News
Preprint: Reviews and synthesis: increasing hypoxia in eastern boundary upwelling systems: a major stressor for zooplankton
Abstract.
"Eastern boundary upwelling systems (EBUS) are ecologically and economically important marine regions of the world ocean. In these systems, zooplankton play a pivotal role in transferring primary production up through the food web. Recent studies show that global warming is causing a gradual deoxygenation of the world ocean, while in EBUS a vertical expansion of the subsurface oxygen minimum zone (OMZ) along with increased wind-driven upwelling are taking place, further exacerbating hypoxic conditions for zooplankton inhabiting the upwelling zone. Hypoxia can affect zooplankton by disrupting their respiration, migration, reproduction, and development. [...]".
Source: EGUsphere
Authors: Leissing Frederick et al.
DOI: https://doi.org/10.5194/egusphere-2024-836
Preprint: The influence of zooplankton and oxygen on the particulate organic carbon flux in the Benguela Upwelling System
Abstract.
"We conducted extensive sediment trap experiments in the Benguela Upwelling System (BUS) in the south-eastern Atlantic Ocean to study the influence of zooplankton on the flux of particulate organic carbon (POC) through the water column and its sedimentation. Two long term moored and sixteen short term free-floating sediment trap systems were deployed. The mooring experiments were conducted for several years and the sixteen drifters were deployed on three different research cruises between 2019 and 2021. Zooplankton was separated from the trapped material and divided into 8 different zooplankton groups. [...]".
Source: EGUsphere
Authors: Luisa Chiara Meiritz et al.
DOI: https://doi.org/10.5194/egusphere-2024-700
Adjusting metabolic rates and critical oxygen tension in planktonic copepods under increasing hypoxia in highly productive coastal upwelling zones
Abstract.
"Ongoing ocean deoxygenation is threatening marine organisms globally. In eastern boundary upwelling systems, planktonic copepods dominate the epipelagic zooplankton, being crucial in the marine food web. Yet, they must cope with severe hypoxia caused by shoaling of the oxygen minimum zone. Based on laboratory experiments during 2021, we found differential responses in the metabolic rate (MR) and critical oxygen partial pressure of three abundant copepods. Calanoides patagoniensis doubled its MR during the upwelling season, so better exploiting the spring phytoplankton bloom for feeding and reproduction while maintaining their critical oxygen partial pressure unchanged between seasons. [...]".
Source: Wiley Online Library
Authors: Leissing Frederick et al.
DOI: https://doi.org/10.1002/lno.12556
Critical swimming speed of juvenile rockfishes (Sebastes) following long- and short-term exposures to acidification and deoxygenation
Abstract.
"Reef fishes in the California Current Ecosystem have evolved in habitats affected by seasonally variable, episodic upwelling of high pCO2 (acidified, low pH) and low dissolved oxygen (deoxygenated) water, which suggests that these fishes might exhibit resilience to ocean acidification (OA) and deoxygenation. Yet, how the fitness of these fish are affected by natural variability in pH and DO over short time scales remains poorly understood, as do the effects of longer-term trends in pH and DO driven by climate change. [...]".
Source: Science Direct
Authors: Corianna Flannery & Eric P. Bjorkstedt
DOI: https://doi.org/10.1016/j.jembe.2024.151993
Cold-Water Coral Reefs in the Oxygen Minimum Zones Off West Africa
Abstract.
"The discoveries of large reefs within cold-water coral mound provinces revealed that the West African margin is a coral hotspot area in the Atlantic Ocean. The most striking observation is that cold-water corals thrive in extensive oxygen minimum zones under extreme conditions. This points to a wide tolerance of cold-water corals in these regions to low oxygen concentrations. The coral mound provinces off Mauritania, Angola, and Namibia, which are located in the centre of the local oxygen minimum zones, were selected as key study areas, and their regional oceanographic, bio-ecological, and geo-morphological settings are described in detail. [...]".
Source: Springer Nature
Authors: Claudia Wienberg et al.
