Report: High seas in high danger as ecological tipping point nears
"As delegates convene at the United Nations to work out an international treaty to preserve the biodiversity of the high seas, a new report underscores the need to protect the remote ocean.
Scientists at Oxford University in the United Kingdom reviewed 271 research papers published between 2012 and 2017 and synthesized the latest data on the impact of climate change, fishing and pollution on the high seas. Their findings are not encouraging: Even the most distant reaches of the ocean are suffering from chemical and plastic contamination, a loss of biodiversity and the consequences of rising temperatures. [...]"
Differential effects of nitrate, ammonium, and urea as N sources for microbial communities in the North Pacific Ocean
"Nitrogen (N) is the major limiting nutrient for phytoplankton growth and productivity in large parts of the world's oceans. Differential preferences for specific N substrates may be important in controlling phytoplankton community composition. To date, there is limited information on how specific N substrates influence the composition of naturally occurring microbial communities. We investigated the effect of nitrate ( ), ammonium ( ), and urea on microbial and phytoplankton community composition (cell abundances and 16S rRNA gene profiling) and functioning (photosynthetic activity, carbon fixation rates) in the oligotrophic waters of the North Pacific Ocean. [...]"
Source: Limonology and Oceanography
Authors: I.N. Shilova et al.
Project: Kelp Forest Array
The Kelp Forest Array (KFA) is a state-of-the-art cabled platform for observational and experimental science aimed at monitoring and understanding local impacts of global climate change. Increasing climate change and ocean acidification pressures require the establishment of long-term, baseline monitoring methods to document how a currently healthy system changes and to understand effects of climate change in relation to this natural variability. Current monitoring practices limit resolution and longevity of baseline data sets.
Evidence for rapid weathering response to climatic warming during the Toarcian Oceanic Anoxic Event
"Chemical weathering consumes atmospheric carbon dioxide through the breakdown of silicate minerals and is thought to stabilize Earth’s long-term climate. However, the potential influence of silicate weathering on atmospheric pCO2 levels on geologically short timescales (103–105 years) remains poorly constrained. Here we focus on the record of a transient interval of severe climatic warming across the Toarcian Oceanic Anoxic Event or T-OAE from an open ocean sedimentary succession from western North America. [...]"
Source: Scientific Reports
Authors: Theodore R. Them et al.
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