Possession Sound, WA, serves as an important foraging area for a group of seasonally resident gray whales Eschrichtius Robustus. This group of predominantly Eastern North Pacific Gray Whales that visit Possession Sound (Sounders) arrive as early as January and continue migrating towards other feeding grounds near May. If the frequency of sounds within the hearing range of these gray whales (50 to 5000 Hz) exceeds comfortable levels, they may have difficulty foraging. To monitor these relationships, we looked at the frequency and amplitude of sound near Mt. Baker Terminal (MBT) in Possession Sound, WA, from January 2021 to May 2021 with a specific focus on sounds from 50 to 5000 Hz. To gather this data, we used a SoundTrap 300 HF hydrophone, which is currently mounted to a dock at MBT. From January 2021 to February 2021, the hydrophone recorded continuously at a 96-kilohertz sampling rate. From March 2021 to May 2021, the hydrophone was set to record the first fifteen minutes of every hour at the same sampling rate. Preliminary research shows that Possession Sound has a consistent prevalence of ambient and intermittent noise within the established frequency range and peak amplitudes as high as 164 dB. This level of noise may have the potential to negatively affect gray whale behavior and foraging success. Future research should be conducted to see how current and future vessel slow-down trials will impact the frequencies and amplitude of local noise. Future research should also include comparing the MBT sound profile to other sites in the Salish Sea to better understand if the amplitude increase is unique to the area or a cause for wider concern.

The interaction between incoming salt water from the ocean, which is driven by tides, and exiting freshwater from rivers drives circulation through estuarine environments. As a result of the interaction between the incoming water and the exiting water, nutrients and sediment are moved around the estuary. This study focuses on the interaction between tides and the Snohomish River as it enters the Possession Sound estuary, located in Everett, Washington. To acquire data, I deployed a boat-mounted acoustic Doppler current profiler (ADCP), which uses sound to measure water current direction and velocity. I collected these data at varying tide stages at three different sites between the Snohomish River’s southern output to nearby Mount Baker Terminal, located 3.6 miles southwest of the river output. I have collected 8 samples over the course of 7 months at both ebb and flood tide stages. Each transect survey lasted 3-6 minutes and collected data from the first 20 meters of the water column. To get accurate analysis of current velocity and direction I split the data into categories based on depth. Preliminary analysis shows a southward current at many sites during all tide stages and depths. This raises questions about the scope of the river influence and the potential for southward currents regardless of tidal stage. However, further analysis of current velocity and river discharge are needed. Due to the complexity of the currents in the area, understanding how the river and the tides are interacting can provide a greater understanding of how these currents are impacting the dispersal of sediment and nutrients throughout the estuary.

The Everett Marina is a heavily developed area that has significantly altered water flow from the Snohomish River compared to its natural state. Anthropogenic alteration of this environment led to buildups of sediment, which has required dredging at increasingly shorter intervals leading up to the present. In order to explain sediment accumulation in the marina, this study examines the movement of currents and the abundance of sediment using an Acoustic Doppler Current Profiler (ADCP); data were recorded from June 2020 to August 2021 and compared to recent data I recorded from February and March of 2023. I hypothesized that current direction would be variable and speed would be sluggish due to the shallow depth. In addition, I hypothesized that seasonal changes such as snowmelt in spring and rain in winter would impact the velocity of the currents. Because sediment movement is largely impacted by currents, I hypothesized that sediment abundance would reflect seasonal changes in water flow. Analysis of water current data between June 2020 and August 2021 demonstrates a significant correlation between the velocity of North/South currents and the magnitude of tide stages, but river discharge levels appear to have less of an effect on current speed in the marina. The susceptibility of this area to tides more than river discharge suggests that it is easier for sediments to accumulate in one area as opposed to being swept away. Future analysis will compare this past data to the present and investigate potential correlations with sediment abundance.

Local bathymetry in estuaries strongly affects water current direction and speed. Water current and speed, or the water flow, determine the circulation of nutrients and oxygen within the estuary. To assess the relationship between water currents and slopes in an estuary, I utilized a boat-based acoustic doppler current profiler (RD Instruments Workhorse 600 kHz ADCP) to measure water speed and direction with depth. Based on preliminary analysis, water direction is consistent at surface level but becomes inconsistent beyond that. Speed is mostly between 0 cm/s and 50 cm/s, but becomes more varied beyond 30 meters. However, that may be due to inaccuracies in measurement, as data collection becomes less consistent beyond that depth based on our current ADCP configuration. The average direction of data at each depth doesn’t change significantly with depth. In summary, speed is mostly consistent with depth near a slope, whereas the direction is not. So, the bathymetry may have a greater effect on water direction than speed. For future work, investigating these patterns with higher resolution datasets will shed more light on any potential patterns.

