DANCE - eDdy-mediated mechAnisms supplying Nitrogen resourCEs
Lead Research Organisation:
NATIONAL OCEANOGRAPHY CENTRE
Abstract
Subtropical gyres, vast rotating regions of the ocean, play a vital role in regulating Earth’s climate by absorbing and storing large amounts of atmospheric CO2. The North Atlantic Subtropical Gyre (NASG) alone accounts for up to 15% of global oceanic CO2 uptake. However, this natural carbon sink is increasingly under threat. As ocean temperatures rise, nutrient availability—particularly nitrogen—is declining in the NASG, putting its long-term capacity to support marine ecosystems and sequester carbon at risk.
One key, yet underexplored, mechanism helping to sustain productivity in this region is the formation of mesoscale eddies—large, swirling ocean currents generated as the Gulf Stream (GS) separates from the continental margin of the North American East Coast. These eddies, which can span tens to hundreds of kilometres, act as mobile biogeochemical engines. By transporting nitrogen-rich coastal waters and diverse microbial communities into the nutrient-poor interior of the NASG, they stimulate phytoplankton growth and enhance carbon uptake.
Recent work by our team has revealed an important biological dimension to this process: eddies do not simply move nutrients, they also carry active nitrogen-fixing microbes. These microbes convert atmospheric nitrogen gas into forms usable by marine life—a process known as nitrogen fixation. This pathway is particularly significant because it supports biological productivity without upwelling CO2-rich deep water, making it an especially efficient contributor to oceanic carbon sequestration. Within eddies, nitrogen fixation rates can be up to 17 times higher than in surrounding waters.
Despite their importance, the full life cycle of GS eddies—and how their physical and biological dynamics interact to influence nitrogen delivery—remains poorly understood. Observations show that eddies initially stimulate productivity, as indicated by elevated chlorophyll concentrations. As nutrients are consumed, this productivity declines—only to rebound weeks later, likely driven by nitrogen-fixing organisms adapted to nutrient-depleted conditions. These patterns suggest a complex succession of microbial communities and processes unfolding over several months.
We hypothesise that the interaction between physical and biological processes throughout the life of a GS eddy fundamentally shapes the quantity and form of nitrogen delivered into the NASG. To investigate this, we will observe and reconstruct the biological and biogeochemical evolution of individual eddies, quantify nitrogen contributions driven by both microbial activity and physical transport, and assess the net delivery of nitrogen into the gyre from the regional population of GS cyclonic eddies.
This project will integrate satellite observations, autonomous platforms, and novel eddy-tracking methods to follow eddies over their full multi-month evolution. In doing so, the research will provide vital insights into how changing mesoscale circulation patterns—projected to intensify with climate change—may alter the ocean’s capacity to absorb carbon. The outcomes will inform next-generation climate models and guide community efforts to better predict and protect one of Earth’s most critical climate-regulating systems.
One key, yet underexplored, mechanism helping to sustain productivity in this region is the formation of mesoscale eddies—large, swirling ocean currents generated as the Gulf Stream (GS) separates from the continental margin of the North American East Coast. These eddies, which can span tens to hundreds of kilometres, act as mobile biogeochemical engines. By transporting nitrogen-rich coastal waters and diverse microbial communities into the nutrient-poor interior of the NASG, they stimulate phytoplankton growth and enhance carbon uptake.
Recent work by our team has revealed an important biological dimension to this process: eddies do not simply move nutrients, they also carry active nitrogen-fixing microbes. These microbes convert atmospheric nitrogen gas into forms usable by marine life—a process known as nitrogen fixation. This pathway is particularly significant because it supports biological productivity without upwelling CO2-rich deep water, making it an especially efficient contributor to oceanic carbon sequestration. Within eddies, nitrogen fixation rates can be up to 17 times higher than in surrounding waters.
Despite their importance, the full life cycle of GS eddies—and how their physical and biological dynamics interact to influence nitrogen delivery—remains poorly understood. Observations show that eddies initially stimulate productivity, as indicated by elevated chlorophyll concentrations. As nutrients are consumed, this productivity declines—only to rebound weeks later, likely driven by nitrogen-fixing organisms adapted to nutrient-depleted conditions. These patterns suggest a complex succession of microbial communities and processes unfolding over several months.
We hypothesise that the interaction between physical and biological processes throughout the life of a GS eddy fundamentally shapes the quantity and form of nitrogen delivered into the NASG. To investigate this, we will observe and reconstruct the biological and biogeochemical evolution of individual eddies, quantify nitrogen contributions driven by both microbial activity and physical transport, and assess the net delivery of nitrogen into the gyre from the regional population of GS cyclonic eddies.
This project will integrate satellite observations, autonomous platforms, and novel eddy-tracking methods to follow eddies over their full multi-month evolution. In doing so, the research will provide vital insights into how changing mesoscale circulation patterns—projected to intensify with climate change—may alter the ocean’s capacity to absorb carbon. The outcomes will inform next-generation climate models and guide community efforts to better predict and protect one of Earth’s most critical climate-regulating systems.