Abstract.

"Diazotrophic dinitrogen (N₂) fixation contributes ~76% to “new” nitrogen inputs to the sunlit open ocean, but environmental factors determining N₂ fixation rates are not well constrained. Excess phosphate (phosphate–nitrate/16 > 0) and iron availability control N₂ fixation rates in the eastern tropical North Atlantic (ETNA), but it remains an open question how excess phosphate is generated within or supplied to the phosphate-depleted sunlit layer. [...]"

Source: Geophysical Research Letters
Authors: Arvind Singh et al.
DOI: 10.1002/2017GL074218

Full article

Abstract.

"Under certain conditions, sediment cores from coastal settings subject to hypoxia can yield records of environmental changes over time scales ranging from decades to millennia, sometimes with a resolution of as little as a few years. A variety of biological and geochemical indicators (proxies) derived from such cores have been used to reconstruct the development of eutrophication and hypoxic conditions over time. [...]"

Source: Biogeosciences
Authors: A. J. Gooday et al.
DOI: 10.5194/bg-6-1707-2009

Full article

"After years of talks, the U.N. has taken a major step toward an international treaty to preserve the biodiversity of the high seas to combat climate change, overfishing and plastic pollution.

[...] The move, which ended two weeks of sometimes contentious talks to hash out the major elements of the treaty, could result in far-reaching protections for marine life through the creation of reserves and other actions designed to blunt threats to ocean health from climate change, over-fishing and pollution. The high seas constitute the nearly 60 percent of the ocean beyond any nation’s jurisdiction. They play a crucial role in the global climate, food supply and economy, yet are largely beyond the reach of the law. [...]"

Source: Newsdeeply

Full article 

Abstract.

"Biological nitrogen fixation (BNF) was investigated above and within the oxygen-depleted waters of the oxygen-minimum zone of the Eastern Tropical North Pacific Ocean. BNF rates were estimated using an isotope tracer method that overcame the uncertainty of the conventional bubble method by directly measuring the tracer enrichment during the incubations. Highest rates of BNF (~4 nM day⁻¹) occurred in coastal surface waters and lowest detectable rates (~0.2 nM day⁻¹) were found in the anoxic region of offshore stations. [...]"

Source: The ISME Journal
Authors: Amal Jayakuma et al.
DOI: 10.1038/ismej.2017.97

Full article

Abstract.

"There is currently no consensus on how humans are affecting the marine nitrogen (N) cycle, which limits marine biological production and CO₂ uptake. Anthropogenic changes in ocean warming, deoxygenation, and atmospheric N deposition can all individually affect the marine N cycle and the oceanic production of the greenhouse gas nitrous oxide (N₂O). However, the combined effect of these perturbations on marine N cycling, ocean productivity, and marine N₂O production is poorly understood. Here we use an Earth system model of intermediate complexity to investigate the combined effects of estimated 21st century CO₂ atmospheric forcing and atmospheric N deposition.  [...]"

Source: Global Biogeochemical Cycles
Authors: A. Landolfi, C. Somes, W. Koeve, L. M. Zamora, A. Oschlies
DOI: 10.1002/2017GB005633

Full article

 Mean state, annual cycle, ENSO, and their interactions

Abstract.

"The El Niño/Southern Oscillation (ENSO) is the leading mode of tropical Pacific interannual variability in the present-day climate. Available proxy evidence suggests that ENSO also existed during past climates, for example during the Pliocene extending from about 5.3 million to about 2.6 million years BP. Here we investigate the influences of the Panama Seaway closing and Indonesian Passages narrowing, and also of atmospheric carbon dioxide (CO₂) on the tropical Pacific mean climate and annual cycle, and their combined impact on ENSO during the Pliocene. [...]"

Source: Climate Dynamics
Authors: Zhaoyang Song, Mojib Latif, Wonsun Park, Uta Krebs-Kanzow, Birgit Schneider
DOI: 10.1007/s00382-016-3298-x

Full article

Abstract.

"Despite of the major role ascribed to marine dissolved organic matter (DOM) in the global carbon cycle, the reactivity of this pool in the dark ocean is still poorly understood. Present hypotheses, posed within the size-reactivity continuum (SRC) and the microbial carbon pump (MCP) conceptual frameworks, need further empirical support. Here, we provide field evidence of the soundness of the SRC model. We sampled the high salinity core-of-flow of the Levantine Intermediate Water along its westward route through the entire Mediterranean Sea. At selected sites, DOM was size-fractionated in apparent high (aHMW) and low (aLMW) molecular weight fractions using an efficient ultrafiltration cell. [...]"

Source: Scientific Reports
Authors: Alba María Martínez-Pérez, Xosé Antón Álvarez-Salgado, Javier Arístegui & Mar Nieto-Cid
DOI: 10.1038/s41598-017-05941-6

Full article

Abstract.

"Oxygen availability drives changes in microbial diversity and biogeochemical cycling between the aerobic surface layer and the anaerobic core in nitrite-rich anoxic marine zones (AMZs), which constitute huge oxygen-depleted regions in the tropical oceans. The current paradigm is that primary production and nitrification within the oxic surface layer fuel anaerobic processes in the anoxic core of AMZs, where 30–50% of global marine nitrogen loss takes place. Here we demonstrate that oxygenic photosynthesis in the secondary chlorophyll maximum (SCM) releases significant amounts of O₂ to the otherwise anoxic environment. [...] "

Source: Proceedings of the National Academy of Sciences of the United States of America (PNAS)
Authors: Emilio Garcia-Robledo et al.
DOI: 10.1073/pnas.1619844114

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Summary:

Using a combination of fossils and chemical markers, scientists have tracked how a period of globally low ocean-oxygen turned an Early Jurassic marine ecosystem into a stressed community inhabited by only a few species.

