Community Structure And Longitudinal Patterns Of Benthic Invertebrates In A Heavy-Metal Contaminated Alaskan River System

Abstract

Community structure of stream invertebrates was investigated in a heavy-metal contaminated watershed in Denali National Park, Alaska. Three sites were located on Stampede Creek, with one station above an antimony mine (active 1916-1970) and two stations below. An additional site was located on the Clearwater Fork of the Toklat River downstream from the Stampede Creek confluence. Quantitative samples of benthic invertebrates and associated coarse ($>$1 mm) detritus were obtained in late June (early spring), late July (summer), and late August (early fall).<p> Gut analyses allowed categorization of insects to functional feeding groups. Water temperatures increased and detrital storage generally decreased downstream. Abundance of shredders was positively correlated with abundance of coarse detritus at the headwater site. Longitudinal changes in functional group composition were consistent with the River Continuum Concept. Heavy metal contamination appeared to affect taxonomic and functional groups differentially. Grazers and predators were severely underrepresented directly downstream from the mine. <p>