Cumberland Basin, located at the head of Chignecto Bay, Bay of Fundy, exhibits a seaward (exponential) decreasing, time-dependent, surface sediment concentration. There is a strong correlation between suspended sediment concentration and longitudianal concentration gradient. A similar correlation was found in Shepody Bay, Chignecto Bay, and Minas Basin, suggesting that an equilibrium condition exists between the two variables. Total suspended mass in Cumberland Basin was constant over 2 years of observation (1011 g) despite changes in sediment concentration and concentration gradient. Temporal controls on suspended sediment concentration are river influx, ice melting dispersion, settling on the intertidal mud flats, and water mass exchange at the mouth of the basin. This exchange is due to cross-channel velocity variations; exchanges due to tidal current asymmetry and settling lag are small. A simple box model was developed to study the temporal variation of total suspended sediment in the basin. The results show that the water mass exchange at the basin mouth varies with time and is the dominant factor controlling suspended mass due to to efficient dampening of temporal fluctuations in suspended mass. ¿ American Geophysical Union 1989