Effects of aquatic macrophytes on physico-chemical conditions of three contrasting lowland streams : a consequence of diffuse pollution from agriculture?

• Published in: Water Science & Technology Vol. 43; no. 5; pp. 163 - 168
• Main Authors: WILCOCK, R. J, NAGELS, J. W
• Format: Conference Proceeding Journal Article
• Language: English
• Published: London IWA 01.01.2001; IWA Publishing
• Subjects: Agricultural management; Agricultural pollution; Agricultural watersheds; Agriculture; Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Applied ecology; Applied sciences; Aquatic plants; Biological and medical sciences; Catchment area; Catchments; Continental surface waters; Diurnal variations; Earth sciences; Earth, ocean, space; Ecosystem; Ecosystems; Ecotoxicology, biological effects of pollution; Energy Metabolism; Engineering and environment geology. Geothermics; Eutrophication; Exact sciences and technology; Floating plants; Fresh water environment; Freshwater; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Macrophytes; Mineral nutrients; Natural water pollution; Nutrients; Organic loading; Oxygen - analysis; Oxygen - metabolism; Pasture; pH effects; Photosynthesis; Plants; Pollution; Pollution, environment geology; Respiration; Riparian vegetation; Rivers; Saturation; Soil and water pollution; Soil science; Stream pollution; Streams; Sustainability; Temperature; Water Pollution - analysis; Water treatment and pollution; Diffuse source; Surface water; Water quality; Agriculture; Stream; Water pollution; Aquatic plant; Chemical properties; Diurnal variation; Dissolved oxygen; Physical properties
• ISBN: 1900222698; 9781900222693
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2001.0277

Three lowland streams in developed pasture catchments with different farming intensities exhibited contrasting summer diurnal variations in pH, DO and temperature. These are ascribed to differences in dominant aquatic vegetation and their respective effects on shade, and on photosynthetic production and respiration within each stream. The stream dominated by submerged macrophytes had the greatest amplitude swings in DO and pH, and DO levels of 86-128% saturation. Floating marginal macrophytes reduced photosynthetic inputs while providing additional organic loading for respiration, with consequent flat DO and pH curves and conditions not conducive to healthy stream ecosystems. The third stream was shaded by riparian plants, which inhibited photosynthetic effects on DO and pH so that diurnal variation was intermediate between the other two streams. The interaction between nutrients and increased insolation in agricultural catchments, in stimulating aquatic plants, needs to be better understood for managing the sustainability of stream habitats and ecosystems.