scholarly journals The cyanobacterium Prochlorococcus has divergent light-harvesting antennae and may have evolved in a low-oxygen ocean

2021 ◽  
Vol 118 (11) ◽  
pp. e2025638118
Author(s):  
Osvaldo Ulloa ◽  
Carlos Henríquez-Castillo ◽  
Salvador Ramírez-Flandes ◽  
Alvaro M. Plominsky ◽  
Alejandro A. Murillo ◽  
...  
Keyword(s):  
Light Harvesting ◽  
Low Oxygen ◽  
South Pacific Ocean ◽  
Anoxic Waters ◽  
Coastal Marine ◽  
Elemental Cycling ◽  
Oxygen Conditions ◽  
Pigment Biosynthesis ◽  
Phylogenetic Lineages ◽  
Light Harvesting Antenna

Marine picocyanobacteria of the genus Prochlorococcus are the most abundant photosynthetic organisms in the modern ocean, where they exert a profound influence on elemental cycling and energy flow. The use of transmembrane chlorophyll complexes instead of phycobilisomes as light-harvesting antennae is considered a defining attribute of Prochlorococcus. Its ecology and evolution are understood in terms of light, temperature, and nutrients. Here, we report single-cell genomic information on previously uncharacterized phylogenetic lineages of this genus from nutrient-rich anoxic waters of the eastern tropical North and South Pacific Ocean. The most basal lineages exhibit optical and genotypic properties of phycobilisome-containing cyanobacteria, indicating that the characteristic light-harvesting antenna of the group is not an ancestral attribute. Additionally, we found that all the indigenous lineages analyzed encode genes for pigment biosynthesis under oxygen-limited conditions, a trait shared with other freshwater and coastal marine cyanobacteria. Our findings thus suggest that Prochlorococcus diverged from other cyanobacteria under low-oxygen conditions before transitioning from phycobilisomes to transmembrane chlorophyll complexes and may have contributed to the oxidation of the ancient ocean.

scholarly journals Vertical migration patterns of the different larval instars of Chaoborus flavicans and the influence of dissolved oxygen concentrations

2018 ◽  
Vol 75 (7) ◽  
pp. 1142-1150
Author(s):  
Manuel Weisser ◽  
Hilmar Hofmann ◽  
Jorge Encinas Fernández ◽  
Frank Peeters
Keyword(s):  
Dissolved Oxygen ◽  
Vertical Distribution ◽  
Vertical Migration ◽  
Low Oxygen ◽  
Migration Patterns ◽  
Larval Instars ◽  
Larval Stages ◽  
Chaoborus Flavicans ◽  
Anoxic Waters ◽  
Oxygen Conditions

Here we investigate the diel vertical migration (DVM) of the different larval stages of Chaoborus flavicans between spring and summer in two different lakes and three different years. Specific attention is given to the influence of the vertical distribution of dissolved oxygen (DO) on the DVM of the different larval instars. To our knowledge, this study is the first that combines continuous observations of DVM of C. flavicans with continuous measurements of DO distributions over several months, allowing the assessment of changes in DVM due to the development of hyperoxic conditions in the deep water of lakes. With ontogenetic development, C. flavicans larvae increase their sensitivity to changes in light intensity and their tolerance to low oxygen conditions. Our results suggest that the physiological changes of C. flavicans larvae are adaptations to seasonal changes in DO, improving migration abilities to enable utilization of hypoxic and anoxic waters to avoid predation. Interannual change in the abundance and vertical distribution of phytoplankton affecting DO concentrations was sufficient to alter DVM patterns of C. flavicans larvae between years.

scholarly journals Benthic phosphorus cycling in the Peruvian oxygen minimum zone

2016 ◽  
Vol 13 (5) ◽  
pp. 1367-1386 ◽  
Author(s):  
Ulrike Lomnitz ◽  
Stefan Sommer ◽  
Andrew W. Dale ◽  
Carolin R. Löscher ◽  
Anna Noffke ◽  
...  
Keyword(s):  
Water Column ◽  
Surface Sediments ◽  
Solid Phase ◽  
Continental Margins ◽  
Low Oxygen ◽  
Anoxic Waters ◽  
Oxygen Conditions ◽  
Bottom Waters ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. Oxygen minimum zones (OMZs) that impinge on continental margins favor the release of phosphorus (P) from the sediments to the water column, enhancing primary productivity and the maintenance or expansion of low-oxygen waters. A comprehensive field program in the Peruvian OMZ was undertaken to identify the sources of benthic P at six stations, including the analysis of particles from the water column, surface sediments, and pore fluids, as well as in situ benthic flux measurements. A major fraction of solid-phase P was bound as particulate inorganic P (PIP) both in the water column and in sediments. Sedimentary PIP increased with depth in the sediment at the expense of particulate organic P (POP). The ratio of particulate organic carbon (POC) to POP exceeded the Redfield ratio both in the water column (202 ± 29) and in surface sediments (303 ± 77). However, the POC to total particulate P (TPP = POP + PIP) ratio was close to Redfield in the water column (103 ± 9) and in sediment samples (102 ± 15). This suggests that the relative burial efficiencies of POC and TPP are similar under low-oxygen conditions and that the sediments underlying the anoxic waters on the Peru margin are not depleted in P compared to Redfield. Benthic fluxes of dissolved P were extremely high (up to 1.04 ± 0.31 mmol m−2 d−1), however, showing that a lack of oxygen promotes the intensified release of dissolved P from sediments, whilst preserving the POC / TPP burial ratio. Benthic dissolved P fluxes were always higher than the TPP rain rate to the seabed, which is proposed to be caused by transient P release by bacterial mats that had stored P during previous periods when bottom waters were less reducing. At one station located at the lower rim of the OMZ, dissolved P was taken up by the sediments, indicating ongoing phosphorite formation. This is further supported by decreasing porewater phosphate concentrations with sediment depth, whereas solid-phase P concentrations were comparatively high.

