Influence of stormflow and baseflow phosphorus pressures on stream ecology in agricultural catchments

Shore, Mairead and Murphy, Sinead and Mellander, Per-Erik and Shortle, Ger and Melland, Alice R. and Crockford, Lucy and O'Flaherty, Vincent and Williams, Lauren and Morgan, Ger and Jordan, Phil (2017) Influence of stormflow and baseflow phosphorus pressures on stream ecology in agricultural catchments. Science of the Total Environment, 590-591. pp. 469-483. ISSN 0048-9697

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Abstract

Stormflow and baseflow phosphorus (P) concentrations and loads in rivers may exert different ecological pressures during different seasons. These pressures and subsequent impacts are important to disentangle in order to target and monitor the effectiveness of mitigation measures. This study investigated the influence of stormflow and baseflow P pressures on stream ecology in six contrasting agricultural catchments. A five-year sub-hourly dataset was used consisting of stream discharge, P chemistry, macroinvertebrate and diatom ecology, supported with microbial source tracking and turbidity data.
Total reactive P (TRP) loads delivered during baseflows were low (1-7% of annual loads), but TRP concentrations frequently exceeded the environmental quality standard (EQS) of 0.035 mg L-1 during these flows (32-100% of the time in five catchments). A pilot microbial source tracking exercise in one catchment indicated that both human and ruminant faecal effluents were contributing to these baseflow P pressures but were diluted at higher flows. Seasonally, TRP concentrations tended to be highest during summer due to these baseflow P pressures and corresponded well with declines in diatom quality during this time (R2 = 0.79). Diatoms tended to recover by late spring when storm P pressures were most prevalent and there was a poor relationship between antecedent TRP concentrations and diatom quality in spring (R2 = 0.23). Seasonal variations were less apparent in the macroinvertebrate indices; however, there was a good relationship between antecedent TRP concentrations and macroinvertebrate quality during spring only (R2 = 0.51) and summer only (R2 = 0.52).
Reducing summer point source discharges may be the quickest way to improve ecological river quality, particularly diatom quality in these and similar catchments. Aligning estimates of P sources with ecological impacts and identifying ecological signals which can be attributed to storm P pressures are important next steps for successful management of agricultural catchments at these scales.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty / Department / School: Current - Institute for Agriculture and the Environment
Date Deposited: 16 Oct 2017 05:46
Last Modified: 07 Nov 2017 01:32
Uncontrolled Keywords: Stormflow; Baseflow; Phosphorus; Agriculture; Diatoms; Macroinvertebrates
Fields of Research : 05 Environmental Sciences > 0502 Environmental Science and Management > 050206 Environmental Monitoring
05 Environmental Sciences > 0501 Ecological Applications > 050104 Landscape Ecology
07 Agricultural and Veterinary Sciences > 0701 Agriculture, Land and Farm Management > 070101 Agricultural Land Management
Socio-Economic Objective: D Environment > 96 Environment > 9609 Land and Water Management > 960905 Farmland, Arable Cropland and Permanent Cropland Water Management
D Environment > 96 Environment > 9614 Soils > 961402 Farmland, Arable Cropland and Permanent Cropland Soils
D Environment > 96 Environment > 9606 Environmental and Natural Resource Evaluation > 960608 Rural Water Evaluation (incl. Water Quality)
Identification Number or DOI: 10.1016/j.scitotenv.2017.02.100
URI: http://eprints.usq.edu.au/id/eprint/30880

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