scholarly journals Virus Attachment to Transparent Exopolymeric Particles along Trophic Gradients in the Southwestern Lagoon of New Caledonia

2007 ◽  
Vol 73 (16) ◽  
pp. 5245-5252 ◽  
Author(s):  
Xavier Mari ◽  
Marie-Emmanuelle Kerros ◽  
Markus G. Weinbauer
Keyword(s):  
Hot Spots ◽  
Magnetic Beads ◽  
Water Mass ◽  
New Caledonia ◽  
Virus Attachment ◽  
Renewal Rate ◽  
Mixed Aggregates ◽  
Transparent Exopolymeric Particles ◽  
Virus Abundance ◽  
Trophic Gradients

ABSTRACT Viruses on organic aggregates such as transparent exopolymeric particles (TEP) are not well investigated. The number of TEP-attached viruses was assessed along trophic gradients in the southwestern lagoon of New Caledonia by determining the fraction of viruses removed after magnetic isolation of TEP. In order to isolate TEP magnetically, TEP were formed in the presence of magnetic beads from submicrometer precursors collected along the trophic gradients. The mixed aggregates of TEP-beads-viruses were removed from solution with a magnetic field. The percentage of viruses associated with newly formed TEP averaged 8% (range, 3 to 13%) for most of the stations but was higher (ca. 30%) in one bay characterized by the low renewal rate of its water mass. The number of viruses (N) attached to TEP varied as a function of TEP size (d [in micrometers]) according to the formulas N = 100d 1.60 and N = 230d 1.75, respectively, for TEP occurring in water masses with short (i.e., <40 days) and long (i.e., >40 days) residence times. These two relationships imply that viral abundance decreases with TEP size, and they indicate that water residence time influences viral density and virus-bacterium interactions within aggregates. Our data suggest that the fraction of viruses attached to TEP is highest in areas characterized by a low renewal rate of the water mass and can constitute at times a significant fraction of total virus abundance. Due to the small distance between viruses and hosts on TEP, these particles may be hot spots for viral infection.

Euphausiids in the Coral and Tasman Seas during May 1972. II. Horizontal Distribution in relation to Circulation Patterns

1979 ◽  
Vol 30 (5) ◽  
pp. 569 ◽  
Author(s):  
FB Griffiths
Keyword(s):  
Water Mass ◽  
New Caledonia ◽  
Solomon Islands ◽  
Horizontal Distribution ◽  
Central Pacific ◽  
Circulation Patterns ◽  
Group A ◽  
Group B ◽  
High Degree ◽  
Group D

An examination of the euphausiid species collected at two stations, 20� S.,153� E. and 33� 40'S.,153� E., during May 1972 showed that 21 of the 33 epipelagic and mesopelagic species were common to both stations. This suggests a high degree of water mass continuity between these two stations. This paper discusses the horizontal distribution of 10 species, divided into four groups, who show range extensions that are related to circulation patterns in the Coral and Tasman Seas. The presence of group A animals (Thysanopoda tricuspidata, Euphausia diomedeae, E. pseudogibba, and Nematoscelis gracilis) at the southern station supports the theory that there is a southward movement of South Equatorial water from between the Solomon Islands and New Caledonia to at least 33� 44'S. This water must have passed over, or close to the continental shelf, probably as part of the East Australian Current in order for the neritic Pseudeuphausia latrifrons (group B) to be caught at the southern station. The species present in group C (Euphausia similis and Thysanoessa gregaria) indicate there had been northern transport of central Tasman water to at least 20� S., possibly along 160� E. or further east. Finally, the group D species (Euphausia brevis, Nematoscelis atlantica and N. tenella) suggest there may have been some westwards flow from the west central Pacific region, possibly during the previous June-December period.

scholarly journals Dynamics of transparent exopolymer particles (TEP) during the VAHINE mesocosm experiment in the New Caledonia lagoon

2016 ◽  
Author(s):  
I. Berman-Frank ◽  
D. Spungin ◽  
E. Rahav ◽  
F. Van Wambeke ◽  
K. Turk-Kubo ◽  
...  
Keyword(s):  
Bacterial Production ◽  
Temporal Dynamics ◽  
New Caledonia ◽  
Inorganic Phosphorus ◽  
Second Phase ◽  
Physical Processes ◽  
Dissolved Carbon ◽  
Spatial And Temporal Dynamics ◽  
Transparent Exopolymeric Particles ◽  
Diazotrophic Growth

