Where oceanography meets engineering to protect the oceans

Did you know the ocean absorbs around a third of the carbon dioxide we release into the atmosphere? As well as slowing down climate change, this absorption causes ocean acidification, which can harm marine ecosystems. Through her research, PhD student Molly is building a sensor to improve our understanding of this phenomenon to help protect our oceans.

Fortunately, the ocean has a natural capacity to resist acidification:  alkalinity, which works in a similar way to when you take an antacid. In your stomach, the antacid neutralises the carbonic acid, helping it maintain a stable pH.

“In the oceans, bicarbonates and carbonates react with hydrogen ions released when carbon dioxide dissolves in sea water, stabilising the fragile pH balance that supports marine life by preventing excessive acidity,” Molly explains.

Molly, who is in the fourth year of her PhD, has created a sensor that measures alkalinity in marine environments where the pH changes rapidly, such as estuaries, coral reefs and phytoplankton blooms.

“I’ve always been interested in ocean acidification, and my PhD has allowed me to continue looking into the carbon biogeochemistry of the ocean, while developing skills in autonomous sensors and engineering,” says Molly, who went on to start her PhD after completing a master’s in Oceanography with French at Southampton. 

Tackling a global problem one droplet at a time 

Molly used a process known as droplet microfluidics: chemical reactions in tiny droplets of water that are measured within the sensor. The sensors are deployed in various locations in the ocean. This enables researchers to measure changes in alkalinity, over a matter of minutes: much faster than was previously possible and producing less waste than currently available sensors.

“My sensor performs three individual measurements known as titrations to find out the acid concentrations across a wide range of the ocean. It works on a ‘Goldilocks principle’: one titration will be too acidic, one titration will be too basic, and one will be ‘just right’,” explains Molly.

This data will help researchers to show which ecosystems are naturally resilient against acidification and which might need further support, through interventions such as alkalinity enhancement. This is where bicarbonates and carbonates are artificially added to seawater to improve how much carbon dioxide the water can take in, and crucially, lock away. 

Creating change by working across subject areas

At Southampton we enable our people to work across disciplines, bringing unique perspectives together to solve global issues.

This approach was essential for Molly’s project. The collaborative research culture within the Southampton Marine and Maritime Institute (SMMI) allowed her to combine the droplet microfluidic sensor, developed by Adrian Nightingale at the University with the alkalinity microfluidic sensor developed by Allison Schaap at the National Oceanography Centre.

“Being able to work at the interface between oceanography and engineering has given me a valuable insight into what working in academia and research would be like. I’ve had access to some of the most advanced research in the world, highly knowledgeable researchers, and an incredibly supportive postgraduate community,” says Molly.

Molly is now applying for post-doctoral positions around the world to continue this interdisciplinary theme between the marine carbonate system and ocean sensors.