Decadal oxygen change in the eastern tropical North Atlantic
"Repeat shipboard and multi-year moored observations obtained in the oxygen minimum zone (OMZ) of the eastern tropical North Atlantic (ETNA) were used to study the decadal change in oxygen for the period 2006–2015. Along 23° W between 6 and 14° N, oxygen decreased with a rate of −5.9 ± 3.5 µmol kg−1 decade−1 within the depth covering the deep oxycline (200–400 m), while below the OMZ core (400–1000 m) oxygen increased by 4.0 ± 1.6 µmol kg−1 decade−1 on average. The inclusion of these decadal oxygen trends in the recently estimated oxygen budget for the ETNA OMZ suggests a weakened ventilation of the upper 400 m, whereas the ventilation strengthened homogeneously below 400 m. [...]"
Source: Ocean Science
Authors: Johannes Hahn, Peter Brandt, Sunke Schmidtko and Gerd Krahmann
Low oxygen eddies in the eastern tropical North Atlantic: Implications for N2O cycling
"Nitrous oxide (N2O) is a climate relevant trace gas, and its production in the ocean generally increases under suboxic conditions. The Atlantic Ocean is well ventilated, and unlike the major oxygen minimum zones (OMZ) of the Pacific and Indian Oceans, dissolved oxygen and N2O concentrations in the Atlantic OMZ are relatively high and low, respectively. [...]"
Source: Scientific Reports
Authors: D. S. Grundle et al.
Oxygen minimum zone: An important oceanographic habitat for deep-diving northern elephant seals
"Little is known about the foraging behavior of top predators in the deep mesopelagic ocean. Elephant seals dive to the deep biota-poor oxygen minimum zone (OMZ) (>800 m depth) despite high diving costs in terms of energy and time, but how they successfully forage in the OMZ remains largely unknown. Assessment of their feeding rate is the key to understanding their foraging behavior, but this has been challenging. Here, we assessed the feeding rate of 14 female northern elephant seals determined by jaw motion events (JME) and dive cycle time to examine how feeding rates varied with dive depth, particularly in the OMZ. [...]"
Source: Ecology and Evolution
Authors: Yasuhiko Naito et al.
Glacial-Interglacial changes and Holocene variations in Arabian Sea denitrification
"At present the Arabian Sea has a permanent oxygen minimum zone (OMZ) at water depths between about 100 m and 1200 m. Active denitrification in this OMZ is recorded by enhanced δ15N values in the sediments. Sediment cores show a δ15N increase from early to late Holocene which is contrary to the trend in other regions of water column denitrification. We calculated composite sea surface temperature (SST) and δ15N in time slices of 1000 years of the last 25 ka to better understand the reasons for the establishment of the Arabian Sea OMZ and its response to changes in the Asian monsoon system. [...]"
Source: Biogeosciences (under review)
Authors: Birgit Gaye et al.
PICES - 4th International Symposium
The Effects of Climate Change on the World's Oceans
BACKGROUND AND OBJECTIVES
The 4th International Symposium will bring together experts from around the world to better understand climate impacts on ocean ecosystems – and how to respond.
The Symposium will:
- Highlight the latest information on how oceans are changing, what is at risk and how to respond;
- Identify key knowledge gaps;
- Promote collaborations; and
- Stimulate the next generation of science and actions
The Symposium will include:
- Great sessions, presentations, and posters
- Opportunities for pre- or post-meeting workshops
- Special events for early career scientists
- Sponsorship and Exhibit Opportunities
Key Topic Areas:
- Characterization of ocean changes and the climate-ocean system
- Extreme and abrupt changes in ocean systems
- Impacts of changing climate on ocean physical, chemical and biological conditions
- Impacts of changing climate on ocean-dependent sectors, societies and economies
- Responding to climate-related changes in ocean conditions – Governance, institutional and sectoral adaptations
- Advancing methods to project climate-related impacts in ocean ecosystems
For further information please visit the event's homepage.
Start Date: 6/4/18
Coastal hypoxia and sediment biogeochemistry
"The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. [...]"
Source: Biogeosciences (2009)
Authors: J. J. Middelburg and L. A. Levin
Massive Bloom Of Pickle-Shaped Sea Creatures Fills The Pacific
"Millions of tubular sea creatures called pyrosomes have taken over the Pacific Ocean in an unprecedented bloom that has scientists baffled.
These bumpy, translucent organisms look like sea cucumbers that range in size from six inches to more than two feet long. But they’re actually made up of hundreds of tiny animals knit together with tissue into a filter-feeding cylinder. [...]
No one knows what the effects of the bloom will be, but scientists worry that if all the creatures die off at once they could sink to the seafloor and suck up all the oxygen as they’re decomposing, creating a dead zone for marine life."
Ecological Energetic Perspectives on Responses of Nitrogen-Transforming Chemolithoautotrophic Microbiota to Changes in the Marine Environment
"Transformation and mobilization of bioessential elements in the biosphere, lithosphere, atmosphere and hydrosphere constitute the Earth's biogeochemical cycles, which are driven mainly by microorganisms through their energy and material metabolic processes. Without microbial energy harvesting from sources of light and inorganic chemical bonds for autotrophic fixation of inorganic carbon, there would not be sustainable ecosystems in the vast ocean. Although ecological energetics (eco-energetics) has been emphasized as a core aspect of ecosystem analyses and microorganisms largely control the flow of matter and energy in marine ecosystems, marine microbial communities are rarely studied from the eco-energetic perspective. [...]"
Source: Frontiers in Microbiology
Authors: Hongyue Dang and Chen-Tung A. Chen
Reminder: SFB 754 International Conference
The distribution of oxygen in the ocean is controlled by physical, biogeochemical and biological processes. Both the supply and consumption of oxygen are sensitive to climate change in ways that are not fully understood.
Recent observations suggest that the oxygen content of the ocean is declining (ocean deoxygenation) and that oxygen minimum zones and coastal hypoxia sites are expanding with tremendous effects on the ocean’s ecosystems and living organisms.
This conference will:
- focus on the past, present and future state of oxygen in the ocean on global, regional and local scales
- nalyse mechanisms and feedbacks critical to identify natural and anthropogenic causes of oxygen variability
- determine impacts on biogeochemical cycles and ecosystems
The call for submission opens December 2017.
NOAA, USGS and partners predict third largest Gulf of Mexico summer ‘dead zone’ ever
"Larger-than-average low and no oxygen area may affect the region’s shrimp fisheries
Federal scientists forecast that this summer’s Gulf of Mexico dead zone – an area of low to no oxygen that can kill fish and other marine life – will be approximately 8,185 square miles, or about the size of New Jersey.
This would be the third largest dead zone recorded since monitoring began 32 years ago – the average Gulf dead zone since then has been 5,309 square miles.
The Gulf’s hypoxic or low-oxygen zones are caused by excess nutrient pollution, primarily from human activities such as agriculture and wastewater treatment. The excess nutrients stimulate an overgrowth of algae, which then sinks and decomposes in the water. The resulting low oxygen levels are insufficient to support most marine life and habitats in near-bottom waters, threatening the Gulf’s fisheries. [...]"
Source: National Oceanic and Atmospheric Administration (NOAA)