Quantifying ecological change in diatom diversity in paleolimnological records from lakes in Sweden.
Jacob Champeau and David Strong, Faculty Advisor: Dr. Krista Slemmons
Department of Biology, University of Wisconsin-Stevens Point
INTRODUCTION
● Diatoms preserve in lake sediment and are sensitive to changes in lake chemistry,
serving as indicators for environmental change.
● The effects on atmospheric nitrogen on lake biota is not as well-understood as the
effects of other elements such as phosphorous but changes in limiting nutrients in
Scandinavian countries and the U.S Rocky Mountains have been attributed to
increased atmospheric nitrogen deposition1,2.
● Changes in diatom community structure over time can indicate changes in
atmospheric nitrogen deposition over time.
● This study focuses on determining if diatom species richness varies regional in
Swedish lakes with degree of atmospheric nitrogen deposition (Table 1, Fig 1).
● Knowledge of the effect of nitrogen on species richness and diversity can allow for
predictions of nitrogen thresholds required to elicit ecological change and can
inform policy making decisions in setting allows for predictions environmental
conditions to be estimated for the time period lining up with that segment depth.
•Cores collected the deepest part from four
.
How has species richness changed
over time and between regions in Swedish lakes?
Furbosjon
Barsjon
.-5
0
•Extruded 0.5 cm segments and processed for
diatoms (Fig 2).
5
 Enumerated and identified diatoms via
microscopy in top (modern) and bottom (past)
core segments.
10
Fig 4. A) Diatom stratigraphy of key diatom
species linked to differences in mixing depth3:
D. stelligera relatively shallow mixing and C.
bodanica relatively deeper mixing. Both lakes
indicate change over time in regard to mixing
depths. B) Sample diatom specimens taken
from Lake Barsjön. Cyclotella bodanica (left),
B) Discostella stelligera (right).
15
20
25
 Dated each core using 210Pb dating techniques.
30
35
 Calculated and compared the species relative
abundance and richness using Rarefaction to
standardize to 300 valves per sample.
 Calculated species evenness and compared
between times and among lakes.
40
0
20
0
20
40
60 0
20
40
0
Relative percent abundance
CONCLUSIONS
 Compared species composition across lakes.
Fig 2. Extruded lake sediment core from
Lake Barsjön, Southwest Sweden.
RESULTS
●Based on limited sample size, no difference
In species evenness spatially, however
there is an indication of difference
temporally.
● Apparent differences in species
Composition of two key species over time.
● No apparent difference in species richness.
Fig 5. Lake Lilla Ulvattnet, Southwest
Sweden, coring site.
FUTURE WORK
1. Analysis of top/bottom sections in two more Swedish lakes: Lilla Ulvattnet and Ysjon.
2. Detailed diatom counts for all depths in the four study lakes.
3. Comparisons of similar time periods between lakes once cores are dated.
4. Conduct Loss-on-ignition data analysis and compare between lakes.
5. Conduct beta-diversity and community turnover analyses
Figure 3. Comparison of species evenness in the A) Past to B) Modern samples. No difference
in evenness between Barsjön and Furbosjön in the past (t-test, p=0.93) or in the modern
samples (t-test, p=0.75).
Average Species Richness (ES300)
17.5
The future analysis of a larger data set will allow for a more thorough look at
environmental change from both a wider geographic region and a more comprehensive
time span.
LITERATURE CITED
1Elser,
J., Anderson, T., Baron, S., Bergstrom, A., Jansson, M., Kyle, M., Koren, R., Steger, L., Hessen, Dag.
Shifts in Lake N:P Stoichiometry and Nutrient Limitation Driven by Atmospheric Nitrogen Deposition.
2009. Science 326: 835-837.
2Bergstrom, A.L., Jonsson, A., Jansson, M. Phytoplankton responses to nitrogen and phosphorus
enrichment in unproductive Swedish lakes along a gradient of atmospheric nitrogen deposition. 2008.
Aquatic Biology 4: 55-64.
3Saros, J., Stone, J., Pederson, G., Slemmons, K., Spanbauer, T., Schliep, A., Cah D., Williamson, C.,
Engstrom, D. Climate-induced changes in lake ecosystem structure inferred from coupled neo- and
paleoecological approaches. 2012 Ecology 93: 2155-2164.
17
16
15.5
How does species richness vary spatially among regions with different
atmospheric deposition?
Barsjon
B
-10
16.5
QUESTIONS
Cyclotella bodanica
Discostella stelligera
Furbosjon
Swedish lakes via HTH gravity corer in Summer
2014.
Table 1. Select characteristics of study lakes.
DIN = dissolved organic nitrate2.
Region Lake Name
Lake DIN Ave for region
area (kg N km-2 yr(km2)
1)
Lilla
0.1913
800
Ulvattnet
1
Bärsjön
0.5689
Furbosjön
0.5894
434
2
Ysjön
0.2864
Figure 1. Location of study site situated in
southern Sweden. Region 1 represents high
nitrogen deposition areas and is the location of
Lake Bärsjön. Region 2 represents relatively
lower nitrogen deposition and the location of
Lake Furbosjön. Regions were designated and
map was adapted from Bergström et al. 20082.
A
Depth (cm)
●Paleolimnology is the study of the sedimentary record of lakes and can be used to
reconstruct environmental history of a region beyond recorded history.
RESULTS
METHODS
15
14.5
14
13.5
Furbosjon
Barsjon
Past
Furbosjon
Barsjon
Modern
Figure 4. Comparison of species richness in Past and Modern samples based Analytic
Rarefaction 1.3 (n=300 [ES300] for every sample, S. Holland). No difference in evenness
between Barsjön and Furbosjön in the past.
ACKNOWLEDGEMENTS
Funding provided by University Personnel Development Committee New faculty Grant, Undergraduate
Education Initiative Grant.
Special thanks to: Caleb Slemmons for field work, Dr. CT Hess and John Cummings for 210Pb dating analysis, Dr.
Kristin Engstrom and Dr Jannie Linneberg for Sweden logistics, and Dr.
Chris Hartleb, Dr. Pete Zani and Dr. Samantha Kaplan for lab space and equipment.