Riparian shading controls instream spring phytoplankton and benthic algal growth. Issue 6 (18th May 2016)

• Record Type: Journal Article
• Authors: Halliday, S. J.; Skeffington, R. A.; Wade, A. J.; Bowes, M. J.; Read, D. S.; Jarvie, H. P.; Loewenthal, M.
• Is Part Of: Environmental science. Volume 18:Issue 6(2016)
• Page Start: 677
• Page End: 689
• Publication Date: 2016-05-18
• Subjects: Environmental monitoring -- Periodicals; Biological monitoring -- Periodicals; Environmental chemistry -- Periodicals; 363.7363
• DOI: 10.1039/c6em00179c
• Languages: English
• ISSNs: 2050-7887

Abstract

Abstract : High-frequency monitoring shows the importance of riparian shading in controlling benthic algal growth and stream metabolism in a small river. Abstract : Dissolved oxygen (DO) concentrations showed a striking pattern in a multi-year study of the River Enborne, a small river in SE England. In each of three years (2010–2012), maximum DO concentrations were attained in mid-April, preceded by a period of steadily increasing diurnal amplitudes, followed by a steady reduction in both amplitude and concentration. Flow events during the reduction period reduce DO to low concentrations until the following spring. Evidence is presented that this pattern is mainly due to benthic algal growth which is eventually suppressed by the growth of the riparian tree canopy. Nitrate and silicate concentrations are too high to inhibit the growth of either benthic algae or phytoplankton, but phosphate concentrations might have started to reduce growth if the tree canopy development had been delayed. This interpretation is supported by evidence from weekly flow cytometry measurements and analysis of the diurnal, seasonal and annual patterns of nutrient concentrations. As the tree canopy develops, the river switches from an autotrophic to a heterotrophic state. The results support the use of riparian shading to help control algal growth, and highlight the risks of reducing riparian shade.