All natural features that make up river systems are created through erosion. The energy in the water column that causes this erosion is called turbulence. Turbulence isn’t limited to river systems, but the focus of this paper is on turbulence, specifically within the possession sound. Depending on how water is flowing within a local ecosystem, the terrain and biological components in that ecosystem can change drastically. In this study I examine how turbulent flow in the mouth of the Snohomish River in Everett, Washington changes relative to river discharge. I defined turbulence for this study as the relationship of the direction and magnitude of two vertically adjacent water particles. I also used a variation of the Reynolds number (Re) to more clearly define the difference between Transitional and Turbulent flow. In this study, data were collected with a 3-beam Aquadopp 1MHz Acoustic Doppler Current Profiler (ADCP), which measures the speed of passing particles in the water column at 1-meter increments starting at 1.4-meters above the river bed. I processed the data in RStudio and Excel. From preliminary research I know that during periods of high flow, the difference of adjacent flows is more dramatic at depth than it is anywhere else in the water column. I also have observed constant random direction of water flow towards the surface. It is expected that this will also be observed while doing tests with the Re, meaning that there will be continuous high Re at the surface due to outside influences, with low Re at depth during periods of normal flow rate. It is also expected that there will be prolonged high Re throughout the water column during and after periods of high flow rates.

Dissolved oxygen (DO) is a vital component of marine ecosystems, providing the key life source for thousands of species of marine vertebrates and invertebrates. Oxygen’s solubility in seawater is influenced by many variables, which can make DO difficult to predict. Estuarine systems experience DO fluctuations, as DO can limit ecosystem reproduction and health. Levels below 4 mg/L induce hypoxic conditions, creating stress for marine organisms, which makes tracking DO levels over time an essential tool for monitoring marine ecosystem health. My research provides Spatial-temporal depth analysis of DO data from the years 2014 through 2021 in the Snohomish River Estuary in Everett, Washington. Temporally, I predicted DO to exhibit a seasonal trend with highs in the winter and lows in the summer and decrease yearly at all depths due to global ocean temperature increase. Spatially, I expected DO to be higher at sites closer to the Snohomish River, and slightly lower at locations further from the river, in the center of the sound. With regard to depths, I predicted DO to be higher near the surface and lower near the bottom, and the oxycline is expected to get closer to the surface over time. Data were collected using an EXO2 Sonde at five different field sites at varying distances from the Snohomish River. I analyzed data using Excel, RStudio, and ArcGIS. Results found that DO is increasing over most sites with seasonal fluctuations of higher DO in the winter, and lower in the summer. There was one hypoxic event in 2016 at Buoy, along with a yearly increase in DO that suggests hypoxic conditions in Possession Sound may not last. Spatially, DO is higher at sites closer to the mainland, contrary to my hypothesis. Continuation of research will include further analysis of Spatial-temporal data in ArcGIS and Rstudio.

Possession Sound is a dynamic salt wedge estuary system near Everett, Washington that is fed by the Snohomish River. In salt wedge estuaries, a mix of salt and fresh water creates a salinity gradient between the two sources, with the denser, saltier water making up the lower sections of the vertical gradient, and the freshwater residing above it. Turbulence from river flow and tidal currents decreases the concentration of suspended sediment in the water column, measured as turbidity. As stratification increases, turbulence increases too, which then causes lower turbidity. This study explores influences on turbidity at the Everett Marina during the year 2020. In the Everett Marina, North flow corresponds with flood tides, and South flow during ebb tides. During these tidal exchanges, the prediction is that when the tide is slack, the horizontal velocities of the water would show an east/west flow. This east/west flow would create vertical mixing because of upwelling and higher turbidity in the water. Two-dimensional horizontal river flow velocities from 0.9 to 4.9 meters from the riverbed at half-meter and meter increments were measured using a grant-supported deployment of an Aquadopp ADCP (Acoustic Doppler Current Profiler). Turbidity was collected using a CTD deployed 1.7 meters from the surface. The volume, velocity, and sediment deposition of river water were compiled from the United States Geological Survey (USGS), and tide heights were published by the National Oceanic and Atmospheric Administration (NOAA). Preliminary results indicate an inverse relationship between tidal height and turbidity and with an emphasis on further Spatio-temporal relationships, more conclusions may be found. The Everett Marina hosts dredging of the estuary in order to maintain safe river flow to the Possession sound itself. Without this river flow, needed nutrients may not reach the saltwater, disrupting the ecosystem, and increasing flooding.