Great Bay Sediments

Primary tabs

What happens to the nutrients that have accumulated in the sediments of the Great Bay? Quantifying nutrient release and removal due to diffusion and sediment resuspension

Linda Kalnejais, Assistant Professor of Oceanography, UNH (603.862.1008); Diane Foster, Associate Professor of Mechanical Engineering, UNH (603.862.3089); and Thomas Lippmann, Research Associate Professor of Coastal and Ocean Mapping (603.862.4450)

The Great Bay Estuary has experienced a growth of nuisance primary producers, including macroalgae and epitphytes, and a decline in ecosystem health, due in large part to increasing nutrient inputs. Although nutrients often enter the system from various sources within the watershed, new research indicates that Great Bay sediments are a significant internal source of nutrients that fuel phytoplankton growth. It is important to understand the mechanisms driving the nutrient release from the sediments and obtain an accurate quantification of the loading in order to obtain a more complete picture of nutrient sources in the bay.

Kalnejais and collaborating researchers will expand upon their previous NHSG-funded research to estimate the net nutrient load from sediments in the spring and fall over the entire Great Bay. Using various field and laboratory experiments, they will determine how eelgrass and various seafloor types in the bay influence the diffusive flux of nutrients to or from the sediments. They will measure nutrient release using core incubations, porewater profiles and erosion chamber experiments at sites along an estuary-wide transect. Researchers will also measure fluid shear stresses using acoustic Doppler profilers across the bay.

This research will provide resource managers with a more accurate assessment of all major nutrient sources within the Great Bay Estuary to more effectively manage the ecosystem’s health and improve water quality in New Hampshire’s estuaries.