scholarly journals Bio-Optical Characterization and Ocean Colour Inversion in the Eastern Lagoon of New Caledonia, South Tropical Pacific

2018 ◽  
Vol 10 (7) ◽  
pp. 1043 ◽  
Author(s):  
Luciane Favareto ◽  
Natália Rudorff ◽  
Milton Kampel ◽  
Robert Frouin ◽  
Rüdiger Röttgers ◽  
...  
Keyword(s):  
New Caledonia ◽  
Optical Characterization ◽  
Tropical Pacific ◽  
Ocean Colour

scholarly journals A standardized database of Marine Isotopic Stage 5e sea-level proxies on tropical Pacific Islands

2020 ◽  
Author(s):  
Nadine Hallmann ◽  
Gilbert Camoin ◽  
Jody M. Webster ◽  
Marc Humblet
Keyword(s):  
Coral Reef ◽  
Sea Level ◽  
Pacific Islands ◽  
New Caledonia ◽  
Tropical Pacific ◽  
Marshall Islands ◽  
Last Interglacial ◽  
Federal States ◽  
Mis 5E ◽  
Holocene Sea Level

Abstract. Marine isotope stage 5 deposits have been reported on many tropical Pacific islands. This paper presents a database compiled through the review of MIS 5e (Last Interglacial – LIG) coral reef records from islands belonging to French Polynesia (Anaa, Niau, Makatea, Moruroa, Takapoto, Bora Bora), the Hawaiian Islands (Oahu, Lana'i, Midway Atoll), Tuvalu, Kiribati (Christmas Island, Tarawa), the Cook Islands (Mangaia, Atiu, Mitiaro, Mauke, Pukapuka, Rakahanga, Rarotonga), Tonga, Samoa, the Federal States of Micronesia, the Mariana Islands, the Marshall Islands (Enewetak, Bikini), New Caledonia, Papua New Guinea, Vanuatu, Fiji and Niue. Studies reporting other sea-level indicators dated to other Pleistocene interglacials and Holocene sea-level indicators were not inserted in the database, but are included in this data description paper for completeness. Overall, about 300 studies concerning Pleistocene and Holocene sea-level indicators have been reviewed, and finally 284 data points from 35 studies on the MIS 5e have been inserted in the database. The main sea-level indicators include emerged coral reef terraces, but also reef units recovered in drill cores from a few islands, thus reflecting the diversity of tectonic settings and sampling approaches. Future research should be directed towards better constrained relative sea-level (RSL) reconstructions, including more precise chronological data, more accurate elevation measurements as well as a better refinement of the palaeo-water depth significance of coralgal assemblages. The database for Tropical Pacific Islands is available open-access at this link: http://doi.org/10.5281/zenodo.3991672 (Hallmann and Camoin, 2020).

Mid- to late Holocene environmental and climatic changes in New Caledonia, southwest tropical Pacific, inferred from the littoral plain Gouaro-Déva

2011 ◽  
Vol 76 (2) ◽  
pp. 229-242 ◽  
Author(s):  
Denis Wirrmann ◽  
Anne-Marie Sémah ◽  
Jean-Pierre Debenay ◽  
Magali Chacornac-Rault
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
Environmental Changes ◽  
New Caledonia ◽  
High Energy ◽  
Climatic Changes ◽  
Tropical Pacific ◽  
Energy Conditions ◽  
Enso Variability ◽  
Freshwater Swamp

AbstractMultiproxy analysis of three littoral cores from western New Caledonia supports the hypothesis that the main controlling factors of environmental changes are sea-level change, ENSO variability and extra-tropical phenomena, such as the Medieval Warm Period (MWP) marked by a tendency for La Niña-like conditions in the tropical Pacific. The record starts during the late Holocene sea-level rise when the terrestrial vegetation indicated wet and cool conditions. The site was a coastal bay definitely transformed into a freshwater swamp at around 3400 cal yr BP, after the rapid drawdown of sea level to its current level. Sediments and foraminiferal assemblages indicated subsequent episodes of freshwater infillings, emersion or very high-energy conditions, likely related to climatic changes and mostly controlled by ENSO variability. Between 2750 and 2000 cal yr BP, relatively dry and cool climate prevailed, while wetter conditions predominated between ca. 1800 and 900 cal yr BP. The Rhizophoraceae peak between ca. 1080 and 750 cal yr BP, coeval with the MWP, may indicate a global phenomenon. Microcharcoal particles present throughout the record increased after 1500 cal yr BP, suggesting an anthropogenic source. From ca. 750 cal yr BP the appearance of current type of vegetation marks the human impact.

