Project 1

Overview

There were 22 sites that were selected along the Whitewater River. Sites 1 though 12 were upstream and sites 13 through 22 were downstream. Data included stream, fish, and invertebrate variables that were collected at each of the 22 sites.

The data included:

  • Sites 1 through 22

  • 18 stream quality variables (example width or depth)

  • 19 fish population variables (fish species counts)

  • 39 invertebrate population variables (invertebrate taxa counts)

Three questions

  • Question 1: Do upstream and downstream sites differ with respect to the variable measured?

  • Question 2: Does it appear that the stream, fish, or invertebrate variables are most responsible for differentiating between upstream and downstream sites?

  • Question 3: Which stream, fish, invertebrate variables differ the most between upstream and downstream sites, and in what way?

Methods

  • Sort all the stream, fish, and invertebrate variables into their own data frame for easy separation.

  • Combined all the variables into one data frame (this way the site column was removed).

  • Use of metaMDS from the vegan package with the Bray-Curtis distance metric across the three variable types. This creates a 2d ordination of the variables.

  • The Bray-Curtis distance metric was used because it works great with abundance data in ecology.

  • The stress was .09 which falls under “good” stress.

  • The envfit was used on the three variable types. This shows the relationship of the variables between the sites.

Results for Question 1

The r2 vector was bound together with each variable type from the envfit.

The variables with an r2 above .4 were filtered. This will only show the variables that explain at least 40% of the variation between sites. Shows strongest variables.

Fish variables have a stronger relationship with upstream sites.

Stream and invertebrate variables have a stronger relationship with downstream sites.

Results for Question 2

After grouping all the variables types together and finding the mean and max of the r2 for each variable type, the results are:

Fish variables:

r2 mean: .305

r2 max: .763

Stream variables:

r2 mean: .333

r2 max: .784

Invertebrate variables:

r2 mean: .186

r2 max: .635

Since the stream variables have the greatest mean and max it shows that stream variables are most responsible for differentiating between upstream and downstream sites.

Methods for Question 3

  • Get the grouped mean of each variable for upstream and downstream sites.

  • Take the mean of the upstream and subtract it from the downstream mean. This means that higher mean differences have stronger relationships with downstream sites and lower mean differences have a stronger relationship with upstream.

  • Main idea is that either upstream or downstream will be a lot lower than the other in a box plot.

  • Filter out the highest and lowest mean differences for each variable type.

Results for Question 3 (Streams)

Looking at the stream variables the variable that has the strongest relationship with downstream was buffer width with a mean difference of 116. The variable that had the strongest relationship with upstream was x fines with a mean difference of -40.

Results for Question 3 (Fish)

For the fish variables the fish that had the strongest relationship with downstream sites was the Slimy Sculpin with a mean difference of 290. The fish that had the strongest relationship with upstream sites was the Creek Chub with a mean difference of -96.

Results for Question 3 (Invertebrate)

The invertebrate variable that has the strongest relationship with downstream was Baetis with a mean difference of 251. The invertebrate that had the strongest relationship with upstream sites was Gammarus with a mean difference of -75.

Conclusion

  • Fish variables have a stronger relationship to upstream sites.

  • Stream variables have a stronger relationship to downstream sites.

  • Invertebrate variables have a stronger relationship to downstream sites.

  • Stream variables are the most responsible for differentiating between upstream and downstream sites.

Stream variables strongest upstream relationship is buffer width.

Stream variables strongest downstream relationship is x fines.

Fish variables strongest upstream relationship is Slimy Sculpin.

Fish variables strongest downstream relationship is Creek Chub.

Invertebrate variables strongest upstream relationship is Baetis.

Invertebrate variables strongest downstream relationship is Gammarus.