Uploaded by celeste Arreola


A01 - Water clarity & correlation
The file "Clarity" contains Secchi depth (m), Turbidity (NTU) and Light extinction values for 64
lakes in Michigan from Summer 2001-2003.
1) Calculate the correlation co-efficients between the 3 light variables in the “Clarity”
worksheet. Provide both the r and corrected p-values for each of your correlations in
the table below. Are all your correlations significant?
- All correlations are significant.
Light Extinction
Light Extinction
By Variable
2) Submit your R Notebook as a PDF
3) Comment on the relationship between the variables. Make sure you clearly explain how
each these variables measure light penetration in water and why they are negatively or
positively correlated with each other.
- Turbidity measures the intensity of light scattered at 90 degrees as a beam of light
passes through the water. Secchi disks measure water transparency by lowering a
disk into water until it cannot be seen anymore.
4) For what type of studies would information on water clarity be important? What
variables may be reducing water clarity in some of these sites? What organisms would
depend on clear water and why?
- Water clarity is important when conducting studies on things such as seeing if water
is okay for recreational use, reservoir fish habitat management, aquatic plant health,
and noxious algae growth. Variables that reduce water clarity are suspended
sediments, algal growth, runoff, shoreline erosion, organic material decay, and
pesticides. Freshwater animals depend on clear water because they cannot survive
in salt water. Aquatic plants need clear, pollution-free water in order to release
oxygen into water and improve environment for fish. They absorb nutrients from the
water which results in clearer water and less algae.