scholarly journals The impact of postdepositional alteration on iron- and molybdenum-based redox proxies

Geology ◽  
2021 ◽  
Author(s):  
Suemeyya Eroglu ◽  
Florian Scholz ◽  
Renato Salvatteci ◽  
Christopher Siebert ◽  
Ralph Schneider ◽  
...  
Keyword(s):  
Sulfate Reduction ◽  
Gulf Of California ◽  
Molybdenum Isotope ◽  
Redox States ◽  
Reactive Iron ◽  
Sheet Silicates ◽  
Fe Speciation ◽  
Minimum Zone ◽  
The Impact ◽  
Oxygen Minimum

Ratios of (un)reactive iron species, authigenic molybdenum contents (Moauth), and molybdenum isotope compositions (δ98Moauth) in sedimentary rocks are geochemical proxies that are widely used to reconstruct past marine redox states, which have been calibrated in modern marine settings covering oxic to euxinic conditions. However, syn- and postdepositional processes can result in alterations and ambiguities of proxy-derived redox signals that can challenge the validity of paleoreconstructions. We present new data from modern organic-rich sediments of two oxygen minimum zone settings in the Gulf of California and the Peruvian margin. The results show that Mo is fully immobilized shortly after deposition by reaction with hydrogen sulfide (H2S) produced during organoclastic sulfate reduction. Thus, any H2S produced deeper in the sediment (e.g., by sulfate reduction coupled to anaerobic methane oxidation) leaves the initially deposited Mo concentrations and δ98Mo signatures unaltered, which supports the robustness of Mo-based redox proxies. In contrast, the Fe speciation data reveal continued pyritization due to constant exposure of Fe minerals to H2S. Importantly, both Fe bound to oxides and carbonates (highly reactive Fe) and also poorly reactive Fe (e.g., sheet silicates) undergo pyritization during early diagenesis. This process generates Fe-based proxy signatures that falsely imply ferruginous or euxinic conditions.

scholarly journals Zooplankton diel vertical migration and downward C flux into the oxygen minimum zone in the highly productive upwelling region off northern Chile

2020 ◽  
Vol 17 (2) ◽  
pp. 455-473 ◽  
Author(s):  
Pritha Tutasi ◽  
Ruben Escribano
Keyword(s):  
Vertical Migration ◽  
Diel Vertical Migration ◽  
Net Primary Production ◽  
Oxygen Minimum Zone ◽  
Zooplankton Biomass ◽  
Taxonomic Structure ◽  
Northern Chile ◽  
Minimum Zone ◽  
The Impact ◽  
Oxygen Minimum

Abstract. Diel vertical migration (DVM) can enhance the vertical flux of carbon (C), and so contributes to the functioning of the biological pump in the ocean. The magnitude and efficiency of this active transport of C may depend on the size and taxonomic structure of the migrant zooplankton. However, the impact that a variable community structure can have on zooplankton-mediated downward C flux has not been properly addressed. This taxonomic effect may become critically important in highly productive eastern boundary upwelling systems (EBUSs), where high levels of zooplankton biomass are found in the coastal zone and are composed by a diverse community with variable DVM behavior. In these systems, presence of a subsurface oxygen minimum zone (OMZ) can impose an additional constraint to vertical migration and so influence the downward C export. Here, we address these issues based on a vertically stratified zooplankton sampling at three stations off northern Chile (20–30∘ S) during November–December 2015. Automated analysis of zooplankton composition and taxa-structured biomass allowed us to estimate daily migrant biomass by taxa and their amplitude of migration. We found that a higher biomass aggregates above the oxycline, associated with more oxygenated surface waters and this was more evident upon a more intense OMZ. Some taxonomic groups, however, were found closely associated with the OMZ. Most taxa were able to perform DVM in the upwelling zone withstanding severe hypoxia. Also, strong migrants, such as eucalanid copepods and euphausiids, can exhibit a large migration amplitude (∼500 m), remaining either temporarily or permanently within the core of the OMZ and thus contributing to the release of C below the thermocline. Our estimates of DVM-mediated C flux suggested that a mean migrant biomass of ca. 958 mg C m−2 d−1 may contribute with about 71.3 mg C m−2 d−1 to the OMZ system through respiration, mortality and C excretion at depth, accounting for ca. 4 % of the net primary production, and so implies the existence of an efficient mechanism to incorporate freshly produced C into the OMZ. This downward C flux mediated by zooplankton is however spatially variable and mostly dependent on the taxonomic structure due to variable migration amplitude and DVM behavior.

