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Worms in Prospect Park, Brooklyn

Linda Intro

 

People often plant flowers and vegetables in the soil. By doing so, they improve the beauty of their surroundings, which often results in commercial benefits. The nutrients found in the soil may be credited to inconspicuous creatures beneath the surface—worms. Many people are disgusted by these curious-looking animals; however, they have always been a source of fascination for me and are creatures I want to research.

Worms are known to be great fish bait, which is one reason I was first drawn to these creatures. When I was 9 years old, my brother-in-law invited me to go fishing in Prospect Park. The park is located just across the street from where I live. I was baffled when I saw him crouch down and pick up some branches. I was told to rummage through some of the moist areas in order to locate worms for our bait. When I excavated the moist areas, I assumed that worms like to hide beneath the topsoil. It seemed to me that the worms were playing a game of hide-and-seek, and that they could somehow detect my movements.

As we continued our search for worms, I discovered that in parts of Prospect Park we were unable to locate any worms, while in other areas they were abundant. As I reflected on this, I wondered what environmental factors might have contributed to the varying worm populations. Why did specific areas of Prospect Park have more worms than other areas? Was the temperature too cold in some areas, or too warm in others? Were there factors affecting the soil (pH level too high/low, insufficient food, etc.)? Were certain regions occupied by predators? These are the questions I set out to answer as I prepared for my field expeditions.

Worms from Prospect Park

Some of the worms Linda collected in Prospect Park.


During my background research, I discovered that there are three major groups of worms: roundworms, flatworms, and segmented worms (www.amnh.org). Earthworms, the worms I am interested in, are segmented worms and belong to the phylum Annelida. They are the most complex of all worms, with five hearts (which are used to circulate blood throughout the organism) and a body that may be divided into 100 or more segments (www.nysite.com). Earthworms also have a unique way of breathing; they perform respiration through their skin (www.irishearthworm.com).

In the past, many people considered earthworms to be pests that invaded their gardens. However, these little organisms are now known as Mother Nature's little helpers and have a reputation as some of the best fertilizers. The leaf litter they digest leaves behind a rich fertilizer known as worm cast. Furthermore, as an earthworm burrows through the soil, it promotes the movement of air, water, and minerals, thus aiding in the breakdown of organic materials (www.irishearthworm.com).

A recent study by the United States Department of Agriculture (Nancarrow and Taylor, 1998, p. 2) tested the effects that worms would have on poorly fertilized soil. In this experiment, the researchers set up two containers. The first container, the control group, contained dead worms and grass seeds. The second container, the experimental group, contained live worms and grass seeds. The results clearly demonstrated the positive effects that worms have on poorly fertilized soil. The grass plants in Container 2 (with live worms) grew four times faster than the seeds in Container 1 (with dead worms).

drawing of worms

Expedition 1: July 20, 2002
The sun was shining intensely as I passed by kids running around chasing each other with water guns and balloons. The temperature was 30°C. A cool breeze blew, while ducks rested near trees to get shade. Other ducks floated above the pond, pecking for algae. I walked toward my observation area wondering what I would discover during this expedition. 

From my background research, I had learned that worms need to live in soil that provides moisture, shade, food, and the proper temperature (Nancarrow and Taylor Hogan, 1998, p. 15). The factor I most wanted to investigate was moisture, as it enables worms to inhale oxygen. The first collection site I chose, next to Prospect Park Lake, was near people who were barbecuing. As I started digging, I found many more species than I had expected to find. The soil was filled with a diversity of creatures, and it didn't smell that great, either! The hole I dug was packed with maggots, caterpillars, baby spiders, ants, termites, beetles, and centipedes. At Area 1 (not pictured), I collected only two worms. I placed the worms in a container filled with grass and moist soil.

After I finished my search in Area 1, I walked approximately 25 meters south to Area 2. The second area I selected had a few people fishing at the lake. At first I thought this area would be packed with plenty of worms. I stayed there for nearly half an hour, pulling grass out and digging and wondering where all the worms had gone. When I finally stopped digging, I was a little disappointed because I had not found any worms. To my dismay, an earthworm ambled by just as I was about to move on to Area 3. I picked up the worm and walked to the next location in the park.

