April 8, 2026 — Scientists have found a new way to detect subtle chemical signatures in seawater—revealing previously invisible details about the ocean’s chemistry from data continuously collected by thousands of autonomous robotic floats drifting across the seas.
A University of Miami Rosenstiel School for Marine, Atmospheric, and Earth Science-led research team applied a new approach they developed to detect subtle chemical signatures in seawater, revealing that nitrogen cycling in parts of the ocean with very little oxygen, known as oxygen-deficient zones, is far more dynamic than previously thought.
“Understanding when and where nitrogen loss occurs is critical because it governs ocean productivity, the global carbon cycle, and even atmospheric greenhouse gas balance.” said the study’s lead author Mariana Bif, an assistant professor in the Department of Ocean Sciences at the Rosenstiel School.
Using the new method, the team extracted previously unresolved chemical signals in seawater—specifically nitrite and thiosulfate—from ultraviolet (UV) spectra collected by nitrate sensors on Biogeochemical-Argo (BGC-Argo) floats. This approach enables the detection of these key intermediates molecules from datasets originally developed to detect only nitrate.
The float recorded vertical profiles of oxygen, nitrate, pH, and bio-optical properties about every ten days in waters of the Eastern Tropical North Pacific. By reconstructing nitrite concentrations from the UV spectra and combining them with the other measurements in a biochemical model, the researchers were able to resolve how nitrogen cycling pathways varied over time and depth. The model also enabled quantification of the relative contributions of different microbial processes in low-oxygen waters.