DOI: https://doi.org/10.1007/978-3-031-40897-7_8
Bottom-water hypoxia in the Paracas Bay (Peru, 13.8°S) associated with seasonal and synoptic time scale variability of winds and water stratification
Abstract.
"Coastal hypoxia can occur naturally in inshore areas of the Eastern Boundary Upwelling Systems, influenced by the nutrient-rich and low-oxygen upwelling waters. This study aims to explore the influence of water stratification and winds on bottom-water hypoxia of the Paracas Bay, an area subjected to the most intense alongshore winds and active coastal upwelling in the Peruvian coast. Monitoring data of the Pisco-Paracas water properties [...]".
Source: Science Direct
Authors: Lander Merma-Mora et al.
DOI: https://doi.org/10.1016/j.jmarsys.2023.103918
Spatial and Temporal Redox Heterogeneity Controlled by a Fe(II), Anoxic Upwelling System in the Early Mesoproterozoic Ocean
Abstract.
"The availability of oxygen and nutrients during the Mesoproterozoic (1.6–1.0 Ga) is thought to influence the rate of eukaryote evolution. The cause of the transition from low productivity in the upper Wumishan Formation to organic-rich sediments in the Hongshuizhuang Formation remains unknown. We report FeHR/FeT, Fepy/FeHR, MoEF, UEF, VEF, and [Ce/Ce*]SN in one core of the Yanliao Basin to study the redox evolution and compare it with other sections in different depths of the Yanliao Basin to get clues of the spatial and temporal redox heterogeneity. [...]".
Source: Wiley Online Library
Authors: Mingze Ye et al.
DOI: https://doi.org/10.1029/2023GL103598
Prokaryotic community dynamics and nitrogen-cycling genes in an oxygen-deficient upwelling system during La Niña and El Niño conditions
Abstract.
"Dissolved oxygen regulates microbial distribution and nitrogen cycling and, therefore, ocean productivity and Earth's climate. To date, the assembly of microbial communities in relation to oceanographic changes due to El Niño Southern Oscillation (ENSO) remains poorly understood in oxygen minimum zones (OMZ). The Mexican Pacific upwelling system supports high productivity and a permanent OMZ. Here, the spatiotemporal distribution of the prokaryotic community and nitrogen-cycling genes was investigated along a repeated transect subjected to varying oceanographic conditions associated with La Niña in 2018 and El Niño in 2019. [...]".
Source: Wiley Online Library
Authors: Silvia Pajares et al.
DOI: https://doi.org/10.1111/1462-2920.16362
Otoliths of marine fishes record evidence of low oxygen, temperature and pH conditions of deep Oxygen Minimum Zones
Abstract.
"The deep-sea is rapidly losing oxygen, with profound implications for marine organisms. Within Eastern Boundary Upwelling Systems, such as the California and the Benguela Current Ecosystems, an important question is how the ongoing expansion, intensification and shoaling of Oxygen Minimum Zones (OMZs) will affect deep-sea fishes throughout their lifetimes. One of the first steps to filling this knowledge gap is through the development of tools and techniques to track fishes’ exposure to hypoxic (<45 μmol kg-1), low-temperature (∼4–10°C) and low-pH (∼7.5) waters when inhabiting OMZs. [...]".
Source: Science Direct
Authors: Leticia Maria Cavole et al.
DOI: https://doi.org/10.1016/j.dsr.2022.103941
Quantifying the Contribution of Ocean Mesoscale Eddies to Low Oxygen Extreme Events
Abstract.
"Ocean mesoscale eddies have been identified as drivers of localized extremely low dissolved oxygen concentration ([O2]) conditions in the subsurface. We employ a global physical-biogeochemical ocean model at eddy-permitting resolution to conduct a census of open-ocean eddies near Eastern Boundary Upwelling Systems adjacent to tropical Oxygen Minimum Zones (OMZs). We track cyclonic and anticyclonic eddies with a surface signature over the period 1992–2018 and isolate their subsurface oxygen characteristics. We identify strongly deoxygenating eddies and quantify their contribution to low [O2] extreme events. [...]".
Source: Geophysical Research Letters
Authors: Jamie Atkins et al.
