, Volume 154, Issue 1, pp 49-59

Effects of physical disturbance and canopy cover on attached diatom community structure in an Idaho stream

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access

Abstract

A field experiment was conducted to determine the effect of disturbance frequency on diatom communities established on artificial substrates within an open canopy site and a closed canopy site of a 3rd order stream. The open canopy site (OCS) had a total of 80 diatom taxa colonizing the substrates, while the closed canopy site (CCS) had only 55 taxa. Cluster analysis revealed that the two sites had distinct diatom communities, although the most common species were similar between sites. There was no effect of disturbance frequency on species diversity (H') at OCS, however species diversity significantly decreased as disturbance frequency increased at CCS. At OCS, Amphora perpusilla increased in abundance as disturbance frequency increased, while Navicula lanceolata abundance decreased as disturbance increased. At CCS, Cocconeis placentula v. euglypta remained dominant regardless of disturbance frequency. The results suggest that some diatom species may be ‘shade adapted’, which may explain the site-specific responses. In addition, diatom growth-forms may explain the within site taxon-specific responses to disturbance. For example, Achnanthes sp. and Cocconeis sp., small horizontal forms, were predominant on the high disturbance substrates. Vertical or large horizontal forms may be mechanically removed by frequent physical disturbance allowing such small horizontal forms to become abundant. Frequent disturbance, by maintaining the community in an early stage of development, directly influences the diatom assemblage on rocks in streams.