Observation 4: 11/10/11

Observation 4

As with the other weeks, there was a good bit of water loss, this time around a third of the tank.

Overall, there was not a lot of change in the MicroAquarium. I did notice that the fungus I observed last week and the week before had diminished. The large mass was gone, but many of the hyphae were left, and other parts of the plant were now sprouting new hyphae. The fungus seems to have invaded this plant. I also noticed that one of my plants is now dead, and almost completely consumed by the organisms feeding on it. The Aeolosoma and seed shrimp have been feeding on it so actively, that now very little of the plant remains.

In all layers of water, there was a an extreme decrease in the number of single-celled organisms. I could find only very few-near the plants, in open water, or near the dirt. The high numbers of larger organisms might be a factor in the decrease of this population. These single-celled organisms might be a food source for some of the larger organisms. I also saw a sharp decrease in the long, green diatoms. I only saw a few left on the bottom of the tank.

One organism did increase, however. Along with the three cylops that I usually see, I saw at least 5 cyclops nymphs. I believe that if the observations continued on for longer, this population would see an increase.

Throughout these observations, the trends seemed to favor an overall boom in microscopic population, then steadied off on average. The exception to the unchanging numbers would be the single-celled organisms and diatoms, which decreased, and the cyclops population, which seems to be increasing. The addition of the food pellet, the loss of water, and the food web interactions are all factors I believe contributed to these trends.

Observation 3: 11/3/11

Observation 2
As with last week, there was substantial water loss, with half the MicroAquarium dry.

I saw a new organism this week, which I was unable to identify with any of the charts in the lab. Dr McFarland was unavailable for assistance at the time, and the organism crawled away into the dirt. It was around the size of a cyclops, circular, and had three legs per side. On its head it had two small "feelers" or "antennae." It could not swim freely, and relied solely on one of the plants to crawl around. It's movement was slow, but almost spider-like. I hope to be able to identify it next week.

Also of interest, I seem to have a fungus growing on one of my plants. I believe it to be a member of phylum Zygomycota, as I could see a few zygosporangium. I first noticed it during observation 2, but was only able to identify it as a fungus this week, after it had grown and begun spreading down the plant. The organisms do not seem to be feeding on the fungus the way they feed on the two plants.

Overall, there was a significant increase in the single-celled populations. On the 10x objective lens, I could see single-celled organisms in every layer, at every depth, near and far from the plants. None seemed very active.

Many of the larger organism populations remained unchanged. I still saw three cyclops, a cyclops nymph, and the same number of Aeolosoma. The one exception was the seed shrimp, whose numbers grew to reach 30 in the bottom layer alone. All the seed  shrimp I observed were very actively feeding on the plant life.

Near the bottom of the aquarium were some dead organisms, the same organisms I saw at the previous observation. All were diatoms.