SEES 2022: Stagnant Shelter

Guest blog: Sharis H.

California is home to 53 mosquito species, including many that serve as vectors for diseases like West Nile, Malaria, and Dengue. In my county of California, Santa Clara, mosquitoes from the genus Culex and Aedes are most common. For mosquitos to keep their population flourishing, female mosquitos lay eggs in stagnant containers of water. These eggs then go through the mosquito lifecycle to reach maturity and reproduce.

The purpose of this experiment is to determine how important stagnant water is to female mosquitos as they choose a location to lay their eggs. My experiment contains habitats with stagnant water and water with a slight flow.

My research takes place at the Los Alamitos Creek, a 7.7-mile-long creek that eventually joins the Guadelupe Creek. I set up a total of 6 traps within a 12 ft by 12 ft area in and around the creek. The water here is not fast flowing and almost stagnant, but still has a slight current.

For setup, I filled 6 clear plastic cups with diced peach as bait, along with wooden beams and rocks. Upon arriving at my location, I filled all 6 cups with water from the river.

3 of the cups were used to be stagnant water habitats. Upon filling them with river water, I placed them along the river bed hoping to attract mosquitoes.

I poked holes in my 3 other cups (allowing for water flow) and buried them within the river so that just a little bit of the cup stuck out of the water.

My cups were left for 6 weeks, with me visiting the location every week. I sampled water from all the cups before taking it home to be analyzed under a microscope.

By the end of the 6 weeks, none of my cups had managed to house any live mosquito larvae or pupa. However, despite it all, I did manage to attract several frogs and snails from the river. I also discovered several bugs and possible mosquitoes, but all were dead.

Week 1 (06/16-6/23)
The water seems relatively clear. None of the cups have been knocked over or fallen over, a good start to the experiment! No sign of larvae in the water.

Week 2 (06/23-6/30)
Algae is making itself known. All 6 of the cups are starting to go through slight algae blooms. One of the cups was knocked over, and a bite was taken out of the peach. I think the culprit was a dog, especially since my experiment location is close to a running trail. Unfortunately, no sign of mosquitoes or larvae.

Week 3 (6/30-7/6)
Life exists in my cups! Unfortunately, it is not mosquitoes. My river cups managed to attract what I think are New Zealand mud snails. These snails are smaller than my pinky nail, with cone-shaped black shells. The algae situation is getting out of hand in my stagnant water cups; however, this should make it a more probable breeding sight due to the food source of algae.

Week 4 (7/6-7/13)
Possible mosquito eggs in sight! I took a water sample from one of my stagnant water cups and placed it under my microscope to see little round clusters. I think these could be mosquito larvae that were disrupted from their grouped orientation due to me sucking up a little bit of water. I also found a dead bug in another stagnant water cup. This could be a possible mosquito, but since the bug was dead and slightly disintegrated, I can’t say for sure this is a mosquito. My river cups have attracted more snails, but still no sign of mosquitoes.

Week 5 (7/13-7/20)
No sign of mosquitoes in any of my cups, making me question if my discoveries in week 4 were truly mosquito eggs as they should be larvae by now. I found more dead bugs in my stagnant water cups, which I believe are mosquitoes.

Week 6 (7/20-7/27)
Out the cups come. After the 6-week-long experiment, they are filthy with algae. All of the stagnant water cups are purely green, whereas those from the river have algae at the bottom followed by some amount of clear water and plenty of snails. I ran a quick pH test to see if there were any differences, and the stagnant water had a pH closer to 8, whereas that of the river was closer to 7. I ran one last set of microscope slides, viewing plenty of algae and this strange beak-like figure from the river water.

Confirmed mosquito count: naught

The ironic part of this experiment is the number of mosquito bites I have gotten checking on these traps. Might I also mention that I am severely allergic to mosquito bites, so I truly have been putting my life on the line in the name of this experiment.

After several weeks of no mosquito larvae, I did some research into the Los Alamitos Creek. Said creek is noted for having extremely high levels of mercury, so high that the creek was nearly filled several years ago. As mercury attacks the central nervous system, the water may have killed the mosquito eggs I noted in week 4. Additionally, mercury may have been the driving factor behind the large number of dead bugs I found in my cup.

Another concern of mine surrounds the New Zealand mud snails I noticed in my river cups. A mosquito could view these as potential threats to the well-being of their eggs and choose another safer location.

All in all, due to my lack of mosquitoes in this experiment, I would like to proceed forward focusing on mercury levels and how that impacts the mosquitoes.

Sharis Hsu​​​​​​​​​​​​​​About the author: Sharis is a student at Valley Christian High School, San Jose, CA. This blog describes a mosquito trapping experiment conducted as part of the NASA STEM Enhancement in the Earth Sciences (SEES) summer high school research internship. Her virtual internship is part of a collaboration between the Institute for Global Environmental Strategies (IGES) and the NASA  Texas Space Grant Consortium (TSGC) to extend the TSGC Summer Enhancement in Earth Science (SEES) internship for US high school ( Sharis shares her experience in this blog post.

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