Effects of the oxygen minimum zone on squat lobster distributions in the Gulf of California, Mexico

2014 ◽  
Vol 9 (1) ◽  
pp. 92-103 ◽  
Author(s):  
Michel Hendrickx ◽  
David Serrano
Keyword(s):  
Gulf Of California ◽  
Oxygen Minimum Zone ◽  
Long Distance ◽  
Sampling Locations ◽  
Minimum Zone ◽  
Shallow Area ◽  
Bottom Oxygen ◽  
Lower Limits ◽  
Squat Lobsters ◽  
Oxygen Minimum

AbstractDistribution of squat lobsters of the genera Gastropthychus (one species), Uroptychus (1), Janetogalathea (1), Galacantha (1), Munidopsis (8), and Munida (7) in the Gulf of California, Mexico, was plotted vs. the localization of the Oxygen Minimum Zone (OMZ) using bottom projections of the 0.50, 0.25, 0.10, and 0.05 ml l−1 oxylines. Four fringes where oxygen concentrations were equal or lower than these concentrations were obtained, extending from the southern Gulf to about 28°–28°30′N. A total of 172 sampling locations with squat lobsters were plotted on four maps, one for each fringe, noting that with decreasing values of bottom oxygen (i.e., from 0.50 to 0.05 ml l−1) the number of locations with species included between the upper and lower boundaries of these fringes decreases as follows: 34% for 0.50, 25% for 0.25, 12% for 0.10, and 5% for 0.05 ml l−1. The upper and lower limits of the 0.05 ml l−1 fringe are recognised as threshold frontiers, acting as barriers between shallow and deep communities of squat lobsters in the area. The distribution of the localities where species have been collected with respect to the upper and lower boundaries of the 0.05 ml l−1 fringe clearly indicates a segregation pattern. Eight species of Munida (except M. perlata), and one each of Janetogalathea and Gastropthychus inhabit the shallow area, just above the OMZ core, with species of Munida generally found a rather long distance from this fringe. By contrast, species of Munidopsis, G. diomedeae and U. pubescens correspond to the deep area, i.e., below the OMZ core. It is suggested that the core of the OMZ in the Gulf of California serves as a vertical and latitudinal distribution filter, preventing species from freely migrating up and down or south and north.

scholarly journals Differential Distribution and Determinants of Ammonia Oxidizing Archaea Sublineages in the Oxygen Minimum Zone off Costa Rica

2019 ◽  
Vol 7 (10) ◽  
pp. 453 ◽  
Author(s):  
Yanhong Lu ◽  
Xiaomin Xia ◽  
Shunyan Cheung ◽  
Hongmei Jing ◽  
Hongbin Liu
Keyword(s):  
Costa Rica ◽  
Water Column ◽  
Gulf Of California ◽  
North Pacific Ocean ◽  
Oxygen Minimum Zone ◽  
Low Oxygen ◽  
Environmental Determinants ◽  
Ammonia Oxidizing Archaea ◽  
Minimum Zone ◽  
Oxygen Minimum

Ammonia oxidizing archaea (AOA) are microbes that are widely distributed in the ocean that convert ammonia to nitrite for energy acquisition in the presence of oxygen. Recent study has unraveled highly diverse sublineages within the previously defined AOA ecotypes (i.e., water column A (WCA) and water column B (WCB)), although the eco-physiology and environmental determinants of WCB subclades remain largely unclear. In this study, we examined the AOA communities along the water columns (40–3000 m depth) in the Costa Rica Dome (CRD) upwelling region in the eastern tropical North Pacific Ocean. Highly diverse AOA communities that were significantly different from those in oxygenated water layers were observed in the core layer of the oxygen minimum zone (OMZ), where the dissolved oxygen (DO) concentration was < 2μM. Moreover, a number of AOA phylotypes were found to be enriched in the OMZ core. Most of them were negatively correlated with DO and were also detected in other OMZs in the Arabian Sea and Gulf of California, which suggests low oxygen adaptation. This study provided the first insight into the differential niche partitioning and environmental determinants of various subclades within the ecotype WCB. Our results indicated that the ecotype WCB did indeed consist of various sublineages with different eco-physiologies, which should be further explored.

scholarly journals New species of the genus Mesocletodes Sars, 1909 from the deep Gulf of California (Copepoda, Harpacticoida)

