1. Research was conducted at the lighthouse dock in Mukilteo,
Washington (figures 6 & 7) using a 1.7 liter Niskin bottle to gather
samples at regular monthly increments between the months of June
and September 2011. A YSI 650 was used to determine the halocline
of the water, where the samples were taken. The water samples were
strained through a 20 μm plankton net and preserved for later counting.
The plankton was placed on a flat surface for 24 hours prior to counting
to allow the samples to settle to the bottom. A 5 milliliter sample was
taken from the bottom, collecting as much plankton as possible. The
sample was then allowed to settle once again, before counting the
bottom one milliliter for identification (figures 4 & 5).
Temporal Analysis of Plankton Abundance in Mukilteo Washington
Student Names: Breanne Ward and Bryan Jacobson; Advisors: Ardi Kveven and Robin Araniva
Ocean Research College Academy, Everett, Washington
The Ocean Research College Academy (ORCA) is an early
college program based in Everett, Washington designed for high
school juniors and seniors who are interested in learning through
intensive studies based in the local estuary. In an attempt to better
understand the lifestyle and habits of plankton, an experiment was
conducted to gather data concerning plankton temporal populations
by species. At the base of the marine food chain, the abundance of
plankton within Possession Sound is a key factor to the health and
stability of the ecosystem around it. Phytoplankton also has an
irreplaceable role in the biogeochemical cycle of the atmosphere,
recycling and reusing carbon within the atmosphere (Baines,
Twining, Brzezinski, Nelson & Fisher. 2010). Research suggests that
the populations of plankton peak early summer and decrease
afterwards. This trend has implications for the impact of climate
change and weather patterns on ecosystem stability.
There was a peak in plankton populations during the blooming
season, in early July. The amount by which the plankton population
increased is substantial: with 2,208 individuals for the July tow as
opposed to 388, 354 and 383 plankton specimens for the other three
months. Of all the plankton identified, 12 separate species of
phytoplankton were discovered – making up 80% of the total species
distribution – and 3 species of zooplankton, completing the other
20%. All plankton identified were graphed by species (figure 3) to
show the dramatic amount of Skeletonema, Thalassiosira,
Chaetoceros and Pseodonitschia versus the much smaller numbers
of the other species counted.
Introduction
Methods
Figure 4 Figure 5
Figure 6 Figure 7
Results
Results
0.0
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16-Jun 6-Jul 26-Jul 15-Aug
CalculatedValues(μg/L)
Date
Temporal Nutrient Levels in Possession Sound
Phosphate
Silica
Nitrate
Nitrite
Ammonia
0
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PlanktonCounted
Tow Dates
Temporal Plankton Abundance by Species
Chaetoceros:
Pseudonitschia:
Skeletonema:
Thalassiosira:
Figure 2 Figure 1
0
200
400
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TotalCounted
Total Plankton Identified by Species
Figure 3
The four most abundant plankton species, which made up 97% of the total amount
counted, were graphed over time to show the growth and decline of each species (figure 1).
All four species increase in numbers between the months of June and July. Some increase
dramatically, such as Skeletonema and Chaetoceros, while others increase in much smaller
numbers, as in the case for Pseudonitschia and Thalassiosira. All four species again
decrease following the month of July, Skeletonema and Chaetoceros again dropping
drastically, while Pseudonitschia and Thalassiosira encounter a much smaller change. The
first difference in trends occurs between the months of August and September when three of
the species increase in counts while Pseudonitschia continues to decrease.
The significant plankton bloom in July could be due to numerous different conditions.
There was a slight increase in the average temperature between June and July,
approximately six degrees, in addition to the slight average rainfall of .03 inches daily
("Weather history,") and the input of the flowing Snohomish River all equate to perfectly
stratified oceanic conditions for a plankton bloom.
Another comparison can be made between nutrients data collected at Mukilteo
Washington for June, July and August with the plankton counts. The concentration (in μg/L)
for five different compounds found within the water column is shown over time in figure 2.
Similar to the plankton data, the nutrients concentration also increases in the end of June and
beginning of July. The most abundant compound (silica) is a crucial component in plankton
growth. The planktonic diatoms found most commonly in our counts use the silica to form
their transparent siliceous cell walls (Baines, Twining, Brzezinski & Fisher. 2010). An increase
in the amount silica in the water would likely lead to an increase in plankton abundance. The
second most concentrated compound in the water column was phosphate; also critically
important to the growth of phytoplankton. The cell membranes of phytoplankton contain
phosphorus-based lipids called phospholipids, which must be produced for them to grow
(Martin, Van Mooy, Heithoff & Dyhrman, 2010). Inorganic nitrogen and ammonium are also
used by the phytoplankton to help anabolize proteins (Falkowski, 1975,) and although they
are not as crucial as the other compounds mentioned, they remain helpful to plankton growth.
The nutrients levels drop at the same time the plankton counts do, between July and August.
The plankton took in the nutrients, and as the nutrients disappeared so did the plankton.
Another component possibly contributing to plankton abundance would be a combination
of the surface area of the plankton and the upwelling/weather conditions of the area. The
most abundant plankton species counted all have the commonality that they are larger
phytoplankton. The surface area of the plankton makes them more likely to reside in the
upper layers of the water, due to the fact that they sink much slower than the smaller
phytoplankton and heavier zooplankton. The small amount of zooplankton identified could
also contribute to the abundance of phytoplankton. The zooplankton feed on the
phytoplankton, with a small zooplankton population the phytoplankton have one less predator.
Conclusion
Our data results match the hypothesis that the plankton
populations increase early summer and decrease afterwards.
66.2% of the counted plankton came from July, and 77.9% of the
counted plankton from June and July, leaving only 22.1% for the
ending summer months.
In the future it would be interesting to take plankton and
nutrients data together to more accurately look at the correlation
between the two, as well as tracking the temporal abundance of
plankton for a longer period of time. It could also potentially be
beneficial to incorporate a chlorophyll sensor into further research
in order to gather complimentary data on phytoplankton
concentrations.
Sources
Baines, S. B., Twining, B. S., Brzezinski, M. A., Nelson, D. M., & Fisher, N. S.
(2010). Causes and biogeochemical implications of regional differences
in silicification of marine diatoms. Global Biogeochemical Cycles, 24(4),
n/a. doi:10.1029/2010GB003856
Falkowski, P. G. (1975). Nitrate uptake in marine phytoplankton: comparison
of half-saturation constants from seven species. ASLO, 20(3), 412.
Retrieved from http://www.aslo.org/lo/toc/vol_20/issue_3/0412.pdf
Martin, P., Van Mooy, B., Heithoff, A. & Dyhrman, S. (2010, December 17).
Efficient phosphorus use by phytoplankton. Science Daily, Retrieved
from http://www.sciencedaily.com/releases/2010/12/101217145928.htm
Tilman, D., Kilham, S. S., & Kilhman, P. (1982). Phytoplankton community
ecology: the role of limiting nutrients. Annual Review of Ecology and
Systematics, 13, 349-372.
Weather history and Data Archive. (n.d.). Retrieved from
http://www.wunderground.com/history/
Acknowledgements
We would like to thank all the faculty and students of the ORCA
program for their help. Specifically Ardi Kveven and Robin Araniva for
their equipment, guidance and support.