In situ observations show vertical community structure of pelagic fauna in the eastern tropical North Atlantic off Cape Verde
"Distribution patterns of fragile gelatinous fauna in the open ocean remain scarcely documented. Using epi-and mesopelagic video transects in the eastern tropical North Atlantic, which features a mild but intensifying midwater oxygen minimum zone (OMZ), we established one of the first regional observations of diversity and abundance of large gelatinous zooplankton. We quantified the day and night vertical distribution of 46 taxa in relation to environmental conditions. While distribution may be driven by multiple factors, abundance peaks of individual taxa were observed in the OMZ[...]"
Source: Nature Scientific Reports
Authors: H. J. T. Hoving et al.
Planktonic food web structure and trophic transfer efficiency along a productivity gradient in the tropical and subtropical Atlantic Ocean
"Oligotrophic and productive areas of the ocean differ in plankton community composition and biomass transfer efficiency. Here, we describe the plankton community along a latitudinal transect in the tropical and subtropical Atlantic Ocean. Prochlorococcus dominated the autotrophic community at the surface and mixed layer of oligotrophic stations, replaced by phototrophic picoeukaryotes and Synechococcus in productive waters. [...]"
Source: Scientific Reports
Authors: Laia Armengol et al.
Characterization of “dead-zone” eddies in the eastern tropical North Atlantic (2016)
"Localized open-ocean low-oxygen “dead zones” in the eastern tropical North Atlantic are recently discovered ocean features that can develop in dynamically isolated water masses within cyclonic eddies (CE) and anticyclonic mode-water eddies (ACME). Analysis of a comprehensive oxygen dataset obtained from gliders, moorings, research vessels and Argo floats reveals that “dead-zone” eddies are found in surprisingly high numbers and in a large area from about 4 to 22°N, from the shelf at the eastern boundary to 38°W. [...]"
Authors: Florian Schütte et al.
Subsurface Fine‐Scale Patterns in an Anticyclonic Eddy Off Cap‐Vert Peninsula Observed From Glider Measurements
"Glider measurements acquired along four transects between Cap‐Vert Peninsula and the Cape Verde archipelago in the eastern tropical North Atlantic during March–April 2014 were used to investigate fine‐scale stirring in an anticyclonic eddy. The anticyclone was formed near 12°N off the continental shelf and propagated northwest toward the Cape Verde islands. At depth, between 100 and –400 m, the isolated anticyclone core contained relatively oxygenated, low‐salinity South Atlantic Central Water, while the surrounding water masses were saltier and poorly oxygenated. [...]"
Authors: Nicolas Kolodziejczyk et al.
Niche construction by non-diazotrophs for N2 fixers in the eastern tropical North Atlantic Ocean
"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.
Decadal oxygen change in the eastern tropical North Atlantic
"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