ZooKeys ◽  
2018 ◽  
Vol 751 ◽  
pp. 75-112 ◽  
Author(s):  
Samuel Gómez
Keyword(s):  
New Species ◽  
Deep Sea ◽  
Gulf Of California ◽  
Tropical Pacific ◽  
Eastern Tropical Pacific ◽  
Minimum Zone ◽  
Species Groups ◽  
Three New Species ◽  
Abundance And Diversity ◽  
Oxygen Minimum

Investigations on the effects of the oxygen minimum zone on the distribution, abundance, and diversity of deep-sea benthic and pelagic fauna of the Gulf of California and Eastern Tropical Pacific has received attention recently. However, very little is known about the diversity of deep-sea benthic harpacticoids from this region, and only three species,AncorabolushendrickxiGómez &amp; Conroy-Dalton, 2002,CeratonotuselongatusGómez &amp; Díaz, 2017 andDendropsylluscaliforniensisGómez &amp; Díaz, 2017, have been described so far. The genusMesocletodesSars, 1909 is one of the most common and abundant genera of deep-sea harpacticoids. This genus has been traditionally subdivided into two species groups, theabyssicolaand theinermisgroups, based on the presence/absence of a dorsal cuticular process on the cephalothorax and anal somite, but some species have been reported to deviate from this scheme. As a result of their investigations, other researchers proposed the monophyly of theabyssicolagroup, and suggested the probable monophyly of two other species-groups. In this paper, the descriptions of three new species of the genusMesocletodesfrom the deep sea of the Gulf of California are presented with some notes on their relationships with other species. Some comments on the monophyly of the genus are given.

scholarly journals Zooplankton diel vertical migration and downward C into the Oxygen Minimum Zone in the highly productive upwelling region off Northern Chile

2019 ◽  
Author(s):  
Pritha Tutasi ◽  
Ruben Escribano
Keyword(s):  
Community Structure ◽  
Vertical Migration ◽  
Diel Vertical Migration ◽  
Oxygen Minimum Zone ◽  
Taxonomic Structure ◽  
Northern Chile ◽  
Daily Rate ◽  
Minimum Zone ◽  
The Impact ◽  
Oxygen Minimum

Abstract. The daily vertical movement of zooplankton, known as diel vertical migration (DVM), can enhance the vertical flux of carbon (C) and so contributing to the functioning of the biological pump. The magnitude and efficiency of this active transport of C may depend on the size and taxonomic structure of the migrant zooplankton. However, the impact that a variable community structure can have on zooplankton-mediated downward C has not been properly addressed. This taxonomic effect may become critically important in highly productive eastern boundary upwelling systems (EBUS), where zooplankton biomass becomes aggregated in the coastal zone, but comprised by a highly variable community structure (size-composition). In these systems, presence of a subsurface oxygen minimum zone (OMZ) can impose an additional constraint to vertical migration and so influencing the downward C export. Here, we address these issues based on a high-resolution zooplankton sampling at three stations off northern Chile (20°S−30°S) during November 2015. Automated analysis of zooplankton composition and taxa-structured biomass allowed us to estimate daily migrant biomass by taxa, amplitude of migration and daily rate of migration, defined as the daily exchange of biomass between the upper mixed layer and below the thermocline. We found that high biomass aggregates above the oxycline, associated with more oxygenated surface waters and this condition was more evident upon a more intense OMZ. Some taxa however, were found closely associated with the OMZ. We found that most taxa were able to perform DVM in the upwelling zone withstanding severe hypoxia. Even, several strong migrants, such as copepods Eucalanidae and Euphausiids, can exhibit a large migration amplitude (~500 m), remaining either temporarily or permanently during the day or night condition within the core of the OMZ and so contributing to the release of C below the thermocline. Our estimates of DVM-mediated C flux showed that migrant biomass (5099 ± 2701 mg C m−2d−1) may contribute with about 678 ± 465 mg C m−2d−1 to the OMZ system through respiration, mortality, and production of fecal pellets, implying the existence of a very efficient mechanism to incorporate freshly produced C into the OMZ. This downward C by zooplankton is however strongly depending on taxonomic structure due to variable migration amplitude and behavior affecting the daily rate of diel vertical migration.

scholarly journals Bioaccumulation of Trace Elements in Myctophids in the Oxygen Minimum Zone Ecosystem of the Gulf of California