Abstract. In the marine environment, transparent exopolymeric particles (TEP) produced from abiotic and biotic sources link the particulate and dissolved carbon pools and are essential vectors enhancing vertical carbon flux. We characterized spatial and temporal dynamics of TEP during the VAHINE experiment that investigated the fate of diazotroph derived nitrogen and carbon in three, replicate, dissolved inorganic phosphorus (DIP)-fertilized 50 m3 enclosures in an oligotrophic New Caledonian lagoon. During the 23 days of the experiment, we did not observe any depth dependent changes in TEP concentrations in the three sampled-depths (1, 6, 12 m). TEP carbon (TEP-C) content per mesocosm averaged 28.9 ± 9.3% and 27.0 ± 7.2% of TOC in the mesocosms and surrounding lagoon respectively and was strongly and positively coupled with TOC during P2. TEP concentrations declined for the first 9 days after DIP fertilization (P1 = days 5-14) and then gradually increased during the second phase (P2 = days 15-23). Temporal changes in TEP concentrations paralleled the growth and mortality rates of the diatom-diazotroph association of Rhizosolenia and Richelia that predominated the diazotroph community during P1. By P2, increasing total primary and heterotrophic bacterial production consumed the supplemented P and reduced availability of DIP. For this period, TEP concentrations were negatively correlated with DIP availability and turnovertime of DIP (TDIP) while positively associated with enhanced alkaline phosphatase activity (APA) that occurs when the microbial populations are P-stressed. During P2, increasing bacterial production (BP) was positively correlated with higher TEP concentrations which were also coupled with the increased growth rates and aggregation of the unicellular UCYN-C diazotrophs which bloomed during this period. We conclude that the composite processes responsible for the formation and breakdown of TEP yielded a relatively stable TEP pool available as both a carbon source and facilitating aggregation and flux throughout the experiment. TEP was probably mostly influenced by abiotic physical processes during P1 while biological activity (BP, diazotrophic growth and aggregation, export production) mainly impacted TEP concentrations during P2 when DIP-availability was limited.

scholarly journals Post-Bomb Radiocarbon Records of Surface Corals from the Tropical Atlantic Ocean

Radiocarbon ◽  
1996 ◽  
Vol 38 (3) ◽  
pp. 563-572 ◽  
Author(s):  
Ellen R. M. Druffel
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Water Mass ◽  
Cape Verde ◽  
North Equatorial Current ◽  
Tropical Atlantic ◽  
Tropical Ocean ◽  
Tropical Atlantic Ocean ◽  
Renewal Rate ◽  
The North

Δ14C records are reported for post-bomb corals from three sites in the tropical Atlantic Ocean. In corals from 18°S in the Brazil Current, Δ14C values increased from ca. −58% in the early 1950s to +138% by 1974, then decreased to 110‰ by 1982. Shorter records from 8ºS off Brazil and from the Cape Verde Islands (17°N) showed initially higher Δ14C values before 1965 than those at 18ºS, but showed lower rates of increase of Δ14C during the early 1960s. There is general agreement between the coral results and Δ14C of dissolved inorganic carbon (DIC) measured in seawater previously for locations in the tropical Atlantic Ocean. Δ14C values at our tropical ocean sites increased at a slower rate than those observed previously in the temperate North Atlantic (Florida and Bermuda), owing to the latter's proximity to the bomb 14C input source in the northern, hemisphere. Model results show that from 1960–1980 the Cape Verde coral and selected DIG Δ14C values from the North Equatorial Current agree with that calculated for the North Atlantic based on an isopycnal mixing model with a constant water mass renewal rate between surface and subsurface waters. This is in contrast to Δ14C values in Bermuda corals that showed higher post-bomb values than those predicted using a constant water mass renewal rate, hence indicating that ventilation in the western north Atlantic Ocean had decreased by a factor of 3 during the 1960s and 1970s (Druffel 1989).

