Functional Responses Associated with Growth Form in Stream Algae

Abstract

The relationship of growth form to phosphorus uptake, carbon fixation, and susceptibility to grazing was tested in stream algae. We hypothesized that algal species with high surface area: volume (SA:V) ratios would have higher biomass-specific rates of nutrient uptake and photosynthesis than species with low SA:V ratios. We also predicted that algal species with gelatinous or prostrate growth forms would have low susceptibility to grazing. Physiological measurements were made using ten taxa comprising five different algal growth forms commonly found in flowing waters (unbranched filamentous; branched filamentous; gelatinous, branched filamentous; gelatinous, colonial; and prostrate). Significant positive relationships were obtained between SA:V and phosphorus uptake, and SA:V and carbon fixation at high light (200 μmol quanta m -2 s -1 ), but only after two outlying taxa were deleted from the analysis. A significant regression was obtained between SA:V and carbon fixation at low light (...