Factors affecting sedimentation rates of a tidally influenced salt marsh in Plum Island Sound, MA McDonald Lee Advisor: Dr. Carl Friedrichs Graduate Assistant: Lynsey Ellis Funding: National Science Foundation Grant DEB

Overview Background TIDE Project Purpose Methods Conclusions

Tidally influenced marsh morphology What is a tidal marsh –Intertidal, vegetated transitional zone between terrestrial and marine ecosystem Sedimentation –Fine-grained particles transported and deposited on marsh surface due to a decrease in water velocity Previous studies determined controlling factors –Concentration of sediments –Vegetation cover –Elevation/duration of inundation –Distance from source

TIDE: Trophic cascades and Interacting control processes in a Detritus-based aquatic Ecosystem 4 year project “Top-down” or “Bottom-up” –Removal of key species –Addition of Nutrients Create models (from Deegan et al., 2002)

Plum Island Sound, MA (from Deegan, 2003)

Purpose of Research What factors (besides top-down/bottom-up control) influence sediment deposition in the Plum Island Sound marshes? To what extent do each of the factors have on total sediment deposition? To determine the control of sedimentation rates for the larger TIDE project Questions

Methods Sampling Sites –2 marshes 3 transects –3 sampling stations Vegetation –Random sampling Using a fixed sample area Count stalks Record species type –Spartina alterniflora –Spartina patens Distance from source and elevation –Total station –Kinematic GPS system

More Methods Duration of inundation –Tide height via pressure sensor (CTD) Sediment concentration –Water samples Filter and dry sample –Backscatter sensor Total sediment deposited –Ceramic sediment traps Analyzing the data –Multiple linear regression y = b 1 x 1 + b 2 x b n x n + c

Conclusions What do I expect to see? –Vegetation will play a key role in determining sedimentation rates. Thicker vegetation will result in higher deposition of sediments. –The distance from source will have significant impacts, showing that points further from the source will experience less deposition due to lower sediment concentration. –The time of inundation will result in a trend where submerged areas of the marsh receive greater loads of sediments. Higher elevations will consequently have less sediment deposited.

Conclusions The extent of impact each factor has on sedimentation is unknown. Any variations between the factors in the two marshes will assist in the interpretation of the data of the TIDE experiment.