Oxygen loss in fjords, coastal areas, and open ocean systems
"Loss of oxygen and expansion of oxygen depleted environments have been witnessed in both coastal and open-ocean systems since the middle of the 20th century, and ocean modelling predicts continuing decease by the year 2100. Oxygen depletion occurs thus during the same time epoch as global warming. Increased knowledge on how and why oxygen varies in space and time shapes the biogeochemical and ecological structure of marine systems and will be needed for future predictions of marine productivity. In coastal systems deoxygenation is also linked to human activities that lead to increased loadings of nutrients and organic matter, and to regional effects of climate induced changes in wind and precipitation patterns[...]"
Source: BJERKNES CENTRE
Authors: Anne Gro Vea Salvanes et al.
Rates and pathways of N2 production in a persistently anoxic fjord: Saanich Inlet, British Columbia
"Marine oxygen minimum zones (OMZs) support 30-50% of global fixed-nitrogen (N) loss but comprise only 7% of total ocean volume. This N-loss is driven by canonical denitrification and anaerobic ammonium oxidation (anammox), and the distribution and activity of these two processes vary greatly in space and time. Factors that regulate N-loss processes are complex, including organic matter availability, oxygen concentrations, and NO2- and NH4+ concentrations. [,,,]"
Source: Frontiers in Marine Science
Authors: Céline C. Michiels et al.
50-years of data from a 'living oxygen minimum' lab could help predict the oceans' future
The mass of data, collected in two new Nature family papers, could help scientists better predict the impact of human activities and ocean deoxygenation on marine environments. Currently, oxygen minimum zones (OMZs) constitute up to 7 percent of global ocean volume. Continued expansion of OMZs in the northeastern subarctic Pacific has the potential to transport oxygen-depleted waters into coastal regions, adversely affecting nutrient cycles and fisheries productivity. [...]"
Source: University of British Columbia (media contact: Chris Balma)
Turbulence and hypoxia contribute to dense zooplankton scattering layers in Patagonian Fjord System
"Abstract. The Puyuhuapi Fjord is an atypical fjord, with two mouths, located in northern Patagonia (44.7° S). One mouth lies to the south, close to the Pacific Ocean, whilst the second connects with the Jacaf Channel to the north where a shallow sill inhibits deep water ventilation contributing to the hypoxic conditions below ~ 100 m depth. Acoustic Doppler Current Profiler moorings, scientific echo sounder transects, and in-situ abundance measurements were used to study zooplankton assemblages and migration patterns along Puyuhuapi Fjord and Jacaf Channel. […]"
Source: Ocean Science (in review)
Authors: Iván Pérez-Santos et al.
Read the full article here.
Effect of oxygen minimum zone formation on communities of marine protists
"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.
Buoyancy-driven coastal current blocks ventilation of an anoxic fjord on the Pacific coast of Canada
"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.