DOI: https://doi.org/10.1029/2022GL098672
Coupled changes in pH, temperature, and dissolved oxygen impact the physiology and ecology of herbivorous kelp forest grazers
Abstract.
"Understanding species’ responses to upwelling may be especially important in light of ongoing environmental change. Upwelling frequency and intensity are expected to increase in the future, while ocean acidification and deoxygenation are expected to decrease the pH and dissolved oxygen (DO) of upwelled waters. However, the acute effects of a single upwelling event and the integrated effects of multiple upwelling events on marine organisms are poorly understood. Here, we use in situ measurements of pH, temperature, and DO to characterize the covariance of environmental conditions within upwelling-dominated kelp forest ecosystems. We then test the effects of acute (0–3 days) and chronic (1–3 months) upwelling on the performance of two species of kelp forest grazers, the echinoderm, Mesocentrotus franciscanus, and the gastropod, Promartynia pulligo. We exposed organisms to static conditions in a regression design to determine the shape of the relationship between upwelling and performance and provide insights into the potential effects in a variable environment. We found that respiration, grazing, growth, and net calcification decline linearly with increasing upwelling intensity for M. francicanus over both acute and chronic timescales. [...]".
Source: Wiley Online Library
Authors: Emily M. Donham et al.
DOI: https://doi.org/10.1111/gcb.16125
Upwelling Bays: How Coastal Upwelling Controls Circulation, Habitat, and Productivity in Bays
Abstract.
"Bays in coastal upwelling regions are physically driven and biochemically fueled by their interaction with open coastal waters. Wind-driven flow over the shelf imposes a circulation in the bay, which is also influenced by local wind stress and thermal bay–ocean density differences. Three types of bays are recognized based on the degree of exposure to coastal currents and winds (wide-open bays, square bays, and elongated bays), and the characteristic circulation and stratification patterns of each type are described. Retention of upwelled waters in bays allows for dense phytoplankton blooms that support productive bay ecosystems. [...]"
Source: Annual Review of Marine Science
Authors: John L. Largier
DOI: 10.1146/annurev-marine-010419-011020
Article Open Access Published: 29 November 2019 Role of synoptic activity on projected changes in upwelling-favourable winds at the ocean’s eastern bo
Abstract.
"The climate of the ocean’s eastern boundaries is strongly influenced by subtropical anticyclones, which drive a surface wind stress that promotes coastal upwelling of nutrient-rich subsurface water that supports high primary productivity and an abundance of food resources. Understanding the projected response of upwelling-favourable winds to climate change has broad implications for coastal biogeochemistry, ecology, and fisheries. [...]"
Source: npj Climate and Atmospheric Science
Authors: Catalina Aguirre et al.
DOI: 10.1038/s41612-019-0101-9
Extinction of cold-water corals on the Namibian shelf due to low oxygen contents
"They were also able to link this event with a shift in the Benguela upwelling system, and an associated intensification of the oxygen minimum zone in this region. The team has now published their findings in the journal Geology.
Known as 'ecosystem engineers', cold-water corals play an important role in the species diversity of the deep sea. The coral species Lophelia pertusa is significantly involved in reef formation. [...]"
Source: EurekAlert!
The Dynamics and Impact of Ocean Acidification and Hypoxia:
Insights from Sustained Investigations in the Northern California Current Large Marine Ecosystem
Abstract.
"Coastal upwelling ecosystems around the world are defined by wind-generated currents that bring deep, nutrient-rich waters to the surface ocean where they fuel exceptionally productive food webs. These ecosystems are also now understood to share a common vulnerability to ocean acidification and hypoxia (OAH). In the California Current Large Marine Ecosystem (CCLME), reports of marine life die-offs by fishers and resource managers triggered research that led to an understanding of the risks posed by hypoxia. Similarly, unprecedented losses from shellfish hatcheries led to novel insights into the coastal expression of ocean acidification. [...]"
Source: Oceanography
Authors: Francis Chan et al.
DOI: 10.5670/oceanog.2019.312
Effects of upwelling duration and phytoplankton growth regime on dissolved oxygen levels in an idealized Iberian Peninsula upwelling system
Abstract.
