Biological Markers for Anoxia in the Photic Zone of the Water Column

2006 ◽  
pp. 127-163 ◽  
Author(s):  
J. S. Sinninghe Damsté ◽  
S. Schouten
Keyword(s):  
Water Column ◽  
Biological Markers ◽  
Photic Zone

scholarly journals Diatoms as a paleoproductivity proxy in the NW Iberian coastal upwelling system (NE Atlantic)

2017 ◽  
Vol 14 (5) ◽  
pp. 1165-1179 ◽  
Author(s):  
Diana Zúñiga ◽  
Celia Santos ◽  
María Froján ◽  
Emilia Salgueiro ◽  
Marta M. Rufino ◽  
...  
Keyword(s):  
Water Column ◽  
Surface Sediment ◽  
Sediment Trap ◽  
Coastal Upwelling ◽  
Late Summer ◽  
Early Summer ◽  
Marine Diatom ◽  
Photic Zone ◽  
Upwelling System ◽  
Water Column Stratification

Abstract. The objective of the current work is to improve our understanding of how water column diatom's abundance and assemblage composition is seasonally transferred from the photic zone to seafloor sediments. To address this, we used a dataset derived from water column, sediment trap and surface sediment samples recovered in the NW Iberian coastal upwelling system. Diatom fluxes (2.2 (±5.6) 106 valves m−2 d−1) represented the majority of the siliceous microorganisms sinking out from the photic zone during all studied years and showed seasonal variability. Contrasting results between water column and sediment trap diatom abundances were found during downwelling periods, as shown by the unexpectedly high diatom export signals when diatom-derived primary production achieved their minimum levels. They were principally related to surface sediment remobilization and intense Minho and Douro river discharge that constitute an additional source of particulate matter to the inner continental shelf. In fact, contributions of allochthonous particles to the sinking material were confirmed by the significant increase of both benthic and freshwater diatoms in the sediment trap assemblage. In contrast, we found that most of the living diatom species blooming during highly productive upwelling periods were dissolved during sinking, and only those resistant to dissolution and the Chaetoceros and Leptocylindrus spp. resting spores were susceptible to being exported and buried. Furthermore, Chaetoceros spp. dominate during spring–early summer, when persistent northerly winds lead to the upwelling of nutrient-rich waters on the shelf, while Leptocylindrus spp. appear associated with late-summer upwelling relaxation, characterized by water column stratification and nutrient depletion. These findings evidence that the contributions of these diatom genera to the sediment's total marine diatom assemblage should allow for the reconstruction of different past upwelling regimes.

scholarly journals Diatoms as paleoproductivity proxy in the NW Iberian coastal upwelling system (NE Atlantic)

2016 ◽  
Author(s):  
Diana Zúñiga ◽  
Celia Santos ◽  
María Froján ◽  
Emilia Salgueiro ◽  
Marta M. Rufino ◽  
...  
Keyword(s):  
Water Column ◽  
Sediment Trap ◽  
Coastal Upwelling ◽  
High Irradiance ◽  
Photic Zone ◽  
Upwelling System ◽  
Water Column Stratification ◽  
Resting Spores ◽  
Seafloor Sediments ◽  
Export Signal

Abstract. The objective of the current work is to better understand how diatoms species determine primary production signal in exported and buried particles. We evaluated how the diatom’s abundance and assemblage composition is transferred from the photic zone into the seafloor sediments. A combined analysis of water column, sediment trap and surface sediment samples recovered in the NW Iberian coastal upwelling system was used. Diatom fluxes (2.2 ± 5.6 106 # valves m−2 d−1) represented the majority of the siliceous microorganisms sinking out from the photic zone and showed strong seasonal variability. During downwelling seasons, diatoms export signal was strongly affected by resuspension of bottom sediments and intense Minho and Douro riverine inputs, with benthic and freshwater diatoms (17–24 %) becoming relevant in the sediment trap assemblage. Nevertheless, during upwelling productive seasons, the diatoms exported out from surface layer reflected water column diatom assemblage. They were principally represented by Chaetoceros spp. (mean 46 ± 25 %) and Leptocylindrus spp. (mean 20 ± 22 %) resting spores, demonstrating that both groups are a good sedimentary imprint during highly productive periods. Moreover, our data showed that the sink of Chaetoceros spp. resting spores dominated under persistent upwelling winds, high irradiance levels and cold and nutrient-rich waters. Otherwise, Leptocylindrus spp. spore fluxes were favoured when northerly winds relax, and surface waters warming promotes water column stratification. Further, this finding will provide a proxy of persistent vs. intermittent upwelling conditions, which is of particular relevance in palaeoceanography.

scholarly journals Fine stratification of microbial communities through a metagenomic profile of the photic zone

2017 ◽  
Author(s):  
Jose M. Haro-Moreno ◽  
Mario López-Pérez ◽  
José R. de la Torre ◽  
Antonio Picazo ◽  
Antonio Camacho ◽  
...  
Keyword(s):  
Community Structure ◽  
Vertical Distribution ◽  
Water Column ◽  
Physicochemical Parameters ◽  
Major Element ◽  
Single Gene ◽  
Single Point ◽  
Photic Zone ◽  
Small Depth ◽  
Sar11 Clade

