Ian Reeber
TESC 445
Field Report #5
Introduction
Quartermaster Harbor lies between Vashon Island and Maury Island. An isthmus connects the
two islands today. Historically during high tide water would flow through a shallow entrance at what is
now known as Portage. The lack of flow through this point today reduces the amount of flushing for the
harbor. The inner harbor has an average depth of about 5m and has two small creeks discharging
freshwater (DNR 2004). A continuous assessment of the physical characteristics, marine communities
and sediments aid in the understanding of how nutrients and potential pollutants cycle within and, or
flush in and out of the harbor. In April 2012 the estuarine field course monitored 8 stations for this
purpose.
Methods
Eight stations in Quartermaster Harbor were the focus of study. The goal was to sample each
station for depth, % transmission, DO, chlorophyll a, nutrients, salinity, density, temperature, grain size,
total organic carbon (TOC), micro plastics and turbidity.
CTD
A CTD Was dropped at each station carrying instruments sampling % transmission, density,
conductivity/salinity, fluorescence, temperature and DO. The CTD was lowered at about 1m/sec to
about 1m above the bottom at each station, and took 2 samples per second. The % transmission data
represented the suspended particulate in the water, and the fluorescence data was a method for
attaining the amount of chlorophyll a in the water. Before dropping the CTD, it was lowered just under
the surface of the water and run for three minutes to insure that water in the pump and membranes
was cleaned out.
Niskin/Thoreson Bottles
A Niskin bottle was secured above the CTD and tripped when the CTD was stopped about 1m
above the bottom at each station. This provided a water sample from roughly 2m above the bottom. A
Thoreson bottle was lowered just under the surface of the water, and 3m below the surface for surface
and thermocline water samples. Water from both bottles was collected for surface, thermocline and
bottom DO, chlorophyll, and nutrients. For each level two glass stopper flasks, approximately 145ml in
volume, were filled for testing DO, two sample bottles, approximately 145ml, were filled for testing
chlorophyll a, and one bottle was filled for testing nutrients. Each bottle was thoroughly rinsed three
times with the sea water attained for specific samples three times before filling. The nutrient and
chlorophyll a bottles were placed in ice after filled.
DO
DO was sampled throughout the water column on the CTD with a DO meter at a rate of
approximately 2 samples per second as it was lowered. DO was also measured from the samples
collected from the Niskin and Thoreson bottles with the Winkler titration method. Immediately after
the glass stopper flasks were filled, 1ml of the manganous reagent and 1ml of alkaline-iodide reagent
was added to fix the oxygen in the samples. These samples were titrated with a dosimat using
standardized thiosulfate solution, and starch solution added to the DO samples.
Chlorophyll a
The fluorometer on board the CTD provided data for chlorophyll a in the entire water column
down to about 1m above the bottom. The sample bottles obtained from the Niskin and Thoreson
bottles were run through a fluorometer in multi-optional raw fluorescence mode. This yielded values
for chlorophyll a μg/L, phaeopigment μg/L, and F0/Fa ratio from the surface, thermocline and bottom of
each station.
Phytoplankton
At each station a 500 micron net was pulled through the water approximately 10m. The
remaining concentrated sample in the net’s cod end was poured into a 145ml jar. The contents of the
jars were analyzed later to identify the genera of phytoplankton present at the surface of each site and
rank them by abundance. Phytoplankton samples were also drawn from the Niskin and Thoreson
bottles were fixed with formalin and allowed to settle overnight. After the phytoplankton had settled,
the contents of the samples were decanted down to approximately 10ml, leaving the fixed
phytoplankton in the remaining seawater/formalin mixture. The contents of the remaining 10ml were
then thoroughly mixed. 1ml of the mixed contents was drawn with a volumetric pipette and introduced
to a Sedgwick slide. The common species of phytoplankton were counted and identified with a
microscope, in which a minimum of 100 were counted within one transect line. Continuous transects
were counted if 100 had not been identified within the first. The data was then used to calculate
phytoplankton per volume.
Grain Size and TOC
At stations 1 and 5 a ponar (Van Veen) grab was used to obtain sediment samples. Stations with
similar coordinates to stations 6, 7, and 8 were sampled one week prior. For this reason they were not
sampled again. Stations 2, 3, and 4 were also not sampled for this parameter. The sediment obtained
from each station was collected in zip-lock baggies for both grain size analysis and TOC analysis. The
grain size was measured with a Beckman-Coulter Counter grain size analyzer. For each station the
sediment was run three times. For each run the sediment particle diameter was categorized by ranges
of size measured in microns. The Beckman-Coulter Counter also provided basic statistical analysis of the
array of sediment diameters.