The continuity of water masses along the western boundary of the Tasman and Coral Seas

1968 ◽  
Vol 19 (2) ◽  
pp. 77 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Water Mass ◽  
New Caledonia ◽  
Core Layer ◽  
Water Masses ◽  
Western Boundary ◽  
Intermediate Water ◽  
North West ◽  
The North ◽  
Coral Sea ◽  
Intermediate Water Mass

Hydrological data of the Umitaka Maru (December 1967) and of H.M.A.S. Gascoyne (November-December 1965) have been used to show continuity of selected water masses from the north-west Coral Sea to the continental margin off New South Wales. The core layer properties of these water masses (salinity, temperature, oxygen) indicate that these water masses of the north-west Coral Sea are formed by the inflow from the east of the South Equatorial water mass (0 m), the upper salinity maximum water mass (150-200 m) of the central South Pacific, and of the Antarctic Intermediate water mass (800-1000 m). The inflow of the first two occurs immediately south of the Solomon Is. whilst that of the third occurs between New Caledonia and the New Hebrides. Continuity of the upper oxygen maximum of the 200-800 m layer was not examined because of doubts as to its existence as a separate water mass.

scholarly journals Mechanisms of <i>Trichodesmium</i> bloom demise within the New Caledonia Lagoon during the VAHINE mesocosm experiment

2016 ◽  
Author(s):  
D. Spungin ◽  
U. Pfreundt ◽  
H. Berthelot ◽  
S. Bonnet ◽  
D. AlRoumi ◽  
...  
Keyword(s):  
Surface Waters ◽  
New Caledonia ◽  
Specific Activity ◽  
Rapid Decline ◽  
Ambient Conditions ◽  
Nutrient Storage ◽  
Cellular Processes ◽  
Extensive Surface ◽  
High Concentrations ◽  
Transparent Exopolymeric Particles

Abstract. The globally important marine diazotrophic cyanobacterium Trichodesmium blooms regularly in the New Caledonian lagoons (Sowthwestern Pacific). We exploited the development of a Trichodesmium bloom in the lagoon waters outside the enclosed VAHINE mesocosms to specifically investigate the cellular processes mediating its decline. Trichodesmium cells (and associated microbiota) were sampled from the time of surface accumulation to biomass demise using a series of enclosed incubations to elucidate the stressors and subcellular underpinning of rapid (~ 24 h) biomass demise and disappearance. The development and decline of Trichodesmium populations was rapid with extensive surface accumulations (blooms) appearing within 24 h on the surface waters of the lagoon. Rapid decline of > 90 % biomass after 24 h of peak accumulation was observed in p opulations that were collected and incubated under ambient conditions. Metatranscriptomic profiling of Trichodesmium biomass 8 h and 22 h after bottle incubation of surface accumulations revealed evidence for phosphorus (P) and iron (Fe) stress, with upreg ulation of genes required to increase their availability and transport. In contrast, genes responsible for nutrient storage were downregulated. Total viral abundance, assessed by SYBR-green staining and analytical flow cytometry, oscillated throughout the experiment and showed no significant relationship with Trichodesmium bloom development or demise. Enhanced caspase-specific activity and upregulation of a suite of metacaspase genes during bloom demise implicated autocatalytic programmed cell death (PCD) as the mechanistic cause. At the same time, genes associated with buoyancy and gas-vesicle production were strongly downregulated concomitant with high concentrations of transparent exopolymeric particles (TEP), greatly aiding aggregation and expediting vertical flux to depth. Our results demonstrate that the rapid demise of this high-density, Trichodesmium surface bloom over 24 h was not caused by specific lytic infection but was rather induced by PCD in response to combined nutrient and oxidative stressors.

scholarly journals Aphotic N<sub>2</sub> fixation along an oligotrophic to ultraoligotrophic transect in the western tropical South Pacific Ocean

2018 ◽  
Vol 15 (10) ◽  
pp. 3107-3119 ◽  
Author(s):  
Mar Benavides ◽  
Katyanne M. Shoemaker ◽  
Pia H. Moisander ◽  
Jutta Niggemann ◽  
Thorsten Dittmar ◽  
...  
Keyword(s):  
N2 Fixation ◽  
Water Mass ◽  
New Caledonia ◽  
Hot Spot ◽  
Nifh Gene ◽  
South Pacific ◽  
French Polynesia ◽  
Mode Water ◽  
Fixation Activity ◽  
Nitrogen Inputs

