A Survey of Diel-Vertical Migration of Freshwater
Zooplankton at Pinchot Lake
Eric Holtzapple
Can we locate two populations that would
show different DVM patterns within a single
lake?
HYPOTHESES
Null
H0: There will be no difference in DVM of
freshwater zooplankton between shallow and
deep areas of a single lake.
Alternate
H1: Freshwater zooplankton will exhibit
more pronounced diel vertical migration in
deeper areas of the lake.
Samples Were Collected from
three depths at two locations in
the lake
Results
Location 1 Zooplankton
A
Location 2 Zooplankton
B
06:00
12:00
3
Zooplankton (#/m )
3
Zooplankton (#/m )
0
0
200
400
600
800
1000
1200
200
400
600
800
1000
1200
0
0
Depth (m)
4
Location 2
copepods
4
daphnia
5
6
6
7
7
C
D
18:00
200
400
600
800
1000
0
1200
200
400
600
D
18:00
24:00
Zooplankton (#/m 3)
Zooplankton (#/m 3)
Zooplankton (#/m 3)
3
Zooplankton (#/m )
0
C
24:00
800
1000
0
1200
200
400
600
800
1000
0
1200
0
1
1
1
1
2
2
2
2
3
4
3
4
Depth (m)
0
Depth (m)
0
Depth (m)
0
3
4
5
5
6
6
6
6
7
7
7
7
–No Significant differences between the separate time plots
B
6:00
5
10
15
20
25
30
A
0
5
10
15
20
25
12:00
Temperature (C) and Dissolved Oxygen (mg/L)
Temperature (C) and Dissolved Oxygen (mg/L)
0
B
6:00
35
0
1200
Location 2 Environmental Factors
12:00
Temperature (C) and Dissolved Oxygen (mg/L)
0
1000
– (C) and (D) at 3m
Location 1 Environmental Factors
A
800
Daphnia
– No Significant differences between the separate time plots
Daphnia
– (B) and (D) at 0m
– (C) and (D) at 6m
600
Figure 2 shows data of relative abundance of copepods and daphnia at location 2 with respect to time.
+/- Standard error accounting for the differences between the replicates are displayed with each data
point.
Copepods
Copepods
400
4
5
Figure 1 shows data of relative abundance of copepods and daphnia at location 1 with respect to time.
+/- Standard error accounting for the differences between the replicates are displayed with each data
point.
200
3
5
30
35
5
10
15
20
25
30
Temperature (C) and Dissolved Oxygen
(mg/L)
35
0
0
0
5
10
15
20
25
30
35
0
1
1
2
1
2
3
4
Depth (m)
2
3
temp
4
Dissolved Oxygen
2
Depth (m)
1
3
4
3
temp
5
5
6
6
6
6
7
7
7
7
C
D
18:00
Temperature (C) and Dissolved Oxygen (mg/L)
0
5
10
15
20
25
30
5
C
24:00
0
5
10
15
20
25
30
D
18:00
Temperature (C) and Dissolved Oxygen (mg/L)
35
24:00
Temperature (C) and Dissolved Oxygen (mg/L)
35
0
5
10
15
20
25
30
Temperature (C) and Dissolved Oxygen (mg/L)
35
0
0
0
1
1
1
1
2
2
2
2
4
3
4
Depth (m)
0
Depth (m)
0
3
Dissolved Oxygen
4
5
3
4
10
15
20
25
30
35
4
5
5
5
6
6
6
6
7
7
7
7
Figure 3 shows data of dissolved oxygen and temperature at location 1 with respect to depth.
Dissolved oxygen within the individual graphs above, was considered to be a significant drop with
depth.
5
3
5
Figure 4 shows data of dissolved oxygen and temperature at location 2 with respect to depth.
Temperature and dissolved oxygen within the individual graphs above, was found to drop significantly
with depth.