River otters (Lontara canadensis) are high trophic level opportunistic feeders. Their diet, examined through scat, provides key information about local ecosystems. Previous studies have observed a diet dominated by fish, including studies in California (90%), Utah (96.5%), and North Dakota (83%); however, my preliminary results on otter diet at the mouth of the Snohomish River highlight a greater variation in observed prey. The meeting of the Snohomish River and Possession Sound creates a salt wedge estuary with extensive tide flats, providing access to diverse freshwater and saltwater prey species. From 2012-2015, river otter scat samples were collected, dissected, and identified by students at the Ocean Research College Academy (ORCA). Averages over the three years showed that fish were the dominant prey type in fall, winter, and summer; however, crustaceans dominated the river otter diet in the spring. In this study, I dissected scat samples from fall 2022 through spring 2023 from 2 sample locations in Everett Marina. In the more recent data, fall 2022 has followed the pattern of these historical studies, but the winter samples have indicated a shift of fish and crustaceans. In fall 2022, 5/25 samples showed 50% or fewer fish bones, while winter 2023 showed 11/13 samples with less than 50% fish bones. Given that otters are described as opportunistic feeders, this shift in winter diet, relative to previous years, may suggest a significant environmental shift. Future research must examine physical environmental features such as changes in river discharge and/or water temperature. Identifying specific fish species in samples may also reveal prey availability throughout the seasons.

Unique relationships between photosynthetic active radiation (“PAR”), turbidity, chlorophyll, and dissolved oxygen (DO) can impact primary productivity levels and directly relate to the health of an estuary. Previous studies show that microbial processes depend on PAR and dissolved oxygen. To some extent, this can govern the rate of near-surface mixing, affecting turbidity and the amount of chlorophyll produced. My preliminary results using data from Possession Sound, a salt wedge estuary, show similar patterns. By examining the previous Ocean Research College Academy’s (ORCA) profile data from 2015-2022, I observed that an increase in chlorophyll corresponded with an increase in turbidity. Further, if there is an increase in chlorophyll, there is an increase in dissolved oxygen. From the fall of 2022 to spring of 2023, I collected additional profiles, including PAR data, from three sample locations in Possession Sound. My results show that when PAR is high, chlorophyll levels and turbidity are also high. However, PAR values are inversely proportional to dissolved oxygen concentrations. This means there are correlations among chlorophyll, turbidity, DO, and PAR values with depth. However, PAR can be affected by many factors, so it is difficult to say that any one of these parameters directly relate to PAR values with depth. Future research can examine different parameters affecting PAR with depth, as availability of sunlight and nutrient levels can also affect PAR data.

Phytoplankton production depends on a number of factors including nutrient availability, water chemistry variables, and light penetration. Previous studies have shown light penetration to be important for submerged aquatic vegetation, the primary producers that support the marine food web and the ecosystem. Possession Sound is a productive sub-basin of the Salish Sea with complex influences on local water chemistry and primary productivity. Given the significance of primary production in a salt water estuary, this study looks at the seasonal relationships between water chemistry and light penetration, measured by photosynthetically active radiation (PAR) in the Possession Sound estuary across three sites. I collected Seabird CTD and YSI EXO profile data as well as PAR sensor results, in Possession Sound from July 2022 through March 2023. Accompanied with historical data collected by past Ocean Research College Academy researchers, I analyzed site dependent relationships as well as the seasonal relationships. Preliminary analyses showed PAR decreasing with higher salinity and turbidity, but increasing with temperature. Limited connection was observed with dissolved oxygen. Studying the relationships among light penetration and water chemistry allows us to better understand the complex relationships among the key factors determining seasonal primary production.

In estuaries and marine environments, eelgrass (Zostera spp.) is considered a keystone species as many marine species depend on the beds for food and shelter. Eelgrass beds also trap sediment, stabilize substrate, reduce wave energy and reduce coastal erosion. The degradation of eelgrass beds can instigate a decline in those species that rely on the eelgrass beds. Eelgrass is traditionally mapped using aerial photographs or diving surveys, which can be time-consuming and ineffective. Another strategy is to use boat-mounted Acoustic Doppler Current Profiler (ADCP), to create transects of eelgrass beds through backscatter data. The purpose of this study is to assess the application of an ADCP to map local eelgrass beds in Possession Sound and determine its advantages over single-beam sonar. I used a boat-mounted RD Instruments Workhorse 600kHz ADCP during transects of a Possession Sound eelgrass bed. Raw data was filtered using Excel to isolate backscatter data for analysis and visualization. These results were compared to the results from a single-beam sonar system. It is expected that the height of the eelgrass and extent of the beds will be seen through the visualizations, even in winter and early spring surveys. A multibeam sonar like an ADCP will be more efficient in mapping a greater area of eelgrass beds as well as providing greater clarity in visualizations than a similar single-beam sonar through the ADCP’s emittance of multiple sound impulses at once.