Friday, February 19, 2010

Pond Rescue

This afternoon Norm and I headed out to Will's Marsh to check on the oxygen level in the water. It is a very shallow pond, only 3 - 6 feet deep in most places. A complete cover of ice/snow has blanketed it since November. This causes the oxygen level in the unfrozen water beneath the ice to steadily drop. There is no unfrozen surface water to gather oxygen from the air. It is critical to help our frogs and fish survive in the depths of the pond by adding oxygenated water from the well in late/mid winter if oxygen levels drop too low.
Norm and I headed out onto the ice, and I used a pulaski to break a hole in the surface of the pond. Immediately my nostrils were filled with the stench of rotten eggs. This is not a good sign; it indicates an anaerobic (unoxygenated) environment. I stuck my hands in the ice-cold water and gathered a small sample of water. We weren't the only ones that had been out on the ice: a couple sets of jackrabbit tracks crossed our path, the alternate walking pattern of foxes criss-crossed them, and one set of cross-country ski tracks went clear across the pond as well.
Back in the lab Norm ran a test for oxygen content in the water. The results were dismaying! The oxygen level had dropped to a critically low level. Norm headed out immediately to start the pump in the well in order to add water onto the north side of the pond, where it will fill in under the ice and bring in fresh oxygen. We hope that we can save the hibernating fish, frogs, and turtles! Deep Mill Pond doesn't have this problem as it is two or three times deeper than Will's Marsh. Will's is a marsh after all, but we'd like to make sure it is hospitable for frogs, fish, and turtles. This means it requires a bit more water than a typical marsh. We'll be keeping our fingers crossed.


  1. Heather, this is very interesting. I had no idea you would need to oxygenate water for the hibernating critters. Any update on the frogs, fishes, and turtles? When will you know how they're doing?

  2. Susanne, we hit a snag: the well is not working, and so we were unable to add fresh water after all. The alternative plan is to make holes in the ice in several locations in order to allow some natural oxygen exchange to take place. I think Norm and I will work on that tomorrow. Thanks for following my blog!

  3. One more thing to add, Susanne, in response to your comment: our ponds don't have any in and out flow of water, and in this sense they are more like marshes. A lot of ponds are fed, and drained, by streams/creeks so that they have a natural fresh source of oxygenated water even in the winter.