Field Work on the Mill River

17 Aug

It’s Molly Peek (’18) again! I am working on the Mill River Project with Marney Pratt and Mia Ndama (’17). We are using different macroinvertebrate sampling methods to measure the health of the Mill River. A typical day of sampling for me involves both field and lab work. In the field, the first thing we do is deploy a Hester-Dendy sampler, which is a long-term macroinvertebrate sampling method. The Hester-Dendy is a series of small, pressed wood plates attached to a screw. This sampler is then secured to a cinder block. Three cinder blocks with one Hester-Dendy each are placed in a line across the stream and left for 4 weeks. Macroinvertbrates will start to live on the Hester-Dendy, and when we remove the device we will have an entire community of animals to sample.

#1

After I place the Hester-Dendy, I use another sampling method, kick net sampling, to collect a sample of macroinvertebrates by disturbing the substrate, causing them to float into my net. I do this several times in one section of river and then take all of my collected samples back to the lab so I can catalog the results.

In the lab, I identify each individual to its genus, and then preserve it for future reference. I use these identifications to calculate water quality and stream health based on the number and type of invertebrates found in my samples. We find many different types of organisms, but some of the most important are mayfly, stonefly, and caddisfly larva. Anyone who is interested in flyfishing might recognize these bugs because they are important bait, but we are interested in them because they are groups that are sensitive to pollution and are good indicators of stream health.

#2(Caddisfly, or Trichoptera, larva)

The identifications can be tough sometimes, because the animals can be quite small and difficult to distinguish, even under a microscope, but we are currently working on a dichotomous key that will make identification easier in the future. This key will be used in BIO 155 when the class has their unit on macroinvertebrate sampling, and is specially made for the Mill river and for students who do not have experience identifying macroinvertebrates. It has also been pretty fun to make!

-Molly lives in King House and plays on Smith’s field hockey team. She grew up in New Jersey and now lives in the Green Mountains of Vermont.

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