Abstract. 

"Coastal seas may account for more than 75 % of global oceanic methane emissions. There, methane is mainly produced microbially in anoxic sediments from which it can escape to the overlying water column. Aerobic methane oxidation (MOx) in the water column acts as a biological filter, reducing the amount of methane that eventually evades to the atmosphere. The efficiency of the MOx filter is potentially controlled by the availability of dissolved methane and oxygen, as well as temperature, salinity, and hydrographic dynamics, and all of these factors undergo strong temporal fluctuations in coastal ecosystems. [...]"

Source: Biogeosciences 14
Authors: Lea Steinle et al.
DOI: 10.5194/bg-14-1631-2017

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Abstract. 

"In the oceans’ high-nitrate–low-chlorophyll regions, such as the Peru/Humboldt Current system and the adjacent eastern equatorial Pacific, primary productivity is limited by the micronutrient iron. Within the Peruvian upwelling area, bioavailable iron is released from the reducing continental margin sediments. The magnitude of this seafloor source could change with fluctuations in the extension or intensity of the oxygen minimum zones. Here we show that measurements of molybdenum, uranium and iron concentrations can be used as a proxy for sedimentary iron release, and use this proxy to assess iron release from the sea floor beneath the Peru upwelling system during the past 140,000 years. [...]"

Source: Nature Geoscience 7
Authors: Florian Scholz et al.
DOI: 10.1038/ngeo2162

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Abstract.

"Changes in ocean temperature and circulation patterns compounded by human activities are leading to oxygen minimum zone (OMZ) expansion with concomitant alteration in nutrient and climate active trace gas cycling. Here, we report the response of microbial eukaryote populations to seasonal changes in water column oxygen-deficiency using Saanich Inlet, a seasonally anoxic fjord on the coast of Vancouver Island British Columbia, as a model ecosystem. [...]"

Source: The ISME Journal 6
Authors: William Orsi et al.
DOI: 10.1038/ismej.2012.7

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"A groundbreaking scientific data collection program to expand the measuring of water quality off 18 West Maui shoreline sites has been forged between the state Department of Health and Maui community groups involved in the protection of the island’s nearshore waters. [...]"

Source: The Maui News

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Abstract.

"The seasonal upwelling along the west coast of India (WCI) brings nutrient-rich, oxygen-poor subsurface waters to the continental shelf, favoring very low oxygen concentrations in the surface waters during late boreal summer and fall. This yearly-recurring coastal hypoxia is more severe during some years, leading to coastal anoxia that has strong impacts on the living resources. In the present study, we analyze a 1/4◦ resolution coupled physical–biogeochemical regional oceanic simulation over the 1960–2012 period to investigate the physical processes influencing the oxycline interannual variability off the WCI, that being a proxy for the variability on the shelf in our model. [...]" 

Source: Bioggeosciences 14
Authors: Parvathi Vallivattathillam et al.
DOI: 10.5194/bg-14-1541-2017

Full article

Abstract.

"The Arabian Sea represents a prime example of an open ocean extended oxygen minimum zone (OMZ) with low oxygen concentrations (down to less than 2 mM) between 200 and 1000 m water depth. The OMZ impinges on the ocean floor, affect ingorganic matter (OM) mineralization. We investigated impact of oxygen depletion on the composition of macromolecularOM (MOM) along a transect through the OMZ on the slopes of the Murray Ridge. This sub-marine high in the northern Arabian Sea, with the top at approximately 500 m below sea surface (mbss), intersects the OMZ. We analyzed sediments deposited in the core of OMZ (suboxic conditions) [...]"

Source: Geochimica et Cosmochimica Acta 206
Authors: Nierop, K.G.J.; Reichart, G.-J.; Veld, H.; Sinninghe Damsté, J.S
DOI: dx.doi.org/10.1016/j.gca.2017.02.032

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Abstract.

"Biological oceanic processes, principally the surface production, sinking and interior remineralization of organic particles, keep atmospheric CO₂ lower than if the ocean was abiotic. The remineralization length scale (RLS, the vertical distance over which organic particle flux declines by 63%, affected by particle respiration, fragmentation and sinking rates) controls the size of this effect and is anomalously high in oxygen minimum zones (OMZ). Here we show in the Eastern Tropical North Pacific OMZ 70% of POC remineralization is due to microbial respiration, indicating that the high RLS is the result of lower particle fragmentation by zooplankton, likely due to the almost complete absence of zooplankton particle interactions in OMZ waters. [...]"

Source: Nature Communications 8
Authors: E. L. Cavan, M. Trimmer, F. Shelley & R. Sanders
DOI: 10.1038/ncomms14847

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Description

"Oxygen-starved coastal waters are rapidly increasing in prevalence worldwide. However, little is known about the impacts of these “dead zones” in tropical ecosystems or their potential threat to coral reefs. We document the deleterious effects of such an anoxic event on coral habitat and biodiversity, and show that the risk of dead-zone events to reefs worldwide likely has been seriously underestimated. Awareness of, and research on, reef hypoxia is needed to address the threat posed by dead zones to coral reefs."