Area 2 before it was flooded

Area 2 before it was flooded


My last site (Area 3) was located west of Area 2 in the quiet zone in Prospect Park near many water plants. As I started to dig, I immediately collected five worms. So I continued to dig deeper. The more I dug, the more earthworms appeared. The hole I excavated was about 30 centimeters deep. I collected a total of 23 worms from this site.

Area 3 as it appeared in July

Area 3 as it appeared in July


After I completed my first expedition, I went home to develop a worm population graph and to record data in my field journal. The longest worm that I collected was 14.5 centimeters (measured when the worm had extended to its fullest), and the shortest was 3.1 centimeters. After compiling measurements, I jotted down some notes and questions in my journal. I wondered why Areas 1 and 2 had such a low population of earthworms compared to Area 3. Were the arthropods I found in Area 1 predators or enemies of the earthworm? What were the factors that may have contributed to the tiny earthworm population at Area 2? Were there more worms in Area 3 because it was undisturbed and had fewer insects? These were some of the questions I set out to answer on my next two expeditions.

 

Expedition 2: August 21, 2002
After my first expedition, I decided to conduct follow-up research on the predators of the earthworm. I found several Web sites that provided information. It turned out that all the insects I had seen in Area 1 were on the earthworm's enemies list. I discovered that if an area is filled with many of the earthworm's enemies, the earthworm will move to a safer area. This information helped me answer my question as to why there were so few earthworms (only two) in Area 1.

According to The Worm Book (Nancarrow and Taylor, 1998, p. 3), soil odors may cause a worm to be unhealthy. Also, a worm needs to inhabit soils with a normal pH level (usually around 6 to 6.5). Soil that has a pH level of 7 (neutral) is the optimum level for a healthy worm population. So I decided to examine the pH levels of soil as a factor affecting earthworm populations on my second expedition.When I arrived at Prospect Park for my second expedition, I planned to record the pH levels of the soil in Areas 1, 2, and 3. The temperature was 28°C and the time was 4:44 pm. I noticed that the leaves in the park appeared drier than during my last expedition in July. As usual, the park was filled with people barbecuing chicken (which made me a little hungry).

 

The Earthworm Enemies List 

Ants Mites Snakes
Birds Moles Sowbugs
Centipedes Nematodes Spiders
Earwigs Rats and Mice Springtails
Fly larvae Slugs Termites
Millipedes Snails Toads
 

Spiders are among the earthworm's enemies.

Spiders are among the earthworm's enemies.


I headed toward Area 1, ready to do my experiment. I first filled a test tube to line 4 with the pH indicator solution. Next, I scooped up 0.5 grams of soil in a special spoon and added the soil sample to the test tube with the pH indicator solution. I closed the cap and shook the test tube gently for one minute. My next step was to allow the tube to stand for 10 minutes to settle the soil. Finally, I matched the results with a pH color chart. I recorded the pH level of Area 1 in my field journal; it was between 6.5 and 7.

As soon as I finished my first test, I headed to Area 2. When I arrived at what I thought was Area 2, I was quite bewildered. I wondered if I had walked to the wrong site because there were no bricks around - I had sat on some bricks during my first expedition. I surveyed the area again, trying to determine if this was where I had been on my first expedition. I finally realized that Prospect Park Lake had expanded since my last expedition, and Area 2 had been flooded. Although I was quite disappointed, I wondered if the changing water level of the lake was one reason I had only found one earthworm on my previous expedition. I snapped a few pictures of Area 2 and left.

When I arrived at Area 3, I followed the same procedure for testing the pH of a soil sample as I had at Area 1. Surprisingly, the pH level was 6, a little bit less than what is considered an optimum level for a healthy worm population. Perhaps a slightly acidic pH level is a good tradeoff compared to being in an area where there is a host of predators, as there was in Area 1.

