DATA
The following is the data as submitted. I have combined images so that we have more information to use to build the diversity index for each site. In a few cases, especially in Stream B, there were a whole lot of individuals in the same scoop (denoted by the numbers in the square with the individual). Decide how you want to take this into account, and explain it in your answer.
Beautiful Place
Stream B (AKA "Stinky Place")
Whitmer Park Pond
QUESTIONS
1. (6 pts) We calculate a diversity index in the following way. First, we count the number of individuals sampled, and call this I (for "Individuals"). Then, we look for "runs" (which we will call R). A new run begins when the species changes. For example, looking at the first line for Beautiful Place, we see that there were 10 individuals. The first one is a green wormy thing. Then, we see four water striders. These all count as a single run because we saw them in order. Next, we see two earth worms, and then two red worms and then a little who-knows-what. Thus, we have 5 runs (R=5). If we saw a water strider next (which we do, but it's on the next line), this would be a new run, even though we've already seen some, because the species changed.
Now, we can calculate a simple diversity index called the "Sequential Comparison Index" (SCI), using the equation: SCI=R/I. For example, the SCI for the first line of the data at Beautiful place is 5/10=0.5. The second line is harder to interpret, but I think they're all different, so we now have I=15 and R=10, so the SCI of the first two lines is 10/15 = 0.667. You can see how sensitive the data is to how many measurements we use: a single run can have a strong effect on the SCI if there are only a few observations. This is why we want to combine the data, even though groups got very different results. In general, small, random occurances tend to be less important if you have a lot of data.
Now, calculate the complete SCI for each of the three sites. We are really interested only in aquatic macroinvertebrates, so if you see something that you are pretty sure is not an aquatic bug, you can ignore it (e.g. the McDonald's, the house flies, and so on). In your response, mention how you treated the large numbers of individuals recorded in Stream B.
2. (3 pts) An SCI of < 0.3 is considered "low diversity", and an SCI of > 0.7 is considered "high diversity." Rank the three sites according to diversity. Also, rank the sites in terms of number of individuals.
3. (3 pts) Do you think that either of these values are useful for estimating the quality of the water for aquatic life? Why, or why not?
4. (3 pts) Based simply upon your observations at the time of the lab, rank the sites in terms of how "natural" you think they were. Explain your choices. Does this ranking correspond more to SCI or I?
5. (3 pts) What factors may have skewed the data that you collected? Think about both errors that samplers could have made as well as features of the systems that you looked at?
6. (2 pts) What other factors would you want to measure to determine the quality of the water bodies?