Pale Snaketail emerges in urban river under dissolved oxygen stress

Pale Snaketail dragonflies emerged this month along the South Platte River — a finding that carries weight in an urban waterway. These elegant damselflies (Gomphus pallida) require clean, well-oxygenated streams with gravelly bottoms to complete their aquatic nymph stage, which typically spans two to four years buried in sediment. A single adult snaketail is therefore a window not into this season's conditions, but into water quality that held steady years in the past, when that nymph was developing.

That context makes the current crisis harder to reconcile. Dissolved oxygen in the creek system has collapsed this month, plummeting to 2.8 milligrams per liter — well into lethal stress for most aquatic invertebrates. Whether the larva that became this adult found a cleaner refuge upstream, or simply experienced milder conditions before the freefall, remains unknown. What is clear is that the broader dragonfly community — Widow Skimmers, Common Green Darners, Blue Dashers, and a dozen other species active in the parks and ponds along the Platte — reminds us how much ecological work these urban water bodies still perform. Even as the river itself teeters, they hold.