by Bella Weeks
Jackson County Early College – Sylva, North Carolina
During the Summer Internship with Great Smoky Mountains National Park (GSMNP) and American Conservation Experience (ACE), the North Carolina interns got the opportunity to collect dragonfly larvae from three different locations within the Park. I had the wonderful chance to participate in all three of these collections.
The ultimate goal of the Dragonfly Mercury Project is to gather statistics about the levels of mercury in the streams, rivers and lakes that are in our National Parks. National Parks all over the country are participating in this project, and Great Smoky Mountains National Park is one of them. All of the samples we collect are sent to Dr. Sarah Nelson at the University of Maine.
One reason why dragonfly larvae in particular were chosen as a model organism for this study is because they live in their larval stage for up to five years, which is a long time for an insect. This means the dragonfly larvae can be exposed to the mercury in the water for a longer time than other insects.
Another reason dragonfly larvae were chosen is because they are predators and eat many other insects. The mercury that is in the insects that they eat builds up inside of the dragonfly larvae.
By collecting the dragonfly larvae and sending the larvae to scientists for laboratory analyses, we can start to get a better understanding of how mercury impacts our streams and rivers and the life within.
The levels of mercury in dragonfly larvae is also important information to know because a lot of fish eat dragonfly larvae. The fish eat the larvae, and the mercury in the dragonfly larvae will now build up in the fish. Then people eat the fish, and the mercury builds up inside of us.
The mercury concentrations become higher as you go up the food chain, and this process is called biomagnification.
Mercury present in the water can potentially accumulate in the dragonfly larvae, and those concentrations will be higher in the fish, and even higher in humans and other animals that eat the fish.
Mercury is dangerous because it is a neurotoxin. This means that it can cause damage, even severe damage, to our nervous system. So, you can see why it is important for us to be aware of the levels of mercury in our streams, and why dragonfly larvae are perfect indicators for not only mercury but the overall health of the streams, rivers and lakes.
Before we could begin collecting the dragonfly larvae, we had a few things to learn.
Learning about dragonflies
First, we had to learn about the different types of dragonflies.
There are five families of dragonfly that have been documented within the Smokies (note that these are simply the families not the individual species.) The five families are the Aeshnidae (Darner dragonflies), Cordulegastridae (Spiketail dragonflies), Gomphidae (Clubtail dragonflies), Libellulidae (Skimmer dragonflies), and Petaluridae (Petaltail dragonflies).
Our field and internship lead, Ranger Carlin Fenn, told us that even though there are five families that have been documented in the Smokies, there are three dragonfly families that are the most common to the types of habitats we were sampling. These are the Aeshnidae, Cordulegastridae, and Gomphidae families. We also learned how to identify the different families.
We used photos and charts for the identification part of the process, plus we had Ranger Carlin’s wonderful help for the identification.
Collecting dragonfly larvae
Next we had to learn about the process of collecting the larvae. Along with data sheets and labels, the equipment we used included nets, plastic spoons, gloves, plastic bags, and a cooler and ice.
Before you can label the larvae, you have to actually collect them. To find the larvae, you have to get into the stream or river you are sampling. You take your net and locate a place, generally right along the bank where there is either a lot of silt or sand or (more ideally) a place where there is a lot of leaf litter. Leaf litter locations were where we found the most larvae during our collecting.
You stick the net into the mud or silt and sort of swish it around, then you pull it up and look through it for the dragonfly larvae. You do not want to contaminate the larvae, as mercury is literally everywhere – in the air, on our skin, and in our hair. If you touch the larvae, you can contaminate it. So, to sort through the mud and silt, we used clean plastic spoons.
After finding a larvae — which I feel is a very exciting moment – we carried it to a collection container. We had to find fifteen larvae at each site for the analysis – and we succeeded at each of the three sites.
Processing larvae — a team effort
After collecting the required number of larvae, it is time to sort and label the larvae and put them on ice. This process goes by surprisingly fast, when the group works like an assembly line, with everyone doing a different job.
One team member is “clean hands,” meaning that person puts the larvae into the bags. Clean hands wears gloves and cannot touch anything except for the larvae. “Dirty hands” opens the bags for the person who is clean hands and closes the bags, before handing the bags off to the measurer. The measurer determines the lengths of the larvae, and then passes them off to the identifier. The team members all pass on their information to the recorder, who writes the information on the slip of paper that goes into the bag with the larvae.
The thing that I think is the most challenging about collecting dragonfly larvae is the part where you are trying to find them. If you do not have much patience, it becomes a bit trying at times, especially when you have been looking for hours and still have not found a larvae. It is even more frustrating when everyone else is finding larvae, but you are not. When you finally find a larvae, it is exciting and rewarding, as it’s good to know that you are aiding scientific research.
I loved doing the dragonfly larvae collection. It is rewarding to know that you are collecting data that scientists will use to further understand the effects of mercury on our streams and rivers. Plus, I always love to learn new things — especially when it comes to learning anything that has to do with biology (particularly anything about wildlife).
This is the second blog post by high school students participating in the Great Smoky Mountains National Park Summer Internship Program. The first post introduced the program. This summer, 24 students are participating, representing high schools in North Carolina and Tennessee that are near the Great Smoky Mountains National Park.
The program is funded by both the Youth Partnership Program and Friends of the Smokies. FOTS has supported the program for 15 years, initially providing the salaries for the interns and now funding the program staff salaries.
The program is designed to give the interns a little taste of a variety of activities that rangers are involved with – from fisheries science to botany to forest and stream ecology. The interns gain an understanding of how the park is managed and are introduced to possible career opportunities.
To support Parks As Classrooms and the high school intern program, click here.