Commencement Bay is located between Tacoma and Browns Point. During our second sampling of Commencement Bay, we expanded our stations to include 4 more stations further northeast of our initial 4 stations. The locations of our stations can be seen in Figure 1, the station map. 

The salt water in this area comes from the Strait of Juan de Fuca and travels south, down through East passage, to the east of Vashon Island, while fresh water is fed directly from Puyallup River. This fresh water is glacier melt from Mount Rainier and carries sediment into the bay. The Puyallup River contributes the third largest annual river sediment load to Puget Sound (Takesue et al. 2017). We can expect to see larger sediment near the mouth of the Puyallup River as smaller sediment takes longer to settle and will wash further out into the bay.

The Puyallup River delta used to be an estuarine wetland, rich in nutrients and supporting a biodiverse ecosystem, until it was turned into a bustling shipyard to support the growing industries of Tacoma in late 1800s and early 1900s. These industrial activities contributed to the contamination of the bay sediment. "Beginning in 1991, the Commencement Bay trustees, under NOAA’s leadership, have negotiated 19 settlements with polluters—recovering funds, services, and properties to support restoration projects" (NOAA [date unknown]). 

Mixing of the water column in this area occurs during ebb tide as water from south Puget Sound rushes north through the Tacoma Narrows and Colvos Passage. During flood tide, dense, saline rich ocean water travels south through East Passage into Commencement Bay at the bottom increasing stratification with the Puyallup River bringing in fresh water at the surface.

Figure 3: Barometric pressure for 16-17 of April 2026 (Sourced from NOAA).

Longitudinal surfer graph credit: Kendall Burch and Ronnie Sullivan, minor edits by Cristian Carreno

Samples were taken at Commencement Bay on April 17th, 2026. Besides differences with the freshwater surface layer, minimal to no stratification was observed within the deep water column of Commencement Bay aside from the upper layer with the present freshwater input by the Puyallup river that feeds into Commencement Bay. 

Starting with the outer bay (stations 1, 2, and 3), the graph resulting from the CTD data shows that the outer bay has a layer of freshwater at the surface, with a slightly deeper layer of that fresh water to the right of the bay as the water keeps to the right while flowing out of the bay. There was similarly a higher level of fluorescence, dissolved oxygen, and lower transmissivity to the right of the bay at stations 2 and 3, showing the outflowing freshwater positively impacting the productivity of phytoplankton in Commencement Bay. Aside from this freshwater layer on top, the water column below is well mixed, with the temperature remaining relatively consistent, salinity having a slight decrease of 1 PSU down the water column, and density following a similar trend of a decrease of 1 sigma-t. There was also a decreased level of nitrate in the surface when compared to the bottom layers of stations 2 and 3, correlated with the bloom of algae in those stations. Station 1 saw a higher level of nitrate in the surface layer than the deep waters which was to be expected with the lower level of phytoplankton activity.

A longitudinal transect was taken between the outer and inner bay with stations 2, 4, and 6. With the contour graphs constructed from the CTD data, there was a clear mixing of water that occurred with the transition of the inner bay to the outer bay. The decrease of salinity and density of the inner bay was seen to occur at lower depths when compared when to the outer bay. A layer of stratification at the surface of station 6 was more pronounced than that at station 2, which had a much thinner layer of freshwater moving over top of it. This was from the incoming freshwater that flowed into Commencement Bay from the Puyallup river, first flowing through station 6 before it reached station 2. There were higher levels of dissolved oxygen that could be seen toward station 2, likely related to the less turbid waters that allowed for phytoplankton to propagate in the outer bay compared to the inner bay. 

Stations 5-8 were sampled near the Puyallup River delta. The graphs produced for these sites show similar stratification throughout the water column, which was especially clear in their thermoclines, pycnoclines, and transmissivity seen in this section's graphs.  The phytoplankton counts found at these stations, along with dissolved oxygen and low transmissivity at the surface of this section, shows that phytoplankton were beginning to thrive. With this high activity, the phytoplankton will begin to consume the oxygen and nutrients in this area. If sampled at a later date, it is possible that lower DO and phytoplankton counts will be found along with higher transmissivity as the phytoplankton will have reproduced, consumed the vital resources that made it possible for them to thrive, and the population will have thinned out.

Phytoplankton analysis: Despite having the highest visibility with a Secchi disk, low fluorescence, and remaining high in NO3 concentration, station 1 saw a bloom of several species just as other stations had observed. This difference in fluorescence, visibility, and nutrient concentration in the water may potentially be inferred to be due to Chaetoceros socialis, as it was the only species of phytoplankton that was observed at every other site, but was not present at station 1. Though, due to the early learning period of identifying phytoplankton during the time this count took place in, it is not entirely certain that Chaetoceros socialis were not miscounted as the general species.

Nutrient analysis: Si(OH)₄ had a relatively even distribution across the deep water samples but had higher amounts with inner stations near the mouth of the Puyallup river, with a higher concentration to the inner stations north of the mouth. This suggests an influx of Si(OH)₄ from the outflow of the Puyallup river. NO₃ was seen to be lower at the surface in all stations aside from at station 1 where the NO₃ concentration was slightly higher than in the deep. This shows a use of NO₃ by the phytoplankton blooms in these areas, decreasing the concentration as the NO₃ was taken up at the surface.

Sediment analysis: Both sediment samples from the inner bay, station 8, and the outer bay, station 1, had high levels of sand as well as silt, with silt being in higher concentration in station 8 which may be attributed to its proximity to the outflow of the Puyallup river containing sediments from glacial melt. The low fluorescence at the surface of inner bay stations combined with the lowered transmissivity shows the sediment load that the incoming water was bringing into the waters of Commencement Bay. There was a higher organic carbon at station 1 compared to station 8, which may be attributed to a faster rate of sedimentation. The inner stations such as station 8 had more sediment being brought in and kicked up into the water, leading to less organic compounds to be deposited when compared to outer stations that were less affected by the freshwater input, such as station 1.

Master Log

CTD files

Dissolved Oxygen

Chlorophyll

Nutrients

Phytoplankton Nets

Phytoplankton Surface

Sediments

Page developed by Cristian Carreno and James Simpson