Ocean acidification, the persistent lowering of pH in marine environments, is influenced by water chemistry, biological aspects, seasonal changes, and human activity. Low pH (acidic conditions) can contribute to hypoxia, coral bleaching, and other dangerous conditions for the environment. Estuarine environments contain all these influences. In this study, changes in pH in Possession Sound, WA were examined over a five-year period, with the context of changes in river discharge. This was accomplished using a YSI EXO Sonde periodically deployed nearshore in Mukilteo, Washington, USA used in partnership with Ocean Research College Academy. This site, being within the Snohomish River Estuary, is affected by both oceanic factors and the Snohomish River, including any runoff that comes through those waters. These measurements create a depiction of changes in pH mostly due to seasonal factors, like river discharge and upwelling. Early results from these data demonstrate a clear seasonal pattern without significant annual trends toward lower pH. As climate change progresses, consistent monitoring of ocean pH will be essential to understanding the effects of ocean acidification and the ways we might combat them in the future. While this study was limited by its short timeframe, these results provide an important baseline for continued collection and analysis of these data.

Nutrient levels in marine environments can vary widely due to local geography, the placement of various manmade input sources, seasonal factors, and tidal patterns. They are important in understanding the overall health of an ecosystem, as they can be an indicator of potential pollution. They also have a significant impact on plankton populations and, as a result, primary production. Unnaturally high nutrient levels can affect other water chemistry variables, contributing to events such as harmful algal blooms, hypoxia, and ocean acidification. In this study, I analyze 13 years of nutrient data from ten Possession Sound sampling sites, at varying distances from the mouth of the Snohomish River. Nitrate and phosphate levels were analyzed temporally, and tidal, weather, and river discharge data was overlaid to analyze the relationship between nutrients and other facets of the surrounding environment. My early analysis indicates that seasons play a large role in nutrient levels, likely due to the weather of the Pacific Northwest and runoff from the Snohomish River. Figures also support the relative similarity of values between sites, showing that nutrient levels in the Snohomish River estuary are collectively affected by nutrient flow rather than having site specific characteristics. Studies of this type can provide insight about specific characteristics of our local nutrient pathways and can provide context for changes in our ecosystem. For further research, oceanic parameters such as dissolved oxygen, pH levels, and plankton densities should be analyzed in comparison to nutrients in order to gain a better understanding of the actual relative impact of nutrients in this local marine system.

In any marine ecosystem, water currents are an important factor in both the biological aspects and the physical movements of a body of water. The focus of this study, the Possession Sound estuary in the Salish Sea, lies in an interesting area that is affected both by discharge from the Snohomish River and surrounding streams, and incoming ocean currents from the Pacific Ocean. In Possession Sound the currents can affect everything from the regular boat traffic through the area to the transportation of debris and other natural or harmful substances in the water. I used an Acoustic Doppler Current Profiler (ADCP), moored in the Everett marina at the mouth of the Snohomish River, to collect data on current velocity for 10–30-minute intervals over the period of seven months in 2020, and almost two months in 2021. The collated data I then used to analyze the current directions and speeds of the water to determine potential local trends in the currents. Preliminary analysis shows that the currents flowing near the moored ADCP tend to flow north and south with fewer currents going to the east or west. However, the currents going east and west are often faster than the north and south streams. These two trends are likely caused by the north moving ocean currents and the south moving river currents, but more research utilizing related data such as river discharge is necessary. Because of the estuary’s diverse current sources, the analysis of these data allows for a greater understanding of the movements of the water column, and insight into the transportation of important substances within it such as nutrients and heavy metals.

Possession Sound, a fjord-type estuary system in the Salish Sea, is home not only to incredible biodiversity but also to some unique clines. A cline, such as a thermocline or a halocline, is a portion of the water column where a physical property changes significantly with depth. The haloclines of the Possession Sound fjord system vary periodically in stratification, particularly at river mouths. One such area can be found at the mouth of the Snohomish River, where cold freshwater flows into warmer seawater, creating a stratified but unstable water column. This study aims to draw connections and seek out patterns between current speeds and temperatures. Temperature data was collected from the Ocean Research College Academy's Conductivity, Temperature and Depth (CTD) sensor mooring at the Everett Marina, and current speed data was collected from their Acoustic Doppler Current Profiler (ADCP) in the same location. Prior research suggests that during most parts of the tidal cycle, temperature readings at the surface correlate strongly with tidal stages: the surface becomes colder when river water flows out to sea at low tide and warmer as the seawater pushes the river water back at high tide. However, when the tide cycle becomes less intense and current speeds decrease, this correlation becomes muddied. It is hypothesized that this pattern represents a decrease in thermocline stratification during periods of slower current speeds. Prior research done on this correlation at the mouth of the Snohomish River lacked in scope and statistical support. By expanding the scope by several months and incorporating statistical support, this study has reinforced previous findings, supporting the hypothesis posed previously: a linear correlation between the variables was supported with a p-value of 2.89E-25, and the inverse linear correlation between temperature and tide height was stronger during periods of greater average current speed.