Spatial and Temporal Variation of Macroinvertebrate Communities in Forested and Moorland Freshwater Streams in Southern Ireland
| Author | : Kevin O'Gorman |
| Publisher | : |
| Total Pages | : 333 |
| Release | : 1998 |
| Genre | : Stream ecology |
| ISBN | : |
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Patter and processes in macroinvertebrate communities are scale dependent, yet few studies incorporate a series of spatial scales into their research. This thesis focuses on the examination of macroinvertebrate communities at different spatial and temporal scales. Two contrasting catchments, Kilworth and Araglin were studied over a two year period to investigate how different land uses influenced macroinvertebrate communities. Within each catchment, each study stream was examined longitudinally for spatial change and within each site samples were taken seasonally over a two year period to investigate temporal variation. Lower altitudes sites in both catchments were found to be quite similar in water chemistry and in macroinvertebrate community metrics, despite differing land uses. Higher altitude sites at three of the four study streams differed substantially to all other sites in terms of macroinvertebrate community structure, lower pH and lower invertebrate density. The principal factors influencling macroinvertebrate composition were a combination of longitudinal variation, altitude and differences in land use all of which varied along the same gradient. Seasonal differences in macroinvertebrate composition were also found. Macroinvertebrate trophic structure (e.g. functional feeding groups) varied in a predictabel manner longitudinally, largely in accordance with the River Continum Concept. A secondary aim of the study was to examine the effects of disturbance on macroinvertebrate communities. Invertebrate recolonisation was studies at one stream in each catchment following two flood events. Macroinvertebrates recolonised both catchments in a similar manner following flooding at both a community and individual taxa level, although similarity between catchments was strongest at the lower altitude sites. Individual taxa showed a strong preference for particular recolonising strategies (i.e. opportunistic, secondary or late colonisers) irrespective of catchment, longitudinal position or year. The effect of a multiple disturbance on macroinvertebrate communities seen during the 1995 disturbance study where a second flooding event occurred. This reverted the macroinvertebrate communities to their initial disturbed state. Lower altitude sites appeared to be more affected by the multiple disturbance and this may be due to the higher shear stress and the greater unpredicitability of floods at lower altitude sites.
