News

The geologic history of seawater pH

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


A significant net sink for CO2 in Tokyo Bay

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


Seasonal and short-term variation in denitrification and anammox at a coastal station on the Gulf of Finland, Baltic Sea

(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


Synthesis and Integrated Modeling of Long-Term Data Sets to Support Fisheries and Hypoxia Management in the Northern Gulf of Mexico

"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 


Using Linked Models to Predict Impacts of Hypoxia on Gulf Coast Fisheries Under Scenarios of Watershed and River Management

"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


Four-month Cruise with German RV METEOR off Peru

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


Hydrogen peroxide in deep waters from the Mediterranean Sea, South Atlantic and South Pacific Oceans

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."

 

LINK


Hydrographic and fish larvae distribution during the “Godzilla El Niño 2015-2016” in the shallow oxygen minimum zone of the eastern Pacific Ocean

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.[...]"

 

LINK


Iron entangled

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.

 

LINK


Response of export production and dissolved oxygen concentrations in oxygen minimum zones to pCO2 and temperature stabilization scenarios

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


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