DESICCATION AND RECOLONIZATION OF PHYTOBENTHOS IN A REGULATED DESERT RIVER: COLORADO RIVER AT LEES FERRY,

Abstract

We tested the recolonization of the phytobenthic community in the tailwaters of Glen Canyon Dam following longand short-term experimentally induced desiccation. The response of Cladophora glomerata, Oscillatoria spp., miscellaneous phytobenthos species and periphyton was studied over 18 weeks using three treatments: (1) undisturbed control cobbles from the submerged zone; (2) cobbles desiccated and replaced into the submerged zone; and (3) cobbles desiccated and replaced into the varial zone. Periphyton density and compositional response resulting from these treatments were also examined. Desiccation treatments were significantly different in biomass from controls throughout the study. The biomass of desiccated and replaced river cobbles averaged �30 % of the controls for C. glomerata and periphyton during the 18-week recolonization period. In contrast, the biomass of the control Oscillatoria and miscellaneous phytobenthos species averaged only 3 and 50 % of that in the desiccation treatments, respectively. Cladophora, the dominant alga, comprised 77 % of the phytobenthic biomass. A significant positive relationship between discharge, Cladophora and periphyton biomass was present in all treatments, while there was a negative relationship with discharge for Oscillatoria and miscellaneous phytobenthos species. There was a significant inverse correlation, as well as a pattern of separate biomass dominance, between C

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oai:CiteSeerX.psu:10.1.1.208.6788Last time updated on 10/22/2014

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