"We apply a coupled modelling system composed of a state-of-the-art hydrodynamical model and a low complexity biogeochemical model to an idealized Iberian Peninsula upwelling system to identify the main drivers of dissolved oxygen variability and to study its response to changes in the duration of the upwelling season and in phytoplankton growth regime. [...]"
Source: Nonlinear Processes in Geophysics (preprint)
Authors: João H. Bettencourt et al.
DOI: 10.5194/npg-2019-47
Fish debris in sediments from the last 25 kyr in the Humboldt Current reveal the role of productivity and oxygen on small pelagic fishes
Abstract.
"Upwelling of cold, nutrient-rich water from the oxygen minimum zone (OMZ) off Peru sustains the world’s highest production of forage fish, mostly composed of anchovy (Engraulis ringens). However, the potential impacts of climate change on upwelling dynamics and thus fish productivity in the near future are uncertain. Here, we reconstruct past changes in fish populations during the last 25,000 years to unravel their response to changes in OMZ intensity and productivity. [...]"
Source: Progress in Oceanography
Authors: RenatoSalvatteci et al.
DOI: 10.1016/j.pocean.2019.05.006
Antarctic offshore polynyas linked to Southern Hemisphere climate anomalies
Abstract.
"Offshore Antarctic polynyas—large openings in the winter sea ice cover—are thought to be maintained by a rapid ventilation of deep-ocean heat through convective mixing. These rare phenomena may alter abyssal properties and circulation, yet their formation mechanisms are not well understood. Here we demonstrate that concurrent upper-ocean preconditioning and meteorological perturbations are responsible for the appearance of polynyas in the Weddell Sea region of the Southern Ocean. [...]"
Source: Nature
Authors: Ethan C. Campbell et al.
DOI: 10.1038/s41586-019-1294-0
Gas exchange estimates in the Peruvian upwelling regime biased by multi-day near-surface stratification
Abstract.
"The coastal upwelling regime off Peru in December 2012 showed considerable vertical concentration gradients of dissolved nitrous oxide (N2O) across the top few meters of the ocean. The gradients were predominantly downward, i.e., concentrations decreased toward the surface. Ignoring these gradients causes a systematic error in regionally integrated gas exchange estimates, when using observed concentrations at several meters below the surface as input for bulk flux parameterizations – as is routinely practiced. [...]"
Source: Biogeosciences
Authors: Tim Fischer et al.
DOI: 10.5194/bg-16-2307-2019
Diapycnal dissolved organic matter supply into the upper Peruvian oxycline
Abstract.
"The eastern tropical South Pacific (ETSP) hosts the Peruvian upwelling system, which represents one of the most productive areas in the world ocean. High primary production followed by rapid heterotrophic utilization of organic matter supports the formation of one of the most intense oxygen minimum zones (OMZs) in the world ocean, where dissolved oxygen (O2) concentrations reach less than 1 µmol kg−1. [...]"
Source: Biogeosciences
Authors: Alexandra N. Loginova et al.
DOI: 10.5194/bg-16-2033-2019
Remote and local drivers of oxygen and nitrate variability in the shallow oxygen minimum zone off Mauritania in June 2014
Abstract.
"Upwelling systems play a key role in the global carbon and nitrogen cycles and are also of local relevance due to their high productivity and fish resources. To capture and understand the high spatial and temporal variability in physical and biogeochemical parameters found in these regions, novel measurement techniques have to be combined in an interdisciplinary manner. Here we use high-resolution glider-based physical–biogeochemical observations in combination with ship-based underwater vision profiler, sensor and bottle data to investigate the drivers of oxygen and nitrate variability across the shelf break off Mauritania in June 2014. [...]"
Source: Biogeosciences
Authors: Soeren Thomsen et al.
DOI: 10.5194/bg-16-979-2019
N2O Emissions From the Northern Benguela Upwelling System
Abstract.
