Aspects of the ecology of a constructed reedbed within herb-rich grassland

Abstract

A horizontal-flow reedbed was constructed in December 1996, at the Central Area Transmission System Terminal, Seal Sands, Teesside (NZ518 247), to provide tertiary treatment for site sewage and surface water. A monitoring programme was required to determine the performance of the reedbed in the treatment of wastewater and its ecological impact within the site. The development of such a biological and chemical monitoring system between October 1996 and July 1997, formed the basis of this project which could be repeated on a long-term basis by Durham University undergraduates. Performance of the reedbed was tested by planting one-half with reeds transplanted from a local natural reedbed, and the other with commercially grown reeds. Wastewater was chemically analysed to show the changes in water quality as it passed through both sections of the reedbed system. Nitrogen and phosphorus inputs to the system were studied in terms of 1) nutrient transformation and 2) their effect on growth and development of the reeds themselves. The ecological impact of the constructed reedbed system upon the surrounding herb- rich grassland was studied using a number of monitoring techniques providing base-line information for future comparison, including pitfall trapping for terrestrial invertebrates, sweep-net sampling for aquatic invertebrates, Longworth trapping of small mammals, and a Common Bird Census. A 5 year management plan has been designed to ensure the efficient treatment performance of the reedbed, and to maintain the conservation value of the site. The research has provided important information on the development of biological processes in a newly constructed reedbed system during the first seven months of operation.