Otoliths of marine fishes record evidence of low oxygen, temperature and pH conditions of deep Oxygen Minimum Zones
"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.
Quantifying the Contribution of Ocean Mesoscale Eddies to Low Oxygen Extreme Events
"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.
Coupled changes in pH, temperature, and dissolved oxygen impact the physiology and ecology of herbivorous kelp forest grazers
"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.
Upwelling Bays: How Coastal Upwelling Controls Circulation, Habitat, and Productivity in Bays
"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
Article Open Access Published: 29 November 2019 Role of synoptic activity on projected changes in upwelling-favourable winds at the ocean’s eastern bo
"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.
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. [...]"
The Dynamics and Impact of Ocean Acidification and Hypoxia:
Insights from Sustained Investigations in the Northern California Current Large Marine Ecosystem
"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. [...]"
Authors: Francis Chan et al.
Effects of upwelling duration and phytoplankton growth regime on dissolved oxygen levels in an idealized Iberian Peninsula upwelling system
"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.
Fish debris in sediments from the last 25 kyr in the Humboldt Current reveal the role of productivity and oxygen on small pelagic fishes
"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.
Antarctic offshore polynyas linked to Southern Hemisphere climate anomalies
"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. [...]"
Authors: Ethan C. Campbell et al.
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