Abstract. The western tropical South Pacific (WTSP) Ocean has been recognized as a global hot spot of dinitrogen (N2) fixation. Here, as in other marine environments across the oceans, N2 fixation studies have focused on the sunlit layer. However, studies have confirmed the importance of aphotic N2 fixation activity, although until now only one had been performed in the WTSP. In order to increase our knowledge of aphotic N2 fixation in the WTSP, we measured N2 fixation rates and identified diazotrophic phylotypes in the mesopelagic layer along a transect spanning from New Caledonia to French Polynesia. Because non-cyanobacterial diazotrophs presumably need external dissolved organic matter (DOM) sources for their nutrition, we also identified DOM compounds using Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) with the aim of searching for relationships between the composition of DOM and non-cyanobacterial N2 fixation in the aphotic ocean. N2 fixation rates were low (average 0.63 ± 0.07 nmol N L−1 d−1) but consistently detected across all depths and stations, representing ∼ 6–88 % of photic N2 fixation. N2 fixation rates were not significantly correlated with DOM compounds. The analysis of nifH gene amplicons revealed a wide diversity of non-cyanobacterial diazotrophs, mostly matching clusters 1 and 3. Interestingly, a distinct phylotype from the major nifH subcluster 1G dominated at 650 dbar, coinciding with the oxygenated Subantarctic Mode Water (SAMW). This consistent pattern suggests that the distribution of aphotic diazotroph communities is to some extent controlled by water mass structure. While the data available are still too scarce to elucidate the distribution and controls of mesopelagic non-cyanobacterial diazotrophs in the WTSP, their prevalence in the mesopelagic layer and the consistent detection of active N2 fixation activity at all depths sampled during our study suggest that aphotic N2 fixation may contribute significantly to fixed nitrogen inputs in this area and/or areas downstream of water mass circulation.

Ultrastructure of Some Planktonic Formainifera

1974 ◽  
Vol 32 ◽  
pp. 190-191
Author(s):  
William H. Zucker
Keyword(s):  
Cell Biology ◽  
Water Mass ◽  
Planktonic Foraminifera ◽  
Uranyl Acetate ◽  
Ethanol Dehydration ◽  
Globigerinoides Ruber ◽  
Light Microscope Level ◽  
Globigerina Bulloides ◽  
Glutaraldehyde Solution ◽  
Diamond Knife

Planktonic foraminifera are widely-distributed and abundant zooplankters. They are significant as water mass indicators and provide evidence of paleotemperatures and events which occurred during Pleistocene glaciation. In spite of their ecological and paleological significance, little is known of their cell biology. There are few cytological studies of these organisms at the light microscope level and some recent reports of their ultrastructure.Specimens of Globigerinoides ruber, Globigerina bulloides, Globigerinoides conglobatus and Globigerinita glutinata were collected in Bermuda waters and fixed in a cold cacodylate-buffered 6% glutaraldehyde solution for two hours. They were then rinsed, post-fixed in Palade's fluid, rinsed again and stained with uranyl acetate. This was followed by graded ethanol dehydration, during which they were identified and picked clean of debris. The specimens were finally embedded in Epon 812 by placing each organism in a separate BEEM capsule. After sectioning with a diamond knife, stained sections were viewed in a Philips 200 electron microscope.

A high-performance oil-free backing pump for electron microscopes

1978 ◽  
Vol 36 (1) ◽  
pp. 110-111
Author(s):  
G.K.W. Balkau ◽  
E. Bez ◽  
J.L. Farrant
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Hot Spots ◽  
High Performance ◽  
Carbonaceous Material ◽  
Contamination Rate ◽  
Low Molecular Weight ◽  
Principal Source ◽  
Rotary Pumps ◽  
Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

Human Adenovirus Uptake by Preirnplantation Mouse Embryos

1972 ◽  
Vol 30 ◽  
pp. 268-269
Author(s):  
D. G. Chase ◽  
W. Winters ◽  
L. Piko
Keyword(s):  
Hela Cells ◽  
Human Adenovirus ◽  
Mouse Embryos ◽  
Equilibrium Density ◽  
Cell Stage ◽  
Virus Attachment ◽  
Preimplantation Mouse Embryos ◽  
Embryo Culture Medium ◽  
Preimplantation Mouse ◽  
Mouse Cells

Although the outlines of human adenovirus entry and uncoating in HeLa cells has been clarified in recent electron microscope studies, several details remain unclear or controversial. Furthermore, morphological features of early interactions of human adenovirus with non-permissive mouse cells have not been extensively documented. In the course of studies on the effects of human adenoviruses type 5 (AD-5) and type 12 on cultured preimplantation mouse embryos we have examined virus attachment, entry and uncoating. Here we present the ultrastructural findings for AD-5.AD-5 was grown in HeLa cells and purified by successive velocity gradient and equilibrium density gradient centrifugations in CsCl. After dialysis against PBS, virus was sedimented and resuspended in embryo culture medium. Embryos were placed in culture at the 2-cell stage in Brinster's medium.

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