Dissolved Oxygen
Temperature
Dissolved Oxygen
Temperature
– No Significant differences between the separate time plots
–No Significant differences between the separate time plots
– No significant difference between the separate time plots
–No Significant differences between the separate time plots
Conclusions
Location 1
3
5
Depth (m)
•Three plankton nets with
153μm mesh were attached (at
designated sample collection
depths) to a telescopic
fiberglass pole anchored to the
front of a boat.
•Dissolved oxygen and
temperature were also
collected.
•Samples were collected over a
distance of 60 feet at a rate of 1
foot per second which was
tracked by GPS.
•Zooplankton Samples were
Preserved in 5% formalin and
were later counted in their
entirety in the lab.
•Two-way ANOVA’s with
Bonferroni post tests were used
to analyze the data.
3
Depth (m)
2 replicates/time
06:00, 12:00, 18:00, 24:00
2
2
Depth (m)
Location 2
0.000 m
1.524 m
3.048 m
Depth (m)
Location 1
0.000 m
3.048 m
6.096m
1
1
Depth (m)
Diel Vertical Migration of Zooplankton in
Lakes
DVM is a pattern of movement that
organisms such as zooplankton undertake over a
twenty-four hour time span. Two major reasons
that zooplankton exhibit DVM are predator
avoidance and for metabolic advantages.
The Predator Avoidance Hypothesis states
that visual predators such as fish feed near the
surface at shallow depths during the day. In
response, zooplankton migrate to deeper, darker
depths to avoid being seen by the fish (Bollens &
Frost, 1989). At night, zooplankton migrate
toward the surface, where food is found in
greater abundance (Lampert, 1989; Loose &
Dawidowics, 1994).
The Metabolic Advantage Hypothesis states
that zooplankton migrate to deeper waters during
the day where the water is cooler. The cooler the
water, the less energy zooplankton must exert
(Loose & Dawidowicz, 1994). They Come to the
surface at night to feed when the surface layer is
cooler.
In some lakes, DVM is not observed.
Zooplankton tend to live in deeper waters both
day and night when food is abundant at these
deeper depths. Also, stratification and oxygen
profile can limit the depth to which zooplankton
can migrate. Anoxic conditions observed in these
stratified waters do not favor DVM as zooplankton
are unable to migrate into the water lacking
oxygen. In shallow waters, there is little benefit
for DVM as light intensities, oxygen, and
temperature do not drastically fluctuate between
surface and deeper waters.
RESEARCH QUESTION
Methods
Depth (m)
Introduction
Department of Biological Sciences, York College of Pennsylvania
•Copepods at location 1 show an increase in abundance at both surface and bottom at
24:00. Although this may indicate migration, it is not the expected trend of vertical
migration.
•Although Daphnia do appear to decrease at midday at the surface in this experiment, this
change is not significant. Perhaps this trend would become significant if the amount of
replicates were increased.
•A future study could be conducted to determine where the zooplankton are migrating, since
it isn’t vertically within the water column.
•Copepods did show a change in abundance at Location 1, but not at Location 2. This can
be expected because light intensities at Location 2 are not as variable, thus the benefits of
DVM are not as great.
•Oxygen and temperature profiles for each Location indicate that the waters are indeed
stratified, though the deeper depths were not anoxic to the point of being uninhabitable.
Literature Cited
Bollens & Frost, B (1989). Zooplanktivorous Fish
and Variable Diel Vertical Migration in the Marine
Planktonic Copepod Calanus pacificus. Limnology
and Oceanography. 34, 1072-1083.
Lampert, W (1989).The adaptive significance of diel
vertical migration of zooplankton. Functional
Ecology. 3, 21-27.
Loose, C, & Dawidowicz, P (1994). Trade-Offs in
Diel Vertical Migration by Zooplankton: The Costs
of Predator Avoidance. Ecology. 75, 2255-2263.
Acknowledgements
I would like to thank Dr. Nolan for dedicating
her time and expert advice into this study.