Dredging of sediments filling in submarine shipping channels and harbors re-releases environmental toxins that have already accumulated in nearshore marine sediments. Dredging also releases fine sediments rich in organic matter that contribute to anoxia and other detrimental benthic environmental impacts in the vicinity (Figure 17.29). The material that settles in harbors, shipping channels, and inland waterways are in constant motion during dredging operations, and wildlife habitats that might be able to tolerate a few days of high turbidity are endangered by the unending release of fine-grained sediments released by a long-term dredging operation.
Figure 17.29. A dredging operation like this one works to remove silt from clogged shipping channels.