EFFECTS OF SUSPENDED SEDIMENT ON BIOMASS AND CELL MORPHOLOGY OF CLADOPHORA GLOMERATA (CHLOROPHYTA) IN THE COLORADO RIVER, ARIZONA

This study assessed changes in biomass, filament length, and cell morphology in Cladophora glomerata (L.) Kütz. along a suspended sediment gradient in the Colorado River below Glen Canyon Dam, Arizona. Suspended sediments ranged from 2.0 mg·L⁻¹ at Lees Ferry (Rkm 0.8) to 4.2 mg·L⁻¹ at Gorilla Island (Rkm 352). There was a 74% decrease in Cladophora biomass along the river transect through Grand Canyon National Park and a significant decrease in filament and cell length, but cell width increased. Similar changes in cell morphology occurred after 19 days when C. glomerata was transplanted from a low suspended sediment site (2.0 mg·L⁻¹) at Lees Ferry to a habitat with high suspended sediments (≥20.0 mg·L⁻¹). Cell length increased and cell width decreased when plants were transplanted back to the low suspended sediment habitat for 24 days. In situ studies with reduced light in the absence of suspended sediments showed no change in cell morphology. These in situ experiments imply that changes in cell morphology by C. glomerata in waters with high suspended sediments are adjustments in structural integrity to accommodate the abrasive force of suspended particles. Our study suggests that cell dimensions in Cladophora might be too plastic under varying environmental conditions to be used in taxonomic determinations.