Mass mortality of a dominant kelp (Laminariales) at Goat Island, north-eastern New Zealand

Abstract

In north-eastern New Zealand, monospecific stands of the laminarian Ecklonia radiata occupy rocky reefs at depths below 10 m on exposed shores. In the austral summer of 1992-93, mass mortalities of populations of E. radiata in the Cape Rodney to Okakari Point Marine Reserve near Leigh were recorded, in which 40-100% of the sporophytes at depths greater than 10 m died. Mortality was gradual, beginning with erosion of the laminae and ultimately progressing to the stipes, which eventually decayed. The mortality was first evident in the deepest plants and culminated in the elimination of large areas of kelp forest. The event was not associated with any previously reported mortality agents. Investigations of the effects of the mortality on other organisms are continuing.