Search results for "Underwater"

Distribution and sources of bulk organic matter (OM) on a tropical intertidal mud bank in French Guiana from elemental and isotopic proxies

2014

International audience; The mobile French Guiana coast is a shoreface region downdrift of the Amazon River, where enormous quantities of inorganic and organic materials are exchanged with the Atlantic Ocean. The rapid accumulation of these materials forms highly unstable shore-attached mud banks, which can be temporally emerged and then rapidly colonized and stabilized by microphytobenthos and opportunistic mangroves (i.e. Avicennia germinans). Mud banks are preferential sites for the accumulation and significant remineralization of organic matter (OM) due to intense erosion/deposition cycles and potential biological colonization. The distribution and sources of bulk sedimentary OM were cha…

Could the acid-base status of Antarctic sea urchins indicate a better-than-expected resilience to near-future ocean acidification?

2015

13 pages; International audience; Increasing atmospheric carbon dioxide concentration alters the chemistry of the oceans towards more acidic conditions. Polar oceans are particularly affected due to their low temperature, low carbonate content and mixing patterns, for instance upwellings. Calcifying organisms are expected to be highly impacted by the decrease in the oceans' pH and carbonate ions concentration. In particular, sea urchins, members of the phylum Echinodermata, are hypothesized to be at risk due to their high-magnesium calcite skeleton. However, tolerance to ocean acidification in metazoans is first linked to acid–base regulation capacities of the extracellular fluids. No infor…

Ecology and extent of freshwater browning - What we know and what should be studied next in the context of global change

2022

Water browning or brownification refers to increasing water color, often related to increasing dissolved organic matter (DOM) and carbon (DOC) content in freshwaters. Browning has been recognized as a significant physicochemical phenomenon altering boreal lakes, but our understanding of its ecological consequences in different freshwater habitats and regions is limited. Here, we review the consequences of browning on different freshwater habitats, food webs and aquatic-terrestrial habitat coupling. We examine global trends of browning and DOM/DOC, and the use of remote sensing as a tool to investigate browning from local to global scales. Studies have focused on lakes and rivers while seldo…

A Low Cost Customizable Micro-ROV for Environmental Research - Applications, Advances and Challenges

2016

Summary Several shallow submarines areas are characterized by considerable releases of hydrocarbon gases, which, during earthquakes or volcanic activity, may suddenly and violently occur. In some instances, changes in chemical and physical properties of gas emissions, which are generated by geothermal systems connected to the volcanoes’ plumbing system, are important precursors of volcanic activity and useful indices for the study of the geothermal field. Furthermore, some superficial structures such faults, landslide slopes or archaeological relics should be studied with such a high detail that geophysical and bathymetric surveys are unable to provide. In response to the needs increasingly…

Coupling two radar backscattering models to assess soil roughness and surface water content at farm scale

2013

Remote sensing techniques are useful for agro-hydrological monitoring at the farm scale because the availability of spatially and temporally distributed data improves agricultural models for irrigation and crop yield optimization under water scarcity conditions. This research focuses on the surface water content retrieval using active microwave data. Two semi-empirical models were chosen as these showed the best performances in simulating cross and co-polarized backscatter. Thus, these models were coupled to obtain reliable assessments of both soil water content and soil roughness. The use of the coupled model enables one to avoid using roughness measured in situ. Remote sensing images and …

Early Paleocene Paleoceanography and Export Productivity in the Chicxulub Crater

2021

The Chicxulub impact caused a crash in productivity in the world''s oceans which contributed to the extinction of ~75% of marine species. In the immediate aftermath of the extinction, export productivity was locally highly variable, with some sites, including the Chicxulub crater, recording elevated export production. The long-term transition back to more stable export productivity regimes has been poorly documented. Here, we present elemental abundances, foraminifer and calcareous nannoplankton assemblage counts, total organic carbon, and bulk carbonate carbon isotope data from the Chicxulub crater to reconstruct changes in export productivity during the first 3 Myr of the Paleocene. We sh…

Species diversity of the deep-water gulper sharks (Squaliformes: Centrophoridae:Centrophorus) in North Atlantic waters - current status and taxonomic…

2014

The gulper sharks (genus Centrophorus) are a group of deep-water benthopelagic sharks with a worldwide dis- tribution. The alpha taxonomy of the group has historically been problematic and the number of species included in the genus has varied considerably over the years and is still under debate. Gulper sharks are routinely caught in mid- and deep-water fisheries worldwide and some have shown a considerable decline in abundance in the last few decades. Clear and consistent species discrimination of Centrophorus is essential for an efficient and sustain- able management of these fisheries resources. Our study used molecular cytochrome oxidase subunit I (COI) and 16S ribosomal RNA gene seque…

Corrigendum to “Uncovering deep mysteries: The underwater life of an amphibious louse” [Journal of Insect Physiology 71 (2014) 164–169]

2015

A new calibration of the effective scattering albedo and soil roughness parameters in the SMOS SM retrieval algorithm

2017

Abstract This study focuses on the calibration of the effective vegetation scattering albedo (ω) and surface soil roughness parameters (H R , and N Rp , p = H,V) in the Soil Moisture (SM) retrieval from L-band passive microwave observations using the L-band Microwave Emission of the Biosphere (L-MEB) model. In the current Soil Moisture and Ocean Salinity (SMOS) Level 2 (L2), v620, and Level 3 (L3), v300, SM retrieval algorithms, low vegetated areas are parameterized by ω = 0 and H R  = 0.1, whereas values of ω = 0.06 − 0.08 and H R  = 0.3 are used for forests. Several parameterizations of the vegetation and soil roughness parameters (ω, H R and N Rp , p = H,V) were tested in this study, tre…

The Aquatic Surface Robot (AnSweR), a Lightweight, Low Cost, Multipurpose Unmanned Research Vessel

2021

Even though a few examples of aquatic surface robots exist, they are generally expensive, relatively large and heavy and tailored to custom-made hardware/software components that are not openly available to a broad public. In this work, the Aquatic Surface Robot (AnSweR), a newly-designed, lightweight, low cost, open-source, multipurpose unmanned research vessel is presented. The AnSweR features a lightweight and compact design that makes it fit in a backpack. Low-noise operation (in and above the surface) is achieved with a propulsion system based on two water-jets. Only affordable commercial-off-the-shelf (COTS) components are adopted. The primary goal of the AnSweR is to map underwater l…