Source: Proceedings of the National Academy of Sciences of the United Stated of America (PNAS)
Authors: Andrew H. Altieri et al.
DOI: 10.1073/pnas.1621517114

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Abstract. 

"Shallow sills restrict the ventilation of deep coastal fjords. Dense oceanic water seaward of the sill and lower density water within the receiving basin are generally required for oxygenated water to cross the sill and descend deep into the fjord. Here, we use concurrent 10-year time series from current meters in the fjord and on the continental shelf to examine ventilation of the 120-m deep, anoxic inner basin of Effingham Inlet on the west coast of Vancouver Island. Whereas density currents traverse the 40 m-deep sill and flow into the inner basin at mid-depth at quasi-fortnightly tidal intervals, only five current intrusions descended to the bottom of the basin over the decade-long measurement period. [...]"

Source: Journal of Geophysical Research (JGR)
Authors: Richard E. Thomson et al.
DOI: 10.1002/2016JC012512

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Experiment with the KOSMOS mesocosms in Peru

"If less and less oxygen is available in the ocean as a result of climate change, this also affects highly productive regions such as the waters off the coast of Peru – an area strongly influenced by the nutrient-rich Humboldt Current. An international team led by GEOMAR Helmholtz Center for Ocean Research Kiel now investigates the impact of declining oxygen on the productivity of the Peruvian upwelling system employing the KOSMOS mesocosm facility. [...]"

Source: GEOMAR
Contact: Maike Nicolai

Link to News

Abstract.  

"Although pH is a fundamental property of Earth’s oceans, critical to our understanding of seawater biogeochemistry, its long-timescale geologic history is poorly constrained. We constrain seawater pH through time by accounting for the cycles of the major components of seawater. We infer an increase from early Archean pH values between ~6.5 and 7.0 and Phanerozoic values between ~7.5 and 9.0, which was caused by a gradual decrease in atmospheric pCO₂ in response to solar brightening, alongside a decrease in hydrothermal exchange between seawater and the ocean crust. [...]"

Source: Science Vol. 355
Authors: I. Halevy, A. Bachan
DOI: 10.1126/science.aal4151

Full article

Abstract.

"Most estuaries and inland waters are significant source for atmospheric CO₂ because of input of terrestrial inorganic carbon and mineralization of terrestrially supplied organic carbon. In contrast to most coastal waters, some estuaries with small freshwater discharge are weak source or sometimes sink for CO₂. Extensive surveys of pCO₂ in Tokyo Bay showed that the overall bay acts as a strong net sink for atmospheric CO₂. Although small area was a consistent source for CO₂, active photosynthesis driven by nutrient loading from the land overwhelmed the CO₂ budget in the bay. [...]"

Source: Scientific Reports Vol. 7
Authors: Atsushi Kubo, Yosaku Maeda & Jota Kanda
DOI: 10.1038/srep44355

Full article

(January 2008)

Abstract. 

"Benthic processes were measured at a coastal deposition area in the northern Baltic Sea, covering all seasons. The N₂ production rates, 90–400μmol Nm−2d−1, were highest in autumn-early winter and lowest in spring. Heterotrophic bacterial production peaked unexpectedly late in the year, indicating that in addition to the temperature, the availability of carbon compounds suitable for the heterotrophic bacteria also plays a major role in regulating the denitrification rate. Anaerobic ammonium oxidation (anammox) was measured in spring and autumn and contributed 10% and 15%, respectively, to the total N₂ production. [...]"

Source: Hydrobiologia 596
Authors: Susanna Hietanen & Jorma Kuparinen
DOI: 10.1007/s10750-007-9058-5

Full article

"We are integrating existing data sets collected in the Northern Gulf of Mexico to study hypoxia impacts on coastal ecosystems and associated fisheries. We are using probabilistic, data-centric modeling to assess the spatiotemporal dynamics of hypoxia and to understand and forecast fisheries and ecosystem impacts. Our research focuses on data-driven inferences driving hypoxia and fisheries dynamics, rigorous uncertainty quantification, and prudent forecasting methodologies for all coastal areas."

Source: National Centers for Coastal Ocean Science (NCCOS)
Primary Contact: David Hilmer

Link to Project Details 

"We are linking a suite of well-established models to quantify fish and shrimp population responses to combinations of nutrient loadings and planned river diversions. Our scenario analyses include different land-use and agricultural practices in the watershed and alternative river diversions. The linked model system informs and supports management decisions by estimating how reduced nutrients and diversion operations affect hypoxia and key living resources." 

Source: National Centers for Coastal Ocean Science (NCCOS)
Primary Contact: David Hilmer

Link to Project Details

Collaborative Research Centre 754 investigates oxygen minimum zone in the Southeast Pacific

Last week, the first of four consecutive expeditions with the German research vessel METEOR started in Valparaiso (Chile) to investigate the oxygen minimum zone off the coast of Peru. For four months scientists from Kiel's Collaborative Research Center 754 “Climate - Biogeochemical Interactions in the Tropical Ocean” will examine the consequences of global change for the oxygen distribution in the tropical East Pacific, as well as the regional biological, chemical and environmental impacts.

