The torch is passed

I've passed my microcosm maintenance duties to other students and so the microcosm blog will be taking a hiatus.

Baseline Monitoring

Here are plots of the routine monitoring data that is collected from the microcosms - temperature, pH, electrical conductivity (EC), and oxidation reduction potential (ORP) - from the beginning of data collection August 17 through September 30. We also make readings of dissolved oxygen (DO) and todal dissolved solids (TDS). The EC has trended upward, due to evaporation and possibly dissolution of salts from the sediments. The pH rose early on and has leveled out at an average value of 8.55. Temperature is stable around 22 degrees C. The ORP is variable. I hypothesize that ORP is correlated with water level in the tank and the subsequent ammount of oxygenation. I'll report back soon. The data from different sampling locations in the microcosm tracked each other well, and indication of good mixedness. To look at the individual data points, you can download the raw data.

Gas production in the wetland

The sediments of the wetland microcosm are rich in organic matter and microbial activity. As the oxygen of the sediments is reduced, noted by the color change in the sediments as seen in the photo, bacteria begin using other molecules as teminal electron acceptors for the oxidation-reduction reactions involved in their metabolic processes. When the redox potential is sufficiently reduced, the bacteria create hydrogen sulfide or methane gases, which accumulate in pockets of the sediments before escaping into the water column. We have set up a gas sampler to capture gases created in the microcosm and will report back.

A few more pictures of the inhabitants of the wetland microcosms. I have now seen two damselflies perched on the emergent vegetation of the microcosms. On Friday I caught two nymphs that had made their way into the sump filters (at first I thought they were minnows). I kept them in their own enclosure over the weekend, hoping to see them molt, but decided today to re-release them to the microcosm to feed and molt into adults. Note the gills at the end of their tails. Also here is a new shot of the biggest and baddest of our crayfish, now isolated in his own tank after tearing the claws off the smaller one. And finally a shot of one of the Sacramento perch who is also starting to get bigger.

Microcosm Construction