Flow Preferences of Benthic Macroinvertebrates in Three Scottish Rivers

OHare, Matthew Thomas (1999) Flow Preferences of Benthic Macroinvertebrates in Three Scottish Rivers. PhD thesis, University of Glasgow.

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Scottish freshwaters have been described as a national resource of international significance. The high quality of Scotland's lotic systems is integral to the formation of this view. The research presented here aims to provide an insight into the interaction between benthic invertebrates and their hydraulic habitat within some of Scotland's lotic systems. A further aim of this project is that this information presented here will aid the design of river rehabilitation and management schemes thereby helping maintain the integrity of the opening statement. There is a large amount of literature existing which addresses the interactions between benthic invertebrates and flow parameters, substrate type, vegetation, velocity, depth and near bed stresses. However significant gaps remain in our understanding, particularly at the level of individual taxa preferences. Furthermore, little work has been done in Scotland. To address these gap in the data the distribution of macroinvertebrates in relation to flow parameters were assessed for three rivers representative of highland (River Etive), central belt (Blane Water) and borders rivers (Duneaton Water). The importance of deep and shallow reaches as habitat units for benthic invertebrates was analysed and the methods for categorising reaches into riffles, runs and pools assessed. The analysis showed that at the sites examined differences between invertebrate community in deep and shallow reaches were minimal and limited to the preferences of a number of key species. Categorising reaches into riffles, runs and pools on purely visual grounds was insufficient and some measures of velocity and depth are required if the work is to be used for between site comparisons. Benthic invertebrates did show preferences for flow parameters. At the physical scale examined (Surber sample) community structure was influenced in a limited manner by flow parameters; velocity and depth wre the most important. A gradient from erosional to depositional conditions was observed at two of the sites. Limitations of Instream Flow Incremental Methodology (IFIM) as applied to benthic invertebrate habitat identification were identified. Estimates of near bed flow parameters based on point measurements of velocity profiles to samples collected at the scale of Surber samples do not explain any additional variation in the distribution of benthic invertebrates. Analysis of individual flow preferences of macroinvertebrates suggest that to identify flow preference curves, an aim of IFIM, finer scale habitat measurements are needed. Laboratory experiments were carried out to identify the upper velocity tolerances of some benthic invertebrates; Tipulidae and Gammarns pulex. The results show that individuals were flexible in their responses to high velocities. What constituted 'high' velocity was taxa specific Benthic invertebrate community structure was investigated in areas of the Blane Water vegetated with Callitriche instagnalis. Submerged vegetated patches supported a greater abundance of invertebrates than bare substrate. The hydraulic habitat of the macrophyte stands was more diverse than that of bare substrate with higher velocities occurring on the outside of the macrophyte stands than on the bare substrate. Simuliidae dominated the outside of the stands, the area exposed to the highest velocities. The invertebrate community on the outside of the plant stands was less equitable than that found at the root-substrate interface. It is suggested that macrophytes can be used as a tool in the rehabilitation of hydraulic habitat for benthic invertebrates in Scottish rivers. The importance of these results are discussed in the context of river rehabilitation and our ecological understanding of benthic invertebrate community structure.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Kevin Murphy
Keywords: Ecology, Hydrologic sciences
Date of Award: 1999
Depositing User: Enlighten Team
Unique ID: glathesis:1999-75908
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Dec 2019 09:15
Last Modified: 19 Dec 2019 09:15
URI: https://theses.gla.ac.uk/id/eprint/75908

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