In the fall of 2008, Jeff Levinton and I taught a course called "Restoration of Aquatic Ecosystems." Foundry Cove is a tidal marsh on the Hudson River in New York, across from West Point. Pollution began in colonial days when it was the site of a metal foundry. By the 1960's it was the site of a battery factory. Literally millions of tons of solid and liquid Cadmium waste were dumped into the marsh. It was eventually declared a superfund site and cleaned up in the mid 1990's. Our class goal was to evaluate the success of the restoration.
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View of the Hudson and the coves, facing south from Breakneck Ridge. South Cove, Constitution Marsh and Foundry Cove are visible in the left of the picture (from top to bottom). West Point and the Hudson River are on the right. Cold Spring NY is seen in the bottom. |
The class consisted of 12 talented undergraduates from Stony Brook University. after learning about the background history of the marsh, the class was divided into three teams. These teams were constructed to take advantage of collaborative learning. Students were each accountable to their group-members, inspiring greater motivation. The students each had specific roles in their own areas of strength and helped to teach the others in their groups. Despite this grouping, the students in the course showed strong willingness to assist other groups as well as their own. The goals of the groups were as follows:
Group 1: Determine the amount of Cadmium still present in the marsh, by sampling soil, water and suspended particles.
Group 2: Compare the diversity and abundance of benthic invertebrates in Foundry Cove with that of another, non-impacted marsh.
Group 3: Evaluate the tolerance of benthic organisms to Cadmium (specifically, the oligochaete
Limnodrilus hoffmeisteri)
We took several field trips to Foundry Cove. We collected many water and sediment samples, we used a polgar grab to obtain samples of benthic organisms and we collected buckets and buckets of fresh mud to create live cultures of
L. hoffmeisteri.
Group 1 prepared their samples and had them analyzed by spectrometry. They found a surprising level of Cadmium was still present in the marsh and in the water exiting the marsh on the falling tide- approximately 8 ppm. However, it was a huge reduction, especially considering that at one time mud near the battery factory's outflow pipe had Cd concentrations up to 250,000 ppm.
Group 2 found that Foundry Cove had reasonably similar composition, diversity and abundance of benthic animals to South Cove, the control marsh. There was one exception: they found many more zebra mussels (a troublesome invader) in Foundry Cove. They suggested that the reason for this is that the sediment used to refill the marsh after the cleanup had larger and more abundant rocks than South Cove. South Cove had thousands of years of soft sediment accumulation; the new rocks in Foundry Cove provided new substrate for zebra mussels.
Group 3 conducted a 24-hr survival analysis of the worms from Foundry Cove, comparing those exposed to Cadmium to un-exposed controls. During the height of pollution, the worms of Foundry Cove evolved resistance to Cadmium toxicity and could survive much longer when exposed. The students found that post cleanup, the worms seem to have lost this resistance.
Jeff Levinton produced the results from a similar class that had been conducted in Foundry Cove in the 1980's, during the height of pollution. We compared the results of the too classes. Two things were apparent: 1) The restoration of Foundry Cove was a significant improvement and 2) the current students did much more work and a much better job than the old students.
This was a great class for me to teach. In addition to the fun of working (and canoeing) in the Hudson River, the students all really grew as scientists. They were shy and unsure of themselves at the beginning of the course, and I even questioned some of the students' motivation. By the end of the course, they were all confident and competent in the lab and field. I would have taken any one of them as a research assistant in the laboratory. The students loved the course too. This was the first experience doing "real science" for many of them, and for the others, it was the most fun.
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Lauren, of group 3, and I collected many buckets of mud, from which Group 3 cultured worms to use in their survival experiments.
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One of the first visits to the marsh. Here the students are learning about the natural history of the marsh. |
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Group1 (and Jeff Levinton) spent a whole tide cycle at the inlet to the cove to measure the volume of water exchanged. They used this information along with their analysis of Cd concentration to estimate daily export. |
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Group 2 searches their benthic sampled for infaunal organisms like oligochaetes, crustaceans and many others. |
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Collecting a water sample. |
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Some of the students developed good leadership skills in the course. |
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In their final presentation, Group 2 compared their results to those of the 1980's class. |