Students Share Their Results and Conclusions
For the past three years we’ve been fortunate to have the seventh graders from Catlin Gabel School focus their research attention on the health of our Timber Forest. Here is a report on the questions their asked, the data they collected, and the conclusions that they’ve drawn. We thank them, their teachers and the parent helpers for the important work.
When Macroinvertebrates Tell Their Story
By: Thea Traw
Catlin Gabel 7th Grade Class
Weather: Cloudy and rainy, with a 50% chance of macroinvertebrates
On March 1st 2016, my science class from Catlin Gabel School returned to Louisgnont Creek, deep within the shadowy forest of Hyla Woods in the Nehalem Watershed. We did not know what to expect: what had changed and what had stayed the same since we last visited a month ago? As we walked through the steady downpour of rain, however, we were not thinking of ways to attempt to write a blog. Instead, we were studying, observing, and questioning our surrounding and the mysteries within Louisignont Creek. I’ll start my eventful and interesting story at the beginning, though, so don’t worry.
Hyla Woods is an experimental forest, which strives to be self-sufficient, while treating the wildlife and trees with respect and the proper care. Following an ancient Catlin Gabel tradition (we’re the third year), we journeyed out to Hyla Woods to research and answer one question, which always remained in the forefront of our minds as we worked: “Is Hyla Woods a healthy ecosystem?” We ran many tests to find the answer to this question, some plagued with more troubles than others (as you will see…). We took it upon ourselves to investigate this question because, as budding scientists, we need to learn how to conduct tests to find out how successfully an ecosystem is maintained, in our case, or just if an ecosystem is functioning properly in general. It is very important to understand if an ecosystem is healthy because Earth could be described as a GIANT ecosystem, so if we didn’t know how to assess if it is healthy, how can we save our home from threats like climate change? Also, answering this question helps us understand the mysteries and complex connections between all living things, so we can learn how each organism is important to make up healthy ecosystems. Our work also can help the owners of Hyla Woods improve the management of their trees and creek because the results and analysis we conclude from our tests can give them important feedback from the animals and the stream: we can speak for the trees and those without voices, following in the Lorax’s momentous footprints.
We conducted many tests during our time at Hyla Woods. The variables that we were testing and recording were the following: water temperature; air temperature; pH, which is the acidity or basicity of the water; turbidity, which is the measurement of how cloudy or opaque the water is; and dissolved oxygen, which is the level of oxygen dissolved in the water. Each of the twelve research teams from our class, did these five tests two times at their respective field sites–once during our first excursion, and the second time during this more recent trip.
We also were carrying out a more complex and involved test: the leaf pack analysis. During our first trip to Hyla, we had carefully selected a place to put our leaf pack then left hoping that it would still be submerged when we returned, brimming with all sorts of aquatic macro-invertebrates. (If you have some terrestrial invertebrates in your leaf pack, something has gone horribly wrong.) On both trips, my group successfully carried out each of the first five tests, but our leaf pack had a slightly tragic tale, but I’ll talk more about that later. These six tests are important in determining the health of an ecosystem, so I’ll take a moment and explain the point and worth of each test.
Since macroinvertebrates are cold-blooded, the temperature of the water affects them more than it would you or me. Some animals, like salmonids, are especially susceptible to higher water temperatures, but if the population of the salmonids decreases, the whole ecosystem could get thrown off. The range most suitable for most aquatic life is 5°C to 15°C. Our first measurement was 8.5°C, and our recent recording was 8°C, both of which fall into a suitable range for aquatic life. The average temperature, based on the first trip, from my whole class was 7.4°C, so Louisignont Creek is at a healthy temperature.
Air temperature has less of an effect on aquatic life than the other variables do, but it is still important. Our class average temperature from the first time was 7°C, and the following time was 8.7°C.
The next test we did was the pH of the creek. Our results (6 on our first day of research and 6.5 on the second) were very close to the class’s average of 6.3 and 6.6 respectively. The suitable range for most aquatic life is 6.5-8.3, so some of our data does not fall into the category of being most suitable. pH affects the health of ecosystems in a large way. Some invertebrates can’t survive in water that is out of a certain range. These more sensitive animals are called “bioindicators,” and their presence or absence goes a long way in finding out if an ecosystem is healthy. In levels of pH that are too high or too low, bioindicators often disappear, which hurts the health of the ecosystem.
Discovering the turbidity of the water was the next step that we took. Erosion is a useful indicator for the health of an ecosystem because the amount of turbidity indicates the amount of riverbank erosion or sediment in the water. Too much sediment can decrease the levels of dissolved oxygen, which leads to a digression in the health of the ecosystem. Our measurement of turbidity using the turbidity tube method was 120+ cm both times, which is a healthy turbidity level. The class average was 87 cm the first time, and 107 cm the second time. That leads me to think that a heavy rainfall occurred before the first trip, but not the second, or some of the test were not done correctly, because the difference between the two results is pretty large. For turbidity, it is better to be clear, so our results as a group are especially optimal. Our class average is less so, but it still is healthy.
