Dragonfly Biodiversity at Abandoned Work Sites: Dredge-spoil Ponds of the Chesapeake and Delaware Canal, New Castle County, Delaware

Abstract - There are few undisturbed, freshwater habitats remaining in the populated areas of the United States. Aquatic organisms, such as dragonflies (Odonata), have therefore either had to adapt to disturbed and modified secondary habitats, such as farms, golf courses, storm-water remediation basins, and community-park ponds, or risk extirpation. The species that readily adapt to these habitats are usually widespread common species. However, other aquatic habitats inadvertently created at abandoned work sites often evolve distinctive characteristics over time that provide refuge for species rarely or never found at deliberately created pond habitats. For 17 years, we have monitored the diverse Odonata fauna at several floristically distinct ponds formed in depressions left from the dredging of the Chesapeake and Delaware Canal in the 1960s. Among the species found are ones not known elsewhere locally or ones found in unusual abundance at 1 or more of the ponds, though infrequently encountered regionally. These dredge-spoil ponds are important for conserving regional Odonata biodiversity by providing unique habitats in an increasingly urbanized environment.