scholarly journals N2 Fixation by Unicellular Bacterioplankton from the Atlantic and Pacific Oceans: Phylogeny and In Situ Rates

2004 ◽  
Vol 70 (2) ◽  
pp. 765-770 ◽  
Author(s):  
Luisa I. Falcón ◽  
Edward J. Carpenter ◽  
Frank Cipriano ◽  
Birgitta Bergman ◽  
Douglas G. Capone
Keyword(s):  
North Atlantic ◽  
Surface Waters ◽  
North Pacific ◽  
Marine Cyanobacteria ◽  
Common Ancestry ◽  
Near Surface ◽  
16S Ribosomal Dna ◽  
Tropical North Atlantic ◽  
Night And Day

ABSTRACT N2-fixing proteobacteria (α and γ) and unicellular cyanobacteria are common in both the tropical North Atlantic and Pacific oceans. In near-surface waters proteobacterial nifH transcripts were present during both night and day while unicellular cyanobacterial nifH transcripts were present during the nighttime only, suggesting separation of N2 fixation and photosynthesis by unicellular cyanobacteria. Phylogenetic relationships among unicellular cyanobacteria from both oceans were determined after sequencing of a conserved region of 16S ribosomal DNA (rDNA) of cyanobacteria, and results showed that they clustered together, regardless of the ocean of origin. However, sequencing of nifH transcripts of unicellular cyanobacteria from both oceans showed that they clustered separately. This suggests that unicellular cyanobacteria from the tropical North Atlantic and subtropical North Pacific share a common ancestry (16S rDNA) and that potential unicellular N2 fixers have diverged (nifH). N2 fixation rates for unicellular bacterioplankton (including small cyanobacteria) from both oceans were determined in situ according to the acetylene reduction and 15N2 protocols. The results showed that rates of fixation by bacterioplankton can be almost as high as those of fixation by the colonial N2-fixing marine cyanobacteria Trichodesmium spp. in the tropical North Atlantic but that rates are much lower in the subtropical North Pacific.

scholarly journals Diversity of Diazotrophic Unicellular Cyanobacteria in the Tropical North Atlantic Ocean

2002 ◽  
Vol 68 (11) ◽  
pp. 5760-5764 ◽  
Author(s):  
Luisa I. Falcón ◽  
Frank Cipriano ◽  
Andrei Y. Chistoserdov ◽  
Edward J. Carpenter
Keyword(s):  
Genetic Diversity ◽  
Atlantic Ocean ◽  
Ribosomal Dna ◽  
North Atlantic ◽  
Dna Sequences ◽  
North Pacific ◽  
North Atlantic Ocean ◽  
16S Ribosomal Dna ◽  
Tropical North Atlantic ◽  
Phylogenetic Affinities

ABSTRACT We present data on the genetic diversity and phylogenetic affinities of N2-fixing unicellular cyanobacteria in the plankton of the tropical North Atlantic Ocean. Our dinitrogenase gene (nifH) sequences grouped together with a group of cyanobacteria from the subtropical North Pacific; another subtropical North Pacific group was only distantly related. Most of the 16S ribosomal DNA sequences from our tropical North Atlantic samples were closely allied with sequences from a symbiont of the diatom Climacodium frauenfeldianum. These findings suggest a complex pattern of evolutionary and ecological divergence among unicellular cyanobacteria within and between ocean basins.

Using a novel combination of autonomous vehicles for air-sea interaction studies: Results from the Eurec4a campaign 

2021 ◽  
Author(s):  
Elizabeth Siddle ◽  
Karen J. Heywood ◽  
Ben Webber ◽  
Peter Bromley
Keyword(s):  
Time Series ◽  
North Atlantic ◽  
Heat Budget ◽  
Heat Content ◽  
Flux Measurement ◽  
Extreme Weather Events ◽  
Upper Ocean ◽  
Momentum Exchange ◽  
Tropical North Atlantic