Source: GEOMAR
Contact: Jan Steffen

Link to Project Details

Abstract 

"Hydrogen peroxide (H₂O₂) is present ubiquitously in marine surface waters where it is a reactive intermediate in the cycling of many trace elements. Photochemical processes are considered the dominant natural H₂O₂ source, yet cannot explain nanomolar H₂O₂concentrations below the photic zone. Here, we determined the concentration of H2O2 in full depth profiles across three ocean basins (Mediterranean Sea, South Atlantic and South Pacific Oceans). To determine the accuracy of H₂O₂ measurements in the deep ocean we also re-assessed the contribution of interfering species to ‘apparent H₂O₂’, as analysed by the luminol based chemiluminescence technique. [...] Our results indicate that a dark, pelagic H₂O₂ production mechanism must occur throughout the deep ocean. A bacterial source of H₂O₂ is the most likely origin and we show that this source is likely sufficient to account for all of the observed H₂O₂ in the deep ocean."

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Abstract.

"Based on hydrographic data and vertical distributions of tropical species of fish larvae (Diogenichthys laternatus, Vinciguerria lucetia, Bregmaceros bathymaster and Auxis spp), effects of “Godzilla El Niño 2015-2016” in the shallow oxygen minimum zone off Mexico were analyzed. Zooplankton samples were collected during four cruises, before (February 2010, April 2012) and during (June 2015, March 2016) the warm event. Temporal series of sea surface temperature revealed that June 2015 was the warmest June of the last years. Conservative Temperature was > 2°C higher than normal in the surface mixed layer, and the suboxic layer (4.4 µmol/kg) reached as shallow as 100 m depth. Unexpected results were that larval abundances were relatively high during the warm event, unlike zooplankton volumes, which declined.[...]"

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Iron is an essential fuel for life in the oceans. The influence of this element on biogeochemistry — and nitrogen cycling in particular — varies across environments and time.

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Abstract.

"Dissolved oxygen (DO) concentration in the ocean is an important component of marine biogeochemical cycles and will be greatly altered as climate change persists. In this study a global oceanic carbon cycle model (HAMOCC 2.0) is used to address how mechanisms of oxygen minimum zone (OMZ) expansion respond to changes in CO₂ radiative forcing. Atmospheric pCO₂ is increased at a rate of 1 % annually and the model is stabilized at 2 ×, 4 ×, 6 ×, and 8 × preindustrial pCO₂ levels. With an increase in CO₂ radiative forcing, the OMZ in the Pacific Ocean is controlled largely by changes in particulate organic carbon (POC) export, resulting in increased remineralization and thus expanding the OMZs within the tropical Pacific Ocean. A potential decline in primary producers in the future as a result of environmental stress due to ocean warming and acidification could lead to a substantial reduction in POC export production, vertical POC flux, and thus increased DO concentration particularly in the Pacific Ocean at a depth of 600–800 m. In contrast, the vertical expansion of the OMZs within the Atlantic is linked to increases POC flux as well as changes in oxygen solubility with increasing seawater temperature. Changes in total organic carbon and increase sea surface temperature (SST) also lead to the formation of a new OMZ in the western subtropical Pacific Ocean. [...]"

LINK

Abstract.

"Oxygen minimum zones (OMZs) contain the largest pools of oceanic methane but its origin and fate are poorly understood. High-resolution (<15 m) water column profiles revealed a 300 m thick layer of elevated methane (20–105 nm) in the anoxic core of the largest OMZ, the Eastern Tropical North Pacific. Sediment core incubations identified a clear benthic methane source where the OMZ meets the continental shelf, between 350 and 650 m, with the flux reflecting the concentration of methane in the overlying anoxic water. Further incubations characterised a methanogenic potential in the presence of both porewater sulphate and nitrate of up to 88 nmol g⁻¹day⁻¹ in the sediment surface layer. In these methane-producing sediments, the majority (85%) of methyl coenzyme M reductase alpha subunit (mcrA) gene sequences clustered with Methanosarcinaceae ([above] 96% similarity to Methanococcoides sp.), a family capable of performing non-competitive methanogenesis. Incubations with C-CH₄ showed potential for both aerobic and anaerobic methane oxidation in the waters within and above the OMZ. Both aerobic and anaerobic methane oxidation is corroborated by the presence of particulate methane monooxygenase (pmoA) gene sequences, related to type I methanotrophs and the lineage of Candidatus Methylomirabilis oxyfera, known to perform nitrite-dependent anaerobic methane oxidation (N-DAMO), respectively."

LINK to article

"The deep sea is the largest environment on the planet. Most of the deep sea consists of the water column above the seafloor, the pelagic zone. In many parts of the pelagic ocean, no scientific sample or observation has ever been collected. Consequently, knowledge on deep-sea pelagic biodiversity and on the biology and ecology of organisms in this realm remain largely unknown.
During MSM61 we perform deployments with the pelagic in situ observation system or PELAGIOS. This ocean instrument collects high definition video during horizontal transects while being towed on a CTD cable at various depths of interest.[...]"

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