Transcript Spatiotemporal Distribution of Phytoplankton Standing Crop

The Deep Chlorophyll Maximum
in Lake Superior
2000 HN210 Chl
M.T. Auer, L.A. Bub and K.D. Elenbaas
Department of Civil and Environmental Engineering
Michigan Technological University
seasonal development of the DCM
HN Transect - Chl (µg•L-1)
4/28/00
0.0
1.0
6/22/00
2.0
0.0
1.0
7/30/00
8/25/00
0.0
0.0
2.0
1.0
2.0
1.0
10/20/00
0.0
2.0
0
0
0
0
0
40
40
40
40
40
80
80
80
80
80
120
120
120
120
120
H N 2 10
160
160
H N 2 10
H N 2 10
H N 2 10
160
160
1.0
2.0
H N 2 10
160
Reported in both freshwater and marine systems and
related to a variety of environmental factors
System
Factor
Reference
Adriatic Sea
Zooplankton grazing
Nutrient levels, distribution
Revelante and Gilmartin
1995
Baltic Sea
Ciliate grazing
Sedimentation
Kononen et al. 1998
Mediterranean Sea
Zooplankton grazing
Nutrient levels, distribution
Physical factors
Gould and Wisenburg
1990
Lake Tahoe
In situ growth
Coon et al. 1987
Lake Michigan
In situ growth
Sedimentation
Zooplankton grazing
Sedimentation
Shade adaptation
Brooks and Torke 1977;
Fahnenstiel and Scavia
1987
Finger Lakes of New York, New York City Reservoirs, et al.
In Lake Superior
Year
Investigator
Factor
1966
Olson and Odlaug
Putnam and Olson
Light
Temperature
Zooplankton grazing
1975
Watson et al.
Factors other than depthvariable settling
differences
1978
Munawar and Munawar
In situ growth
1983
Fahenstiel and Glime
In situ growth
2001
Zhou et al.
Light – nutrients
Thermocline tilting
But it comes down to two camps …
The Ecological
The Physical
Enhanced growth
due to conditions of
light, temperature,
nutrients, grazing,
particularly suitable
for some or all taxa
Accumulation of
phytoplankton due to
differences in settling
velocities over the
metalimnion
Or more simply,
“Is the DCM a great place to live
… or are they just hanging around?
The Ecological
For phytoplankton:
• nutrient supply
• temperature optima
• light efficiency
• chlorophyll adaptation
• grazing pressure
chemoautotrophs
nutrient supply
DIP (µgP∙L-1)
0.0
0.5
1.0
1.5
C:P Ratios (molar)
2.0
0
0
500
1000
1500
0
20
50
40
Depth (m)
60
100
80
100
120
150
140
160
200
180
Feb On
250
May On
May Off
Jun On
Jun Off
Jul On
Jul Off
nutrient supply
ELF-APA Data from
Vickie Morris, MTU
ELF
Gloeocystis
ELF
Fragilaria
ELF (Enzyme-Labeled Fluorescence) is an alkaline phosphatase
substrate which yields a bright yellow-green fluorescent precipitate
upon enzymatic cleavage.
nutrient supply
APA Vmax
ELF Activity
Algal Biomass
-1
(µgChl·L )
µM/min
0.0
0
0.073
0.5
1.0
1.5
2.0
% of cells
81%
20
0.037
Depth (m)
61%
0.025
40
60
80
100
65%
temperature optima
Optimum T @ ~15 °C
T in DCM ~ 4-5 °C
Primary Production
(mgC∙µg Chl∙L-1∙hr-1)
0.6
0.4
0.2
0.0
0
5
10
Temperature (°C)
15
20
light efficiency
0
HN090 - JD 239
0.30
HN 210-30m
-10
0.20
0.10
0.00
0
200
400
600
800
1000
1200
1% light level, m
Specific Production
(mg Chl• µg Chl-1 hr-1 )
8/25/00
-20
3-5%
1-3%
-30
0.6-1%
Light Intensity
(µE m-2 s-1)
-40
-50
300 350 400 450 500 550 600 650 700
wavelength, nm
chlorophyll adaptation
July and August
Offshore Stations
POC (mg/L)
C:Chl (mg/ug)
0
100
200
300
0.00
400
0.05
0.10
0.15
0.20
0
0
20
40
Depth (m)
Depth (m)
10
20
30
40
50
60
60
carbon data courtesy of Noel Urban
Shade adaptation does account for some of the DCM, but certainly
not all of it. The maximum is also present in the carbon data.
grazing pressure
0m
temperature
(0-20 m)
zooplankton
(15-30 m)
chlorophyll
(25-40 m)
10 m
20 m
30 m
40 m
50 m
60 m
OPC scans provided by David J. Osterberg, MTU
let’s ask the bacteria
Production
(mg C m-3 h-1)
0.00
0.05
0.10
0.15
0.20
Carbon Source Utilization
Chlorophyll (mg L-1)
0.5
1.0
1.5
2.0
22m
PC2
0.0
5m
50m
August 1999
HN210
PC1
… and furthermore
Excretion
BCR
(mg C m-3 h-1)
0.00
0.25
(mg C m-3 h-1)
0.50
0.00
0.25
0.50
Depth (m)
0
25
50
75
100
Carbon excretion by actively photosynthesizing phytoplankton is able to
satisfy the bacterial carbon requirement (BCR) only in the surface waters.
The Physical
s et t ling v eloc it y (c m ∙ s - 1 )
6
8
10
12
0
20
40
Dept h (m)
60
80
100
120
140
160
180
velocity 
g

solid
 liquid  d 2
18 m
The Expanding Universe
Chl (µg/L)
T °C
6/22/00
7/30/00
9/24/00
Conversation Overheard at 30m …
Hey! Is this
a great place
to live?
Naw.
We’re just
hangin’ around.
For field support:
Captain & Crew of the
R/V Laurentian
For assistance in data analysis:
Jae Jeong, MTU
For data:
Angela Cates, LLO
Judy Budd, MTU
Kim Elenbaas, MTU
Sarah Green, MTU
Vickie Morris, MTU
Dave Osterberg, MTU
Noel Urban, MTU
For financial support:
National Science Foundation
acknowledgements: