Don Barber Bryn Mawr College

mixing/stratification in a hydrologic basin;
solubility of oxygen in water as function of temperature;
primary productivity, O2/CO2 consequences of photosynthesis/respiration;
deposition of organic-rich sediments in a restricted basin setting

survey planning/design; mapping; construction of cross-sections; drawing contours; field observations: sampling and recording data; spreadsheet data analysis and calculations

posing testable hypotheses; applying spatial and quantitative reasoning for pattern evaluation; interpreting and synthesizing results of observations

experience operating water quality meter in field setting; coordinating/cooperating with other team members and with team assigned to different tasks

Undergraduate entry/advanced level, but probably could work at 9-12th grade levels, too, if classes are small.

It is helpful to have some students with basic mapping/map-reading skills as learned in an introductory geology course, but not necessary for all participants. Facility with a spreadsheet program such as Microsoft Excel speeds the data analysis/reduction/plotting process.

Carried out during a 3-hr lab period for either introductory or mid-level undergraduate courses; builds on some material presented earlier, but almost can stand alone.

A small boat is used to survey across pond (ideally--other approaches can work, too).
A portable, battery-powered, submersible water quality meter on a cable is required. These range in price; unit must include at least temperature and dissolved oxygen sensors for this exercise.
Computers are helpful for spreadsheet work, although plots could be made on graph paper with use of a calculator.
One also needs info on the equilibrium saturation of dissolved oxygen in water vs. water temperature (students can look this up).

Main problem is getting students out on water SAFELY to make observations.
Water quality meters are generally reliable and simple to use, but needs to be carefully checked well in advance.
This project is seasonally dependent; summer or early fall works better, while there is still lots of plant photosynthesis near surface, and pond is temperature stratified. Winter/early spring would be least interesting if pond is homogeneous at 4 degrees C and no plant growth and little decay.

I'm curious about whether students adequately conceive of the pond setting as a small scale analogue of larger hydrographic and depositional environments, and whether they are able to use this knowledge in understanding these larger systems.

No pre-testing has been done, although student experiences with the activity have been gauged through questionnaires at end of course.

Sedimentology students use a small boat to measure vertical temperature and dissolved O2 profiles to evaluate a local pond as a small-scale basin wherein organic carbon-rich sediments are deposited. Students observe algal growth (i.e., photosynthesis and oxygen supersaturation) near the surface, whereas the sinking of excess organic matter into the poorly ventilated, deepest part of the pond produces suboxic-to-anoxic conditions and accumulation of organic-rich mud.