The second to last test we conducted was our dissolved oxygen test. Dissolved oxygen is one of the most important factors in measuring the health of the ecosystem. Aquatic animals need a certain amount of oxygen in the water, because they need oxygen to function, just like we do. My group’s recording of dissolved oxygen was 10 ppm both times. This indicates that our site is healthy because 8-12 ppm is a healthy range for most aquatic life, and our data falls right in the middle of that range. Our class average was 10.1 ppm the first time, and 10.8 ppm the second time. Our class’s data also indicates that the creek is healthy because both measurements fall in the optimal range.
The final and most complex variable that we tested was the macroinvertebrate survey using our leaf pack. On our first excursion to Hyla Woods, we selected a place to put our leaf pack. A leaf pack is made up of three types of leaves: big leaf maple, vine maple, and alder. Leaf packs are designed to become a home for macroinvertebrates, therefore enabling us to collect and research the macroinvertebrates without harming their natural home. Measuring macroinvertebrates is probably the most important test a scientist can do while researching the health of a stream ecosystem. Macroinvertebrates are something called bioindicators. As I mentioned before, bioindicators, as their name suggests, indicate the health of an ecosystem. Their presence, or absence, can tell a lot about the state the ecosystem is in. The more sensitive macroinvertebrates there are, the healthier the ecosystem. But, if your leaf pack overflowed with only tolerant insects or has none at all, the ecosystem is in a sadder condition. The leaf packs are not especially accurate when they are placed in a less-than-satisfactory place, which ours sadly was.
We had left our leaf pack three weeks ago with high hopes, but when we came back, our hopes were crushed by a tiny stone fly and aquatic worm. There were only two macroinvertebrates in our whole leaf pack. However, I consider those two invertebrates to be something of an achievement, taking into account that our leaf pack was practically floating on the top of the creek when we arrived instead of anchored near the gravel where we had intended. Our leaf pack was an unsuccessful test, and it, in and of itself, will not help Pam and Peter Hayes, the owners of Hyla Woods, with finding out if Hyla Woods is healthy, but it still was a good opportunity to practice making a leaf pack. I bet that if we all made another leaf pack, it would turn out much better. With this said, we’re happy that a majority of the other research teams were more successful, and that they collected more useful macroinvertebrate data.
Anyway, our class’s results were somewhat varied, as a few other groups had similar troubles to ours. Still, most groups were able to collect data from their leaf packs. Our collective EPT score was 71.8. An EPT score is the percentage of macroinvertebrates that are either Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies). These species are very important to the ecosystem’s health, and they are all sensitive macroinvertebrates, though the caddisflies are more tolerant than the other two. The higher the score, the better the health is. Biotic Index is the other way to view the data we collected from our leaf packs. It measures the average tolerance value of an invertebrate in this ecosystem. In this case, the higher the number, the healthier the ecosystem is. Our class’s average Biotic Index score was 4.3, which falls into a reasonably healthy ecosystem. It would have been better if the score had been below 3.75, because that would mean the ecosystem is in excellent shape, but 4.5 falls between 3.76 and 5, which is indicated as good on the Biotic Index scale.
When taken all together, my belief is that Hyla Woods is a reasonably healthy ecosystem. None of the tests, air and water temperature, turbidity, pH, dissolved oxygen, Biotic Index, or EPT score were significantly unhealthy, and a few fell directly into the healthiest range. The temperature, both air and water, dissolved oxygen, turbidity, and pH all were healthy, which indicates a healthy ecosystem, even if a few of the tests were less optimal than one might wish. The two tests from the leaf pack, EPT and Biotic Index, were both reasonably good, and while the Biotic Index score fell only into the “good” range, that still indicates a healthy ecosystem. Our EPT score was more satisfactory, and at a 70.8, that test indicates a quite healthy ecosystem. To conclude, Hyla Woods’ health could improve as an ecosystem, but Pam and Peter Hayes have done a tremendous job working on the ecosystem’s health, and they should be proud of how well the ecosystem is doing. No matter what, the ecosystem of Hyla Woods will never act exactly how it would without any human interference, so when you take that into account, Hyla Woods is a healthy ecosystem.
After going to Hyla Woods, I am left with many good memories and a dripping wet backpack. One highlight of my experience was conducting the tests in the field. I had a lot of fun with my friends, exploring the stream’s ecosystem and researching the different variables of an ecosystem. However, I am also left with a burning question in the pocket of my soaking rain jacket. How far would a stream have to be removed from all of human interference to be completely healthy and untouched? And is there even a stream like that somewhere in the world? I also wonder about all the forests and streams that are not treated with such care, and what happens to the streams after the loggers and industries come and remove a part of their ecosystem (the forest), or pollute their waters? I am also left with a bigger picture question. Why do we, as humanity, ruin our resources that allow us to live, and squander away all of nature, which was our first home, way before we built houses or cities? To wrap up,, I would like to leave an overly cliché message for all of humankind: Do unto nature as you would have nature do unto you. I would also like to give you some food for thought. Sometimes we forget that we are animals, too, not unlike a fish or an eagle, but we think we are above the beings on Earth. But remember this, we are animals, and animals are nature, so that must mean that we are nature. So if we destroy nature, by polluting and clear cutting and climate change, we are, in effect, destroying ourselves.