A 2-year record of monthly observations of suspended material concentrations at a network of 11 stations in eastern Long Island Sound is used to detail the characteristics of the concentration field and the factors governing its variability. These suspended material distributions display a high degree of spatial and temporal variability, there being only weak correlation between concentrations and concurrent salinity. This behavior contrasts sharply with observations in other regions of the sound. To determine the relative importance of hydrodynamic, meteorological, and biological factors, an ensemble average of selected station data is introduced. This average displays a seasonal variability that can be represented by the combined effects of streamflow and wind stress. Streamflow serves to produce a persistent background concentration. The occurrence of higher frequency fluctuations due to aperiodic discharge events appears limited by the volume and mixing characteristics of the eastern sound. Wind events will dominate the concentration field if high stress levels are maintained for more than 48 hours. Duration requirements are most commonly satisfied during the winter months. Materials introduced by streamflows and wind stress are distributed by the high energy tidal stream. Biological factors exert minor influence on the variability of the concentration field.

A review of this system suggests that the eastern sound is more properly viewed as a coastal embayment than as an estuary. Mixing in this area establishes the eastern boundary conditions for the remainder of the sound.