Source: Science Daily

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The Zoological Department of Oxford University has reviewed and synthesised major marine science findings which have been published since Rio+20 in 2012.

The purpose of this synthesis is to determine how our understanding of the ocean at an Earth System level, with a particular focus on the role of the high seas, has changed in the last five years.

Summary:

"During the last five years scientists have utilised novel technologies and methods to explore new locations and investigate both the fundamental processes of the ocean and the mounting anthropogenic impacts on the marine environment. Studies have highlighted the important functions that the high seas perform for the planet and have often focused on the complexity and interconnected nature of these processes."

Full report

"As delegates convene at the United Nations to work out an international treaty to preserve the biodiversity of the high seas, a new report underscores the need to protect the remote ocean.

Scientists at Oxford University in the United Kingdom reviewed 271 research papers published between 2012 and 2017 and synthesized the latest data on the impact of climate change, fishing and pollution on the high seas. Their findings are not encouraging: Even the most distant reaches of the ocean are suffering from chemical and plastic contamination, a loss of biodiversity and the consequences of rising temperatures. [...]"

Source: UPI

Full article

Abstract.

"Nitrogen (N) is the major limiting nutrient for phytoplankton growth and productivity in large parts of the world's oceans. Differential preferences for specific N substrates may be important in controlling phytoplankton community composition. To date, there is limited information on how specific N substrates influence the composition of naturally occurring microbial communities. We investigated the effect of nitrate ( ), ammonium ( ), and urea on microbial and phytoplankton community composition (cell abundances and 16S rRNA gene profiling) and functioning (photosynthetic activity, carbon fixation rates) in the oligotrophic waters of the North Pacific Ocean. [...]"

Source: Limonology and Oceanography
Authors: I.N. Shilova et al.
DOI: 10.1002/lno.10590

Full article

The Kelp Forest Array (KFA) is a state-of-the-art cabled platform for observational and experimental science aimed at monitoring and understanding local impacts of global climate change. Increasing climate change and ocean acidification pressures require the establishment of long-term, baseline monitoring methods to document how a currently healthy system changes and to understand effects of climate change in relation to this natural variability. Current monitoring practices limit resolution and longevity of baseline data sets.

Full article

Abstract.

"Chemical weathering consumes atmospheric carbon dioxide through the breakdown of silicate minerals and is thought to stabilize Earth’s long-term climate. However, the potential influence of silicate weathering on atmospheric pCO₂ levels on geologically short timescales (10³–10⁵ years) remains poorly constrained. Here we focus on the record of a transient interval of severe climatic warming across the Toarcian Oceanic Anoxic Event or T-OAE from an open ocean sedimentary succession from western North America. [...]"

Source: Scientific Reports
Authors: Theodore R. Them et al.
DOI: 10.1038/s41598-017-05307-y

Full article

Abstract.

"Repeat shipboard and multi-year moored observations obtained in the oxygen minimum zone (OMZ) of the eastern tropical North Atlantic (ETNA) were used to study the decadal change in oxygen for the period 2006–2015. Along 23° W between 6 and 14° N, oxygen decreased with a rate of −5.9 ± 3.5 µmol kg−1 decade−1 within the depth covering the deep oxycline (200–400 m), while below the OMZ core (400–1000 m) oxygen increased by 4.0 ± 1.6 µmol kg−1 decade−1 on average. The inclusion of these decadal oxygen trends in the recently estimated oxygen budget for the ETNA OMZ suggests a weakened ventilation of the upper 400 m, whereas the ventilation strengthened homogeneously below 400 m. [...]"

Source: Ocean Science
Authors: Johannes Hahn, Peter Brandt, Sunke Schmidtko and Gerd Krahmann
DOI: 10.5194/os-13-551-2017

Full article

Abstract.

"Nitrous oxide (N₂O) is a climate relevant trace gas, and its production in the ocean generally increases under suboxic conditions. The Atlantic Ocean is well ventilated, and unlike the major oxygen minimum zones (OMZ) of the Pacific and Indian Oceans, dissolved oxygen and N₂O concentrations in the Atlantic OMZ are relatively high and low, respectively. [...]"

Source: Scientific Reports
Authors: D. S. Grundle et al.
DOI: 10.1038/s41598-017-04745-y

Full article

Abstract.

"Little is known about the foraging behavior of top predators in the deep mesopelagic ocean. Elephant seals dive to the deep biota-poor oxygen minimum zone (OMZ) (>800 m depth) despite high diving costs in terms of energy and time, but how they successfully forage in the OMZ remains largely unknown. Assessment of their feeding rate is the key to understanding their foraging behavior, but this has been challenging. Here, we assessed the feeding rate of 14 female northern elephant seals determined by jaw motion events (JME) and dive cycle time to examine how feeding rates varied with dive depth, particularly in the OMZ. [...]"

Source: Ecology and Evolution
Authors: Yasuhiko Naito et al.
DOI: 10.1002/ece3.3202

Full article