Sedimentary trace metals: improving proxies for deoxygenation in coastal European seas

2021 ◽  
Author(s):  
Mareike Paul ◽  
Niels A. G. M. van Helmond ◽  
Caroline P. Slomp ◽  
Sami A. Jokinen ◽  
Joonas J. Virtasalo ◽  
...  
Keyword(s):  
Trace Metals ◽  
Trace Metal ◽  
Bottom Water ◽  
Depositional Environments ◽  
Coastal Zones ◽  
Low Oxygen ◽  
Coastal Marine ◽  
Oxygen Conditions ◽  
History Of ◽  
Metal Redox

<p>Deoxygenation in response to eutrophication and climate change in coastal systems is increasing worldwide. Low oxygen conditions cause the chemical transformation of redox-sensitive trace metals (e.g. molybdenum and uranium) in seawater, and their subsequent transport to the sediment. Sedimentary trace metal contents can therefore be used as a record of changes in bottom water oxygen conditions allowing the history of deoxygenation to be reconstructed. However, most trace metal studies have focused on strongly reducing and sulfidic settings, leaving mildly reducing and oxygenated (but eutrophic) settings vastly understudied. Currently, it is unknown to what extent existing trace metal redox proxies are applicable to reconstruct oxygen conditions in coastal zones experiencing mild deoxygenation, despite the fact that such areas occupy vast stretches of the coastal oceans. Here, we study trace metal enrichments in 13 European coastal marine sites with varying bottom water redox conditions and depositional environments. Our data demonstrates that sedimentary molybdenum and uranium contents are sensitive to deoxygenation across a range of settings, although the mechanisms of enrichment may vary. Improved understanding of molybdenum and uranium dynamics in mildly reducing coastal settings will facilitate the development of reliable and widely applicable molybdenum and uranium-based redox proxies.</p>

scholarly journals Identification and Functional Analysis of ThADH1 and ThADH4 Genes Involved in Tolerance to Waterlogging Stress in Taxodium hybrid ‘Zhongshanshan 406’

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 225
Author(s):  
Lei Xuan ◽  
Jianfeng Hua ◽  
Fan Zhang ◽  
Zhiquan Wang ◽  
Xiaoxiao Pei ◽  
...  
Keyword(s):  
Ethanol Metabolism ◽  
Flooding Tolerance ◽  
Transcriptome Data ◽  
Low Oxygen ◽  
Anaerobic Conditions ◽  
Waterlogging Tolerance ◽  
Waterlogging Stress ◽  
Adh Genes ◽  
Oxygen Conditions ◽  
Stems And Leaves

The Taxodium hybrid ‘Zhongshanshan 406’ (T. hybrid ‘Zhongshanshan 406’) [Taxodium mucronatum Tenore × Taxodium distichum (L.). Rich] has an outstanding advantage in flooding tolerance and thus has been widely used in wetland afforestation in China. Alcohol dehydrogenase genes (ADHs) played key roles in ethanol metabolism to maintain energy supply for plants in low-oxygen conditions. Two ADH genes were isolated and characterized—ThADH1 and ThADH4 (GenBank ID: AWL83216 and AWL83217—basing on the transcriptome data of T. hybrid ‘Zhongshanshan 406’ grown under waterlogging stress. Then the functions of these two genes were investigated through transient expression and overexpression. The results showed that the ThADH1 and ThADH4 proteins both fall under ADH III subfamily. ThADH1 was localized in the cytoplasm and nucleus, whereas ThADH4 was only localized in the cytoplasm. The expression of the two genes was stimulated by waterlogging and the expression level in roots was significantly higher than those in stems and leaves. The respective overexpression of ThADH1 and ThADH4 in Populus caused the opposite phenotype, while waterlogging tolerance of the two transgenic Populus significantly improved. Collectively, these results indicated that genes ThADH1 and ThADH4 were involved in the tolerance and adaptation to anaerobic conditions in T. hybrid ‘Zhongshanshan 406’.

Pilot-scale production of cloudy juice from low-quality pear fruit under low-oxygen conditions

2015 ◽  
Vol 173 ◽  
pp. 827-837 ◽  
Author(s):  
Domien De Paepe ◽  
Katleen Coudijzer ◽  
Bart Noten ◽  
Dirk Valkenborg ◽  
Kelly Servaes ◽  
...  
Keyword(s):  
Pilot Scale ◽  
Scale Production ◽  
Low Oxygen ◽  
Pear Fruit ◽  
Pilot Scale Production ◽  
Oxygen Conditions
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