Transcript Power Point Presentation

Phytoplankton Community
Composition, Abundance, and
Health on the International
Section of the St. Lawrence
River
Jessica Harold
Advisor: Dr. Michael Twiss
Clarkson REU Program
August 2, 2007
Outline
• Importance
– Hypothesis
• Methods
– Instruments
• Results &
Discussion
Why Study Phytoplankton of the St.
Lawrence River?
•
The Great Lakes-St. Lawrence River System holds 18% of the world’s
freshwater (Thorp et al. 2005)
•
Phytoplankton form the basis of aquatic food chains
Hypothesis
• Phytoplankton biomass will decrease upon entry
into the St. Lawrence River from Lake Ontario
– Disruption of phytoplankton physiology (Lewis et al.
1984)
– Increased predation by zooplankton and benthic
grazers
– Decreased nutrient availability
– Cell loss from the water column due to increased
flocculation (Ruiz et al. 2004)
• Phytoplankton community composition will
change due to changing environmental factors
Materials and Methods
• 19 stations were sampled over a two day
period
• Phytoplankton
– Health and composition determined by a
FRRF and a FluoroProbe, respectively
– Abundance determined using chlorophyll-a
abundance
Fast Repitition Rate Fluorometer
(FRRF)
• Determines photosynthetic
efficiency of whole phytoplankton
samples (Fv/Fm)
• Photosynthetic efficiency is a
measure of phytoplankton health
FluoroProbe
• Measures phytoplankton
biomass in each of four
divisions
• Nutrients
– Water collected from a depth of 6 m
using a 2 L Niskin bottle
– Analyzed water to determine total
phosphorus and dissolved silicate
• Chlorophyll-a
– Water is filtered and then chlorophylla is extracted from the filter paper
using acetone
– Fluorometer is used to determine
abundance
Results
100
90
80
70
60
50
40
30
20
10
0
%Cryptophyta and PE
rich cyanobacteria
%Heterokontophyta and
Dinophyta
% PC rich
Cyanobacteria
Distance from the MosesSaunders Dam (km)
179.0
152.1
132.9
114.6
95.9
77.3
58.3
39.2
21.4
% Chlorophyta and
Euglenophyta
3.1
Percentage of Phytoplankton
Division
• No significant changes in phytoplankton community
composition were found along the transect
•Dominated by
Chlorophyta (green
algae) and
Euglenophyta
• Both groups are
typically abundant
under eutrophic
conditions (Kalff
2002).
Phytoplankton Abundance and
Health
Photosynthetic efficiency remained relatively constant
Distinct trends seen in phytoplankton abundance
Concentration of Chlorophyll-a
(µm)
•
•
2.50
2.00
Total (>0.22µm)
1.50
Micro (>20 µm)
1.00
Nano (2-20µm)
Pico (0.22-2µm)
0.50
0.00
0.0
50.0
100.0
150.0
200.0
Distance from Moses-Saunders Dam
(km)
Nutrients
• Total dissolved phosphorus remains constant
• Dissolved silicate exhibits an interesting trend
8.0
7.0
SiO2 (µM)
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0.0
50.0
100.0
150.0
Distance from the Moses-Saunders Dam (km)
200.0
Discussion
• Total dissolved phosphorus and chlorophylla are not correlated
– Phosphorus is not limiting
• Silicate concentrations
– Increase due to elevated turbulence as the
river becomes isothermal
• Phytoplankton abundance initially
decreases, but then recovers
– The decrease is not due to poor health
• Hypothesis: decrease is due to
increased predation or disrupted
physiology
– Increase in abundance
• Hypothesis: phytoplankton have
adapted to new environment, or
predation has decreased
Acknowledgements
•
•
•
•
Advisor Dr. Michael Twiss
Tiffany Basara and Dave Page
Co-worker Kyleigh Gloska
Cristina Gauthier and all the REUs!
Questions?
Literature
Ruiz, J., Macias, D, Peters, F. 2004. Turbulence increases the average settling
velocity of phytoplankton cells. Proc. Nat. Acad. Sci. 101:17720-17724.
Lewis, M. R., E. P. W. Horne, J. J. Cullen, N.S. Oakley & T. Platt. 1984.
Turbulent motions may control phytoplankton photosynthesis in the upper
ocean. Nature 311: 49-50; doi 10.1038/311049a0.
Thorp, J.H., Lamberti, G.A., and Casper, A.F. 2005. St. Lawrence River Basin.
In Rivers of North America, eds. A.C. Benke and C.E. Cushing, pp. 9831018. Boston: Elsevier Academic Press.
Kalff, Jacob. 2002. The Phytoplankton. In Limnology, p. 316. Upper Saddle
River, New Jersey: Prentice Hall.
Basu, B.K., Klaff, J., Pinel-Alloul, B. 2000. Midsummer plankton development
along a temperate river: the St. Lawrence River. Can. J. Fish. Aquat. Sci. 57
(Suppl.1): 7-15.
FRRF details
• The FRRF was programmed to measure
the ratio of variable chlorophyll-a
fluorescence (Fv) to maximal chlorophyll-a
fluorescence (Fm)
• Fo=basal chlorophyll-a fluorescence