"The Benguela Upwelling System (BUS) is the most productive of all eastern boundary upwelling ecosystems and it hosts a well‐developed oxygen minimum zone. As such, the BUS is a potential hotspot for production of N2O, a potent greenhouse gas derived from microbially driven decay of sinking organic matter. Yet, the extent at which near‐surface waters emit N2O to the atmosphere in the BUS is highly uncertain. [...]"
Source: Geophysical Research Letters
Authors: D. L. Arévalo‐Martínez et al.
DOI: 10.1029/2018GL081648
Seasonal Variability of the Mauritania Current and Hydrography at 18°N
Abstract.
"Extensive field campaigns in the Mauritanian upwelling region between 2005 and 2016 provide the database for analyzing the seasonal variability of the eastern boundary circulation (EBC) and associated water mass distribution at 18°N. The data set includes shipboard upper ocean current, hydrographic, and oxygen measurements from nine research cruises conducted during upwelling (December to April) and relaxation (May to July) seasons. [...]"
Source: JGR Oceans
Authors: T. Klenz, M. Dengler and P. Brandt
DOI: 10.1029/2018JC014264
Deglacial to Holocene Ocean Temperatures in the Humboldt Current System as Indicated by Alkenone Paleothermometry
Abstract.
"The response of the Humboldt Current System to future global warming is uncertain. Here we reconstruct alkenone‐derived near‐surface temperatures from multiple cores along the Peruvian coast to infer the driving mechanisms of upwelling changes for the last 20 kyr. Our records show a deglacial warming consistent with Antarctic ice‐core temperatures and a Mid‐Holocene cooling, which, in combination with other paleoceanographic records, suggest a strengthening of upwelling conditions. [...]"
Source: Geophysical Research Letters
Authors: Renato Salvatteci et al.
DOI: 10.1029/2018GL080634
Effects of Coastal Upwelling and Downwelling on Hydrographic Variability and Dissolved Oxygen in Mobile Bay
Abstract.
"Upwellling and downwelling events are important coastal processes that strongly influence shelf ecosystem dynamics. Though changes on the shelf have been well studied, the impact of these events on estuarine systems has received less focus. In summer 2016 a downwelling and upwelling event were observed near the mouth of Mobile Bay. The impact of these events were examined throughout the bay with high spatial resolution observations. Five boat surveys were conducted to capture the spatial response of offshore forcing and its changes in the estuary. In addition to the surveys, 16 CTDs were deployed and measured temporal changes. [...]"
Source: JGR Oceans
Authors: Jeffrey Coogan, Brian Dzwonkowski and John Lehrter
DOI: 10.1029/2018JC014592
Pacific Decadal Oscillation and recent oxygen decline in the eastern tropical Pacific Ocean
Abstract.
"The impact of the positive and negative phases of the Pacific Decadal Oscillation (PDO) on the extension of the poorly oxygenated regions of the eastern Pacific Ocean was assessed using a coupled ocean circulation–biogeochemical model. We show that during a “typical” PDO-positive phase the volume of the suboxic regions expands by 7 % over 50 years due to a slowdown of the large-scale circulation related to the decrease in the intensity of the trade winds. Changes in oxygen levels are mostly controlled by advective processes between 10∘ N and 10∘ S, whereas diffusive processes are dominant poleward of 10∘: in a “typical” PDO-positive phase the sluggish equatorial current system provides less oxygen to the eastern equatorial part of the basin while the oxygen transport by diffusive processes significantly decreases south of 10∘ S. [...]"
Source: Biogeosciences
Authors: Olaf Duteil, Andreas Oschlies, and Claus W. Böning
DOI: 10.5194/bg-15-7111-2018
Tool to Capture Marine Biological Activity Gets Coastal Upgrade
"Upwelling hinders an efficient method to estimate a key measure of biological productivity in coastal waters, but accounting for surface temperatures could boost accuracy.
Although coastal waters make up only about 10% of the surface area of the ocean, they harbor most of its life. Measuring biological activity in these regions can reveal their impact on fisheries, low-oxygen dead zones, and the global carbon cycle, but coastal zones remain understudied. Now new research by Teeter et al. suggests how to improve the accuracy of a method that uses oxygen and argon measurements to quickly estimate marine biological activity. [...]"
