A full year of turbulence measurements from a drift campaign in the Arctic Ocean 2019-2020.

Ocean turbulent mixing is a key process in the global climate system, regulating ocean circulation and the uptake and redistribution of heat, carbon, nutrients, oxygen and other tracers. In polar oceans, turbulent heat transport additionally affects the sea ice mass balance. Due to the inaccessibility of polar regions, direct observations of turbulent mixing are sparse in the Arctic Ocean.

Carbon assimilating fungi from surface ocean to subseafloor revealed by coupled phylogenetic and stable isotope analysis.

Fungi are ubiquitous in the ocean and hypothesized to be important members of marine ecosystems, but their roles in the marine carbon cycle are poorly understood. Here, we use C DNA stable isotope probing coupled with phylogenetic analyses to investigate carbon assimilation within diverse communities of planktonic and benthic fungi in the Benguela Upwelling System (Namibia). Across the redox stratified water column and in the underlying sediments, assimilation of C-labeled carbon from diatom extracellular polymeric substances (C-dEPS) by fungi correlated with the expression of fungal genes encoding carbohydrate-active enzymes.

Author Correction: Metabolic activity analyses demonstrate that Lokiarchaeon exhibits homoacetogenesis in sulfidic marine sediments.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Metabolic activity analyses demonstrate that Lokiarchaeon exhibits homoacetogenesis in sulfidic marine sediments.

The genomes of the Asgard superphylum of Archaea hold clues pertaining to the nature of the host cell that acquired the mitochondrion at the origin of eukaryotes. Representatives of the Asgard candidate phylum Candidatus Lokiarchaeota (Lokiarchaeon) have the capacity for acetogenesis and fermentation, but how their metabolic activity responds to environmental conditions is poorly understood. Here, we show that in anoxic Namibian shelf sediments, Lokiarchaeon gene expression levels are higher than those of bacterial phyla and increase with depth below the seafloor.

The tropical-subtropical coupling in the Southeast Atlantic from the perspective of the northern Benguela upwelling system.

In the Benguela upwelling system, the environmental conditions are determined to a large extent by central water masses advected from remote areas onto the shelf. The origin, spreading pathways and fate of those water masses are investigated with a regional ocean model that is analysed using Eulerian passive tracers and on the basis of Lagrangian trajectories. Two major water masses influencing the Benguela upwelling system are identified: tropical South Atlantic Central Water (SACW) and subtropical Eastern South Atlantic Central Water (ESACW).

Stratification, nitrogen fixation, and cyanobacterial bloom stage regulate the planktonic food web structure.

Changes in the complexity of planktonic food webs may be expected in future aquatic systems due to increases in sea surface temperature and an enhanced stratification of the water column. Under these conditions, the growth of unpalatable, filamentous, N -fixing cyanobacterial blooms, and their effect on planktonic food webs will become increasingly important. The planktonic food web structure in aquatic ecosystems at times of filamentous cyanobacterial blooms is currently unresolved, with discordant lines of evidence suggesting that herbivores dominate the mesozooplankton or that mesozooplankton organisms are mainly carnivorous.

The Impact of the Major Baltic Inflow of December 2014 on the Mercury Species Distribution in the Baltic Sea.

The Baltic Sea is a marginal sea characterized by stagnation periods of several years. Oxygen consumption in its deep waters leads to the buildup of sulfide from sulfate reduction. Some of the microorganisms responsible for these processes also transform reactive ionic mercury to neurotoxic methylmercury.

Detoxification of sulphidic African shelf waters by blooming chemolithotrophs.

Coastal waters support approximately 90 per cent of global fisheries and are therefore an important food reserve for our planet. Eutrophication of these waters, due to human activity, leads to severe oxygen depletion and the episodic occurrence of hydrogen sulphide-toxic to multi-cellular life-with disastrous consequences for coastal ecosytems. Here we show that an area of approximately 7,000 km(2) of African shelf, covered by sulphidic water, was detoxified by blooming bacteria that oxidized the biologically harmful sulphide to environmentally harmless colloidal sulphur and sulphate.

Expanding oxygen-minimum zones in the tropical oceans.

Oxygen-poor waters occupy large volumes of the intermediate-depth eastern tropical oceans. Oxygen-poor conditions have far-reaching impacts on ecosystems because important mobile macroorganisms avoid or cannot survive in hypoxic zones. Climate models predict declines in oceanic dissolved oxygen produced by global warming.