Nutrient and light limitation of periphyton in the River Thames: Implications for catchment management

Abstract

This version available http://nora.nerc.ac.uk/16072/ NERC has developed NORA to enable users to access research outputs wholly or partially funded by NERC. Copyright and other rights for material on this site are retained by the rights owners. Users should read the terms and conditions of use of this material at http://nora.nerc.ac.uk/policies.html#access NOTICE: this is the author's version of a work that was accepted for publication in Science of the Total Environment. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Science of the Total Environment [434, 201-212 (2012) . Decreasing ambient SRP concentration from 225 µg l -1 to 173 µg l -1 had no effect on periphyton biomass accrual rate or diatom assemblage. Phosphorus limitation became apparent at 83 µg SRP l -1 , at which point a 25 % reduction in periphyton biomass was observed. Diatom assemblage significantly changed when the SRP concentration was reduced to 30 µg l -1 . Such stringent phosphorus targets are costly and difficult to achieve for the River Thames, due to the high population density and intensive agriculture within the Thames basin. Reducing light levels by shading reduced the periphyton accrual rate by 50 %.Providing shading along the River Thames by planting riparian tree cover could be an effective measure to reduce the risk of excessive algal growth. If the ecology of the Thames is to reach the WFD's "good ecological status", then both SRP concentration reductions (probably to below 100 µg l -1 ) and increased shading will be required.

Identifying multiple stressor controls on phytoplankton dynamics in the River Thames (UK) using high-frequency water quality data

“…Other studies of the River Thames have come to similar conclusions (Bowes et al, 2012b;Hutchins et al, 2010). It also has implications for the potential impact of future climate change.…”

“…Again, this suggests that multiple factors are limiting periphyton growth. The two potentiallylimiting macronutrients for phytoplankton within the River Thames system; soluble reactive phosphorus and dissolved reactive silicon (which is required by diatoms to construct frustules) (Bowes et al, 2012b), showed negative relationships due to algal uptake resulting in depletion (Bowes et al, 2011), with the highest chlorophyll concentrations coinciding with the lowest P and Si concentrations.…”

Within-River Phosphorus Retention: Accounting for a Missing Piece in the Watershed Phosphorus Puzzle

“…After effluent P remediation within-river P retention reduces ambient P concentrations to levels which, while still above the numerical water standard adopted by Oklahoma, may still be capable of limiting nuisance algal growth 59,60 .…”

Phototrophic periphyton techniques combine phosphorous removal and recovery for sustainable salt-soil zone

“…High (45°C) or low (5°C) temperature could restrain P removal capacity of periphytons. One possible explanation was that the light, temperature and P concentration could affect the normal growth of periphytons, such as altering the species composition and its characteristics, the release of extracellular organic carbon (EOC) and EPS from living algal cells in biofilms (Bowes et al, 2012;Espeland & Wetzel, 2001;McCormick et al, 2001;Vander Grinten et al, 2004), subsequently influencing the function of periphyton such as its adsorption capability. Therefore, environmental conditions, especially the water flow Fig.…”