Eelgrass (Zostera marina) is a vitally important organism to the Puget Sound that exists along the shallow, muddy seabed. Many different living creatures of all trophic levels rely on the eelgrass beds to survive and absorbed contaminants could be a real threat. Toxics metals in the eelgrass, sediment and water column could have critical implications to the ecosystem. The heavy metal concentrations in the eelgrass, sediment and the water column of two locations in the Possession Sound (Mukilteo and Buoy) were analyzed in order to determine the specific levels of metals and contaminants that travel up through the trophic pyramid. The study endeavors to determine the metal absorbance ability of eelgrass and check if factors including temperature of the water column, seasonality or time of day influenced heavy metal uptake by eelgrass. A sediment grab was utilized to collect the sediment and eelgrass samples. Sample analyses were conducted at the Everett Environmental Laboratory and in partnership with a University of Washington trace metals laboratory to find the concentration of the metals arsenic, copper, lead, zinc and cadmium in the surrounding water column and the eelgrass. It was predicted that greater concentrations of copper and zinc would be found near Buoy because they are legacy chemicals and due to anthropogenic influences near the Everett Port of Everett. It was also hypothesized that a higher concentration of metals would be found in the eelgrass during the spring and summer as more direct sunlight leads to greater primary productivity and uptake of chemical constituents. Determining these types of correlations and catalysts is significant to the entire Possession Sound ecosystem as it would lead to possible strategies on how to prevent further contamination of eelgrass. Furthering our understanding of the connected network of interactions here can only benefit the future inquiries.

The Puget Sound is a complex estuarine system within the Salish Sea, fed by both high salinity water from the Pacific Ocean and freshwater from a number of rivers. The Snohomish River is the second largest input, transporting freshwater from the Skykomish and Snoqualmie rivers to Port Gardner Bay off the coast of Everett. At its mouth, the higher density salt water from the Puget Sound intrudes into the freshwater, forming a salt wedge that causes a highly stratified water column which rapidly changes with the tidal cycle. These mixing dynamics may be the primary driver of biological productivity in the estuarine system. To characterize the density profile relative to tidal patterns and season, current speed and velocity were recorded utilizing a Nortek ADCP. During normal outflow (3,500 f^3/s) of the Snohomish River, upward velocities were positive during flood tide and negative during ebb tide, following a typical salt-wedge trend. During a peak outflow event (56,000 f^3/s) on October 22nd, this tidal cycle dependence was disrupted and downwelling dominated in the form of negative vertical velocities throughout the water column. In addition, the magnitude of east/west velocities increased during peak outflow. This signaled a period of intense turbulence at the bottom of the water column. During the same time span, data concerning turbidity and chlorophyll levels were recorded utilizing a Seabird CTD. No clear trend was evident in chlorophyll levels at both normal and peak outflow timespans. Turbidity maintained high levels (35 NTU) following peak outflow, possibly reflecting the transportation of sediment from the river bed into the water column. This transportation would be caused by the turbulence reflected in the higher magnitude of the east/west velocity data.

Possession Sound is a salt-wedge estuary influenced by both sea water entering through the Puget Sound and fresh water entering from the Snohomish River. Regionally, upwelling off the Pacific Coast during spring and summer months brings acidic deep water into the Puget Sound. Locally in the Possession Sound, previous research has shown that seasonal cycles in both temperature and river discharge are the primary influencers of pH. These cycles are affected by the El Niño Southern Oscillation (ENSO) climate pattern, which alternates between a cooling phase (La Niña), a warming phase (El Niño), and a neutral period. The biological processes of many organisms are influenced by pH levels, and few studies have examined interannual pH variation in estuaries. This study seeks to identify the influence of ENSO on pH cycles in two different areas of Possession Sound, based on proximity to the Snohomish River. Surface pH and temperature data were analyzed at two sites, Buoy (closer to the river) and MBT (farther from the river) from January 2010 to September of 2017, using Yellow Springs Instruments and a Niskin Bottle. River discharge data was ascertained from United States Geological Survey data recorded near Monroe, Washington (2010-2017). The hypothesis of spatial variability in pH due to proximity to the river was not supported. Many of the trends at Buoy were the same or more pronounced at MBT, suggesting that the influence of the Snohomish River at Buoy did not make that site more sensitive to ENSO than MBT. Surface pH was more variable at MBT than at Buoy during the summer months, presumably due to eutrophication and subsequent decay during periods of intense biological productivity. Future studies are planned for seasonal variations of biological factors along with dissolved oxygen variation with depth to further analyze these pH trends.

The focus of this research is on the abundance of nutrients and which non-toxic heavy metals concentrations in estuarine eelgrass (Zostera marina L.). Eelgrass beds are an important factor in the marine environment, providing a secure habitat for marine life to forge, obtain shelter, spawn, and stabilize the sediment. Also, eelgrass beds reduce costal erosion, meaning healthy eelgrass beds maintain stability in the marine ecosystem. Nutrients and heavy metal concentration is an important element to eelgrass health. Eelgrass plants rely on nutrient abundance to fuel growth, and non-toxic heavy metals in the sediment are absorbed by the plants. Previous research has shown that productive eelgrass beds reduce coastal erosion and cycle carbon dioxide and nutrients into the surrounding ecosystem, acting as a filter for an estuarine habitat. Data collected by the Ocean Research College Academy (ORCA) between 2009 and 2017 were analyzed. It was hypothesized that phosphate and nitrate in the water column would be most abundant during the cold seasons due to high intake of nutrients during the spring and summer, and heavy metal concentration would be more abundant during the spring and summer due to industrial runoff. Results support the original hypothesis, as the data indicate that the highest nutrient abundance occurred December-February each year. Phosphate levels at Site 1 had an abundance of 2.47 [PO₄] μM in December of 2010, which was the highest phosphate level observed. The lowest phosphate abundance throughout the year occurred during the spring of each year. Arsenic, copper, zinc and lead were found to be the most common non-toxic metals concentrated in the eelgrass, which also appeared to have some seasonal influence, likely do to industrial runoff during the spring .