First Ocean Alkalinity Monitor Deployed Off Nova Scotia

*TL;DR: In August 2025 a Duke University mass spectrometer was installed in Halifax Harbour to monitor the world’s first coastal ocean alkalinity enhancement project, providing the first continuous measurements of how added minerals affect seawater chemistry and marine microbes.*

Context The ocean has absorbed roughly one‑third of anthropogenic CO₂ since the Industrial Revolution, slowing global warming. Scientists are now testing whether deliberately raising seawater alkalinity can boost that natural sink. The pilot, run by Planetary Technologies, injects crushed alkaline minerals into the cooling‑water discharge of a natural‑gas power plant in Halifax Harbour, Nova Scotia.

Key Facts - In August 2025 researchers from Duke University’s Cassar Lab placed a custom mass spectrometer on a dive‑boat laboratory. The instrument draws seawater through tubing, extracts dissolved gases, and quantifies them with a mass‑to‑charge detector. Continuous readings reveal the balance between photosynthesis (CO₂ uptake) and respiration (CO₂ release) by microbes. - The same team used a Gopticas sensor, which measures light‑induced oxygen production to estimate photosynthetic rates. Both devices were operated from a makeshift lab built in the boat’s cabin, with wiring and tubing assembled on‑site. - Early observations showed a visible alkaline plume spreading from the discharge pipe. The researcher on deck described the sight as “awe‑inspiring” but emphasized that the plume represents only a tiny fraction of the global ocean. - Preliminary data indicate a modest rise in dissolved inorganic carbon uptake, on the order of 0.2 µmol kg⁻¹ day⁻¹, compared with baseline levels of 1.5 µmol kg⁻¹ day⁻¹. The increase aligns with laboratory models predicting that each kilogram of added limestone can raise seawater alkalinity by about 0.1 mmol kg⁻¹. - The findings will be detailed in an upcoming paper in *Environmental Science & Technology* and uploaded to the open‑access Ocean Carbon Data Initiative.

What It Means The deployment marks the first real‑time, in‑situ monitoring of a marine carbon‑dioxide‑removal (mCDR) effort. Continuous gas measurements allow scientists to quantify how much atmospheric CO₂ is being pulled into the sea and stored as stable carbonate minerals. If scaling proves feasible, alkalinity enhancement could complement land‑based removal methods, which are limited by space and ecosystem trade‑offs.

Looking Ahead Future work will expand the sensor network to multiple sites and compare chemical changes with long‑term ecological impacts. Tracking these variables will be crucial to determine whether ocean alkalinity can move from experimental pilot to climate‑policy tool.