User:Carly Laroche/Notebook/Biology 210 at AU

2/3/16 Protists and Algae From Hay Infusion

Purpose: The goal of this lab was to observe protists and algae in a hay infusion and identify their species by learning how to use a dichotomous key.

Materials and Methods

The week prior to this lab, hay infusions were prepared from samples taken at transect 3 on American University’s campus. 12 grams of soil and vegetation, 500 mLs of deerpark water and 0.1 gram of dried milk were mixed in a glass jar and allowed to sit for a week. Observations of the hay infusion were made. Then, samples were taken from two niches– the top and bottom of the jar– and placed on wet mounts. Organisms may differ in each niche because some may feed on plant matter or thrive in darkness while others may prefer to be near the top of the container where there is light.

After that, a serial dilution was made to prepare for next week’s lab. Starting with four tubes with 10 mL of sterile broth, 100 uL of liquid from the Hay infusion were pipetted into the first tube, labeled 10^-2. 100 uL from the 10^-2 tube was put into the next tube, labeled 10^-4. This process was repeated to create tubes with 10^-6 and 10^-8 dilutions. From each dilution, 100 uL was plated onto an agar plate and a tet+ plate, making a 10^-3 dilution. The same was done with the 10^-4 dilution on 10^-5 plate, the 10^-6 dilution on the 10^-7 plates, and the 10^-8 dilution on the 10^-9 plates. The plates were then incubated at room temperature for one week. Below is a diagram explaining the serial dilution.

Data and Conclusions

When observing the Hay Infusion, the water was a murky brown color and there was a thin white film with brown fuzzy matter covering the surface. It smelled similar to decomposing leaves. The white film on top was the only apparent life. From the wet mounted samples, we used the dichotomous key to determine organisms present. In the top niche, there were Peranema (motile, protozoa, not photosynthesizing, 100 um), Arcella (motile, protozoa, not photosynthesizing, 100 um), and Oedogonium (non-motile, algae, photosynthetic, 70 um). In the bottom niche, there were Colpidium (motile, protozoa, not photosynthetic) and Oedogonium (non-motile, algae, photosynthetic, 70 um). We were unable to find a third organism type for the bottom niche. Images of Peranema and Colpidium are included below.

Arcella is a type of amoebae that reproduces asexually. To eat, arcella engulf their food in their pseudopods. Generally, they eat diatoms, green algae or small protozoa. They thrive in wet environments like foliage, marshes and ponds.

If the Hay Infusion Culture were to continue to "grow" for another two months, I would predict that 1) there would be greater decomposition of the leaf litter and 2) the populations of protozoa a algae would increase in size. However, pressures for food and space would result from the population increases.

Hay Infusion Wet Mount: Top Niche with Peranema

Hay Infusion Wet Mount: Bottom Niche with Colpidium

CKL

1/19/16

AU Site 3 Transect Observations

Purpose:

The purpose of this lab was to create an aerial map of a 20 by 20 meter transect (site 3) and observe the abiotic and biotic components of this ecosystem. Additionally, samples were collected to observe protist life in the transect.

Materials and Methods:

To create an aerial map of the 20 by 20 meter transect, a map was first hand-drawn and later refined by using Google Earth images. Popsicle sticks marked the edges of Transect 3. While drawing the map, topography, abiotic, and biotic features were considered.

A representative sample of soil/ ground vegetation was collected randomly throughout the transect and placed into a plastic bag. The sample was used in a Hay Infusion Culture to study protist life present in the transect. Data and Conclusions:

Transect 3 is located in the American University arboretum with the Woods-Brown Amphitheatre to the North and Bender arena to the West. As for topography, the Western and Eastern edges of the transect are sloping down, but the land peaks on the left and right sides of the sidewalk. There is a depression in the land where the middle sidewalk is. All of the land in the transect is landscaped, with black plastic and mulch placed on site.

While observing the transect, many abiotic and biotic components were evident. Abiotic factors included (1) a light post, (2) black plastic under the mulch, (3) cigarettes, (4) rocks, and (5) concrete sidewalk. Biotic factors included (6) a large tree, (7) a bush, (8) lichen, (9) low shrubs, and (10)a spider. Below is an aerial map of transect 3 and the biotic/ abiotic factors within it labeled by the above numbers.

CKL