effect of the relative hardness of water on crayfish abundance and size
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Effect of the Relative Hardness of Water on Crayfish Abundance and Size. Sarah Deel Chris Brassell Ben Wade Jeff Rosemond. Crayfish Collected during the experiment. Introduction. Freshwater Crayfish naturally inhabit most all the continents. - PowerPoint PPT PresentationTRANSCRIPT
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Effect of the Relative Hardness of Water on Crayfish Abundance and Size
Sarah DeelChris Brassell
Ben WadeJeff Rosemond
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Crayfish Collected during the experiment
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Introduction
• Freshwater Crayfish naturally inhabit most all the continents.
• The US is home to two families (Reynolds and Souty-Grosset 2012).– Astacidae– Camvaridae
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Introduction
• Crayfish play an important role in trophic structure (Edwards et al. 2009).
• The amount of Ionic Calcium in water is critical to crayfish growth and survival. (Stelxer and Burton 2011).
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Introduction
• Growth for freshwater crayfish is limited by the exoskeleton.
• To increase in size the crayfish must molt.
• Ionic calcium in the water aids in the hardening of the new exoskeleton (Hammond et al. 2005).
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Introduction
• The calcium concentration in surrounding water may be a limiting factor for the survival of crayfish during postmolt (Cairns and Yan 2009).
Crayfish collected from Sinking Creek
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Introduction- A Recent Study
• Comparisons of crayfish number and weight were done in the in the Lake Michigan drainage basin. – Ford River (hard water) – Baraga Creek (soft water)
• Densities of crayfish were higher in the Ford River (Stelzer and Burton 2011).
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Introduction- A Recent Study
• Water hardness linked to number and growth of the two populations of crayfish
• The researchers could not establish causality(Stelzer and Burton 2011).
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Introduction- Another Study
• Juvenile crayfish were placed in aquariums treated with varying levels of Ca2+
• The survival rate of crayfish (70-80%) was significantly greater in high calcium environments than low (Hammond et al. 2005).
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Based on Previous Studies…
• Hypothesis: we will find a greater density of crayfish in waterways with higher levels of Calcium concentrations.
• The specific size and weight is difficult to predict
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Introduction
• We predict the average length of crayfish to be over 7.5cm in sinking creek, while crayfish in the softer streams will be less than that, as well as less numerous.
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Introduction- Sampling Sites
• 3 chosen sites:
1) Sinking Creek: high hardness
– dolostone and limestone (U.S. Geological).
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Introduction- Sampling Sites
• Both dolostone and limestone leech metals cations– limestone leeches calcium– dolostone leeches both magnesium and
calcium.Limestone
Image from: http://geology.com/rocks/limestone.shtml
Dolostone
Image from: http://core.ecu.edu/geology/harper/Sedimentary/display_new.cfm?ID=7
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Introduction- Sampling Sites
2) Little Stony Creek for its low level of hardness.
– sandstone and granite (U.S. Geological).
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Introduction- Sampling Sites
3) Tom’s Creek: very high hardness
– elbrook formations: dolostone and limestone (U.S. Geological).
– Runoff/ pollution
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Methods
• Water hardness
• In this experiment, water hardness was tested using the LaMott’s water chemistry kit.
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Sarah Using the LaMott Kit to Test Water Hardness
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Methods
• USGS Water-Quality Information• General guidelines for classification of waters
are: • 0 to 60 mg/L as calcium carbonate is classified
as soft• 61 to 120 mg/L as moderately hard• 121 to 180 mg/L as hard• more than 180 mg/L as very hard.
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Methods
• We visited each stream varying times between 15 October and 26 November.
• Hardness kit used to evaluate water hardness and see if there was any variation during the time span of this experiment. – Hardness was measured 3 times on two occasions and
the average was used in the results
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Methods
• A 25 meter transect was the designated sample area for each stream.
• Crayfish were collected by hand
• In each stream zone we systematically collected crayfish in 30 minute intervals.
• Crayfish abundance in that zone was recorded.
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Methods
• Each crayfish we caught was put into an ethanol bucket for storage.
• Length and weight was measured and recorded in the lab
• ANOVA tests used for comparison• Regression and r2 used for signifigance
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Equipment
• Several buckets• Ethanol• Ruler • Scale• LaMott hardness kit
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Chris and Jeff Measuring Crayfish
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Weighing the Crayfish
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Chris measuring length
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Ben working out the statistics
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Results
Mean Length (cm) Mean Mass (g) Abundance
Mean Hardness
(ppm)
Sinking Creek 11.03182 14.79409091 18 121.2727
Little Stony Creek 9.236364 9.848181818 11 28.54545
Tom's Creek 8.388235 4.770588235 17 232.9167
• Largest Measured Growth Indicators: Sinking Creek
• Smallest Measured Growth Indicators: Little Stony Creek
• Highest Measured Hardness: Tom’s Creek• Unanticipated
• Lowest Measured Hardness: Little Stony Creek
Observed Means For Each Variable:
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Between Population Variance for each Variable
VariableBetween Population Variance
(P-value)
Hardness 7.74843E-26
Mass 5.17261E-05
Length 0.000658702
Abundance 0.059667724
• Almost all measured variables show significant variance between each population
• Abundance shows no significant variance
• Where is significant variance coming from?
