For our stream ecology lab in Foundations, we would have gone out to the Monocacy Creek, put on hip waders, and used nets (seines) to capture macroinvertebrates that live in the water, on the rocks, and in the detritus (leaf litter on the bottom of the stream). The number and type of each species that we catch can tell us something about the health of the stream (and how polluted it may be) because some species are more tolerant of the pollution while others are very sensitive to it. This is one of the most fun outdoor labs we do – so we’re really sad that we did not get an opportunity to do this activity in-person with you this semester!

We still want you to understand why biologists and environmental scientists study the macroinvertebrates living in streams. So this activity is a simulation used to estimate diversity of macroinvertebrates living in a stream.

The results of this lab would have been written up as a lab report. We’ve decided to forego the report and instead we’re asking you to submit your work as described in (3) and (4) below.

Please read the instructions here carefully.

1. Open the simulation (Links to an external site.). Read through the detailed instruction manual (Links to an external site.) for how it works (i.e., how you change the settings). Try it out a few times for practice. Here are some tips to familiarize you with the layout:
   • Green boxes: you can change these settings. Please leave sampling-time set to 500. You only need to change the pollution level.
   • Blue boxes: these are the buttons that start, stop, and reset each trial
   • Yellow boxes: These show the results from each trial
   • You can increase the speed of the sampling (using the slider at the top) to make your trials finish faster.
2. You will test three different scenarios based on the pollution levels: None, Moderate, Severe. You will compare the diversity of organisms found in these streams. Please set sampling-time to 500 for all trials. You can increase the speed (it will not affect your results in any way). At the end of each trial, record the number of each type of macroinvertebrate (e.g., caddisfly, mayfly, stonefly). I would suggest using the screen capture feature (command + shift + 4) so that you can compare all the results at the end.
3. Analyze your results.
   • For the trial pollution=none, calculate a biotic index using this online tool (Links to an external site.). Here are some special notes about the names of taxa:
     • Treat caddisflies as “non-netting-spinning caddisflies”
     • Treat gill snails as “Right-handed snails “
     • Treat worms as “Aquatic Worms (Oligochaeta)”
     • Lung snails are called “Left-handed / lunged snails”
   • Repeat the biotic index calculation for pollution=moderate and pollution=severe.
   • Write 1-2 paragraphs (no more than one page) to explain your results. You don’t need to report all the raw data from the simulation. Instead, just summarize your findings for us and explain how and why the Pollution Tolerance Index (PTI) and the EPT index differed between the three streams with various levels of pollution.
   • Submit your written response here on Canvas under this assignment.
4. The best part! Examine your data again more carefully. Think about: how did the pollution levels affect each species? Which species showed an increase in relative abundance? Which species decreased in relative abundance?