sampling along depth profiles at five stations in the eastern tropical North Pacific Ocean (ETNP), we captured systematic variations in dissolved oxygen (DO) and associated variables (nitrite, chlorophyll, and ammonium) with depth and between stations. We quantitatively analysed relationships between oceanographic gradients and microbial community assembly and activity based on paired 16S rDNA and 16S rRNA sequencing. Overall microbial community[...] "
Source: Society for Applied Microbiology
Authors: J. Michael Berman et al.
Impacts of climate change on dissolved oxygen concentration relevant to the costal and marine environment around the UK
"The decline in dissolved oxygen and onset of oxygen deficiency and hypoxia are naturally occurring phenomenon in aquatic environments, typically occurring on seasonal timescales. Over decadal timescales, there has been a measurable decline in dissolved oxygen concentrations in the global ocean due to warming caused by anthropogenic activity. Approximately 15% of the global decline in oxygen has been attributed to reduced solubility in response to ocean warming, with the remaining 85% due to intensified stratification. The relative contribution of these factors in coastal and shelf-sea waters is currently unknown. In UK waters, sustained observations in the North[...]"
Source: MCCIP Science Review
Authors: Mahaffey, C et al.
The Impacts of Ocean Acidification on Marine Ecosystems and Reliant Human Communities
"Rising atmospheric carbon dioxide (CO2) levels, from fossil fuel combustion and deforestation, along with agriculture and land-use practices are causing wholesale increases in seawater CO2 and inorganic carbon levels; reductions in pH; and alterations in acid-base chemistry of estuarine, coastal, and surface open-ocean waters. On the basis of laboratory experiments and field studies of naturally elevated CO2 marine environments, widespread biological impacts of human-driven ocean acidification have been posited, ranging from changes in organism physiology and population dynamics to altered communities and ecosystems. Acidification, in conjunction with other climate change–related environmental stresses, particularly under future climate change[...]"
Source: Annual Review of Environment and Resources
Authors: Scott C. Doney et al.