Source: EOS
Reconstructing Aragonite Saturation State Based on an Empirical Relationship for Northern California
Abstract.
"Ocean acidification is a global phenomenon with highly regional spatial and temporal patterns. In order to address the challenges of future ocean acidification at a regional scale, it is necessary to increase the resolution of spatial and temporal monitoring of the inorganic carbon system beyond what is currently available. One approach is to develop empirical regional models that enable aragonite saturation state to be estimated from existing hydrographic measurements, for which greater spatial coverage and longer time series exist in addition to higher spatial and temporal resolution. [...]"
Source: Estuaries and Coasts
Authors: Catherine V. Davis et al.
DOI: 10.1007/s12237-018-0372-0
Modulation of the vertical particle transfer efficiency in the oxygen minimum zone off Peru
Abstract.
"The fate of the organic matter (OM) produced by marine life controls the major biogeochemical cycles of the Earth's system. The OM produced through photosynthesis is either preserved, exported towards sediments or degraded through remineralisation in the water column. The productive eastern boundary upwelling systems (EBUSs) associated with oxygen minimum zones (OMZs) would be expected to foster OM preservation due to low O2 conditions. But their intense and diverse microbial activity should enhance OM degradation. To investigate this contradiction, sediment traps were deployed near the oxycline and in the OMZ core on an instrumented moored line off Peru. [...]"
Source: Biogeosciences
Authors: Marine Bretagnon et al.
DOI: 10.5194/bg-15-5093-2018
Biogeochemical Role of Subsurface Coherent Eddies in the Ocean: Tracer Cannonballs, Hypoxic Storms, and Microbial Stewpots?
Abstract.
"Subsurface eddies are known features of ocean circulation, but the sparsity of observations prevents an assessment of their importance for biogeochemistry. Here we use a global eddying (0.1°) ocean-biogeochemical model to carry out a census of subsurface coherent eddies originating from eastern boundary upwelling systems (EBUS) and quantify their biogeochemical effects as they propagate westward into the subtropical gyres. [...]"
Source: Global Biogeochemical Cycles
Authors: Ivy Frenger et al.
DOI: 10.1002/2017GB005743
Multifarious anchovy and sardine regimes in the Humboldt Current System during the last 150 years
Abstract.
"The Humboldt Current System (HCS) has the highest production of forage fish in the world, although it is highly variable and the future of the primary component, anchovy, is uncertain in the context of global warming. Paradigms based on late 20th century observations suggest that large-scale forcing controls decadal-scale fluctuations of anchovy and sardine across different boundary currents of the Pacific. We develop records of anchovy and sardine fluctuations since 1860 AD using fish scales from multiple sites containing laminated sediments and compare them with Pacific basin-scale and regional indices of ocean climate variability. [...]"
Source: Global Change Biology
Authors: Renato Salvatteci et al.
DOI: 10.1111/gcb.13991
The Northern Gulf of Mexico During OAE2 and the Relationship Between Water Depth and Black Shale Development
Abstract.
"Despite their name, Oceanic Anoxic Events (OAEs) are not periods of uniform anoxia and black shale deposition in ancient oceans. Shelf environments account for the majority of productivity and organic carbon burial in the modern ocean, and this was likely true in the Cretaceous as well. However, it is unlikely that the mechanisms for such an increase were uniform across all shelf environments. Some, like the northwest margin of Africa, were characterized by strong upwelling, but what might drive enhanced productivity on shelves not geographically suited for upwelling? [...]"
Source: Plaeoceanography
Authors: Christopher M. Lowery
DOI: 10.1002/2017PA003180
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Tag Cloud
- anoxia (77)
- anthropogenic impacts (41)
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- biogeochemical cycling (24)
- biogeochemistry (36)
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- coastal waters (34)
- dead zone (46)
- denitrification (43)
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- oceanic anoxic events (52)
- oxygen cycle (25)
- oxygen minimum zone (218)
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- paleoceanography (178)
- plankton (27)
- upwelling (32)