Oceans ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 34-46
Author(s):  
Cátia Figueiredo ◽  
Miguel Baptista ◽  
Tiago Grilo ◽  
Miguel Caetano ◽  
Unai Markaida ◽  
...  
Keyword(s):  
Trace Element ◽  
Gulf Of California ◽  
Trace Element Content ◽  
Oxygen Minimum Zone ◽  
Trophic Levels ◽  
Diel Vertical Migrations ◽  
Trace Elemental ◽  
Minimum Zone ◽  
Element Transfer ◽  
Oxygen Minimum

Myctophids are key members of mesopelagic communities with a world biomass estimated at 600 million tons. They play a central role in oceanic food webs and are known to perform diel vertical migrations, crossing the thermocline and reaching the oxygen minimum zone, however, very scarce information exists on trace element content in these organisms. Therefore, the trace elemental composition (Cr, Mn, Co, Ni, Cu, Zn, As, Se, Cd and Pb) of Triphoturus mexicanus and Benthosema panamense specimens was determined. Zinc (Zn) was the most common trace element for both species, T. mexicanus presented 39.8 µg.g−1 dw and B. panamense 30.6 µg.g−1 dw. Contrasting, for T. mexicanus the less abundant trace element was Ni (0.332 µg.g−1 dw) and for B. panamense was Pb (0.236 µg.g−1 dw). T. mexicanus exhibited significantly higher concentrations of Cr, Cu, Zn and Pb in comparison to B. panamense, and these differences seemed to be related to inherent physiological and/or ecological traits rather than environmental element availability. These diel vertical migrators are crucial in the energy transfer between the deep-sea and epipelagic zones (and vice-versa), and the estimation of the Biomagnification Factor (based on Cu, Zn, Cd and Pb) levels revealed that both T. mexicanus and B. panamense play a major role in trace element transfer to higher trophic levels in the pelagic food web of the Gulf of California.

scholarly journals Distribution of the deep-sea genus Bathypterois (Pisces: Ipnopidae) in the Eastern Central Pacific

2016 ◽  
Vol 65 (1) ◽  
pp. 89 ◽  
Author(s):  
Edgar Cruz-Acevedo ◽  
Miguel Betancourt-Lozano ◽  
Hugo Aguirre-Villaseñor
Keyword(s):  
Deep Sea ◽  
Gulf Of California ◽  
Depth Distribution ◽  
Continuous Distribution ◽  
Niche Overlap ◽  
Limiting Factor ◽  
Central Pacific ◽  
Mexican Pacific ◽  
Minimum Zone ◽  
Oxygen Minimum

The genus Bathypterois (tripod fish) comprises 19 species of deep-sea fishes distributed worldwide. The biology and distribution of the species of this genus are relatively poorly known throughout the Eastern Central Pacific (ECP). This work aims to update the geographic and bathymetric distribution of species of Bathypterois throughout the ECP. To describe the influence of depth, temperature and dissolved oxygen concentrations (DO) on latitudinal and depth distribution of members of the genus throughout the Mexican Pacific, 51 specimens of B. atricolor (12 trawls) and 112 of B. ventralis (18 trawls), collected during TALUD project, were analyzed. Bathypterois atricolor had broader environmental niches (depth: 0.47, temperature: 0.46, DO: 0.39), and inhabits deeper and colder sites (Electivity positives: > 1 000 m, < 3.2 °C, 1.0-1.62 mL/L) than B. ventralis, which had narrow environmental niches (depth: 0.34, temperature: 0.32, DO: 0.28), with high affinity to warmer sites and lower DO concentrations (Electivity positives: 778-1 400 m, 3.3-5.8 °C, < 1.0 mL/L). Both species used different environmental strata (niche overlap; depth: 0.34, temperature: 0.32, DO: 0.28). The adaptation of B. atricolor to live in a broad range of DO concentrations explains its almost circumglobal distribution, while B. ventralis lives almost permanently in the Oxygen Minimum Zone (< 0.05 mL/L), so the DO could be a limiting factor, reducing its potential geographic and bathymetric distributions. None of these species had been previously recorded in the central Gulf of California, and B. ventralis had not been recorded along the West coast of Baja California. This study confirms that both species have a continuous distribution within the ECP, our new records extended the known northernmost range for B. atricolor by 886 km (from 22°46' N to 30°45’ N) and for B. ventralis by 645 km (from 21°18’ N to 27°07’ N).

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