Collaborative Research: Uncovering the role of planktic foraminifera in marine snow formation and ocean carbon export

Healthy oceans provide benefits to the American people by supporting fisheries, coastal economies, climate regulation, and marine ecosystems that sustain biodiversity. One of the ocean's most important roles in Earth’s carbon cycle is the transport of carbon from surface waters to the deep sea, where it can be stored for long periods. Tiny marine organisms called planktic foraminifera are well known for producing calcium carbonate shells, but their role in transporting organic carbon remains poorly understood. Recent observations suggest that these organisms actively collect, transform, and release large particles known as marine snow, which are a major vehicle for carbon export to the deep ocean. This project investigates how planktic foraminifera interact with marine snow and whether these interactions influence the amount of carbon transported below the ocean surface. This research combines laboratory experiments, field-collected specimens from both US coasts, and geochemical analyses to examine how foraminifera aggregate particles and alter their chemical composition. This project improves understanding of ocean carbon cycling, provides training opportunities for undergraduate and graduate students, and strengthens connections between scientists and coastal communities. Planktic foraminifera are globally distributed calcifying rhizarians that contribute substantially to the export of inorganic carbon through the sinking of their calcium carbonate shells. In contrast, their role in inorganic carbon export and the biological carbon pump remains poorly constrained. Recent observations indicate that many planktic foraminifera actively aggregate, transform, and release large particulate matter, suggesting a previously unrecognized pathway through which these organisms may influence marine snow formation and carbon export. This project evaluates the interactions between planktic foraminifera and particulate organic matter to determine how these interactions contribute to marine snow formation, transformation, and export. Laboratory cultures of foraminifera collected from waters off both the northwestern in southeastern United States will be used to quantify particle selectivity, aggregation behavior, and the time scales over which particle-foraminifera interactions occur. Experiments assess whether foraminifera preferentially aggregate specific particle types and how aggregation and transformation alter the sinking and export potential of particulate matter. Geochemical tracer analyses further examine whether interactions with marine snow modify the chemical composition of foraminiferal organic matter and shells. These measurements provide mechanistic insight into the pathways linking foraminifera, particular organic matter, and carbon export, while enabling inferences about interactions occurring in natural populations. These results constrain the contribution of planktic foraminifera to the biological carbon pump and address a major gap in understanding the ecology of non-spinose foraminifera and other large rhizarians associated with marine snow. By improving knowledge of carbon export processes this work advances understanding of ocean carbon cycling and its role in regulating Earth’s interconnected ocean and atmospheric systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.