Optical characterization and assessment of ocean colour algorithms in Chilika Lagoon

2016 ◽  
Author(s):  
Aneesh A. Lotliker ◽  
Subhashree Sahoo ◽  
S. K. Baliarsingh ◽  
C. Parida ◽  
K. C. Sahu
Keyword(s):  
Optical Characterization ◽  
Chilika Lagoon ◽  
Ocean Colour

scholarly journals Silicon cycle in the Tropical South Pacific: evidence for an active pico-sized siliceous plankton

2018 ◽  
Author(s):  
Karine Leblanc ◽  
Véronique Cornet ◽  
Peggy Rimmelin-Maury ◽  
Olivier Grosso ◽  
Sandra Hélias-Nunige ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Biogenic Silica ◽  
New Caledonia ◽  
South Pacific ◽  
Tropical Pacific ◽  
Biogeochemical Cycle ◽  
Silicon Cycle ◽  
Standing Stocks ◽  
Negligible Contribution

Abstract. This article presents data regarding the Si biogeochemical cycle during two oceanographic cruises conducted in the Southern Tropical Pacific (BIOSOPE and OUTPACE cruises) in 2005 and 2015. It involves the first Si stock measurements in this understudied region, encompassing various oceanic systems from New Caledonia to the Chilean upwelling between 8 and 34° S. Some of the lowest levels of biogenic silica standing stocks ever measured were found in this area, notably in the Southern Pacific Gyre, where Chlorophyll a concentrations are most depleted worldwide. Integrated biogenic silica stocks are as low as 1.08 ± 0.95 mmol m−2, and are the lowest stocks measured in the Southern Pacific. Size-fractionated biogenic silica concentrations revealed a non-negligible contribution of the pico-sized fraction (

scholarly journals Diazotrophic <i>Trichodesmium</i> influence on ocean color and pigment composition in the South West tropical Pacific

2018 ◽  
Author(s):  
Cécile Dupouy ◽  
Robert Frouin ◽  
Marc Tedetti ◽  
Morgane Maillard ◽  
Martine Rodier ◽  
...  
Keyword(s):  
High Performance ◽  
New Caledonia ◽  
Principal Component ◽  
Euphotic Zone ◽  
Tropical Pacific ◽  
The South ◽  
South West ◽  
Underwater Vision ◽  
Fiji Islands ◽  
High Fluorescence

Abstract. We assessed the influence of the marine diazotrophic cyanobacterium Trichodesmium on the bio-optical properties of South West tropical Pacific waters (18–22° S, 160° E–160° W) during the February–March 2015 OUTPACE cruise. We performed measurements of backscattering and absorption coefficients, irradiance, and radiance, in the euphotic zone, and took Underwater Vision Profiler 5 (UPV5) pictures for counting the largest Trichodesmium spp. colonies. Pigment concentrations were determined by fluorimetry and by high performance liquid chromatography and picoplankton abundance by flow cytometry. Trichome concentration was estimated from pigment algorithms and validated by surface visual counts. In result, the large colonies were well correlated to the trichome concentration estimates (though with a large factor of 600 to 900, due to aggregation processes). Large Trichodesmium abundance was always associated with particulate absorption at a peak of mycosporine-like amino acid absorption, and high particulate backscattering, but not with high fluorescence, high chlorophyll-a concentration, or blue particulate absorption in the water column. Along the West to East transect, Trichodesmium together with Prochlorococcus represented the major part of total chlorophyll and the other groups were negligible. Trichodesmium contribution to chlorophyll was the highest in the Melanesian Archipelago around New Caledonia and Vanuatu, progressively decreased to the vicinity of the Fiji Islands, and reached a minimum in the South Pacific gyre where the contribution of Prochlorococcus was maximum. At the frontal LDB, Trichodesmium and Prochlorococcus has almost same contributions. The relationship between normalized water-leaving radiance, in the ultraviolet and visible domains, nLw, and chlorophyll was generally similar to that found in the Eastern tropical at BIOSOPE. Principal component analysis (PCA) of OUTPACE data showed that nLw were strongly correlated to chlorophyll except in the green and yellow domains. These results, as well as differences in the PCA of BIOSOPE data, suggested that nLw variability in the green and yellow during OUTPACE was influenced by other variables, associated with Trichodesmium presence as the backscattering coefficient, phycoerythrin fluorescence, and/or zeaxanthin absorption. Trichodesmium detection should then involve examination of nLw at the green and yellow wavelengths.

scholarly journals An algorithm for detecting <i>Trichodesmium</i> surface blooms in the South Western Tropical Pacific

2011 ◽  
Vol 8 (12) ◽  
pp. 3631-3647 ◽  
Author(s):  
C. Dupouy ◽  
D. Benielli-Gary ◽  
J. Neveux ◽  
Y. Dandonneau ◽  
T. K. Westberry
Keyword(s):  
Co2 Sequestration ◽  
New Caledonia ◽  
Tropical Pacific ◽  
The South ◽  
Western Tropical Pacific ◽  
Tropical Oceans ◽  
Fiji Islands ◽  
C And N ◽  
In Situ Observations

