Effect of Turoa oil spill on aquatic insects in the Mangawhero river system

Abstract

Oil (17,000 1) was spilled from Turoa Skifield on Mt Ruapehu and entered the headwaters of the Mangawhero and Makotuku Rivers where it persisted for up to 5 months. Brown trout, rainbow trout, long-finned eels, and blue duck were not killed. However, in the upper reaches, aquatic insects were disturbed and killed by the oil spill within 2 weeks. The total numbers of aquatic insects were not significantly affected at the lower stations within Tongariro National Park over the following year. The mayflies Deleatidium nr myzobranchia B and D. nr lillii A (Ephemeroptera: Leptophlebiidae) were significantly reduced in numbers in the Makotuku River following the oil spill and may be indicator species for oil pollution. Comparisons with overseas studies confirmed a recovery time of at least 6 months for the “sensitive” orders of aquatic insects following an oil spill of this magnitude.