Aquatic Macroinvertebrate Survey with Pierre Van Cortlandt Middle School 5th Graders

Earlier in February I visited the Piere van Cortlandt Middle School in Croton-On-Hudson. We did a survey of aquatic macroinvertebrates from pond water samples taken from a pond at the Landis Arboretum in Esperance, NY. These samples were taken from under the ice covering the pond which was about a foot thick.

Zabbia (first class first day), Ernau (second class first day), Dillon (third class first day), Barkan (first class second day), Herbert (second class second day), Liss (third class second day)
Waterboatmen - Dillon 1, Barkan 2, Herbert 3, Liss 1
Nematode - Dillon 3
Crawling Water Beetle - Ernau 3, Dillon 5, Barkan 3, Herbert 5, Liss 6
Dragonfly - Zabbia 34, Ernau 40, Dillon 39, Barkan 42, Herbert 31, Liss 35
Caddisfly - Zabbia 20, Ernau 27, Dillon 21, Barkan 18, Herbert 17, Liss 15
Backswimmer - Zabbia 4, Ernau 8, Dillon 8, Barkan 2, Herbert 8, Liss 6
Leech - Zabbia 5, Ernau 2, Dillon 3, Barkan 2, Herbert 2, Liss 2
Mayfly - Zabbia 16, Ernau 1, Dillon 1, Barkan 5
Bloodworm Midge - Zabbia 7, Ernau 11, Dillon 3, Barkan 5, Herbert 4
Freshwater Shrimp - Ernau 2, Dillon 2, Barkan 2
Giant Waterbug - Zabbia 4, Dillon 1, Barkan 1, Herbert 1
Cranefly - Dillon 1
Daphnia - Zabbia 1, Ernau 2, Dillon 1
Damselfly - Zabbia 10, Ernau 11, Dillon 4, Barkan 8, Herbert 7, Liss 3
Snail - Zabbia 2, Dillon 3, Barkan 3, Herbert 2, Liss 6
Water Pennies* - Ernau 1, Barkan 6,
Adalphia** - Barkan 1
Riffle Beetles*** - Barkan 2
Stonefly**** - Liss 1

* Water Pennies are the immature stage of the riffle beetles and occur only in streams. Since our samples came from a pond these wouldn’t be found there. I am not sure what creature may have been mistaken for a water penny.
** I think there was some confusion in the writing of the name “daphnia” which resulted in this entry.
*** Riffle beetles are found only in streams. The beetles identified as riffle beetles were most likely crawling water beetles.
**** Stoneflies occur mostly in streams or large lakes. They do not occur in the pond where our samples were taken. I suspect this specimen was really a damselfly.

In our first study of aquatic macroinvertebrates, the samples taken from the duck pond, we were doing a qualitative study. In a qualitative study we are looking at what kind of life occurs in that habitat. With this study we were looking for not only what is there but in what amounts. This would a quantitative study. Depending on what information a scientist is looking for they might do either studies.

I was interested in knowing how well 5th grade scientist might be at finding and identifying aquatic macroinvertebrates, a quantitative study. I wanted to know not only whether the 5th graders would find dragonflies, for example, but how many they would find. If the numbers of dragonflies found by the six classes varied widely I would then presume that there was wide range of ability at finding these creatures. In fact, students were quite capable at finding the macroinvertebrates, especially the larger size ones like damselflies, dragonflies and caddisflies.

As we did our investigation I began to wonder about the midge fly larvae, also called bloodworms. Several students observed bloodworms being eaten by dragonfly nymphs in the uncamouflage containers. It seems from the data that indeed they were being eaten since we found more of them on the first day (11 being the most and an average of 7 being found) as compared to the second day, where the most found was 5 with an average of 3. The bloodworm midges with their bright red color need a lot of hiding places. The investigation tubs must not have provided enough hiding places and they were being eaten.

As with any scientific work the more you do something the better you get at it. As beginning aquatic ecologist I am sure that there were some misidentifications made. For example I know that there was only one waterboatmen in all of the tubs. The waterboatmen look a lot like backswimmers. When I look at the data for waterboatmen I presume that the wide range in the number reported is a result of this misidentification. I’m sure that the extra waterboatmen were in fact backswimmers.

Mistakes in identification can be suspected if we analyze the data. Look at the giant waterbug data. Three classes found one giant waterbug, two found none and one found four. Again, with my experience, I know for sure that there was only one giant waterbug in our samples. When I analyze our findings I see that most teams, if they found a giant waterbug they found only one. I would suspect then that the class that found four likely misidentified the species and mistook some other organism for giant waterbugs.

When we look at most of the other creatures that were counted we see that we get very consistent numbers. In the cases where there was definitely some confusion in identification (the riffle beetles and stoneflies), the species that they likely were fit nicely into the numbers found by other students (the riffle beetles being crawling water beetles and the stonefly being a damselfly). This tells me that students were doing a good job in identifying most of the macroinvertebrates. There is one other species though, where I think there were some mistaken identities. Can you figure out which species this is?

From this data I conclude that 5th grade scientist with guidance, practice and experience a very capable of doing an inventory of aquatic macroinvertebrates. Even though some misidentification might occur the students did a great job in finding and identifying most of the aquatic organisms that we had in the sample tubs.

For more aquatic ecology investigations, including photos of some of the aquatic macroinvertebrates that might be seen in a freshwater pond see blog entry, Pond Ecology at Central Valley and Circleville, dated November 19, 2008.

Jefferson Elementary School Owl Pellet Dissection

Here are the results for the owl pellet dissection that I did with the 5th grade ornithologists at the Jefferson Elementary School in Rotterdam, NY.

Gorski’s class – 12 pellets dissected, 28 mice, 1 shrew, 0 moles and 0 birds found
Guzewich’s class – 11 pellets dissected, 34 mice, 0 shrews, 0 moles and 0 birds found
Fiske’s class – 10 pellets dissected, 28 mice, 0 shrews, 0 moles and 1 bird found
Zanta’s class – 11 pellets dissected, 24 mice, 3 shrews, 0 moles and 0 birds found
Walker’s class – 10 pellets dissected, 24 mice, 2 shrews, 0 moles and 0 birds found

In our discussion we concluded that we could get a better understanding of what the owls eat if we took apart more pellets. Unfortunately time and money constraints didn’t allow us to take apart more pellets with each class. By looking at the data from all the classes though we are “taking apart more owl pellets”. What does this data tell us about owl food preference?

You can take this further if you can figure out how many pellets an owl might make in a night. This is what most likely happens. Starting at dusk an owl hunts and eats until it’s full. Then the owl finds a roosting place where it will rest, spit out a pellet and digest its food. This whole process might take a couple of hours. Then the owl will go off and hunt some more doing it all over again. Can you figure out how many pellets an owl might produce in a night? If you can, you can also figure out how many mice an owl might eat in a year.

Look through the blog for more owl pellet dissection entries. That would provide even more data to analyze and get a better understanding of owl prey preference.