 Observers of the oceans include scientists, regulators and industries (such as aquaculture, fisheries and offshore energy) and they all require high quality data to understand, effectively manage and sustainably exploit the oceans’ resources. Whilst physical data (such as currents, temperature, salinity, wind and waves) are vital for their priorities (such as climate change, weather prediction or safety at sea) these measurements can largely be made with existing sensor technologies which could be applied to autonomous vehicles.
In contrast, the measurement of ocean chemistry and biology is far less mature with few instruments available commercially - and many of these are unsuitable for use on autonomous vehicles. Yet these measurements are required to understand and manage pollution, the effects of elevated atmospheric CO2 and climate change, as well as the impact on biodiversity, ecosystems and natural processes from human activities and exploitation of ocean resources.
Filling the gap
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The Oceanids sensors projects aim to fill that gap by developing robust, high performance and mature technologies that can measure a range of key ocean chemical and biological parameters and are suitable for integration with autonomous vehicles
Further, the maturity of these sensors is being demonstrated by integrating them with the autonomous vehicle fleet in the UK's National Marine Equipment Pool (NMEP), and performing technical trials and science demonstration missions. This will deliver Technology Readiness Level (TRL) 8 ('operational') systems that can in the future be made accessible to the UK science community and other stakeholders. |
The Oceanids sensors projects target benthic biology and habitats (BIOCAM led by University of Southampton), primary productivity of phytoplankton (STAFES-APP: University of Southampton, Chelsea Technologies Group Ltd, NOC), CO2 exchange across the ocean-air interface (CaPASOS: University of Exeter, NOC, Plymouth Marine Lab), Nutrients (AutoNutS: NOC and University of Southampton) and the ocean carbonate system / the effects of increased CO2 in the ocean (CarCASS, NOC, University of Southampton, ANB Sensors Ltd.).
 Targeting two of the highest scientific priorities for chemical measurement in ocean waters, this project has optimised the performance of existing NOC sensor technology to produce six new operational devices for measuring nutrients and micronutrients. The data gathered using these sensors will be crucial to advancing our knowledge of how marine ecosystems work, how productive they are and how they respond to climate change, exploitation and ecosystem management. These 'Lab-On-Chip' (LOC) miniaturised laboratories are able to perform seawater chemical analysis using small samples of seawater and chemical reagents to help create more complete low-cost ocean chemistry datasets.
The project has developed sensors that can be deployed on the NMEP autonomous fleet to measure phosphate, silicate and iron to TRL 7 ('mature and delivering science') and created new sensors for ammonia (TRL 5: 'prototype in simulated environment') and trace concentration iron (TRL 4/5) with the latter two being rapidly developed to be at TRL 7 or 8 by the end of the project. This builds on the existing mature nitrate / nitrite sensors (TRL 9) enabling comprehensive measurement of nutrients and micronutrients on autonomous vehicles or in low infrastructure settings.
'Extremely robust'
These LOC sensors employ microfluidics (channels of ~150 mm in width) in polymer 'chips' (manifolds with fluidics and optical structures). They use microvalves mounted on the chip and highly accurate miniature pumps to mix seawater with chemical reagents that produce a change in colour (absorbance), fluorescence or luminescence intensity related to the target chemical concentration. This optical signal can be read electronically giving results within minutes. The devices use components that can withstand deep sea pressures, while bathing the components in oil within a housing ensures no local stresses build up even at extreme depths. As a result the devices are extremely robust and are depth rated to 6000m (60 MPa).
Deployments
Through this project - and enabled by other projects running in parallel - there have been a large number of successful deployments in a wide range of settings, from coast to deep ocean. These include seven AutoNutS sensors onboard Autosub Long Range and one integrated with a Teledyne Webb Slocum glider for the Oceanids trials in Loch Ness in 2019.
Other deployments have included: profiling to >4800m in the region of the Porcupine Abyssal Plain; >6 months of Silicate data from a mooring in the Southern Ocean (Ocean Observatories Initiative (OOI) Global Southern Ocean Array); and a 120 km transect in the northern North Sea onboard a Kongsberg Seaglider equipped with a phosphate LOC. The associated data are being prepared for publication, adding to the considerable body of literature documenting some of the 200+ successful deployments of the LOC platform.
Challenges remain and are the current focus of the development team. These include a revision of the platform technology to include new low power valves (that have been successfully demonstrated in tests during AutoNutS) as well as faster measurements. This is in addition to the focus on ammonia and trace iron sensor development, preparing them for the upcoming trials and science demonstration deployments.