Abstract. Trichodesmium, a major colonial cyanobacterial nitrogen fixer, forms large blooms in NO3-depleted tropical oceans and enhances CO2 sequestration by the ocean due to its ability to fix dissolved dinitrogen. Thus, its importance in C and N cycles requires better estimates of its distribution at basin to global scales. However, existing algorithms to detect them from satellite have not yet been successful in the South Western Tropical Pacific (SP). Here, a novel algorithm (TRICHOdesmium SATellite) based on radiance anomaly spectra (RAS) observed in SeaWiFS imagery, is used to detect Trichodesmium during the austral summertime in the SP (5° S–25° S 160° E–170° W). Selected pixels are characterized by a restricted range of parameters quantifying RAS spectra (e.g. slope, intercept, curvature). The fraction of valid (non-cloudy) pixels identified as Trichodesmium surface blooms in the region is low (between 0.01 and 0.2 %), but is about 100 times higher than deduced from previous algorithms. At daily scales in the SP, this fraction represents a total ocean surface area varying from 16 to 48 km2 in Winter and from 200 to 1000 km2 in Summer (and at monthly scale, from 500 to 1000 km2 in Winter and from 3100 to 10 890 km2 in Summer with a maximum of 26 432 km2 in January 1999). The daily distribution of Trichodesmium surface accumulations in the SP detected by TRICHOSAT is presented for the period 1998–2010 which demonstrates that the number of selected pixels peaks in November–February each year, consistent with field observations. This approach was validated with in situ observations of Trichodesmium surface accumulations in the Melanesian archipelago around New Caledonia, Vanuatu and Fiji Islands for the same period.

Rhipidocotyle labroidei n. sp. (Digenea: Bucephalidae) from Labroides dimidiatus (Valenciennes) (Labridae)

Zootaxa ◽  
2003 ◽  
Vol 327 (1) ◽  
pp. 1 ◽  
Author(s):  
CONOR M. JONES ◽  
ALEXANDRA S. GRUTTER ◽  
THOMAS H. CRIBB
Keyword(s):  
Great Barrier Reef ◽  
New Caledonia ◽  
Tropical Pacific ◽  
Barrier Reef ◽  
Cleaner Fish ◽  
Labroides Dimidiatus ◽  
The Tropical Pacific

Rhipidocotyle labroidei n. sp. is described from the rectum of cleaner fish, Labroides dimidiatus (Labridae), on the Great Barrier Reef. R. labroidei differs from its congeners by the combination of its small size, anteriorly directed caecum, the shape and positioning of its gonads, and by its posteriorly confined uterus. We have found Rhipidocotyle in species of Labroides from New Caledonia and Moorea that differ from the described material in the size of eggs, but these worms are not suitable for description. We suggest there are at least two species of Rhipidocotyle in Labroides spp. from the tropical Pacific.

scholarly journals Modelling the processes driving <i>Trichodesmium</i> sp. spatial distribution and biogeochemical impact in the tropical Pacific Ocean

2018 ◽  
Author(s):  
Cyril Dutheil ◽  
Olivier Aumont ◽  
Thomas Gorguès ◽  
Anne Lorrain ◽  
Sophie Bonnet ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Spatial Distribution ◽  
Primary Production ◽  
New Caledonia ◽  
Regional Distribution ◽  
South Pacific ◽  
Tropical Pacific ◽  
Dinitrogen Fixation ◽  
Biogeochemical Model ◽  
Biogeochemical Models

Abstract. Dinitrogen fixation is now recognized as one of the major sources of bio-available nitrogen in the ocean. Thus, nitrogen fixation sustains a significant part of the global primary production by providing an input of the most common limiting nutrient for phytoplankton growth. Evidences of the Western Tropical South Pacific being a hotspot of nitrogen fixation, and a data coverage complemented by OUTPACE, lead us to develop an explicit nitrogen fixation compartment based on the Trichodesmium physiology (the most studied nitrogen fixer) within a 3D coupled dynamical-biogeochemical model (ROMS-PISCES). We performed a first 20-year tropical Pacific simulation that is able to reproduce the main physical (e.g. Sea Surface Temperature) and biogeochemical conditions (nutrients, and chlorophyll concentrations as well as dinitrogen fixation). This simulation showed a possible Trichodesmium regional distribution that extends from 150° E to 120° W in the south tropical Pacific, and from 120° E to 140° W in the north tropical Pacific. The local simulated maximums were around islands (Hawaii, Fiji, Samoa, New Caledonia, Vanuatu). We assessed that 15 % of the total primary production may be due to Trichodesmium in the Low Nutrient, Low Chlorophyll regions (LNLC). We also argue that implicit parameterization of N2 fixation (often used in biogeochemical models) leads to underestimate nitrogen fixation rates by about 25% in LNLC regions compared to our explicit formulation. Finally, we showed that iron fluxes from island sediments control the spatial distribution and the abundance of Trichodesmium in the western tropical south Pacific. Noteworthy, this last result does not take into account the iron supply from rivers and hydrothermal sources, which may well be of importance in a region known for its strong precipitation rates and volcanic activity.

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