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T-TestsStreams Comparison Hardness Mass
Length
Sinking vs. Tom’s 2.62164E-05 0.0067290.0023184
52
Little Stony vs. Tom’s 1.0486E-07 0.2055810.8138352
62
Little Stony vs. Sinking 1.36484E-05 0.1072140.0859850
66
• Compared each variable between each population using t-tests (post-hoc not available)
• Hardness differences are unilaterally significant
• Sinking Creek vs. Tom’s Creek
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Comparisons to Hardness Across Populations
Abundance:
Hypothetically, this trend should hold. Right?
0 50 100 150 200 250 3000
1
2
3
4
5
6
R² = 0.488450801065093
Abundance vs Mean Hardness
Mean Hardness (ppm)
Abun
danc
e
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Comparisons to Hardness Across Populations
Wrong.• Mass:
0 50 100 150 200 250 3000
5
10
15
20
25
R² = 0.0682925825879584
Mean Mass vs Mean Hardness
Mean Hardness (ppm)
Mea
n M
ass (
g)
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Comparisons to Hardness Across Populations
• Length
0 50 100 150 200 250 3000
2
4
6
8
10
12
R² = 0
Mean Length vs Mean Hardness
Mean Hardness (ppm)
Mea
n Le
ngth
(cm
)
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Why is R^2 So Low?
• Strange Observation– Shouldn’t growth be correlated to [CaCO3]?– Why that not observed?– Most likely confounding variable in populations
somewhere.
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Tom’s Creek Omitted
• Mass:
0 20 40 60 80 100 120 140 1600
5
10
15
20
25
R² = 0.507538825418463
Mean Mass vs Mean Hardness (Tom's Creek Ommitted)
Mean Hardness (ppm)
Mea
n M
ass (
g)
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Tom’s Creek Omitted
0 20 40 60 80 100 120 140 1600
2
4
6
8
10
12
14
R² = 0.479611244719436
Mean Length vs Mean Hardness (Tom's Creek Ommit -ted)
Mean Hardness (ppm)
Mea
n Le
ngth
(cm
)Length:
What does this mean?
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Discussion/ Conclusion
• Finding more Crayfish at Sinking Creek than Little Stony does support our hypothesis.
• The low numbers of crayfish found in Tom’s Creek contradicts our hypothesis.
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Discussion/ Conclusion
• Calcium important to crayfish growth causality not known
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Discussion/ Conclusion
• This contradiction may be due to varying habitats.
• More Sediments at Tom’s Creek• More Rocks at Sinking Creek• Little Stony had boulders • Sinking Creek had more cobble in the
sampling area
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Results/ Conclusion
• Future Experiments:– Send the same person to each stream near the
same time of day on the same day
– Different capturing strategies, weather patterns, seasons and amount of sunlight may affect the numbers of crayfish caught
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Literature Cited• Cairns, Allegra, Yan Norman. 2009. A Review of the Influence of
Low Amvient Calcium Concentrations on Freshwater Daphniids, Gammarids, and Crayfish. NRC Research Press website at er.nrc.ca.
• Edwards, Brie A., Jackson, Donald A., Somers, Keith M. 2009. Multispecies Crayfish Declines in Lakes: Implications for Species Distributions and Richness. J. N. Am. Benthol. Soc 2009, 28(3): 719-732.
• Hammond, Kent S., Hallows, John W., Townsend, Colin R., Lokman Mark P. 2005. Effects of Temperature and Water Calcium Concentration on Growth, Survival and Moulting of Freshwater crayfish, Paranephrops zealandicus. Aquaculture 251(2006): 271-279.
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Literature Cited• Reynolds, Julian, Souty-Grosset, Catherine. 2012. Manage of Freshwater
Biodiversity Crayfish as Bioindicatiors. Cambridge University Press, New York.• Stelzer, Robert S. and Burton, Thomas M. 2011. Growth and Abundance of
the Crayfish Orconectes propinouus in a Hard Water and a Soft Water Stream. Journal of Freshwater Ecology, 8:4, 329-340.
• U.S. Geological Survey. "Virginia Geologic Map Data." Virginia Geologic Map Data. U.S. Department of the Interior, 2005. Web. 24 Oct. 2012. <http://tin.er.usgs.gov/geology/state/state.php?state=VA>.
• "Northern Virginia Ecology." Northern Virginia Ecology. Fairfax County Public Schools, n.d. Web. 07 Nov. 2012. <http://www.fcps.edu/islandcreekes/ecology.htm>.
• "Water Hardness and Alkalinity." USGS Water-Quality Information:. U.S. Department of the Interior, n.d. Web. 28 Nov. 2012. <http://water.usgs.gov/owq/hardness-alkalinity.html>.
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Questions?