Title: Investigating the effect of changing retention time in natural and artificial water bodies: Simulations using PROTECH-D
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1346, Representation ID: 450, Object ID: 2521
WFD38: Phytoplankton Classification Tool: WP4 Artificial and Heavily Modified Water Bodies (May, 2006) Project funders/partners: SNIFFER and Environment Agency Background to research The Environment Agency and SNIFFER have commissioned this R and D project to examine the potential effect that changes in retention times could have on the phytoplankton communities of a range of water body types. In order to investigate the potential effects of varying retention times, four water bodies were modelled by the phytoplankton community model, PROTECH (Phytoplankton RespOnses To Environmental CHange); two were natural lakes and the others were reservoirs. Objectives of research 1. Gain understanding of the relationship between phytoplankton composition and mean annual biomass and changing retention time. 2. Assess the potential impact a 20% decrease in the inflow would have on the modelled water bodies. Key findings and recommendations All the water bodies tested in this study were sensitive to retention times that were shorter than their original time. The general response in lakes was a decrease in both biomass and cyanobacteria abundance because flushing loss processes began to prevail. The response in the reservoirs was more varied and less consistent. At longer retention times, responses in both total chlorophyll and cyanobacteria abundance were smaller and particularly so beyond a retention time of 100 days for the lakes in this study. This suggests that drought induced effects upon the phytoplankton annual mean biomass are minimal. Annual chlorophyll a, one measure of ecological status in lakes did not alter significantly as a result of any of the changes in retention time except for the extremely short retention times in the lake simulations. Mixed reservoirs were relatively insensitive to changes in retention time because the limiting factor for phytoplankton growth under these conditions was light availability, and flushing loss and nutrient supply were less important. Although many months were sensitive to changes in retention times, it appears that June could possibly be the most sensitive month, particularly at longer retention times. Cyanobacteria dominance was most responsive at this time and under those conditions. When setting MEP and GEP for the phytoplankton biological quality element in reservoirs, the metrics used will be broadly similar to those required to set HES and GES in natural lakes. Key words: Phytoplankton, retention time, PROTECH, inflow i SNIFFER WFD38 effect of changing retention time in natural and artificial water bodies May 2006 TABLE OF CONTENTS EXECUTIVE SUMMARY 1.
Publisher: Environment Agency
Subject Keywords: Phytoplankton; Retention time; Protech; Inflow
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