Collaborative Research: MRA: ConFines: Continental-scale study of the role of fine particles in riverine material fluxes

Streams and rivers move more than water and the material dissolved in it—they also carry a complex blend of small particles, collectively called seston. Seston typically includes silt, clay, organic material, and microbes that originate from the surrounding land or that are produced within the stream itself. While the significance of seston transported by streams can be seen in a muddy river after a rainstorm, the function of these particles in streams remains poorly understood.

However, as seston moves downstream it can serve many crucial roles, including as food and energy for stream animals and as a source of the life-building elements carbon, nitrogen, and phosphorus for coastal ecosystems. Using field samples and high-frequency water quality data from environmental sensors at National Ecological Observatory Network (NEON) sites, this project will increase our understanding of the role of fine particles as they travel in streams.

Results from the project will help to refine estimates of carbon, nitrogen, and phosphorus carried from the land to the coast by riverine particles. These data can be used to inform global earth-system models. Undergraduate and graduate students will participate in this research.

NEON data will be used to introduce data-science techniques, computer modeling, and graphical analysis into several undergraduate courses and educational modules developed by the team will be made publicly available.

The role and importance of seston in flowing waters is underappreciated, both because of its diverse composition and because of challenges associated with robust sampling capable of capturing spatial and temporal dynamics. This project will increase understanding of riverine seston composition as well as how seston couples carbon, nitrogen, and phosphorus transport in rivers.

The team will test three complementary hypotheses that will expand understanding of the role of seston in riverine fluxes: 1) seston composition depends on continental-scale patterns in geology and climate; 2) seston is an integrated signal of terrestrial and in-stream biogeochemical processes that varies according to seasonal or hydrologic context; and 3) seston quantity and quality will reveal river network-scale processes that connect headwaters to larger rivers. This project will leverage new and ongoing data collection efforts at 22 wadeable-stream and river NEON sites to measure seston quality and quantity.

These data will be used to develop predictive models for seston composition and transport across seasons, hydrologic conditions, and NEON domains. By shedding light on the role of seston in riverine carbon and nutrient biogeochemistry at the local, regional, and continental scale, the work proposed here will provide key data needed to parameterize models that further define the role of rivers in global biogeochemical cycles.

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.