Week 5 Pondcast Black Pond, Ann Arbor, MI

January 31, 2010 1:15 21.2°F, -6°C

Week 5 of 2010 above the surface of Black Pond was, in a word, boring. True, we did see the return of our mouse, Pond Rover. But most life was that of the rodent (squirrel), canine (dog) and primate (human) variety.

Life under the pond seems to be where the action is happening. Although we did not collect a fresh water sample in Week 5, on Feb. 3, we observed the sample collected two weeks earlier, on Jan. 18.

The populations of ostracods (seed shrimp) and copepods (cyclops) were reduced. It was first suspected that these organisms had settled down into the layer of detritus on the bottom of the sample jar. Or perhaps, in the case of the copepods, they had completed their life cycle by depositing eggs within the two-week period. Two copepods with egg sacs were observed. One had two intact egg sacs, while the other had only one egg sac. Were the eggs already deposited, or were the eggs eaten by a predator?

A number of slowly moving, vertical white lines of about 3 mm had appeared on the sides of the jar. Upon further investigation, it appears that we are in the process of observing predator/prey interactions in an enclosed ecosystem - a peanut butter jar of pond life. These white lines were most likely midge fly larvae, as evidenced by the spike-like projections on the sides of their bodies when viewed under the microscope. -- Correction (15Feb10) - these white lines are a type of worm, most likely from the family Naididae, in the Oligochaete subclass of the phylum Annelid.

Other white lines were observed, which grew and shrank as they moved about on the microscope slide. These lines were most likely flatworms. Unfortunately, this time I was only able to capture video imagery of them in small form.

One small flatworm did move about freely, without contorting it’s body. On the same microscope slide, the flatworm encountered a shell-like organism, which seems to be a bivalve mollusk. The mollusk was smaller than 0.33 mm. No attempt by the flatworm to consume the mollusk was observed.

One large (about 5 mm) red-segmented worm was observed and digitally captured. From the Oligochaete class of the phylum Annelid, this worm scavenges on living and non-living organic matter, much like it’s cousin, the earthworm.

Join us next week for Pondcast 6, when we take another depth measurement from the middle of the pond with a longer, stronger measurement device, collect another sample of pond water and continue to observe previously collected samples.

Stefan Szumko is a middle school science teacher by trade, an outdoor environmental educator by calling, and a homedaddy by choice. Stefan can be reached at slugwhisperer@gmail.com.