<div> <p>The Tropical North Atlantic region is a key driver of climate variability and extreme weather events, driven largely by heat and momentum exchanges across the air-sea boundary. Observations of these fluxes by satellites and vessels are limited in their spatial resolution and length of time series respectively. In-situ samples across long time periods are needed, which can be obtained through developing a network of in-situ flux measurement platforms. UEA and AutoNaut have worked to address this challenge with the deployment of <em>Caravela</em> - an AutoNaut uncrewed surface vessel. <em>Caravela</em> is a wave and solar powered autonomous vessel, equipped with meteorological and oceanographic sensors and the ability to transport a Seaglider. <em>Caravela</em> successfully completed its first scientific deployment as part of the Eurec<sup>4</sup>a campaign. </p> </div><div> <p>Eurec<sup>4</sup>a ran from January—March 2020 from Barbados, investigating climate change feedback in the Tropical North Atlantic and the role of cloud systems. <em>Caravela</em> spent 11 days of her 33-day deployment occupying a 10 km square, co-located with other Eurec<sup>4</sup>a platforms to gather in-situ surface data on heat and momentum exchange. Preliminary results from <em>Caravela</em> give us an insight into heat exchange at the surface, downwelling radiation and wind conditions during deployment. There is an identifiable diurnal cycle during the deployment, particularly visible in temperature data, which will feed into our understanding of changes in fluxes at a local scale. Profiling ocean gliders at the study site allow us to determine a time series of upper ocean heat content changes. These data, alongside that collected by other platforms during Eurec<sup>4</sup>a, should enable an upper ocean heat budget to be calculated at <em>Caravela’s</em> study site. </p> </div>

scholarly journals The pliocene record of climatic change: equator-to-pole biotic response

1992 ◽  
Vol 6 ◽  
pp. 78-78
Author(s):  
Thomas M. Cronin ◽  
H.J. Dowsett
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
North Pacific ◽  
Global Climate ◽  
North Pacific Ocean ◽  
Thermal Gradients ◽  
High Latitudes ◽  
Near Surface ◽  
Temperature Changes ◽  
The North

Pliocene faunal events in tropical and subtropical regions of the Americas and the Caribbean have been causally linked to global climatic events, particularly, progressive cooling and increased amplitude of climatic cycles between 3.5 and 2.0 Ma. However, the rate and magnitude of Pliocene temperature changes has been determined in only a few climate proxy records. Our study contrasts paleoceanographic conditions at 3 Ma, an extremely warm period in many areas, with conditions 2.4 Ma, a much cooler interval, in equator-to-pole transects for the North Atlantic and the North Pacific Oceans. By using microfaunal data (ostracodes from ocean margin environments and planktic foraminifers from deep sea cores), quantitative factor analytic and modern analog dissimilarity coefficient analyses were carried out on faunas from the following sections.Our studies lead to the following conclusions: (1) Equator-to-pole thermal gradients in the oceans at 3.0 Ma were not as steep as they are today, but thermal gradients at 2.4 Ma were steeper than those today; (2)At 3 Ma middle to high latitudes were substantially warmer than today, but tropical regions were about the same; (3)Substantial cooling occurred in middle and high latitudes in the western North Pacific Ocean and the western North Atlantic between 3 Ma and 2.4 Ma; (4)Ocean water temperatures off the southeastern U.S. remained the same or cooled only slightly between 3 Ma and 2.4 Ma. Our results support the hypothesis that ocean circulation changes, probably resulting from the closure of near surface water by the Isthmus of Panama, had significant impact on equator-to-pole heat transport and global climate between about 3 and 2.4 Ma. They also argue against the hypothesis that climatically induced ocean temperature changes were directly linked to a major marine extinction in the southwestern North Atlantic and Caribbean.

Oxygen variability in the near-surface waters of the northern North Atlantic: Observations and a model

2004 ◽  
Vol 62 (5) ◽  
pp. 663-683 ◽  
Author(s):  
Peter Lazarevich ◽  
Tom Rossby ◽  
Craig Mcneil
Keyword(s):  
North Atlantic ◽  
Surface Waters ◽  
Near Surface

scholarly journals From In Situ to satellite observations of pelagic Sargassum distribution and aggregation in the Tropical North Atlantic Ocean

PLoS ONE ◽  
2019 ◽  
Vol 14 (9) ◽  
pp. e0222584 ◽  
Author(s):  
Anouck Ody ◽  
Thierry Thibaut ◽  
Léo Berline ◽  
Thomas Changeux ◽  
Jean-Michel André ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Satellite Observations ◽  
Tropical North Atlantic

scholarly journals Assessment of a global climatology of oceanic dimethylsulfide (DMS) concentrations based on SeaWiFS imagery (1998-2001)

