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Major impacts of climate change on deep-sea benthic ecosystems

The deep sea encompasses the largest ecosystems on Earth. Although poorly known, deep seafloor ecosystems provide services that are vitally important to the entire ocean and biosphere. Rising atmospheric greenhouse gases are bringing about significant changes in the environmental properties of the ocean realm in terms of water column oxygenation, temperature, pH and food supply, with concomitant impacts on deep-sea ecosystems. Projections suggest that abyssal (3000–6000 m) ocean temperatures could increase by 1°C over the next 84 years, while abyssal seafloor habitats under areas of deep-water formation may experience reductions in water column oxygen concentrations by as much as 0.03 mL L–1 by 2100. Bathyal depths (200–3000 m) worldwide will undergo the most significant reductions in pH in all oceans by the year 2100 (0.29 to 0.37 pH units). O2 concentrations will also decline in the bathyal NE Pacific and Southern Oceans, with losses up to 3.7% or more, especially at intermediate depths. Another important environmental parameter, the flux of particulate organic matter to the seafloor, is likely to decline significantly in most oceans, most notably in the abyssal and bathyal Indian Ocean where it is predicted to decrease by 40–55% by the end of the century. Unfortunately, how these major changes will affect deep-seafloor ecosystems is, in some cases, very poorly understood. In this paper, we provide a detailed overview of the impacts of these changing environmental parameters on deep-seafloor ecosystems that will most likely be seen by 2100 in continental margin, abyssal and polar settings. We also consider how these changes may combine with other anthropogenic stressors (e.g., fishing, mineral mining, oil and gas extraction) to further impact deep-seafloor ecosystems and discuss the possible societal implications.

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IMBIZO 5: “Marine biosphere research for a sustainable ocean: Linking ecosystems, future states and resource management”, 2-5 October 2017, Woods Hole, USA

Deadline for abstract submission: 30 May 2017!

The fifth IMBeR IMBIZO (the Zulu word for a gathering) will be hosted by the Ocean, Carbon & Biogeochemistry Group at the Woods Hole Oceanographic Institution, Woods Hole, MA, USA from 2-6 October 2017.

IMBIZO 5 will follow the usual format of three concurrent but interacting workshops. The three workshops are:

  • Critical constraints on future projections of marine systems (co-Chairs: Laurent Bopp and Eric Galbraith)
  • Metabolic diversity and evolution in marine biogeochemical cycling and ocean ecosystem processes (co-Chairs: Gerhard Herndl and Tatiana Rynearson)
  • Management Strategy Evaluation: Achieving transparency in natural resource management by quantitatively bridging social and natural science uncertainties (co-Chairs: Ingrid van Putten and Cisco Werner)

To ensure an environment conducive to interaction and discussion, each workshop will be limited to around 40 participants. For a diversity of scientific interests, participants will be selected according to their research interests and the abstracts that they submit.

Choose a workshop, and submit an abstract!

Further information.

Uncertain future for Southern Ocean phytoplankton

A new review of scientific research into the impact of climate change on Southern Ocean phytoplankton has revealed uncertainty about the future of the single-celled plants at the base of the ocean food chain, which play a key role in reducing atmospheric carbon.

A range of climate-induced stressors, from warming seas and increased ocean acidification to reductions in salinity and sea ice, is expected to alter phytoplankton communities across the Southern Ocean.

But a review of the latest scientific research, by IMAS PhD student Stacy Deppeler in collaboration with the Australian Antarctic Division and ACE CRC, has revealed that a clear trend of how Southern Ocean phytoplankton are affected is not expected to become apparent until mid-century, by which time the changes may be too far progressed to mitigate or reverse.

“While a fundamental part of the ecosystem is changing in ways that could have global implications, there’s uncertainty about exactly what the changes and their impact will be,” Ms Deppeler said.

Continue reading ‘Uncertain future for Southern Ocean phytoplankton’

Southern Ocean phytoplankton in a changing climate

Phytoplankton are the base of the Antarctic food web, sustain the wealth and diversity of life for which Antarctica is renowned, and play a critical role in biogeochemical cycles that mediate global climate. Over the vast expanse of the Southern Ocean (SO), the climate is variously predicted to experience increased warming, strengthening wind, acidification, shallowing mixed layer depths, increased light (and UV), changes in upwelling and nutrient replenishment, declining sea ice, reduced salinity, and the southward migration of ocean fronts. These changes are expected to alter the structure and function of phytoplankton communities in the SO. The diverse environments contained within the vast expanse of the SO will be impacted differently by climate change; causing the identity and the magnitude of environmental factors driving biotic change to vary within and among bioregions. Predicting the net effect of multiple climate-induced stressors over a range of environments is complex. Yet understanding the response of SO phytoplankton to climate change is vital if we are to predict the future state/s of the ecosystem, estimate the impacts on fisheries and endangered species, and accurately predict the effects of physical and biotic change in the SO on global climate. This review looks at the major environmental factors that define the structure and function of phytoplankton communities in the SO, examines the forecast changes in the SO environment, predicts the likely effect of these changes on phytoplankton, and considers the ramifications for trophodynamics and feedbacks to global climate change. Predictions strongly suggest that all regions of the SO will experience changes in phytoplankton productivity and community composition with climate change. The nature, and even the sign, of these changes varies within and among regions and will depend upon the magnitude and sequence in which these environmental changes are imposed. It is likely that predicted changes to phytoplankton communities will affect SO biogeochemistry, carbon export, and nutrition for higher trophic levels.

