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.

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 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

Phylogeny and biogeography of the Australasian centipede Henicops (Chilopoda: Lithobiomorpha): A combined morphological and molecular approach

2006 ◽  
Vol 37 (3) ◽  
pp. 241-256 ◽  
Author(s):  
Donald Colgan ◽  
Gregory Edgecombe ◽  
Deirdre Sharkey
Keyword(s):  
New Zealand ◽  
Western Australia ◽  
New Caledonia ◽  
Sequence Data ◽  
Morphological Characters ◽  
Molecular Data ◽  
28S Rrna ◽  
Southeastern Australia ◽  
Lord Howe Island ◽  
Eastern Australia

AbstractThe lithobiomorph centipede Henicops is widely distributed in Australia and New Zealand, with five described species, as well as two species in New Caledonia and Lord Howe Island. Parsimony, maximum likelihood and Bayesian analyses of ca. 800 aligned bases of sequence data from 16S rRNA and 28S rRNA were conducted on a dataset including multiple individuals of Henicops species from populations sampled from different parts of species' geographic ranges, together with the allied henicopines Lamyctes and Easonobius. Morphological characters are included in parsimony analyses. Molecular and combined datasets unite species from eastern Australia and New Zealand to the exclusion of species from Western Australia, New Caledonia and Lord Howe Island. The molecular data favour these two geographic groupings as clades, whereas inclusion of morphology resolves New Caledonia, Lord Howe Island, southwest Western Australia and Queensland as successive sisters to southeastern Australia and New Zealand. The basal position of the Lord Howe Island species in the phylogeny favours a diversification of Australasian Henicops since the late Miocene unless the Lord Howe species originated in a biota that pre-dates the island. The molecular and combined data resolve the widespread morphospecies H. maculatus as paraphyletic, with its populations contributing to the geographic groupings New South Wales + New Zealand and Tasmania + Victoria.

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.

Morphological evaluation of the Drosera peltata complex (Droseraceae)

2012 ◽  
Vol 25 (1) ◽  
pp. 49 ◽  
Author(s):  
Robert Gibson ◽  
Barry J. Conn ◽  
Jeremy J. Bruhl
Keyword(s):  
New Zealand ◽  
Western Australia ◽  
Distinct Species ◽  
Morphological Characters ◽  
South Eastern ◽  
Morphological Evaluation ◽  
Granite Outcrops ◽  
Eastern Australia ◽  
North Eastern ◽  
South Eastern Australia

A phenetic study of morphological characters of the Drosera peltata complex (Droseraceae) supports the recognition of the following taxa: D. peltata from wetlands of south-eastern Australia; D. auriculata from south-eastern Australia and New Zealand; the morphologically variable D. hookeri from south-eastern Australia and northern New Zealand; the widespread D. lunata from southern and South-East Asia, as well as northern and north-eastern Australia; and the new species D. yilgarnensis R.P.Gibson & B.J.Conn is here described, from around granite outcrops of south-western Australia. D. bicolor from south-western Australia is recognised as a distinct species outside of the D. peltata complex. D. insolita, considered until recently as a distinct species, is reduced to synonymy of D. lunata. Phenotypic plasticity, vegetative similarity and fleetingly produced diagnostic floral and seed characters within the complex pose significant challenges in understanding the taxonomy of these taxa.

scholarly journals Net radiative effects of dust in the tropical North Atlantic based on integrated satellite observations and in situ measurements

2018 ◽  
Vol 18 (15) ◽  
pp. 11303-11322 ◽  
Author(s):  
Qianqian Song ◽  
Zhibo Zhang ◽  
Hongbin Yu ◽  
Seiji Kato ◽  
Ping Yang ◽  
...  
Keyword(s):  
Particle Size ◽  
Refractive Index ◽  
Dust Particle ◽  
North Atlantic ◽  
In Situ Measurements ◽  
Radiative Properties ◽  
Radiative Effects ◽  
Tropical North Atlantic ◽  
Holistic Understanding

Abstract. In this study, we integrate recent in situ measurements with satellite retrievals of dust physical and radiative properties to quantify dust direct radiative effects on shortwave (SW) and longwave (LW) radiation (denoted as DRESW and DRELW, respectively) in the tropical North Atlantic during the summer months from 2007 to 2010. Through linear regression of the CERES-measured top-of-atmosphere (TOA) flux versus satellite aerosol optical depth (AOD) retrievals, we estimate the instantaneous DRESW efficiency at the TOA to be -49.7±7.1 W m−2 AOD−1 and -36.5±4.8 W m−2 AOD−1 based on AOD from MODIS and CALIOP, respectively. We then perform various sensitivity studies based on recent measurements of dust particle size distribution (PSD), refractive index, and particle shape distribution to determine how the dust microphysical and optical properties affect DRE estimates and its agreement with the above-mentioned satellite-derived DREs. Our analysis shows that a good agreement with the observation-based estimates of instantaneous DRESW and DRELW can be achieved through a combination of recently observed PSD with substantial presence of coarse particles, a less absorptive SW refractive index, and spheroid shapes. Based on this optimal combination of dust physical properties we further estimate the diurnal mean dust DRESW in the region of −10 W m−2 at TOA and −26 W m−2 at the surface, respectively, of which ∼ 30 % is canceled out by the positive DRELW. This yields a net DRE of about −6.9 and −18.3 W m−2 at TOA and the surface, respectively. Our study suggests that the LW flux contains useful information on dust particle size, which could be used together with SW observations to achieve a more holistic understanding of the dust radiative effect.