2004 ◽  
Vol 61 (5) ◽  
pp. 804-816 ◽  
Author(s):  
S Belviso ◽  
C Moulin ◽  
L Bopp ◽  
J Stefels
Keyword(s):  
North Atlantic ◽  
Surface Waters ◽  
Sea Surface ◽  
Wide Field ◽  
Chl A ◽  
The North ◽  
Wide Field Of View ◽  
Lyase Activity ◽  
Mixed Populations

A method is developed to estimate sea-surface particulate dimethylsulfoniopropionate (DMSPp) and dimethylsulfide (DMS) concentrations from sea-surface concentrations of chlorophyll a (Chl a). When compared with previous studies, the 1° × 1° global climatology of oceanic DMS concentrations computed from 4 years (1998–2001) of Chl a measurements derived from SeaWiFS (satellite-based, sea-viewing wide field of view sensor) exhibits lower seasonal variability in the southern hemisphere than in the northern hemisphere. A first evaluation of the method shows that it reasonably well represents DMSPp and DMS in the North Atlantic subtropical gyre, in large blooms of mixed populations of diatoms and Phaeocystis spp., and in massive blooms of Phaeocystis spp. but fails for large, almost pure blooms of diatoms. DMSPp and DMS concentrations derived from SeaWiFS were also compared with spatially and temporally coincident in situ measurements acquired independently in the Atlantic between 39°N and 45°N and in subtropical and subantarctic Indian Ocean surface waters. Moderate spring and summer phytoplankton blooms there exhibited similar trends in DMSPp and DMS levels vs. moderate blooms of mixed populations of prymnesiophytes and dinoflagellates investigated by others. Measured DMS largely exceeded simulated DMS concentrations, whereas measured and simulated DMSPp levels were in close agreement. DMS accumulation is tentatively attributed to dinoflagellate DMSP lyase activity.

scholarly journals Oxygen Utilization and Downward Carbon Flux in an Oxygen-Depleted Eddy in the Eastern Tropical North Atlantic

2016 ◽  
Author(s):  
B. Fiedler ◽  
D. Grundle ◽  
F. Schütte ◽  
J. Karstensen ◽  
C. R. Löscher ◽  
...  
Keyword(s):  
Organic Matter ◽  
North Atlantic ◽  
Lower Boundary ◽  
Euphotic Zone ◽  
Shallow Depth ◽  
Surface Mixed Layer ◽  
Low Oxygen ◽  
Oxygen Utilization ◽  
Near Surface ◽  
Tropical North Atlantic

Abstract. The occurrence of mesoscale eddies that develop an extreme low oxygen environment at shallow depth (about 40 to 100 m) has recently been reported for the eastern tropical North Atlantic (ETNA). Their hydrographic structure suggests that the water mass inside the eddy is well isolated from ambient waters supporting the development of severe near-surface oxygen deficits. So far, hydrographic and biogeochemical characterization of these eddies was limited to a few autonomous surveys, using moorings, underwater gliders and profiling floats. In this study we present results from the first dedicated biogeochemical survey of one of these eddies conducted in March 2014 near the Cape Verde Ocean Observatory (CVOO). At the time of the survey the eddy core showed lowest oxygen concentrations of less than 5 μmol kg−1 and a pH of approx. 7.6 at the lower boundary of the euphotic zone. Correspondingly, the aragonite saturation level dropped to 1 thereby creating unfavorable conditions for calcifying organisms at this shallow depth. To our knowledge, such enhanced acidity within near-surface waters has never been reported before for the open Atlantic Ocean. Vertical distributions of particulate and dissolved organic matter (POM, DOM) generally show elevated concentrations in the surface mixed layer, but particularly DOM also accumulates beneath the oxygen minimum. Considering reference data from the upwelling region where these eddies are formed, we determined the oxygen consumption through remineralization of organic matter and found an enhancement of apparent oxygen utilization rates (aOUR, 0.26 μmol kg−1 d−1) by almost one order of magnitude when compared with typical values for the open North Atlantic. Computed downward fluxes for particulate organic carbon (POC) at 100 m were about 0.19 to 0.23 g C m−2 d−1 which clearly exceed fluxes typical for an oligotrophic open ocean setting. The observations support the view that the oxygen depleted eddies can be viewed as isolated, westwards propagating upwelling systems as their own.

