Are Odonata nymph adversely affected by impaired water quality in urban streams

Globally 10% of all dragonfly species are threatened by extinction that can be primarily attributed to a loss of natural habitat. Urban expansion and the associated urban stream syndrome has established that the extent and intensity of urban development is directly linked to a range of adverse physical, chemical and ecological changes. Urban waterways typically experience degraded water quality and are occupied by impaired communities of aquatic invertebrates which are mostly dominated by rapid colonizing insects. Odonata are a diverse insect group and their tolerance or sensitivity to urban waterway degradation is unclear. This research examined the response of aquatic macroinvertebrate communities and specifically the Odonata nymph community to impaired water quality and degraded riparian vegetation condition in streams of the Georges River catchment, Sydney, across an urban development gradient. Unlike the overall macroinvertebrate community, Odonata nymph species assemblages were not strongly linked to the urban development gradient nor the degree of degradation in water quality. This result diverges from many aquatic macroinvertebrate studies that have reported a correlation between the response of Odonata taxa to degraded water quality. Our findings conclude that Odonata nymph community alone are not a suitable indictor of urban stream degradation as measured by water quality or catchment imperviousness and that the conservation of urban dragonflies should place a greater focus on the conservation and creation of suitable habitats.