Quartermaster Harbor

Site Description

Quartermaster Harbor is a small harbor between Vashon Island and Maury Island at the southern end of the Main Basin of the Puget Sound. It has depths down to 50 feet. The body of water is fed by Judd, Fisher and Mileta creeks. The islands surround the harbor on three sides, the west, north, and east, with the harbor itself extending longitudinally north to south. Tidal currents in the area, particularly outgoing tides from the Tacoma Narrows, create a relatively continuous clockwise current that encircles Vashon Island, including the mouth of Quartermaster Harbor. Quartermaster Harbor’s marine habitat is affected by an artificial isthmus that was built in 1916 by the Army Core of Engineers. The harbor has been a subject of interest to the WA State Dept of Ecology due to low dissolved oxygen levels observed in the late summer (QMH Nitrogen Management Study 2013). An extensive model of the harbor was developed by the department and its partners to better understand the way nutrients move within the harbor.

Sampling Stations

Figure 1. Station Map of sites sampled in Quartermaster Harbor on 5 May 2023.

Eight stations throughout the harbor were selected for water sampling and CTD profile analysis and are depicted in Fig 1. Sediment samples were collected for analysis at Stations 54 and 56. From Table 1 stations 50 - 53 were sampled in the morning, and stations 54 - 56 were in the afternoon.

Meteorological Conditions During Sampling Period

Barometric pressure from 5/04/2023-5/05/2023 retrieved from NOAA in Tacoma.

May 4th

Weather conditions on the day preceding sampling.

May 5th

Weather was overcast with heavy rains and varing winds during the morning while Team A was sampling. During team B's sampling period in the afternoon there were intermittant rains.

Meteorological Station Information is from SeaTac Airport

SeaTac, WA Weather History | Weather Underground (wunderground.com)

Tidal Patterns During Sampling Period

Figure: Tidal information in Commencement bay May 5, 2023 (closest NOAA station to Quartermaster Harbor).

Tidal Graphs from NOAA for 5 May 2023

CTD Water Property Sections

Surface temperatures ranged from 10 – 14 C, dropping quickly to about 8 C at the thermocline. Salinity was around 25 – 28 PSU, with the deepest parts profiled reaching about 30 PSU. Density hovered around 18 – 20 kg/m3, dropping to above 23 kg/m3 at the pycnocline. Dissolved oxygen peaked at all stations around 5m in depth before declining. Fluorescence was most prominent at station 50, with a peak of 16.4 mg/m3. Transmissivity readings were widespread at depths less than 20m. CTD data was used to create contour sections of QMH seen below.

Comparison of CTD Data with Discrete Water Sample Data

Figure 10: The correlation shown between the Fluorescence concentrations as measured by the Seabird 19 CTD vs the Discrete Chlorophyll. (Credit - Mateo Schuler)

The Fluorescence as calculated by the Seabird CTD at surface and bottom is shown to have no correlation to the discrete Chlorophyll measured in the lab.

Figure 9: Dissolved oxygen (mg/L) measured by the Seabird 19 CTD vs the Discrete dissolved. (Credit - Mateo Schuler)

Dissolved oxygen as measured by the Seabird CTD at surface and bottom is shown to have somewhat of a correlation with discrete dissolved oxygen as calculated in the lab for the majority of stations. The R2 value = .6054. Figure 10. The lab results appear to be consistently higher in values across stations.

Secchi Disk

The average Secchi depth observed across all stations was 2.5m. The deepest observation was made at Station 51 at 3.5m, and the shallowest at Station 55 at 2m. Photosynthetic light layer for most stations reached a depth of approximately 7.5m.

Phytoplankton

Figure: Phytoplankton concentrations from net samples.

Chaetoceros decipiens was observed to be the most abundant phytoplankton species, being present at all stations and blooming at Stations 50, 52, and 56. Image from Encylopedia of Life.

Figure: Phytoplankton concentrations from water samples.