summertime stationary waves integrate tropical and extratropical impacts on tropical cyclone activity 

2021 ◽  
Author(s):  
Zhuo Wang ◽  
Gan Zhang ◽  
Timothy Dunkerton ◽  
Fei-Fei Jin
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Large Scale ◽  
Seasonal Prediction ◽  
Significant Loss ◽  
Stationary Waves ◽  
Atmospheric Conditions ◽  
Rossby Wave Breaking ◽  
The North ◽  
Tropical North Atlantic

<div> <div> <div> <div> <p>Tropical cyclones (TC) are one of the most severe storm systems on Earth and cause significant loss of life and property upon landfall in coastal areas. A better understanding of their variability mech- anisms will help improve the TC seasonal prediction skill and mitigate the destructive impacts of the storms. Early studies focused primarily on tropical processes in regulating the variability of TC activity, while recent studies suggest also some long-range impacts of extratropical processes, such as lateral transport of dry air and potential vorticity by large-scale waves. Here we show that stationary waves in the Northern Hemisphere integrate tropical and extratropical impacts on TC activity in July through October. In particular, tropical upper-tropospheric troughs (TUTTs), as part of the summertime stationary waves, are associated with the var- iability of large-scale environmental conditions in the tropical North Atlantic and North Pacific and significantly correlated to the variability of TC activity in these basins. TUTTs are subject to the modulation of diabatic heating in various regions and are the preferred locations for extratropical Rossby wave breaking (RWB). A strong TUTT in a basin is associated with enhanced RWB and tropical−extratropical stirring in that basin, and the resultant changes in the tropical atmospheric conditions modulate TC activ- ity. In addition, the anticorrelation of TUTTs between the North Atlantic and North Pacific makes the TC activity indices over the two basins compensate each other, rendering the global TC activ- ity less variable than otherwise would be the case if TUTTs were independent.</p> </div> </div> </div> </div>

Unraveling the Asteromenia peltata species complex with clarification of the genera Halichrysis and Drouetia (Rhodymeniaceae, Rhodophyta)

2006 ◽  
Vol 84 (10) ◽  
pp. 1581-1607 ◽  
Author(s):  
Gary W. Saunders ◽  
Christopher E. Lane ◽  
Craig W. Schneider ◽  
Gerald T. Kraft
Keyword(s):  
Western Australia ◽  
North Atlantic ◽  
Distinct Species ◽  
Senior Author ◽  
Anatomical Features ◽  
Lord Howe Island ◽  
Tropical North Atlantic ◽  
Eastern Australia ◽  
Houtman Abrolhos Islands

The senior author was fortunate in 1996 to dive on the remote Houtman Abrolhos Islands of Western Australia and view in situ the stunning “ Asteromenia peltata ” that is so strikingly illustrated by John Huisman (viewable on AlgaeBase). Five years later, during excursions to Bermuda and Lord Howe Island (tropical eastern Australia), he observed and collected specimens referable to this species in both these localities. Based on their respective appearances in the field, it seemed unlikely that these entities from geographically remote regions represented the same species. Our molecular results not only confirm this suspicion, but further indicate that A. peltata sensu lato constitutes a complex of at least five distinct species. We restrict A. peltata to one of two species found in the western (sub)tropical North Atlantic, the second described herein as A. bermudensis sp. nov. Samples from Western Australia represent an undescribed species, A. exanimans sp. nov., while two entities collected from Lord Howe Island (A. anastomosans (Weber-van Bosse) comb. nov. and A. pseudocoalescens sp. nov.) conform to records variously reported as Asteromenia peltata and Drouetia coalescens . Specimens of D. coalescens from South Africa are also not representative of the genus Drouetia , but form a novel lineage within the Rhodymeniaceae. We included two species of Halichrysis in our molecular analyses and, in combination with observations of salient anatomical features, provide arguments for maintaining Asteromenia, Drouetia, and Halichrysis as distinct genera.

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