ABSTRACTMost marine metagenomic studies of the marine photic zone analyze only samples taken at one or two depths. However, when the water column is stratified, physicochemical parameters change dramatically over relatively short depth intervals. We sampled the photic water column every 15m depth at a single point of an off-shore Mediterranean site during a period of strong stratification (early autumn) to evaluate the effects of small depth increases on the microbiome. Using genomic assembly and metagenomic read recruitment, we found major shifts in the community structure over small variations of depth, with most microbes showing a distribution limited to layers approximately 30 meters thick (stenobathic). Only some representatives of the SAR11 clade and the Sphingomonadaceae appeared to be eurybathic, spanning a greater range of depths. These results were confirmed by studying a single gene (rhodopsin) for which we also found narrow depth distributions. Our results highlight the importance of considering vertical distribution as a major element when analyzing the presence of marine clades and species or comparing the microbiome present at different locations.

scholarly journals Impact of the Paleoclimate, Paleoenvironment, and Algae Bloom: Organic Matter Accumulation in the Lacustrine Lucaogou Formation of Jimsar Sag, Junggar Basin, NW China

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1488 ◽  
Author(s):  
Yuhan Jiang ◽  
Dujie Hou ◽  
Hang Li ◽  
Ziming Zhang ◽  
Ruibo Guo
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Water Column ◽  
Shale Oil ◽  
Photic Zone ◽  
Sweet Spot ◽  
Algae Bloom ◽  
Organic Matter Accumulation ◽  
Lucaogou Formation ◽  
Water Stratification

Shale oil exploration has been a key area of onshore oil and gas exploration in China in recent years. In this study, organic geochemistry and element geochemistry are united to study the shale oil and source rock in the Lucaogou formation of Jimusar sag, in order to reveal the paleoclimate, paleoenvironment, source of organic matter, and factors affecting organic matter accumulation and shale oil generation. The shale oil in the study area is mainly accumulated in two strata with good reservoir properties and oiliness, known as the upper sweet spot and lower sweet spot. Indexes of biomarkers and sensitive elements revealed the warm and semi-arid paleoclimate during Lucaogou formation, and the water column was brackish to salty. Water stratification caused a suboxic to anoxic environment in the deep-water column and coincided with the anoxic photic zone phenomenon. Compared with the lower sweet spot, the more humid climate, deeper and fresher water, and stronger water stratification characterize the upper sweet spot during sedimentation. This made the photic zone with freshwater more suitable for the reproduction of algae in the upper sweet spot. Meanwhile, the organic matter was well-preserved in the anoxic zone. Volcanic ash caused algae bloom, which promoted primary productivity and ensured the supply of organic matter. The composition and distribution pattern of biomarkers prove that phytoplankton is the most important source of organic matter in the study area and the contribution of higher plants is insignificant. The relationship between parameters of paleoproductivity and the redox condition versus total organic carbon (TOC) suggests that compared with the preservation conditions, the input of organic carbon is the most important controlling factor of organic matter accumulation in the study area.

scholarly journals Spatial distribution of living coccolithophores in the southwestern Gulf of Mexico

2013 ◽  
Vol 32 (2) ◽  
pp. 123-133 ◽  
Author(s):  
Karl-Heinz Baumann ◽  
Babette Boeckel
Keyword(s):  
Gulf Of Mexico ◽  
Water Column ◽  
Light Availability ◽  
Minor Component ◽  
Abundant Species ◽  
Intermediate Water ◽  
Photic Zone ◽  
Type Iv ◽  
Florisphaera Profunda ◽  
Living Coccolithophores

Abstract. The present study was conducted to provide information about the upper water column distribution of living coccolithophores in the subtropical Gulf of Mexico. In total, 52 plankton samples from 6 stations collected in March 2006 were analysed. Coccolithophore standing crops range from zero in deep-water samples (200 m) to about 23 000 to 46 500 coccospheres per litre at intermediate water depths. From 39 identified taxa, only nine species contribute significant cell numbers of more than 1000 cells 1–1 and comprise more than 5 % of the communities in at least one sample. Emiliania huxleyi was the most abundant species throughout the stations with concentrations of up to 22 700 cells l–1. At all stations, a vertical succession of coccolithophore species was found. Umbellosphaera tenuis (type IV), Discosphaera tubifera, Rhabdosphaera clavigera and, as a minor component, species of the genus Syracosphaera, were mainly restricted to surface waters (≤50 m), all adapted to lower nutrient levels. The assemblage in the deep photic zone (50–150 m water depth) was composed mainly of abundant Florisphaera profunda, Gladiolithus flabellatus and Algirosphaera robusta indicating a tolerance of lower light availability. Thus, the vertical distribution of all coccolithophorid taxa, except the placolith-bearing species, in particular E. huxleyi, was probably controlled by upper photic-zone water temperature and stratification of the water column.

Extreme self-sacrifice beyond fusion: Moral expansiveness and the special case of allyship

2018 ◽  
Vol 41 ◽  
Author(s):  
Daniel Crimston ◽  
Matthew J. Hornsey
Keyword(s):  
General Theory ◽  
Biological Markers ◽  
Natural Environment ◽  
Relevant Dimension ◽  
Special Case

AbstractAs a general theory of extreme self-sacrifice, Whitehouse's article misses one relevant dimension: people's willingness to fight and die in support of entities not bound by biological markers or ancestral kinship (allyship). We discuss research on moral expansiveness, which highlights individuals’ capacity to self-sacrifice for targets that lie outside traditional in-group markers, including racial out-groups, animals, and the natural environment.

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