Continue reading ‘Southern Ocean phytoplankton in a changing climate’

Spatial and temporal controls on the inorganic carbon system of the Western Arctic Ocean

The Arctic Ocean plays a critical role in the global carbon cycle. It is believed to be particularly sensitive to the effects of climate change, is already undergoing dramatic changes, and is therefore important to study in that context. Most studies of the inorganic carbon system in the Western Arctic focus on hydrographic datasets from summer and/or fall (July-October), and do not consider the full response of the system to the timing of ice retreat, organic matter production and remineralization, and ice advance. Here we present the first dataset to investigate the spatial and temporal controls on the inorganic carbon system from early spring (pre-phytoplankton), late spring (initial phytoplankton bloom), summer (post-bloom), and fall in 2014. Our results suggest that the timing of ice retreat has important implications for the length of the phytoplankton growing season, and thus influences the magnitude of biological carbon cycling. We extend our analysis to include high-resolution temporal estimates of air-sea CO2 flux, and estimate a total annual CO2 uptake in the Chukchi Sea of ~7.7 Tg C. This is the first dataset to evaluate the importance of different seasonal observations within one year on the annual uptake of CO2 in the western Arctic Ocean. Our results show that extrapolations from one observational dataset result in large over- or underestimations of annual CO2 flux.

Continue reading ‘Spatial and temporal controls on the inorganic carbon system of the Western Arctic Ocean’

Experimental evidence of formation of transparent exopolymer particles (TEP) and POC export provoked by dust addition under current and high pCO2 conditions

The evolution of organic carbon export to the deep ocean, under anthropogenic forcing such as ocean warming and acidification, needs to be investigated in order to evaluate potential positive or negative feedbacks on atmospheric CO2 concentrations, and therefore on climate. As such, modifications of aggregation processes driven by transparent exopolymer particles (TEP) formation have the potential to affect carbon export. The objectives of this study were to experimentally assess the dynamics of organic matter, after the simulation of a Saharan dust deposition event, through the measurement over one week of TEP abundance and size, and to evaluate the effects of ocean acidification on TEP formation and carbon export following a dust deposition event. Three experiments were performed in the laboratory using 300 L tanks filled with filtered seawater collected in the Mediterranean Sea, during two ‘no bloom’ periods (spring at the start of the stratification period and autumn at the end of this stratification period) and during the winter bloom period. For each experiment, one of the two tanks was acidified to reach pH conditions slightly below values projected for 2100 (~ 7.6–7.8). In both tanks, a dust deposition event of 10 g m-2 was simulated at the surface. Our results suggest that Saharan dust deposition triggered the abiotic formation of TEP, leading to the formation of organic-mineral aggregates. The amount of particulate organic carbon (POC) exported was proportional to the flux of lithogenic particles to the sediment traps. Depending on the season, the POC flux following artificial dust deposition ranged between 38 and 90 mg m-2 over six experimental days. Such variability is likely linked to the seasonal differences in the quality and quantity of TEP-precursors initially present in seawater. Finally, these export fluxes were not significantly different at the completion of the three experiments between the two pH conditions.

Continue reading ‘Experimental evidence of formation of transparent exopolymer particles (TEP) and POC export provoked by dust addition under current and high pCO2 conditions’

Team investigates effects of acidification on marine ecosystem

LONDON – British and Japanese scientists are conducting new research seeking to discover how Japan’s marine ecosystem may be affected by global warming. They are studying the potential side effects of rising acidity in Japan’s seas caused by increased levels of carbon dioxide in the atmosphere.

Previous studies in the Mediterranean have shown that increased acidification can disrupt the growth of sea organisms, with potentially long-term implications for the marine food chain.

Researchers hope their findings will inform politicians about the importance of cutting greenhouse gas emissions. Scientists believe the heating of the world’s oceans will impact marine ecology, but less is known about a second byproduct of global warming: acidification.

The world’s oceans are absorbing higher levels of CO2. This dissolves into the seawater and reacts with the water to produce a weak carbonic acid. The ocean gradually becomes less alkaline and the level of carbonate is reduced. However, calcium carbonate is required by organisms, such as corals and shellfish, to build skeletons and shells. Some estimates suggest the oceans have become 30 percent more acidic since the Industrial Revolution. And if CO2 continues to be emitted at the same rate by 2100, acidity will increase by about 150 percent.

Continue reading ‘Team investigates effects of acidification on marine ecosystem’

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Ocean acidification in the IPCC AR5 WG II

OUP book