For TOC analyses 10ml of sediment was placed into a blast furnace in a clean dry crucible. Once
dry and cooled the weight of the sediment was measured. The sediment was then placed back into the
furnace at 650 C for 8 hours to burn off all organic material. Once cooled, the sediment was weighed
again. The weight of carbon in the sample was the difference of mass from the first dry weight and
second dry weight.
Micro plastics
A 250 micron manta net with an attached flow meter was dragged off of the side of the boat, to
minimize turned up water from the prop, for 15 minutes at a rate of 2-4 knots. After the net was
brought in the contents were thoroughly rinsed down into the cod end. The contents of the cod end
were then thoroughly rinsed through a 5mm sieve, followed by a 0.25mm sieve. These remaining
contents were rinsed thoroughly into sample bottles.
After identification, all contents sifted from the 5mm sieve was discarded. The mass of the
small sieve portion was determined after drying it in an oven for 24 hours. After this all organic matter
is removed through a wet peroxide oxidation process. Afterwards, the remaining contents are dried in
an oven for 24 hours and the remaining mass of the contents was determined.
Nutrients
The nutrients samples collected from the Niskin and Thoreson bottles were frozen and sent off
to a lab for analysis of nitrates.
Results
Fig. 1: The temperature of each station from surface to 45m. The bottom temperatures for stations 50
and 51, not depicted here, were 7.34°C and 8.29°C.
7
Temperature °C
9
10
8
11
12
13
0
5
Depth (m)
10
15
20
25
30
35
40
45
STN50
STN54
STN51
STN55
STN52
STN56
STN53
Dockton
Fig. 2: The salinity of each station from surface to 45m. The bottom salinity for stations 50 and 51 was
29.4 PSU, 28.9 PSU.
22.5
23.5
24.5
Salinity (PSU)
25.5
26.5
27.5
28.5
29.5
0
5
Depth (m)
10
15
20
25
30
35
40
45
STN50
STN54
STN51
STN55
STN52
STN56
STN53
Dockton
Fig. 3: sigma-t of each station from surface to 45m.
sigma-t
17
18
19
20
21
22
23
0
5
Depth (m)
10
15
20
25
30
35
40
45
STN50
STN54
STN51
STN55
STN52
STN56
STN53
Dockton
Fig. 4: Fluorescence of each station from surface to 70m.
0
2
Fluorescence (mg/m3)
4
6
8
10
0
10
Depth (m)
20
30
40
50
60
70
STN50
STN51
STN52
STN53
STN54
STN55
STN56
Dockton
Fig. 5: The % transmission of each station from surface to 45m, representing the clarity/turbidity of the
water.
50
60
% Transmission
70
80
90
0
5
Depth (m)
10
15
20
25
30
35
40
45
STN50
STN54
STN51
STN55
STN52
STN56
STN53
Dockton
Fig. 6: Chlorophyll a vs. fluorescence at each station. The chlorophyll a vallues are averages from two
sample per location depth.
Chlorophyll vs. fluorescence
10
2.00
1.50
1
1.00
0.50
0.00
fluorescence (mg/m3)
Chlorophyll F0/Fa ratio
2.50
0.1
STN 50 STN 51 STN 52 STN 53 STN 54 STN 55 STN 56 Dockton
chloro surface
chloro thermo
chloro bottom
fluoro. surface
fluoro. thermo.
fluoro. bottom
Fig. 7: The DO for each station from surface to 25m.
DO (mg/l)
7
8
9
10
11
12
13
0
Depth (m)
5
10
15
20
25
STN50
STN54
STN51
STN55
STN52
STN56
STN53
Dockton
Fig. 8: The DO for each station via Winkler titration at the surface, and thermocline. Each value is an
average from two samples.
DO (Winkler Titration)
15.3
15.0
14.0
12.1
11.9
12.0
11.9
DO (mg/l)
13.0
12.0
11.0
11.1
10.8
10.0
9.0
10.8
10.3
10.9 11.0
9.4
10.7 11.0
9.9
9.5
12.7
12.3
11.7
12.0
11.7
9.4
8.2
8.0
7.0
STN 50
STN 51 STN 52 STN 53 STN 54 STN 55
DO surf
DO therm
DO bottom
STN 56
Dockton
Fig. 9: The DO for each station via CTD at the surface, thermocline and bottom.
