Dredging, commonly used as a form of remediation, removes contaminated sediments in river ecosystems, which may also lead to loss of habitat and food resources for benthic macroinvertebrates (MIV). This study analyzed the recovery of the Fox River, WI from polychlorinated biphenyl (PCB) remediation during and post-dredging from three study sites below the De Pere dam from 2013-2017. We predict that dredging has a negative effect on the recovery of the Fox River in short-term and longer-term scales. Water quality samples were taken using YSI probes. Macroinvertebrate (MIV) samples were taken three times per summer at each study site. Data was analyzed using the following statistical tests: one way ANOVA, pairwise comparison, and Tukey's Honest Significant Difference test.
Results/Conclusions
Analyses show that the total abundance of MIV species was significantly lower in years directly post-dredging at study site 1 (p < 0.001) and site 2 (p = 0.038). Abundance of physidae (Site 1; p ≤ 0.049 & Site 2; p ≤ 0.003), oligochaete (Site 2; p ≤ 0.003), and chironomidae (Site 1; p = 0.003 & Site 2; p ≤ 0.001) were significantly lower in some study sites when comparing post-dredge years. Dreissenidae abundance was significantly lower at Site 1 (p ≤ 0.007) for the majority of years post-dredging, and species diversity (H’) at this site was lower the year after dredging was completed (p=0.027). Lower MIV abundance and diversity may be due to the inability of the river to recover lost sediment deposits in the short-term and thus the MIVs have reduced resources. Based on our preliminary findings, dredging had detrimental consequences on macroinvertebrates in the lower Fox River in 2013-2017. Further study of the potential effects of disturbance from dredging on benthic macroinvertebrates in river ecosystems is needed.