Amos, C.L.; Brylinsky, M.; Forbes, D.L.; Robertson, A.; Thompson, C.E.L., and Kassem, H., 2018. Stability of seabed sediments in the embayments of North Rustico, Prince Edward Island, Canada.
This paper describes a series of 15 deployments of the annular benthic flume Sea Carousel made along the two estuaries of North Rustico, Prince Edward Island (PEI), Canada: The Hunter River estuary and the Wheatley River estuary. The study was part of a wider study on the environmental impact of coastal changes and aquaculture (Mytilus edulis) development in the region. The study site was situated on the dynamic north shore of PEI that is characterised by sandy barrier islands, inlets and beaches, and muddy lagoons. The lagoons are dominated by the seagrass Zostera marina in the muddy outer parts and by Ulva lactuca in the eutrophic inner parts. The thresholds for surface erosion of cohesive sediments (0.10 < τcrit,o < 0.75) derived from trends of suspended sediment concentration (C) increased with distance (d) into the estuary: τcrit,o = 0.50e−0.26d (±0.05) Pa. Location in the estuary is the best predictor of bed stability. The next best predictor is surface sediment wet bulk density (ρb), which takes the form: τcrit,o = 6.67 × 10−4(ρb) − 0.55 Pa. Erosion rates (E) can only be correlated (significantly) with excess bed shear stress (τex) by incorporation of a time (depth)-varying erosion threshold. A power function emerged of the form: E = Eoτexm kg/m2/s (0.28 < m < 1.06). The exponent is within the range of laboratory experiments reported in the literature. The still-water settling rates of eroded material are diagnostic of a wide range of sedimentation diameters varying from fine sand to medium silt. The deposition threshold (τd) was evaluated in a laboratory equivalent of Sea Carousel (Lab Carousel) for sites RUS11 and RUS12 and yielded a mean value of 0.51 Pa. The exponential decay constant (k) for still-water settling is strongly dependent on initial concentration and suggests a constant settling rate that fits with data from a wide variety of settings throughout Canada.