DO (CTD)
13.0
12.0
DO (mg/l)
11.0
11.9
11.7
11.7
11.1
11.3
10.0
10.8
10.9
12.8
12.1
11.7
11.8
10.7
9.6
10.4
10.2
9.9
9.7
12.4
12.5
12.3
9.4
8.9
9.0
8.3
8.0
7.5
7.0
STN 50
STN 51
STN 52
DO surf
STN 53
STN 54
DO therm
STN 55
STN 56
Dockton
DO bottom
Fig. 10: Chlorophyll vs. phytoplankton abundance at each station. Phytoplankton data for station 56 was
not cataloged.
2.50
10000
2.00
1000
1.50
100
1.00
0.50
10
0.00
1
surface
thermocline
phytoplankton surf.
phytoplankton therm.
bottom
Phytoplankton abundance/ml
Chlorophyll F0/Fa ratio
Chlorophyll vs. Phytoplankton Abundance
Fig. 11: Phytoplankton concentrations at surface and thermocline of each station by percent.
Fig. 12: Grain/paricle size analysis of sediment obtained via ponar grab. Grain size analysis was not run
for the Dockton station due to high concentrations of shells.
Grain Size
Grain size composition (%)
100%
90%
very course sand
80%
course sand
70%
medium sand
fine sand
60%
very fine sand
50%
silt
31
40%
15
30%
8
4
20%
10%
clay
0%
55
53
52
Fig. 13: TOC from sediment obtained from four stations.
TOC
Percent Organic Composition
12
10
8
52
6
53
55
4
Dockton
2
0
Stations
Table 1: Washington State Department of Ecology dissolved oxygen classes.
Washington State Dissolved Oxygen
Standards
Class AA - Extraordinary
> 9.5 mg/l
Class A - Excellent
> 8 mg/l
Class B - Good
> 6.5 mg/l
Class C - Fair
> 4 mg/l
Table 2: The relative abundance of varying genera of phytoplankton at each station. Samples were
collected via net.
Station
Actinopytycus
Chaetoceros
Cosinodiscus
Cylindrotheca
Dactyliosolen
Detonula
Dinophysis
Ditylum
Eucampia
Gymnodinium
Navicula
Odontella
Pluerosigma
Protoperidinium
Psuedonitzschia
Rhizosolenia
Skeletonema
Stephanopyxis
Thalasionema
Thalasiosira
Tropidoneis
Key:
Bloom
Dockton
Abundant
50
51
Common Rare
52
53
54
55
56
Discussion
Temperature
In all stations the thermocline was around 3m (Fig. 1). The thermocline became more defined
with each consecutive station moving inward into QMH. Stations 50 and 51 were both fairly deep and
exposed to the main channel of this portion of Puget Sound. This is likely the cause of the faint change
in temperature to depth. There may be extensive vertical mixing in these areas as well due to the tidal
currents that disturb the waters around the edges of the islands. Further into QMH the stations become
shallower and also flush less frequently. This allows the surface waters to warm considerably, and is the
cause of the sharp thermoclines seen in the rest of the data. In stations 50, 52, 53, 54, and 56 the water
warms slightly just above the thermocline. This suggests that the surface waters warmed for a while
undisturbed then began to overturn with the consistent winds during the day of sampling.
Salinity and density
For each station the halocline was around 3m (Fig. 2). The consecutive drop in salinity, with
moving further into the harbor, along the surface mirrors that of the temperature. The outer stations 50
and 51 are the highest at the surface, most probably due to the same influences explained above. The
salinity and temperature are not directly linked to one another though. The common factor that links
the two is the decreasing rate of flushing throughout the harbor towards its head. This affects the
surface salinity by allowing the recent rainfall to remain on the surface, in turn decreasing salinity. This
is also suggested by the surface water density (Fig. 3). The harbor is also fairly well protected from
winds, which reduces the amount of turnover influence from wave action.
Fluorescence, % transmission, and chlorophyll a
The fluorescence of each station seemed to peak from around the thermocline down to about
10 m in depth (Fig. 4). The % transmission also seemed to peek in this range for most stations (Fig. 5).
