Tag Archives: ocean acidification

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New Sensor Monitors Ocean Acidification

Scientists and engineers have achieved the first step in developing a cost-effective micro sensor for long-term monitoring of ocean acidification.

The new technology, that will measure pH levels in seawater, was developed by engineers from the National Oceanography Centre, in close collaboration with oceanographers from University of Southampton Ocean and Earth Science, which is based at the centre.

The team tested the new device aboard the RRS Discovery and published their results in Anaytica Chimica Acta. The sensor can currently be used for on-board analysis of seawater samples, but they hope that it will eventually be deployed for long periods of time in the ocean, taking in situ measurements.

Ocean acidification is occurring as a consequence of rising levels of atmospheric carbon dioxide (CO2), which is absorbed by the oceans. When it dissolves in seawater, CO2 forms a mild acid, which is decreasing ocean pH globally and could impact marine ecosystems. “We need to monitor seawater pH to a high level of precision and accuracy, and over long periods of time, in order to detect changes in the carbon system,” says Dr Victoire Rérolle, lead author and researcher with NOC’s Sensors group.

The sensor works on the same principles as litmus paper that many people may have used in chemistry lessons at school, whereby the colour changes depending on the acidity of the solution.

“The microfluidic chip within the sensor has great advantages because it is robust, small, reasonably cheap to produce and uses small amounts of reagents – which is really key for in situ deployment where it may be collecting data at sea for long periods of time.

“The sensor uses a dye which changes colour with pH. The dye is added to the sample, then the colour is measured using an LED light source and a device called a ‘spectrometer’. The microfluidic element simply describes the component needed to mix the seawater sample with the dye and the cell to measure the colour.”

As well as monitoring global change, the sensors can be used to measure more localised human impact. The micro sensors could be deployed to detect leakages from carbon capture and storage sites – whereby CO2 is artificially removed from the atmosphere and stored in subsea reservoirs – by measuring any proximal fluctuations in pH. The oil industry is also interested in this technology for monitoring seawater acidity around drilling sites.

Collaborating institutes were the National Oceanography Centre, University of Southampton Ocean and Earth Science, the Norwegian Institute for Water Research, the Uni Bjerknes Centre Norway and the University of Bergen.

Australia pushes for ban on ocean “fertilisation”

Australia said it was pushing for a ban of any commercial use of a pioneering technique to reduce the impacts of climate change by “fertilising” the world’s oceans with iron, according to a report by the Sydney Morning Herald.

The practice is proposed as a way to increase carbon dioxide absorption in the ocean and boost fish stocks. It rose to prominence last year when a fishing boat chartered by an American entrepeneur strewed 100 tonnes of iron sulphate into the ocean off western Canada. The iron was meant to increase plankton, boost salmon populations and sequester carbon. Whether the ocean responded as hoped is not clear.

In response, Australia has joined South Korea and Nigeria in trying to ban commercial ocean geo-engineering projects by moving a legally binding amendment to the London Protocol – an international treaty countering dumping-related ocean pollution.

University of Tasmania Associate Professor Peter Strutton said the increased phytoplankton would absorb more carbon dioxide from the atmosphere. When the phytoplankton dies it sinks to the bottom of the ocean taking some carbon dioxide with it.

”It might take more CO2 out of the atmosphere, make the surface ocean more productive – which might help feed more fish – and perhaps store more carbon on the bottom of the ocean in sediments,” Professor Strutton said.

But ocean fertilisation could also have unintended consequences, such as causing damaging toxic algae blooms, increasing ocean acidification, and depleting oxygen in deep waters. So far there have been more than a dozen formal scientific trials, with mixed results.

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Scientists Warn of Unprecidented Marine Exctinctions

Scientists are warning that marine species are at risk of entering a phase of extinction unprecedented in human history.

A preliminary report arising from a ‘State of the Oceans’ workshop held at the University of Oxford in April, is the first ever to consider the cumulative impact of all pressures on the oceans. Considering the latest research across all areas of marine science, the workshop examined the combined effects of pollution, acidification, ocean warming, over-fishing and deoxygenation.

The scientific panel concluded that the combination of stresses on the ocean is creating the conditions associated with every previous major extinction of species in Earth’s history. And the speed and rate of degeneration in the ocean is far greater than anyone has predicted. As a result, although difficult to assess, the first steps to globally significant extinction may have begun with a rise in the extinction threat to marine species such as reef-forming corals.

“The findings are shocking,” says Dr Alex Rogers, Scientific Director of the International Programme on the State of the Ocean (IPSO) which convened the workshop. “As we considered the cumulative effect of what humankind does to the ocean, the implications became far worse than we had individually realized. This is a very serious situation demanding unequivocal action at every level. We are looking at consequences for humankind that will impact in our lifetime, and worse, our children’s and generations beyond that.”

Marine scientists from institutions around the world gathered at Oxford University under the auspices of IPSO and the IUCN. The group reviewed over 50 of the most recent research papers by world ocean experts and found firm evidence that the effects of climate change, coupled with other human-induced impacts such as over-fishing and nutrient run-off from farming, have already caused a dramatic decline in ocean health.

Increasing hypoxia and anoxia (absence of oxygen, known as ocean dead zones) combined with warming of the ocean and acidification are the three factors which have been present in every mass extinction event in Earth’s history.

There is strong scientific evidence that these three factors are combining in the ocean again, exacerbated by multiple severe stresses. The panel concluded that a new extinction event was inevitable if the current trajectory of damage continues, and could be said to have already begun.

The report concludes that “Unless action is taken now, the consequences of our activities are at a high risk of causing, through the combined effects of climate change, overexploitation, pollution and habitat loss, the next globally significant extinction event in the ocean. It is notable that the occurrence of multiple high intensity- stressors has been a prerequisite for all the five global extinction events of the past 600 million years.”

It highlights these keypoints:
- Human actions have resulted in warming and acidification of the oceans and are now causing increased hypoxia.
- The speeds of many negative changes to the ocean are near to or are tracking worst-case scenarios. Some are as predicted but many are faster than anticipated and accelerating.
- The magnitude of the cumulative impacts on the ocean is greater than previously understood.
- Timelines for action are shrinking: the longer the delay in reducing emissions, the higher the annual reduction rate will have to be and the greater the financial cost.
- Resilience of the ocean to climate change impacts is severely compromised by other stressors from human activities, including fisheries, pollution and habitat destruction.
- The extinction threat to marine species is rapidly increasing.

The authors also give a solution, but comment that society’s values are a barrier to implementing what needs to be done.
- Reduce CO2 emissions
- Reduce fishing to sustainable levels
- Establish a global system of marine protected areas.
- Reduce pollution
- Avoid, reduce or at least strictly regulate oil, gas and mineral extraction
- Assess, monitor and control other uses of the marine environment such as renewable energy schemes
- Activities to proceed only if they are shown positively not to harm the ocean
- UN global body to ensure compliance with the UN Convention on the Law of the Sea

Further Reading:
Summary of the conclusions and recommendations of the international Earth system expert workshop on ocean stresses and impacts
Multiple ocean stresses threaten “globally significant” marine extinction