Global Warming and the Effects of Water Pollution on Aquatic Organisms
Zachary T. Guilford and Marjorie L. Brooks
Department of Zoology
Research Rookies
• Average global temperatures are expected to increase by 2 to
6˚C by the year 2100 (Meehl et al. 2007)
• Cold blooded aquatic organisms have a higher metabolic rate in
warmer waters (Bokolova and Lannig 2008).
• Faster respiration and higher food intake by aquatic organisms
means that they take in more of a toxicant.
• Copper has become an increasing issue due to widespread use
as brake pads on cars that emit copper dust, which can wash into
lakes and streams.
Toxicity of Copper at HigherTemperatures:
Implications of Climate Change
100
Mortality (%)
Introduction:
• Those findings indicated that Daphnia could serve as sensitive
indicator species to monitor the health of natural water bodies.
20
a
a
a
2
4
6
8
10
[Cu] µg/L
Fig. 1. Graph of the mortality rates the of Daphnia magna at the
temperatures of 22°C and 26°C. Blue lines represent regression
analysis. Letters represent significant differences compared to
controls.
Table 1. Experimental Constants
Daphnia magna
“water flea”
Photoperiod
16 h light : 8 h dark
2-days or less
pH at 19.5˚C
6.68
Animals / treatment
(10 x 3 reps)
30
Alkalinity
Static renewal
Hardness
(fresh water daily)
Experimental
endpoint
Mortality
Water source
Table 3. Results of Statistical Analyses
20 mg/L as CaCO3
12 mg/L as CaCO3
Little Grassy Lake
collected 4/22/2011
Table 2. 2 x 4 Factorial Design
[Cu] (μg/L)
a
0
Methods:
Test type
a
a
0
• We hypothesized that increased temperature would
significantly increase the toxicity of copper.
Organism age
• Subsequently, we decreased copper concentrations and
temperatures for the second set of experiments shown here.
60
a
• Even sublethal levels of copper can alter swimming performance
(Sandahl et al. 2007).
Test species
b
40
Water Temp (˚C)
22˚C
26˚C
0 μg/L (control)
3 reps
3 reps
2.5 μg/L
3 reps
3 reps
5 μg/L
3 reps
3 reps
10 μg/L
3 reps
3 reps
Regression analysis
22˚C
r2
0.01
p-value
0.46
Paired t-test
p-values comparing 22˚C
control to:
2.5 μg/L
0.15
5.0 μg/L
0.28
10.0 μg/L
0.17
(a)
26˚C
0.96
0.02
26˚C
0.19
0.09
0.02
Statistical Criteria:
• r2 values describe the amount
of change in mortality
explained by copper toxicity
under the conditions of the test
(i.e. 22 vs 26oC).
• p-values greater than an alpha
value of 0.05 indicate that a
comparison is not different in
more than 95% of cases, and
thus, is not a significantly
different treatment.
(b)
Acknowledgements:
Z.T.G. thanks Marjorie Brooks, Amanda Ellison, Kristen Jordan, Liz Trip, Tyler Hallman, Jessi
Hallman, Dr. Mike Lydy and Amanda Harwood for their help on my project. M.L.B. thanks
Z.T.G. for his dedication to designing and executing experiments despite inexplicable
cladoceran mortalities.
Pilot test results:
• Pilot tests with copper concentrations of 0, 10, 25, 50, and 100 μg
Cu/L at temperatures of 25, 27, and 29˚C caused 100% mortality in
every case (data not shown).
22oC
26oC
80
Results and Discussion:
Fig. 2. a) Treatments in water baths at different temperatures (example
from pilot experiment), b) Transferring Daphnia magna into test chambers
Definitive test results: Hypothesis supported.
• As hypothesized, results from the second tests conducted at 22
and 26oC with maximal copper concentration of 10 μg/L showed
that at the higher temperature, the same copper
concentrations were more lethal (Fig. 1).
Implications of Climate Change for Ectotherms (Fig. 1, Table 3):
• In ectotherms, metabolism, respiration, and dose increase with
warming.
• At 22°C, survival did not differ significantly from that of controls
regardless of copper concentration (p=0.48).
• At 26°C, significantly more animals died in treatments containing
10 μg Cu/L than in the control.
• Moreover, at 26°C, copper concentration explained 96% of
mortality.
• Water quality criteria for freshwater biota is 8.7 μg Cu/L. At slightly
more copper — 10 μg/L— mortality at 26oC averaged 63%, which
was significantly greater than the control mortality of 23% and 25%
average mortality at 22oC in the same copper concentration.
• These findings suggest that more stringent water quality criteria
are needed if important prey species for sport fishes are to survive
global warming .
Literature Cited:
Meehl, G. A., T. F. Stocker, W. D. Collins, P. Friedlingstein, A. T. Gaye, J. M. Gregory, A.
Kitoh, R. Knutti, J. M. Murphy, A. Noda, S. C. B. Raper, I. G. Watterson, A. J.
Weaver, and Z.-C. Zhao. 2007. Global Climate Projections. In Climate Change
2007. Eds: S. Solomon, et al. Cambridge University Press.
Sandahl, J. F., D. H. Baldwin, J. J. Jenkins, and N. L. Scholz. 2007. A sensory system at
the interface between urban stormwater runoff and salmon survival. Environmental
Science & Technology 41(8): 2998-3004.
Sokolova, I. M. and G. Lannig. 2008. Interactive effects of metal pollution and temperature
on metabolism in aquatic ectotherms: implications of global climate change. Climate
Research 37(2-3): 181-201.