This suggests that phytoplankton concentrations are highest in this range. Although there is a clear peak
in the clarity and fluorescence in this range throughout all stations, overall the % transmission and
fluorescence increase and decrease erratically with depth. This suggests that there is either a fair
amount of vertical mixing occurring, or pockets of water with higher concentrations of nutrients, or
both. This may also be the cause of the inconsistency in chlorophyll a vs. fluorescence (Fig. 6). These
are both indicators of phytoplankton production, but the data from both do not agree with one another.
The data from each were obtained from two separate vessels which were not dropped in exactly the
same locations from a boat that was drifting slowly. The erratic nature of the fluorescence suggests that
phytoplankton productivity could be very different in two vary close locations at the same depth. Since
the highest fluorescence occurred roughly between the thermocline and 10 m, the irregularity of this
data is considered insignificant.
The chlorophyll a F0/Fa ratio at each station fell between 1.80 and 1.95 at the surface and
thermocline (Fig. 6). This is an indicator of healthy primary production levels. The relatively low
variance of chlorophyll a among the surface and thermocline also may be indicating the presence of
vertical mixing (Dussenberry 1999). In stations 52, 54, and 55 the chlorophyll a is slightly lower at the
surface then at the thermocline. This is likely due to the freshwater that remains stratified at the
surface which was seen in the density and salinity data. Overall the fluorescence does seem to drop
towards the head of the harbor, but the chlorophyll a data does not confirm this.
DO
The DO in each station seemed to be linked to phytoplankton production, remaining relatively
high from the thermocline to about 8m in depth at each station (Fig. 7). At each station the DO was
slightly lower at the surface, again indicating freshwater stratification from rainwater due to lack of
phytoplankton presence. In all cases other than station 52, the DO was in the excellent to extraordinary
classification in surface water and in the thermocline. The lower DO on the surface at station 52 is likely
linked to the low % transmission seen at this site, which in turn affects the phytoplankton production
and DO.
Variations among the DO data from the CTD and Winkler titration method were seen. In cases
where the Winkler titration values were high compared to CTD data, student error is assumed. It is
possible that the sample bottles were not flushed well enough after filling, before the application of the
O2 fixing chemicals were added. In cases where the CTD DO readings were abnormally low, it is
assumed that these measurements may actually depict the correct DO value, but are low due to vertical
mixing bringing bottom water up in pockets (Fig. 8 & 9).
Phytoplankton
Phytoplankton at each station resembled what was shown in the chlorophyll a data (Fig. 10). At
each station phytoplankton counts were slightly higher in the thermocline than at the surface. This was
expected due to the lower salinity at the surface. The station with the highest total abundance of
phytoplankton was Dockton (Fig. 10). In the net counts it was shown that there was a relatively even
distribution among phytoplankton genera (Table 2). The other stations did not have as high of a total
abundance at the surface, and had varying numbers of blooming vs. abundant, common and rare genera
(Table 2). No clear correlation between population abundance of genera and concentration can
therefore be drawn. Overall it seems that Chaetocerous and Detonula were the most common among
QMH as a whole (Fig. 11).
Grain size and TOC
Wide variances were observed between stations for collected sediment and total organic carbon
(TOC) samples. Stations 53 had a good mixture of clay, very fine sand and fine sand. Station 55 had a
majority of clay, and station 52 had a relatively even mixture of fine sand and medium sand. TOC related
to these follows what is expected. Station 55 had the highest TOC of stations that also had a grain size
analysis and station 52 had the lowest.
Conclusion
It is clearly seen that further in towards the head of QMH the flushing rate is slower than
towards the mouth. This can be seen in several parameters. Depending on what is happening with
weather and season, the isolated harbor can likely exhibit differing concentrations of DO and
phytoplankton.
References
Department of Natural Resources. 2004. Maury Island Environmental Aquatic ReserveFinal Management
Plan.
[IHD]Island History:Dockton. [Internet]. 2012. Vashon-Maury Island Heritage Association. [cited 2012
May 3] Available from: http://www.vashonhistory.org/dockton.html.
Dussenberry JA, Olson RJ, Chrisholm SW. 1999. Frequency Distributions of Phytoplankton Single-Cell
Fluorescence and Vertical Mixing in the Surface Ocean. Limnology and Oceanography. 44(2): 431-435.
Acknowledgements
A special thanks to Julie Masura for instructiona dn direction, and Cheryl Greengrove for
providing food. Also to Nanette for all of her help in the lab. I would also like to thank all of my
classmates for working well together.