Nutrient Data

Figure: Shows the amount of dissolved inorganic nitrogen (uM) at both surface and deep depths.

54.5 indicates Dockton Station

Dissolved inorganic nitrogen as seen in the deeper water samples, lowered significantly from stations 50 to 56. As the station number increases stations are further inside Quartermaster Harbor. Nitrogen concentration decreased, likely due to being used up by phytoplankton.

Figure: Shows Si(OH)4 concentration at both surface and deep depths

54.5 indicates Dockton Station

Si(OH)4 concentration also decreased as stations are further in the harbor indicating use by phytoplankton.

Nutrient table for Quartermaster Harbor

Sediment Data

Figure: Percent composition of sediment samples procured via Van Veen device.

A high percentage of silt and total organic carbon was observed when compared to other sampling areas. Several small streams feed into the harbor, with Judd Creek being the harbors largest source of freshwater inflow. QMH has slower water currents than other sample sites, likely resulting in the buildup of fine sediment such as silt and clay.

Discussion of Observations

Dissolved oxygen, fluorescence, and transmissivity CTD profiles all indicated a fairly high level of variance in the first 10 – 20 meters. Weather conditions on 5 May could account for this, as heavy rainfall dilutes the top layer of saltwater, and occasional strong winds contribute to surface layer mixing. Phytoplankton counts indicated more overall abundance observed at stations sampled in the morning vs those sampled in the afternoon. The outgoing tide in the morning may have contributed to this abundance by concentrating the water in the harbor, while the incoming tide after the 11:33am low may have flushed in new water, moving and diluting the phytoplankton concentrations. Fig 7 fluorescence CTD profile for station 50 agrees with the abundance reported in Table 2, as does the Fig 11 surface phytoplankton count.

Being a relatively small, shallow and channelized terrain feature, Quartermaster Harbor is likely easily influenced by tidal changes and adverse weather conditions. The differences observed between the different tidal swings on 5 May are likely common on a daily basis as the tide ebbs and flows. Because the harbor is mostly protected by landmasses to the west, north, and east, is possible that the surface layer within the harbor does not get much mixing due to wind unless a strong wind from the south or the north blows directly across the harbor. Being a fairly shallow harbor, phytoplankton concentrations are no doubt higher during the spring and summer as light is able to penetrate deeper and currents are not particularly strong due to the protected nature of the harbor.

It would be of interest to sample phytoplankton regularly throughout the first few weeks of spring and summer sunlight to observe how quickly the phytoplankton reach blooming abundance levels within the harbor. Bill et al. 2016 looked at environmental effects on Alexandrium within the Puget Sound, including QMH. Combined effects of blooming phytoplankton and DO levels below 7 mg/L in the late summer may have a distinct effect on conditions for organisms within the harbor.

Data Repository

Phytoplankton Nets & Surface

Sediments

Page Developed By Michael Paszek and Mateo Schuler

Hydrodynamic Model Report Quartermaster Harbor Nitrogen Management Study. 2013. [accessed 2023 May 18]. https://apps.ecology.wa.gov/publications/documents/1303026.pdf.

Bill BD, Moore SA, Hay LR, Anderson DM, Trainer VL. 2016. Effects of temperature and salinity on the growth of Alexandrium (Dinophyceae) isolates from the Salish Sea. Journal of Phycology. 52(2):230–238. doi:https://doi.org/10.1111/jpy.12386. [accessed 2023 Apr 28]. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4818979/.

County K, DeGasperi CL, Ferguson E. 2012. Quartermaster Harbor Nearshore Freshwater Inflows Assessment.

Stark K. 2007. Quartermaster Harbor Marine Water Quality Data Report 2007 - 2011.

Tobin ED, Horner RA. 2011. Germination characteristics of Alexandrium catenella cysts from surface sediments in Quartermaster Harbor, Puget Sound, Washington, USA. Harmful Algae. 10(2):216–223. doi:10.1016/j.hal.2010.10.002.

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