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Riparian shading controls instream spring phytoplankton and benthic algal growth.
S J Halliday1, R A Skeffington, A J Wade
1Department of Geography and Environmental Sciences, University of Reading, Reading, RG6 6AB, UK. r.a.skeffington@reading.ac.uk.
Environmental Science. Processes & Impacts
|May 19, 2016
Summary
Dissolved oxygen (DO) levels in the River Enborne peaked in mid-April due to benthic algal blooms. Riparian tree canopy growth suppressed these blooms, shifting the river ecosystem. Riparian shading is crucial for managing algal growth.
Area of Science:
- Environmental Science
- River Ecology
- Limnology
Background:
- Dissolved oxygen (DO) dynamics in rivers are critical for aquatic ecosystems.
- Benthic algal growth significantly influences riverine DO concentrations.
- Riparian vegetation plays a key role in regulating light availability and nutrient cycling in rivers.
Purpose of the Study:
- To investigate the multi-year patterns of dissolved oxygen (DO) in the River Enborne.
- To determine the primary drivers of seasonal DO fluctuations, particularly the role of benthic algae and riparian canopy.
- To assess the impact of nutrient concentrations and flow events on riverine DO.
Main Methods:
- Multi-year study (2010-2012) of dissolved oxygen (DO) concentrations and diurnal amplitudes.
- Analysis of nutrient concentrations (nitrate, silicate, phosphate).
- Weekly flow cytometry measurements and seasonal/annual pattern analysis.
Main Results:
- Maximum DO concentrations consistently occurred in mid-April, preceded by increasing diurnal amplitudes.
- Benthic algal growth was identified as the main driver of high DO, suppressed by developing riparian tree canopy.
- Nutrient levels (nitrate, silicate) did not limit algal growth, but phosphate may have if canopy development was delayed.
- River ecosystem shifted from autotrophic to heterotrophic as the tree canopy developed.
Conclusions:
- Riparian shading is an effective strategy for controlling excessive benthic algal growth in rivers.
- Reducing riparian shade poses risks to riverine ecosystems by potentially increasing algal blooms and altering DO regimes.
- Understanding the interplay between riparian vegetation, algal dynamics, and DO is vital for river management.
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