Mindy Forsyth (Biology) Virginia Polytechnic Institute and State University
Over the summer of 2007, the zooplankton concentration and CNP were compared to different aspects of retention ponds. These aspects included pond size, runoff area, impervious cover, and age. Before the project began, the expected result was that impervious cover would be the biggest determining factor. As it increased, it was thought that the concentration and CNP of the zooplankton would decrease because there would be more pollution that ran into the ponds.
The project started in the field where plankton was collected with a filter and a plankton net, and then the concentration and carbon, nitrogen, and phosphorus ratios were obtained in the lab. GIS was used to obtain pond size, runoff area, and impervious cover, and James City County provided some information that could be used.
When the independent and dependent variables were compared, it was found that pond size and runoff area did not have any correlations with the concentration and CNP. The larger ponds and runoff areas were consistent with each other, however, with similar concentrations and CNP. There was no relation with the GIS impervious cover, but there was a positive relation with the JCC impervious cover with concentration and N:P. There was no relationship with age. It was also interesting to see that the data was different than the Redfield Ratio which states that the plankton ratio should be 106 C: 16 N: 1 P. The data showed C:P in the 1000s and N:P in the 100s. Additionally, copper sulfate also did seem to affect the zooplankton.
All in all, there were some relations but there were not strong. Some further research may be able to find stronger correlations especially if one variable is focused on and others kept constant.
For additional documentation Mindy Forsyth provided a PowerPoint Presentation entitled "Zooplankton in Retention Ponds" provided here in PDF form.