Effects of stream velocity and phosphorus concentrations on alkaline phosphatase activity and carbon:phosphorus ratios in periphyton

• Published in: Hydrobiologia 2019, Vol.826 (1), p.173-182
• Main Authors: Hiatt, Daniel L., Back, Jeffrey A., King, Ryan S.
• Format: Article
• Language: English
• Subjects: Alkaline phosphatase; Biogeochemistry; Biomedical and Life Sciences; Carbon; Climate change; Drought; Ecological function; Ecology; Extreme weather; Freshwater & Marine Ecology; Hypotheses; Life Sciences; Metabolism; Mud-water interfaces; Perennial streams; Periphyton; Phosphatase; Phosphates; Phosphorus; Primary Research Paper; Ratios; Rivers; Stream discharge; Stream flow; Velocity; Water velocity; Zoology
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/s10750-018-3727-4

We studied several streams spanning a steep dissolved phosphorus (PO 4 –P) gradient to test the hypothesis that faster stream velocity would reduce alkaline phosphatase activity (APA) and carbon:phosphorus (C:P) of benthic periphyton because higher velocities should increase the supply rate of dissolved phosphorus at the community–water interface. We tested the hypothesis that the differences in APA and C:P between fast and slow velocity locations within a stream reach would decline as stream PO 4 –P concentrations increased, and, therefore, velocity effects should be the greatest at low levels of PO 4 –P. APA declined in response to both the increased water velocity and PO 4 –P, but the effect of velocity on APA was negligible at the highest levels of PO 4 –P. Further, we found a strong, negative relationship between periphyton C:P and PO 4 –P levels as hypothesized, but did not detect significant relationship between C:P and velocity after accounting for the effects of PO 4 –P. The lack of an effect of velocity on C:P is probably due to the higher levels of APA in low-velocity, low PO 4 –P reaches, as the higher APA rates reflect an alternative pathway for acquiring sufficient PO 4 –P to sustain periphytic growth and metabolism. These results have important implications for stream ecosystem function because of the increasing frequency of extreme weather events associated with the climate change, particularly droughts that reduce or eliminate perennial stream flow, and further illustrate the important effects of stream flow on biogeochemical processes.