 

Expedition 3: November 3, 2003
For my final expedition, I planned to observe earthworms during cold weather conditions. When I entered Prospect Park, I recorded the temperature. It was only 6°C. I wondered whether or not worms migrate to avoid winter, similar to the way birds migrate south, or do all of them just die? The wind blew, and the leaves twirled in circular motions. I coughed as dirt flew in my mouth. My eyes started to water as I looked at the landscape of the park. The park was desolate, unlike on my last two visits when there were people barbecuing and lots of children playing games.

 

Temperature and Soil pH Levels 

Area Temperature Soil pH Level
1 28°C 6.5-7
2 28°C Unknown
3 28°C 6
 

When I reached Area 1, I observed the condition of the soil. Because of seasonal changes, the plants had all dried out and the leaves had fallen. The soil had hardened and appeared very dry. It was very difficult to dig in this area. I did not find any earthworms in Area 1 on this expedition.

As I moved on to Area 2, I shivered even though I was wearing several layers of clothes, and I walked as briskly as possible. Unfortunately, the area was still completely flooded. I decided to take measurements of the water level, and recorded the results in my field journal. The water in Area 2 was approximately 20 centimeters deep.

I moved on to Area 3. As in Area 1, the soil in Area 3 was hard and appeared very dry. I started digging and looked to see if there were any earthworms. The first earthworm I spotted was approximately 15 centimeters below the ground. The second earthworm I found was located about 23 centimeters down in the soil. I found two more earthworms at approximately 28 and 34 centimeters below the ground. I continued digging a hole that was about 50 centimeters deep, but found no additional earthworms.

I then conducted follow-up research to find out why I had found so few earthworms on this expedition compared to my first expedition. I found out that earthworms, like birds and butterflies, also migrate during the winter when the temperature drops. Rather than migrating south, most worms take a voyage deeper down into the soil. Their travels sometimes take them as far as two meters down. Down below the ground, where they go to avoid the chill, they sleep until the weather changes. This form of sleeping is called "estivation," and it is comparable to hibernation among bears (www.learner.org).

 

Conclusion
After completing my research and field expeditions on earthworms, I have gained a greater appreciation of these fascinating invertebrates. Like humans, earthworms have their own way of life. They respond to their environment and make adjustments based on external stimuli (predators, temperature, pH level, etc.). They also have a tremendous impact on their surroundings. Earthworms are credited with improving the quality of soil and have even been studied by the United States Department of Agriculture. Who knows what important discoveries will be made about these complex little creatures as further research is done on them?

Completing these field expeditions has given me greater insight into how scientists observe and study the world around them. During my expeditions, I got a glimpse of an underground world located just across the street from where I live. I discovered that Prospect Park supports millions of creatures that live right under our feet. Although it was sometimes challenging to gather information about this underground world, and I did make a few mistakes along the way, I learned about both the joys and frustrations of researching an inconspicuous yet captivating animal — the earthworm.

 

References

"Amazing Worm Facts." Retrieved from the World Wide Web on May 31, 2002: http://www.irisheartworm.com/primschool/psh1.html.

"The City Naturalist - Earthworms." Retrieved from the World Wide Web on December 21, 2002: http://www.nysite.com/nature/fauna/earthworm.html.

"Earthworm Enemies." Retrieved from the World Wide Web on August 6, 2002: http://ohioline.osu.edu/hyg-fact/2000/2134.html.

"Map of Prospect Park." My illustration was adapted from a map on this World Wide Web site, retrieved on December 24, 2002: http://prospectpark.org/general/parkmap.pdf.

Nancarrow, Loren and Janet Hogan Taylor. The Worm Book: The Complete Guide to Worms in Your Garden. Berkeley, California: Ten Speed Press, 1998.

"Segmented Worms." Retrieved from the World Wide Web on December 24, 2002: http://www.amnh.org/exhibitions/hall_tour/spectrum/27.html.

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