scholarly journals North Atlantic warming over six decades drives decreases in krill abundance with no associated range shift

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Martin Edwards ◽  
Pierre Hélaouët ◽  
Eric Goberville ◽  
Alistair Lindley ◽  
Geraint A. Tarling ◽  
...  
Keyword(s):  
North Atlantic ◽  
Range Shift ◽  
The Core ◽  
Krill Abundance ◽  
The North ◽  
Living Space ◽  
Warming Climate ◽  
Two Temperatures ◽  
The North Atlantic

AbstractIn the North Atlantic, euphausiids (krill) form a major link between primary production and predators including commercially exploited fish. This basin is warming very rapidly, with species expected to shift northwards following their thermal tolerances. Here we show, however, that there has been a 50% decline in surface krill abundance over the last 60 years that occurred in situ, with no associated range shift. While we relate these changes to the warming climate, our study is the first to document an in situ squeeze on living space within this system. The warmer isotherms are shifting measurably northwards but cooler isotherms have remained relatively static, stalled by the subpolar fronts in the NW Atlantic. Consequently the two temperatures defining the core of krill distribution (7–13 °C) were 8° of latitude apart 60 years ago but are presently only 4° apart. Over the 60 year period the core latitudinal distribution of euphausiids has remained relatively stable so a ‘habitat squeeze’, with loss of 4° of latitude in living space, could explain the decline in krill. This highlights that, as the temperature warms, not all species can track isotherms and shift northward at the same rate with both losers and winners emerging under the ‘Atlantification’ of the sub-Arctic.

scholarly journals Particle export fluxes to the oxygen minimum zone of the eastern tropical North Atlantic

2017 ◽  
Vol 14 (7) ◽  
pp. 1825-1838 ◽  
Author(s):  
Anja Engel ◽  
Hannes Wagner ◽  
Frédéric A. C. Le Moigne ◽  
Samuel T. Wilson
Keyword(s):  
Organic Matter ◽  
North Atlantic ◽  
Organic Phosphorus ◽  
Euphotic Zone ◽  
Carbon Export ◽  
Organic Matter Quality ◽  
B Values ◽  
Chl A ◽  
Tropical North Atlantic ◽  
Particle Export

Abstract. In the ocean, sinking of particulate organic matter (POM) drives carbon export from the euphotic zone and supplies nutrition to mesopelagic communities, the feeding and degradation activities of which in turn lead to export flux attenuation. Oxygen (O2) minimum zones (OMZs) with suboxic water layers (< 5 µmol O2 kg−1) show a lower carbon flux attenuation compared to well-oxygenated waters (> 100 µmol O2 kg−1), supposedly due to reduced heterotrophic activity. This study focuses on sinking particle fluxes through hypoxic mesopelagic waters (< 60 µmol O2 kg−1); these represent  ∼  100 times more ocean volume globally compared to suboxic waters, but they have less been studied. Particle export fluxes and attenuation coefficients were determined in the eastern tropical North Atlantic (ETNA) using two surface-tethered drifting sediment trap arrays with seven trapping depths located between 100 and 600 m. Data on particulate matter fluxes were fitted to the normalized power function Fz =  F100 (z∕100)−b, with F100 being the flux at a depth (z) of 100 m and b being the attenuation coefficient. Higher b values suggest stronger flux attenuation and are influenced by factors such as faster degradation at higher temperatures. In this study, b values of organic carbon fluxes varied between 0.74 and 0.80 and were in the intermediate range of previous reports, but lower than expected from seawater temperatures within the upper 500 m. During this study, highest b values were determined for fluxes of particulate hydrolyzable amino acids (PHAA), followed by particulate organic phosphorus (POP), nitrogen (PN), carbon (POC), chlorophyll a (Chl a) and transparent exopolymer particles (TEP), pointing to a sequential degradation of organic matter components during sinking. Our study suggests that in addition to O2 concentration, organic matter composition co-determines transfer efficiency through the mesopelagic. The magnitude of future carbon export fluxes may therefore also depend on how organic matter quality in the surface ocean changes under influence of warming, acidification and enhanced stratification.

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