Granite Lake Field Trip

Granite Lake Field Trip Limnology Lab 4430 R. Hall/B. Taylor

Our field trip to Granite Lake is designed to show you patterns of chemistry and biology associated with depth in a stratified lake (actually a reservoir). We will examine several parameters in this lake during the field trip and afterwards in the lab. Many of the questions below will be answered by us during the field trips and in the laboratory. This exercise is not designed so that you have to answer a bunch of tough questions based on our data, but rather for you to integrate how different processes control patterns in a stratified lake. Ask us lots of questions! Hopefully the lake will be somewhat stratified; in past years it has barely stratified despite its 17-m depth. Why would this be in mid September in Wyoming?

1. Temperature curve. What should this look like for a lake in midsummer? What is the mixing regime in this lake? 2. Dissolved oxygen. How does DO respond to the stratification? Is there a clinograde or an orthograde curve? Why is this? 3. Alkalinity. Does alkalinity change along this gradient? Why? 4. Ammonium. How does ammonium change? Does it track dissolved oxygen? Why? 5. Chlorophyll. How does chlorophyll concentration change along this gradient? What might structure the algal assemblage? DO, nutrients, light availability, or other physical factors? 6. Does conductivity change with depth? Why?

The above questions would serve as a general outline for the lab report (REPORT DUE October 22!). This report should be no more than 3 pages double- spaced, 12-point font, page limit does not include graphs,. Use one paragraph to introduce the subject, one paragraph to describe what you did, and the rest of the report to describe and interpret the results. Use Excel to make figures for temperature, DO, and conductivity as depth changes (to get the y-axis to be below the X-axis: double click on the Y-axis, select “Scale”, then select “Values in reverse order”).

When writing, cut right to the chase; with only three pages we expect succinct descriptions with a brief discussion of the results. End with a concluding paragraph tying your findings together. We do not expect an abstract or literature cited section on this short report. You should discuss why the patterns we observe are present in this lake at this time of year. Do not just state that the patterns exist because the lake is mixed or not mixed? Discuss and speculate on the phenomenon that may have produced the observed patterns. Use your knowledge from lecture and the textbook.