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 Focusing on the highest scientific priority for chemical measurement - the effects of CO2 in water - this project is delivering the first integrated sensor for pH, Dissolved Inorganic Carbon (DIC) and Total Alkalinity (TA) that can operate from the surface to full ocean depth.
Developed in partnership with ANB Sensors, the NOC's CarCASS technology will be used to improve our understanding of the ocean’s rapidly changing CO2 reservoir, as well as monitor ocean acidification in areas of significant ecosystem and commercial importance such as coral reefs, shell fishing areas and in mariculture. The sensor will also be a powerful tool for monitoring sub-seafloor carbon storage reservoirs due to its ability to detect carbon dioxide leaks during and after gas injection into an offshore (subseabed geological) store.
Despite the impact of the Covid-19 pandemic, CarCASS has achieved many of its key deliverables and the project team are currently preparing for trials and science demonstration activities in 2021.
'Complete characterisation'
Central to the CarCASS concept is that using multiple sensors together enables a complete characterisation of the ocean carbonate system, and using a combination of fast and slower but more accurate sensors enables this to be done accurately and at high speed.
To constrain the seawater carbonate system (which includes the carbonate ion (CO32+), bicarbonate ion (HCO3+ ), carbonic acid (H2CO3) concentrations and saturation states of calcite and aragonite (Ωcalc, Ωarag)) two of the four master parameters (TA, DIC, partial pressure of carbon dioxide (pCO2) and pH must be measured, along with temperature and salinity. Pairings of pH with either TA and DIC yield the smallest uncertainty which is why CarCASS targets these parameters.
For 'climate' quality observations the carbonate ion (CO32+) concentrations must be determined with a relative uncertainty of 1% which requires uncertainty of about 0.003 units in pH and 2 µmol kg-1 in DIC and TA, which is why CarCASS has developed ultra high performance pH, TA and DIC sensors based upon Lab-on-Chip (LOC) technology. However, these sensors are slow and therefore to determine the carbonate system at high resolution an additional fast pH sensor (developed by partners ANB Sensors Ltd) is used, as well as estimates of TA using fast salinity sensors and known approximate relationships between TA and salinity. In this way fast estimates of TA can be periodically calibrated with slower but more accurate measurements.
Recent progress
The project has delivered demonstrations of all three LOC sensors together and separately. All of the LOC sensors use small (~150 µm) channels, microvalves and pumps to sample and process small volumes of seawater and reagents which create a measurable signal in a pH dye (pH and TA sensors) or in conductivity of a receiving solution (DIC). Currently the individual LOC sensors have reached Technology Readiness Level (TRL) 8 (pH), TRL 6/7 (TA) and TRL 6 (DIC). The fast pH sensor from ANB has reached TRL 6.
Deployments have included: trials of all CarCASS sensors onboard Autosub Long Range in Loch Ness; pH on a deep descending (~4800 m) sensor frame in the region of the Porcupine Abyssal Plain; and pH, TA and DIC multiple times in the North Sea in the region of the Goldeneye Platform as part of the STEMM-CCS project which is developing capability for monitoring Offshore Carbon Capture and Storage.
Currently the team are implementing an algorithm and associated software and hardware to integrate the individual sensors into the combined CarCASS instrument whilst progressing the TRL of a combined TA / DIC sensor and LOC and ANB pH sensors.
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 Join Dr Kate Hendry and Dr Eleanor Frajka-Williams on 27 January 2021 for the first Net Zero Oceanographic Carbon (NZOC) project workshop, 'The 21st Century Marine Scientist - Delivering science in a net zero world'. Here you will have the opportunity to discuss the multiple science drivers that will help to shape future UK oceanographic research directions and infrastructure investment over the next 15 years, and how investment decisions may also be shaped in turn by the need for sustainability and a low carbon footprint.
Find out more about the workshop, and how to register your interest here.
National Marine Equipment Pool
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The National Marine Equipment Pool (NMEP) is the largest centralised marine scientific equipment pool in Europe with a diverse range of cutting-edge scientific instruments and equipment capable of sampling from the sea surface to the deep ocean.
Equipment held within the NMEP is available for use by the marine science community. Contact us to find out about commercial hire of our instruments and vehicles, as well as future use of sensors, platforms and other Oceanids technologies.
Further details are available in the National Marine Facilities Technology Roadmap 2020-21, which outlines the current capabilities of the fleet, and looks to the future of marine science and the technology that will take us there.
Head to https://bit.ly/NMF_TRM to view or download a copy. |
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