diatom silicification changes in a high pco 2 environment: a mesocosm experiment
DESCRIPTION
Diatom silicification changes in a high pCO 2 environment: a mesocosm experiment . Kiely Shutt University of Washington Friday Harbor Laboratories Spring 2013. Diatoms: A Brief Overview. Major primary producers Most common phytoplankton Single celled, some are chain forming - PowerPoint PPT PresentationTRANSCRIPT
Diatom silicification changes in a high pCO2 environment: a mesocosm
experiment
Kiely ShuttUniversity of Washington
Friday Harbor LaboratoriesSpring 2013
Diatoms: A Brief Overview
•Major primary producers•Most common phytoplankton•Single celled, some are chain forming•Primary controllers of silica cycling in the ocean•Radial or bilateral symmetry•Diatoms have a silica requirement in order to build frustules
Silicification
Dissolved H4SiO4
Biogenic Silica SiO2
Upt
ake
MethodsBiogenic Silica Filtering
Rapid filter method by Paasche (1980)Prepped and ran on spectrometer using
Strickland and Parsons (1968)
Biogenic Silica/Diatom Cell CalculationBiogenic Silica
Liter
( Phytoplankton Cells
Liter
# Diatoms# Cells )
Research Questions
• Does biogenic silica differ between pCO2 treatments?
• What stressors affected biogenic silica and silica per diatom cell?– Micronutrient limitation? (Iron, Zinc)– Macronutrient limitation? (Nitrate, Silicate)– Microzooplankton grazing pressure?– Light limitation?
F(2,32)= 5.250, p=0.072
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 202
4
6
8
10
12
14Control
High
Dock
Drift
Time (Days)
Med
ian
Biog
enic
Sili
ca (µ
mol
L-1
)Biogenic silica through time
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200
5
10
15
20
25
0
5
10
15
20
25
Time (Days)
Med
ian
Nitr
ate
(µm
ol L-
1)
Med
ian
Biog
enic
Sili
ca (µ
mol
L-1)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200
5
10
15
20
25
0
5
10
15
20
25
Control Ni-trate
High Nitrate
Drift Nitrate
Dock Nitrate
Control BioS
High BioS
Drift BioS
Dock BioS
Time (Days)
Med
ian
Nitr
ate
(µm
ol L-
1)
Med
ian
Biog
enic
Sili
ca (µ
mol
L-1)
Statistically strong negative correlations for all treatment groups: ρ= -.923, -.913, -.884
Nitrate and biogenic silica through time
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200
5
10
15
20
25
30
35
40
45
50
0
5
10
15
20
25
30
35
40
45
50
Time (Days)
Med
ian
Silic
ate
(µm
ol L-
1)
Med
ian
Biog
enic
Sili
ca (µ
mol
L-1
)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200
5
10
15
20
25
30
35
40
45
50
0
5
10
15
20
25
30
35
40
45
50
Control BioS
High BioS
Drift BioS
Dock BioS
Control Sil-icate
High Silicate
Drift Silicate
Dock Silicate
Time (Days)
Med
ian
Silic
ate
(µm
ol L-
1)
Med
ian
Biog
enic
Sili
ca (µ
mol
L-1
)
Biogenic silica and dissolved silicate through time
Statistically strong negative correlations for all treatment groups: ρ= -.939, -.897, -.854
Grazing pressure
Treatment Spearman ρ
Control .382
High -.054
In order to show a significant association between silicification and grazing, our ρ value would need to be closer to -1 or 1.
Previous studies found increase in diatom silicification under grazing pressure (Pondaven et al 2007)
0 20 40 60 80 100 120 1400.5
1
1.5
2
2.5
3
3.5
4
4.5 Irradiance (inside mesocosms) µmol m-2 s-1
Dept
h (m
)
0 20 40 60 80 100 120 1400.5
1
1.5
2
2.5
3
3.5
4
4.5
T0 ControlT0 HighT0 DriftT11 ControlT11 HighT11 Drift
Irradiance (inside mesocosms) µmol m-2 s-1
Dept
h (m
)
PAR
(Eie
nste
ins m
-2 d
-1)
Adapted from (Martin-jézéquel et al 2000)
F(2,30)= 4.200, p=0.122
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200
20
40
60
80
100
120
140
160
180ControlHighDrift
Time (Days)
Pico
mol
e Si
lica
Cell
-1Picomole Silica Per Cell Through Time
Research Questions - Revisited
• Does biogenic silica differ between pCO2 treatments? Nope!
• What stressors affected biogenic silica and silica per diatom cell?– Micronutrient limitation? (Iron, Zinc)– Macronutrient limitation? (Nitrate, Silicate)– Grazing pressure?– Light limitation? Could be!
Conclusions
• No significant differences between pCO2 treatments for biogenic silica or silicification in diatoms
• Macronutrient limitation and grazing pressure were not affecting silicification in diatoms
• Light limitation likely to be the reason why we see the trends in silicification data as well as other unmeasured variables within our mesocosm system
Acknowledgements• Jim Murray• Robin Kodner• Kelsey Gaessner • Evelyn Lessard• Mike Foy• Barbara Paul• Amanda Fay• Molly Roberts• Kitae Park• Peers: Phil Gravinese, Kelly Govenar, Jen
Apple, Andrew Turner, Daneil Newcomb, Natsuko Porcino, Amy Stephens
• University of Washington - Friday Harbor Labs
• Mary Gates Endowment• Henry and Holly Wednt Endowment• Educational Foundation of America• Herbs Tavern